Using a near-infrared spectrograph attached to ESO's Very Large Telescope, astronomers have been able to examine the inner protoplanetary disks around three interesting stars, with results showing the sheer diversity of the apparently emerging systems. Only a few million years old, all three stars could be considered analogs of our own Sun, going through processes like those that produced the Solar System some 4.6 billion years ago. The disks under study show regions where the dust has been cleared out, the possible signature of planetary influence. The new work, which offers higher resolution than was earlier available, demonstrates that the previously known gaps in the dust still contain molecular gas, an indication that the dust has begun to form planetary embryos or that a planet has already formed and is clearing the disk gas as it orbits. The likely planets include a massive gas giant orbiting the star SR 21 at a distance of something less than 3.5 AU, and a possible planet...

A supercomputing cluster operated by a team at Northwestern University is giving us fresh simulations of the birth of planetary systems, with results that may dismay terrestrial planet hunters. For if this work is correct, the 'rare Earth' hypothesis is back, this time bolstered by computer models that are the first to simulate the formation of planetary systems all the way from earliest dust disk to full-fledged solar system. More than a hundred simulations using exoplanet data collected over the last fifteen years went into the modeling of dust, gases and the effects of gravity. Planetary systems do seem to have a few things in common, among them a violent birth. The Northwestern team found that the dynamics of the early gas disk push nascent planets inexorably toward their central star. There they may be consumed in the star or subjected to collisions with other objects as each accumulates mass. Dynamical resonances can occur that produce increasing orbital eccentricity, with...

Astrometry, using the position and motion of celestial objects to further astronomical research, is ever more useful in the study of extrasolar planets. If you can measure how much a given star is displaced by the presence of a planet, you have a valuable adjunct to existing radial velocity and transit methods. Now a new study has examined astrometry's uses with binary stars, using the Hale telescope on Mt. Palomar and the Keck II instruments on Mauna Kea. And with certain restrictions, adaptive optics may allow us to detect binary star planets. The targets were seventeen binary or multiple star systems, most of them M-dwarf binaries closer than 20 parsecs from the Sun. Observations were conducted in the near infrared, with relative separations and position angles carefully measured. Study authors Krzysztof Helminiak and Maciej Konacki (Nicolaus Copernicus Astronomical Center, Poland) note the advantage of close systems: The closure of companions allows one to observe visual binaries...

Finding transiting planets is no longer a surprise, and we can expect a host of transits from the CoRoT mission, which has the advantage of observing from a space-based platform. Moreover, CoRoT will, in the course of its lifetime, survey as many as 120,000 stars for up to five months. Driving home the advantage is the announcement of a new CoRoT planet known as CoRoT-Exo-4b. We're dealing with another Jupiter-sized planet orbiting in close proximity to its star, but this one has a unique claim to distinction: Its host star is rotating at the same pace as the planet's orbit. Image: Fixated upon a star: An artists impression of the satellite CoRoT in orbit around the Earth. Credit: CNES. Moreover, for a transiting world, CoRoT-Exo-4b is a relatively long-period planet, orbiting its F-class primary in 9.2 days. Thus far most transiting worlds have had orbits below about five days, two major exceptions being HD 147506b and HD 17156b, the latter with a period of 21.2 days -- both of...

You must see new video from EPOXI, whose effect can only be suggested by the photo montage below (click the link below for the movie). EPOXI is the combined extended mission of the Deep Impact spacecraft. As we discussed in an earlier story here, EPOXI turned its cameras on the Earth to view the moon transiting the planet's disk from a vantage point of 31 million miles. Think in terms of viewing the Earth the way we will eventually view terrestrial worlds around other stars. The idea is to build insights into how these worlds can be observed and characterized. Image: The moon crossing the Earth, as viewed by EPOXI. Video credit: Donald J. Lindler, Sigma Space Corporation/GSFC; EPOCh/DIXI Science Teams. Drake Deming (NASA GSFC), deputy principal investigator for EPOXI and leader of the extrasolar planet component of the mission (called EPOCh), points out how the information can be helpful: "Our video shows some specific features that are important for observations of Earth-like...

It's easy to see why interest in planets around red dwarfs is growing. The low mass of such a star makes finding smaller planets feasible. It also produces orbits closer to the star, another aid to their detection. We know that planets can form near the habitable zone of such stars because we have the example of Gliese 581, where two planets orbit close to if not just within that region. But is a habitable planet always habitable? If not, what could make these conditions change? I'm looking at a paper that examines tidal effects, an important factor when dealing with M dwarfs. Planets in the habitable zone around these stars experience effects that can cause both their orbital distance and orbital eccentricity to decrease [see comments below re my original misstatement of the eccentricity change, now corrected]. The paper, by Rory Barnes (University of Arizona, Tucson), Sean Raymond (University of Colorado, Boulder) and team, examines an interesting parameter: The habitable lifetime....

