Another Interstellar Object Detected in the Solar System

[CalChris]

Just as a reminder,

  circle e = 0
  earth e = 0.0167
  ellipse e < 1
  parabola e = 1
  hyperbola e > 1

So at e = 3, this object is in a sense bouncing off the sun at an angle of 180 * 2 * invsec(3) / pi or ~141 degrees.

https://en.wikipedia.org/wiki/Eccentricity_(mathematics)

[SiempreViernes]

An animation of the orbit as it is known right now: https://twitter.com/tony873004/status/1171917219485192192

[mirimir]

Interesting. This came in at ~30 km/sec. And Oumuamua came in at ~26 km/sec.

It seems that "the Sun moves through the Milky Way at about 20 km/s faster than the local average", or "local standard of rest (LSR)".[0] With the components being ...

    11.1 km/s toward the galactic center
    12.24 km/s extra in the direction of galactic rotation
    7.25 km/s toward the north galactic pole

Some ~nearby stars are coming through the galactic plane at 150 km/sec or so relative to LSR.

These objects probably came from stars with relatively low velocities relative to LSR. There might be some moving a lot faster, but the detection window would be much smaller.

0) https://en.wikipedia.org/wiki/Stellar_kinematics

[bloopernova]

...wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes...

[krapp]

>The Ramans do everything in threes...

Ironically, Arthur C. Clarke never intended for Rendezvous With Rama to be the start of a trilogy when he wrote that, even though it's an obvious trilogy hook in hindsight. It never occurred to him until readers kept asking when the other two books were coming out.

[Mobius01]

This always comes to mind when an event like this is announced. Paging Captain Norton.

[DoctorOetker]

who are the Ramans? are you suggesting these are callibration shots?

[gpderetta]

Opened the thread looking for this comment :)

[jedberg]

I see a lot of cool space stuff in the tweet and in these comments. Can someone explain this to someone without an astrophysics background? What does the eccentricity of 3 mean, why is that important, and why is this discovery important? Thanks!

[Uehreka]

Think of it this way:

If it was flying by slowly, it would get caught by the sun’s gravity and end up in a circular orbit around the sun. If the orbit was perfectly circular, it would have an eccentricity of 0.

If it was flying by a little bit faster, it might barely get caught by the sun and end up with an orbit like Halley’s comet where it comes close to the sun once every hundred years and then flies off to the far reaches of the solar system before coming back again. It would have an eccentricity of 0.9-ish.

If it was flying a little bit faster, the sun’s gravity would try to catch it, but it would fail! The object would “swoop” around the sun then go flying back the direction it came, never to return again. It would have an eccentricity of about 1 or a little more (Less than 1 means it’s in orbit, 1 or more means it’s not coming back).

If it was flying REALLY REALLY fast, the sun’s gravity would try to pull it in, but this time the object has other plans. It barely even changes course and rockets through the solar system in an almost perfectly straight line. Its eccentricity would be something like 89 (there’s no upper limit, although at a certain point the object would have to travel at close to lightspeed to acheive certain really high eccentricities if flying close to the inner solar system).

This object (the real-life one we’re talking about) is going faster than the “swoop” object but slower than the “other plans” object. Its path is being bent somewhat by the sun’s gravity, but it is going to leave an never come back. So its eccentricity is 3.

One last thing: eccentricity is PURELY a math thing that describes circles, ellipses and curves. It’s just that when you’re talking about orbital mechanics, it gets interwoven with other aspects of an object’s orbit, like its velocity and its altitude at the closest point in the orbit.

[davidcuddeback]

Eccentricity describes the shape of an orbit. 0 is perfectly circular. Between 0 and 1 is elliptical. 1 is parabolic. Above 1 is hyperbolic. So an eccentricity of 3.0 is hyperbolic, which means the object is of interstellar origin. (Picture the shape of a hyperbola in your mind. An object on that trajectory can't come back to the same point.)

With the uncertainties that come from fitting early observations, these numbers can change as more observations come in. At 1.07, it would still be possible that the final orbit turns out to not be hyperbolic. At 3.0, that's much less likely.

What makes this discovery exciting is that it would be the second object of interstellar origin that we've discovered in our own solar system (and both discoveries are fairly recent). That's a new class of object to be studied and presents an opportunity to learn something new. The fact that these two discoveries are temporally close suggests that we'll discover many more as our technology and technique improve.

[throwaway2048]

Eccentricity is a measure of how elongated/oval shaped your orbit is, eccentricity of 0 means a circular orbit, 0.5 is "very elongated orbit" (that is coming relatively close to the sun, then going very far away, think deep space comets) 1 means a parabola escape trajectory, and anything higher than 1 means a very fast escape trajectory.

