| Exoplanetary Scratchpad|
Encyclopedia of Suns Web PagesEdit
List of Stars (By Distance)Edit
- Alpha Centauri System - Alpha Centauri is also known as Rigil Kentaurus. A is also known as HD 128620 and HR 5459, B is HD 128621 and HR 5460, and C is Proxima Centauri. It is the nearest star system to the Sun. Contains a yellow dwarf star a little bigger than the Sun and an orange star a little smaller orbiting each other orbiting each other about the distance Uranus is from the Sun (varies from Saturn like to Neptune like), as well as a distant Red Dwarf companion Proxima that may or may not be orbiting the other two.
Stellar fingerprinting suggests a high probability that a planet orbits star A, due to dearth of Iron around star. Russian astronomers announced the detection of a second planet orbiting the binary pair at 80 AU with a 100 year period, which appears to be false. The stars in the system will become markedly closer together in 2016, making observations much more difficult and one follow up failed to find it. The system is the first target for the European Cheops exoplanet space telescope.
First planet discovered is an Earth-massed rocky-iron planet with no atmosphere at epistellar distances around the orange dwarf star B found by HARPS. This is the least massive planet found around a sunlike star. The planet was informally and controversially named by Uwingu during a fund raising naming contest Albertus Alauda, after a participant's grandfather. Earthlike planets are not detectable in the habitable zone with present radial velocity methods. Technique for detection of planet is a source of doubt for some and it has yet to be independently verified. A team thought they might have detected a transit of this planet, but further observations showed the timing wasn't consistent. It is possible that a second further out (20.4 day period) Earth-sized planet is altering the transit times of the first. A cheap crowdfunded satellite devoted to studying this star could confirm the planets. The star was observed to be a good candidate to host a "super Habitable" planet, which would have 25% more gravity than the Earth, shallow seas, flatter landscape, higher atmospheric pressure, and the 6 BYO star would be stable for life longer.
Proxima, a small flare star, was discovered in 1915 by Robert Ines, who named it. Long suspected planet around Proxima found not to exist. The Pale Red Dot project is dedicated to finding a planet around Proxima using dopplar spectrometry. As Proxima passes in front of two stars (once in 2014, again in 2016), any planets within 5 AU should be detectable via microlensing using the HST. It is known that no planets of Neptune sized mass exist within 1 AU and no Jovians with periods up to 1000 days, or transiting planets exist. An Earth-like planet in the habitable zone was discovered around Proxima Centauri. In 2017, a large stellar flare erupted and bombarded the planet, making it likely that the atmosphere has been completely stripped away by events such as this and not a good candidate for life. It was thought that a lot of dust existed in the system, making it feasable that the star had a rich complement of planets, but this seems to not be the case.
- 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.
- Epsilon Indi System - Epsilon Indi is the also known as HR 8387, Gl 845, and HD 209100. Second nearest single sunlike star to the Sun. Orange dwarf with a binary brown dwarf orbiting it. The smaller of the two is the closest thing to an "extrasolar moon" found so far. The constellation "Indus" first appeared in 1603 in the Uranometria. Epsilon Indi appeared as one of the Indian's arrows in Bode's 1801 atlas, the Uranographia. The star's high proper motion was first discovered by Gill in 1882, which was improved upon by Shapley in 1923. During 1960, the star was observed for radio signals, but none was found. In 1972, it was searched for ultraviolet laser signals. It leads a Carnegie list of stars most likely to have an earth-like planet. The star's age has been controversial, at first thought to be older than the sun, then younger, then even older than originally thought, all based on studies regarding the brown dwarf's nature and the rotation rate of the star.
