≡ Menu

Small, Rocky World Discovered by La Silla Observatory

A planet fourteen times the size of the Earth may not be all that small, but it’s tiny compared to the bulk of planets discovered around other stars, most of which are so-called ‘hot Jupiters’ — gas giants in tight orbits around their parent star. The European Southern Observatory’s La Silla telescope has now found a much smaller planet, and one that may well be rocky, a kind of ‘super Earth,’ as some researchers have said. But the new planet orbits the star mu Arae (about fifty light years from Earth) so tightly that it completes its orbit in less than ten days, making for temperatures that probably top 1000 degrees Fahrenheit.

You can read more about the mu Arae planet at Space.com, whose story quotes Alan Boss of the Carnegie Institution in Washington as saying, “It’s much closer to our solar system than anything we’ve found so far…I’m still somewhat stunned that they have such good data.” The star mu Arae is similar in size and brightness to the Sun, and the new planet seems to have roughly the mass of Uranus (it may, in fact, have been the rocky core of a gas giant that never fully formed). Making the discovery more strikingly like the Solar System is the fact that mu Arae seems to have two other planets, both apparently gas giants. Portuguese researcher Nuno Santos led the team that made the discovery.

As exciting as all this is, keep in mind that we’re soon going to be doing much better. NASA is launching two missions within the next decade to track down Earth-like planets. The Space Interferometry Mission in particular is worth your attention. It’s going to survey 200 nearby stars looking for planets with wet, rocky surfaces. The other mission, called Kepler, will use a photometer and the ‘transit method’ to find planets that pass in front of their home stars. We are mere years away from knowing how widely dispersed Earth-like worlds are, and which stars offer the most tempting targets for our first interstellar probes. As Berkeley planet-hunter Geoff Marcy told an interviewer last year: “With SIM, we’re going to survey about 200 nearby stars. The interesting problem we face is that we don’t know how many planets it’s going to find. It might turn out that every star has an Earth or a Venus or a Mercury or a Mars — a smallish planet heretofore undetectable. That’s the great part about SIM — we don’t know the answer ahead of time. We don’t know if we’ll find three planets or hundreds. We have to do the experiment to find out.”

Comments on this entry are closed.

  • ljk April 24, 2007, 14:00

    Finding Solar System Analogs With SIM and HIPPARCOS: A White Paper for the ExoPlanet Task Force

    Authors: Rob P. Olling

    (Submitted on 23 Apr 2007)

    Abstract: The astrometric signature imposed by a planet on its primary increases substantially towards longer periods (proportinal to P^2/3), so that long-period planets can be more easily detected, in principle. For example, a one Solar-mass (M_Sun) star would be pulled by roughly 1 mas by a one Jupiter-mass (M_J) planet with a period of one-hundred years at a distance of 20 pc. Such position accuracies can now be obtained with both ground-based and space-based telescopes. The difficulty was that it often takes many decades before a detectable position shift will occur. However, by the time the next generation of astrometric missions such as SIM will be taking data, several decades will have past since the first astrometric mission, HIPPARCOS. Here we propose to use a new astrometric method that employs a future, highly accurate SIM Quick-Look survey and HIPPARCOS data taken twenty years prior. Using position errors for SIM of 4 muas, this method enables the detection and characterization of Solar-system analogs (SOSAs) with periods up to 240 (500) years for 1 (10) M_J companions. Because many tens of thousands nearby stars can be surveyed this way for a modest expenditure of SIM time and SOSAs may be quite abundant, we expect to find many hundreds of extra-solar planets with long-period orbits. Such a data set would nicely complement the short-period systems found by the radial-velocity method. Brown dwarfs and low-mass stellar companions can be found and characterized if their periods are shorter than about 500 years. This data set will provide invaluable constraints on models of planet formation, as well as a database for systems where the location of the giant planets allow for the formation of low-mass planets in the habitable zone. [Abridged]


    A White Paper for the ExoPlanet Task Force: 7 pages


    Astrophysics (astro-ph)

    Cite as:

    arXiv:0704.3059v1 [astro-ph]

    Submission history

    From: Rob P. Olling [view email]

    [v1] Mon, 23 Apr 2007 18:42:10 GMT (22kb)