We've been paying a lot of attention to Centauri A and B in the past two years, but what about Proxima Centauri? After all, this is the closest star to our Sun, a fifth of a light year out from the two major Centauri stars, and free of the close binary problem. You would think this small red dwarf would rank higher on our list of astrobiologically interesting places, but until recently, that red dwarf status has been an encumbrance. It has been only within the last eleven years that the presumed tidal locking of planets in the habitable zone of such stars has been found not to be a necessary deterrent to the formation of a stable climate. Today, M dwarf interest grows. There's at least the chance of a workable ecosystem around such a star, assuming flare activity (common to these stars) might act more as an evolutionary stimulus than a deterrent to life. Moreover, the long lifetimes granted to M dwarfs mean that stable environments could exist for many billions -- perhaps hundreds of...

The news about planetary prospects around the Centauri stars has been positive enough lately that a paper suggesting otherwise introduces a rather jarring note (to me, at least). After all, we've detected more than forty extrasolar planets in multiple systems, a significant percentage of all detected exoplanets, and while most of these are in systems where the stars are widely spaced, there are planets around stars like Gliese 86 or Gamma Cephei where the separations are in the range of a Centauri-like 20 AU. Moreover, key studies have shown that planetary orbits in the habitable zone of the Centauri stars are viable. But what Philippen Thébault (Stockholm Observatory), Francesco Marzari (University of Padova) and Hans Scholl (Observatoire de la Côte d'Azur) bring to the table is a different question. Never mind that planetary orbits may be stable -- how likely are planets to form in these settings in the first place? It turns out that the last stage of planet formation has been...

We'd all like to think our Solar System is a run-of-the-mill place, filled with the kind of planets, including our own, likely to be found around other stars. But maybe it's not so ordinary after all. For recent work suggests that stars like the Sun aren't all that likely to form planets the size of Jupiter or larger. So while small, rocky worlds may or may not be common -- we're still finding the answer to that one -- the combination of rocky worlds and gas giants we take for granted may actually be distinctive. Once again I'm reminded how many conjectures go into our projections of habitable worlds. Here's one possibility: Without a large gas giant in the outer solar system to act as a gravitational shield for the inner system, planets in the habitable zone of a star might be so pelted by space debris that life would be unlikely to form on them. So it's conceivable that any findings about the scarcity of gas giants are a blow to our astrobiological hopes around other stars. At...

The dusty disks around other stars can tell us much about how planets form, creating a catalog of systems in various stages of development. But some of the best evidence for our own system's formation has to be dug out of the ground. It's based on the chondrules found in certain meteorites that seem to have been formed in the earliest stages of its life. They're small, round objects about a millimeter in size, made of glass and crystal and thought to have been formed by the flash heating of dust. We're talking major heat here, up to 2000 degrees Celsius. A new study of chondrules is unusual because it finds higher levels of sodium than ought to be there. That's problematic because the heat of chondrule formation, under existing theories, should have boiled off volatile chemical elements. Here's Conel Alexander (Carnegie Institution) on the matter: "Chondrules formed as molten droplets produced by what was probably one of the most energetic processes that operated in the early solar...

The much anticipated Nantes conference on Extrasolar Super-Earths is already paying off big in the form of a triple system of such planets. Found around the star HD 40307, the planets are among the 45 candidate worlds recently identified by European scientists using the HARPS instrument, a spectrograph mounted on the European Southern Observatory's 3.6-meter telescope at La Silla. The survey focused on F, G and K-class stars, finding 45 potential planets, all of which are below 30 Earth masses and show an orbital period shorter than fifty days. What's happening here testifies to the growing sophistication of our tools. While most of the 300+ positively identified exoplanets have been found around Sun-like stars, they have so far tended to be gas giants. Teasing smaller planets out of the data requires long observing runs -- HD 40307, for example, has been under active study for five years -- and it also requires the greater precision of instruments like HARPS. "With the advent of...

The latest Carnival of Space is up at Out of the Cradle, where this week's interstellar focus is delivered by Steinn Sigurdsson (Penn State), who takes a look at the new planet with the tongue-twisting name: MOA-2007-BLG-192Lb. We focused in on this one just a few days ago, intrigued by its small size (about three Earth masses) and its orbit around a low-mass star that is either a brown dwarf or a low mass M-dwarf. But note the play in the numbers from this microlensing detection, which suggests the mass could actually be as low as 1.7 Earth masses or as high as 8.2. The discovery paper is stuffed with the relevant analysis of the statistics and how the team's conclusions were arrived at. Let me quote Steinn on the possible significance of this find, which should have some resonance here: It is very hard to draw a robust conclusion from a single data point, the formal uncertainties are infinite; but, this is a small corner of the observing parameters space, low mass stars have low...

Yesterday's story on the smallest exoplanet yet discovered somewhat obscured work on brown dwarfs released at the same conference. But this year's meeting of the American Astronomical Society has been filled with interesting items, and I don't want to neglect the latest news about a type of star that may be as plentiful as any in the cosmos. We don't know that that is the case, but we have much to learn about brown dwarfs as we compile a census of those in the Sun's neighborhood, including the question of what kind of planets might circle them. New observations studied by Michael Liu (University of Hawaii) and team have now been able to determine the masses of a number of brown dwarfs, with findings that suggest the shape of future research. Says Liu: "Mass is the fundamental parameter that governs the life-history of a free-floating object, and thus after many years of patient measurements, we are delighted to report the first masses of the very faintest, coldest brown dwarfs. After...

