by Paul Gilster | Aug 14, 2007 | Exoplanetary Science |
The Hungarian Automated Telescope Network (HATNet) is run out of the Harvard-Smithsonian Center for Astrophysics, with primary stations at Mauna Kea (HI) and on Mt. Hopkins (Arizona). Looking at large fields of stars over many consecutive nights, the automated telescopes involved help astronomers identify the periodic dimming that marks a transiting exoplanet. And with other projects like the Trans-Atlantic Exoplanet Survey (TrES), the XO Project in Maui and the Optical Gravitational Lensing Experiment (OGLE) in Chile operational, transit data are piling up.
All of which is useful indeed, for at present we are just nearing 20 transiting planets detected from ground-based observatories. The discovery paper for the most recent HATnet detection makes an interesting point about the size of our sample, declaring it “…still small enough that individual discoveries often advance our understanding of these objects significantly by pushing the limits of parameter space, either in planet mass, radius, or some other property.”
How true, and a corrective to the notion that we can make quick generalizations about the planets thus far found. At a recent cocktail party, I was button-holed by a man who wanted to know whether or not most solar systems are going to be like our own. I had to explain that the data aren’t remotely available to make such a call, that we are beginning to know some things about particular classes of planets, especially those most readily detected by radial-velocity methods (and early in the data gathering process at that), but that due to the nature of our techniques there are planetary regimes we know little about, including outer gas giants and terrestrial planets in habitable zones.
Transits are a particularly useful kind of detection because astronomers can get good information about the mass and size of such planets, as well as having a shot at learning something about their atmospheres. The new HAT find is designated HAT-P-3b, a planet that turns out to be the smallest transiting world found photometrically (the transits of smaller planets have been noted — among them, GJ 436b — but not before their original detection by radial-velocity methods). The star in question is the K dwarf GSC 03466-00819, now called in the paper HAT-P-3.
Its planet, HAT-P-3b, orbits at a scorching 0.03894 AU, and looks to be about 60 percent Jupiter’s mass, with a radius almost 90 percent that of Jupiter. Theory suggests that radius is consistent with a core of heavy metals of about 75 Earth masses, a finding supported by the metal content of the host star. The paper is Torres et al., “HAT P-3b: A Heavy-Element Rich Planet Transiting a K Dwarf Star,” scheduled to appear in Astrophysical Journal Letters, with preprint available.
by Paul Gilster | Aug 14, 2007 | Culture and Society |
by Bernd Henschenmacher
Giancarlo Genta’s new book Lonely Minds in the Universe deals with many aspects of the search for extraterrestrial life and intelligence. As does Michael Michaud in his Contact with Alien Civilizations, Genta examines the scientific and philosophical implications of such contact. The book begins with an overview of Western thought on the subject from the ancient Greeks to the late 20th Century, including the question of how extraterrestrial contact might affect human religious beliefs.
The book’s astrobiological chapters offer a rapid introduction to this emerging science. Readers who are familiar with concepts like habitable zones, speculations about life on Mars, Europa or Titan and the concept of a galactic habitable zone will find little new here, but this section offers a well written and easy to understand backgrounder.
The book’s treatment of evolution, intelligence and consciousness — including the problem of defining consciousness itself — is striking. Genta provides an introduction to the evolution and origin of the human mind, one that questions traditional concepts of the association between intelligence and consciousness. Can intelligence exist without consciousness? The book’s final chapters deal with the sociological and technical aspects of ETIs. Is interstellar travel inevitable for technological civilizations? What about dealing with contact? Can wars occur between different species? (The author rejects the idea because of the huge distances between the stars and the speed of light barrier).
Even though the possibility of faster than light travel and breakthrough propulsion by manipulating gravity, inertia or space-time are mentioned, the author concludes that fast interstellar flight (i.e., within single human lifetimes) will probably involve methods we cannot even imagine at the moment. This book is highly recommended for anyone looking for for an overview about the scientific and philosophical aspects of astrobiology and SETI.
by Paul Gilster | Aug 13, 2007 | Exoplanetary Science |
With the European Space Agency’s DARWIN at least a decade off and funding for the Terrestrial Planet Finder as problematic as ever, what would be a suitable interim mission to extend our exoplanet exploration program? COROT is already flying, with the possibility of detecting large terrestrial planets in close orbits, while Kepler should be able to detect Earth-mass planets in Earth-like orbits by 2013 or earlier. All of which is promising, but we’re still missing key elements of the puzzle.
Take those transiting exoplanets COROT and Kepler track. We’ll retrieve a wealth of data, but we probably won’t be able to get the kind of spectroscopic information we’d like to see from a more advanced mission. Similarly, ground-based telescopes using adaptive optics, and future space missions like the James Webb Space Telescope should show us hot gas giants, but we’ll be unlikely to see planets like our own Jupiter and Saturn, cooler worlds in more distant orbits.
The solution? A team of NASA researchers including Karl Stapelfeldt and Wesley Traub at the Jet Propulsion Laboratory make a strong case for a 2-meter optical space telescope equipped with the latest in coronagraph technology to reveal details of planetary systems that would otherwise be lost in the central star’s glare. A smaller space telescope could be flown at a cost much reduced over the kind of budgets the full-scale Terrestrial Planet Finder would have required.
Among its benefits:
- Measuring the color, taking the spectra and providing astrometric measurements of outer gas giant planets in nine nearby systems known to host planets. We should be able to analyze their atmospheres and measure the depth of their uppermost cloud decks. Factors such as the planets’ albedo and the presence of ring systems should be accessible, as will be planetary size.
