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Scratchpad

Most Significant Systems

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Exoplanetary Scratchpad

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List of most significant stellar system.

Pulsar Planets

  • PSR B1620-26 System - A helium white dwarf and a pulsar in the middle of the crowded core of the M4 star cluster, around which , the oldest known planet, nicknamed "Methuselah, orbits. It was formed only 1 Billion Years after the big bang and is 13 Billion years old. The planet may be a brown dwarf.

Early Dopplar Pioneer Systems

  • 51 Pegasi System - Contains the first exo-planet around a normal star discovered and the first "Hot Jupiter" found, which is nicknamed "Bellerophon". Found to have supersonic winds that caused the eternal night-side hemisphere to be as hot as the day-side one.
  • 55 Cancri System - Wide binary star consisting of a sun-like primary (A) and a red-dwarf secondary (B) separated by 1,100 AU, 41 light years away. Star A contains five exoplanets, the first system found with this many. It has three tightly packed eccentric planets close in to the star, including planet e (hot Super Earth/Neptunian), b (hot Jupiter), and c (hot Saturn). Planet e was the first Neptunian discovered. It was later found to be the shortest-period planet discovered (18 hours) and to transit. The planet has about half of Neptune's mass, but is Earth-like in size and density (2.17 Earth Radius). It is composed 70% of rock and the outer 30% is likely an ocean of super-critical water (between a gas and liquid state) that is 3000km thick. This is the hottest and densest super-Earth and the is the most watery planet found to date. It likely possesses a thick atmosphere of CO and CO2. The brightness of the star (also closest known to transit and only known naked eye star to do so) makes it more easily studied than other hot super Earths. Planet f is a very eccentric Saturnian in the habitable zone. Planet d is a super jovian at Jupiter-like distances, which was the first found at true Jupiter distances and still the exoplanet discovered with dopplar spectrometry with the largest known semi-major axis. The distant outer star causes planet d's axis to flip on its axis every million years. Planet d in turn causes the other planets to flip, including its star. The axis tilt of transiting planet e should be determined at some point. "Bode's law" predicts four undiscovered planets.
  • Upsilon Andromedae System - A nearby (44 ly) multi-star system which is the first multiplanet system found around a main sequence star. The main star around which the planets orbit is a yellow-white star somewhat younger than the sun and its companion is a red dwarf in a wide orbit. It is one of the most well studied non-transiting star systems. Roaster Planet b (0.05 au, 1.4 MJ, e=0.013) is nicknamed the Fire and Ice Planet because it is hot on one side and cold on the other. The hottest parts of the planet are near the trailing side terminator at the equator, due to high velocity winds transporting heat to the night side. This is 80deg offset from the starward pole and a much greater offset than other observed hot Jupiters. This threw astronomers off and caused them to doubt the wind-theory, though later observations of other planets have shown that winds indeed can travel fast enough to cause this. The middle planets c (0.83 au, 14 MJ, may actually be a brown dwarf star, e=0.224) and d (2.5 au, 10 MJ, e=0.26) have had their inclinations and masses determined with astrometry. They are very eccentric and highly inclined to each other (30 deg). Planet scattering was thought to be a source until the outermost planet was discovered. This is planet e (5.2 au, 1.05 MJ, e = 0.005), which is the most Jupiter-like exoplanet known, and is in 3:1 resonance with planet d. The star appears to have no Kuiper-belt like disc, perhaps due to its companion star sweeping away this material.
  • Tau Bootes System - (aka Tau Bootis) Contains one of the first discovered Hot Jupiters, which was one of the largest and hottest of the earlier discovered ones. First planet-bearing star to have its magnetosphere probed. Hot Jupiter is embedded within it and tidally locks the star's rotation.

