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Most near-Earth asteroids are destroyed by the Sun, long before they get to Earth



 
 
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  #1  
Old February 23rd 16, 10:00 PM posted to sci.astro
Steve Willner
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Posts: 1,172
Default Most near-Earth asteroids are destroyed by the Sun, long before they get to Earth

In article ,
Yousuf Khan writes:
"A new study finds that most asteroids and comets are destroyed in a
drawn out, long hot fizzle, much farther from the Sun than previously
thought."

Mystery of disappearing asteroids solved | Astronomy.com
http://www.astronomy.com/news/2016/0...teroids-solved


The paper is in _Nature_ at
http://www.nature.com/nature/journal...ture16934.html
but you will need a subscription or pay to read more than the
Abstract. I didn't find a preprint.

The new result implies that many asteroids, especially dark ones,
disintegrate at a few tens solar radii rather than at the much
smaller distances one might expect. Despite the press release, I
don't see anything about what fraction of asteroids disappear this
way versus the fraction destroyed by hitting a planet.

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  #2  
Old February 24th 16, 05:28 PM posted to sci.astro
Yousuf Khan[_2_]
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Posts: 1,692
Default Most near-Earth asteroids are destroyed by the Sun, long beforethey get to Earth

On 23/02/2016 5:00 PM, Steve Willner wrote:
In article ,
Yousuf Khan writes:
"A new study finds that most asteroids and comets are destroyed in a
drawn out, long hot fizzle, much farther from the Sun than previously
thought."

Mystery of disappearing asteroids solved | Astronomy.com
http://www.astronomy.com/news/2016/0...teroids-solved


The paper is in _Nature_ at
http://www.nature.com/nature/journal...ture16934.html
but you will need a subscription or pay to read more than the
Abstract. I didn't find a preprint.

The new result implies that many asteroids, especially dark ones,
disintegrate at a few tens solar radii rather than at the much
smaller distances one might expect. Despite the press release, I
don't see anything about what fraction of asteroids disappear this
way versus the fraction destroyed by hitting a planet.


Doesn't it simply mean that any and all asteroids that gets this close
to the Sun, gets destroyed?

Yousuf Khan
  #3  
Old February 24th 16, 10:05 PM posted to sci.astro
Steve Willner
external usenet poster
 
Posts: 1,172
Default Most near-Earth asteroids are destroyed by the Sun, long before they get to Earth

In article ,
Yousuf Khan writes:
Doesn't it simply mean that any and all asteroids that gets this close
to the Sun, gets destroyed?


"This close" is not a fixed distance. According to the paper, small
and/or dark asteroids are destroyed at larger distances than big
and/or reflective ones. However the uncertainty in how destruction
distance varies with asteroid parameters isn't clear to me. It also
isn't clear to me whether destruction has to be instantaneous, though
the paper models it that way.

It was always clear that asteroids passing close enough to the Sun
would be destroyed. What's new is that "close enough" is somewhat
farther than was known. The destruction mechanism that leads to this
is still not known.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
  #4  
Old February 25th 16, 12:39 AM posted to sci.astro
Yousuf Khan[_2_]
external usenet poster
 
Posts: 1,692
Default Most near-Earth asteroids are destroyed by the Sun, long beforethey get to Earth

On 24/02/2016 5:05 PM, Steve Willner wrote:
It was always clear that asteroids passing close enough to the Sun
would be destroyed. What's new is that "close enough" is somewhat
farther than was known. The destruction mechanism that leads to this
is still not known.


Since they're talking about solar radii distances here, rather than
something like AU, so could it be a combination of the Roche Limit of
the Sun plus it's solar radiation pressure?

Yousuf Khan
  #5  
Old March 1st 16, 10:30 PM posted to sci.astro
Steve Willner
external usenet poster
 
Posts: 1,172
Default Most near-Earth asteroids are destroyed by the Sun, long before they get to Earth

In article ,
Yousuf Khan writes:
Since they're talking about solar radii distances here, rather than
something like AU, so could it be a combination of the Roche Limit of
the Sun plus it's solar radiation pressure?


Roche limit is about 3.5 solar radii even if the density is as low as
0.5, so that doesn't seem to be the mechanism. I don't see how solar
radiation pressure could break up an object. The pressure would have
to be different at different locations in such a way as to push the
object apart.

Expected surface temperatures at the relevant perihelion distances
are in the range 700 to 1200 K. These are much higher than the
boiling point of water (373 K) but rather lower than the melting
point of rocks. The actual destruction mechanism is unknown, but
that's no surprise. If there were an obvious destruction mechanism,
the statistical result would have been expected.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
 




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