- The discovery of new gas giants in the kind of five to ten AU orbit Jupiter and Saturn occupy in our own system. Thirty stars within 25 parsecs that are already known to host close-in planets (detected through radial velocity methods) would be prime candidates for study. Ultimately, such an instrument has the potential to find outer Jovian worlds around as many as 200 nearby stars.
- A 2-meter class instrument in space should be able to resolve rings, warps and asymmetries caused by planetary movement within circumstellar dust disks. With a contrast a thousand times sharper than Hubble’s, such an instrument could be sensitive enough to detect exosystem analogues to our own tenuous Kuiper Belt.
I save the best for last. The researchers believe their instrument may have the ability to detect Earth-sized planets in the habitable zones of five to ten of the brightest, nearest stars. Studying their photons would allow a basic spectral characterization, doubtless motivating intense studies by later, more powerful instruments (and, of course, tuning their target lists).
A mission like this is currently missing from the catalog of upcoming observatories, doubtless because of over-optimism in early assessments about both the growing power of adaptive optics on ground-based telescopes and the possibility of refitting the Hubble instrument with an advanced coronagraph, an idea since abandoned. “Our community can either resign itself to waiting out JWST,” the authors write, “or look for ways to achieve significant new exoplanet science, sooner, through more modest projects.”
The paper is Stapelfeldt, “First Steps in Direct Imaging of Planetary Systems Like our Own: The Science Potential of 2-m Class Optical Space Telescopes,” a white paper submitted to the AAAC Exoplanet Task Force (Spring, 2007), available online.
by Paul Gilster | Aug 11, 2007 | Culture and Society |
American aerospace engineer Dandridge MacFarland Cole, who died just over forty years ago, was an early advocate of exploring the asteroids, advocating their eventual colonization in his book Islands in Space: The Challenge of the Planetoids. Alex Michael Bonnici takes a look at this fascinating figure, placing him in the tradition of Tsiolkovsky and Goddard as a futurist whose thinking challenged us to think big. Among his startling ideas was the use of asteroids as interstellar arks or generation ships. Bonnici’s tribute is well deserved and highly recommended.
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The Galaxy Zoo continues to draw remarkable traffic. Launched in mid-July, this project to categorize galactic images taps the volunteer efforts of users from all over the planet. Users have thus far inspected almost seven million images and produced more than 12.3 million galaxy classifications. The Galaxy Zoo has now enrolled 85,000 participants, and is again demonstrating the power of networking to do things computers alone cannot manage as well as humans. Says Daniel Thomas (Portsmouth University): “We now have the world’s largest computer working for us, through the combined power of all these human brains.”
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Neil deGrasse Tyson’s August 5 essay in Parade presented the case for continued space exploration in the context of spin-off technologies that improve our daily lives. A key example was the development of image processing software for the Hubble Space Telescope that was adopted by Georgetown Medical Center for use in tumor detection. Tyson’s emphasis on the multi-disciplinary nature of the space enterprise hits home:
You cannot script these kinds of outcomes, yet they occur daily. The cross-pollination of disciplines almost always creates innovation and discovery. And nothing accomplishes this like space exploration, which draws from the ranks of astrophysicists, biologists, physiologists, chemists, engineers and planetary geologists. Their collective efforts have the capacity to improve and enhance all that we have come to value as a modern society.
Cross-pollination is exactly the right metaphor, and I would add that the growing involvement of the commercial sector in the human space enterprise adds substantially to this process.
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The second European Planetary Science Congress (EPSC) takes place at the Kongress Hotel am Templiner See, Potsdam, Germany from August 20th through 24th, with 500 planetary scientists expected to attend. Topics for the more than forty sessions range from the latest research on terrestrial planets to atmospheres, oceans, planetary moons and the current status of Solar System exploration. Also on the table: A roadmap for future lunar exploration and analysis of SMART-1 data.
by Paul Gilster | Aug 10, 2007 | Astrobiology and SETI |
Life seeded throughout the cosmos makes for a satisfying vision, but what are the odds that some kind of panspermia could really happen? Rutgers researchers cast a bit of cold water on the concept recently with data showing what happens to DNA from microbes frozen for millions of years in Antarctic ice. The upshot: Radiation bombardment in the interstellar depths makes survival unlikely. That makes the Fred Hoyle-style delivery of life via cometary bombardment look improbable.
Antartica makes a good testbed for such studies because the polar regions receive more cosmic radiation than anywhere else on the planet, as well as containing its oldest ices. The DNA in the five samples studied by the research team showed marked decline after 1.1 million years. Rutgers’ Kay Bidle notes that “There is still DNA left after 1.1 million years. But 1.1 million years is the ‘half-life’ – that is, every 1.1 million years, the DNA gets chopped in half.”
Bidle’s team doesn’t completely rule out life being transferred among planets within the Solar System, but finds it unlikely that life on Earth could have arisen from extrasolar sources. Somewhat lost in the shuffle is the impressive news that DNA frozen in glaciers may return to life with glacial melting even after vast periods of time. The team sampled and melted ices ranging from 100,000 to eight million years old looking for microorganisms that had been trapped within.
And find them they did. As expected, the microorganisms from younger ice grew more quickly than their older counterparts. And those in the oldest ice couldn’t be identified at all because of the deterioration in DNA. The ices came from two valleys in the Transantarctic Mountains, a remote and hostile place that reminds us of the incessant mutability of living things, something to be kept in mind as we ponder potential habitats on other planets both in our system and beyond.
The paper is Bidle, “Fossil genes and microbes in the oldest ice on Earth,” published online on August 8 by Proceedings of the National Academy of Sciences (abstract). I’ll post the print reference when it becomes available.
