Wednesday, May 14, 2008

Gl 436

Star type
g M2.5

Distance from Earth
g 33 ly

Star Service No.
g NA

g About 6.5 billion years; member of the old-disk population

Radius/Mass/Temp (xSol)
g 42%; 42%; 3318 K

Brightness (xSol)
g 2.5%

g 44%

Comparison to Sol
g NA

Picture of star
g NA

Star system features
g NA

Known planets
g GJ 436b: A hot Neptune (140% Neptune mass; 2220 times Earth's mass) definitley has been located. The planet has an orbital period of 2.6 days. It's roughly 55,000 km in diameter, giving it a mass and radius similar to the ice giant planets Uranus and Neptune in our solar system. The planet is thought to be largely composed of hot ices with an outer envelope of hydrogen and helium. The planet's orbit is eccentric. Because tidal forces would tend to circularise the orbit of the planet on short timescales, this suggested that Gliese 436 b is being perturbed by an additional planet orbiting the star.
g GJ 436c: In 2008, a second planet was claimed to have been discovered, with an orbital period of 5.2 days and an orbital semimajor axis of 0.045 AU. The planet was thought to have a mass of roughly 5 Earth masses and have a radius about 1.5 times larger than the Earth's. Despite being announced in the media as being the smallest known extrasolar planet, it would still have been more massive than the three planets orbiting the pulsar PSR B1257+12, which have been known since 1992. Due to its size, the planet was thought to be a rocky, terrestrial planet. Further analysis showed that the transit length of the inner planet is not changing, a situation which rules out most possible configurations for this system. Also, if it did orbit at these parameters, the system would be the only "unstable" orbit on UA's Extrasolar Planet Interactions chart. The existence of this "Gliese 436 c" was thus regarded as unlikely, and the discovery was eventually retracted. Despite the retraction, studies have concluded that the possibility that there is an additional planet orbiting Gliese 436 remains plausible. With the aid of an unnoticed transit automatically recorded and observations by amateur astronomers, it has been suggested that there is a trend of increasing inclination of the orbit of Gliese 436 b, though this trend remains unconfirmed. This trend is compatible with a perturbation by a planet of less than 12 Earth masses on an orbit within about 0.08 AU of the star. This is still unconfirmed.
g UCF-1.01: In 2012, astronomers using NASA’s Spitzer Space Telescope have detected what they believe is a planet two-thirds (diameter would be approximately 5,200 miles) the size of Earth. Although probably rocky in composition like Earth, the world would be a terrible place for life. The world orbits scorchingly close to its star (at about seven times the distance of the Earth from the Moon, with its “year” lasting only 1.4 Earth days), so in all likelihood this planet lacks an atmosphere and might even have a molten surface (surface temperature would be more than 1,000 degrees F); if it ever had an atmosphere, it almost surely has evaporated. The world might therefore resemble a cratered, mostly geologically dead world like Mercury or it might even be covered in magma.

Habitable zone
g NA

Orbital map
g NA

View from star
g NA

Nearby stars
(Star systems with 10 light years)
g NA

Map locating star system
g NA

Location in Earth sky
g Northeast of constellation Leo's hindquarters

Other names
g Ross 905, GJ 436, LTT 13213, GCTP 2704.10, LHS 310, AC+27:28217, Vyssotsky 616, HIP 57087, GEN# +9.80120068, LP 319-75, G 121-7, LSPM J1142+2642, 1RXS J114211.9+264328, ASCC 683818, G 147-68, UCAC2 41198281, BPS BS 15625-0002, G 120-68, 2MASS J11421096+2642251, USNO-B1.0 1167-00204205, CSI+27-11394, MCC 616, VVO 171, CSI+27-11395, HIC 57087, NLTT 28288, Zkh 164, CSI+26-11395, [RHG95] 1830, GCRV 7104, LFT 838, PM 11395+2700

Sci-fi mentions
g NA

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