Thursday, December 10, 2009

2009 Season Summary

The 2009 Atlantic Hurricane Season was below average with eleven depressions forming, nine of which became tropical storms, three of which became hurricanes, and two out of the three became major hurricanes. In total, about $174 million in damages resulted (wealth value for 2009) and fifteen direct fatalities. No hurricanes hit the U.S. this year, and only one made landfall. Although this was a relatively quiet season, there were a few notable storms.
  • Tropical Depression One forming in May made a tropical cyclone form in the Atlantic Ocean in May for three consecutive years
  • No tropical storms formed until August 12, which was the latest start since 1992
  • Hurricane Fred achieved major hurricane status the farthest south and east of any Atlantic cyclone ever recorded
  • Tropical Storm Grace formed the farthest north and east of any tropical cyclone in the Atlantic Basin
  • Hurricane Ida made landfall in the U.S. as a tropical storm in November, becoming one of only six cyclones to do so

Overall, due to an El Nino event, the 2009 Atlantic Hurricane Season was relatively quiet and not much damage resulted.

Thursday, November 26, 2009

Intertropical Convergence Zone

The Intertropical Convergence Zone is an area near the Equator that circumnavigates the globe. Most of it lies between 10ºN and 10ºS. The trade winds, or the winds near the Equator, converge on this zone. Since the winds are rotated in different directions by the Coriolis Effect, no low pressure systems, and therefore no tropical cyclones, can form too near the Equator.

The Intertropical Convergence Zone over the East Pacific. Although no low pressure systems can form in the ITCZ, it is constantly marked by thunderstorm activity.

However, the boundary of the ITCZ, or the ITCZ Axis, is always shifting, and a tropical system can sometimes, but very rarely, from below 5ºN or above 5ºS. A notable example is Typhoon Vamei, which was a Western Pacific cyclone that reached tropical storm strength at a mere 1.5ºN in December of 2001, which is the closest formation to the Equator on record. Also notable is 2004's Cyclone Agni, which formed farther from the Equator than Vamei and moved towards it, eventually reaching the most southerly point of 0.7ºN before turning back northward. Claims on this system are disputed because it was not officially tracked until a few days after the record was set but a fair amount of evidence supports that Agni does indeed hold the record for closest cyclone to the Equator.

Cyclone Agni at record latitude, a mere 45 miles from the Equator.

Although the winds over the ITCZ hinder tropical cyclones from forming within the region, they do provide an important factor for tropical cyclone development: tropical waves. A vast majority of tropical cyclones form from tropical waves, which are areas of convection that typically move west over the ITCZ. After the wave moves northward, it then can develop a low pressure system, and eventually become a tropical system. Therefore, the ITCZ is an important factor in tropical cyclone development, even if tropical cyclones can't form in the area itself.

A map of the formation and progression of tropical waves before becoming tropical cyclones.

Sunday, November 8, 2009

Hurricane Ida (2009)

Storm Active: November 4-10

On November 2, a low pressure system formed from a tropical wave along the Intertropical Convergence Zone. The low was situated in the extreme southwestern Caribbean, off the coast of Nicaragua. The low was nearly stationary for the next two days and it began to gather cloud cover and tropical characteristics. On November 4, Tropical Depression Eleven formed with 35 mph winds and a pressure of 1006 millibars. Later that afternoon, the winds near the center of circulation jumped to 60 mph and the system was named Tropical Storm Ida. Then, as it moved northwest, Ida reached a minimal hurricane strength of 75 mph winds and a 987 millibar pressure before making landfall in Nicaragua in the morning of November 5. As it encountered the mountainous terrain of the region, Ida promptly lost hurricane status, and it steadily weakened, becoming a tropical depression by late on November 5. During the morning of November 6, Ida crossed into Honduras, still maintaining tropical depression strength. Finally, later on November 6, Ida reemerged into the northwest Caribbean Sea. Ida regained tropical storm strength on November 7. During the day, the deep moisture and warm water of the region fed Ida, and it rapidly strengthened once again. By the evening of November 7, Ida was approaching hurricane strength, and was continuing north, towards the Gulf of Mexico. Ida then became a Category 2 hurricane with 100 mph winds and a pressure of 976 millibars. It brushed past the Yucatan Peninsula, causing tropical storm force winds and rain, but a majority of the wind was on the east side of the system due to a strong ridge of high pressure over the Bahamas. The pressure difference caused sustained winds of over 30 mph to rip through the Florida Keys and the surrounding region, despite the fact that the circulation was still fairly far away. In addition, rain from Ida extended farther to the southeast, reaching the Cayman Islands and beyond. Later on November 8, Ida reached its peak intensity of 105 mph winds and a pressure of 976 millibars. Then as Ida entered the northern Gulf of Mexico, it encountered cooler water, and weakened once again. By the afternoon of November 9, Ida had become a tropical storm once again, and was already battering the coasts of Alabama, Louisiana and the Florida Panhandle with high surf and tropical storm force winds and rain. Overnight, Ida weakened further and began its extratropical transition. By the morning of November 10, the center of Ida was sill offshore, but all convection associated with the system had moved to the north over much of the southeast U.S., producing rain and thunderstorms, including up to six inches of rain locally in parts of Florida. As Ida made landfall in Alabama, it promptly weakened to a tropical depression and became extratropical. It then combined with a westward moving cold front and another low pressure system approaching North Carolina from the east to bring a huge rain and wind event to the entire U.S. east coast. In addition, a very strong high pressure system was situated over Maine (it was a powerful one, with a pressure exceeding 1035 millibars) causing east-to-west wind to bring surf and tropical storm force gusts to much of the coast. The high pressure also blocked the system, and it moved very slowly. Rain and wind continued for the next three days and some areas accumulated over 10 inches of rain. By November 13, the low pressure system had moved up to the coast of New Jersey and was finally weakening. The system sped off to the northeast and left the U.S. on November 14. Ida was a notable storm in El Salvador because it contributed to a mudslide that killed 124 people, but Ida also became a powerful and dangerous nor'easter after becoming extratropical, killing an additional 10 people. Ida also caused $2.15 million in damage.

Ida strengthening as it enters the Gulf of Mexico.

Track of Ida.

Wednesday, October 7, 2009

Tropical Storm Henri (2009)

Storm Active: October 6-8

Near the end of September, a tropical wave emerged off the coast of Africa and moved westward. By October 1, the system already was associated with a large area of showers and thunderstorms. The deep tropical moisture enriched the system and contributed to its organization, but it did not develop a well-defined center. The wave moved northwest, out of favorable conditions, but convection persisted. Then, on October 6, a rapid intensification occurred, and the system was declared Tropical Storm Henri. Henri's convection was displaced to the east of the center by El Nino-related west to east sheer, much like Danny and Erika before it. Despite these adverse conditions, Henri gained strength, reaching its peak intensity of 50 mph winds and a pressure of 1005 millibars. Henri paralleled the northern islands of the Caribbean Sea to their north, causing raised surf. Henri weakened later on October 7, and, overnight, became a tropical depression. By the early evening of October 8, Henri had disintegrated into almost nothing on satellite imagery, and it decayed into a remnant low. The low quickly dissipated on October 9. No significant effects resulted from this system.

Henri at peak intensity north of the Caribbean Sea.

Track of Henri.

Tuesday, October 6, 2009

Tropical Storm Grace (2009)

Storm Active: October 4-5

On October 1, the center of a non-tropical low over the Azores developed a small area of showers. However, the showers didn't persist and no tropical cyclone formed. The low moved slowly northeast, hindered by a stationary front to its north into October 4. Then, an area of convection flared up rapidly within the low that evening, resulting in it being classified as Tropical Storm Grace. It formed at 41.2 N and 20.3 W, making it the farthest northeast a tropical cyclone has ever formed on record, Since the low was already fairly strong (995 millibars before Grace's formation) Grace already had reached a strong tropical storm intensity of 65 mph winds and a pressure of 990 millibars. Grace's movement quickened to 25 mph, as it went speeding off to the northeast. Despite being in a hostile area for tropical cyclone development, Grace strengthened into the morning of October 5, reaching its peak intensity of 70 mph winds and a pressure of 989 millibars. At its peak intensity, Grace was a very small system, less than 100 miles across. In comparison, the widely scattered shower activity of the extratropical low spanned hundreds or even a thousand miles. Throughout the day of October 5, Grace continued northeast, reaching a forward speed of 30 mph, and began to weaken. It was then absorbed by a frontal boundary late on October 5. The combined system caused scattered showers over the British Isles over the next day but no damage resulted.