Transiting Systems

  • HD 209458 System (1999) - Has first discovered transiting planet which was nicknamed Osiris due to the comet-like tail detected and the first exoplanet around a normal star to have its mass directly measured. The planet may be losing its outer atmosphere, or magnetism may prevent the ions from escaping. They detected water in its atmosphere (they had failed earlier), the first time this has been done for any exoplanet. 2nd Exoplanet with detected organic compounds; like HD 189733b, it has water and carbon dioxide, but it has a lot more Methane. Tracking carbon molecules with dopplar spectrometry caused it to be the first exoplanet detected to have winds, which are raging at 5,000 to 10,000 km/h. This is believed to cause hotspots to appear at terminators rather than at the star-ward facing point.
  • OGLE-TR-56 System (Nov 02) - Contains first planet discovered by transit and later confirmed by Dopplar Spectroscopy (rather than the other way around). The first OGLE planet confirmed with the Dopplar method. It is 6000 ly away, 10 times as far as any previous known planet, in a different arm of the galaxy. Also the first Very Hot Jupiter discovered. It may meet its doom in less than a million years. Planet has one of the first two ground-detected atmospheres. Has an atmosphere hotter than any other measured so far. Unlike other hot Jupiters observed, it is way too hot for clouds of silicon or iron to form which would keep it dark.
  • TrES-1 System (Mar 05) - Contains the first transiting exoplanet discovered with the TrES amateur equipment and second transiting exoplanet close enough to have its atmosphere studied. It is the first Hot Jupiter that had the expected radius. Was the one of the first two exoplanets to have its light separated from its host star.
  • HD 189733 System (Dec 05) - Planet b (the first nearby Very Hot Jupiter, originally thought to be inflated) is the nearest planet discovered using the transit technique (62.9 ly). This is the first exoplanet to have its temperature mapped and was nicknamed Bull's Eye for its hot spot that is significantly offset from the starward pole. It is also the first exoplanet for which scattered light in the upper atmosphere has been detected and the second exoplanet with water detected and first with Methane and then Carbon Dioxide detected. It later was the first exoplanet whose gasses were detected from Earth-based telescopes. It was also found to spin up its star and magnetically interact with it, causing stellar storms. Hubble found that its atmosphere was a uniform blue haze.
  • TrES-2 System (Sep 06) - Contains TrES-2, which was the most massive nearby transiting planet until the discovery of Hat-P-2 b. It has a large radius for a planet not considered inflated. A large ground-based telescope method of observation was pioneered on this planet. Since its in Keplar's field of view, it was observed by it as a test subject and dubbed Kepler1b. A second planet is possibly responsible for fluctuations in the first's inclination. Kepler determined that it is the darkest known planet, blacker than coal, due to its extremely low dimming and brightening detected during transits. It would appear black except for some faint red tinge. This conflicts with current theories, which thought that a Hot Jupiter could only get as dark as Mercury. It appears that the planet is too hot for reflective clouds to form and instead its atmosphere contains light-absorbing chemicals. An off-the-cuff nickname Erebus (Greek god of darkness) has been suggested. It was also the first planet whose phases have been detected.
  • Gliese 436 System (May 07T) - The second known red dwarf planetary system. Contains one of the first Neptunians discovered. Planet b temporarily later found to be the smallest exoplanet (about Uranus' diameter, though over 50% its mass) known to transit its host star and is currently the nearest (33 ly). Its temperature (712K) was measured to be higher than what it would be purely from radiation (520K), perhaps due to a greenhouse effect, somewhat higher than Venus. It was originally thought to have a layer of "hot ice", water solidified due to high pressures. It turned out that it was larger than thought and hot ice was not needed. It could still be a rocky super-Earth. It was later found to have a remarkably low levels of Methane and high levels of Carbon Monoxide for its 800K temperature. Possible explanations include Methane being changed into hydrocarbon polymers due to its star's ultraviolet radiation, CO being drafted upwards with winds, or observational defects. It's significant eccentricity suggests a possible neighboring planet. Planet c was announced to be the smallest known exoplanet (1.5 Earth's diameter), but was later retracted because variations in transit timing of the first planet did not occur and the proposed orbit would be unstable. It is still thought that a second planet of some kind is possible in the system.
  • WASP-12 System (Sep 08) - The shortest period transiting Hot Jupiter known and the first carbon-rich planet ever found (more Carbon than Oxygen). One of the two largest known planets at 1.79 Jupiter radii. Hottest known exoplanet at time of its discovery. Planet is being ripped apart by star. It is stretched in the shape of a rugby ball and leaves a ring around its star. Huge cloud of material detected around the planet containing elements never before detected on an exoplanet. It has much more methane than water vapor. It may produce shock waves as it plows through its star's stellar wind (the first evidence of shocks around an exoplanet, like Earth and Saturn's bowshocks), possibly produced by a strong planetary magnetic field. This could protect its atmosphere from being stripped away. It could have a diamond core and other terrestrial planets in system would have black spots on them and also be carbon based.
  • HD 80606 System (Jan 09) - Multiple star system with a planet, which has a higher period (111 days) than any other known transiting planet and highest eccentricty (Halley's comet-like). Discovered in 2001, but found to transit in 2009. Its orbit brings it from epistellar distances to Earth-like distances. Planet is the first one for which changes in weather have been observed. Potassium was detected from the high wind regions of the exosphere. In 2010 it was found to be only one of the two out of all 79 known transiting exoplanetary systems that could not support a habitable Earth-like planet, since its elongated orbit would destabilize any such planets.
  • CoRoT-7 System (Feb 09) - A sunlike star about 500 light years away with two Hot Super Earths (and possibly a third), including the first detected transiting Super-Earth. It a diameter about twice that of the Earth. First exoplanet with evidence of a solid surface and does not possess a thick atmosphere. Because its star is active, its mass is somewhat uncertain (2.3 to 8.5 ME), which makes it unclear if the planet actually has a solid surface. Also the closest exoplanet to its star known and has the smallest orbit period (0.85 Earth Days). Likely the first Super-Io discovered (due to slight eccentricity) and the first gas giant remnant core found. Has temperature of 1000-1500C. Planet c is a larger Neptunian orbiting further away and does not transit.
  • GJ 1214 System (Dec 09) - A red dwarf system containing the first exoplanet discovered by the MEarth project, which seeks to detect transiting Earth-like planets around nearby red dwarves, and the second transiting super-Earth. The planet is the first of a new class of planets with low mass and low density. It is between Earth and Neptune in radius and it could be a small Neptunian, a terrestrial with an outgassed atmosphere, or a water world. Its featureless spectrum (the first Super Earth atmosphere ever studied) suggests a heavy atmosphere choked with water steam or one with thick water clouds above it, making viewing the surface impossible (further studies should resolve this). It may be the coolest transiting planet detected. Its close proximity (under 50 ly) assures promising future observation.
  • CoRoT-Exo-9 System (Mar 10) - First temperate transiting Jupiter discovered. An 80% Jupiter Mass planet orbiting at a Mercury-like distance. Temperature could be between -20 to 160 C. Liquid water in the form of water clouds could exist. If its too hot, it could be cloudless. A moon covered by ice or liquid oceans could be around it, depending on its temperature.

