Scientists Discover Record Fifth Planet Orbiting Nearby Star

Astronomers have recently discovered a fifth planet around the star 55 Cancri. This star lies 41 light-years away (or 12.6 parsecs) towards the constellation of Cancer, the Crab. 55 Cancri is a binary star system with one star being a G-type star (the same as our sun) and the other being a red dwarf. The image to the right is an artists conception of what a planet around 55 Cancri might look like.

There are multiple methods for discovering extrasolar planets. The main methods for detection are astrometry, radial velocity (or doppler spectroscopy), pulsar timing, transits, gravitational microlensing, circumstellar disks, and direct imaging. The fifth star around 55 Cancri was discovered using the radial velocity method. In this method, one looks for doppler shifts in the spectrum of the star to determine whether or not there is an orbiting planet(s).

The planet, which was discovered by astronomers at San Francisco State University, University of California (Berkeley), and a team of other collaborators, is about 45 times the mass of the Earth and could be similar to Saturn (in terms of composition and appearance). It is the fourth planet from the star and has an orbital period of 260 days (or about .71 Earth years). Located in the habitable zone, a region of space where conditions are favorable for life, the planet lies 116.7 million kilometers (or .78 AU [where Earth is 1 AU away from the Sun]). The image to the left shows the 55 Cancri system on top and our own solar system (for comparison) on the bottom. The green areas in the pictures depict the location of the habitable zones in each system.

Thus far, all the planets discovered around 55 Cancri are gas giant-like planets ranging in size from Neptune to larger than Jupiter. These planets have nearly circular orbits with a Jupiter like planet orbiting at nearly the same distance as our Jupiter. These findings, along with others like them, leave hope for finding Earth-like planets around other stars and life elsewhere in the galaxy.

I think that finding planets around other stars is always a good thing. Finding more planets around stars allows us to get a better picture of how our own solar system formed and the evolution of solar systems in general.

NASA article:
http://www.jpl.nasa.gov/news/news.cfm?release=2007-128
Space.com article:
http://www.space.com/scienceastronomy/071106-five-planets.html