Grace at its peak of a small, intense tropical storm in the extreme northeast Atlantic.

Grace's track.

Sunday, September 27, 2009

Tropical Depression Eight (2009)

Storm Active: September 25-26

A tropical wave moved off of Africa on August 23, and began to develop disorganized showers and thunderstorms as it moved to the west-north-west at about 15 mph. On September 24, the Cape Verde Islands received scattered showers and thunderstorms as it passed to the south of the region. On September 25, the wave began to organize west of the Cape Verde Islands, despite being in an area only marginally favorable for tropical cyclone formation and started to develop a center of circulation. The system was declared Tropical Depression Eight at 5 p.m. on September 25 already at its peak intensity of 35 mph winds and a pressure of 1008 millibars. Over the next day, the depression moved northwest into cooler waters and became less organized. Then, exactly a day after formation, Eight lost its center of circulation and dissipated. The tropical wave continued to produce shower activity as it moved northwest and was monitored for regeneration, but no new low formed, and the possibility for reformation was gone by September 27.

The tropical wave destined to become Tropical Depression Eight organizing in the East Atlantic.

Track of Eight

Saturday, September 12, 2009

Hurricane Fred (2009)

Storm Active: September 7-12

On September 6, a strong, organized, tropical wave associated with an area of low pressure moved off of Africa and quickly developed into Tropical Depression Seven the next day. The depression passed south of the Cape Verde Islands and intensified into Tropical Storm Fred on September 7. Fred's center became well-defined, and the system strengthened through the next day, becoming Hurricane Fred on September 8 with 75 mph winds and a pressure of 987 millibars. Hurricane Fred jumped to Category 3 intensity in just 12 hours and reached its peak intensity of 120 mph winds and a pressure of 958 millibars on September 9. At his time, Fred had a distinct eye feature, and it became the most southeasterly major hurricane ever to form in the Atlantic Ocean. Fred curved to the north, due to a ridge to its west, and its southeast side weakened. As a result, strong wind sheer ripped at the system from that direction, causing Fred to weaken, becoming a tropical storm on September 11. Convection began to separate from the center to the north, and Fred became nearly stationary, drifting east, then south, and weakening all the time and making a tight loop in the Eastern Atlantic. By mid-afternoon on September 12, Fred was a minimal tropical storm, with almost no convection. It was then downgraded to a remnant low that night, and moved west. The low continued to produce shower activity, but dissipated on September 16. However, a new low formed in association with Fred's remnants 500 miles south of Bermuda and the area was monitored once again. The low continued to drift west, and finally dissipated, becoming part of a frontal boundary, on September 20.

Hurricane Fred at Category 3 intensity in the far east Atlantic.

Track of Fred. Note that the triangles signifying Fred's remnant low continued much farther west before dissipating.

Wednesday, September 2, 2009

Tropical Storm Erika (2009)

Storm Active: September 1-3

On August 26, a tropical wave moving off of Africa became associated with a broad area of low pressure south of the Cape Verde Islands, producing shower and thunderstorm activity. However, the cloud cover and organization diminished over the next few days as the system moved west. By August 31, though, the low had regenerated into an organized ball of convection. The system was organized enough to be a tropical storm and had tropical storm force winds, but i still wasn't classified. This was because it lacked a center of circulation. The low was an elongated oval, widest north to south, and a center could have formed anywhere along the oval. During the afternoon of September 1, a center began to for, evident on visible imagery as a point just east of the cloud cover associated with with the system. Therefore, like the previous storm Danny, the system skipped tropical depression status and was upgraded directly to Tropical Storm Erika, with 50 mph winds and a pressure of 1007 millibars. Later that night, the pressure dropped to 1004 millibars and the winds increased to 60 mph, but Erika took a southerly turn and weakened the next morning. By mid-morning, Erika began to interact with the northern Leeward islands of the Caribbean Sea, causing wind and rain. Later on September 2, Erika entered the Caribbean, still maintaining minimal tropical storm winds of 40 mph. Erika struggled westward, its center well west of the convection, similar to Tropical Storm Danny's appearance several days earlier. Erika meandered through the Caribbean for another day, before weakening to a tropical depression south of Puerto Rico on September 3. Overnight, Erika weakened into a remnant low. The next day, the low dissipated. Damage was minimal and no fatalities resulted from Erika.

Erika near peak intensity. Even then, Erika was very disorganized.

Track of Erika.

Sunday, August 30, 2009

Tropical Storm Danny (2009)

Storm Active: August 26-29

On August 20, a tropical wave moved off Africa. It showed little signs of organization, but it was monitored for development. The cloud cover diminished on August 22, but flared up again on August 23, as the wave interacted with an upper-level low to its northwest. The low, sheered the system, but it also fueled increasing convection around the wave over the next two days. As the tropical wave passed under the low on August 25, sheer lessened, and more organization was evident. The wave ad strong enough winds to be considered a tropical storm, but still lacked a specific center of circulation. However, this appeared on the morning of August 26, and the wave-low interaction was upgraded directly to Tropical Storm Danny. Danny had most cloud activity to the northeast of the center, and wasn't that organized. Despite this, stronger winds were found in the system and Danny strengthened, reaching its peak intensity of 60 mph winds and a pressure of 1006 millibars that night. Danny was heading generally northwest, but meandered north of the Bahamas, sometimes going west, north, even south. As Danny slowly made its way towards the U.S. east coast on August 27, it encountered less favorable conditions and began to weaken as its convection became increasingly displaced to the east of its center. By August 28, Danny was a minimal tropical storm, and was steered more northerly by a ridge of high pressure of the southeastern United States. Early on August 29, Danny was downgraded to a tropical depression off the Outer Banks of North Carolina. The last advisory was issued at 5 a.m. Eastern Standard Time that morning as Danny merged with a frontal low pressure system in the Northeast. Danny helped to enhance the moisture in the region even more, causing 2-4 inches of rain over various areas of New England. The merged low and accompanying frontal boundary continued northeast, eventually causing heavy rain in the Canadian Maritime on August 30. Danny, having never made landfall as a tropical system, caused little damage, and one fatality resulted from rip currents on the coast of North Carolina.

Visible satellite image of Danny while maintaining its peak. The center is highly evident as a swirl of clouds well outside the cloud cover, which is all east of the center.

Track of Danny.

Tropical Storm Claudette (2009)

Storm Active: August 16-17

On August 11, a scattered area of showers and thunderstorms became associated with a tropical wave over the Bahamas. The wave showed little to no organization over the next few days as it moved westward, and tracked south of Florida. On August 15, upon entering the Gulf of Mexico, the wave became significantly better organized, and on August 16, was classified Tropical Depression Four, with 35 mph winds and a central pressure of 1011 millibars. Later that same day, Tropical Depression Four became Tropical Storm Claudette. The system quickly reached its peak intensity of 50 mph winds that evening. Overnight, technically very early on August 17, Eastern Standard Time, Claudette made landfall in the panhandle of Florida. The system's central pressure briefly decreased after landfall, but then Claudette became a remnant low late on August 17. For a few more hours, the remnants of Claudette continued northwest, before it dissipated on August 18. Two fatalities occurred as a result of this system, and damages totaled around $1.2 million.

Claudette near peak intensity in the Gulf of Mexico.

Track of Claudette.

