Winking Star Decoded as Root of Planetary System

sam1am points out a New York Times report on a recent paper published in Nature about the formation of planetary systems. A binary star system surrounded by a protoplanetary disc was observed over a period of six years by scientists at Wesleyan University. The orbit of the stars around each other caused changes in illumination from within the disc and allowed the researchers to learn a great deal about its composition. Some of the basic data is posted on the university's site. An animation of the system is also available. From the NYTimes: "'This is the first step in going from smoke particles to macroscopic things like planets and asteroids,' Dr. Herbst said in an interview, noting that these grains were about the same size as those found in many meteorites. Observing starlight reflected from these grains, he said, represented a rare opportunity to study the structure and chemical properties of material in the inner parts of another planetary system."

Comments

Wow, those stars are moving fast

[Anonymous Coward]

The diagrams shown must vastly underestimate the difference in distance from the stars to the surrounding ring. Stars moving that fast and with that large of a radius would quickly gravitationally shred the ring if it was as close as shown.

Now the question is how this disc formed around two stars with such high inclinations relative to it. The typical nebular collapse theory isn't going to work here due to the conservation of angular momentum. Could one of the stars have traveled through a dense nebula or had a multi-body interaction with a recently formed system thus starting this odd system? And if so then wouldn't these results be of a hybrid system and not necessarily representative as the missing gap that the article claims? With two stars with such high inclinations, high velocities, and large major axes, no inner planet is ever going to form and the source of this dust probably isn't from a single nebular collapse. I certainly don't think it has a definitive connection to our solar system formation.

1mm objects at 2400 light years

[MosesJones]

Now this is the sort of thing that makes me take my hat off to science. These chaps, who probably still lose their car keys down the couch, have managed to identify objects of a 1mm size at a distance of 22,705,268,200,000,000,000 meters (14108399600000000 miles). Now obviously they are using analysis and not just "seeing" the dust but that truly is a gobsmaking achievement.

Of course now the bible literalists can jump up and say "see we are made from dust" but hell that can only lead to interesting conversations....

Re:1mm objects at 2400 light years

[Random Walk]

First, it's actually easier to detect smaller particles. Surface scales as radius squared, mass as radius to the third power, thus with smaller particles you get much more (absorbing or reflecting) surface per mass.

Second, the author's results depend on whether their particular model geometry for the binary system + disk is correct.

And third, in their Nature paper they argue that they most likely are biased towards the smallest grains that make up the circumbinary disk, and that the bulk of the disk may be in even larger grains ('pebbles'). For the same amount of occultation, that would require much more mass (see first point). I wonder whether that wouldn't result in an insane mass for the disk ... they don't discuss this ;-)

Re:Earth-like??

[SquirrelsUnite]

It depends on their distance. The problem isn't so much that a planet would get ripped apart (it would have to be pretty close for that) but that if the two stars are too close than any orbit in the habitable zone would be unstable. There are basically two ways to have stable orbits in a binary system in the habitable zone. In the first case the stars are very close to each other and the planet orbits both of them. In the second they are fairly distant and the planet is in orbit around one of them. It doesn't have to be a huge distance either, Alpha Centauri A and B are 11 AU from each other at their closest approach, yet an Earth sized planet could have formed and be stable in the habitble zone around either of them.