First Image of a Planet Orbiting a Sun-Like Star 131
Several readers including houbou and DigitumDei sent links to what may be the first-ever image of a planet orbiting a sun-like star (research paper). The giant planet, the mass of 8 Jupiters, orbits its star at 330 AU, or 11 times the distance to Neptune's orbit. If the imaged object does turn out to be a planet — and it's not certain it is — then theories of planet formation may have to be adjusted. "The bulk of the material from which planets might form is significantly closer to the parent star... The outermost parts of such disks wouldn't contain enough material to assemble a Jupiter-mass planet at the distance from the star... at which the Toronto team found the faint object."
First? (Score:5, Interesting)
This [wikipedia.org] is no longer the "first" directly observed extrasolar planet? What value of "first" is are we using now?
Re:Planetary Science (Score:3, Interesting)
The short version, IIRC goes something like this:
* Star forms. The remaining disk around the star consists mainly of grains of dust, which slowly clump together under their own gravity.
* As clumps get bigger, they create a gravitational "wake" of particulates in the vicinity of their orbit. The wake closer to the star orbits faster and therefore its mass provides a "forward pull" on the object, whereas the part of the wake farther out orbits more slowly and provides a "rearward pull" on the object. The disk gets bigger as you go out (geometry!) and therefore there is more material in the outer half of the "wake," so the "rearward pull" is stronger than the foreward pull. This slows the object slightly and causes it to spiral inward towards the star.
* At a certain distance from the star (the "snow line") water ice converts to water vapor and the "rearward pull" on our orbiting object goes away. (I'm still not clear on why this is the case, BTW.) So inward-spiraling objects tend to stop at the snow line, and this is where a gas giant planet is most likely to form.
* Jupiter's wake at the snow line leads to the formation of Saturn as Jupiter's large mass starts throwing nearby things into a higher orbit.
* "Ice giants" like Neptune and Uranus can't grow as big as Jupiter because their local environment is depleted as they formed later than Jupiter & Saturn and mostly benefitted from more throw-offs by Saturn.
So to see an 8-Jupiter-mass gas giant orbiting 330AU from a sunlike star seems extremely unusual and it ought to imply that it was ejected into a higher orbit by something else because there's no reason for it to form there.
Again, IANAastrophysicist or planetary scientist, but I really get off on this stuff.
Re:Theories of planet formation may have to be adj (Score:5, Interesting)
1) In the 1700's some French guy starts a list of objects that are in the sky that resemble comets, but are not. They are assumed to be relatively nearby objects. One has the name M31.
2) In the early 1900's some American guy comes along and looks a little closer at those objects, and finds not only are they not nearby, but they are entire islands of stars, and we live in one of those islands too! And M31 ends up being over 2 million light years away.
3) In the later part of the 20th century, an astronomical space based telescope, discovers the background variations in the left overs of the big bang, that led to the eventual location of these things now called 'galaxies'
Charles Messier, Edwin Hubble, and the COBE satellite would like to have a discussion with you about the scientific method.
In other words, yes. The theories on planet formation will change the larger the sample size gets. Just the same way the awareness and eventual theories of galaxies changed as they were observed more often and became part of a larger sample size - the known visible universe