
An exoplanet has been found in the ‘Neptunian Desert’ - lelf
https://phys.org/news/2019-05-forbidden-planet-neptunian.html
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eloff
It's posited that this planet kept its atmosphere despite intense solar
radiation pressure because it either moved into this orbit recently from a
safer place, or it had much more atmosphere to begin with. I wonder if maybe
it just has a very powerful magnetic field that protects it, just like Earth's
does.

That's the reason Earth has kept its atmosphere while Mars did not, despite
the fact that Mars is twice as far from the sun.

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dwaltrip
> I wonder if maybe it just has a very powerful magnetic field that protects
> it, just like Earth's does.

With an orbit of 1.3 days, I would guess that it is tidally locked, which I
think would make it unlikely to have a strong magnetic field.

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cevn
Why? Is it because the sun batters the same side of the field with radiation
as opposed to distributing it evenly?

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genocidicbunny
Because its far less likely that it has a rotating core due to being tidally
locked. You need something like that to generate a planetary magnetic field.

~~~
mgsouth
Delayed edit: Yes, apparently tidally-locked planets can have a surprisingly
large magnetic field. Evidently the major reason for planetary fields is
convection, not rotation. ([0] cites [1]) However, I believe there are also
homopolar [2] generation effects due to the star and the planet's (tidally
locked) rotation. [3] looked at fields caused by convection due to tidal
flexing. [4] talks about magnetic interactions between stars and close
planets.

[0] [https://www.quora.com/How-does-the-magnetic-field-of-a-
star-...](https://www.quora.com/How-does-the-magnetic-field-of-a-star-..).

[1] “Energy flux determines magnetic field strength of planets and stars”, U.
R. Christensen et al, Nature vol 457, pages 167–169

[2]
[https://en.wikipedia.org/wiki/Homopolar_generator#Astrophysi...](https://en.wikipedia.org/wiki/Homopolar_generator#Astrophysi..).

[3] [https://exoplanets.nasa.gov/news/217/earth-like-
exoplanets-m...](https://exoplanets.nasa.gov/news/217/earth-like-
exoplanets-m..).

[4]
[https://www.youtube.com/watch?v=HjfOdjpNZHo](https://www.youtube.com/watch?v=HjfOdjpNZHo)
(Talk by Evgenya Shkolnik, part of Short Course on Magnetic Fields: A Window
to a Planet's Interior and Habitability at the Keck Institute for Space
Studies at Caltech on August 12, 2013)

~~~
cevn
I learned so much today...

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willidiots
(Orbiting a distant K-dwarf star)

Original paper, I believe:
[https://arxiv.org/abs/1809.00678](https://arxiv.org/abs/1809.00678)

~~~
Raphmedia
Thank you, this was unclear to me after reading the article. This planet is
not in our own solar system.

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3JPLW
That's the definition of exoplanet :)

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willidiots
IIRC the original link didn't include "exo". The whole article seemed
intentionally vague in that regard.

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martinpw
The HN headline is incomplete and therefore confusing. I realize it is an
attempt to avoid the sadly clickbaity phys.org headline, but the fact the
planet is smaller than Neptune and has its own atmosphere is not the
interesting thing. The interesting thing is that the planet is smaller than
Neptune with its own atmosphere _in the region close to stars where Neptune-
sized planets have not previously been found_.

~~~
sctb
OK, we've updated it from “An exoplanet smaller than Neptune with its own
atmosphere has been discovered”. In either case I think users will be able to
decide whether or not their Neptune-related exoplanet curiosity is aroused
enough to click through to the article.

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rozab
What the hell is the Neptunian Desert? All I can find on google is articles
about this, none of which actually explain what it is. Is it an actual
location in space or just a space in the distribution of planets?

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Abundnce10
From the article:

 _The Neptunian Desert is the region close to stars where no Neptune-sized
planets are found. This area receives strong irradiation from the star,
meaning the planets do not retain their gaseous atmosphere as they evaporate
leaving just a rocky core. However NGTS-4b still has its atmosphere of gas._

~~~
libria
Not sure why GP's downvoted, the definition sucks. What's "close to stars"?
1AU? Here to Pluto? Here to the Oort cloud? 1LY? In the orbital plane?
Localized to an arc or surround ing the Sun?

Then the link to desert goes to nothing but Earth deserts and the wikipedia
article was literally made today. It's like the author has no clue what the
Neptunian Desert is.

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PorterDuff
Imagine what the weather is like.

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PorterDuff
lol. Say what? I get downvoted for wondering what a large planet with an
atmosphere that's close to it's star has for weather?

~~~
PorterDuff
I decided to declare a jihad on downvotes. In some ways, this site is as bad
as reddit with the children and their 'vote' concept. Every downvoted comment
gets an upvote from me, it doesn't matter what they say.

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ilovewhiskey
Wheatley became an Astronomy professor.

