Interstellar Comet

[tony873004]

There's a chance that the first truly-interstellar comet has been discovered.

Many comets have been deemed hyperbolic. That means they're not bound to the Sun. They have eccentricities >= 1.
Wikipedia has a list of them:
https://en.wikipedia.org/wiki/List_of_hyperbolic_comets

C/1980 E1 has the largest eccentricity of 1.057
But these comets were either boosted to escape velocity by a planet, or have eccentricities < 1 if their orbital elements are taken with respect to the Solar System's barycenter instead of the Sun. In other words, they came from here.

Newly-discovered comet, C/2017 U1, has an eccentricity of 1.2, and it hasn't come close to any of our gas giants. If confirmed, that would make it the first observed visitor from beyond the solar system, besides charged particles from Beta Pictoris.

http://www.minorplanetcenter.net/mpec/K17/K17UI1.html

[tony873004]

Simulation: http://orbitsimulator.com/gravitySim...9_C2017U1.html
Animated GIF: https://twitter.com/tony873004/statu...09368903622656

[slang]

Wow, would be nice indeed.

[Ross 54]

They reportedly have only six days of observations of this comet. Because of this, the hyperbolic orbit, and so its interstellar status, is somewhat tentative. Does anyone know how long a series of observations is necessary to remove the ambiguity?

[George]

It's Planet 9's doing!!! [Sorry, I strangely felt the urge to be hyperbolic. But wouldn't that be cool?]

[selden]

It's Planet 9's doing!!! [Sorry, I strangely felt the urge to be hyperbolic. But wouldn't that be cool?]

That was my immediate thought, too. Of course, there must be many actual interstellar bodies of similar mass, whether they originate free-flying in interstellar dust clouds or are the result of planetary migrations throwing them out of their "home" systems.

[Swift]

Newly-discovered comet, C/2017 U1, has an eccentricity of 1.2, and it hasn't come close to any of our gas giants. If confirmed, that would make it the first observed visitor from beyond the solar system, besides charged particles from Beta Pictoris.

http://www.minorplanetcenter.net/mpec/K17/K17UI1.html

And I thought of this...

Then the orbit was calculated, and the mystery was resolved - to be replaced by a greater one. 31/439 was not traveling on a normal asteroidal path, along an ellipse which it retraced with clockwork precision every few years. It was a lonely wanderer between the stars, making its first and last visit to the solar system - for it was moving so swiftly that the gravitational field of the sun could never capture it. It would flash inwards past the orbits of Jupiter, Mars, Earth, Venus and Mercury, gaining speed as it did so, until it rounded the sun and headed out once again into the unknown.

From Rendezvous with Rama by Arthur C. Clarke

[slang]

It already has its own wikipedia page, for those who find that more readable than orbit elements. Guess whose pictures are in there?

C/2017 U1 (Pan-STARRS)

And I thought of this...

You too, eh?

Do the comet specialists have some kind of protocol to deal with an object like this (interstallar comet, not Rama), observation wise? I would think they would be extra interested in its composition in such cases.

[01101001]

C/2017 U1 (Pan-STARRS)

Now A/2017 U1

On October 25, in very deep stacked images taken at the Very Large Telescope (VLT) the object was found to show no presence whatsoever of any cometary nature. The object was renamed A/2017 U1, becoming the first comet to ever be re-designated as an asteroid.

[Eclogite]

Do the comet specialists have some kind of protocol to deal with an object like this (interstallar comet, not Rama), observation wise? I would think they would be extra interested in its composition in such cases.

Composition would be everything! One would hope it would turn up some wonderful surprises, opening upnew avenues of speculation and possibility.

[CJSF]

i thought I saw reports that the refined orbital parameters ruled out interstellar origin? Imma go check.

[edited]
OK, it was brief discussion on social media; if you drop the least reliable observation, the parameters (eccentricity, mostly?) drop, making it non-interstellar. I don't see anything "official" so, who knows?

CJSF

[Ross 54]

Further observations saw the eccentricity increase from 1.18 to 1.19. This places the object's orbit more firmly in the hyperbolic category than before.

They're saying that the object was probably an icy body from the outer part of its star system. These are reportedly the most likely to have their orbits substantially affected by interactions with planets, or passing stars.

The object shows no coma, so presumably would have lost its ice. In the given scenario, it seems that it must have undergone two gravitational encounters. The first forcing it inward toward its star, where its ices sublimed away, and the second ejecting it from its star system and sending it our way.

It might be simpler to think in terms of an inner system asteroid, without substantial ice to begin with, which managed to encounter a major planet severely enough to be ejected from the system. This might be more likely to work in a system with a close-in 'hot Jupiter'

[selden]

My simplistic understanding is that when large planets migrate they're flinging protoplanets in all directions. Presumably inward-migrating planets would tend to generate more outward-flying protoplanets. Doubtless many of the ones sent outward would escape from the system. I'd expect very few to make it deep into other planetary systems just because those systems are such small targets.

[selvaarchi]

From the Nat. Geographic article "(This spacecraft could visit the star system next door in the not-so-distant future.)".

So can it be a probe scouting the neighbouring solar systems???

https://news.nationalgeographic.com/...space-science/

"Rivkin adds that astronomers did examine whether this object is from our solar system but got gravitationally nudged by Jupiter or Saturn into its careening arc. "People don't think this is the case," he says. "They think this is a legit, bona-fide interstellar object." (This spacecraft could visit the star system next door in the not-so-distant future.)"

Sent from my SM-G900F using Tapatalk

[glappkaeft]

From the Nat. Geographic article "(This spacecraft could visit the star system next door in the not-so-distant future.)".

