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."
Re:First? (Score:5, Informative)
Comment removed (Score:5, Informative)
Re:Obligatory (Score:5, Informative)
... that's no moon ...
We've already established that. It's a planet.
Re:Planetary Science (Score:3, Informative)
I meant that Neptune was 1/10th the distance as this object. Yeah, I screwed up here. Thanks for pointing that out.
Re:Where's the orbit? (Score:2, Informative)
Yes, assuming the object is orbiting the star, and using some quick and very dirty calculations based on information in the article, it has an orbital period of between 6 and 7 thousand years. Even if we were viewing at a right angle to its orbital trajectory it would take years to see it move at all and many more to determine its orbit with any certainty.
Re:Gemini Telescope and guide stars (Score:5, Informative)
Just to flesh this out and offer a few corrections, as someone who works around the AO LGS at Gemini (and Keck):
Tomduck is correct that an adaptive optics (AO) system uses deformable optics to bring a guide star into sharp focus, and the rest of the scene with it. He fails to mention that this process is in no way inherently dependent upon the use of a laser. Indeed, when a bright natural star is close enough to the target to be used, it is in many ways preferable to using the laser. (For one, the brightness of natural stars tends to be pretty constant, and not subject to the usual game of "so, how many watts shy of nominal power are we tonight?" :) So Gemini's AO system, Altair (read all about it here [harvard.edu]) is quite often used with natural guide stars (NGS).
A NGS can, incidentally, also be used for guiding - keeping the telescope pointed correctly - as its name implies. This isn't the case for a laser guide star (LGS), which in fact has absolutely no use for pointing, since the laser is fastened to, and aligned with, the telescope. It's a horrible misnomer. :( LGS come into play because the field of view of large (8-10m) telescopes is narrow enough that NGS are frequently not visible at the same time as science targets.
There are three large telescopes on Mauna Kea with LGS capabilities - Keck II has an older-technology sodium dye laser (pumped/amped by about six YAGs), Gemini has a solid-state (crystal) laser, and I'm not certain what Subaru has as I haven't worked with them yet. The W.M. Keck Observatory has funding to put a laser on Keck I also, but I'm unsure when it'll be operational. All of the lasers propagate at around 589nm for sodium fluorescence (this is coincidentally about the same frequency put out by the low-pressure sodium streetlights used in the towns on the island, so astronomers can pretty much ignore this frequency).
Each beam is about 8-12W with an objective lens diameter of typically 30-50cm, spreading a little as it goes up. Not enough power to punch holes in stuff, but enough that the FAA requires aircraft spotters to be positioned outside each observatory to make sure they don't blind the pilots of flights between the west coast and Australia/New Zealand. I've done this work sporadically since 2005 at Keck and 2006 at Gemini, so I have tons of pictures and time-lapse video... here's one [lava.net] of the Gemini beam with me ruining the picture by sitting in front of it.
Along with the FAA, AFSC (that's Air Force Space Command, not the American Friends Service Committee) is rather particular about us not shining the bright lights into the sensitive sensors of keyholes and such things. We look up, they look down, etc.
By the way, if there are any Farkers on the Big Island of Hawaii who think this kind of work sounds like fun, it looks like Keck has openings [keckobservatory.org]. It's temp-agency work, and probably the coldest, highest-altitude temp-agency work you'll ever get...
Re:So what planets have we seen (Score:1, Informative)
The majority of extra-solar planets so far discovered have been massive, extremely close orbitting bodies; so called 'hot-jupiters', usually 10-20x the mass of our own Jupiter, so they're verging more on being Brown Dwarves than planets.
The reason for this is that the primary way of discovering an extra solar planet is by measuring the orbital perburbation that the planet causes on it's parent sun - the star seems to wobble or oscillate as it tracks. The secondary way is to measure the change in instensity of the star as a (large) planet passes in front of it relative to us and occludes it.
Smaller planetary systems, or a planet further from the star means less orbital wobble. Less orbital wobble means that it falls beneath the resolution of the instrumentation in use. Gets lost in the noise basically.
NB - Orbital wobble is most observable if the stellar disc is perpendicular to our observation. In contrast, occlusion only works if the orbital disc is directly in line with our line of observation. Cases where the disc may be offset by 5-15 degrees will be commensurately harder to detect since the observed wobble is a lot lower. (this is potentially a majority of systems, since our galaxy is basically planar and star system formation could echo this planarity of orientation)
Initial planetary discoveries were big, bright stars with massive, close-orbitting planets because these are the easiest to distinguish from noise. As we get better instrumentation (primarily orbital telescopes or Very Large Arrays with better noise elimination algoritims) our ability to 'see' smaller, more earth-like planets improves.
We're still a long way from seeing an Earth Equivalent, but seeing an orbital body around an 'earth-like sun' is a major step forward.
Re:So what planets have we seen (Score:3, Informative)
This one: http://blogs.discovermagazine.com/badastronomy/2005/04/29/first-exoplanet-imaged/ [discovermagazine.com]
It orbits a brown dwarf. A very non-sunlike star.
Re:First? (Score:3, Informative)
Nope. There have been a few false positives, but there have been plenty of 'confirmed' sightings of extra-solar planets.