Tuesday, August 18, 2009

Hurrricane Bill (2009)

Storm Active; August 15-24

On August 11, a strong tropical wave moved off Africa. It took a few days to organize, but on August 15, it became Tropical Depression Three, with 35 mph winds and a pressure of 1006 millibars. A few hours later, Three became Tropical Storm Bill. Unlike the previous storm Ana, Bill quickly stregthened and became the first hurricane of the 2009 season on August 17 with 75 mph winds and a pressure of 987 millibars. It took a west-north-west track, which allowed for more favorable conditions. Inside the well-organized circulation, eyewall and eye structures quickly formed. A large area of high pressure kept Bill on this track, as it continued to gain strength. By August 18, it was a Category 2, with 100 mph winds and a pressure of 967 millibars. Then, overnight, Bill rapidly intensified into a Category 4 hurricane, with winds of 135 mph and a pressure of 948 millibars. Later that same day, Bill made its closest approach to the northeasternmost islands of the Caribbean, causing high surf but no other effects. On August 20, the ridge of high pressure keeping Bill to the south weakened, allowing Bill to take a northward turn. Bill slowly weakened, and on August 21, began to batter Bermuda with tropical storm force winds as a Category 2. Bill continued north, accelerating over time, and brushed Cape Cod with its outer bands causing huge surf and rip currents. On August 23, Bill's center paralleled the coast of Nova Scotia, staying barely offshore. At this time, Bill was turning east and was a minimal Category 1 hurricane. Late that night Bill made a landfall in Newfoundland and had passed by a mere six hours later. Early on August 24, Bill was a tropical storm, and, going east at 43 mph, Bill finally became extratropical. It continued eastward, and its extratropical remnants eventually brought wind and rain to Great Britain and surrounding areas. Bill caused two fatalities, both as a result of high surf on the east coast of the U.S.

Sorry, but an image of Hurricane Bill is not currently available on this website. To see one, click here.

Track of Bill.

Tuesday, August 11, 2009

Tropical Storm Ana (2009)

Storm Active: August 11-17

On August 8, a strong tropical wave emerged off Africa. It showed a lot of organization, and therefore was classified a tropical depression on August 11. Tropical Depression Two had 30 mph winds and an internal pressure of 1006 millibars on its first advisory, but it showed signs of strengthening. It also had minor effects on the southern Cape Verde Islands. Tropical Depression Two became more organized on August 12, when convection became more defined and covered the center of circulation. However, the system was still a tropical depression with 35 mph winds and a pressure of 1006 millibars. That night, however, the depression lost its cloud cover due to wind sheer, and weakened back to 30 mph winds on August 13. Despite some regeneration of the convection later that day, it was downgraded to a remnant low. However, cloud cover came back to the system slowly and on August 15, it became Tropical Depression Two once again. Then, six hours later, it became the first named storm of the 2009 season with its peak intensity of 40 mph winds and a pressure 1005 millibars. The newly named Tropical Storm Ana continued westward and interacted with the easternmost islands of the Caribbean, causing little damage. Only rain and some tropical storm force winds resulted. As it plowed deeply into wind sheer, the system weakened and became Tropical Depression Ana south of Puerto Rico. It brought periods of showers and winds to the island, before becoming a remnant low on August 17. The low continued west-north-west over the next few days, and dissipated near Florida on August 19. Damage from Ana was minimal and no fatalities resulted from this system.

Tropical Depression Two before dissipating and regenerating into Tropical Storm Ana.

Track of Ana.

Monday, July 27, 2009

Lack of Hurricane Activity in the Atlantic Basin in 2009

In the first two months of the hurricane season, i.e. up to the end of July, typically only one tropical cyclone has occurred in the north Atlantic Basin, but in the last decade, an average of three named storms have already occurred by this point. Also in the last decade, there has been about a fifty percent chance of a hurricane forming before July 31.

Tropical Depression One has been the only storm of the season, and it formed before the season started, in May, making it a preseason storm. Since then, hardly any activity has occurred and no cyclones have formed. The very opposite of this has happened in the East Pacific Basin, where, after a late start, five tropical cyclones, four of them named, and two of them hurricanes formed before July 31.

Some potential for tropical cyclone formation was present in June, and a fair amount of tropical waves came and dissipated during that time. However, an El Nino event (see here) that had been building for months reached strength in early July, stopping anything from forming. The current prediction is for a near average hurricane season with 11 named storms. However, the current trend may end in a below average season, the first since 2006, and before that, 1997. Both of these seasons' source of inactivity was an El Nino as well.

Despite this, there are exceptions. In 2004, no storms formed until August 1, which is a very late start. However, the 2004 season went on to have 15 named storms, with 9 hurricanes and 6 major hurricanes, along with over 3,100 fatalities, making it one of the most damaging seasons ever.

Hurricane activity is very unpredictable, and a lot may happen between the end of July, and the end of November which marks the end of the hurricane season.

Sources: National Hurricane Center, and wikipedia (which got its information from the National Hurricane Center)

Tuesday, June 23, 2009

El Nino and La Nina

El Nino and La Nina are two phenomena that concern pressure differences over the Pacific Ocean and have effects all over the world, most specifically on North and South America. El Nino and La Nina conditions are defined by the pressure of the air above the northeastern Pacific Ocean. During an El Nino, a low pressure system is situated over this region, and during a La Nina, a high pressure is situated over this region. Although low and high pressure systems come and go, some areas of the world generally have a low pressure or high pressure over them. One example of this is the Bermuda high, which is a high pressure over the Bermuda area during the summer months. When this high pressure is weaker, it allows tropical cyclones to curve off the east coast of the United States and not impact land, but when it is strong, it acts as a barrier, and tropical cyclones are pushed into making landfall along the Atlantic coast.

An example of a weak Bermuda high. Tropical cyclones are able to curve eastward without affecting land

An example of a strong Bermuda high. Tropical cyclones are pushed into the U.S. This condition was present during the 2004 and 2005 seasons, and these were some of the worst and most active in history.

Minor El Nino and La Nina conditions are common and usually only last a few months. But a long term event, or episode, occurs every five to seven years. An El Nino has the effect of letting a stronger Jet Stream enter the United States, which causes wet weather in the Midwest and South, and cool weather in the north. During a La Nina, the high pressure system in the Pacific severely weakens the Jet Stream and prevents moisture from reaching the Midwest and South. Therefore, there is dry weather in this region. El Nino and La Nina conditions also affect tropical cyclone formation. The strong Jet Stream during an El Nino causes a strong west to east wind along the tropics, causing intense wind shear (for the effects of a strong Jet Stream, see The Dagger of Death) which rips tropical cyclones apart. During a La Nina event, the lack of wind shear allows more tropical cyclones to form. A recent example of tropical cyclone formation hindered by an El Nino was 2006, when only 10 storms formed. Also, due to the effect of the Jet Stream on the Bermuda High, the only strong hurricanes of this season didn't affect land.

The effects of El Nino and La Nina.

El Nino and La Nina also affect water temperature, and therefore fish migrations. The fish migrations, in turn, affect the fishing business and therefore the economy. Although the results of El Nino and La Nina seem minor, they start many chains of events that change things in many different topics in many different parts of the world.

Sources: (images), wikipedia (some information and image)

Thursday, May 28, 2009

Tropical Depression One (2009)

Storm Active: May 28-29

A low pressure system formed on May 27 off the coast of North Carolina. Drifting northeast, the low showed no signs of development until, on May 28, it rapidly strengthened into Tropical Depression One with 35 mph winds and a pressure of 1007 millibars. The convection associated with the system was tight, and therefore didn't affect any landmass. The depression continued east-north-east into May 29, when, at its peak intensity of 35 mph winds and a pressure of 1006 millibars, the circulation began to separate from the clouds associated with it. Soon after it became extratropical and was absorbed by a frontal boundary. Tropical Depression One was a preseason storm, and therefore the 2009 season is the third consecutive season with a storm forming before June 1. No land was affected by this system.

