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(Big Think)   NASA's Kepler mission taught us that practically all stars possess exoplanets. Now we're learning something deeper: many of them don't. Here's why   (bigthink.com) divider line
    More: Cool, Planet, Star, Gas giant, Solar System, Hydrogen, Extrasolar planet, parent stars, Jupiter  
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1056 clicks; posted to STEM » on 10 Aug 2022 at 6:52 PM (25 weeks ago)   |   Favorite    |   share:  Share on Twitter share via Email Share on Facebook



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2022-08-10 7:26:59 PM  
5 votes:
That or the planets around those stars are too small for us to detect with current instruments and techniques. There's a reason most of the exoplanets we HAVE found are both bigger and closer than any planets in our own solar system.

If there was an identical twin of our system just 50 light years from us right now, we wouldn't be able to detect ANY of the terrestrial planets using the equipment we have today. We'd be able to detect Jupiter, but only BARELY, and only if the ecliptic  was aligned edge-on to us.
 
TWX
2022-08-10 6:59:48 PM  
4 votes:
It makes sense, if your universe only has hydrogen and helium, then it doesn't have the sort of stuff necessary to condense into planets.

It's after enough stars have fused heavier elements that it becomes possible for planets to form.

I wonder if a sand-grain within an oyster to form a pearl is an apt analogy.  Without the grain for the pearl to be constructed around, nothing forms.
 
2022-08-10 7:41:43 PM  
2 votes:

akallen404: That or the planets around those stars are too small for us to detect with current instruments and techniques. There's a reason most of the exoplanets we HAVE found are both bigger and closer than any planets in our own solar system.

If there was an identical twin of our system just 50 light years from us right now, we wouldn't be able to detect ANY of the terrestrial planets using the equipment we have today. We'd be able to detect Jupiter, but only BARELY, and only if the ecliptic  was aligned edge-on to us.


That's the case for not seeing smaller planets around younger stars.

Without enough heavy elements, it's impossible to form the grains that drive core accretion. And without core accretion, there's no way to form gravitationally bound planets before the star switches on and evaporates the disk (which shuts down planet growth). Once the star initiates fusion, the UV radiation flow photoevaporates all the gas in the disk that has a direct line of sight to the star. This also occurs if there is a nearby massive star in the cluster.

There's another interesting factor that heavy elements are relevant to that TFA doesn't get into. Without dusty - specifically carbonaceous - grains mopping up electrons, the midplane of the disk will remain ionized. As long as it's ionized and conductive, the magnetorotational instability will continue to efficiently drive mass into the star and keep things too turbulent for grains to accrete onto each other.
 
2022-08-10 7:00:52 PM  
1 vote:
We are the First Ones.
 
2022-08-10 7:06:57 PM  
1 vote:
Because they are violent machines of destruction, every bit as capable as a black hole of farking shiat up.
 
2022-08-10 11:09:12 PM  
1 vote:

akallen404: That or the planets around those stars are too small for us to detect with current instruments and techniques. There's a reason most of the exoplanets we HAVE found are both bigger and closer than any planets in our own solar system.

If there was an identical twin of our system just 50 light years from us right now, we wouldn't be able to detect ANY of the terrestrial planets using the equipment we have today. We'd be able to detect Jupiter, but only BARELY, and only if the ecliptic  was aligned edge-on to us.


I was going to say, "what if they revolved the other way and never transited?"

/   glad I'm not crazy
//  or at least I have company if I am
/// THREE exoplanets
 
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