- Tau Ceti System - Tau Ceti is also known as HD 10700, HR 509, and Gl 71. The nearest single G-class yellow dwarf to the sun, somewhat smaller than the Sun. A popular science fiction subject and one of two targets of SETI-forerunner Project Ozma in the 1960s. Despite being somewhat older than the sun, it has an extensive asteroid and/or comet field 10-50 AU, with the bulk between 35 and 50 AU. It has about ten times as much material as the Sun. This would make life difficult. It is a metal deficient star, so it is thought less likely to host rocky planets. Traditional dopplar spectrometry has ruled out any large Jupiter sized planets at Jupiter like distances or closer in, which was thought to be good for any potentially habitable planets. Five candidate rocky super Earth planets were detected though using a new method of planetary detection. This method made predictions of the stellar "noise" activity that might obscure detection of a planet based on the long history of dopplar measurements done on this system. Deviations from this prediction pointed towards the existence of planets. Confirmation using more established methods is needed. These planets are labeled b through f as you go outward, span 0.1 AU to 1.35 AU, and get larger the further you go out (at least 2 ME to 6.6 ME). The outermost two are near the habitable zone and were originally hailed as possibly being the nearest and smallest known habitable planets. More recent modeling indicates they are not actually habitable though. Planet e is probably too close to the star and only in the HZ if generous assumptions are made. Planet f has probably only been in the habitable zone for about a billion years as a result of its star becoming hotter, which might make biosigns difficult to detect from Earth, considering it took 2 BY for biosigns to become detectable around the Earth. Since the star has a higher magnesium to silicon ratio than the Sun, these planets compositions could be quite different that the Solar System's. The lower mantles could be dominated with ferropericlase, which is not very viscious, which may make the rocks of the mantle flow easier than on Earth, affecting volcanism and tectonics. One of 5 PICTURE-C targets selected for sub-orbital coronograph observation.
15 Light YearsEdit
- Omicron 2 Eridani System - Kied is also known as 40 Eridani, Omicron 2 Eri, and Gl 166. Triple star which is Gene Roddenberry's favored location for Spock's home planet of Vulcan. Consists of an Orange Dwarf primary A (also called HD 26965 and HR 1325) with a flare star Red Dwarf C (also called DY Eridani) orbiting 50 AU away, and a much further White Dwarf B at 600 AU. The white star would appear two orders of magnitude brighter than Venus does from any planets in AC, so it would be visible in the daylight. While no planet has been discovered in this system yet, it has been selected as a target for the SIM Planet quest when launched in 2015 for signs of a habitable planet. The White Dwarf is by far the easiest White Dwarf to observe, as it is brighter than the closer Van Manaan's Star and is not swamped by the light of a bright primary like those found in the Sirius or Procyon systems.
- 70 Ophiuchi System - 70 Ophiuchi is also known as GJ 702 and HD 165341. It is a nearby pair of orange dwarves, easily visible with the naked eye when away from city lights. Star A is a DY Draconis variable star and is also known as HR 6752. It was first cataloged by William Herschel in the late 18th century during his study of binary stars, who claimed Father Meyor noticed its duplicity earlier (whose other claims could not be verified by contemporaries). He proved the two stars went around each other, an important verification of Newton's laws. He suspected another object was affecting the orbits of the two stars. Other astronomers claimed this could be a planet, such as Captain Jacob in 1855, which is one of the first claims for a planet using astrometric data. See also made a claim in 1899, but Moulton soon published a paper showing that this system would be unstable. In 1943, Reuyl again caused a sensation by claiming planets, only to be refuted again. The two stars follow an eccentric orbit ranging from 11.7 to 34.8 AU away. Star A has about 92% of the Sun's mass. The stars are thought to be 1.5 Billion Years old.
- Sigma Draconis System - Alsafi is also known as Sigma Draconis, HR 7462, Gl 764, and HD 185144. It's name is from derived from Arabic for a "cooking tripod" that nomads used. It has been reclassified in 2003 as a G9 Yellow Dwarf star (it was thought to be an orange dwarf). It has about 90% of the Sun's mass and 80% of its diameter. There appears to be a sunspot cycle, though its length is undetermined, and it was found to be the least variable of any of the stars observed by Hipparcos. It is thought to be 7 to 8 Billion Years old. It was a tier 1 target for Nasa's Terrestrial Planet Finder and a top target for ESA's Darwin project before both projects were put on indefinite hold. It was described as being the fourth easiest star to find terrestrial planets. No indication of any planets or dust disks have so far been detected. One of 5 PICTURE-C targets selected for sub-orbital coronograph observation.
- Gliese 570 System - Nearby star system.
