Before I get into today’s story, which is an interesting study on planets around white dwarfs that Andrew Tribick passed along, I want to say a few words about Japan. Centauri Dreams has many, many readers in that country, and the terrible images and stories coming out of there have haunted me these past few days. The suffering of those displaced by the earthquake and tsunami, and the continued problems in resolving the worsening situation at Fukushima, make it hard to focus on any other topic. Speaking for myself here at Centauri Dreams -- and I know I speak for the entire Tau Zero Foundation as well -- you Japanese readers remain in our thoughts and prayers, and will continue to do so until these great national wounds are healed. On the space front, today is the day when MESSENGER enters Mercury orbit. Below is the schedule for the events, which we’ll follow closely as orbital insertion occurs. White Dwarfs and Potential Planets But for now let’s talk about white dwarfs, those...

If by any chance you missed Lee Billings' recent work on BoingBoing, let me direct you to Cosmic Commodities: How Much is a New Planet Worth? Lee has been talking to planet hunter Greg Laughlin (UC-Santa Cruz) about the latter's equation that quantifies the worth of a given planet. It's an ingenious concept, one that accepts inputs like planetary mass, estimated temperature, type and brightness of the primary star, and generates a value in cash. Why do this? It's a way to measure the potential of an exoplanet to be interesting. or in Laughlin's terms, "a way for me to be able to quantify how excited I should be about any particular planet." Reasons to Go You can follow the genial and long-running musings on planetary value on Laughlin's systemic blog, but read Billings if you're not already familiar with the equation, because his interview with Laughlin walks you through all the parameters step by step. One of the interesting things about the equation is that the brighter the star...

Protoplanetary disks present huge challenges, but we need to learn more about them to make sense of our exoplanet catalog. We're interested in learning about the two primary theories of planet formation -- core accretion from colliding bodies of rock or ice and gravitational instability in the disks themselves. But protoplanetary disks are dim compared to their central star, and our studies thus far have been more or less limited to the outer envelope of the disk structure. What that means is that we're looking at a scale that's much larger than our own Solar System, not sufficient for the kind of detailed observation we'd like to make. Fortunately, we have technologies like coronagraphs, that can mask the bright light of the central star, and adaptive optics that can compensate for the blurring effects of the Earth's atmosphere. Now we have new images from the Subaru telescope in Hawaii, which is using advanced versions of both technologies in an instrument called HiCIAO (High...

When Geoff Marcy (UC-Berkeley) got started in the exoplanet game, it was the result of an apparent dead-end. As Marcy tells Wired.com in a recent interview, he had been working as a post-doc at the Carnegie Institute of Washington, feeling 'a little bit like an impostor' and wondering whether a career in science hadn't been a bad choice. But epiphanies happen in the strangest places. One afternoon he was taking a shower in Pasadena, and the rest is history: "So I thought, what do I care about? I would love to know if there were other planets around other stars. "This was a question that nobody was asking. It was 1983, and nobody was even talking about planets. Even our own solar system was considered boring at the time. "So by the time I turned off the shower, I knew how I was going to end my career. I quickly realized that this was kind of a lucky moment. By knowing that I was a failure, I was free. I could just satisfy myself, and hunt for planets — even though it was a...

The data from Kepler’s first 136 days of operation could not be more interesting. As discussed in yesterday’s news conference, we now have fully 1235 exoplanet candidates from Kepler’s transit observations, and it’s worth quoting principal investigator William Borucki (NASA Ames) on the significance of the results thus far: "We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone - a region where liquid water could exist on a planet’s surface. Some candidates could even have moons with liquid water. Five of the planetary candidates are both near Earth-size and orbit in the habitable zone of their parent stars." Statistical analysis by the Kepler team shows that between 80 and 90 percent of these candidates are likely to be real planets. Remember that the spacecraft is staring at 156,453 stars in a patch covering 1/400th of the sky, located in the constellations Cygnus and Lyra. What it’s giving us is a statistical sample of stars in a...

