Beyond Our Solar System - 1
Beyond Our Solar System (BOSS)
Our Sun and its system of planetary bodies are not alone in the universe. Since 1995, astronomers have discovered more than 370 planets in orbit around other stars.
Most of the stars with planets are similar in size to our Sun. Several of these stars have more than one or two planets orbiting them. Since our Sun is a fairly typical star in the Milky Way galaxy, one would expect that other planetary systems would be common. Planets that exist around other stars are called extra-solar planets or exoplanets. Part of the enormous attraction of searching for exoplanets is the possibility that some of these new-found worlds will be able to support life.
Detecting exoplanets
Astronomers detect planets around other stars by a number of methods. One method involves accurately measuring changes in the intensity of light coming from a star as a planet passes in front of the star (the transit technique). If such changes are regular, then it is likely a planet is orbiting the star. Another method involves an accurate analysis of the motion of the star – a wobble in a star’s motion could be caused by the gravitational pull of its planets. Astronomers also use spectral analysis to detect exoplanets. An exoplanet’s properties are determined by combining information about a planet’s brightness, colour, spectral properties and the variability of these over time. Detection of planets around a distant star is extremely difficult from Earth because the intense brightness of a star tends to block out any planets. Very high resolution instrumentation is needed to separate the planet from its parent. Most of the known exoplanets have been discovered using Earth-based telescopes, but astronomers also use space telescopes (that is, those in orbit above Earth’s atmosphere).
Most of the exoplanets astronomers have already discovered have been around stars similar to our Sun. It is estimated that at least 12 percent of sun-like stars have planets orbiting them. Most known exoplanets are also ‘giant’ planets, typically as large or larger than Jupiter. The difficulty of detecting exoplanets means that current techniques are suited to discovering large exoplanets very close to their parent stars.
September 11th, 2009 at 7:22 am
Is one method or another better at discovering multiple planets in a system? It would seem, with our own solar system as a model, that gravitational effects on a star would be rather complex with many bodies in orbit. When an astrophysicist states a planet has been found around a star, would their results infer this is the only orbiting body affecting the star? And does these observations rule out the existence of other significant gravitational forces?
July 25th, 2010 at 7:10 pm
excellent information.