GJ 436 b atmosphere and evaporation tail

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

Quote :

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 8.8±4.5% near mid-transit, to 22.9±3.9% ∼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 23.7±4.5%, 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 3.7×106−1.1×109 g s−1, corresponding to an atmospheric lifetime of 4×1011−2×1014 years.

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

Aliens with Mickey Mouse voices...

http://www.sciencedaily.com/releases/2015/06/150624132433.htm I wonder if this is not mimicking transits of ucf 1 and 2

The paper and a video :

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

https://www.youtube.com/watch?v=stcT2Nm2VwU

on arxiv now in pdf http://arxiv.org/abs/1506.07541

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.

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?)

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