Artist's concept of a rocky planet in orbit around a distant star. Click on image for full size (201 Kb) NASA, ESA and G. Bacon (STScI)

The star and its planet orbit a common center of gravity. The planet moves in a wide orbit, while the star just appears to wobble slightly. By measuring the Doppler shift from the spectrum of the star, scientists can detect the tiny motion caused by the planet. Most of the distant planets were discovered using this technique.

If we are lucky enough to be lined up properly with the planet's orbit, it can occasionally pass in front of the star, blocking out some of the light that we usually see from the star and briefly making it appear dimmer. It's like a solar eclipse, but the planet only covers a small fraction of the star. Only a few of the planets outside of our solar system pass in front of their stars.

All of the distant planets are much too far away to resolve directly. We can only see their effect on the star that they orbit.

Artist's concept of a rocky planet in orbit around a distant star. Click on image for full size (201 Kb) NASA, ESA and G. Bacon (STScI)

The star and its planet orbit around each other. The planet moves in a wide orbit, while the star just appears to wobble slightly. By measuring the Doppler shift of the light coming from the star, scientists can detect the tiny motion caused by the planet. Most of the distant planets were discovered this way.

If we are lucky, some of the planets can pass in front of their star. This blocks out some of the light that we usually see from the star, briefly making it dimmer. It's like a solar eclipse, but the planet only covers a small part of the star. Only a few planets outside our solar system pass in front of their stars.

All of the distant planets are too far away to see directly. We can only see their effect on the star that they orbit.

Artist's concept of a rocky planet in orbit around a distant star. Click on image for full size (201 Kb) NASA, ESA and G. Bacon (STScI)

The star and its planet move around each other. The planet moves in a wide orbit. The star just wobbles slightly. This causes a Doppler shift of the light. Most of the distant planets were discovered this way.

Some of the planets pass in front of their star. This blocks out some of the light. It makes the star look dimmer. It's like a solar eclipse. The planet only covers a small part of the star. Only a few of the planets pass in front of their stars.

All of the new planets are too far away to see directly. We can only see their effect on the star that they orbit.