- Eta Cassiopeiae System - Archird is also known as Eta Cassiopeiae and Gliese 34. Nearby yellow dwarf star (A) orbited by an orange dwarf star (B). It is the brightest star near the lines formed by the "W" of the constellation. Star A is also known as HR 219, LHS 123, and HD 4614, while Star B is also known as LHS 122. Star A is about the same size, mass, and age as the Sun, but only about 65% as metal rich. It represents what the Sun might look like from Archird. Its habitable zone is centered on 1.35 AU. At one time, Star A was thought to have a spectroscopic binary companion with a nine day orbit period. Star B may have first been discovered by William Hershel in 1779 two years prior to discovering Uranus, while he was seeking nearby double stars for parallax studies. Star B ranges from 36 to 107 AU. It has 56% of the Sun's mass and 66% it diameter, but only 3% its luminosity. Radial velocity variations have been detected, though no planet has been announced at this time. The system is a top tier target for TPF. In Star Trek, this is home to Terra Nova.
- 36 Ophiuchi System - 36 Ophiuchi is also known as Gl 663. A nearby triple orange dwarf star system. Stars A and B have extremely eccentric orbits and their distance varies from 7 to 169 AU and are bright K0/K1 stars. Star A is also called HR 6402 and 155886, while Star B is also called HR 6401 and HD 155885. Limits have been placed on planets in this system and orbits beyond 1.5 AU may not be possible. Gliese Star C lies 5,000 AU away and is a dimmer star. It is also known as Gl 663C and Gl 664 and HD 156026. It is a RS CVn type variable star designated V2215 Oph. The system is relatively young at 1 to 1.8 Billion Years old and A is sometimes listed as a pre-main sequence star.
- Gliese 783 System - J. Herschel 5173 is also known as Gl 783, HD 191408, HR 7703, CD-36°13940, DM-36°13940, and 279 G. Sagittarii. Nearby orange dwarf star with a red dwarf companion, currently separated by 43 AU. Herschel first published it as a binary star. It is heading towards the Sun and will be 6.7 ly away (compared to its current 19.9 ly) in 40,000 and will be 10 times as bright. It could be a member of the Old Disk, which implies an age of up to 10 Billion Years old, though rotational analysis suggests 6.4 to 7.7 BY. It is a tier 1 priority for searching for planetary companions by SIM. Has two optical companions which are not optically bound, which are themselves binaries, Gl 783.1 AB Gl 738.2 AB.
- 82 G. Eridani System - 82 G. Eridani is also known as 82 Eri, HR 1008, Gl 139, and HD 20794. One of the nearest star systems with planets. It is one of the dimmer yellow dwarf stars. Has three radial velocity detected super Earth planets orbiting closer than the habitable zone. The outermost one d is the largest (5 times Earth's mass, twice its radius, rocky-water composition) is about the same distance as Mercury is from the Sun. The middle one c is 0.1 au closer and is the smallest (2.5 Earth's mass, 1.5 its radius) and is likely a rocky-iron in composition. The innermost one is at 0.1 AU and just slightly larger than c, but more massive and of a more rocky-water composition. A dust disk was also found about 20AU from the star. The 2007 book "Habitable Planets for Man", released prior to the discovery of the planetary system, placed this as the most habitable star system within reach of mankind.
- Delta Pavonis System - Delta Pavonis is also known as Gl 780, HD 190248, and HR 7665. One of the nearest bright stars to the sun. Although somewhat smaller than the Sun, it is easily visible with the naked eye. It is about 6.8 Billion Years old. It has a New Suspected Variable designation NSV 12790 and appears unusually bright for a main sequence star, so may be starting to become a sub-giant. It was identified as the best SETI target of the nearest 100 G-type stars. It is the nearest solar-analog in a single system and is type G5-8 V-IV.
20 Light YearsEdit
- Gliese 892 System - BD+56°2966 is also known as Gl 892, HR 8832, and HD 219134. Nearby orange dwarf star and flare star. Its habitable zone is centered at 0.46 AU. It was a top tier target for the Terrestrial Planet Finder and Darwin missions. It might have a red dwarf companion.
- Xi Bootis System - Nearby binary star system, including a yellow and an orange dwarf star.
