<p>No.</p>
<p>The motion of comets is determined by the gravity of the sun (principally) but also by the gravity of the other planets, and to some extent the propulsion that comes from the gases that get propelled into space as they heat up.</p>
<p>The gravitational forces are very well understood, including the effects of other planets.  This means we can make quite accurate predictions of where the comet will be on any day. And we know it won't get anywhere near Earth.</p>
<p>The non-gravitational forces are less predictable, but they are also much weaker than the gravity of the sun.  Over a long orbit they can be significant, but in the relatively short time till the comet reaches the inner solar system, they aren't strong enough to make the comet &quot;veer off course&quot;.</p>
<p>Eventually the Earth will be hit by a large comet or asteroid and the effects will be disastrous.  But not this comet, this time around.  We have got pretty good at seeing the dangerous asteroids, and no known asteroid will hit the Earth for the next few hundred years.</p>

CC BY-SA 4.0
2021-10-07T03:14:18.773Z
2021-10-07T03:14:18.773Z
James K
<p>How can we possibly know that this comet took 3 plus million years to get back to the present orbit it is at now. Is it on a constant circular path. If so . Does that not mean  we can compute the size of the universe based on the 3 plus million years prediction. I think not. Its all circumstance.</p>

CC BY-SA 4.0
2021-10-06T22:22:13.420Z
2021-10-06T22:22:13.420Z
james duff
<p>At a size of 100 kilometers, this comet is ten times the one that exterminated the dinosaurs on Earth. It is headed towards our Solar System and expected to arrive in 2031. It is projected to swing by Saturn's orbit . Is there any chance that it could change course and collide with Earth ?</p>

CC BY-SA 4.0
2021-09-29T19:48:16.697Z
No chance. [It won't even get close](https://en.wikipedia.org/wiki/C/2014_UN271_(Bernardinelli-Bernstein)#Orbit).
Aaron F
CC BY-SA 4.0
2021-09-29T20:06:39.653Z
What do you mean "change course?"
Rory Alsop
CC BY-SA 4.0
2021-09-29T21:17:03.133Z
@RoryAlsop well maybe they miscalculated its course or some gravitational force from a Planet or the Sun causes it to veer off on a collision course with Earth ? Even if we avoid this one , how long can our luck hold out ? Eventually, won't this be the fate of the Earth, to be taken out by a surprise collision with an asteroid or comet ?
Peter U
CC BY-SA 4.0
2021-09-29T21:19:49.673Z
This was a valid question . I don't see what the need was for a downvote ?
Peter U
CC BY-SA 4.0
2021-09-29T21:25:33.247Z
@PeterU If you look at the wiki page graphic, you can see that the orbital plane of the comet is not aligned with the orbital plane of the planets around the Sun.  Also, Saturn is not very close even when the comet is at perigee, so the Sun's gravitational force dominates the orbit.  That means the orbit is very predictable.  The chance of a close flyby or collision changing the comet's orbit is negligible.  Also, our luck could easily hold out until the Sun grows enough to end all life here.  Large comet and asteroid strikes become less likely as the solar system ages.
Connor Garcia
CC BY-SA 4.0
2021-09-29T21:25:39.663Z
@Aaron F It says in the link that you provided ,that this Comet is not bound by the Sun, so what is it being propelled by then ?
Peter U
CC BY-SA 4.0
2021-09-29T21:28:44.587Z
@Connor Garcia Why is that , that "large comet and asteroid strikes become less likely as the solar system ages ?
Peter U
CC BY-SA 4.0
2021-09-29T21:41:39.373Z
@PeterU Because more of them get taken out of circulation by impacting the Sun and planets.
Connor Garcia
CC BY-SA 4.0
2021-09-29T21:52:11.057Z
@PeterU "not bound by the Sun" just means that it's not in an elliptical orbit; its orbit is  hyperbolic, so it will leave the Solar System eventually. It's still being 'propelled' by gravity.
Jim421616
CC BY-SA 4.0
2021-09-30T03:03:32.350Z
No: https://mashable.com/article/giant-comet-discovery-solar-system?amp
Nilay Ghosh
CC BY-SA 4.0
2021-09-30T03:39:32.240Z
@Jim421616 When you say that "it's still being propelled by gravity" are you referring to the Sun's gravity ?
Peter U
CC BY-SA 4.0
2021-09-30T03:41:32.723Z
@PeterU Yes; the comet is being pulled toward the Sun because of the Sun's gravity, but it is moving too fast to enter a stable orbit. As the cyan line in https://en.wikipedia.org/wiki/C/2014_UN271_(Bernardinelli-Bernstein)#/media/File:2014_UN271.jpg this diagram shows, it will slingshot around the Sun and leave the Solar System.
Jim421616
CC BY-SA 4.0
2021-09-30T10:23:08.690Z
The [Wikipedia article](https://en.wikipedia.org/wiki/C/2014_UN271_(Bernardinelli-Bernstein)#Orbit) says that the comet is "loosely bound by the sun."  Indications are that it's  probably in a _very_ elliptical orbit that will bring it back to perihelion in about 4.5 million years.
notovny
<comets>
Is there any chance Comet Bernardinelli-Bernstein could collide with Earth?
Peter U
# Is there any chance Comet Bernardinelli-Bernstein could collide with Earth?

