Archives

‘Blobs’ Flag Early Galaxy Formation

by Paul Gilster | Jun 30, 2009 | Deep Sky Astronomy & Telescopes | 2 Comments

Look back far enough in time (and hence far enough in distance) and you see things that don't correspond to nearby cosmic objects. The so-called 'Lyman-alpha blobs' that astronomers have found associated with young, distant galaxies are a case in point. Huge collections of hydrogen gas (some of them the largest single objects yet found in the universe), they're bright at optical wavelengths, raising the question of what powers the glow and how they factored into the galaxy formation process. New research may be offering an answer. The key is something called 'feedback,' a stage in galaxy formation that shows the interplay between galaxies and the intergalactic medium. Here, the cooling of gas within the dark matter halos enshrouding a young galaxy is countered by heating from active galactic nuclei (think supermassive black holes), which helps to enrich intergalactic space and also slow down star formation. Image: An artist's representation showing what one of the galaxies inside a...

Finding Life in the Ice

by Paul Gilster | Jun 29, 2009 | Astrobiology and SETI | 10 Comments

As we contemplate using long-range tools like spectroscopy to examine distant exoplanets for life, we're also developing the hands-on equipment we'll need for seeking it out in our own Solar System. Project SLIce (Signatures of Life in Ice) is a case in point, an attempt to study how organic material behaves in ice on other worlds by using Earth settings as an analogy. On that score, the archipelago of Svalbard has proven to be a helpful testbed. Located in the Arctic Ocean between Norway and the North Pole, Svalbard is icy and spectacular. The image below conjures up memories of a nautical journey I took around Iceland in the 1970s, with white-capped seas pushing up against snow-clad peaks. The SLIce team sees Svalbard as a laboratory for looking for extant or extinct life, and a place to develop the protocols for working with rovers in operating environments like Mars. Image: I love Iceland, but pushing as far north as Svalbard would really bring out the adventurer in me. Here we...

A Cometary Closeup for NExT

by Paul Gilster | Jun 26, 2009 | Asteroid and Comet Deflection | 3 Comments

By Larry Klaes Apropos of yesterday's story on the possible cometary origin of the Tunguska Event in 1908, Tau Zero journalist Larry Klaes looks at the NExT (New Exploration of Tempel) mission, which gives us a second crack at observing comet Tempel 1. Ancient artifacts of the early Solar System, comets can tell us much about its earliest days, but as Larry points out, getting data out of the Deep Impact mission proved to be unexpectedly complicated. NExT is a useful re-purposing of an earlier mission that may unlock further cometary secrets when it returns to Tempel 1 in 2011. If a comet did cause Tunguska, here's hoping such events continue to be rare, but in the meantime, garnering all the information we can about how comets are made is as important for planetary security as it is for the study of Solar System origins. An Impact to Remember Late on the Fourth of July in 2005, while fireworks brightened the sky across the United States, another group of American citizens were...

Comet Implicated in Tunguska Blast

by Paul Gilster | Jun 25, 2009 | Asteroid and Comet Deflection | 9 Comments

Back in my flying days, I found myself becoming absorbed with meteorology, enough to wind up teaching the subject in various flight school settings. I was no expert, but looking for clues on flying conditions in the next few hours by studying cloud formation and movement was fascinating. In all that time, the one cloud phenomenon I always wanted to see but never did was the noctilucent cloud, an unusual, lovely formation made up of ice particles that occurs at extremely high altitudes. 'Noctilucent' means 'night-shining,' and that's just what these clouds do when they're illuminated by sunlight from below the horizon. Space Shuttle launches have been found to generate them as the vehicle pumps about 300 metric tons of water vapor into the thermosphere, the layer of atmosphere beginning at about ninety kilometers above the surface, just above the mesosphere. Photographs of such clouds show a unique beauty, though it's one that might also seem eerie, at least in certain settings. For...

Enceladus: Riddle of the Plumes

by Paul Gilster | Jun 24, 2009 | Outer Solar System | 4 Comments

Is there really an underground ocean on Enceladus? The Cassini spacecraft's striking images have created a cottage industry in speculation, with spectacular glimpses of erupting plumes composed of ice and water vapor. This week, however, we get two contrasting views on what all this means. In one, a paper in Nature by a European team led by Frank Postberg (Universität Heidelberg), studies of sodium salts in dust ejected by the Enceladus plumes reveal telltale signs of a salty ocean deep below the surface. Postberg was working with data from the Cosmic Dust Analyzer (CDA) instrument aboard Cassini, and the results imply a level of sodium chloride that may be as high as that found in Earth's oceans. The data come from ice grains in Saturn's E-ring, which is thought to consist largely of material from Enceladus. Thus we seem to be gathering direct evidence for the presence of the hypothesized ocean, which should be salty from long contact with the rocky core. But not so fast. The same...