- Gliese 667 System - MLO 4 is most commonly known as Gliese 667 and also known as HR 6426 and HD 156384. A triple star system 23 light years away that contains planets in Scorpius. It was first cataloged as a binary star by astronomers at the old Melbourne Observatory (MLO) in Australia in 1867, so it was cataloged as MLO 4. It consisting of binary of orange dwarf stars about 12 AU apart (ranging from 5 to 20 AU), around which a distant red Dwarf C orbits (ranging from 56 to 215 AU). Star C is a dynamically packed planetary system, with at up to 7 unconfirmed super-Earth planets. The system became the nearest multistar system with planets when planet b (innermost, largest), a temperate super Earth planet (5.7 ME, 0.05 AU) was discovered, and is at the very inner edge of the most generous habitable zone. It became the poster child for an announcement of 32 exoplanets discovered by European astronomers working on the HARPs project and brought the total number of exoplanets to near 400. Planet c was later discovered near the inner edge of least generous habitable zone and is about the same size, and receives the same amount of stellar energy as the Earth. It was calculated that it likely no longer has a magnetic field that could protect its oceans from stellar radiation. Planets f and e were confirmed and also orbit in the Hz further out. Planet d is just beyond he HZ. Outermost planet, g (2.4 ME) is likely a frozen planet and the only one beyond Mercury-like distances. The multi-planet solution is somewhat lax and complicated and may need further confirmation. An even more unconfirmed planet h may be between b and c. A fourth stellar companion D is not gravitationally bound to the system.
- Gliese 105 System - BD+06°398 is also known as HR 753, HD 16160, and Gl 105. It is a triple star system comprising of an orange dwarf (A) and two red dwarf (B, C). Star A lies at the minimum mass needed for core fusion of Hydrogen. It's habitable zone would be centered at Mercury-like distances. B lies 1,200 AU away, and is a flare star and a BY Draconis variable star also known as BX Ceti. C is an extremely faint Red Dwarf and only about the size of Jupiter and is separated from A by 24 AU, but likely has extreme eccentricity (0.75). It is near the lower mass limit needed to sustain nuclear fusion. Hubble confirmed its existance in 1995. Mnemonic: BD Ceti.
- Gliese 33 System - BD+04°123 is also called HR 222, Gl 33, HD 4628, and 96 G. Piscium. A relatively bright and nearby orange dwarf system visible to the naked eye. Mnemonic: BD Piscium.
- 107 Piscium System - 107 Piscium System
25 Light YearsEdit
- Pi3 Orionis System - Tabit is also known as Pi3 Ori, Gl 178, HD 30652, and, HR 1543,. Nearby Yellow-White Main Sequence star. It is type F6, has about 1.3 times the Sun's mass, and the same amount of its radius. It has a stable spectrum, which is used to compare with other stars. It is the brightest star in Orion's "shield" or "lion". It has a companion star that may be visual or optical. It is now 26.2 ly away, but came within 15 ly 210,000 years ago.
- P Eridani System - p Eridani is also known as Gl 66 and Dunlop 5. Nearby binary orange dwarf star. A is also known as HR 487 and HD 10361, while B is called HR 486 and HD 10360. It was found to be a double in 1825 by Dunlop. It's possible that star B has a spectroscopic companion as suspected in the 1960s.
- Beta Canum Venaticorum System - Chara is also known as Beta Canum Venaticorum, Asterion, HR 4785, Gl 475, and HD 109358. Together with Cor Caroli, it forms the "Southern Dog" portion of the Hunting Dogs constellation. Its name Chara (Greek for "joy") used to apply to both stars, but is now only applied to this one. Nearby yellow dwarf star and Solar analog. It is slightly older than the Sun and rotates at a similar speed as the Sun. X-Rays have been detected, as would be expected. It was named in 2003 to be the most likely sun-like star old enough to produce a radio-wave producing civilization. An unconfirmed spectroscopic companion star with a 2,430 day period has been claimed.
- 61 Virginis System - A system containing a 5.1 ME Hot Super-Earth b (which is hot enough to have emissions on its night side) and one and possibly two other further out Neptunians (c and d [unconfirmed] and possibly a fourth), and a massive Kuiper Belt around a very Sun-like star only 28 light years away. All planets would fit inside Venus' orbit and have high eccentricities, especially the outermost one. This is the closest planetary system around a G-type star, which is one of the only very sun-like stars visible to the naked eye. It is the first non-borderline G-class main sequence star found to have a super-Earth. A lack of a Jovian planet and an unseen further out Neptunian may explain the large amount of cometary debris detected. Systems like this may avoid a heavy bombardment period, but instead undergo a steady rain of occasional cometary impacts for billions of year. Of the six sunlike stars within 10 parsecs, this star would be the one most likely to have an older version of Earth orbiting it. This postulated planet would have only microbes left as its star became hotter.
