For much longer than the nine years Centauri Dreams has been in existence, I've been waiting for the announcement of a planetary discovery around Centauri B. And I'm delighted to turn the first announcement on this site over to Lee Billings, one of the most gifted science writers of our time (and author of a highly regarded piece on the Centauri stars called The Long Shot). Lee puts the find into the broader context of exoplanet research as we turn our gaze to the nearest stars, those that would be the first targets of any future interstellar probes. On Thursday I'll follow up with specifics, digging into the discovery paper with more on the planet itself and the reasons why Centauri B was a better target than nearby Centauri A. I'll also be offering my own take on the significance of the find, which I think is considerable. by Lee Billings For much of the past century, astronomy has been consumed by a quest to gaze ever deeper out in space and time, in pursuit of the universe's...

Continuing with what promises to be a seriously interesting week in exoplanet studies, I want to home in this morning on PH1, a planet that reminds us how much the public has become involved in ongoing science thanks to the widespread distribution of computer power. As presented at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno (NV), the finding pairs volunteers working with the crowdsourced Planet Hunters project with an international team of professional astronomers led by Yale University's Meg Schwamb. The volunteers -- Kian Jek of San Francisco, California, and Robert Gagliano of Cottonwood, Arizona -- were the first to spot the telltale lightcurve of a transit, which was then confirmed by astronomers using the Keck instruments at Mauna Kea (Hawaii). What the investigation uncovered was a gas giant about 6.2 times the radius of the Earth, putting it into Neptune-territory. But what really flags the attention is the fact that...

Because it's going to be an interesting week for exoplanet studies (for reasons I'll talk about soon, though not today), I'll lead off with some thoughts on eta-Earth, defined as the fraction of Sun-like stars with a planet like Earth orbiting them. We have a lot to learn about the frequency of terrestrial worlds, and as Philip Horzempa points out in a recent article for The Space Review, the image that's gradually emerging is of fewer 'Earths' than Carl Sagan once estimated when he said in the 1980s that half of all stars could have a planet like our own. Image: Artists' concepts of small exoplanets compared to our own planets Mars and Earth. As Kepler continues to hunt, how can we move beyond its findings to learn more about terrestrial planets around much closer stars? Credit: NASA/JPL-Caltech With Kepler's continuing datastream and improving ground-based instrumentation, we're learning more about planet distribution, but Horzempa notes that even now, estimates of Earth analogs...

Gliese 581d seems more and more to be considered a habitable zone planet, as Siddharth Hegde (Max Planck Institute for Astronomy) and Lisa Kaltenegger (Harvard-Smithsonian Center for Astrophysics) describe it in a new paper. They're homing in on how to characterize a rocky exoplanet and point to HD 85512b and Gliese 667Cc as well as Gl581d as examples, but they also assume that we'll be seeing more and more habitable zone worlds as the Kepler mission continues its work, so how we learn more about these planets becomes a big issue. In the absence of missions like Terrestrial Planet Finder or ESA's Darwin, which would allow us to analyze an exoplanetary atmosphere for biomarkers, what else can we do to find the places where life exists? Hegde and Kaltenegger look hard at a planet's color to find the answer. Specifically, they're interested in what's known as a color-color diagram, which takes advantage of the fact that an object can be observed at a variety of wavelengths, with a...

New findings from the Herschel space observatory demonstrate how effective the infrared telescope can be at teasing out details of distant planetary systems. At issue is the system around Beta Pictoris, a young star (12 million years old) some 63 light years from the Earth. We’re looking at planetary system formation in progress here, with a single gas giant planet and a dusty debris disk that may be the forerunner of a disk much like our own Edgeworth/Kuiper Belt, the collection of icy bodies that orbits outside the orbit of Neptune. Ben de Vries (KU Leuven) is lead author of the paper on the new Herschel data, which examines the composition of dust in the outer regions of the Beta Pictoris disk. The study, reported today in Nature, presents a photometric and spectral analysis of dust particles produced when planetesimals in this region collide. The key player here is olivine, a mineral associated with protoplanetary disk material around newborn stars. The olivine found around Beta...

Super-Earths are exciting finds. The more of them we discover, the more likely it seems that life is abundant in the cosmos. But new work examining the viscosity and melting temperature of mantle rock is casting a different aura over super-Earths. Rather than being planets much like the Earth but simply more massive -- worlds characterized by thick atmospheres, plate tectonics, volcanic activity and magnetic fields -- they may differ in fundamental ways. With internal pressures tens of times higher than those found in Earth's interior, large viscosities and melting temperatures could have adverse consequences on the planet's habitability. The potential effects extend as far as the core of the planet, which may not even exist. In a presentation at the European Planetary Science Congress on September 26, Vlada Stamenkovic (Massachusetts Institute of Technology) noted that the average super-Earth may in fact be undifferentiated; i.e., it may not have separated into a metallic core and a...