Last June Centauri Dreams readers were excited about the release of Kepler results, but miffed that so much of the most interesting material was held back for later release. Now we have the release of these data, and the first thing I want to do is direct you to Greg Laughlin's systemic site, where you can find a follow-up characterization flow chart to help work through systems of interest. Laughlin calls it a 'template for the treasure map,' and it's available in full here. What happens next? Laughlin (UC-Santa Cruz) notes the process: "Once the candidates hit the stands, there will be a rush to skim the cream, and a mobilization of follow-up observational campaigns to capitalize on the best opportunities in the data set." He also reminds us that the brighter the parent star, the better the chances for delving deep into its exoplanetary mysteries. We're in cream skimming time indeed, and we'll have plenty to talk about in coming weeks. We'll carry on tomorrow with thoughts on the...

The NASA news conference announcing the latest Kepler results will take place today at 1800 UTC (1300 EST) at NASA headquarters in Washington. You can follow the action live on NASA TV. The participants are: Douglas Hudgins, Kepler program scientist, NASA Headquarters, Washington William Borucki, Kepler Science principal investigator, NASA Ames Jack Lissauer, Kepler co-investigator and planetary scientist, NASA Ames Debra Fischer, professor of Astronomy, Yale University I'll hold today's main post until after the embargo on the Kepler news lifts.

The abundance of giant planets among the more than 500 exoplanets thus far identified is largely the result of our detection methods -- we can find larger planets far more readily than smaller ones. But even as we bring our detections down to ever more Earth-sized worlds, we can go to work on the questions that giant planets close to their star raise. Current thinking is that planets like these must have formed far from their host stars and migrated to their current locations. Still to be determined are the mechanisms at work to make migration happen. Intriguing new evidence is coming in from the National Astronomical Observatory of Japan, which has been working with data from the Subaru Telescope to study the orbital characteristics of two exoplanets, HAT-P-11 b and XO-4 b. The former, about 130 light years from Earth in the constellation Cygnus, shows a mass of 0.081 that of Jupiter, making it a Neptune-sized world in an eccentric 4.89-day orbit. The latter is a Jupiter-class...

We're exoplanet-minded around here, and any news from Kepler or CoRoT almost automatically goes to the top of the queue, but there are days when the visuals take precedence. Such was the case yesterday, when even as we learned about a small, rocky planet in Kepler's view, we also received the image below, released at the American Astronomical Society's 217th meeting. It's Hanny's Voorwerp, named for Hanny van Arkel, the Dutch teacher who discovered the celestial anomaly in 2007 while working with the Galaxy Zoo project. Here it's seen through the Hubble Space Telescope's Wide Field Camera 3 and Advanced Camera for Surveys, and what an image it is. Image: This bizarre object, dubbed Hanny's Voorwerp (Hanny's Object in Dutch), is the only visible part of a 300,000-light-year-long streamer of gas stretching around the galaxy, called IC 2497. The greenish Voorwerp is visible because a searchlight beam of light from the galaxy's core illuminated it. This beam came from a quasar, a bright,...

Last night's lunar eclipse is the first I've seen used as the hook for a story on exoplanets in the popular press, as it was in this Christian Science Monitor story yesterday. Maybe that's a sign that we're beginning to relate the familiar things we see in the sky to the distant and less well understood, placing ourselves in a larger, cosmic context. Or maybe it's just because the idea of extraterrestrial life sells well in Hollywood and people have gotten enthusiastic about the prospects that it might actually be out there on some distant world. Whatever the case, it's good to see exoplanet science in the newspapers again (and thanks to Erik Anderson for the tip on the CSM article). Eclipses and Exoplanetary Science Eclipses change what we see on the lunar surface as the Earth's atmosphere affects the color of sunlight passing through it. That's quite an interesting effect for astrobiologists, because studying the light reflected off the moon during an eclipse is a way for...

