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Old 12th September 2019, 10:16 PM   #1
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Another Interstellar Visitor?

https://www.bbc.com/news/science-environment-49676757

An amateur astronomer has discovered a comet that could come from outside our Solar System.

If so, it would be the second interstellar object after the elongated body known as 'Oumuamua was identified in 2017.

The Minor Planet Center (MPC) at Harvard University has issued a formal announcement of the discovery.

The body appears to have a "hyperbolic" orbit, which would appear to indicate its origin in another planetary system.
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Old 12th September 2019, 11:22 PM   #2
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Or it could come from the Oort cloud.
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Old 13th September 2019, 02:02 AM   #3
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Originally Posted by Puppycow View Post
Or it could come from the Oort cloud.
At 31 km/s - with an eccentricity of 3.2? I don't think so.

e = 3.2 means it is definitely on a hyperbolic orbit and therefore not gravitationally bound to the Sun
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Old 13th September 2019, 07:06 AM   #4
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Originally Posted by smartcooky View Post
At 31 km/s - with an eccentricity of 3.2? I don't think so.

e = 3.2 means it is definitely on a hyperbolic orbit and therefore not gravitationally bound to the Sun
That doesn't mean it didn't originate in the Oort cloud, just that it's now going too fast to stay in orbit.
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Old 13th September 2019, 08:26 AM   #5
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Originally Posted by wollery View Post
That doesn't mean it didn't originate in the Oort cloud, just that it's now going too fast to stay in orbit.

Is a kick that large feasible? If the interaction that put it on that orbit actually did happen in our solar system the orbit of this object could be extrapolated back to the orbit of some massive object in the Oort cloud.
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Old 13th September 2019, 12:49 PM   #6
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Originally Posted by RecoveringYuppy View Post
Is a kick that large feasible? If the interaction that put it on that orbit actually did happen in our solar system the orbit of this object could be extrapolated back to the orbit of some massive object in the Oort cloud.
Feasible? Yes.

Likely? Not very.

But then, very unlikely things happen if you wait long enough.

Also, it doesn't need to be just one kick.
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Old 13th September 2019, 01:25 PM   #7
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Originally Posted by RecoveringYuppy View Post
Is a kick that large feasible? If the interaction that put it on that orbit actually did happen in our solar system the orbit of this object could be extrapolated back to the orbit of some massive object in the Oort cloud.
Anything large enough to give it a big enough kick to accelerate it to over 30 km/s and give it an eccentricity of over 3 is going to be coplanar with the rest of the planets. (the way the solar system formed dictates this). Comet Borisov (C/2019 Q4) is coming at us with an inclination of over 40°.



There isn't anything in that direction big enough to do the job.


ETA: It seems that as the orbital measurements are becoming more refined, the results for eccentricity are increasing. The original estimate was 3.2 but the later refinements are between 3.46 and 3.63.

https://www.projectpluto.com/temp/2i.htm

"the answer to why this object can't be a chunk from our own Oort cloud, for example, is pretty much the same as it was for ʻOumuamua."
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Old 13th September 2019, 01:56 PM   #8
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Originally Posted by wollery View Post
Also, it doesn't need to be just one kick.

How many more kicks in the solar system can you get once your eccentricity is hyperbolic? This a pretty large kick. Multiple encounters with multi-Jupiter sized planets all in the same highly inclined orbit after the object has been put on a course that's going to eject it? And these would be really slow moving massive Jupiters at that distance.
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Old 13th September 2019, 01:59 PM   #9
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Quote function isn't working for smartcooky's post.

Is it true that large object would have to be coplanar even at the distance of the Oort cloud? (ETA: ignore this if the link you added addresses this, I'll read it)
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Old 13th September 2019, 02:16 PM   #10
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Originally Posted by RecoveringYuppy View Post
Quote function isn't working for smartcooky's post.

Is it true that large object would have to be coplanar even at the distance of the Oort cloud? (ETA: ignore this if the link you added addresses this, I'll read it)
The orbits of the planets are coplanar. This is because of the way the solar system formed from a disk of dust which surrounded the Sun. Because that disk of dust was a disk, all in a plane, all of the planets formed in a plane as well.

It would take multiple kicks from Jupiter to Neptune sized planets to accelerate an object to 30+ km/s. Hell, the tiny Voyager spacecraft had multiple kicks from the largest planets (V1 from Jupiter and Saturn, V2 from Uranus and Neptune as well) and only managed to make 15 and 17 km/s respectively.

If such planets existed, they would have to be captured - not formed as part of the Solar System's formation. Its the only way they could be out there, and that would be an even more amazing discovery than a comet from interstellar space.
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Old 13th September 2019, 02:42 PM   #11
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Re-arranging your post slightly since the middle paragraph needs a different response.

Originally Posted by smartcooky View Post
It would take multiple kicks from Jupiter to Neptune sized planets to accelerate an object to 30+ km/s. Hell, the tiny Voyager spacecraft had multiple kicks from the largest planets (V1 from Jupiter and Saturn, V2 from Uranus and Neptune as well) and only managed to make 15 and 17 km/s respectively.
Yeah. Don't know if you saw my last post to Wollery but I mentioned that and a couple other problems.

Originally Posted by smartcooky View Post
The orbits of the planets are coplanar. This is because of the way the solar system formed from a disk of dust which surrounded the Sun. Because that disk of dust was a disk, all in a plane, all of the planets formed in a plane as well.