SETI: A Detectable Neutrino Signal?

by Paul Gilster | Jun 23, 2009 | Astrobiology and SETI | 24 Comments

Somehow I never thought of the IceCube neutrino telescope as a SETI instrument. Deployed in a series of 1,450 to 2,450 meters-deep holes in Antarctica and taking up over a cubic kilometer of ice, IceCube is fine-tuned to detect neutrinos. That makes it a useful tool for studying violent events like galactic collisions and the formation of quasars, providing insights into the early universe. But SETI? Perhaps, says Zurab Silagadze (Novosibirsk State University), who notes that most SETI work in the past has focused on centimeter wavelength electromagnetic signals. Says Silagadze: Here we question this old wisdom and argue that the muon collider, certainly in reach of modern day technology... provides a far more unique marker of civilizations like our own [type I in Kardashev's classification... Muon colliders are accompanied by a very intense and collimated high-energy neutrino beam which can be readily detected even at astronomical distances. Image: The IceCube array in the deep ice,...

TESS Mission Fails to Make the Cut

by Paul Gilster | Jun 22, 2009 | Missions | 13 Comments

NASA has made its choices, and TESS is not one of them. The Transiting Exoplanet Survey Satellite would have used six telescopes to observe the brightest stars in the sky, a remarkable 2.5 million of them, hoping to find more than 1,000 transiting planets ranging in size from Jupiter-mass down to rocky worlds like our own. An entrant in the agency's Small Explorer program, TESS could have accelerated the time-frame for discovering another habitable world, assuming all went well. Not that we don't have Kepler at work on 100,000 distant stars, looking for transits that can give us some solid statistical knowledge of how often terrestrial (and other) planets occur. And, of course, the CoRoT mission is actively in the hunt. But TESS would have complemented both, looking at a wide variety of stars, many of which would have been M-dwarfs. Not long ago I referred to a Greg Laughlin post that noted a 98 percent probability that TESS would locate a potentially habitable transiting planet...

Brute-Force Engineering and Climate

by Paul Gilster | Jun 19, 2009 | Culture and Society | 36 Comments

The eruption of Mt. Tambora in Indonesia in 1815 pumped so much sulfur dioxide into the stratosphere that New England farmers found their fields frosted over in July. Climate change, it seems, can be quick and overwhelming, at least on short scales. The eruption of the Mt. Pinatubo in the Philippines in 1991 cooled global temperatures for several years by about half a degree Celsius. Sulfur dioxide works. So how about this: We send a fleet of airships high into the stratosphere, attached to hoses on the ground that pump 10 kilos of sulfur dioxide every second. The airships then spew this mix into the upper atmosphere, a aerosolized pollutant that, turning the skies Blade Runner red, shields the planet from the Sun's heat. Call it geo-engineering, an extreme form of human climate manipulation that is the subject of a recent story in The Atlantic. Into the Anthropocene Writer Graeme Wood notes that our activities have been transforming the planet for centuries now, leading some to dub...

Huge Outburst from a Magnetar

by Paul Gilster | Jun 18, 2009 | Deep Sky Astronomy & Telescopes | 6 Comments

We get yet another example of space-based observatories complementing each other with the recent outburst of X-rays and gamma rays detected last August. The Swift satellite first noted the event on August 22, while the European Space Agency's XMM-Newton satellite began making detailed spectral studies of the radiation twelve hours later, followed by the Integral observatory. The outburst went on for more than four months, accompanied by hundreds of smaller bursts. The source for these events was a magnetar, a type of neutron star that is the most highly magnetized object known, with a magnetic field some 10,000 million times stronger than Earth's. The new magnetar, christened SGR 0501+4516, is of the type known as Soft Gamma-Ray Repeaters (SGR), and is the first such found in the last decade. Magnetars are known for spectacular periods of irregular burst activity, changing their luminosity up to ten orders of magnitude on timescales of just a few milliseconds. We occasionally discuss...

Two Angles on Meteorites

by Paul Gilster | Jun 17, 2009 | Asteroid and Comet Deflection | 7 Comments

Meteorites are in the news in two starkly different ways this week, but I'll lead with a story that has implications for how planetary systems like ours are born. Philipp Heck (University of Chicago) and colleagues have been analyzing interstellar grains from the Murchison meteorite, a large object that fell near the town of Murchison, Victoria in Australia in 1969. The Murchison grains are thought to have been blown into space by dying stars long before the formation of Earth. We'd like to know more about such grains because they became incorporated into the earliest solids forming in the Solar System, and hence offer a window into that era. Moreover, their composition helps us understand a bit more about their history. "The concentration of neon," says Heck, "produced during cosmic-ray irradiation, allows us to determine the time a grain has spent in interstellar space." Image: A fragment of the Murchison meteorite. Copyright New England Meteoritical Services, 2001. The...