Nearby Systems

  • Epsilon Eridani System - Nearest single non-red dwarf star to the Sun and the second nearest system with a confirmed planet. The planet is a very elliptical Jupiter-like world. It also has two asteroid belts and a kuiper belt, with evidence of planets in between.
  • Gliese 876 System - Very nearby quadruple planet system and the first Red Dwarf found to have planets. The innermost planet (d) was the first found rocky planet around a normal star (the first true Super-Earth, at epistellar distances). The outer three planets c (Saturnian), b (Jovian), and e (Neptunian) are in 1:2:4 (30d/60d/120d) resonance (the exoplanet resonance and first triple-resonant planets discovered). The outermost planet has a Mercury-like orbit however it is very much colder than Mercury. Gliese 876 e actually receives only slightly more warmth from Gliese 876 than Jupiter does from our Sun. Planet b is second discovered by ELODIE after 51 Peg b and the second to have its mass exactly measured and the first to have done so by astrometry.
  • Gliese 581 System - Small nearby Red Dwarf with six planets in tight circular orbits and a distant Kuiper belt where many comets orbit. Gliese 581 e was, at the time of its discovery, the smallest known dopplar-detected exoplanet and a super-Mercury, b is a hot-Neptunian, c is a super-Venus and the first detected in the habitable zone (initially heralded as habitable, but later thought too hot due to the greenhouse effect), g is a super-Earth and the first detected in the middle of the HZ (and is highly controversial, having many doubters and defenders), d is a super-Earth on the outer edge of the HZ which could support liquid water (due to its presumably large atmospheric pressure and carbon dioxide), and f (its existence is also highly controversial) is a cold super-Earth. Much further out, from 25 ± 12 AU to more than 60 AU, there is a cold debris disk reminiscent of the Kuiper belt but with 10 times more comets than the one in our solar system. The star is not very active.