Tropical Depression One in the Northwest Atlantic.

Track of One.

Saturday, May 16, 2009

Hurricane Names List-2009

For the Atlantic Basin in 2009, the names list is as follows

Ana (used)
Bill (used)
Claudette (used)
Denny (used)
Erika (used)
Fred (used)
Grace (used)
Henri (used)
Ida (used)

The names Fred, Ida, and Joaquin replaced the names Fabian, Isabel, and Juan which were retired in the 2003 season.

Monday, May 4, 2009

Heat and Its Relation to the Early Universe

Heat is what we depend on for life, warmth, and the existence of galaxies, stars, and planets. However, heat had another meaning in the very early Universe. Heat equaled movement and instability and the huge amount of heat caused particles to move around and annihilate each other causing chaos and confusion. Much of these hyperactive particles' movement happened in the first second of the Universe, creating what we know today. To encompass all temperatures, the Kelvin scale is used. Beginning at room temperature, or 293 K, we begin our journey into extreme heat, and the fascinating phenomena that occur there.

At 310 K, or 98.4 F, is the average temperature of the human body, closely followed by the boiling point of water, at 373.15 K. Note that all main states of matter of water occur naturally: solid, liquid and gas. However, the gas form, water vapor, can be attained in average temperatures by the Sun's heat and the movement of particles. At 1900 K, we reach the temperature of the nose of the Space Shuttle, during re-entry. The supercharged ionosphere (filled with ionized gas, hence the name) is a factor, along with friction, that heats the spacecraft to this temperature. As you get higher, metals start to boil, such as lead, which boils into a gas at 2022 K, or about 4000 degrees Fahrenheit.

At 3000 K, we reach our first important milestone on the backwards journey towards the Big Bang on the scale of extreme heat. The Universe had settled down to this still extreme temperature about 380,000 years after the Big Bang. It is at this time that the Cosmic Background Radiation was emitted* (see footnote below this paragraph). In fact, this is the first time that the Universe was transparent. The Cosmic Background Radiation wasn't emitted until this time, because electrons and anti-electrons (the electron's antimatter pair) were still annihilating each other and turning into photons. In the case of antimatter, there were approximately one million antiparticles for every one million and one regular particles. On contact the pairs destroyed each other and became photons. And the next second, the photons would transmit their energy into mass, and immediately create another electron and another anti-electron. This process stopped when the temperature dropped below 3000 K because the photons lost energy as the Universe expanded, and eventually, they didn't have enough energy to become electrons anymore. Gamma rays are the only waves that have enough energy to produce such particles. Overall, after this time, the net result was one particle left for every one million original particle pairs, (note that this slight amount of matter left in the Universe became everything we know today: galaxies, planets and stars) and a whole bunch of photons. These photons have been causing the Cosmic Background Radiation ever since, for the past 13.7 billion years. This also is the first time in the Universe that complete atoms existed.

*Note that I could call it the Cosmic Microwave Background Radiation as it is called today, but I will refrain from doing so due to the fact that the radiation originated as gamma and X-rays and over time, the wave lost energy and became a microwave. The different waves are distinguished by their frequency, or the distance between "crests" in the curvy line that is the wave. The frequency of the CBR (this of course being the acronym for Cosmic Background Radiation) drops as the Universe expands, and thus if the Universe continues to expand the frequency will get longer and longer, until all Cosmic Background Radiation will become radio waves.

Suddenly, we jump to 13,000,000 K, the temperature required for the proton-proton cycle and the fusion of Hydrogen nuclei into Helium nuclei. (see the post Burning Hydrogen) This is also the temperature of the Sun's core, and the temperature in the Universe about 20 minutes after its formation. This temperature in the early Universe formed the first atomic nuclei heavier than H1. (the Hydrogen nucleus consisting of one proton) The process in which the first Helium, Lithium, and Deuterium atoms were formed in this time period was called Big Bang Nucleosythesis. Big Bang Nucleosythesis lasted approximately from 3-20 minutes after the Big Bang. At this time, hyperactive electrons were still at the point where they couldn't settle down into completed atoms, and real atoms (electrons and all) weren't formed until a while after. This is because of the ongoing electron-photon reactions, see above.

The proton-proton cycle of fusion in the Sun.  Notice how neutrinos (marked v) and the positrons (anti-electrons represented by white dots) are emitted during the reaction. Also, the gamma rays are the heat and energy released from the reaction, and absorbed by the Earth. The process begins with four Hydrogen nuclei and ends with one Helium nucleus.

At 10 billion K, atomic nuclei break down and proton and anti-proton reactions occur. This temperature occurred naturally in the Universe at about one second after the Big Bang. This milestone in temperature marked the end of the hadron epoch, which lasted from one millionth of a second to one second after the Big Bang. As with electron and anti-electrons, protons and anti-protons annihilate each other on contact, forming photons. Also, since a byproduct of this reaction is the production of the tiny neutrino (a small particle possessing nearly no mass), a wave of neutrinos was released at the end of the epoch, forming the less known brother of the Cosmic Background Radiation, the Cosmic Neutrino Radiation. Since the neutrinos move at close to the speed of light, and the speed of them is known, they would probably be an even more accurate Universe clock-if they could be detected. Unlike other particles, neutrinos are so minuscule that they pass directly through ordinary matter, and barely ever make contact with other particles, such as protons. In fact, the Sun emits so many of these tiny particles that in the time that it takes to say "neutrino", 50 trillion of these particles pass through you!

At about 1,000,000,000,000 or one trillion K, the heat breaks down the hadrons themselves into the even tinier particles inside them, the quarks. The Universe dropped below this temperature at one millionth of a second after the Big Bang, at before this, from one trillionth to one millionth of a second after the creation of the Universe, was the Quark Epoch. During this epoch, the entire Universe was a sea of quarks and gluons. The gluon is the (somewhat hypothetical) particle that binds quarks together into hadrons. The substance of the Universe during this time was quark-gluon plasma, (for more info on plasma, see here) or a sea of ionized quarks mixed with gluons. Before this point however, the four forces of the Universe: gravity (the force that pulls heavy objects together), electromagnetism (the connections and effects of electricity and magnetism), the weak nuclear force (the force that causes radioactive decay) and the strong nuclear force (the force that binds protons and neutrons together in the nucleus, and, at a smaller scale, also binds together quarks within particles such as protons and neutrons) start to break down and the physics we know today start to change even at fundamental levels.

A representation of the internal structure of a proton. The quarks labeled "u" are up quarks and each have a charge of 2/3. The quark labeled "d" is a down quark and has a charge of -1/3. The wavy lines represented the strong nuclear force, carried by the gluon. Notice that the charges of the quarks, 2/3+2/3-1/3=1 add to form a charge of +1, which is the charge of a proton.

At one trillionth of a second after the Big Bang, the forces begin to unify. The first two forces to unify are the electromagnetic force and the weak nuclear force, forming what is called the electroweak force. This state only can occur at a temperature at about 1,000,000,000,000,000 K, or one million billion Kelvin. To unify these forces in theory, one must come up with a set of physical and mathematical laws that cover both forces. This has already been done for the electroweak force. The strongly hypothetical particles that carry these forces have been explained and unified, but beyond this, it gets even trickier.

At higher than 1,000,000,000,000,000,000,000,000,000 K, or one million billion trillion K, the next unification occurs, this time between the electroweak force and the strong nuclear force to form what is known as the electronuclear force. The theory connecting all three of these forces is called the Grand Unification Theory. This unites nearly all of quantum physics. This force only existed during the Grand Unification Epoch (aptly named) from 10^-43 seconds to 10^-36 seconds after the Big Bang. The electroweak and the strong nuclear force have been unified in theory, but there is still some disagreement about the force's exact nature.

