Best wishes to all for a wonderful 2008, and thanks beyond the telling to the numerous readers who participated in our discussions in the year past. There will be no post on New Year's day, but we'll get back to the normal schedule on the afternoon of January 2. Have a wonderful holiday.
Apropos of Saturday's article on the Subaru Telescope -- and the optical improvements that may help it detect an exoplanet image -- comes news that scattered light from a planet orbiting another star has been detected by an international team. The planet is our old friend HD189733b, some sixty light years away in the constellation Vulpecula. The transiting world is a 'hot Jupiter,' orbiting its star in 2.2 days at a blindingly close 0.03 AU. Thanks to Hans Bausewein for passing along the link to a news release on this work. The scientists involved -- Svetlana Berdyugina (ETH Zurich & Tuorla Observatory), Andrei Berdyugin and Vilppu Piirola (Tuorla Observatory), and Dominique Fluri (ETH Zurich) did their study using polarimetry, examining starlight that is scattered in the distant planet's atmosphere. Polarimetry measures the angle of rotation of the plane of polarized light that occurs when it moves through particular materials. It's a useful technique for exoplanetary work because...
How likely is it that we will begin to image extrasolar planets from observatories on the ground? The prospect seems all but certain if we grant a long enough lead time to get certain advanced telescope designs built, but it may happen sooner than we think if the news from the Subaru Telescope is factored in. The instrument, an 8.2 meter optical/infrared telescope, is located at the summit of Mauna Kea (Hawaii), from which vantage it has already produced intriguing results like spin-orbit alignment measurements for the exoplanet TrES-1. But Subaru astronomer Ryuji Suzuki is ready to go to the next step. Noting the installation of the HiCIAO camera (High Contrast Instrument for the Subaru Next Generation Adaptive Optics), Dr. Suzuki points out that "...the unique instrument was primarily designed for the direct detection of extrasolar planets and disks." Indeed, the Subaru team is hopeful that they will be the first to directly observe a planet orbiting a star other than our own...
When it comes to understanding possible extraterrestrial civilizations, I'm with Freeman Dyson, who had this to say: "Our business as scientists is to search the universe and find out what is there. What is there may conform to our moral sense or it may not...It is just as unscientific to impute to remote intelligences wisdom and serenity as it is to impute to them irrational and murderous impulses. We must be prepared for either possibility and conduct our searches accordingly." As quoted in a 2005 essay by Michael Michaud, Dyson saw two alternatives: Intelligent races may rule their domains with benign intelligence, occasionally passing along the knowledge they have accumulated to a universe eager to listen. Or intelligence may be purely exploitative, consuming what it encounters. We don't know which of these alternatives prevails, if either, and that's one reason that Michaud, a former diplomat who became deputy assistant secretary of state for science and technology, resigned...
Cassopeia A is a supernova remnant some 11,000 light years away. Turning the attention of the Spitzer Space Telescope on this object allows us to examine the different elements within it, a useful exercise because it helps to answer a question about the early universe: Where did the interstellar dust so essential for the formation of stars and planets -- not to mention the creatures that live on planets like ours -- come from? Despite the ubiquity of space dust, the question has persisted because the first stars, so-called Population III, are the only ones to have formed without dust. We can see dust being pumped out by dying solar-type stars in the nearby universe, but in the infancy of the cosmos, such stars weren't old enough to perform the job. So massive Population III stars are thought to have contributed dust in their violent death as supernovae, a theory in support of which Cassiopeia A provides data. Jeonghee Rho (Spitzer Science Center, Caltech) seems certain of the result:...
Merry Christmas! And for those who celebrate other holidays — or none at all — best wishes for the season. Centauri Dreams will not publish on December 25. Normal publication resumes on the afternoon of the 26th.
How much information can you extract from a single pixel? That's a key question for exoplanet studies as we look to the day when advanced telescopes can actually see a planet orbiting another star. But a single point of light seems to offer scant value, which is where Enric Pallé (Instituto de Astrofísica de Canarias) and colleagues go to work. They've been looking at how that single pixel changes over time, and what we might glean from it in terms of planetary details. A key factor is cloud cover. Using data from Earth's weather satellites, the scientists have been able to discover consistent patterns associating clouds with arid or rainy landmasses. Pallé explains: "The trick lies in interpreting the movement of the Earth's surface and the clouds as periodical signals, just as if we were to observe the spots on a spinning ball appearing and disappearing...[O]n a global scale clouds aren't as random and chaotic as is generally believed, but instead follow a pattern...
