Andy's Wiki
Exoplanetary Scratchpad

[SysBP Img]

Here is a list of systems that contain multiple sub-stellar companions. "Plus" systems also include either a circumstellar disk, a brown dwarf, a nearby companion star, or an unconfirmed planet.

Eight Planet Plus Systems[]

  • Solar System - Home system of Earth, the only confirmed habitable planet. Also has three other terrestrials, two Jovians, two Neptunians, several rocky and icy Dwarf Planets, a asteroid belt, a kuiper belt, and an Oort cloud.

Five Planet Systems[]

  • 55 Cancri System - Copernicus is also known as Rho Cancri, 55 Cancri, Rho1 Cancri, HR 3522, Gl 324, and HD 75732. Wide binary star consisting of a sun-like primary (A, though super metal rich) 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 four or five planets. It has three tightly packed eccentric planets close in to the star, including planet Jannsen (e, hot Super Earth/Neptunian), Galileo (b, warm Jupiter), and Brahe (c, hot Saturn), followed by an eccentric Saturn in the habitable zone (Harriot, f) and a Jupiter analog, Lippershey (d). Planet e was heralded as the first Neptunian discovered. It was later found to be the shortest-period planet discovered (18 hours) and to transit. Its density was measured and determined to be rocky, and thus re-dubbed the first Super-Earth discovered. It was then the first super-Earth to have its light detected (by Spitzer in the infrared). The planet has about half of Neptune's mass, but is Earth-like in size and density (2.17 Earth Radius). Studies taking into account the composition of the star suggested that it was largely made of diamond, with graphite at the surface (the first diamond planet around a Sunlike star), and the first terrestrial found with fundamentally different surface composition and processes than Earth. This was later refuted when it turned out there wasn't as much carbon in the parent star as believed. Earlier studies that assumed an Earth-like composition suggested that it would be covered with an ocean of super-critical water. The brightness of the planet was found to have raised dramatically, possibly the aftermath of cloud cover due to a volcanic eruption. 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. It was found to be dark and its sun-facing side hot enough to melt metal. It became the first super Earth to have its atmospheric composition measured (mostly hydrogen and helium with hints of hydrogen cyanide which would only dominate in a carbon-rich environment and no traces of water vapor) and temperature mapped, and the large hemispherical temperature differences suggest little atmosphere to transport heat. Planet b (one of the original 4 Hot Jupiters discovered) is the first "warm Jupiter" found to have a puffed up atmosphere and it probably at the outer limit from the star at which a planet can lose its atmosphere in this way. Its outer atmosphere skims the surface of the star, which was detected when attempting to detect an atmosphere around transiting Janssen. The strong interaction between planets Galileo and Brahe can be detected in measurements, and it took a while to find a fit that would allow them to survive over long periods of time. Harriot 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. It was first thought to be circular, then eccentric, and then circular again. The distant outer star causes Lippershey's axis to flip on its axis every million years. Lippershey 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. One of the first 20 exoplanet systems allowed to be given common names by the IAU.

Four Planet Systems[]

  • Mu Arae System - Cervantes (Mu Arae) is a 6th magnitude Sunlike star close to becoming a Sub-Giant located 50 ly with four known planets. At first believed to be a system dominated by orbit crossing eccentric Super Jupiters. Instead, three Jovians orbit in roughly circular orbits at Earth-like (Rocinante, d), Mars-like (Quixote, b, in habitable zone), and Jupiter-like (Sancho, e) distances in addition to an inner (Dulcinea, c) Hot Neptune. Planet c was one of three Hot Neptunes or Hot Super Earths discovered around the same time. It was the first one announced, but it was still under scientific review at the time, so there remains controversy on what the actual first planet discovered of this class is. Initially thought to likely to be rocky because it had 2 known neighboring gas giants which may have stunted its growth. The characteristics of the planets in this system changed greatly as new planets were discovered, and included a re-ordering of their designations. Initially, the first planet b was thought to be highly eccentric. An outer planet was then detected, at the time dubbed "c" (though a full period hadn't yet been observed), and was thought to have an extremely high eccentricity so that the orbits of the two planets would cross. An innermost third planet then dubbed "d" was then detected. A new fit for the data then emerged, and it was found that the outermost planet was actually much less eccentric, and that there was a planet interior to planet b with almost half its period. The eccentricity of b was also reduced so that no planet criss-crossed another's anymore. It was decided to redesignate the planets in order of characterizations instead of by discovery, so the innermost Neptunian planet was re-dubbed "c" and the planets just interior and exterior to planet "b" were re-dubbed "d" and "e". The system became the second known 4-planet system. The innermost two Jovians are close enough so that they're unstable over short periods of time. If they were actually in 1:2 resonance, which almost fits the data, they would be much more stable. One of the first 20 exoplanet systems allowed to be given common names by the IAU. Star is named after the author of Il Ingenioso Hildalgo Don Quixote de la Mancha and the planets after its characters, Quijote (main character), Dulcinea (love interest), Rocinante (horse), and Sancho (squire).