- Zeta Tucanae System - Zeta Tuc is also known as HR 77, Gl 17, and HD 1581. Nearby star system. It is a nearby yellowish star with a late F or early G spectrum. It may have an unseen spectroscopic binary partner. It is slightly less massive, slightly larger, and slightly brighter than the Sun and only 44 to 79% its metalicity. It is one of the least variable stars observed during the Hipparcos mission. Its similarity to the Sun make it an interesting target. It is about 3 Billion Years old. It is thought to have a debris disk. Its rotational velocity appears to be almost zero, indicating it presents its pole towards us, which would make finding planets through radial velocity nearly impossible.
- Chi 1 Orionis System - Chi 1 Orionis is also called Gl 222, HR 2047, and HD 39587. Nearby binary star system. A yellow dwarf star somewhat brighter than the Sun and a red dwarf. Because the red dwarf orbits 3.3 to 8.9 AU, the chances of a habitable planet are low. A member of the Ursa Major Moving Group. There is a theory that this star may have once been in a star system that includes HD 147513 A and B (which have a planet), which is part of the same moving group. When HD 147513 B went on to become a White Dwarf, material was sluffed off onto Chi 1 Orionis A, enriching it and causing it to become a "Barium Dwarf". Gravitational instabilities caused Chi 1 Orionis and HD 147513 systems to separate.
- Gliese 250 System - BD-05°1844 is also known as Gl 250 and HD 50281. Nearby double star consisting of an orange dwarf (A) and a red dwarf (B) in Monoceros. The stars are separated by about 500 light years. Mnemonic: BD Monoceros.
- Gliese 666 System - Gliese 666 System
- Gliese 183 System - BD-05°1123 is also known as Gl 183 and HR 1614. It is a nearby orange dwarf star system in Eridanus. It is the title member of the 2 Billion Year Old HR 1614 Moving Group. It is a spectroscopic binary, although no data is available on its companion star. Mnemonic: BD Eridani 2.
- Gliese 785 System - CD-27°14659 is most commonly referred to as Gliese 785 and also known as HR 7722 and HD 192310. It is a relatively bright orange dwarf star in Capricorn with planets. It is a chromospherically inactive star with a slow rotation (48 days) and old age of 8 billion years. It is a suspected variable CSV 101960 and NSV 12933 Planet b is a Neptunian with a mildly eccentric orbit near the inner edge of the habitable zone (period is 74 days, distance 0.32 AU). Planet c is somewhat larger and orbiting near the outer edge of the habitable zone at 1.18 AU (528 days).
- Gamma Leporis System - Gamma Leporis is also known as Gl 216, HR 1983, and HD 38393. It is a double or triple star system, including a yellow white main sequence star A, a distant orange dwarf companion B at 864 AU. A distant star may or may not be gravitationally bound. This is sometimes called star C, or LTT 2368, or VB 1 (Van Biesbroeck 1). The star system may be 2.7 Billion Years old and is a member of the Sirius group. A has 1.2 times the Sun's mass and 1.3 its diameter. B has 63% of its mass, but about the same diameter. It is a BY Draconis variable star known as AK Leporis. The star is one of the top 100 target stars for the Terrestrial Planet finder mission.
- Beta Coma Berenices System - Beta Coma Berenices System
- Kappa Ceti System - Kappa Ceti is also known as Kappa 1 Ceti, HD 20630, HR 996, and Gl 137. Nearby yellow dwarf star system. Kappa 2 Ceti is nearby it in the sky, but is a giant yellow star ten times as far away. Kappa Ceti has similar mass and size as the Sun, but is cooler and less bright. It is much younger than the Sun, at 800 Million Years old. It may emit superflares, which may make life impossible on any otherwise inhabitable worlds. Past spectroscopic studies suggested a partner star, but this has not been confirmed with radial velocity studies.
30 Light YearsEdit