What exactly do we know?

 

What kind of planets have been found, and where?

 

Noteworthy Planets

"Methuselah"

Officially named PSR B1620-26c, the planet is notable being the oldest known extrasolar planet. It is believed to have been formed about 12.7 billion years ago (probably only about a billion years younger than the universe itself).

PSR B1620-26c orbits a binary pair of stars. One, the pulsar (PSR B1620-26), is a neutron star. The second is a white dwarf with a mass of 0.34 solar mass. These stars orbit each other at a distance of 1 AU about once every half year.PSR B1620-26 is located in the Messier 4 (M4 globular cluster), about 12,400 light-years away in the constellation of Scorpius.

 

51 Pegasi b

The first exoplanet observed around a main sequence star with a mass of 0.468 jupiters and a semimajor axis of 0.052 AU (close enough to become tidally locked), it is the prototypical hot jupiter.

51 Pegasi b probably has a greater radius than Jupiter despite its lower mass. This is because its superheated atmosphere must be puffed up into a thick but tenuous layer surrounding it. Beneath this, the gases that make up the planet would be so hot that the planet would glow red. Clouds of silicates may exist in the atmosphere.

 

HD 209458 b

In 1999, this was the first extrasolar planet seen transiting its parent star, conclusively proving that the radial velocity measurements suspected to be planets actually were planets.

In 2001, astronomers using the Hubble Space Telescope announced that they had detected the atmosphere of HD 209458 b. They found the spectroscopic signature of sodium in the atmosphere, but at a smaller intensity than expected, suggesting that high clouds obscure the lower atmospheric layers.

 

HD 188753 Ab

The first planet discovered in a relatively tight triple star system.

 

 

Noteworthy Systems

Epsilon Eridani

Star Data

Main Sequence Star (Orange/Yellow Dwarf)

85% Solar Mass

28% Solar Luminosity

86.5% Solar Diameter

Est. Comfort Zone: 0.540 AU

Age: 0.66 Billion Years

Notes: Star also has a Kuiper belt. Observed doppler shifts and dust depletion within 35 AU imply the presence of terrestrial planets.

 

Epsilon Eridani b

Semimajor Axis: 3.3 AU

Mass: 0.86 Jupiters

 

Epsilon Eridani c (Unconfirmed)

Semimajor Axis: ~40 AU

Mass: ~0.1 Jupiters

Notes: Marcy et al. claim that " The Doppler behavior of magnetically active stars remains poorly explored, because so few stars are as active as Epsilon Eridani. Thus, Campbell's interpretation of a planet remains controversial." - 20 oct 02: The hypothetical planet epsilon Eridani c is suspected from the dust ring morphology.

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Gliese 876

Star Data

Red dwarf star

32% Solar Mass

1.24% Solar Luminosity (largely infrared)

36% Solar Diameter

 

 

Age: 6.5 - 9.9 Billion Years

Aqueous Zone: 0.116-0.227 AU

 

Gliese 876d

Semimajor Axis: 0.0208 AU

Mass: 0.0185 Jupiters (7.5 Earths)

Notes: Terrestrial? One model predicts a watery ocean with an oxygen/water vapour atmosphere.

 

Gliese 876c

Semimajor Axis: 0.1303 AU

Mass: 0.619 Jupiters

Notes: Gas Giant? Predicted to have a cloudless upper atmosphere.

 

Gliese 876b

Semimajor Axis: 0.208 AU

Mass: 1.93 Jupiters

Notes: Gas Giant? Predicted to be largely cloudless, perhaps with water clouds in cooler regions.

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Upsilon Andromedae

Binary Star System

Upsilon Andromedae A

Yellow/White Dwarf

128% Solar Mass

340% Solar Luminosity

173% Solar Diameter

Est. Comfort Zone: 1.91 AU

Age: 3.3 Billion Years

 

Upsilon Andromedae Ab

Semimajor Axis: 0.0595 AU

Mass: 0.687 Jupiters

Notes: Gas Giant? Predicted to have clouds of iron and silicate in it's upper atmosphere.

 

Upsilon Andromedae c

Semimajor Axis: 0.830 AU

Mass: 1.97 Jupiters

Notes:Gas Giant? Predicted to be cloudless.