Finally, we reach the hottest, densest, shortest epoch of this Universe, in which the remaining fundamentals of physics break down. This epoch is named the Planck epoch, named after Max Planck. Max Planck discovered the smallest units of length and time as well as others, and discovered the maximum possible temperature and density, as well as others. I go into detail about the Planck units in the post, The Planck Constant and Its Applications. The Universe up to 10^-43 seconds is the time when it was younger than the Planck time, a possibility not nearly explained by any modern theory. It is theorized that the electronuclear force now combines with gravity, at a soaring 14,000,000,000,000,000,000,000,000,000,000,000 K, or the Planck temperature. The theory that covers this is called (very appropriately) the Theory of Everything. This theory would unify gravitation and quantum physics into a theory that explains all phenomena that have and will occur in our Universe. The String Theory and Quantum Loop Gravity Theory have both attempted to explain this, but appear to have failed in encompassing everything. Hopefully, in the future, theories will shed light on this unknown epoch.

Therefore, extreme heat starts by boiling metal, and then breaking down particles, and finally by unifying all that there is in the Universe.

Monday, April 13, 2009

Cold and Special States of Matter

Although the journey to extreme heat spans many trillion trillion trillions of Kelvin, the journey to extreme cold only goes down a few hundred Kelvin to 0 K, or absolute zero, about -273.15 Celsius and -459.67 Fahrenheit. I will use the Kelvin scale, as it is the most convenient for representing low temperatures (to convert Celsius to Kelvin, simply add 273.15). As we go down in temperature, the movement of particles slows, eventually freezing gases, and creating substances that defy gravity and nearly stop light beams.

The calculation of absolute zero came about in a fairly simple way. Two temperatures were found, and the movement of particles was measured for each temperature. This was done using the boiling and freezing points of water. By plotting these two points on a graph, and then continuing the line until it reached the temperature where there was no movement at all, a very accurate approximation of absolute zero could be found. This, of course, is assuming the function of temperature to particle movement was linear, or a straight line. If it wasn't, more points would be calculated before the zero point could be found.

We will start at room temperature, which is about 293 Kelvin, traveling down on the temperature scale. On this journey, we soon encounter the melting point of the element Mercury, which is a liquid at room temperature. Mercury freezes into a solid at 234 K. As we get lower, we encounter the well known dry ice. Dry ice is frozen carbon dioxide and does not have a "melting point" because on contact with warm air, carbon dioxide sublimes (going directly from solid to gas, without any liquid middle stage). The gas resulting from subliming carbon dioxide is fog. In fact, the liquid form of carbon dioxide cannot occur unless under pressure. Therefore, the "subliming point" of carbon dioxide is 194.65 K.

As the temperatures continue to drop, the gases begin to liquefy. One example is oxygen, which at 90.20 K, becomes a blue liquid. One property of this liquid is its ability to make objects dipped in it very brittle. The classic example of this is dipping a bouncy ball into liquid oxygen and dropping it. The brittle properties of the ball causes it to shatter. Oxygen is supposedly one of the permanent gases, (the term was coined by Michael Faraday) or a gas that cannot be liquefied by pressure alone. These gases are oxygen, nitrogen, and Hydrogen (Helium would be a permanent gas but it wasn't discovered until later).

The second of the so called permanent gases to liquefy is nitrogen at 77 K. Nitrogen then solidifies at 63 K. The next gas is Hydrogen, which liquefies at a very low 20.28 Kelvin. This was the coldest liquefaction point of any gas before Helium was discovered. Hydrogen also becomes a solid at 14.2 K. Finally, the last gas to liquefy is Helium, at an astounding 4.22 Kelvin. Helium solidifies at an even lower temperature, and the solid from of Helium usually requires pressure to keep it stable.

Now, that all the gases are liquefied, various strange phenomena occur, the first of which is superconductivity. Many metals conduct electricity, but it has been discovered that at very low temperatures, metals suddenly have zero resistance to electrical current. Therefore, magnets have the effect of floating on the metal's magnetic field. Until 1986, all metals known had a superconductivity point of less than 30 K. Over recent years, however, metals have been discovered with higher superconductivity points. The first metal to have a point higher than 30 K was LaBaCuO (La=Lanthanum, Ba=Barium, Cu=Copper, O=Oxygen) at 35 K. The next discovery was the metal whose acronym is YBCO, which had a point of 90 K, discovered in 1987. Progress continued over the years, until today, when the highest temperature superconductor is thallium barium calcium copper oxide (Hg (12 atoms) Tl (3 atoms) Ba (30 atoms) Ca (30 atoms) Cu (45 atoms) O (125 atoms)). This remarkable substance has a superconductivity point of 138 K, and possibly up to 164 K under more extreme pressures. If more high temperature superconductors could be discovered, there would be a definite commercial use for superconductivity and electric wires could conduct electricity without any resistance, increasing the efficiency of transporting electricity over long distances. Currently, it is not known why metals reach this curious state at low temperatures or why the temperatures would vary from metal to metal.

A magnet levitating on the magnetic field produced by a superconductor. The superconductor itself is not visible but the wisps of gas are a result of the liquid nitrogen (the coolant to the superconductor) evaporating.

Another strange property of matter at extremely cold temperatures comes about when we reach 2.1768 K. Helium* (see footnote directly below this paragraph) at this point is a liquid, and it is a normal colorless liquid from 4.2 K down to 2.1768 K. Then, a strange thing happens. The liquid switches phases and turns blue. Also, its viscosity becomes zero. The viscosity of a liquid is, in common terms, the "thickness" of the liquid. For example, maple syrup, as you know, takes awhile to flow and clearly has high viscosity compared to water, which is "thin" and flows easily and quickly over a surface. However, even water encounters resistance and barriers, such as rocks or dams, can (temporarily) stop it. However, when a liquid has exactly zero viscosity, it is called a superfluid. The normal Helium 4 atom (which has two electrons, two protons, and two neutrons) becomes a superfluid at its "lambda point" or 2.1768 K, as mentioned above. The amazing properties of superfluid Helium allow it to, without friction, travel up surfaces and defy gravity. For example, if a empty container, devoid of superfluid Helium, was submerged into an area filled with the fluid, a thin film of Helium would travel up the walls of the container and fill it until the level equalizes. In fact, unless sealed, superfluid Helium would flow everywhere until it was heated above its Lambda point or until there was a film of superfluid Helium around the entire Earth! Also, below Helium's freezing point (not exactly calculated, but is probably 1.5 K for pressurized Helium and 0.95 K for regular Helium) Helium is conjectured to become a supersolid. A supersolid is identical to a superfluid, with the exception that a supersolid has solid-like properties that result in an orderly spacing of molecules. Therefore, the solid would be "flowing". Since superfluids move without friction, a superfluid fountain is a perpetual motion device. The fountain continues without any energy at all! The only problem is that superfluids exist at such low temperatures that there is no commercial use.

*The only substance that is capable of being a superfluid is Helium. This is because Helium is the only substance that is a liquid at this extremely low temperature. (Hydrogen freezes at 14.2 K)

A picture showing how superfluids can travel, as a thin film, up the walls of a container. Eventually, the levels will equalize. Also, notice that a thin film circumnavigates the entire structure. If the top was not sealed, the superfluid would creep out and escape.

In 1924, Satyendra Bose sent a paper to Albert Einstein on theories of matter at extremely low temperatures. Einstein applied his own calculations and together they discovered a peculiar property of matter at very low temperature called the Bose-Einstein condensate. The quantum properties of this state of matter are very technical, but it seems that the atoms themselves adopt wave-like properties and grow larger. As the temperature continues to drop, the waves become larger and larger, until they intersect with each other and become one single unit, moving (although very little because the temperature is so low) uniformly. The quantum physics of atoms and particles applies to the larger "atom" and allows events to be seen visibly that usually only occur on very small scales. However, nothing was physically learned about this state of matter until over seventy years later, in 1995, because the temperature needed to attain it was very low (below 0.000001 Kelvin). Before its discovery, it was thought that light atoms would be more useful in producing Bose-Einstein condensates, but the first sample synthesized was of a small sample of Rubidium at 170 nanokelvin (0.000000170 K). Later, another Bose-Einstein condensate was produced, this time with Sodium atoms. This condensate had about one hundred times more atoms, or about two hundred thousand atoms, and the results were very beneficial for seeing how Bose-Einstein condensates interact with each other. Also, the Bose-Einstein condensate has the interesting property of being able to slow down light to observable speeds. The Bose-Einstein condesate is also very fragile, and interaction with even one regular atom could turn the substance back into normal form.

