
Another Interstellar Object Detected in the Solar System - juancampa
https://twitter.com/AscendingNode/status/1171627233066143744
======
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)](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](https://twitter.com/tony873004/status/1171917219485192192)

~~~
healsjnr1
This animation seems to imply it is traveling orthogonal to the ecliptic. Is
that normal (maybe expected is a better word) for this kind of thing?

~~~
teraflop
That's a trick of perspective. The estimated orbital elements [1] show an
inclination of roughly 45 degrees between the object and the ecliptic. If you
click the link in the tweet, you can rotate the model and see for yourself.

The orbital plane of the solar system is not aligned in any special
orientation relative to nearby stars or the Milky Way, so we would expect
interstellar objects to arrive from all directions with equal probability.

[1]:
[https://twitter.com/AscendingNode/status/1171845027099795456](https://twitter.com/AscendingNode/status/1171845027099795456)

~~~
healsjnr1
Thanks, I was wondering if there was a perspective thing going on.

But also thinking that the larger the angle to the ecliptic, the less likely
it was something that just happened to be in a very large orbit around our
solar system.

From the discussion above though it sounds like the eccentricity tells us that
anyway.

------
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](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..._

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

~~~
rob74
LMGTFY:
[https://en.wikipedia.org/wiki/Rendezvous_with_Rama](https://en.wikipedia.org/wiki/Rendezvous_with_Rama)
:D

~~~
teh_klev
> LMGTFY

Even with a smiley face this is still a tiresome and rude response.

~~~
rob74
Sorry if anyone felt offended, not being a SF expert myself I actually did
Google "The Ramans do everything in threes" and wanted to save others the
trouble of doing so...

~~~
teh_klev
It's not the link itself, it's the LMGTFY in front. It's a form of snark.

------
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.

~~~
_kst_
"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."

An interstellar object cannot be flying by slowly enough to enter a circular
orbit. If it were, it would already have been in a circular orbit.
Trajectories can be extrapolated both into the future and into the past. It
has enough momentum to escape the Solar System if and only if it came from
outside the Solar System.

This assumes the only interaction is the gravitational pull between the Sun
and the object. A close approach to Jupiter, for example, might slow an
incoming object into an elliptical orbit, or speed a Solar System object into
a hyperbolic escape trajectory.

~~~
davidmurdoch
It it not at all possible for an interstellar object to be captured into a
stable solar orbit?

~~~
greglindahl
Not without interacting with a 3rd body, such as Jupiter.

~~~
ars
Or, apparently, if it crosses an event horizon, although I've never properly
understood how that works. (Explanations I've found typically just say: "All
paths from a black hole are toward the black hole."

~~~
greglindahl
Most things flying towards a black hole don't cross the event horizon thanks
to angular momentum.

Stars tend to get torn apart, go into the accretion disk, and then eventually
fall in. But we don't have a big black hole in the solar system.

------
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](https://twitter.com/twit_spires/status/1171939194282762240)

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

------
petschge
See also the initial professional report at
[http://www.astronomerstelegram.org/?read=13100](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.

~~~
samtheprogram
I was under the impression we did know that Voyager left our solar system --
could you clarify what you mean by this to someone not familiar with these
concepts?

[https://www.nytimes.com/2013/09/13/science/in-a-
breathtaking...](https://www.nytimes.com/2013/09/13/science/in-a-breathtaking-
first-nasa-craft-exits-the-solar-system.html)

~~~
hannasanarion
For several years there were a series of "voyager left the solar system today"
headlines, each using a different definition of the solar system boundary
because very little is known about where it is.

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

~~~
fasteddie31003
Or the object is speeding up...

~~~
davidcuddeback
The orbit didn't physically change. The author fixed his code and reran the
analysis.

------
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.

~~~
cptaj
Sadly space is super complicated and you can't piggy back on these. To land on
one you need to precisely match their speed so if you were to do that, you
could already go wherever it was going in the first place.

~~~
jsjohnst
Matching DeltaV for a short duration is easier than for a long duration, no?
I’m not an astrophysicist, but that seems to make sense to me.

~~~
dragonwriter
You match velocity, not deltaV. Since natural objects accelerate only under
environmental forces (mainly gravity for something like this), once you match
velocity and are subject to essentially the same gravitational fields, you
will stay matched (roughly).

~~~
jsjohnst
I shouldn’t have asked the question while commuting, clearly didn’t explain
myself well.

Elsewhere I saw what I thought was the speed of the comet, which was around
69k mph. Didn’t Helios 1 and 2 do something like ~150k mph[0]?

Assuming those numbers are correct (please say so if not), then what would
stop an intercept from being technically possible (even if very very very
hard)?

[0]
[https://en.m.wikipedia.org/wiki/Helios_(spacecraft)](https://en.m.wikipedia.org/wiki/Helios_\(spacecraft\))

~~~
bzbarsky
The Helios probes reached those speeds by starting out much slower than that
and then falling toward the sun, speeding up in the process.

To actually hitch a ride with another object you have to match their velocity
_and_ their location at the same time.

If the object you are trying to catch started further from the sun than you,
and was already moving faster than you, then you can't match its speed and
location by falling toward the sun: when you arrive at the same location, it
will have fallen further than you and hence picked up more kinetic energy per
unit mass than you did, and it started off moving faster than you to start
with, so it's still moving faster.

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

------
japaget
See also the Minor Planet Electronic Circular at
[https://minorplanetcenter.net/mpec/K19/K19RA6.html](https://minorplanetcenter.net/mpec/K19/K19RA6.html)

------
gbugniot
It's a comet.
[https://twitter.com/AscendingNode/status/1171894551780290560](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?

------
m3kw9
Sadly, there has to be lots more that are undetected

------
gfodor
frankly, having read the three body trilogy, these kinds of reports scare the
pants off of me. i always put a small prior that astronomers would look at
this and say "uh, oddly, it seems to be headed precisely for a direct
collision with Earth."

~~~
garmaine
That book has junk science. I wouldn’t be so concerned.

~~~
hossbeast
The word you're looking for is "fiction"

~~~
garmaine
And one shouldn't base their worldview on fiction.