The fact its eccentricity is 3 means its going through the solar system extremely fast (relative to the orbits of other things at comparable distance), and is going to exit again after slingshotting around the sun, that means its origin is extremely likely to be extra-solar because we know of no real mechanism for a body to generate such extreme speed while originating from within the solar system.

https://upload.wikimedia.org/wikipedia/commons/b/b7/Kepler_o...

In this image, red has an eccentricity of 0.7, green 1.0 and blue 1.7, the sun would be the focus. The the green and blue "orbits" never return, just like a parabola/hyperbola never curve into an ellipse, think of a graph like y=x^2.

[simplicio]

Eccentricity is a way of characterizing the curve the object makes around the sun. <1 is an ellipse, and so the object would be in orbit around the sun, and hence probably not interstellar. >1 is hyperbolic, and thus not gravitationally bound to the sun, and so probably interstellar.

The closer the eccentricity is to 1 without being equal or less, the more "curved" the trajectory is and the nearer its closes approach to the sun will be.

[dgudkov]

A helpful comment from the twitter thread:

"Not aliens. And surely they're common. But we just haven't been able to detect these things until recently. It's new to us, not new to the universe."

[1] https://twitter.com/twit_spires/status/1171939194282762240

[jlmorton]

Short Wiki article on the object: https://en.wikipedia.org/wiki/C/2019_Q4_(Borisov)

[petschge]

See also the initial professional report at http://www.astronomerstelegram.org/?read=13100

[chadcmulligan]

Something I don't understand - why is it surprising that there could be rocks floating around that come from other solar systems?

[freehunter]

I don't think it necessarily has to be surprising to be interesting. If it came from another solar system, it's traveled more than 4 light years (obviously much slower than light speed) to get here. That's a long time, and our solar system is a very small target, so the odds are (literally) astronomical.

There's a lot we don't know about the space between solar systems or the space outside of our own heliosphere. This is evidenced by our lack of understanding of when (or if) Voyager actually left our solar system. We just don't know enough to say. Having the opportunity to see something that came from outside our solar system is a good thing for science.

[_kst_]

It's not particularly surprising, but this is (probably) only the second such object we've actually seen, which makes it very interesting.

The first such object, ʻOumuamua, was both interesting (because it was the first one we saw) and surprising (because of its apparent odd shape as indicated by its observed light curve).

[garmaine]

A lot of rocks get ejected from solar systems. Current dynamical models suggest there are as many as 3 of these sorts of objects passing through on closest approach every day. We just aren’t very well equipped to detect them.

[decoyworker]

You can assume but you don't know until you actually observe them. It's no longer an assumption.

[davidcuddeback]

Update: eccentricity closer to 3.0 (still hyperbolic). https://twitter.com/AscendingNode/status/1171845027099795456

[fasteddie31003]

Or the object is speeding up...

[makerofspoons]

I'm excited that as our technology improves we will likely find objects like this increasingly frequently, and in the near future may have the ability to rapidly send a mission to intercept one.

[dogma1138]

It’s also because I think we are more actively looking for them now since we discovered one kinda by accident.

Overall I think we’ll discover that they are more common than we think which makes me wonder if we could use them to piggy back probes on them to the outer solar system and beyond since they move quite darn fast.

[mellosouls]

An interesting podcast interviewing Avi Loeb at the time on his speculative theory from the previous visitor:

https://after-on.com/episodes-31-60/040

[japaget]

See also the Minor Planet Electronic Circular at https://minorplanetcenter.net/mpec/K19/K19RA6.html

[gbugniot]

It's a comet. https://twitter.com/AscendingNode/status/1171894551780290560

[sidcool]

Is it even feasible to think of scraping something off this object for study? I mean in far future it will happen, but does current tech allow it?

[katharinaa]

So interesting. There is so much that we don't know about the solar system.

Does anyone have more helpful links on this topic?

[booleandilemma]

Can we not miss this one this time? I’m still bummed over not catching sight of the first interstellar solar sail.

[RandomBacon]

Apparently it will come within 1.7 AU of Mars and 1.9 AU of Earth.

I'm not sure if they've figured out how big it is, or what other analysis they can do of it.

Eye-balling the animation someone else link to, it looks like it will be in our solar system area for about half a year.

I have no idea if we have telescopes good enough for this. Does anyone else know?

[HarryHirsch]

ESA is planning to launch the Comet Interceptor mission in 2028: https://en.wikipedia.org/wiki/Comet_Interceptor

Hope a rewarding target comes up.

[m3kw9]

Sadly, there has to be lots more that are undetected