Home Earth and Planetary Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b

# [1812.02214] Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b

(Submitted on 5 Dec 2018)

Abstract: The helium absorption triplet at a wavelength of 10,833 Å has been
proposed as a way to probe the escaping atmospheres of exoplanets. Recently
this feature was detected for the first time using Hubble Space Telescope (HST)
WFC3 observations of the hot Jupiter WASP-107b. We use similar HST/WFC3
observations to detect helium in the atmosphere of the hot Neptune HAT-P-11b at
the $4σ$ confidence level. We compare our observations to a grid of 1D
models of hydrodynamic escape to constrain the thermospheric temperatures and
mass loss rate. We find that our data are best fit by models with high mass
loss rates of $dot{M} approx 10^{9}$ – $10^{11}$ g s$^{-1}$. Although we do
not detect the planetary wind directly, our data are consistent with the
prediction that HAT-P-11b is experiencing hydrodynamic atmospheric escape.
Nevertheless, the mass loss rate is low enough that the planet has only lost up
to a few percent of its mass over its history, leaving its bulk composition
largely unaffected. This matches the expectation from population statistics,
which indicate that close-in planets with radii greater than 2 R$_{oplus}$
form and retain H/He-dominated atmospheres. We also confirm the independent
detection of helium in HAT-P-11b obtained with the CARMENES instrument, making
this the first exoplanet with the detection of the same signature of
photoevaporation from both ground- and space-based facilities.

 Comments: 12 pages, 9 figures, accepted for publication in ApJL Subjects: Earth and Planetary Astrophysics (astro-ph.EP) Journal reference: The Astrophysical Journal Letters, Volume 868, Issue 2, article id. L34, 6 pp. (2018) DOI: 10.3847/2041-8213/aaf166 Cite as: arXiv:1812.02214 [astro-ph.EP] (or arXiv:1812.02214v1 [astro-ph.EP] for this version)

## Submission history

From: Megan Mansfield [view email]

[v1]
Wed, 5 Dec 2018 20:39:56 UTC (1,357 KB)

### Why everyone is talking about energy storage | MNN

Ever since governments started getting serious about developing renewable energy, naysayers have been arguing that it's a pipe dream — after all, the...

### Give charities free ad space on your smartphone’s lock screen with Screen Donor

This app gives free ad space to deserving charities and NGOs on one of our tech-centric culture's most commonly seen screens - our...

### Tropicana 100% Juice 3-Flavor Fruit Blend Variety Pack, 10 Fl Oz, Bottles, (Pack of 24)

Price: (as of - Details) Now you can enjoy the refreshing taste of Tropicana’s Fruit Medley, Pineapple Peach Mango and Strawberry Orange Juice...

### Cell phones and screens are keeping your kid awake

For children and teens, using cell phones, tablets and computers at night is associated with losing sleep time and sleep quality, new research...