Starship Asterisk*

For a dwarf star to enter our solar system?

Ailean4321 wrote:
For a dwarf star to enter our solar system?

Yes: http://asterisk.apod.com/viewtopic.php? ... 38#p136438

Thanks.
That doesn't really answer my question, though.
Is it possible for this brown dwarf to enter our solar system? How?

Ailean4321 wrote:Thanks.
That doesn't really answer my question, though.
Is it possible for this brown dwarf to enter our solar system? How?

Every star is in its own orbit within the Milky Way, and these orbits are continually perturbed by interactions with other stars, and the complex gravitational field of the galaxy itself. It's a matter of statistics that some stars come close together- close enough that you could say that one is within the system of the other (depending on how you define the size of a solar system).

Brown dwarfs are quite difficult to detect (although we now have the technology to detect many more of them), so nobody knows for certain how many might be in the general environs of the Solar System- say, within a few light years. But it's likely that nothing has come too close for at least a few billion years, as such an object passing through the planetary zone would shift orbits and possibly even eject planets. Not a good thing.

Would we know in advance if this were to happen?

Ailean4321 wrote:Would we know in advance if this were to happen?

In advance? Certainly. Far enough in advance to do anything about it (if we could think of anything to do, that is)? Nope.

Rob

What do you think the gov would do about it? ...like you said, if anything? Do you think they would tell us?

Ailean4321 wrote:What do you think the gov would do about it? ...like you said, if anything? Do you think they would tell us?

This idea that the "government" would be involved comes from (bad) movies. In reality, an object coming into our system would be discovered by amateur astronomers or by academics (even if using quasi-governmental instruments like HST). There is no "government" to suppress a discovery, and no "government" to announce it. If something like a large comet were discovered coming towards Earth, or even a dwarf star that might enter our system, it would be public knowledge in short order. There is no way to keep something like that secret. In fact, the first thing a researcher would do upon making such a discovery would be to make an announcement- both to get initial credit for the find, and to quickly secure confirming observations from others, which are required to get the most accurate possible orbit. The discovery observations would almost certainly be well in advance of the orbit determination observations.

OK, good point.
Would an amateur astronomer know it was a dwarf star instead of a comet or something else?

Ailean4321 wrote:OK, good point.
Would an amateur astronomer know it was a dwarf star instead of a comet or something else?

Possibly not an amateur astronomer, but a professional astronomer with a spectrograph would have no difficulty detecting the difference between a brown dwarf and a comet.

Ann

"What if the erratic track of the comet were due to it being in a tight orbit around a brown dwarf star? Brown dwarfs are only able to be indirectly observed at distance by the gravitational lensing effect they have. They are collapsed dead stars. With huge gravitational pull. What if this dwarf were in an elliptical binary orbit with our sun? A dead twin? The comet could be seen but not the dwarf."
...copied from wordpress.com

is this possible??

by the way, i really appreciate all of your interest and participation!! I don't know much about astronomy, so I need some help thinking about the plausibility of some things that have been mentioned to me recently.

Ailean4321 wrote:Would an amateur astronomer know it was a dwarf star instead of a comet or something else?

From a single discovery exposure, probably not. It could be an asteroid, a comet, a dwarf star (assuming in the latter case it was even producing or reflecting enough light to image). A short sequence of exposures (as would be typical) would yield a rough orbit, which would probably provide evidence to separate a star from an asteroid or comet, since the star would probably be in a very hyperbolic orbit, while a comet or asteroid would be somewhere between elliptical and barely hyperbolic. Also, the star would be much further away- still outside the orbits of the planets. A comet at discovery might show signs of a coma, which would make its nature fairly clear. And of course, even the most basic color analysis (imaging through at least two filters) would make it possible to distinguish a star from a comet.

Ailean4321 wrote:"What if the erratic track of the comet were due to it being in a tight orbit around a brown dwarf star? Brown dwarfs are only able to be indirectly observed at distance by the gravitational lensing effect they have. They are collapsed dead stars. With huge gravitational pull. What if this dwarf were in an elliptical binary orbit with our sun? A dead twin? The comet could be seen but not the dwarf."
...copied from wordpress.com

is this possible??

No. First of all, we don't observe any objects in "erratic" orbits or tracks. Second, whoever wrote this has no idea what brown dwarfs actually are. They are not collapsed dead stars, they are not massive, they do not have huge gravitational pulls. They are substellar objects- sort of hybrids between stars and gas giant planets, not quite massive enough to support fusion. Perhaps the author is confusing brown dwarfs with black holes.

It is very unlikely that a brown dwarf is in orbit around the Sun (and it would not properly be considered a binary in that case). If such an object were in orbit, it would have to be very distant, in which case we would not see a comet in orbit around it because there would not be enough light from the Sun to illuminate it. That's why we don't see individual Oort Cloud objects.