[nkurz]

But it is the only chance we have ever had to directly view a largeish piece of another solar system, just millions of miles away. The next time probably won't come until we send a probe to Proxima Centauri.

While this is the only one we've seen so far, the current belief is that similar objects might actually quite common. A parallel newspaper article in the Guardian [1] cites a paper out of UCLA [2], and works through the math:

  The other group of astronomers, led by David Jewitt,
  University of California Los Angeles, estimated how 
  many other interstellar visitors like it there might
  be in our solar system.

  Surprisingly, they calculate that another 10,000 could
  be closer to the Sun than the eighth planet, Neptune,
  which lies 30 times further from the Sun than the Earth.
  Yet these are currently undetected.

  Each of these interstellar interlopers would be just
  passing through. They are travelling too fast to be
  captured by the gravity of the Sun. Yet it still takes
  them about a decade to cross our solar system and
  disappear back into interstellar space.

  If this estimate is correct, then roughly 1,000 enter
  and another 1,000 leave every year – which means that
  roughly three arrive and three leave every day.

So now that we now to look for them, it may be possible that we'll be able to find others, at least before the probe reports back from Proxima Centauri.

[1] https://www.theguardian.com/science/across-the-universe/2017...

[2] http://www2.ess.ucla.edu/~jewitt/papers/2017/JLR17.pdf

[nathanielc]

> So now that we now to look for them, it may be possible that we'll be able to find others, at least before the probe reports back from Proxima Centauri.

To me this is the most exciting part of the discovery. Previous research was quite pessimistic about our ability to observe these kinds of interstellar comets[1]. Finding the few interstellar comets among the many objects within our solar system requires effort and specialized methods. Since our previous estimates indicated that we would not be able to observe many of these interstellar comets, it did not seem like looking for them was worth the effort. Now that has changed.

Since previous estimates indicated that this discovery should not have been likely, we can be reasonably sure that previous estimates were incorrect. Meaning it now seems worth the effort to begin looking for them.

With the LSST[2] coming online in the next year or so, our ability to observe such objects will be dramatically improved over current telescopes including Pan-STARRS which discovered this one.

[1] (Disclaimer: I am an author of a previous paper which concluded that these kinds of discoveries would be nearly impossible with current telescopes. Never have I been more happy to be wrong) My paper along with several others are referenced in the Nature letter.

[2] https://www.lsst.org/

[eru]

Seems very similar to when they found the first exoplanets. The first few were big news, and now they are routine.

[Balgair]

SO worked with Dave and his lab while in grad school. On this stuff, Dave is right, trust him.

On most meteorite and asteroid science in the field, take it all with a grain of salt. There's not much data and they are pretty 'dark' as objects (low albeido, low mass/gravity, long periods, very tiny in a telescope, etc). Mostly, they are guessing at stuff. It's kinda funny how worked up they get over pretty much no data (as compared to other astro disciplines).

That said, extra-solar objects are super cool, bust mostly from an isotopic % standpoint. We then infer a lot from that stuff.

[sandworm101]

If so many are passing through, and have been doing so for millions/billions of years, then at least a few thousand must have been captured. Line up the right planet and even a high-inclination object can be slowed enough to be trapped. It would be an interesting exercise to calculate what percentage of high-inclination objects might actually be alien.

[pqh]

Would it still be travelling too fast to be captured if it hit the sun directly?

[macintux]

Is something technically captured by a gravity well if it just happens to hit the object at the center? I assume not.

[isoprophlex]

At the very least, I'd say that... after collision, assuming complete coalescence into the object, they will share identical orbital parameters

[JshWright]

It would cease to exist in that case...

[eru]

No, but that's exceedingly unlikely. Even the sun is a very tiny target.