how do they know that?
planets beyond the solar system
are there planets going around other sun? are there other solar system? planets located outside our solar system are known as extra solar planets.
it isn't easy to find planets around other suns. planets are very small compared with stars and usually have less than one-billionth the brightness. Still, it is possible to find planets orbiting other stars.
today, powerful telescopes may be able to detect other extrasolar planets if they are large enough.
planets have a gravitational effect on stars the same way that stars have a gravitational effect on planets. planets cause a star to wobble. telescopes can detect this wobble. using this method, a planet was discovered in orbit around the star 51 pegasi in 1995. more than 300 extrasolar planets have been discovered so far.
thinking critically
why are planets that orbit other stars called extrasolar planets?