Tatooine's Double-Sunset a Common Sight

anthemaniac writes "Thirty years ago, Luke Skywalker beheld something that scientists are just now realizing is likely quite common in the universe: double sunsets. Astronomers have long known that binary star systems are common. And models suggested that planets could form in these systems, even though there's a double-tug of gravity on the material that would have to form a planet. Observations from NASA's Spitzer telescope, show that binary systems are just as likely to be surrounded by planet-forming debris disks are are lone stars."

Comments

It wasn't thirty years ago...

[xxxJonBoyxxx]

Thirty years ago, Luke Skywalker beheld something that scientists are just now realizing is likely quite common in the universe: double sunsets.

Luke didn't see the sunset thirty years ago - he saw it "A Long Long Time Ago (in a Galaxy Far Far Away)..."

I can't believe I'm posting to a Star Wars item...feel like I need to take a shower now.

Two is Better than One

[AaxelB]

Trilling and his team looked for disks in 69 binary systems between 50 and 200 light-years away from Earth. All the stars are more massive and younger than our middle-aged Sun.

Better endowed and younger, eh? And you can have two at once? Maybe we'd better rethink our exclusive orbit with our Sun... After all, we just keep going in circles.

what about a double-sunset + life?

[dmoen]

Planets may be common in binary systems, but what about planets that support life?

One of the reasons that Earth can support life is that the distance between the earth and the sun remains close to a constant for the duration of Earth's orbit around the sun, so the Earth receives a fairly constant amount of solar energy. This means, for example, that the temperature doesn't go down to -200 in the winter and up to +800 in the summer.

But in a binary system, I would imagine that orbits that provide a constant amount of solar energy in the Earth-normal range would be less likely to occur. (What would such an orbit look like when there are 2 suns?) Are there any astrophysicists out there that can comment on this?

Doug Moen

Re:Planetary Orbit?

[Lars T.]

How would the planet orbit them though?

Would it have to be far enough away so they appeared as one, or go into some crazy chaotic close orbit? Look at the image in TFA. Either the stars are closer than 3 AU, then the planet(s) circle around them both, or they are farther away than 50 AU, then the planet(s) circle one of them (it doesn't mention if there could be planets about both, but IMHO that's also possible). In between, no planets will form.

Re:Planetary Orbit?

[cswiger]

There are two stable possibilities: where the two stars orbit each other fairly closely (ie, 0-4 AU from the article, IIRC), and planets then orbit the common center of gravity formed by these two stars...or where one star has a very distant orbit, which is so far that it doesn't disrupt planets close in to the bigger primary.

If the second binary star is in a medium-sized orbit (ie, somewhere between where Jupiter and Pluto are in our system), it seems to be the case that this disrupts the planet-forming disk of gas so much that no planets are likely to form.

If you want to see a full list of all known exoplanets, go here: http://exoplanets.org/planets.shtml
The column marked "a (AU)" is orbital radius, where 1 AU is the earth's distance from the sun.