Posted on 12/03/2018 9:26:27 AM PST by ETL
Most stars with the mass of the sun or larger have one or more companion stars, but when and how these multiple stars form is one of the controversial central problems of astronomy. Gravity contracts the natal gas and dust in an interstellar cloud until clumps develop that are dense enough to coalesce into stars, but how are multiple stars fashioned? Because the shrinking cloud has a slight spin, a disk (possibly a preplanetary system) eventually forms.
In one model of binary star formation, this disk fragments due to gravitational instabilities, producing a second star. The other model argues that turbulence in the contracting cloud itself fragments the clumps into multiple star systems. In the first case, simulations show that the two stars should be relatively close together, typically less than about 600 astronomical units (one AU is the average distance of the earth from the sun).
If the second mechanism is correct, both close and wide binary pairs can form. A distinguishing feature of the turbulent fragmentation process, and one that facilitates an observational test, is that the seeds for multiplicity are produced early in the pre-stellar phases.
CfA astronomers Sarah Sadavoy and Mike Dunham were members of a team of astronomers that used the VLA and ALMA radio and millimeter-wave facilities to study seventeen protostellar systems of multiple-stars in the nearby Perseus cloud. The sensitive observations were able to reveal the environments of the systems and determine the presence of any small-scale rotation or surrounding material. Twelve of the systems were spatially resolved, and eight showed dust emission structures surrounding the pair.
The slightly more evolved systems in the set showed no evidence for circumbinary dust; they have probably reached the end point of their early evolution and finished accreting material. In summary, about two-thirds of the systems were consistent with the disk fragmentation theory and one third was inconsistent with it. The results show that the disk fragmentation mechanism is an important one but probably not the whole story, and a larger sample should help constrain the processes even further.
[[How do stellar binaries form?]]
usually an agressive motivated vicarious Stellar organizes a small group of supporters who then decide to rule the universe and make them pay dues
Usually it starts with drinks and a nice dinner.
Now I submit to fellow Freepers a question. How liable are we to find a planet inhabitable by advanced life orbiting a binary star system? I'd submit to you that the tectonic activity on such a planet would render it unsuitable (though we do need a limited amount of tectonic activity). Plus, the ever discussed "goldilocks zone" for water becomes harder to achieve. (Though liquid water is only one of many requirements for a habitable planet.)
Thus I submit to you that the knowledge that most stars our sun's size or larger are binary stars is yet further evidence that a Great Designer made the system we live in. I'm simply not religious enough to be an atheist.
“How liable are we to find a planet inhabitable by advanced life orbiting a binary star system?”
Don’t say “we”. If you find it, you’re liable for it, not me!
Do you think Copernicus' mom ever screamed at him, "When will you realize the sun does not revolve around you?!"
*ping*
One question being asked right now is whether our own Solar System has a very faint and small brown dwarf star orbiting our Sun at a distance beyond the Oort Cloud. We won’t be able to find out until the James Webb Space Telescope is launched in 2020. If confirmed, that could explain the occasional orbital changes with Neptune, Pluto and the recently discovered “mini planets” even further beyond.
Some years ago, if not still?, some thought the Sun might have a distant companion ("Nemesis") which was responsible for periodic mass extinctions on Earth, the idea being the companion would periodically stir up comets in the Oort Cloud, sending some toward the inner solar system and Earth.
I see whut you did there. ;-D
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