A map of atomic velocities during the production of a Bose-Einstein Condensate. The colors represent how many atoms are moving at a certain velocity. For example, the color red represents that very few atoms are moving at the same velocity while the color white represented thousands of atoms moving at the same rate. The image on the left is just before formation of the condensate, and the atoms are moving to different directions at different speeds. The center and left images are progressions in the life of the Bose-Einstein condensate where the atoms are moving in unison, represented by the white peak.

The temperature at which a Bose-Einstein Condensation is achieved is still above the lowest attained temperature of 0.0000000001 Kelvin, and this is still above absolute zero. The colder you get, the harder the last bit of heat clings to the matter. What happens at absolute zero, and whether it is even attainable, is unknown and may never be known.


Dawn is a spacecraft launched by the U.S. whose primary mission is to investigate the asteroid Vesta and the asteroid and dwarf planet Ceres. Dawn will investigate these two asteroids in particular, because they are large, and supposedly have remained intact for billions of years. Also, the ways in which Ceres and Vesta were very different, one formed with a "wet" or icy composition, and one farther out and closer to Jupiter, which formed with a "dry" or rocky composition. The contrast of these two asteroids makes the information collected very beneficial to an understanding of the formation of the Solar System.

Dawn was launched on September 27, 2007, after having been delayed several times. Dawn's orbit continued as roughly an outward spiral. The spacecraft completed an orbit around the Sun, and had a flyby of Mars on February 17, 2009 to put in on track to reach Vesta. On May 3, 2011, the first images of Vesta were captured.

The first image of Vesta taken by Dawn at a distance of approximately 750,000 miles. Another image was taken of Vesta on July 9, only about a week before entering orbit (below).

The gravity assist at Mars slowed the spacecraft down enough to orbit Vesta until 2012. The probe successfully entered Vesta orbit on July 15, 2011, and has begun conducting scientific experiments. The probe used an array of spectrometers and detectors to determine the surface composition of Vesta. Further analysis of Vesta's gravitational field also revealed clues concerning the asteroid's inner structure.

After orbital insertion, Dawn continued to decrease its orbital altitude, mapping the surface in broad swaths during the month of August 2011, and later spiraled into an orbit less than 500 miles from Vesta, from where it began more detailed surface analyses.

One significant feature of Vesta is the difference between the northern and southern hemispheres. The northern is littered with craters and the surface is as old as the Solar System itself, over 4 billion years! However, by dating estimates, the southern hemisphere's surface only has 1-2 billion years' worth of craters, suggesting that a very large impact by another asteroid may have changed the surface.

A view of Vesta showing the northern hemisphere (top) and southern (bottom). Many long scores in the surface are present near the equator, further supporting the idea of a large impact on the asteroid. The scores are probably a result of internal fracturing. Dawn also characterized the temperatures of various areas of the surface of Vesta, and the climate was found to be such that there may be frozen water beneath the surface in the colder regions, despite the asteroid's reputation as "dry". Also, later data indicated an unexpected abundance of hydrated minerals, supporting the possibility that asteroid impacts may have fed Earth's oceans.

Observation of the surface of Vesta on different wavelengths records a wider range of emitted radiation. This radiation, in turn, indicates the surface composition and structure. In the final two images above, false color imaging highlights the differences in material along the surface. Much of the surface is composed of iron and magnesium-rich dust, probably from the accumulation of material and not reflecting the internal composition. This point of view is confirmed when observing craters, where an impact has exposed lower layers of the asteroid, and these have been found to be composed of different minerals. In early 2012, Dawn revealed the unexpected intricacy of Vesta's composition, including a many-layered structure and an iron-rich core, a scenario characteristic of much larger bodies, including many moons.

Having spent almost year in orbit, the spacecraft adjusted its orbit outward in June 2012 to record final data before Vesta departure. This data underwent continued analysis, yielding even more insight. For example, the distribution of hydrated (incorporating water) minerals was different than expected and in turn changed our understanding of how planetary bodies, including the earth, gather water. Vesta showed evidence of receiving water from a steady bombardment of small dust particles very early in the history of the solar system, rather than by large impacts. Also, Dawn found evidence that Vesta is in effect a "mini-planet" as far as internal structure is concerned; there are layers corresponding to crust, mantle, and core in its interior. However, the composition of the asteroid suggests that the formation process of Vesta is more complex than previously thought.

The spacecraft propelled itself away from Vesta in early September 2012, beginning its spiral outward to reach Ceres. By December 27, 2013, Dawn was closer to Ceres than Vesta. By early 2015, the probe was beginning its approach towards Ceres. In mid-January, it began to resolve surface features, as in the image below.

On March 6, 2015, Dawn entered orbit around Ceres at a distance of about 30,000 miles. The insertion represented two historic milestones in spaceflight: Dawn became the first spacecraft ever to visit (or orbit) a dwarf planet, and the first spacecraft to successfully orbit two extraterrestrial targets. Most approaches to objects in the solar system by other spacecraft have been flybys, but the use of ion thrusters allowed Dawn to repeatedly accelerate and decelerate and orbit multiple bodies.

Dawn's arrival trajectory brought it around the side of Ceres facing away from the Sun. The first images taken in orbit (two are shown above) reveal crescents of Ceres from a distance of 30,000 miles. Over the following months, the spacecraft performed several more maneuvers to spiral in towards Ceres in preparation for entering its science orbit in late April.

During the month of May, Dawn returned numerous images of Ceres from its first mapping orbit. In particular, it captured in great resolution the mysterious "bright spots" on Ceres (see below).

The unusually reflective spots are suspected to be ice, but the spacecraft's data had not yet established this definitively. In late May, Dawn began to spiral inward to an altitude of 2,700 miles where it will enter its second mapping orbit. Further thrusts subsequently brought the orbiter to its final science orbit at an altitude of only 235 miles in October of that year. This allowed images to be taken with resolutions as high as 120 ft/pixel.

Further study revealed that the bright spots were primarily due to the presence of a salt compound, sodium carbonate. Its presence had paradigm-shifting ramifications for our understanding of Ceres's interior, namely that this material must have reached the surface due to hydrothermal activity underneath it. This in turn implies that the asteroid's interior is warmer and more dynamic than previously anticipated.

As the analysis of Ceres continued into 2016, the Dawn mission pursued other techniques of analyzing its interior, including through its gravitational field. More orbital maneuvers were making Dawn's orbit about Ceres larger over time, offering global views. By using radio signals to measure precisely how the spacecraft was responding to Ceres's gravitational pull, scientists could infer the distribution of mass in the asteroid. They concluded that its interior was fairly low in density and was differentiated into layers, as with other large Solar System bodies such as planets.

Another significant discovery occurred in February 2017, when Dawn detected organic molecules on Ceres near a crater known as Ernutet. This was the first discovery of its kind for a main belt asteroid and bolstered theories that meteorites on Earth harboring such materials could trace their origins to these objects. The Dawn mission was extended once again by NASA in October 2017.

The next year, the Dawn team planned further maneuvers to lower its closest approach to Ceres to an even lower altitude. The above photo, taken in May 2018, reveals surface features from an altitude of 270 miles. At the completion of the orbit adjustment (in early June), the spacecraft's highly elliptical orbit brought it as close as 22 miles from the surface before retreating to 2,500 miles on every circuit.

