NASA - National Aeronautics and Space Administration

We may be closer to answering the question, "Are we alone in the Universe?" Research that was funded by NASA and the National Science Foundation has gotten us closer.

Image to left: Artist's concept of extrasolar planet. Image credit: David A. Hardy, astroart.org (c) pparc.ac.uk

Astronomers have found two more planets that are outside our solar system. Because they are outside of our system, they are called extrasolar planets.

This is not the first time that astronomers have found extrasolar planets. The two most recently found planets are about the same size as Neptune. They are about 10 to 20 times larger than Earth. These newly discovered planets are much smaller than planets found before. Planets found up until this point were considered "gas giants" like Jupiter.

Because these two planets are smaller than Jupiter, they may be made of rock or both rock and ice instead of gas. They may have formed in the same way that Earth did. They were found by astronomers from three universities.

Stand by Your Star

Both of the newly found planets orbit closely to their parent stars. One of the planets orbits the star Gliese 436. It orbits every two and a half days. This star is in the constellation Leo. It is a star that is smaller than our own Sun. It is only 30 light years away. A light year is the distance light travels in a year. That is about 9.5 trillion kilometers (5.8 trillion miles.)

Image above: The two newly found planets are larger than Earth but smaller than Jupiter. Image credit: NASA

The second planet orbits the star 55 Cancri in less than three days. It is 41 light years away in the constellation Cancer.

Both planets are very close to their stars. They are even closer than Mercury is to our Sun. Mercury is about 58 million kilometers (36 million miles). The first planet is 4.1 million kilometers (2.6 million miles) from its star. The other is about 5.6 million kilometers (3.5 million miles) from its star.

Both of these planets were found using radial velocity. This method measures the slight changes in the position of a star as a planet's gravity pulls on it. It makes the star seem to wobble.

Looking for Planets in All the Right Places

NASA will launch a series of planet-hunting missions over the next 15 years. These missions include Kepler, the Space Interferometry Mission (SIM) and Terrestrial Planet Finder (TPF). They are looking for Earth-like planets. Planet hunters have found nearly 140 planets outside of our solar system.

Image to left: An artist's idea of how the TPF will look. Image credit: NASA

The Keck Interferometer will combine the light of the world’s largest optical telescopes. It will study dust clouds around stars where planets may be forming. The Keck telescopes are already working in Hawaii. The Kepler Telescope will search for proof of Earth-like planets. The SIM will help us find planets that are slightly larger than Earth. TPF will send back photographs of nearby planetary systems. It will have an imaging power 100 times greater than that of the Hubble Space Telescope.

Keep Looking

Although the planets we have found so far are unlikely to support life as we know it, we will keep looking. There may be planets out there that are very similar to Earth. We will study the atmospheres of these distant worlds. We will look for carbon dioxide, water and ozone. If there are a lot of these gases on a planet, there is a good chance that there is life. A discovery such as this would let us know that we probably are not alone.

Adapted from Scientists Discover First of a New Class of Extrasolar Planets and Planet Quest Overview