Smaller and smaller planets keep coming into view. A prime goal, of course, is to find something around the size of the Earth, implying as it would the existence of a world that might be like ours in other ways. My suspicion is that one day soon a transit study is going to come up with an exoplanet that's closer to the size of Mars (definitely possible with today's technologies), and we'll skip right past the 'Earth twin' point before finding a planet that really is close to the same diameter. But so far we're still looking at worlds larger than Earth, like the tongue-twisting MOA-2007-BLG-192Lb, now thought to be the lowest mass planet ever found around another star. Announced today at the American Astronomical Society's meeting in St. Louis, the new planet orbits a brown dwarf. At six percent of the mass of the Sun (and thus unable to sustain nuclear reactions in its core), the host is the lowest mass star to have a companion with a planetary mass ratio. But the fudge factor in the...

My local paper is running a story on page 11A entitled "Astronomers Report Earth-like Planet." It's a tantalizing headline, but obviously one that bears further investigation. For what's being reported here is background information on one of the 45 planets -- I should say 'candidate' planets -- recently discussed at the Boston meeting of the IAU. These have been extracted from the HARPS planet survey, but we'll probably have to wait until mid-June for further confirmation, which may well occur at the upcoming Extrasolar Super-Earths workshop in Nantes. This would be an interesting world if things do play out, a rocky 'super Earth' just over four times as massive as Earth, and hence the smallest world yet in our attempt to find planets not so different from our own. If the press continues to generate a buzz about this, we should look at the contrast with the Gliese 581 story. There we wound up with two planets of astrobiological interest, one apparently on the inner edge of the...

I recently wrote about EPOXI, the dual-purpose extended mission being flown by the Deep Impact spacecraft. Yes, this is the same spacecraft that delivered an impactor to comet Tempel 1 with such spectacular results back in 2005. The vehicle now proceeds to a flyby of comet Hartley 2, but along the way a second extended mission has been coaxed out of it, this one targeting several known transiting planets in a search for signs of undiscovered worlds in those same systems. The mission will also look for possible moons or rings around the giant planets already discovered. Another goal: To study the Earth, by way of calibrating the kind of 'pale blue dot' imagery a future terrestrial planet finder might see. In fact, observations taking place this very day should be helpful because the Moon will 'transit' the Earth from the spacecraft's perspective. And yes, the nomenclature is confusing, but acronyms are the name of the game in space operations. EPOXI is actually a conflation of two...

Yesterday's high-tension arrival on Mars raises inescapable thoughts about future missions. Even the fastest spacecraft we can build today take years to reach the outer planets (New Horizons won't reach Pluto/Charon until 2015), and targets deep in the Kuiper Belt, much less the Oort Cloud, conjure up potential missions longer than a human lifetime. Imagine the arrival of a robotic interstellar probe around, say, Epsilon Eridani, not a few years after launch, but a few generations. How would the team feel that took that final handoff from previous researchers, people who had invested their lives in a mission whose end they knew they would never see? Thus we make the segue back into interstellar matters, with today's Phoenix operations still very much in mind. And I want to go quickly to the recent COROT announcement, for the doughty spacecraft has been hard at work observing its sixth star field, a sweep of some 12,000 stars that began in early May. The team presented two new planets...

From the standpoint of planetary detections, the small red stars called M dwarfs are all but ideal. Their size is an advantage because radial velocity and transit methods should find it easier to pull the signature of smaller planets out of the statistical noise. Not so long ago, that wouldn't have seemed important because the search for terrestrial worlds seemed confined to G- and K-class stars not too different from our Sun. But more and more theory is piling up as to why a terrestrial-sized planet in the habitable zone of an M dwarf could harbor life. So these are important stars, especially when you add in the fact that they account for 75 percent or so of all the stars in the Milky Way (that statistic is admittedly subject to change as we learn more about other stars, especially brown dwarfs). And that makes the recent flare on EV Lacertae quite interesting. Some sixteen light years from Earth, the star is young (300 million years), dim (shining with one percent of Sol's light)...

Boosting the sensitivity of our exoplanet search tools by a hundredfold is no small matter, yet that's just what optical frequency combs, when implemented with an ultrafast laser, may be able to do. A frequency comb is created by a laser that generates short, equally spaced pulses of light. 'Locking' the individual frequencies -- keeping them in phase with each other -- is essential, as is producing pulses that are no more than a few million billionths of a second long. The image below explains the name, the graph giving the impression of nothing more than a fine-toothed comb (and see this National Institute of Standards and Technology backgrounder for further details on how these combs work). We've looked at laser combs before, in particular in the work being performed at the Harvard Smithsonian Center for Astrophysics, which is involved in the deployment of such a comb at the William Herschel Observatory in the Canary Islands. The resultant instrument, called the HARPS-NEF...