Three Planet Plus Systems[]

  • PSR B1257+12 System - The first extrasolar system confirmed and one of the only planetary systems known around a pulsar. Has three rocky planets that orbit closer than Venus. The innermost has a Moon-like mass, while the next two out are Super Earths. May also have an outer "comet" sized body, the first sub-planetary object detected and possibly a representative of a mini "kuiper belt" at asteroid belt like distance.
  • HD 69830 System - First planetary system found that does not have a Jupiter-sized planet around a normal star (K0 spectrum). Contains 3 Neptunians and the first discovered asteroid belt that is like the size and age as the Sun's. The debris from this belt that was detected was from the breakup of an asteroid, is 20 times as massive as our own, and would cause zodiacal lights 1000 times brighter than we see from Earth. The smallest and outermost planet may be a 10 ME super Earth, is within the habitable zone, and is an inner shepherd for the asteroid belt. Halo 3 features a fictitious moon around this planet.

Three Planet Systems[]

  • Upsilon Andromedae System - Titawin (Upsilon Andromeadae) is a nearby (44 ly) multi-star system which is the first multiplanet system found around a main sequence star or a multi-star system. 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 Saffar (b, 0.05 au, 0.62 MJ, e=0.013, and the nearest true Hot Jupiter to Earth) 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. Stability studies and observations suggest its diameter is 1.8 DJ, rather large for a planet its age. The middle planets Samh (c, 0.83 au, 1.8 MJ, initially thought to possibly be a brown dwarf star, e=0.224) and Majriti (d, 2.5 au, 10.2 MJ, e=0.26) have had their inclinations and masses determined with astrometry, the first determination of relative inclinations of exoplanets. 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. Planet c is in the habitable zone, though any habitable moons would see drastic temperature swings. The star appears to have no Kuiper-belt like disc, perhaps due to its companion star sweeping away this material. One of the first 20 exoplanet systems allowed to be given common names by the IAU. The star is named after an important city in Morocco that bridged the Spanish and Arab worlds. The planets are named after famous Andalusian astronomers.
  • Gliese 876 System - Ross 780 is also known as Gl 876 and the flare star IL Aquarii. Very nearby quadruple planet system and the first Red Dwarf found to have planets. The innermost planet (d, Hot Superterran, rocky-water) was the first found rocky planet around a normal star (the first true Super-Earth, at epistellar distances). The outer three planets c (Warm Saturnian), b (Warm Jovian), and e (Cold 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. 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.
  • HD 37124 System - The fourth triple planet system discovered around a normal star, the last one announced with 4 other multiplanet components in 2005. A Sunlike star with Jovian planets that received Venus-like, Mars-like, and Asteroid Belt-like radition from their stars. Simulations showed that no terrestrial planets could form between the Venus-like and Mars-like Jovian planets.
  • Gliese 581 System - BD-11°3759 is better known as Gliese 581. Small nearby Red Dwarf with six planets in tight circular orbits. Several planets were announced in the habitable zone, but have since been retracted due to being due to sunspots rotating in view during it's 130 day rotation. E is 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 HZ (initially heralded as habitable, but later thought too hot due to the greenhouse effect). G (1/4 stellar rotation) was the most controversial heralded as the first habitable Super-Earth and "Eyeball Earth", but was disproven. D (1/2 stellar rotation) was later thought to be an even more promising planet for life as it was big enough for a decent greenhouse effect even though it was at the outer edge of the habitable zone, was later thought to also not exist, but then its existence was re-affirmed. F was thought to be a cold super-Earth, but also disproven. The star is not very active. A massive Kuiper Belt was found, which may have been allowed to exist because the system lacks a Jovian class planet. A further out Neptunian may be responsible for the cometary collisions that produced the debris.

