A ‘Benchmark’ Brown Dwarf

by | Nov 23, 2010 | | 17 Comments

The WISE mission has received a lot of press in terms of discovering nearby brown dwarfs, but it's clear that finding low-temperature objects is a major investigation at many Earth-bound sites as well. That includes the UKIRT (United Kingdom Infrared Telescope) Deep Sky Survey's project to find the coolest objects in our galaxy, an effort that has paid off in the form of a unique binary system. One of the stars here is a cool, methane-rich T-dwarf, while the other is a white dwarf, the two low-mass stars orbiting each other though separated by a quarter of a light year. Understanding Brown Dwarf Atmospheres We need to put this find in context. In the absence of hydrogen fusion at the core, brown dwarfs depend upon gravitational contraction as their internal energy source. Cooling slowly over time as they shed their energies, brown dwarfs emit most of their radiation in the infrared, with spectra showing absorption bands of water, methane, carbon monoxide and other molecules in the...

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Mission News: Sails, Nebulae, Comets

by | Nov 22, 2010 | | 1 Comment

NanoSail-D is now in space, following a successful launch on the 19th that involved eight satellites for university research programs and the US government. The sail experiment was carried aboard FASTSAT (the Fast Affordable Science and Technology Satellite) and is scheduled for release seven days after launch, with sail deployment three days later. We'll soon know how well the deployment of the sail -- a five second process -- proceeds, but how energizing to have another sail experiment in motion as we continue to shake out this technology. The NanoSail Twitter feed (@NanoSailD) is active and bears an uncanny resemblance to the amiable, chatty and often obscure IKAROS tweets from that mission's launch. Colorful Imagery from WISE Meanwhile, other missions continue to pop up with intriguing results, including WISE (Wide-field Infrared Survey Explorer), which has been surveying the sky at infrared wavelengths since January and is now on its NEOWISE mission, the extended sequence of...

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Status Report on the Tau Zero Foundation

by | Nov 19, 2010 | | 39 Comments

by Marc Millis A number of things have been happening recently with the Tau Zero Foundation, but most of them have been behind the scenes. Marc Millis, founding architect of the TZF and former head of NASA's Breakthrough Propulsion Physics project, now goes public with his thoughts on recent activities and where the Foundation is heading. To the fans and contributors of Tau Zero, thanks for your help and suggestions. It's time to talk about recent progress and next-steps. One major news item is that I took an early retirement from NASA, in February 2010, so that I could devote more time to Tau Zero. As much as I tried, I could not do both. I had to make the hard choice between following NASA or leaving that full-salary day-job to make advances via the more flexible Tau Zero Foundation. Now that I'm free of prior restrictions, we are restructuring how we operate and will be eventually shifting to a "Membership" format with regular newsletters. During the first week in November, I met...

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A Red Giant Planet of Extragalactic Origin

by | Nov 18, 2010 | | 11 Comments

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...

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A Second Life for NanoSail-D

by | Nov 17, 2010 | | 6 Comments

I notice that the Planetary Society is doing some fundraising for its LightSail program, in this case looking for money to help build a spare for the LightSail craft. Lou Friedman puts it this way in a recent mailing: "We need to build a spare to insure our plans. It's the prudent move; much cheaper than purchasing insurance and building an entire new back-up craft, as long as we do it now, while the first spacecraft is being built." The cost of a back-up craft during this window is roughly $200,000. Some basics about LightSail-1: Its mylar sails are 4.5 microns thick, the thinnest ever made for spaceflight. When they deploy, they'll extend to cover 32 square meters, and the four sails should throw quite a reflection, acting like mirrors that would be visible from Earth and may appear brighter than any visible star or planet. The vehicle is to be formed from three CubeSat spacecraft, forming a 'bus' about the size of a shoebox that weighs about 4.5 kilograms. We've covered the...

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Fermi Bubbles: Remnants of an Ancient Jet?

by | Nov 16, 2010 | | 3 Comments

Did the Milky Way once have a jet powered by matter falling into the supermassive black hole at galactic center? There is little evidence for an active jet today, but we do see jets like these in so-called 'active galaxies,' those that show higher than normal luminosity over much of the electromagnetic spectrum. Some jets in active galaxies can be thousands of light years long, evidently emerging from each face of the accretion disk around a central black hole in the so-called active galactic nucleus (AGN). And on a smaller level, we've found similar jets emerging from the accretion disks around neutron stars and stellar-mass black holes. Image: Streaming out from the center of the galaxy M87 like a cosmic searchlight is one of nature's most amazing phenomena, a black-hole-powered jet of electrons and other sub-atomic particles traveling at nearly the speed of light. In this Hubble telescope image, the blue jet contrasts with the yellow glow from the combined light of billions of...

