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Planets with Helium-Rich Atmospheres

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#1 Dave Mitsky

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Posted 23 November 2022 - 01:55 AM

For centuries, no one knew if we were alone in the universe—or if there were even other planets like ours.
 

But thanks to new telescopes and methods in the past decades, we now know there are thousands and thousands of planets out there circling faraway stars, and they come in all sorts of shapes and sizes—large and small, rocky and gaseous, cloudy or icy or wet.
 

A study by scientists with the University of Chicago, the University of Michigan and the University of Maryland suggests another for the list: planets with helium atmospheres. Moreover, the discovery may suggest a new step in our understanding of planet evolution.

 

https://phys.org/new...ich-helium.html

 



#2 Mark Gingrich

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Posted 23 November 2022 - 02:04 PM

...

 

A study by scientists with the University of Chicago, the University of Michigan and the University of Maryland suggests another for the list: planets with helium atmospheres. Moreover, the discovery may suggest a new step in our understanding of planet evolution.

If planets with helium atmospheres exist, then any intelligent, vocal-cord-equipped beings on said planets surely speak with high-pitched voices, sounding much like the Munchkins in The Wizard of Oz.

 

And yes, with regard to helium, in my reckless youth I unabashedly admit to having once inhaled...


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#3 russell23

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Posted 24 November 2022 - 10:50 AM

Here is the abstract for the paper - which is not available free:

 

https://www.nature.c...550-022-01823-8

 

 

Here is a 2020 arXiv posting by the authors that seems to be the same topic.  Not sure if this preprint is the same paper prior to two years of wrestling with a referee to get it published or if it is an earlier analysis:

 

https://arxiv.org/pdf/2002.06466.pdf



#4 DSOGabe

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Posted 25 November 2022 - 04:49 PM

If planets with helium atmospheres exist, then any intelligent, vocal-cord-equipped beings on said planets surely speak with high-pitched voices, sounding much like the Munchkins in The Wizard of Oz.

 

 

A race known as Squeakers



#5 Katharine

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Posted 25 November 2022 - 10:20 PM

A race known as Squeakers

They'd like you to know that they still want a hula hoop...



#6 russell23

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Posted 27 November 2022 - 01:56 PM

Let me provide a little additional explanation.  One of the things to understand is that many/most exoplanets discovered to date have short orbital periods and much higher stellar irradiation values than the Earth receives from the Sun.  The high stellar irradiation values can strip an H-He envelope and evaporate a significant fraction of a water planet's hydrosphere - turning it into a "steam world".

 

The authors of this study looked at the situation where high stellar irradiation preferentially strips away the hydrogen from the H-He envelope, leaving behind an atmosphere enhanced in He due to the higher erosion rate of H.  But the conditions where this mechanism applies were found to be restricted to highly irradiated planets with a low % by mass initial H-He envelope.   Specifically, the stellar irradiation needs to be be 10 - 1000x the value the Earth receives and the % mass of H-He has to be much less than the Solar System's "Neptunes", which have 10-15% H-He by mass.   The planets that can achieve helium enrichment need to have an envelope that is <0.5% by mass H-He. 

 

Anyway, as funny as it would be, nobody is going to visit these planets and get to laugh their way through a conversation in a helium rich atmosphere.  The minimum temperatures these helium enriched planets would have is 500 Kelvin to upwards of 1600 Kelvin before the H-He envelope is completely stripped.

 

For comparison, the surface temperature of Venus is ~740 Kelvin which means these planets would have a temperature ~240 Kelvin less than to roughly twice the surface temperature of Venus.  A temperature range too toasty for humans to breathe.


Edited by russell23, 27 November 2022 - 02:00 PM.

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