Finally, on October 31, 2018, the spacecraft went silent. After a day of studying the problem, the Dawn team concluded that the probe had finally run out of the hydrazine fuel that enabled it to control its orientation. After over 11 years in space, this concluded the highly successful mission. The image of Ceres below was among the last transmitted by the Dawn mission.

Dawn was the first spacecraft ever to orbit two different extraterrestrial objects and the wealth of data it returned will be invaluable to our future understanding of the birth of our own Solar System.
For more information, see the NASA page on Dawn.

Images from wikipedia, and Dawn website, at

Sunday, April 5, 2009


Kepler, named after Johannes Kepler, was a spacecraft launched by the U.S. The objective of Kepler's mission was to detect exosolar planets, or planets outside our system.

The Kepler spacecraft consisted of a large telescope, equipped only for observing subtle signs of planets. The telescope detected transits, or slight eclipses of light from the star when a planet passes in front. Some of these light changes are so slight that the difference in brightness is equal to that of a fly on a windshield, but Kepler detected them all the same.

The Kepler spacecraft was launched on March 7, 2009 from Cape Canaveral, Florida. It escaped Earth's orbit and settled into its orbit around the Sun, which causes Kepler to follow Earth around its orbit. Kepler went through a commissioning phase and began observation on May 13, 2009. Then, the first information was transmitted to Earth in June. NASA will sorts through the thousands of images to find signs of exosolar planets. In September, Kepler verified the existence of an exosolar planet. The planet's orbital period is just over two days, so Kepler took under a week to detect its transit three times.

On January 12, 2010, the first five new planets were discovered from an analysis of the results obtained in November of the previous year. On August 26, 2010, three additional planets orbiting the same star were announced. Another major discovery occurred in early 2011, when a system of six planets was announced, along with the smallest extrasolar planet yet discovered. Planet discoveries continued to trickle in as the year went on, including another planet in May 2011.

Another interesting discovery was that of a planet, named Kepler-16b, orbiting a binary star system. Discovered in September 2011, it is the first definitively confirmed circumbinary (circum = around, binary = two [stars]) planet. Also, in November 2011, Kepler-21b was discovered. It is a rocky planet only 60% massive than Earth. Unfortunately, it is so close to its parent star that it orbits in less than three days.

On January 26, 2012, 26 new planet discoveries were released, including two more instances of circumbinary planets, and numerous systems containing two or more planets, leading to higher estimates of planets per star in the Milky Way. In response to this unexpected bounty of planets, NASA extended the mission of Kepler through 2016 in April 2012. This allowed the confirmation of orbiting bodies with longer periods of revolution. Other significant discoveries of 2012 include the first known occurrence of two planets orbiting two stars and also the discovery of a planet that orbits one of the two stars in a binary system.

By 2013, Kepler had discovered over 100 planets. In April of that year, planets in the habitable zone of two stars were discovered, and they were also Earth-like in size, being less than twice the size of the Earth. Unfortunately, a failure of the orienting mechanism of the telescope on the spacecraft in May halted observation. The spacecraft was then put into hibernation while NASA planned maneuvers to restore Kepler's mobility. Over the next several months, tests revealed that the failure could not be corrected.

Despite these difficulties, Kepler turned to other observations with its remaining capabilities, including the study of supernovae and small solar system bodies. Meanwhile, analysis of the data that Kepler had already provided continued to reveal many new extrasolar planets. Using a data analysis method called verification by multiplicity, many planets in multiple-planet systems were verified in early 2014, culminating in an announcement on 2014 that an astounding 715 new planets had been confirmed! Several of these planets were also small (smaller than Neptune) and a few were Earth-sized and in their stars' habitable zones.

In April 2014, data analysis revealed the most Earth-like planet yet known: an Earth-sized body orbiting in the habitable zone of its star, a red dwarf. Known as Kepler-186f, this planet is about 492 light-years away, and is potentially habitable.

On May 16, 2014, NASA approved a new mission for the Kepler telescope itself, after scientists developed a method to keep the spacecraft sufficiently steady with only two reaction wheels to observe an area of the sky continuously for over 80 days, enough to detect transiting planets. Using the radiation pressure from the Sun as a counterforce, the telescope can balance the force from the remaining orientation mechanism. The image below illustrates the so-called K2 mission.

Instead of fixing the gaze of the telescope at a small area of sky for a number of years, as in the first scientific campaign, the K2 mission explored several different fields of view, spending a few months on each phase or "campaign". The new mission detected its first confirmed exoplanets in January 2015. That same month, the number of confirmed planets from the Kepler mission surpassed 1000 with the further analysis of previous data.

In July 2015, one of Kepler's more notable planet candidates was confirmed. Known as Kepler-452b, the planet was the most similar to Earth of any yet discovered: it is 60% larger than the Earth in diameter (and therefore has a good chance of being rocky), orbits a sun-like star in an orbit only 5% larger than Earth's, and has an orbital period of 385 Earth days, very close to our own. In addition, the planet is estimated to have existed for 6 billion years, even longer than the Earth, giving it a better chance of harboring life.

Mission operations continued normally until April 7, 2016, at which time it was discovered that the spacecraft had entered emergency mode. NASA immediately made efforts to return the telescope to normal operations in order to make the scheduled maneuver. These effort were successful and the spacecraft was able to resume normal operations on April 22. It was then able to begin Campaign 9 (abbreviated C9) of its mission. This involved using gravitational microlensing to detect planets farther away from their host stars. This works as follows: when a planet passes in front of its star, the mass of the planet causes starlight to bend (very slightly) around it, causing a temporary increase in brightness, as illustrated in a graphic below from Kepler's NASA website.

The scale of the bending is exaggerated here for illustration. Note that for planets close to their host stars, Kepler looked for a decrease in brightness that would indicate starlight being blocked. However, for sufficiently massive and distant planets, the gravitational microlensing effect is larger, leading to a net increase in brightness.

Meanwhile, continuing data analysis continued to yield new planet confirmations from among Kepler's earlier candidates. On May 10, 2016, NASA announced that an additional 1,284 planets had been confirmed, more than doubling the total that Kepler had verified. Among these, almost 550 were of a size that they could be rocky, and nine of these were in the habitable zones of their parent stars.

In June 2016, the mission was officially extended through the anticipated end of Kepler's fuel resources. Over the next few years, the K2 mission confirmed the existence of another few hundred exoplanets. Low on fuel, the spacecraft was still operating in April 2018, when its successor, the Transiting Exoplanet Survey Satellite (TESS) was launched by NASA. Built on the experience gained through the Kepler mission, TESS and Kepler shared the same detection method, but with TESS having a much larger field of view. In May, the K2 mission began its 18th observing campaign, focusing on observing star clusters. Finally, at the end of October 2018, Kepler had exhausted the remainder of its fuel resources. The telescope was officially retired on November 15, 2018, nearly a decade after its launch. During its service, Kepler discovered a remarkable 2662 exoplanets, well over half of the total known at that time. Its success moved exoplanet astronomy forward by leaps and bounds and paved the way for future missions to answer the many remaining questions concerning worlds outside our own Solar System.


Saturday, March 28, 2009

New Horizons

New Horizons is the first spacecraft ever to travel to the dwarf planet Pluto. The main objective of the mission is to observe the distant Pluto for the first time as well as photograph the five known moons Charon, Nix, Hydra, Kerberos, and Styx, and perhaps some moons not yet discovered.

New Horizons was launched on January 19, 2006 from Cape Canaveral, Florida. As it escaped Earth's gravity, it reached a speed of 36,360 miles per hour or 10.1 miles per second! Shortly after launch, it passed the moon, and by April 7, 2006, it had passed Mars's orbit. Soon after, in May 2006, New Horizons passed into the asteroid belt. It is true that there are many asteroids in the belt, but they are very far apart. The closest flyby of New Horizons to an asteroid was 132524 APL at about 60,000 miles on June 11-13, 2006, and the probe took this opportunity to test its instruments. However, at risk for damaging its instruments by looking at the Sun, New Horizons did not unveil its more powerful telescope, LORRI for this distant flyby.