The latest on the asteroid approaching Mars, with potentially Tunguska-like dangers, is that it will likely pass a safe 48,000 kilometers from the surface at about 1100 UTC on January 30. This news release describes the possibility of an impact as 'unlikely,' but goes on to say that if it does occur, the best view of the event will come from the Mars Reconnaissance Orbiter, whose High Resolution Imaging Experiment (HiRISE) would provide an unprecedented look at the crater. While the size of asteroid 2007 WD5 approximates the object whose impact formed Meteor Crater (northern Arizona) some 50,000 years ago, the latter is thought to have been a metallic asteroid, while the one approaching Mars is probably stony. Current estimates of 2007 WD5 make it out to be 50 meters wide, traveling at some 13 kilometers per second. That's enough to carry quite a punch, as the Tunguska impact proved in 1908, and as we may conceivably see at the end of January. As we watch for updates, ponder the...
Perhaps it's fortuitous that an object similar to the asteroid that caused the Tunguska event in Siberia may put on a display for us on Mars. It's only a one in 75 chance that 2007 WD5 will strike the surface, and those odds may change again as further data are analyzed, but if it does hit, the object could strike with much the same force as the Siberian explosion. This news story reports Tunguska as a 15-megaton explosion, though as we saw on Wednesday, new work at Sandia National Laboratories has re-considered that figure and now opts for the 3-5 megaton range. The potential impact site is near the Martian equator. If we were to witness such a spectacle, it would bring back memories of the 1994 strike of comet Shoemaker/Levy 9, the famous 'string of pearls', on Jupiter. The devastation of that event was stunning, far greater than 2007 WD5 would produce, but the latter might deliver enough fireworks to produce a crater the size of Meteor Crater in Arizona. Is the Solar System trying...
You knew as soon as you opened Carl Sagan's 1973 title The Cosmic Connection that you were leaving an Earth-centric view of the cosmos behind. The title page showed, spread across both it and the facing page, a spiral galaxy. The work of Sagan friend and collaborator Jon Lomberg, the illustration included reference to Type I, II and III civilizations, the Kardashev ranking that few laymen had heard about in those days, but which Sagan's work would illuminate for an increasingly interested public. The public would have been drawn first, though, to the cover of that first edition of The Cosmic Connection. A night landscape in black and white, a solitary tree outlined against the sky. But what a sky, filled with what looked like a galaxy -- billions and billions of stars -- rising. That image encapsulated so much of the book's message. It juxtaposed our familiar terrain against something so vast, so filled with the potential other stars suggest, that you were forced to speculate on our...
Fifteen megatons of TNT would set off a blast a thousand times more powerful than the weapon used on Hiroshima. 2000 square kilometers of flattened pine forest near the Podkamennaya Tunguska River in central Siberia bear witness to what such a blast can do. That explosion occurred on June 30, 1908 [original typo said '2008,' an obvious mistake!], and we're learning more about it. The Tunguska event seems to have been an air blast occurring at an altitude between five and ten kilometers. The presumed cause: A small asteroid slamming into our atmosphere at speeds in the range of 15-30 kilometers per second. But just how big was the asteroid? I've seen estimates in the range of 50-100 meters in diameter, but we know surprisingly little about the object. No fragments exist. The effects of the fireball and blast wave are apparent (and there are eyewitness accounts of hot winds and shaking buildings), but there is no crater at the epicenter of the blast. We're left to calculate the...
Lately I've been thinking about cosmic killers, the kind of extinction events that could destroy an entire ecosphere and any civilization living within it. It's a natural enough thought given our speculations about life elsewhere in the universe. Just how hostile a place is the Milky Way? We're beginning to learn that planets are abundant around stars in our region of the disk, with the encouraging expectation that habitats for evolving lifeforms must be widespread. But maybe there are natural caps other than technological suicide that could end a civilization's dreams. You can't help pondering this when you run into the recent news about a long duration gamma-ray burst (GRB) that took astronomers by surprise. GRBs are normally thought to flag the death of a massive star, but in this case the burst seems to come out of nowhere. What caused the event in a region of space where the nearest galaxy is 88,000 light years away? And no question about GRB 070125's credentials. It was...
How long did it take for the planets in our Solar System to form? Much depends upon the surface density of the solar nebula protoplanetary disk, the gas and dust from which the planets emerged. And the problem with surface density -- mass per area -- in these settings is that it's hard to observe with our current instrumentation. Looking at distant systems in the process of formation, we see mostly dust and miss larger objects. Thus an estimate based on known factors is called into play. It produces the so-called minimum mass solar nebula. Using it, scientists can estimate solar nebula mass by starting with the rocky components of each planet, adding hydrogen and helium until the composition resembles that of the Sun. Spread that mass over the area of each planet's orbit and you get disk masses that look like what we see in systems around other stars. But there's a problem. The low surface densities this model produces aren't sufficient to allow the planets to form in a reasonable...
We wrap up our look at the American Geophysical Union meeting last week in San Francisco with an update on Europa. An interesting point that William McKinnon (Washington University, St. Louis) made in a news briefing there has that what had been a belief that there is an ocean on Europa is now hardening into a certainty. The intriguing next step is to learn more about that ocean, and here things get tricky. Just how do you study an ocean on a distant world upon which you have yet to land? Fortunately, magnetic variations around Europa as well as observations of how the moon flexes and deforms as it orbits Jupiter can tell us much. Thus the need for a Europa orbiter, a mission that could measure gravity and magnetic fields as well as determining surface composition. Another area of interest for such a spacecraft: Are there recent eruptions from this geologically young world? The search for hot spots from such events could get interesting, to judge from what Cassini found on Enceladus....
