TESS Spots a Super-puff: The Remarkably Low Density of TOI-1420b
We present the discovery of TOI-1420b, an exceptionally low-density ( ρ = 0.08 ± 0.02 g cm −3 ) transiting planet in a P = 6.96 days orbit around a late G-dwarf star. Using transit observations from TESS, LCOGT, Observatoire Privé du Mont, Whitin, Wendelstein, OAUV, Ca l’Ou, and KeplerCam, along wit...
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Veröffentlicht in: | The Astronomical journal 2023-11, Vol.166 (5), p.181 |
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Sprache: | eng |
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Zusammenfassung: | We present the discovery of TOI-1420b, an exceptionally low-density (
ρ
= 0.08 ±
0.02
g cm
−3
) transiting planet in a
P
= 6.96 days orbit around a late G-dwarf star. Using transit observations from TESS, LCOGT, Observatoire Privé du Mont, Whitin, Wendelstein, OAUV, Ca l’Ou, and KeplerCam, along with radial velocity observations from HARPS-N and NEID, we find that the planet has a radius of
R
p
= 11.9 ± 0.3
R
⊕
and a mass of
M
p
= 25.1 ± 3.8
M
⊕
. TOI-1420b is the largest known planet with a mass less than 50
M
⊕
, indicating that it contains a sizeable envelope of hydrogen and helium. We determine TOI-1420b’s envelope mass fraction to be
f
env
=
82
−
6
+
7
%
, suggesting that runaway gas accretion occurred when its core was at most four to five times the mass of the Earth. TOI-1420b is similar to the planet WASP-107b in mass, radius, density, and orbital period, so a comparison of these two systems may help reveal the origins of close-in low-density planets. With an atmospheric scale height of 1950 km, a transmission spectroscopy metric of 580, and a predicted Rossiter–McLaughlin amplitude of about 17 m s
−1
, TOI-1420b is an excellent target for future atmospheric and dynamical characterization. |
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ISSN: | 0004-6256 1538-3881 |
DOI: | 10.3847/1538-3881/acf858 |