If such planets existed, they would have to be captured - not formed as part of the Solar System's formation. Its the only way they could be out there, and that would be an even more amazing discovery than a comet from interstellar space.
Not that I think there is much reason to hypothesize massive planets out there based on this event, but what would prevent massive planets created during the formation of our solar system from having migrated out there (which I believe is the current most accepted explanation for the Oort cloud)?
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Old 13th September 2019, 03:00 PM   #12
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The only important question here is: will it be visible to home astronomers?

JPL says: The object will peak in brightness in mid-December and continue to be observable with moderate-size telescopes until April 2020

Given a "well-developed tail" already and a distance from earth less than Jupiter, I'd be expecting a fairly good show.

Time will tell. I'll certainly be cranking the telescope up come December.
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Old 13th September 2019, 03:09 PM   #13
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Originally Posted by The Atheist View Post
The only important question here is: will it be visible to home astronomers?

I think it is now but I haven't seen a fully reliable report. This was discovered by an amateur, but probably not from his home. Some of the current reports seem to have been done with 8" instruments.


ETA: https://minorplanetcenter.net/mpec/K19/K19RA6.html
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Old 13th September 2019, 03:17 PM   #14
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Originally Posted by RecoveringYuppy View Post
Not that I think there is much reason to hypothesize massive planets out there based on this event, but what would prevent massive planets created during the formation of our solar system from having migrated out there (which I believe is the current most accepted explanation for the Oort cloud)?
A massive planet would have to be flung out there though an interaction with another massive planet. It is thought that Planets may "migrate" through incremental interactions with other planets, but they don't just execute 90° turns and head off in a new direction. It takes a massive amount of energy to change the orbit of a planet

Also, the size of Oort Cloud objects is very small; the total mass of all the materials in the outer (spherical) Oort cloud has been estimated at about five earth masses. There is not enough material out there to have a massive planet. If there was a planet large enough travelling through the Oort cloud disturbing comets, it would likely be raining comets down upon us in very large numbers.
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Old 13th September 2019, 03:46 PM   #15
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I just wonder how often we do get visitors from outside the solar system. If we have detected two in the last two years then maybe they are common. Maybe they are part of the dark matter. Be difficult to detect.

Edit. If I am right there will be another one discovered within the next few years.
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Old 13th September 2019, 06:15 PM   #16
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Originally Posted by rjh01 View Post
Maybe they are part of the dark matter. Be difficult to detect.
Impossible, not difficult, because they wouldn't be visible. Noticing the gravitational shift would also be impossible as the changes would be far too small to detect.
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Old 13th September 2019, 11:34 PM   #17
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unfortunately it is like a decade too early for the amazing esa comet interceptor mission
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Old 14th September 2019, 07:37 AM   #18
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Originally Posted by tusenfem View Post
unfortunately it is like a decade too early for the amazing esa comet interceptor mission
And even longer for a mission that could intercept this comet. Catching this comet is way beyond the capabilities of the ESA mission.

ETA: I wonder if I'm wrong about this. One article suggests that interstellar objects would be interesting targets for that machine but I can't what their source for that is. This object is far faster than anything we've even flown and way out of the plane of the ecliptic.

https://en.wikipedia.org/wiki/Comet_Interceptor

ETA:

Quote:
The Comet Interceptor mission is unique in that it is designed to encounter an as-yet unknown target, having to wait between 2 and 3 years for a target it can reach with a reasonable change in velocity (delta-v) within a total mission length of approximately 5 years.[4][5] The baseline design is solar electric propulsion.[4]
I don't see any numbers cited but what could "reasonable change in velocity" mean? Other wording in that article and at the sources cited suggests we'd have to get very lucky for an interstellar object that happened to be on an attainable trajectory.
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Old 14th September 2019, 08:48 AM   #19
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Originally Posted by RecoveringYuppy View Post
And even longer for a mission that could intercept this comet. Catching this comet is way beyond the capabilities of the ESA mission.

ETA: I wonder if I'm wrong about this. One article suggests that interstellar objects would be interesting targets for that machine but I can't what their source for that is. This object is far faster than anything we've even flown and way out of the plane of the ecliptic.

https://en.wikipedia.org/wiki/Comet_Interceptor

ETA:

I don't see any numbers cited but what could "reasonable change in velocity" mean? Other wording in that article and at the sources cited suggests we'd have to get very lucky for an interstellar object that happened to be on an attainable trajectory.
don't have the proposal here at home, so i cannot give you the delta v
but it is a flyby mission, in the equatorial plane (maybe slightly off) not a rosetta type mission
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Old 14th September 2019, 08:53 AM   #20
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It might be that Delta-v isn't even known yet. How far along is the design?

The two interstellar objects we've seen so far weren't reasonably close to the ecliptic plane. The current plan calls for this mission to wait two years at most for a suitable target. Not likely to get a suitable interstellar object in that time IMO. And an interstellar object would shorten both the planning time and the duration of the fly-by.
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Old 14th September 2019, 08:58 AM   #21
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Surely the only IMPORTANT question is, "How electric is it"?

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Old 14th September 2019, 08:24 PM   #22
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Been thinking about how easy it would be to send a spacecraft to an interstellar object that is flying though the solar system. I suggest it would be easier to send a craft to Pluto. Either that or the object is found years before it gets into the inner solar system and its path goes close to the Earth then it would not need a high speed craft to intercept. The later though would be the best case scenario.
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