Photographed Systems

  • 1RXS J160929.1-210524 System - Contains first exoplanet (full name 1RXS J160929.1-210524) imaged around a sun-like star, photographed in 2008 and confirmed to orbit star in 2010. The planet's very large distance from the star 330 AU causes problems for planetary formation theories. Some liken it to an unbalanced binary star system where one component gobbled up the vast majority of the dust. It has about 8 times Jupiter's mass and 11 times Neptune's distance. It could be a new type of sub-stellar object between a planet and a Brown Dwarf. First exoplanet to have its spectrum taken, which revealed evidence of water, carbon monoxide, and hydrogen. Its star is young enough (5 MY) so that the planet has not had enough time to cool (1,500 C) and thus detectable.
  • HR 8799 System - Hot young star system which is the only imaged and wide multiplanetary system. The 30 MY old star is the only known Gamma Doradus variable that is also a Vega-like star. The innermost is e (14.5 AU, 10 MJ), followed by d (24 AU, 10 MJ), c (38 AU, 10 MJ), and b (68 AU, 7 MJ). Inside the inner planet's orbit is an asteroid belt, while outside of the outer planet is a cometary belt (including a clump at 1:2 resonance with the outermost planet), while further yet is a huge halo extending to 2000 AU. The outer three are planets are 2-2.5 times as far as Saturn, Uranus, and Neptune are respectively, but receive similar radiation. The large planets would likely pull the system apart, leading scientists to believe the inner three planets are probably locked in a 1:2:4 orbital resonance in order to maintain stability. An inner planet is at Saturn-to-Uranus-like distances and challenges planetary formation models. Fomalhaut is the only other system where interaction between planets and dust belts can be observed. They are near the upper limits of mass to be classified as planets and could be Brown Dwarves. All three planets were later found in archived Hubble images. The middle planet became the first to have its spectrum directly measured. The spectrum confused scientists and didn't fit current formation theories. They contain carbon monoxide and are depleted in methane, which suggests they were formed in part by absorbing comets in the system. The outermost planet b has unusually thick dust clouds.
  • GJ 758 System - Star with a giant planet or Brown Dwarf (M betw 10-40MJ) which has been directly photographed. Reguardless of its nature, it is the first and coolest substellar companion to a sunlike star ever photographed (333 C, about as hot as Mercury). It orbits at about Neptune's distance and is still in the contraction phase. A possible third companion may have been imaged, later observations should determine if it is bound to the system or merely an object in the background.
  • Fomalhaut System - Fomalhaut dust disk is observed in unprecedented detail. It appears reminiscent of the "Eye of Sauron" from the Lord of the Rings films. A planet suspected of causing a sharp gap in the ring was suspected and imaged, becoming the first undisputed exoplanet imaged and the first planet since Neptune to be predicted prior to its discovery. The planet orbits about 115 AU and is between Neptune and 3x Jupiter's mass in an eccentric orbit. Planet b was shown to deviate slightly from its predicted path, stirring up some controversy about the planets' existance. Material surrounding the planet may have been imaged, rather than the planet itself, which some say should bump it off the directly imaged list. Also, the Hubble instrument that detected it is damaged and will not be fixed, making it unobservable for a time.
  • Beta Pictoris System - First star found to have a circumstellar disk and the source of most interstellar meteorites in the Solar System and the nearest star with a planet that has been visually detected (61 ly). Contains the youngest known exo-planet, which shows that Jupiter-like planets can form much quicker than previously believed. It is the closest-in exoplanet photographed and is at 8 AU and 7-11 Jupiter Masses and orbits in 20 years. This planet was first hinted at by studying dust disks in 2003 and first photographed in 2003, but it was not confirmed and was lost. It was imaged again in 2008, and became the first imaged exoplanet confirmed to move around its star in 2010. It has an effective temperature of 1,100 to 1,700C, showing that it is still warm and has retained much of its heat from its formation. Evidence of a planetary transit in 1981 was found in record. It was originally thought that a second planet must have caused a tilt in one of the disks, but now it known that the first planet is. Some data suggests the planet is unusually wide, perhaps evidence of a ring system around it. The planet is traveling through a relatively dust-free gap in the debris disk, and thought to be clearing it. The planet is losing momentum as it travels through the debris disk.

Dust Disk Systems

  • Vega System - Nearby star with one of the first detected circumstellar disks. Recently, it was surmised that this disk was caused by a collision between Pluto sized objects.
  • Tau Ceti System - The nearest single G-class yellow dwarf to the sun. It has five super-Earth sized planets in orbit around it, discovered using a new and very powerful but also controversial technique, and an outer debris disk with ten times more material than our solar system's Kuiper belt has.

Two of the planets in the Tau Ceti system are located on opposite edges of a very liberally described habitable zone, analogous to Venus and Mars. No planet has as yet been detected near the middle of the habitable zone, in a situation similar to Earth.

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