Two Planet Plus Systems[]

  • HD 82943 System - Yellow dwarf with two large orbit-crossing Jovians locked in 1:2 orbital resonance that would span the inner solar system, which were disccovered by the Swiss team by 2001. The planets have nearly identical mass (1.8 MJ). Shown to have a dust disk by Spitzer.
  • HD 128311 System - An orange dwarf star with two jovians (a Jupiter analog detected in 2005 and an eccentric giant in the outer habitable zone) possibly in 1:2 resonance and a dusk disk detected by Spitzer.

Two Planet Systems[]

  • 47 Ursa Majoris System - (aka Ursae Majoris) Chalawan (aka 47 Ursae Majoris) is solar analog (G1 V, about the same age as the Sun) with 3 planets 46 ly away. One of earliest systems discovered. Taphao Thong (b, 2.5 MJ, 2.1 AU) and Taphao Kaew (c, 0.5 MJ, 3.6 AU) are in circular orbits at asteroid-belt like distances, while planet d (1.6 MJ, 11.6 AU) is in a distant more eccentric orbit (0.16, 9.6-13 AU). Planet b was the first found to have a circular orbit beyond the habitable zone. The discovery of planet c made the system the first multiplanet system whose planets have circular orbits, and b and c are rough Jupiter-Saturn analogs in relative size and positions. Their existence was in doubt until planet d was discovered. Planet d has not yet completed a full year (38.4 years) yet since its discovery (it cannot be named yet), but is the furthest out planet discovered with the dopplar spectrometry method. Studies have shown a terrestrial planet could only form in the innermost part of the habitable zone. Several transmissions have been sent to the star system. One of the first 20 exoplanet systems allowed to be given common names by the IAU. Star named after a Thai crocodile asterism and its planets are associated with two sisters associated with this legend. Taphao Thong was captured by the crocodile, while her sister Taphao Kaew married the one who rescued her.
  • HIP 14810 System - System with two eccentric planets discovered in 2006 by the Carnegie team. One is a moderately eccentric massive Hot Jupiter, while the other is a very eccentric half-Jupiter orbiting at Mercury-like distances.
  • HD 217107 System - Contains the first discovered moderately eccentric Hot Jupiter. Its outer planet was suspected when the inner one was discovered due to its eccentricity (0.13) and confirmed with four other new multiplanet systems in 2005. The Outer planet c is highly eccentric and skirts the outer edge of the habitable zone.
  • Gliese 777 System - Outer planet of the primary star was initially believed to be a Jupiter analog, but later found to be eccentric (its apastron is at Jupiter-like distance). Its second planet was the fourth Neptunian discovered and was announced with four other "second" planets in 2005.
  • HD 74156 System - Sunlike star with two planets more massive than Jupiter, one in about Mercury's position, and one at an Asteroid Belt-like position. A planet was predicted in between these two at Earth-like distances and later found, the first vindicated prediction since Neptune. This supports the "Packed Planetary Systems" theory. Some have suggested that it's one Earth year orbit period may mean its detection is due to Earth based observation errors.
  • HD 169830 System - Bright star with two eccentric planets known in 2003. One is likely too hot to have any clouds, while the other one is likely to sport white water cloud bands.
  • HD 12661 System - System with two Jovians that could support water clouds discovered in 2000 and 2002. The innermost one may be an "Eccentric Sulfurous Cloud Giant".
  • HD 108874 System - System with two Jovians that could have bands of white water clouds. The inner planet is in a circular orbit and enjoy's Earth-like heat. Its second planet, which was announced with four other new multiplanet systems in 2005, is in an eccentric orbit that would span our solar system's inner asteroid belt.
  • HD 47536 System - Very large orange giant star with two large eccentric jovian discovered by the European-Brazilian team. The inner planet is at Earth-like distance, but is too hot for clouds to appear.
  • HD 187123 System - Template loop detected: Template:HD 187123 System
  • HD 11964 System - Sunlike star with two eccentric gas giants detected in 2005. The outermost one was retracted but then re-confirmed as one of the 28 planets announced at the May 2007 AAS media briefing. The inner most has half the mass of Saturn and is too hot for clouds. The outer one is cool and likely dominated by white water clouds. A middle planet may also exist.
  • HD 73526 System - System with two large orbit-crossing Jovians locked in 1:2 resonance that would span the inner solar system to the asteroid belt. The second planet was one of the 28 planets announced at the May 2007 AAS media briefing.
  • HD 155358 System - The extrasolar system with the lowest metalicity host star. Its two known Jovian planets were discovered recently and challenged planetary formation theorists. The two planets interact gravitationally with each other and are on opposite sides of the star's habitable zone.