(Asked by: username_0 on 2021-09-29)

At a size of 100 kilometers, this comet is ten times the one that exterminated the dinosaurs on Earth. It is headed towards our Solar System and expected to arrive in 2031. It is projected to swing by Saturn's orbit . Is there any chance that it could change course and collide with Earth ?

**Tags:** comets
> **Comments:**
> **username_1**: No chance. [It won't even get close](https://en.wikipedia.org/wiki/C/2014_UN271_(Bernardinelli-Bernstein)#Orbit).  
> **username_2**: What do you mean "change course?"  
> **username_0**: @RoryAlsop well maybe they miscalculated its course or some gravitational force from a Planet or the Sun causes it to veer off on a collision course with Earth ? Even if we avoid this one , how long can our luck hold out ? Eventually, won't this be the fate of the Earth, to be taken out by a surprise collision with an asteroid or comet ?  
> **username_0**: This was a valid question . I don't see what the need was for a downvote ?  
> **username_3**: @PeterU If you look at the wiki page graphic, you can see that the orbital plane of the comet is not aligned with the orbital plane of the planets around the Sun.  Also, Saturn is not very close even when the comet is at perigee, so the Sun's gravitational force dominates the orbit.  That means the orbit is very predictable.  The chance of a close flyby or collision changing the comet's orbit is negligible.  Also, our luck could easily hold out until the Sun grows enough to end all life here.  Large comet and asteroid strikes become less likely as the solar system ages.  
> **username_0**: @Aaron F It says in the link that you provided ,that this Comet is not bound by the Sun, so what is it being propelled by then ?  
> **username_0**: @Connor Garcia Why is that , that "large comet and asteroid strikes become less likely as the solar system ages ?  
> **username_3**: @PeterU Because more of them get taken out of circulation by impacting the Sun and planets.  
> **username_4**: @PeterU "not bound by the Sun" just means that it's not in an elliptical orbit; its orbit is  hyperbolic, so it will leave the Solar System eventually. It's still being 'propelled' by gravity.  
> **username_5**: No: https://mashable.com/article/giant-comet-discovery-solar-system?amp  
> **username_0**: @Jim421616 When you say that "it's still being propelled by gravity" are you referring to the Sun's gravity ?  
> **username_4**: @PeterU Yes; the comet is being pulled toward the Sun because of the Sun's gravity, but it is moving too fast to enter a stable orbit. As the cyan line in https://en.wikipedia.org/wiki/C/2014_UN271_(Bernardinelli-Bernstein)#/media/File:2014_UN271.jpg this diagram shows, it will slingshot around the Sun and leave the Solar System.  
> **username_6**: The [Wikipedia article](https://en.wikipedia.org/wiki/C/2014_UN271_(Bernardinelli-Bernstein)#Orbit) says that the comet is "loosely bound by the sun."  Indications are that it's  probably in a _very_ elliptical orbit that will bring it back to perihelion in about 4.5 million years.  

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## 2 answers

### Answer by username_7 on 2021-10-07. Score: 2

No.

The motion of comets is determined by the gravity of the sun (principally) but also by the gravity of the other planets, and to some extent the propulsion that comes from the gases that get propelled into space as they heat up.

The gravitational forces are very well understood, including the effects of other planets. This means we can make quite accurate predictions of where the comet will be on any day. And we know it won't get anywhere near Earth.

The non-gravitational forces are less predictable, but they are also much weaker than the gravity of the sun. Over a long orbit they can be significant, but in the relatively short time till the comet reaches the inner solar system, they aren't strong enough to make the comet "veer off course".

Eventually the Earth will be hit by a large comet or asteroid and the effects will be disastrous. But not this comet, this time around. We have got pretty good at seeing the dangerous asteroids, and no known asteroid will hit the Earth for the next few hundred years.


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### Answer by username_8 on 2021-10-06. Score: -5

How can we possibly know that this comet took 3 plus million years to get back to the present orbit it is at now. Is it on a constant circular path. If so . Does that not mean we can compute the size of the universe based on the 3 plus million years prediction. I think not. Its all circumstance.


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