Notes & Queries 6/16/09

by Paul Gilster | Jun 16, 2009 | Culture and Society | 18 Comments

Life Beneath the Ice Three kilometers down in the Greenland ice sheet is what I call an extreme environment. Even so, Penn State researchers have been able to bring a bacterium called Herminiimonas glaciei back to life after a dormancy of 120,000 years in these conditions. The work involved incubating the samples at 2 degrees Celsius for seven months, then at 5 degrees Celsius for a further four and a half, a patient process rewarded by the appearance of the purple-brown bacteria. Ten to fifty times smaller than E. coli, Herminiimonas glaciei evidently used its size to survive in liquid veins amongst the ice crystals. Jennifer Loveland-Curtze describes the find: "These extremely cold environments are the best analogues of possible extraterrestrial habitats. The exceptionally low temperatures can preserve cells and nucleic acids for even millions of years. H. glaciei is one of just a handful of officially described ultra-small species and the only one so far from the Greenland ice...

A Longer Life for Earth’s Biosphere?

by Paul Gilster | Jun 15, 2009 | Astrobiology and SETI | 15 Comments

If we can find a way to double the lifespan of Earth's biosphere, we'll have changed the odds for finding extraterrestrial civilizations. After all, the amount of time an advanced culture can exist is one of the variables in the famous Drake equation, which estimates how many intelligent civilizations there are in the Milky Way. Lengthen potential habitability and you give any civilization that much more chance to spread into the cosmos. Thus recent work out of Caltech intrigues us in several directions. Joseph Kirschvink and colleagues look at effects that could add a billion years on to our planet's projected habitability. Consider: Earth took some four billion years to develop intelligent life, leaving us about a billion before our planet becomes uninhabitable. That result would be caused by a brighter and hotter Sun, the loss of carbon dioxide in the atmosphere through the weathering of rocks, and the eventual evaporation of water from the oceans, leaving nothing alive. Reducing...

Modeling an Interstellar Future

by Paul Gilster | Jun 13, 2009 | Culture and Society | 3 Comments

The bet between Tibor Pacher and myself continues to draw emails, proving that my friend Tibor was right when he saw an interstellar wager as a teaching opportunity. I still maintain that an interstellar mission will not be launched anywhere near as early as 2025, but Tibor does have his advocates, as you can see on the Long Bets site. Moreover, it's been useful to plug in distances and velocities for a 2000-year mission to a place like Proxima Centauri when I speak to audiences about how large the distance between the stars really is. 2000 years is a long time, but we're still talking 650 kilometers per second, and just 20 years to the Oort Cloud! And as a guy who used to build model airplanes back in my youth, first in plastic and then from balsa wood (wonderful memories of working with kits of World War I and II aircraft from Guillow), I can relate to Tibor's latest venture. MiniSpaceWorld is an attempt to create, at a European site still to be determined, a wide-ranging exhibit...

Earthlight’s Bio-signature Measured

by Paul Gilster | Jun 12, 2009 | Astrobiology and SETI | 5 Comments

Among the most interesting of the future missions now being weighed by NASA, TESS (the Transiting Exoplanet Survey Satellite) would help scientists using the James Webb Space Telescope know where to look for Earth-like planets around nearby stars. While the invaluable Kepler mission scans 100,000 distant stars, hoping to gain statistics on Earth-sized exoplanets, TESS would have a different aim, looking for transiting terrestrial worlds around only the brightest stars. A 2012 launch is possible if the mission is approved. Here's Greg Laughlin (UC-Santa Cruz) on TESS' possibilities: TESS... provides the cheapest, shortest, and most direct path to the actual characterization of a potentially habitable planet. Included in the 2.5 million brightest stars are a substantial number of M dwarfs. Detailed Monte-Carlo simulations indicate that there's a 98% probability that TESS will locate a potentially habitable transiting terrestrial planet orbiting a red dwarf lying closer than 50 parsecs....

A Planetary Detection in Andromeda?

by Paul Gilster | Jun 11, 2009 | Exoplanetary Science | 10 Comments

Gravitational microlensing has been actively employed in the search for MACHOs (Massive Astrophysical Compact Halo Objects) in the galactic halo, although with ambiguous results. The idea here is to find large, dark objects by detecting the microlensing effects they produce on stars behind them. While these dark matter studies have looked toward the Large Magellanic Cloud, we are using the same technique elsewhere in the planet hunt, finding that exoplanets can magnify the light of stars behind them in the galactic bulge, producing a clear detection. Remember, for this kind of work, you want a dense background field of stars because the alignment needed for microlensing is obviously rare. The Magellanics are ideal, as is the galactic bulge, and so, for that matter, is M31, the Andromeda galaxy. And if our early exoplanet work, relying on radial velocity and transit methods, has naturally produced large planets in the Jupiter class, microlensing can be quite effective at smaller...

