The Sun Had Sisters 155
[TheBORG] writes to mention a Space.com article about the Sun's departed solar siblings. Our own medium-sized yellow star was far from alone when it was formed, with hundreds of fellow solar bodies and a supernova to keep it company. From the article: "The evidence for the solar sisters was found in daughters--such as decayed particles from radioactive isotopes of iron--trapped in meteorites, which can be studied as fossil remnants of the early solar system. These daughter species allowed Looney and his colleagues to discern that a supernova with the mass of about 20 suns exploded relatively near the early Sun when it formed 4.6 billion years ago; and where there are supernovas or any massive star, you also see hundreds to thousands of sun-like stars, he said. The cluster of thousands of stars dispersed billions of years ago due to a lack of gravitational pull, Looney said, leaving the sisters 'lost in space' and our Sun looking like an only child ever since, he said."
lack of gravitational pull?? (Score:3, Interesting)
Dearly Departed (Score:4, Interesting)
How does that work? These stars are the gravitational pull, local "depressions" in the spacetime fabric that bend space around them towards themselves. Which is gravitational pull. Which must be overcome by some other force, either other gravitational pull from some other, larger/closer mass(es), or momentum from a kinetic event like a collision. Maybe the exploding supernova knocked them out of the area. Maybe, if it was big enough, its departing mass would have not only knocked the stars away, but pulled them away, overcoming their mutual gravitational attraction through greater departing, but still attractive, mass.
But something did. That's the biggest missing factor in this whole proposed scenario, in Robin Lloyd's Space.com story about it at least, that it needs to hold it together. Theories fall apart because of a lack of gravity, star clusters not so much.
Was One Named Nemesis? (Score:5, Interesting)
Re:Huh? (Score:5, Interesting)
I'm pretty sure that's not true. Remember: the larger the star, the shorter its life. Really large stars have lifetimes of just a few tens of millions of years, while red dwarfs can live trillions, according to current theory. While a 20 solar mass star isn't that big, I imagine it still didn't last long.
The actual paper, if you want to read it (Score:5, Interesting)
Re:Dearly Departed (Score:3, Interesting)
Yeah, or it was something else. There are about a billion things that could have prevented the star cluster from being stable. I was merely presenting the simplest and most obvious one, just as an example. Your post implied that it seemed implausible that a star cluster could fly apart, and that without this crucial piece of information you refused to believe the conclusion that there was in fact such a cluster -- "Theories fall apart because of a lack of gravity, star clusters not so much." Which isn't true. Star clusters fall apart all the time due to lack of gravity, so asking "why?" makes a poor fulcrum for doubting the findings described in the article.
BTW, while the energy of the nova may have contributed to pushing stars out of the cluster, it is doubtful to me that the gravity of the escaping mass did, since it would necessarily be a relatively small amount of mass near enough to effect any particular star. The mere fact of it no longer being concentrated within the cluster would have a much larger and immediate effect on the trajectories of the other stars.
Re:Dearly Departed (Score:3, Interesting)