Name the hottest giant planet that was discovered recently by astronomers.
A) KELT-9b
B) TRAPPIST-1
C) HAT-P-38b
D) OGLE-2017-BLG
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KELT-9b is the hottest gas giant exoplanetknown, with a dayside temperature of between 4,050 and 4,600 K(surface temperature tops 3780 degree celsius), which makes it hotter than M-type stars, and many K-type stars.[1] It orbits HD 195689 (or KELT-9), a late B-type main sequence star about 620 light-years (190 parsecs) from Earth.
KELT-9b
Artist's impression of KELT-9b and its parent star
Orbital characteristics
Semi-major axis
0.03462+0.00110
−0.00093 AU
Orbital period
1.4811235±0.0000011[1]dInclination86.79±0.25[1]StarKELT-9Physical characteristics
Mean radius
1.891+0.061
−0.053[1] RJMass2.88±0.84[1] MJ
Mean density
530±0.15 kg m−3Temperature4050±180[1] K
The host star has a temperature of 10,170 K, which is remarkable, as transiting planets are not usually detected in orbit of hot stars; as a reference, only six A-type stars were known to have planets prior to KELT-9b discovery (WASP-33, an A-type star with a temperature of 7,430 K being the hottest at the moment of the discovery of KELT-9b), and no B-type stars were known (hotter than A-type stars); KELT-9, classified as B9.5-A0[1] or A1,[2] is the first B-type star (or, at least, almost B-type) in which a planet has been discovered.
KELT-9b was detected using the Kilodegree Extremely Little Telescope and the results of its unusual nature were published in 2017.[3][1]
The planet was found to have a largely extended hydrogen atmosphere.[4] The size of the atmosphere is close to the planetary Roche lobe, which implies the planetary atmosphere is escaping at a high mass loss rate. The discovery was made by probing the Balmer Hα line absorption when the planet is transiting in front of its host star.
It is tidally locked.
The atmosphere of the planet is so hot that refractory elements that would usually be sequestered into molecules can exist as atomic species, including neutral and singly ionized atomic iron (Fe and Fe+) and singly ionized titanium (Ti+).
KELT-9b has surprised astronomers yet again with the discovery that its atmosphere contains the metals iron and titanium.
KELT-9b
Artist's impression of KELT-9b and its parent star
Orbital characteristics
Semi-major axis
0.03462+0.00110
−0.00093 AU
Orbital period
1.4811235±0.0000011[1]dInclination86.79±0.25[1]StarKELT-9Physical characteristics
Mean radius
1.891+0.061
−0.053[1] RJMass2.88±0.84[1] MJ
Mean density
530±0.15 kg m−3Temperature4050±180[1] K
The host star has a temperature of 10,170 K, which is remarkable, as transiting planets are not usually detected in orbit of hot stars; as a reference, only six A-type stars were known to have planets prior to KELT-9b discovery (WASP-33, an A-type star with a temperature of 7,430 K being the hottest at the moment of the discovery of KELT-9b), and no B-type stars were known (hotter than A-type stars); KELT-9, classified as B9.5-A0[1] or A1,[2] is the first B-type star (or, at least, almost B-type) in which a planet has been discovered.
KELT-9b was detected using the Kilodegree Extremely Little Telescope and the results of its unusual nature were published in 2017.[3][1]
The planet was found to have a largely extended hydrogen atmosphere.[4] The size of the atmosphere is close to the planetary Roche lobe, which implies the planetary atmosphere is escaping at a high mass loss rate. The discovery was made by probing the Balmer Hα line absorption when the planet is transiting in front of its host star.
It is tidally locked.
The atmosphere of the planet is so hot that refractory elements that would usually be sequestered into molecules can exist as atomic species, including neutral and singly ionized atomic iron (Fe and Fe+) and singly ionized titanium (Ti+).
KELT-9b has surprised astronomers yet again with the discovery that its atmosphere contains the metals iron and titanium.
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