Planets Forming Around a Close Binary

by Paul Gilster | Jun 10, 2009 | Exoplanetary Science | 7 Comments

Planets around binary stars continue to be a major interest here, given our fascination with nearby Alpha Centauri. Thus the recent radio interferometry images captured by the Submillimeter Array radio telescope system (Mauna Kea) come right to the top of the queue. We're looking at a young binary system called V4046 Sagittarii, providing a glimpse of planetary system formation occurring around two stars of roughly the Sun's mass. This system is approximately 240 light years from our own. Image: Submillimeter Array image of the rotating, gaseous disk surrounding the young twin-star system V4046 Sagittarii (located at the white dot in the image). Note the size of the V4046 Sagittarii disk relative to the orbit of Neptune, shown to scale at the lower right (the filled oval at lower left represents the size of the smallest structures that could be detected in the image). The disk is tipped from our perspective, such that it appears as elliptical rather than circular. The image is...

Alpha Centauri Hunt Intensifies

by Paul Gilster | Jun 9, 2009 | Exoplanetary Science | 20 Comments

I love Greg Laughlin's remark to the Washington Post's Joel Achenbach in last week's article Astronomers Seek New Home Closer to Home. Having discussed Debra Fischer's ongoing search for Alpha Centauri planets and his own theories on planet formation around binary stars, Laughlin points out where we stand today: "We have what is to all appearances by far the best planet in the galaxy. And we have no workable backup plan." The Washington Post article doubtless draws on Lee Billings' earlier piece in SEED Magazine called The Long Shot, which discusses with an elegance rare in science writing the attempt to find planets around the Centauri stars by Fischer as well as Michel Mayor's Geneva team. Mayor has been using the High Accuracy Radial velocity Planet Searcher (HARPS) instrument at La Silla, the Cadillac of radial velocity instrumentation (and boy does that auto industry reference date me!). Competition can work wonders, and having two teams on the case can only bode well for quick...

Tuning Up the Interstellar Ramjet

by Paul Gilster | Jun 8, 2009 | Advanced Rocketry | 15 Comments

Catching my eye in the latest Carnival of Space, hosted by Brian Wang at Next Big Future, is Adam Crowl's write-up of a rethinking of an exotic ramjet technology. Robert Bussard put the interstellar ramjet into the public eye back in 1960 in a paper proposing that a starship moving fast enough would be able to use the hydrogen between the stars as a source of fuel, enabling a constant acceleration at one g. You'll recognize the Bussard ramjet in Poul Anderson's classic novel Tau Zero (originally published in Galaxy in 1967 as To Outlive Eternity). The Problem with Slow Fusion Anderson's 'Leonora Christine' was a runaway starship, accelerating ever closer to lightspeed until she was punching through entire galaxies in times experienced by the crew as mere minutes. But we don't have to get quite that extreme with the Bussard idea. It's built around the premise of gathering fuel along the way so as to avoid the vast mass ratio problems of conventional rocketry. We can imagine an...

SETA: Finding a ‘Graveyard Civilization’

by Paul Gilster | Jun 5, 2009 | Astrobiology and SETI | 38 Comments

Imagine an extraterrestrial civilization that manages to colonize the entire galaxy. Then imagine the colonizing civilization collapsing so definitively that no trace of its existence has yet been detected, at least from our planet. We can call it, as Jacob Haqq-Misra and Seth Baum (Pennsylvania State University) do in a recently released paper, a 'graveyard civilization,' one whose remains might still be accessible provided we know where and how to look. Pushing the Limits of Growth What could bring down such a civilization? The idea here is that we can explain the Fermi paradox ('Where are they?') by assuming that exponential growth is not a sustainable development pattern for intelligent civilizations. The authors draw on human experience in analyzing this possibility. Here's the gist of it: The consequences of unsustainable development are often dire. In many documented cases, resource depletion caused by human activities has led to the permanent collapse of human populations,...

Slow Weather on Titan

by Paul Gilster | Jun 4, 2009 | Outer Solar System | 8 Comments

With a dense atmosphere of nitrogen and methane, Titan is the only moon in our Solar System that shares Earth-like characteristics in climate. But Titan's climate, receiving one hundred times less sunlight at ten times Earth's distance from the Sun, operates at a much slower pace. The seasons on the distant moon last more than seven Earth years, and the motion of its clouds is slow and deliberate. We've had a good look via the Cassini spacecraft at the movement of those clouds, some two hundred of them being examined between July 2004 and December 2007 in a study of global circulation patterns. Summer changes to fall at the equinox in August of this year. We're at a time when the circulation models say clouds in the southern latitudes should have already disappeared, but it's clear from the Cassini imagery that many clouds remained as late as 2007. Image: This infrared image of Saturn's moon Titan shows a large burst of clouds in the moon's south polar region. These clouds form and...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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