New Horizons's pictures of the distant asteroid 132524 APL. The diameter of this asteroid is estimated at about 1.4 miles.

By late October, New Horizons had left the asteroid belt and was on target for its flyby of Jupiter. In early January 2007, New Horizons began its Jupiter encounter. As New Horizons passed Jupiter, it tracked and took photos of Jupiter's outer moon, Callirrhoe as practice for navigation. Also, New Horizons made observations of other of Jupiter's moons and edited their orbit information. On February 28, 2007, New Horizons passed its closest to Jupiter at about 1.3 million miles from the planet. On March 5, the Jupiter encounter came to an end.

On June 8, 2008, the probe passed Saturn's orbit. On March 18, 2011, New Horizons passed the next planet, Uranus. On December 2, 2011, New Horizons's distance from Pluto dropped below 983 million miles, the closest approach to Pluto ever by a spacecraft. This surpassed Voyager 2's record set in the 1980's, although this mission was not directed toward Pluto. In 2012, New Horizons began a series of simulations to test equipment for the Pluto encounter.

In 2013, analyses on the Pluto system assessed growing concerns that the many moons of the Pluto system suggested the presence of other extraneous debris - in other words, a possible threat to the spacecraft. The current planned trajectory takes New Horizons to a relatively safe area, namely near the orbit of Charon, Pluto's largest moon and its binary companion. The reason that this was theoretically safer was that Charon, being large, clears the debris in its orbit with its gravity, unlike its smaller satellite neighbors. However, just in case a closer look revealed danger, alternate flyby plans were devised. Later analyses concluded that the risk was not significant and that New Horizons could proceed as planned.

In July 2013, New Horizons was close enough to distinguish Pluto (bright spot at center) and its largest Moon Charon (dim spot just above and to the left of Pluto).

On its path towards Neptune, New Horizons approached the Neptune's L5 point in late 2013, allowing the spacecraft to take a few observations of recently discovered asteroids near that location. On October 25, 2013, New Horizons became less than 5 AU (astronomical units) from Pluto.

On August 25, 2014, the probe passed Neptune's orbit, at which point it was only about 2.5 AU from Pluto. On December 6, 2014, the spacecraft emerged from its final period of hibernation before the Pluto encounter. Over the next several weeks, the operations team checked the functioning of the system's instruments.

During the final approach, image resolution improved steadily. By early February, New Horizons was able to discern both Nix and Hydra, two of Pluto's smaller moons (though Styx and Kerberos are smaller still).

In the above image, Hydra is highlighted by a yellow diamond and Nix by an orange one. The lefthand image shows the Plutonian system and background stars, while the right has been processed to emphasize the Moons. The bright streak in each image is an artificial effect of the camera resulting from overexposure of Pluto.

On March 10, New Horizons passed its final symbolic milestone as it became less than 1 AU from the dwarf planet - closer than the Earth is to the Sun. New Horizons also realized its first color image of Pluto and Charon on April 14, 2015.

The following month, images from New Horizons became the best ever looks at Pluto. During June, the probe revealed reflective polar regions, dark spots and other tantalizing features of Pluto as well as on Charon, also capturing the massive difference in coloration between the two objects. Some of these features appear in the image below, taken between June 25 and June 27.

On July 14, 2015, at precisely 11:49:57 UTC, the New Horizons spacecraft made its closest approach to Pluto at a distance of 7,800 miles (12,500 km). During the flyby, all instruments were busy collecting data, so it was only hours afterward that the probe sent a signal to Earth confirming the flyby's success. After an additional 4.5 hour delay for the radio signal to travel, news of the mission's success reached Earth over 10 hours after closest approach. New Horizons took the following path through the Pluto system:

The above image shows the positions of Pluto and its moons when New Horizons made its closest approach (C/A). After closest approach, the probe briefly passed into the shadow of Pluto and then of Charon, allowing it to observe how sunlight interacted with the bodies' atmospheres.

The first image, taken before the Pluto flyby, shows the never-before-seen world in true color. The photograph, with its iconic heart-shaped feature, became one of the most famous images captured by a spacecraft. The second image shows the mostly gray coloration of Charon as well as its reddish polar cap.

The analysis of Pluto's atmosphere (primarily conducted as New Horizons passed behind the shadow of Pluto) indicated that it was dominated by nitrogen, and that this nitrogen escaped the relatively weak gravity at a rapid rate. This fact, added to the observed complexity of the surface's texture and composition from enhanced-color imagery, indicate that Pluto is geologically active.

In August, NASA identified the Kuiper belt object designated 2014 MU69 as the next target for New Horizons under the constraints of its diminished fuel supply.

Meanwhile, data from the Pluto encounter continued to produce astonishing discoveries. For example, the occultation images showed that Pluto's outer atmosphere is in fact a blueish color, an effect caused by the scattering of sunlight off of complex molecules. These molecules form through the interaction of nitrogen and methane with solar wind.

In addition, surface analysis revealed the presence of exposed water ice on Pluto, indicated in the image above. All of this analysis and more was completed before New Horizons even finished transmitting data from the Pluto encounter. Due to the limited power supply on the spacecraft as well as other factors, the images and instrument readings that were all collected within a few days took well over a year to transmit. It was only in late October 2016 that Earth finished receiving the stored data. In April 2017, after being "awake" since late 2014, the New Horizons probe went into hibernation for several months as it moved through deep space. Other than routine course corrections and instrument tests, the spacecraft spent most of its time in hibernation over the following year.

The end of this hibernation came in June 2018, when the spacecraft "awoke" once again. With its systems functioning normally, the time had come to prepare for its flyby of 2014 MU69, which was now less than 150 million miles away (a comparatively small distance compared to the 3.8 billion that the spacecraft had already traveled). This object had been nicknamed "Ultima Thule" a few months earlier, referring to a classical term for a place beyond the borders of the known world. Kuiper Belt objects such as Ultimate Thule have remained nearly unchanged since the formation of the solar system. On December 2, New Horizons underwent a small course correction at a unprecedented distance of over four billion miles from Earth. The flyby program began December 26.

At 12:33am EST on January 1, 2019, New Horizons made its closest approach to Ultima Thule (2014 MU69) at a distance of 2,200 miles (3,500 km) from its surface. This was a much closer approach than to the Pluto system, partially because Ultima Thule is a much smaller body, but it did make the risk of encountering orbiting debris somewhat higher. The flyby itself was at a distance from Earth of about 4.1 billion miles (6.6 billion km), making it the most distant flyby ever. A few hours after, the probe took a small break from its outbound science objectives to transmit a telemetry signal to Earth and confirm success. However, New Horizons was so far from Earth that the signal took over 6 hours, even at the speed of light, to reach the satellite dishes of the Deep Space Network (DSN) at 10:30am EST.

After the science mission was concluded, the long process of transmitting data back to Earth began. As in the Pluto encounter, this was a process that lasted more than a year. The first images returned (such as the one below) were low-resolution, but revealed Ultima Thule to be a conglomeration of two objects stuck together!

The above image is black and white, but Ultima Thule is in fact a reddish color. The larger and smaller lobes of the minor planet were nicknamed "Ultima" and "Thule" respectively, with the whole object being about 21 miles across at its largest extent.

NASA scientists speculated that Ultima Thule was formed through an accretionary process, illustrated above. A "cloud" of small objects at the beginning of the solar system gradually coalesced into two objects, which over great spans of millions of years gradually shed angular momentum until they eventually touched. New Horizons found that the binary object rotates with a period of 15 hours today.

The above image of Ultima Thule appeared on the cover of Science magazine and is a composite of the highest quality black-and-white photos obtained by New Horizons and data about color collected by other instruments. In November 2019, Ultima Thule received the official name Arrokoth, meaning “sky” in the Powhatan/Algonquian language.

The above image shows New Horizons's path from Earth to Pluto.