One Planet Plus Systems[]

  • Errai System - Also known as Gamma Cephei, an orange sub-giant (1.4 MS, 4.8 RS, 6.6 GY) with a 1.6 MJ "Sulfurous Cloud Giant", Tadmos, in an eccentric orbet centered at 2 AU (1.8 to 2.2 AU) and a red dwarf (0.5 MS) at 20 AU (11.9 to 28.3). Located 45 ly away at the northern tip of the constellation and one of the brightest stars near Polaris and will succeed Polaris as the North Star (closer to pole in 3000 AD, and at closest in 4000 AD). It is the first close in binary star found to have a planet. The planet was first detected in 1988, and could have been the first discovered, but wasn't confirmed until 2002. Could be called the first real exoplanet detected. One of the first 20 exoplanet systems allowed to be given common names by the IAU. Named after an ancient Syrian city.
  • HD 38529 System - Subgiant star with a cloudy Hot Jupiter, Brown Dwarf, and Red Dwarf companion. Simulations showed that Earth-sized planet could exist between the planet and brown dwarf, but that an asteroid belt can be expected there instead.
  • HD 117176 System - One of the six extrasolar systems known to have planets to be first shown to also have a dust disk by Spitzer.
  • HD 52265 System - Sunlike star 90 ly away in Monoceros with a planet. Star is 1.2 the Sun's radius, 1.3 its mass, and 2.5 BY old. The star is an ideal object of study for the interactions between stars and planets. One of the six extrasolar systems known to have planets to be first shown to also have a dust disk by Spitzer. Planet independently discovered by CORALIE and Carnegie teams and is at least a 1.09 MJ Jovian in a hot eccentric orbit. By analyzing sonic vibrations, oscillations in brightness, through astroseismology, the exact internal spin rate (12 days) and orientation of the star has been computed. Assuming the planet orbits along the star's equator, it's mass can be inferred to be 1.85 Jupiter's, calming some suspicions that it may be a brown dwarf.
  • HD 50554 System - One of the six extrasolar systems known to have planets to be first shown to also have a dust disk by Spitzer.
  • Epsilon Eridani System - Ran (Epsilon Eridani) is the nearest single non-red dwarf star to the Sun, also known as HD 195019, Gl 144, and HR 1084. It is a member of the Ursa Major star association and close encounters to other stars is relatively common. One of the first stars found to have a dust disk, with several potential planets suspected in the gaps early on, and later on of the earliest nearest system with confirmed planets. Has an inner asteroid belt at 3 AU, Jovian planet AEger at 3.4 AU, outer asteroid belt at 20 AU, and Kuiper Belt at 35-100 AU. A planet is proposed to be just outside the outer asteroid belt, and another just before the Kuiper belt.Because the star is very chromospherically active, doubts were cast on planet's b's existence. Hubble then confirmed its existence with astrometrics and found to be orbiting in the plane of the dust disks, which supported the theory that planets are born from dust disks and yielded a precise mass of 1.5 MJ. The planet b was originally thought to be extremely eccentric (2-10 AU), but later discovery of the inner asteroid belt suggests it is more moderately eccentric so as not to cross the belt. It could still have high eccentricity if the outer belt was being fed with material from the outer belt though. Dinosaur-killing sized impacts would be frequent on any Earth-like planets, about once every 2 million years. One of 5 PICTURE-C targets selected for sub-orbital coronograph observation. One of the first 20 exoplanet systems allowed to be given common names by the IAU. Star is named after a Norse goddess of the seas, while the planet after her husband, god of the ocean. A common sci fi system, including the original home of Star Trek Vulcans (though this moved to 40 Eridani) and Babylon 5.
  • HD 202206 System - System with an eccentric brown-dwarf at Venus-like distances and an even further out eccentric Jovian found in 2004.