GJ 436 b atmosphere and evaporation tail

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GJ 436 b atmosphere and evaporation tail

Post by Sirius_Alpha on 27th March 2014, 8:27 pm

Lyman-α Transit Spectroscopy and the Neutral Hydrogen Tail of the Hot Neptune GJ436b
http://arxiv.org/abs/1403.6834

To date, more than 750 planets have been discovered orbiting stars other than the Sun. Two sub-classes of these exoplanets, "hot Jupiters" and their less massive counterparts "hot Neptunes," provide a unique opportunity to study the extended atmospheres of planets outside of our solar system. We describe here the first far-ultraviolet transit study of a hot Neptune, specifically GJ436b, for which we use HST/STIS Lyman-α spectra to measure stellar flux as a function of time, observing variations due to absorption from the planetary atmosphere during transit. This analysis permits us to derive information about atmospheric extent, mass-loss rate from the planet, and interactions between the star and planet. We observe an evolution of the Lyman-α lightcurve with a transit depth of GJ436b from 8.84.5% near mid-transit, to 22.93.9% ∼2 hours after the nominal geometric egress of the planet. Using data from the time-tag mode and considering astrophysical noise from stellar variability, we calculate a post-egress occultation of 23.74.5%, demonstrating that the signature is statistically significant and of greater amplitude than can be attributed to stellar fluctuations alone. The extended egress absorption indicates the probable existence of a comet-like tail trailing the exoplanet. We calculate a mass-loss rate for GJ436b in the range of 3.7106−1.1109 g s−1, corresponding to an atmospheric lifetime of 41011−21014 years.


Last edited by Sirius_Alpha on 26th June 2015, 7:18 pm; edited 1 time in total

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Re: GJ 436 b atmosphere and evaporation tail

Post by tommi59 on 12th May 2015, 2:14 am

http://arxiv.org/abs/1505.02221
It has to be interested I am wonder what influence thin helium atmosphere can have on habitability on sub neptunes and super earths
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Re: GJ 436 b atmosphere and evaporation tail

Post by Stalker on 12th May 2015, 3:37 am

Aliens with Mickey Mouse voices...

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Re: GJ 436 b atmosphere and evaporation tail

Post by tommi59 on 24th June 2015, 5:16 pm

http://www.sciencedaily.com/releases/2015/06/150624132433.htm I wonder if this is not mimicking transits of ucf 1 and 2
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Re: GJ 436 b atmosphere and evaporation tail

Post by Led_Zep on 25th June 2015, 6:43 am

The paper and a video :

http://www.spacetelescope.org/static/archives/releases/science_papers/heic1515a.pdf

https://www.youtube.com/watch?v=stcT2Nm2VwU
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Re: GJ 436 b atmosphere and evaporation tail

Post by tommi59 on 26th June 2015, 5:17 am

on arxiv now in pdf http://arxiv.org/abs/1506.07541
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Re: GJ 436 b atmosphere and evaporation tail

Post by Shellface on 26th June 2015, 5:12 pm

tommi59 wrote:I wonder if this is not mimicking transits of ucf 1 and 2
Eh, I doubt that would be possible. This is, y'know, hydrogen, which doesn't really do a whole lot in the infra-red.

Pretty staggering that the transit depth is 56% in the UV - that's a depth typically only inhabited by eclipsing binaries in the visible. If my calculations are correct, the transits cause the star to fainten by 0.9 magnitudes in that band! Goodness.

I wonder what the UV transits of a similar planet around a young star - like, say, HAT-P-11 - look like, especially in terms of mass loss.

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Re: GJ 436 b atmosphere and evaporation tail

Post by Lazarus on 26th June 2015, 7:06 pm

Good example of why having a telescope operating in the ultraviolet is a good thing, and why JWST cannot be considered to be a replacement for Hubble.

Would be interesting to find out what the situation looks like for helium escaping from the planet, could be a test for the helium planets hypothesis.

(maybe the material about the GJ 436 b atmosphere should be merged with this thread?)
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Re: GJ 436 b atmosphere and evaporation tail

Post by Sirius_Alpha on 26th June 2015, 7:15 pm

That's a good idea. This was getting off-topic with respect to the original thread.

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Re: GJ 436 b atmosphere and evaporation tail

Post by tommi59 on 17th July 2015, 3:21 am

http://beyondearthlyskies.blogspot.ie/2015/07/forming-graphite-like-carbon-in.html?utm_source=BP_recent
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