"With your help, we are looking for planets around other stars." So begins a first-time user's introduction to Planet Hunters, an online citizen science project that delivers exactly what many of us have been hoping for since the first Kepler results came in -- a chance to use our own computers to help analyze data taken by the mission. Kepler has been in operation for the better part of two years now, accumulating what Yale astronomer Kevin Schawinski calls 'another mountain of data to sort through.' What better way to sort than with distributed computing? Schawinski is a co-founder of Planet Hunters, and was deeply involved in the creation of the successful Galaxy Zoo project several years back. In the latter, the involvement of average citizens in astronomy took off, to the tune of hundreds of thousands of Web users sorting through a million images of galaxies and classifying them. Kepler presents its own challenges, monitoring almost 150,000 stars in the constellations of Cygnus...

Yesterday's successful launch of a SpaceX Falcon, and the subsequent safe return of the Dragon spacecraft after a three hour ride, puts an exclamation point on Dana Andrews' paper on space and commercial viability, which was discussed here yesterday. We're a long way from a sustainable space infrastructure -- many reports note the fact that what SpaceX did yesterday roughly parallels where humans were in space about fifty years ago, with the early Soviet and American flights -- but we are seeing the most promising signs yet of a viable launch business emerging from the commercial sector, with all that implies about eventual use of space resources and future colonization. Exoplanetary Puzzles Now we wait for news from NanoSail-D, whose sail deployment should, if my sources are right, be today, but the @NanoSailD Twitter feed has grown quiet. We'll think good thoughts and, while waiting, move on to the exoplanet hunt, the latest news from which is the discovery that the planet...

There's so much we still don't know about GJ 1214b. What we do know is this: The planet is 2.7 times the size of Earth and about 6.5 times as massive, orbiting its star at a distance of 0.014 AU. That's far too close to the primary to make this a habitable world, but a planet hardly has to be habitable to be interesting, and GJ 1214b becomes interesting indeed now that Jacob Bean (Harvard-Smithsonian Center for Astrophysics) has announced the first analysis of its atmosphere. Until now, we've been looking at exoplanet atmospheres only around larger worlds. Super-Earths are generally considered to range from two to ten Earth masses. To study this one, the researchers used the Very Large Telescope at Paranal Observatory (Chile) to examine the near-infrared (780 to 1000 nanometers) region of the spectrum. More work at different wavelengths will be needed to tease out GJ 1214b's secrets, but the progression in atmospheric observations to smaller planets is satisfying to see, as David...

I can't begin today's entry, which deals with an unusual planet indeed, without first mentioning the passing of Allan Sandage, a man whose work I have admired for my entire adult life. A protegé of Edwin Hubble, Sandage would refine the latter's findings, re-examining Hubble's distance measurements to galaxies like Andromeda and helping us fine-tune our estimates of Hubble's Constant, a measure of the expansion of the universe. In fact, our current estimate, 71 kilometres per second per megaparsec, is only slight off Sandage's 1958 result. A final paper, on RR Lyrae variable stars, appeared as recently as June, one of 500 papers the astronomer wrote. Astronomy Now has a fine obituary of Sandage, who died at the age of 84. Looking Back from the Future Maybe it's the death of Sandage that has me in a retrospective mood as I tackle a most unusual exoplanet story. All morning I've been remembering a passage from H.G. Wells' The Time Machine in which the time traveler has found his...

I had hoped to be able to cover the Hartley 2 flyby today, but I'm traveling on Tau Zero business and have to write this entry early. Instead, I'll at least keep the EPOXI mission focus by talking about the other half of this unique venture, an investigation of exoplanet systems. We can always talk about what the Hartley 2 encounter produced next week, but not before, as the schedule is crowded and I doubt I'll be able to get an entry posted here at all on Friday. Remember that the Deep Impact spacecraft that visited Tempel 1 in 2005 is now on an adventuresome extended mission called EPOXI (although the spacecraft, confusingly enough, still retains the original 'Deep Impact' name). The spacecraft was reawakened in the fall of 2007 and directed to a flyby of the Earth for a gravitational assist that would put it into a heliocentric orbit for the Hartley 2 encounter. On the cruise portion of that journey, the extrasolar component of the mission kicked in. EPOCh (Extrasolar Planet...