 

Upsilon Andromedae d

Semimajor Axis: 2.54 AU

Mass: 3.93 Jupiters

Notes: Gas Giant? Predicted to have water clouds

 

Upsilon Andromedae B

Red Dwarf Star

Semimajor Axis: 750 AU

20% Solar Mass

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55 Cancri

Binary Star System

55 Cancri A

Yellow Dwarf Star

0.95 Solar Mass

0.61 Solar Luminosity

91% Solar Diameter

Est. Comfort Zone: 0.76 AU

Age: 5.5 Billion Years

Notes: The star is surrounded by a dust disk extending at least a 40 AU, with an inclination of ~ 25o. If the planets are in the same plane than the disc, this gives to the forst planet a mas of 1.9+1.1 -0.4 MJ (Trilling & Brown 1998, Trilling et al 2000). But disc not confirmed by Schneider et al (2000b). There may by a hole with a radius of ~ 10 AU in the disk (Jayawardhana et al 2000)

 

55 Cancri e

Semimajor Axis: 0.038 AU

Mass: 0.045 Jupiters

Notes: Large terrestrial planet? (Chthonian planet?)

 

55 Cancri b

Semimajor Axis: 0.115 AU

Mass: 0.0784 Jupiters

Notes: Predicted to have a cloudless upper atmosphere with strong alkali metal absorbtion lines. Unlikely to have large moons due to tidal forces.

 

55 Cancri c

Semimajor Axis: 0.24 AU

Mass: 0.217 Jupiters

Notes: Gas giant?

 

55 Cancri d

Semimajor Axis: 5.257 AU

Mass: 3.92 Jupiters

Notes: Probably a gas giant with water clouds -- temperature is likely to be too high for ammonia clouds.

 

Rho Cancri B

Red Dwarf Star

0.13 Solar Mass

0.0076 Solar Luminosity

30% Solar Diameter

Semimajor Axis: ~1150 AU

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HD 69830

Star Data

Orange Dwarf

86% Solar Mass

60% Solar Luminosity

96% Solar Diameter

Est. Comfort Zone: 0.753 AU

Age: 7 Billion Years

Notes: System has an extensive asteroid belt (20x more massive than ours). Star emits extensive amounts of IR.

 

HD 69830 b

Semimajor Axis: 0.075 AU

Mass: 0.033 Jupiters

Notes:

 

HD 69830 c

Semimajor Axis: 0.186 AU

Mass: 0.038

Notes:

 

HD 69830 d

Semimajor Axis: 0.63

Mass: 0.058

Notes: Planet is in the inner Habitable Zone?

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Mu Arae (HD 160691)

Yellow/Orange Dwarf

108% Solar Mass

177% Solar Luminosity

143% Solar Diameter

Est. Comfort Zone: 1.34 AU

Age: 6 Billion Years

Notes:

 

Mu Arae d

Semimajor Axis: 0.09 AU

Mass: 0.044 Jupiters (~14 Earths)

Notes: Probably a terrestrial planet.

 

Mu Arae b

Semimajor Axis: 1.5 AU

Mass: 1.67 AU

Notes:

 

Mu Arae c

Semimajor Axis: 4.17 AU

Mass: 3.1 Jupiters

Notes:

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HD 37124

Yellow Dwarf Star

82% Solar Luminosity

Est Comfort Zone: 0.91 AU

 

HD 37124 b

Semimajor Axis: 0.53 AU

Mass: 0.61 Jupiters

Notes: Probable Gas Giant

 

HD 37124 c

Semimajor Axis: 1.64 AU

Mass: 0.6 Jupiters

Notes: Probable Gas Giant

 

HD 37124 d

Semimajor Axis: 3.19 AU

Mass: 0.66 Jupiters

Notes: Probable Gas Giant

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Iota Draconis (Edasich)

Orange Giant Star

 

105% Solar Mass

?% Solar Luminosity

1101% Solar Diameter

Est. Comfort Zone: 3.96-12.36 AU

Age: 0.66 Billion Years

 

HD Iota Draconis b

Semimajor Axis: 1.34 AU

Mass: >8.82 Jupiters

Notes:

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47 Ursae Majoris

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2M1207

Brown Dwarf Star

~21 Jupiter Masses

Minor Luminosity

 

2M1207b

Mass: 3.3 Jupiter Masses

Semimajor axis: ~41 AU

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PSR B1257+12

Pulsar

~ 140% Solar Mass

Unknown Luminosity

~ 0.0002% Solar Radius

Notes: Discovered in 1990 and publicised in 1992, these were the first exoplanets ever verified. They are still considered highly unusual in that they orbit a pulsar.

 

PSR B1257+12 A

Semimajor Axis: 0.19 AU

Mass: 0.02 Earths

Notes:

 

PSR B1257+12 B

Semimajor Axis: 0.36 AU

Mass: 4.3 Earths

Notes:

 

PSR B1257+12 C

Semimajor Axis: 0.46 AU

Mass: 3.9 Earths

Notes:

 

PSR B1257+12 D

Semimajor Axis: 2.6 AU

Mass: 0.0004 Earths (0.2 Plutos)

Notes: Arguably the first extrasolar comet observed.

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Ref: Extrasolar Planet Encyclopedia