How do scientist determine a year in a binary system?

Question

If a planet is orbiting a two star system how do scientists figure out what length of time is a year for that planet?

Answer 1

The planet will be orbiting a common center of gravity, which may be a point between the two stars. The total time to orbit this common center will be the planets year.

It's also possible that the planet would only be orbiting one of the stars, in that case the year is determined in the standard fashion.

Answer 2

funny how useless the entire mayan calander is once you leave earth.

if its a binary star system, all its planets would still orbit the binary systems center of mass. the year for a planet of a binary star would be unaffected, it would still be the time taken for the star to orbit the sun's.

for a binary planet system (similar to pluto except pluto isnt a planet) the planets would be in orbit around each other. they would still orbit their star normally. its jsut you would see the binary planet systems center of mass sitting on the orbit and not either of the planets themselves. The only reason you'd have wacked out days is if the planets orbited eachother in a different period from which they rotate. If they are tidally locked, it would seem normal, if they weren't and their orbit period around eachother was different than each's rotation period, well you'd have one planet with extended days and the other planet with shortened days.

Answer 3

So far, no planets have been observed in binary systems, so the issue has not come up. When astronomers report the period of an exoplanet, they are talking about its sidereal year, its revolution time relative an external reference. It would take more information about the planet than we can currently discern to estimate the tropical year (time between equinoxes) such as we use to define the Earth year. I think you should be able to define a sidereal year relative to the system's barycenter, assuming a non-chaotic orbit. It is possible that the tropical year in a binary system might vary depending on where the stars are in their orbits.

Answer 4

That would probably be determined by how it orbits those stars.

Does it orbit both? Then it becomes an easy question to resolve. It is still an orbit.

If it orbits only one, then you also have your answer.

However, if their is a convoluted orbit, sometimes one, or both or switching stars in it's orbit, then that is a question that shall go unanswered by me.

Answer 5

interesting. lets check it out.......

http://en.wikipedia.org/wiki/Binary_star#Planets_around_binary_stars

PSR_B1620-26c
is the first planet found in a binary system.
http://en.wikipedia.org/wiki/PSR_B1620-26c

researching....

http://en.wikipedia.org/wiki/Image:2003-19-e-large.jpg

looks like they do it like we do it with our sun.

The planet orbits at a distance of 3400 million km, a little larger than the distance between Uranus and the Sun.
Each orbit of the planet takes about 100 years.

http://upload.wikimedia.org/wikipedia/en/4/4f/TatooineSuns.jpg