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A FOCAL Mission into the Oort Cloud

by | Nov 15, 2010 | | 29 Comments

After all this time, I'm still trying to wrap my head around the idea of massive objects in space as lenses, their distortion of spacetime offering the ability to see distant objects at huge magnification. On Friday we saw how the lensing effect caused by galactic clusters can be used to study dark energy. And consider the early results from the Herschel-ATLAS project, conducted by ESA's Herschel Space Observatory. Herschel is scanning large areas of the sky in far-infrared and sub-millimeter light. Many of its brightest sources turn out to be magnified by gravitational lenses, where light from a very distant object passes a galaxy much closer to the Earth, bending that light so that the image of the more distant galaxy is magnified and distorted. Because Herschel has only covered one-thirtieth of the entire Herschel-ATLAS survey area, it's likely that the project will uncover hundreds of gravitational lenses, offering astronomers the chance to probe galaxies in the early universe...

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Gravitational Lensing Probes Dark Energy

by | Nov 12, 2010 | | 13 Comments

Abell 1689 is one of the most massive clusters of galaxies known, making it a superb venue for the study of dark matter. That's because the cluster, some 2.2 billion light years away, creates gravitational lensing that magnifies and distorts the light from galaxies far beyond it. Astronomers used Abell 1689 in 2008 to identify one of the youngest and brightest galaxies ever seen, a galaxy in existence a mere 700 million years after the beginning of the universe. That find, A1689-zD1, turned out to be ablaze with star formation in an era when stars were only beginning to emerge. New Hubble studies have now used Abell 1689 yet again to make some of the most detailed maps yet of dark matter. The idea is this: The cluster's gravitational lensing bends and amplifies the light of objects beyond it. The researchers, led by JPL's Dan Coe, go to work on the distorted images that result, figuring out the mass it would take to produce them. If the galaxies we see in the cluster were the sole...

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Hartley 2: Primordial Dry Ice

by | Nov 11, 2010 | | 9 Comments

Keep an eye on the EPOXI site at the University of Maryland. New images from the Hartley 2 comet encounter are coming in, some of them truly breathtaking, as is the one at left. The jets clearly visible in the image can be linked with distinct areas on the surface of the comet, the first time we've ever seen a comet with this degree of clarity. Image by image, the tiny comet is yielding its secrets. We now learn that spectral analysis of the material coming from the cometary jets shows it to be primarily carbon dioxide, along with dust and ice particles. Image: This enhanced image, one of the closest taken of comet Hartley 2 by NASA's EPOXI mission, shows jets and where they originate from the surface. There are jets outgassing from the sunward side, the night side, and along the terminator -- the line between the two sides. The image was taken by EPOXI's Medium-Resolution Instrument on Nov. 4, 2010. The sun is to the right. Credit: NASA/JPL-Caltech/UMD. Jessica Sunshine (University...

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WISE: First Ultra-cool Brown Dwarf

by | Nov 10, 2010 | | 32 Comments

"To a man with a hammer, everything looks like a nail," said Mark Twain, one take on which is that the way we see problems shapes how we see solutions. That fact can be either confining or liberating depending on how open we are to examining our preconceptions, but in the case of Amy Mainzer (JPL), it leads to a natural way to describe a failed star. Mainzer, who is deputy project scientist on the Wide-field Infrared Survey Explorer mission (WISE), is an amateur jewelry-maker. For her, it's easy to look at the image below and see gems. "The brown dwarfs," says Mainzer, "jump out at you like big, fat, green emeralds." And that emerald below, dead center in the image, is hard to miss. Image: The green dot in the middle of this image might look like an emerald amidst glittering diamonds, but it is actually a dim star belonging to a class called brown dwarfs. This particular object, named "WISEPC J045853.90+643451.9" after its location in the sky, is the first ultra-cool brown dwarf...

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The Poetry of SETI

by | Nov 9, 2010 | | 5 Comments

Stephen Baxter's "Turing's Apples," which originally ran in a collection called Eclipse Two (2008), is an intriguing take on SETI and the problem of extracting meaningful information from a signal. It's a bit reminiscent of Fred Hoyle's A for Andromeda (1962) in that the SETI signal received on Earth contains instructions for building something that may or may not pose a threat to our species. Sorting out the issue involves discussion of information theory and Shannon entropy analysis. Say again? Best to handle this by quoting from the story. In this scene, the protagonist's brother, who is obsessed with the signal his team has received from the direction of the Eagle Nebula and, ultimately, the galactic center, is explaining how information is being extracted from it. Shannon entropy analysis looks for relationships between signal elements. The brother goes on: "You work out conditional probabilities: Given pairs of elements, how likely is it that you'll see U following Q? Then you...

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Of Comets and Deep Space Aspirations

by | Nov 8, 2010 | | 11 Comments

The Hartley 2 flyby was an outstanding event, and the only thing I regret about my recent travels was that I was unable to follow the action as the images first streamed in. By now, sights like the one at left have made their way all over the Net, so I won't dwell on them other than to say that if you haven't seen the short video clip of the EPOXI flyby, you should definitely give it a look. You're getting the view from a spacecraft that closed to 700 kilometers or so of the surface, during an encounter taking place at a speed of 12.3 kilometers per second. Image: Comet Hartley 2 can be seen in glorious detail in this image from NASA's EPOXI mission. It was taken as the spacecraft flew by around 6:59 a.m. PDT (9:59 a.m. EDT), from a distance of about 700 kilometers (435 miles). Jets can be seen streaming out of the nucleus. Image credit: NASA/JPL-Caltech/UMD. I'll go along with EPOXI principal investigator Michael A'Hearn's description of the comet's "stark, majestic beauty."...

