| Exoplanetary Scratchpad|
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Rank by Apparent MagnitudeEdit
Bright as the Sun:
- Solar System (-26.7; 4.83; G2V) - Our home star system. Contains 4 terrestrial planets, 4 gas giant planets, several dwarf planets, an asteroid belt, and a kuiper belt, around a G-Class yellow dwarf star. Contains the only known habitable planet, Earth.
Brighter than Magnitude 1:
- Sirius System (-1.46; 1.42; A1V) - Sirius is also known as Alpha Canis Majoris and Gliese 244. The brightest star in the sky. A hot blue-white main sequence star with a white dwarf (the "pup") orbiting it. Orbit distance varies between 8.1 and 31.5 ly and takes 50 years to navigate. The habitable zone of Star A is centered 4.25 AU from the star and may be disrupted due to the presence of Star B. Long thought to be a part of the Ursa Major Moving Group (also called the "Sirius Group"), it was found to be too young to be a member and not heading in the right direction. The brightest star within a large distance from the Sun. Star B is about the same mass as the Sun, but is almost the same size as the Earth. It may have evolved from a 5 solar massed B-type main sequence star. It is the nearest and first discovered white dwarf star. Dust has been detected from the system, probably from material sluffed off from Star B. A search in 2008 using high contrast imaging for planets within 10 Jupiter masses within 25 AU of the binary star turned up negative.
- Alpha Centauri System (-0.1; 4.38/5.71; G2V/K1V; 4.3 ly) - 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.
- Procyon System (0.34; 2.65; F5V-IV; 11.4 ly) - Procyon is also known as Alpha Canis Minoris, HD 61421, and HR 2943. Nearby Bright star system. Nearest yellow white star (F5 IV–V) to the Sun and the closest star to Sirius. It is the 7th brightest star in the sky. Has a white dwarf companion B. Has about 50% more mass than the Sun and about twice its radius. It is a BY-Draconis type of variable (unusual for a bright star) and entering the last stage of its life on the main sequence, heading towards a sub-giant, as its core seems to have exhausted its supply of Hydrogen and is starting to fuse Helium. Its habitable zone, which is 2 to 4 AU, may be disrupted by B, which is only 9 to 21 AU away. Star B was first predicted due to its effect on A's proper motion in 1844 and later spotted in 1896. It was probably about the same mass as Star A, and sterilized the system when it went into a giant phase. Luyten's Star is only 1.2 light years away, near enough to stir up any Oort clouds in either system and would be dimly visible.
- Tabit System (3.2; 3.6; F6V; 26.3 ly) - 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.
- Tau Ceti System (3.5; 5.7; G8.5V; 11.9 ly) - 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.
- Rana System (3.5; 3.8; K0 IV; 29.5 ly) - Rana is also known as Delta Eridani, HD 23249, HR 1136, and Gl 150. Nearby orange-red sub-giant star system about 30ly away. Has about 2.5 times the Sun's radius. Early estimates thought it could have 87% of the Sun's mass, but newer estimates suggest 1.2 times its mass. It is thought to have evolved from an F8 main sequence star 7.5 Billion Years ago. It will later become a true giant star. Astrometric observations suggest a companion star, but this has not been confirmed with radial velocity, perhaps because its effect would be small due to its inclination to the Sun.
- Gamma Leporis System (3.6; 3.8; F6V; 39.3 ly) - 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.
- Epsilon Eridani System (3.7; 6.2; K2V; 10.5 ly) - 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.
- Keid System (4.3; 5.9; K1V; 16.5 ly) - 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.
- Chi 1 Orionis System (4.4; 4.7; G0V; 28 ly) - 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.
- 82 G. Eridani System (4.25; 5.34; G8V; 19.7 ly) - 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.
- Kappa Ceti System (4.8; 5.16; G5V; 29.8 ly) - 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.
- BD+04°123 System (5.75; 5.88; K2V; 24.3 ly) - 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.
- BD+06°398 System (5.8; 6.5; K3V; 23.4 ly) - 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.
- BD-13°544 System (6.0; 6.0; K1V; 33.8 ly) - BD-13°544 is also known as Gl 117, HIP 13402, HR 857, and HD 17925. Nearby orange dwarf star system in Eridanus. It is part of the Beta Pictoris moving group. A strong lithium presence indicates that it must be a very young star. Since it is at about 10 parsecs away, its absolute and apparent magnitude are about the same, which is at the very limit of human detection at magnitude 6.04. Mnemonic: BD Eridani.
- BD-05°1123 System (6.2; K3V; 28.4 ly) - 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.
- BD-05°1844 System (6.6; 6.8; K3V; 28.4 ly) - 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.
- Groombridge 1618 System (6.6; K5V; 14.9 ly) - Groombridge 1618 is also known as Gl 380 and HD 88230. Nearby orange dwarf system in Ursa Major. It is an unusually bright flare star, but flares less frequently than other such stars. Its level of activity suggests it is relatively young, perhaps a little older than a Billion years. First identified in A Catalog of Circumpolar Stars by Stephen Groombridge, published posthumously in 1838. An unconfirmed planet was published in 1989 with 4 Jupiter masses at about half Earth's distance, in the inner part of the star's habitability zone. It's signal could be due to stellar activity. Its closest neighbor is a red dwarf UX UMa, which would flicker in and out of visibility due to the effects of its flares.
7th Magnitude and Dimmer:
- BD+11°878 System (8.9; 8.6; K7V; 37.1 ly) - BD+11°878 System is also known as Gliese 208, HD 245409, and HIP 26335. Nearby orange dwarf system in Orion. It is on the borderline with being a red dwarf. In 2003, a "cosmic call" was sent to this star and is expected to arrive in 2040. It may have passed within 5 ly 500,000 years ago. Mnemonic: BD Orionis 2.
- Ursa Major - Groombridge 1618 System
- Centaurus - Alpha Centauri System
- Canis Minor - Procyon System
- Monoceros - BD-05°1844 System
- Canis Major - Sirius System
- Lepus - Gamma Leporis System
- Orion - Tabit System, Chi 1 Orionis System, BD+11°878 System
- Eridanus - Rana System, Epsilon Eridani System, Keid System, 82 G. Eridani System, BD-13°544 System, BD-05°1123 System
- Cetus - Tau Ceti System, Kappa Ceti System, BD+06°398 System
- Pisces - BD+04°123 System
-  A Class + White Dwarf: Sirius System (A1)
- [3/1] Single F Class Stars: Tabit System (F6)
-  Subgiant Stars: Rana System (K0IV)
- [7/4] Single G Class Stars: Solar System (G2, planets), Kappa Ceti System (G5), 82 G. Eridani System (G8, planets), Tau Ceti System (G8.5, possible planets)
- [11/5] Single K Class Stars: BD-13°544 System (K1, BD Eridani), Epsilon Eridani System (K2, planets), BD+04°123 System (K2, BD Piscium), Groombridge 1618 System (K5), BD+11°878 System (K7, BD Orionis 2)