Kappa Andromedae b
| Exoplanet | List of exoplanets | |
|---|---|---|
 |
||
| Parent star | ||
| Constellation | Andromeda | |
| Right ascension | (α) | 23h 40m 24.50763s |
| Declination | (δ) | +44° 20′ 02.1566″ |
| Apparent magnitude | (mV) | 4.139 |
| Spectral type | B9 IVn | |
| Mass | (m) |
2.8+0.1 −0.2 M☉ |
| Radius | (r) | 2.31 (± 0.09) R☉ |
| Temperature | (T) | 11,361 (± 66) K |
| Age |
0.03+0.12 −0.01 Gyr |
|
| Physical characteristics | ||
| Mass | (m) |
14+25 −2 MJ |
| Radius | (r) |
1.2+0.2 −0.1 RJ |
| Other designations | ||
Kappa Andromedae b is a substellar object and massive planet or brown dwarf orbiting Kappa Andromedae, a star in the Andromeda constellation, about 170 light years away. The object, nearly 13 times the mass of Jupiter, was directly photographed by the Subaru Telescope. There has been considerable debate as to whether Kappa Andromedae b is an exoplanet or a brown dwarf; and, until the question can be clarified, scientists have dubbed it the "Super-Jupiter" object.
Through the Strategic Explorations of Exoplanets and Disks with Subaru (SEEDS) survey, the Subaru Telescope, located atop Mauna Kea, Hawaii, astronomers were able to photograph Kappa Andromedae b by taking a near-infrared photograph of the parent star and processing it to reduce its light. Between January and July 2012, Subaru observed Kappa Andromedae using four separate infrared wavelengths, and when comparing photographs from January and July, the team of astronomers was able to determine that Kappa Andromedae and Kappa Andromedae b were gravitationally bound.
Through those photographs and other research by the Subaru team, a few details about the "Super-Jupiter" object have been revealed. The object's mass has been calculated as approximately 12.8 times Jupiter's mass, the host star's mass as 2.4 to 2.5 solar masses. The temperature of the object is estimated to be around 1700 kelvin, and, if seen up close, would appear reddish in color. The object's distance from its parent star is about 1.8 times Neptune's distance from the Sun.
It is unclear whether Kappa Andromedae b is a gas giant or a brown dwarf—that is, an object massive enough to fuse deuterium but not protium. Conventional planetary formation models dictate that the lowest expected mass for a brown dwarf is around 13 times that of Jupiter. Kappa Andromedae b has a mass of about 12.8 times that of Jupiter, apparently too small to fuse deuterium in its core; however, according to NASA discovery team member Michael McElwain, "this isn't definitive, and other considerations could nudge the object across the line into brown dwarf territory." Analysis of the object's brightness reveals infrared colors similar to those found for other massive imaged planets like Beta Pictoris b, further suggesting that Kappa Andromedae b could be a planet rather than a more massive brown dwarf.
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Wikipedia