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Beyond Hartley 2: EPOXI’s Hunt for Exoplanets

by | Nov 4, 2010 | | 1 Comment

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...

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Closing on Hartley 2

by | Nov 3, 2010 | | 3 Comments

With NASA's EPOXI mission closing on comet Hartley 2 at 12.5 kilometers per second, be aware that live coverage of the close encounter will begin at 1330 UTC (0930 EDT) on Nov. 4 from mission control at the Jet Propulsion Laboratory. NASA TV streaming video will be available, and you should also be able to watch the action on a JPL Ustream channel. Finally, NASA's Eyes on the Solar System Web tool, a 3-D environment for Solar System exploration, is available for viewing a real-time animation of the cometary flyby on your PC. EPOXI is a great instance of re-purposing a spacecraft to extract maximum value. This is the Deep Impact vehicle that gave us such a spectacular view of the impactor smash-up on comet Tempel 1 back in the summer of 2005. Under the name EPOXI, the mission has pressed ahead with two separate objectives, the first being EPOCh, or Extrasolar Planet Observation and Characterization, which has involved a number of nearby stars known to have transiting exoplanets. The...

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Millis: Thoughts on the ‘100-Year Starship’

by | Nov 2, 2010 | | 19 Comments

by Marc Millis When Pete Worden (NASA Ames) spoke to the Long Now Foundation recently, he surely didn't realize how much confusion his announcement of a '100-Year Starship' study would create. The news coverage has been all over the map and frequently incorrect, ranging from intimations of a coverup (Fox News) to mistaken linkages between the study and competely unrelated talk about one-way missions to Mars (the Telegraph and many other papers). What's really going on in this collaboration between NASA and DARPA? Marc Millis has some thoughts on that based on his own talks with the principals. Millis, former head of NASA's Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, here puts some of the myths to rest and explains where the 100-Year Starship fits into our future. If you have not yet heard, there's been a bit of news flurry over the announcement that DARPA is funding NASA Ames to the tune of $1M for a one-year study for a "100-Year...

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Enchanted with the Outer System

by | Nov 1, 2010 | | 13 Comments

It's staggering how much our view of the Solar System has changed over the past few decades. The system I grew up with seemed a stable place. The planets were in well-defined orbits out to Pluto and, even if it were always possible another might be found, it surely couldn't pose any great surprise in that great emptiness that was the outer system. But today we routinely track trans-Neptunian objects with diameters over 500 kilometers -- about 50 of these have now been found, and some 122 TNOs at least 300 kilometers in diameter. We know about well over a thousand objects in that ring of early system debris called the Kuiper Belt. It's an increasingly messy place, this outer Solar System, and it has its own terminology. We have centaurs and plutinos, resonance objects, cubewanos, scattered disk objects (SDOs), Neptune trojans, damocloids, apollos and, perhaps, inner Oort cloud objects. Nope, this isn't the Solar System I grew up with, and every new discovery adds to the enchantment....

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Astrobiology and the Kuiper Belt

by | Oct 29, 2010 | | 9 Comments

Here's an interesting bit of news from the New Horizons team. Remember that the spacecraft, having made its pass by the Pluto/Charon system in 2015, will be moving ever deeper into the Kuiper Belt. It's been the hope of mission planners that a close study of one or more objects there might be possible. Now astronomer Scott Sheppard (Carnegie Institution of Washington) has announced that he has detected the first asteroid in Neptune's trailing Trojan zone (the planet's L5 point), an area New Horizons will fly through before arriving at the Pluto/Charon binary. 2008 LC18 is not itself in range for a New Horizons flyby, but mission principal investigator Alan Stern notes its significance in a recent report on the mission's Web site: " ...its discovery shows that additional and potentially closer Neptune Trojans that New Horizons might be able to study could be discovered in the next three years." And that gives us an interesting mission extension for New Horizons, to take advantage of...

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Crunching the Numbers on Earth-Size Planets

by | Oct 28, 2010 | | 30 Comments

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...

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Ocean Impacts and Their Consequences

by | Oct 27, 2010 | | 15 Comments

It's good to see asteroid deflection occasionally popping up in the news, thanks to the efforts of people like former astronaut Rusty Schweickart, whose efforts as co-chairman of the Task Force on Planetary Defense of the NASA Advisory Council are complemented by his work for non-profits like the B612 Foundation. Schweickart is worried about the potential consequences of even a small asteroid impact, pointing to the Tunguska event of 1908, in which 800 square miles of Siberian forest were flattened in the kind of strike that occurs every 200 to 300 years. Bigger asteroids are, obviously, a far greater danger, and while they're much rarer, they do have the capability of wiping out entire species, as may well have occurred some 65 million years ago in the destruction of the dinosaurs. In his recent New York Times article, Schweickart notes what we need to do: With a readily achievable detection and deflection system we can avoid their same fate. Professional (and a few amateur)...

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‘Snowball Growth’ and the Centauri Stars

by | Oct 26, 2010 | | 10 Comments

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...

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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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