Finding Earth-size planets around other stars is a long-cherished goal, and new results from Geoffrey Marcy and Andrew Howard (UC Berkeley) give us reason to think they're out there in some abundance. As reported in Science, the astronomers have used the 10-meter Keck telescopes in Hawaii to make radial velocity measurements of 166 G and K-class stars within 80 light years of Earth. The resulting five years of data suggest that about one in every four stars like the Sun could have Earth-size planets, although none has thus far been detected. "Of about 100 typical Sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune, and about 12 have super-Earths between three and 10 Earth masses," said Howard, a research astronomer in UC Berkeley's Department of Astronomy and at the Space Sciences Laboratory. "If we extrapolate down to Earth-size planets -- between one-half and two times the mass of Earth -- we predict that you'd find about 23...

With three groups now looking hard at Alpha Centauri for planets, let’s hope our nearest stars don’t do for us what Gliese 581 has. First we had a habitable planet in Gl 581c, then we didn’t. Then Gl 581d looked a bit promising, and may skirt the outer edges of the habitable zone, although the jury is still out. Gl 581g looked to be the winner, the fabled ‘Goldilocks’ planet, but now the evidence for it seems weak and its existence is called very much into doubt. Gl 581 keeps dealing out winners and then calling them back, a frustrating period for all concerned. What we’d like to find at Alpha Centauri, then, is something unambiguous. But while we wait for answers, the issue of how planets form in close binary systems like Alpha Centauri is under the microscope. Centauri A and B have a mean separation of 23 AU, closing to within 11.2 AU (think of another star as close to ours as Saturn) and receding up to 35.6 AU (roughly Pluto’s distance). Proxima is much further out at 13,000 AU...

Planets around binary stars fascinate me, doubtless because of Alpha Centauri’s proximity and the question of whether there are planets there. About ten percent of the planets we’ve found around main sequence stars are found in binary systems, and most of these binaries have wide separations, in the range of 100 to 300 AU. But, like Alpha Centauri, close binaries remain promising targets. I’m looking at a new paper by Andras Zsom, Zsolt Sándor and Kees Dullemond (Max-Planck-Institute für Astronomie) dealing with early stage planet formation in binaries, and they’re quick to note that planets in close binary systems put constraints on planet formation theories. After all, if we find planets in these systems, our planet forming theories have to produce satisfactory explanations for their existence. Does core accretion, then, work in these environments? We can look to close binaries with planets, systems like Gamma Cephei (separation 18.5 AU), GL 86 (18.4 AU), HD 41004 (23 AU) and HD...

For all the excitement the Kepler mission has generated, we sometimes forget its limitations. Kepler is engaged in a transit hunt for exoplanets that will help us identify not just gas giants but planets the size of our own. But it's a brute-force method, looking at a huge number of stars to identify the few whose planetary systems are aligned properly for us to see transits. And the necessary limitation is that when we do find terrestrial-sized worlds, we'll be unable to do much by way of follow-up, because most of those planets will be thousands of light years away. This is not to diminish Kepler's critical work (nor that of CoRoT), for in no other way are we currently gaining this kind of overview of the planetary environment around a wide range of stars. But Philip Horzempa reminds us in a recent post on The Space Review that we have follow-up missions in the pipeline that are now losing their funding. Specifically, the Space Interferometry Mission (known as SIM Lite in its last...

What exactly does the word 'habitable' mean? The question comes to mind because of two things, the first being the media buzz over Gliese 581g, now widely described as the first potentially habitable planet we've found. The second is Paul Davies' presentation yesterday at the International Astronautical Congress in Prague, where Davies was careful to differentiate between 'habitable' and 'inhabited.' More on the latter in a moment. Let's look first at this outstanding find, two new planets in the Gliese 581 system discovered through the unflagging efforts of the Lick-Carnegie team. A World in the Zone? The beauty of Gl 581, of course, is not only that it has yielded a storehouse of planets (six known at present), but that these worlds are on nearly circular orbits, and several have caught our eye re habitability before. The current buzz seems a bit tamer than the one that greeted the announcement of Gl 581c, at the time thought to be capable of sustaining liquid water on its surface,...