How do astronomers detect that a star has a planet orbiting it?
It is amazing what human ingenuity can come up with! In this case, you have thousands of astronomers peering at the heavens every night using a relatively small set of tools ( telescopes gathering light or radio waves ), so they spend a great deal of time thinking of different ways to use these tools. To be able to sense objects as small as a planet at a distance of trillions of miles using these tools is a major accomplishment. You can understand what astronomers are doing if you think about our own sun and the planets that orbit it. The largest of these planets is Jupiter. Jupiter weighs about one-thousandth of what the sun weighs, and it orbits the sun every 11.8 years or so at a distance of 5 astronomical units (AU, the average distance between the Earth and the sun, which is 92,955,800 miles or 149,597,870 kilometers). The sun is not anchored in space with Jupiter orbiting around it. As Jupiter moves around the sun, Jupiter pulls on the sun and moves it. The distance it pulls the
