by johnnydeep » Tue Aug 18, 2020 3:49 pm
BDanielMayfield wrote: ↑Tue Aug 18, 2020 1:35 pm
The system orbiting TYC 8998-760-1 is very different than ours.
There are two giant exoplanets orbiting the star. The ESO Very Large Telescope photographed the two planets using its SPHERE instrument, producing the first direct image of multiple planets orbiting a Sun-like star.[1][6]
TYC 8998-760-1 b has a mass 14 times that of Jupiter, and a radius of 3 RJ. It orbits at a distance of 162 AU (2.42×1010 km; 1.51×1010 mi), or slightly more than 5 times the Neptune-Sun distance.[5][7]
TYC 8998-760-1 c has a mass of 6 MJ, and orbits at 320 AU (4.8×1010 km; 3.0×1010 mi), or slightly more than 11 times the Neptune-Sun distance.[5]
The object labeled b might not even be a true planet. It is over the 13 Jupiter lower mass limit for brown dwarfs.
A brown dwarf is a type of substellar object that has a mass between those of the heaviest gas giant planets and the least massive stars, i.e. about 13 to 75–80 times that of Jupiter (MJ),[1][2] or about 2.5×1028 kg to 1.5×1029 kg. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the red dwarfs. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.[3]
Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores. They are, however, thought to fuse deuterium (2H). If their mass is > 65 MJ they may also fuse fuse lithium (7Li).[2] It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their nuclear fusion reactions.[4]
The whole subject of sub stellar mass objects is extremely interesting to me. Heck, it's ALL interesting: the range of planet-like objects, the range of star-like objects, and stellar evolution. Hmm - you never hear much about
planetary evolution. Why not? I guess because we only have 8 or so examples to study, and those are all "stuck" in time at about 4.5 billion years old.
[quote=BDanielMayfield post_id=305272 time=1597757724 user_id=139536]
The system orbiting TYC 8998-760-1 is very different than ours.
[quote]There are two giant exoplanets orbiting the star. The ESO Very Large Telescope photographed the two planets using its SPHERE instrument, producing the first direct image of multiple planets orbiting a Sun-like star.[1][6]
TYC 8998-760-1 b has a mass 14 times that of Jupiter, and a radius of 3 RJ. It orbits at a distance of 162 AU (2.42×1010 km; 1.51×1010 mi), or slightly more than 5 times the Neptune-Sun distance.[5][7]
TYC 8998-760-1 c has a mass of 6 MJ, and orbits at 320 AU (4.8×1010 km; 3.0×1010 mi), or slightly more than 11 times the Neptune-Sun distance.[5][/quote]
The object labeled b might not even be a true planet. It is over the 13 Jupiter lower mass limit for brown dwarfs.
[quote]A [b]brown dwarf[/b] is a type of substellar object that has a mass between those of the heaviest gas giant planets and the least massive stars, i.e. about 13 to 75–80 times that of Jupiter (MJ),[1][2] or about 2.5×1028 kg to 1.5×1029 kg. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the red dwarfs. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.[3]
Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores. They are, however, thought to fuse deuterium (2H). If their mass is > 65 MJ they may also fuse fuse lithium (7Li).[2] It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their nuclear fusion reactions.[4][/quote]
[/quote]
The whole subject of sub stellar mass objects is extremely interesting to me. Heck, it's ALL interesting: the range of planet-like objects, the range of star-like objects, and stellar evolution. Hmm - you never hear much about [b]planetary [/b]evolution. Why not? I guess because we only have 8 or so examples to study, and those are all "stuck" in time at about 4.5 billion years old.