So can it be a probe scouting the neighbouring solar systems???

No, that line is only a badly placed link to an older article about laser power light sails.

[chornedsnorkack]

By which right is it an asteroid? It is not an orbiting member of solar system.

If/when an object passes through Solar System without becoming bound to Solar System, and that object is large enough to be round due to gravity and would clear an orbit if it remained on one (but does not have time to do so during its single hyperbolic pass) would its presence within Solar System qualify it as a planet?

[George]

By which right is it an asteroid? It is not an orbiting member of solar system.

If/when an object passes through Solar System without becoming bound to Solar System, and that object is large enough to be round due to gravity and would clear an orbit if it remained on one (but does not have time to do so during its single hyperbolic pass) would its presence within Solar System qualify it as a planet?

Is it not a mute question if it has no orbit? It would be cool, however, to give these objects a fun label. In-N-Out Burger has their "Animal" designation for special fries and burgers, though not on their menu. Anaroids! [I must be getting hungry.]

[glappkaeft]

By which right is it an asteroid? It is not an orbiting member of solar system.

I'm not aware of any formal scientific definition of asteroids (pretty sure it's a case of I know it when I see it) but going by the pictures it is certainly "star-like". It however doesn't fit either the pre-2006 "Minor Planet" definition or the current "Small Solar System Body" definition.

[01101001]

By which right is it an asteroid? It is not an orbiting member of solar system.

When did you change the definition of "asteroid"?

Or do you think "orbit" means only elliptical orbits and excludes hyperbolic orbits?

Again, the announcement of the reclassification from comet to asteroid, with the implied authority, is MPEC (Minor Planet Electronic Circular) 2017-U183: A/2017 U1

The prefix for the designation 2017 U1 is therefore being changed to
A/, in line with the 1995 IAU Resolution on the system of comet designations.

Its classification could change with more data, or with new classification rules from the IAU.

[Noisy Rhysling]

Does it necessarily have to be a former solar planet?

[publiusr]

Simulation: http://orbitsimulator.com/gravitySim...9_C2017U1.html
Animated GIF: https://twitter.com/tony873004/statu...09368903622656

That seems to make a pretty hard turn along and generally across the plane(s) where our planets orbit.

Anything along its path?

Please say Ceres--maybe DAWN could have a new target after all?

[lbfjrmd]

was likely an alien probe ... glad it apparently found earth nothing of interest as it never slowed down! whew!

[tony873004]

That seems to make a pretty hard turn along and generally across the plane(s) where our planets orbit.

Anything along its path?

Please say Ceres--maybe DAWN could have a new target after all?

I'm just guessing, but I doubt that DAWN's camera is optimized for long-exposure deep sky observing, as its primary mission is to study something bathed in bright sunlight.

Here are a few more animations and simulations of A/2017 U1 that I made that I posted on my Twitter account.
https://twitter.com/tony873004/statu...34271495254018
https://twitter.com/tony873004/statu...28678963658752
https://twitter.com/tony873004/statu...09368903622656
https://twitter.com/tony873004/statu...37689843023872

[Ross 54]

Intriguing to learn that the SETI Institute has shown interest in this object. SETIQuest info, the website for their Allen Telescope Array, has reported their intention to observe the object on Oct. 30, in the radio range of 1 to 3 GigaHertz. Today, they report plans to observe it again. Asteroids are not known for radio emissions. It appears that they are considering the possibility that the object is something else, altogether.

http://www.setiquest.info

[schlaugh]

Sounds more like a publicity stunt just to draw eyeballs and clicks and donations. What can they possibly “hear” from an asteroid?


Sent from my iPhone using Tapatalk Pro

[Ross 54]

This scarcely looks like a 'publicity stunt'. No mention at all is made of it on the SETI Institute's main website. It only appears as a few, not-very-prominent lines, under 'observer notes' at the website dedicated specifically to the work of the Allen Telescope Array.

It seems a reasonable inference that a SETI facility observing an object anticipates the possibility that it could be something other than an asteroid, and might emit intelligent signals. It appears obvious that they are aware that the odds of this being the case are quite long. They apparently still consider testing this hypothesis repeatedly, to be worthwhile.

[schlaugh]

OK, maybe I'm being a bit harsh, but what science they do they expect to gain by listening to an asteroid? Of course their ET expectations are low for this object, but surely they must anticipate some results beyond the null data received from A/2017 U1?

And why those particular wavelengths and not others?

[lbfjrmd]

if it comes back soon for a closer 'look' we will know!

[CJSF]

I think they are going to "listen" for intelligent or "non natural" radio emissions from the object.

It's the SETI Institute.

Why would they anticipate anything rather than just observe and sort through whatever they do or don't get? Maybe there'll be some sort of interaction/emission that will give them a baseline for observing objects of unknown/extraterrestrial/extrasolar origin. What *does" an asteroid emit at the wavelengths one might expect ETI to use? Or worded a bit differently: Does an asteroid emit nothing at the wavelengths one might expect ETI to use?

CJSF

[schlaugh]

I mean the folks at SETI must have some idea of what to expect when they study the asteroid, even if it's a null result; for example the selected frequencies tell us they want to look in a particular range. And that's OK, but why those frequencies? (I understand the ATA is set up to look at 1GhZ to 10Ghz so their options are somewhat limited). Certainly they could just point and listen, but wouldn't they do so against a plan or a hypothesis?

Optical imagery on the asteroid has been sparse. Have any radio telescopes tried to obtain an image as was done for other passing bodies? Or is it too far away?