Universe Today offers the latest Carnival of Space, which will have exoplanet watchers checking Steinn Sigurðsson's Dynamics of Cats site for updates on CoRoT. Almost a year into its mission, the observatory has completed its first 150-day continuous examination of the same area of sky, and the results are, so rumor has it, quite interesting. I see that CNES (Centre National d'Études Spatiales) is now saying that 'CoRoT will instigate a breakthrough in both of the fields of science that it applies to,' making the upcoming publication of CoRoT papers eagerly to be awaited. And you have to love this statement: ""...CoRoT is discovering exo-planets at a rate only set by the available resources to follow up the detections."
The accepted take on the formation of Saturn's rings not so long ago was that they had emerged within the past 100 million years. The most likely driver: A comet that broke a larger moon into pieces, forming ring features seemingly consistent with what the Voyagers saw in the 1970s and the Hubble telescope has seen ever since. But leave it to Cassini to stir things up yet again with much more precise data suggesting that the rings did not form in a cataclysmic event but are continually recycled. Thus Larry Esposito (Colarado University, Boulder), who is also principal investigator for Cassini's Ultraviolet Imaging Spectrograph: "The evidence is consistent with the picture that Saturn has had rings all through its history. We see extensive, rapid recycling of ring material, in which moons are continually shattered into ring particles, which then gather together and re-form moons." The findings received less media attention than Voyager 2's crossing of the termination shock, discussed...
Gliese 581 is back in the news with a flourish. Astronomy & Astrophysics is publishing two independent studies of the system asserting that at least one of the inner planets is indeed located within the habitable zone of that star. Gliese 581 c and d are noteworthy every time they're mentioned. Of five and eight Earth masses respectively, they are the first exoplanets ever considered serious candidates for habitability. M dwarfs have inherent problems in terms of habitability, not the least of which is the tidal lock that planets in the HZ of such stars presumably experience, keeping one side perpetually dark. But models of atmospheric circulation exist that overcome that obstacle, and the intense magnetic activity of early M star life (producing dangerous flares) is no longer considered a necessary disqualifier for all forms of life. It's going to be a while before we have any definitive answers, but current thinking is that habitable M dwarf planets are very much in the picture,...
We're learning more and more about HD 189733b, an extrasolar planet some 63 light years from Earth in the direction of the constellation Vulpecula. This transiting 'hot Jupiter' orbits once every two days about three million miles out from its primary. David Charbonneau (Harvard-Smithsonian Center for Astrophysics) and team recently measured an unusual spectrum from the planet's atmosphere using the Spitzer Space Telescope. Looking for water, carbon dioxide and methane, they found instead a flat spectrum that Charbonneau thinks may indicate the presence of dark silicate clouds. Now we have further work, this time using Hubble Space Telescope data, that points to the presence of haze in the atmosphere of HD 189733b. That's an interesting finding to which we can add another result: Studying how light varies when the planet makes its transit indicates that this world has neither Earth-sized moons or a discernible ring system. Moreover, we've got a fairly good read on the temperature of...
The recent Voyager news, reported from the American Geophysical Union conference in San Francisco and recently discussed here, has drawn attention to the apparent asymmetry of our Solar System. Voyager 1 crossed the termination shock -- where the solar wind first encounters the thin gas of the interstellar medium -- some three years ago. But that was a crossing with a difference. Voyager 1 went through the termination shock just once. Voyager 2 has apparently crossed it five times and may encounter it again. Ahead in a decade or so: The heliopause, where the Sun's influence effectively ends. Thus we have a glimpse of how the solar wind varies with changes in the Sun's activity level, pulsating as the solar cycle swings from solar flares into quiet periods, pushing the shock area out a bit farther, then contracting it. And while Voyager 1's plasma science instrument had stopped working when it encountered the termination shock, Voyager 2's is working well and making detailed...
Some day we may be using solar sails to take payloads into an increasingly busy Solar System. Let's hope that day isn't far off, because the technology looks practical. But as we study solar sail methods, in which the sail is pushed by the momentum of photons, we also want to keep magnetic sail possibilities firmly in mind. A magsail could theoretically ride the 'solar wind,' that stream of charged particles pushing out from the Sun at speeds approaching 1.5 million kilometers per hour. Dana Andrews (Andrew Space) considered the problem of drag posed by interstellar ramjet concepts back in the 1980s, and along with fellow engineer Robert Zubrin went on to ponder how enormous magnetic sails could take advantage of the solar wind. The beauty of the concept is that you do away with a material structure of the sort so tricky to deploy in large solar sail designs. Instead, you generate the magsail from within the spacecraft. Couple this with a particle beam and you may have an...
