This is an active and interesting program well worth your attention, and its Web presence is ably enlivened by Wayne Hall, who presents the current Carnival materials. Of these, I point you to Colony Worlds and its enjoyable musings on dogs in space. Headed out for Mars for a couple of years, or perhaps planning on settling in a distant colony, maybe an O’Neill habitat somewhere out around L-5? If so, you’ll get a kick out of Darnell Clayton’s reasons why your dog may be your best traveling companion. All of which reminds me of one of the wilder dreams I’ve ever had, about one of my Border Collies being sent Laika-style aboard a spacecraft bound for Neptune…

Also intriguing from the mix is Ian O’Neill’s short piece on black holes, and the results of a computer simulation that rammed two black holes into each other at close to the speed of light. The question: What happens to the event horizon after so cataclysmic an event? Can a black hole exist without one? The results from this work by Emanuele Berti and team at the Jet Propulsion Laboratory were intriguing:

Unlike previous simulations examining lower-energy collisions, far more energetic gravitational waves were produced. So much so that 14% of the total masses of the colliding black holes were converted into gravitational wave energy. So far so good. If this extreme (and unlikely) scenario were to occur, perhaps we’d know what to look out for in the noisy LIGO data, and we might gain an estimate of how much mass black holes shed in these encounters. However, there’s another outcome to Berti’s research: black holes keep their event horizons no matter what is thrown at them.

An event as powerful as this is gravitationally interesting, but it’s also of note in relation to Roger Penrose’s musings on so-called ‘naked’ singularities, which suggest there is no way they can exist in nature. Exactly how such ‘cosmic censorship’ might work is an open question — Ian notes that you can work out the math to show that a singularity could exist without an event horizon — but in any case, we have no idea what a naked singularity would look like if it did exist, making this theorizing unlikely to move into the realm of observational data any time soon.

The extrasolar component of EPOXI is called EPOCh, for Extrasolar Planet Observation and Characterization, and it primarily involves an examination of stars with known transiting planets, looking for other planets in the system (EPOXI can detect transits of objects down to about half the diameter of the Earth) or possibly moons around the known ones. Meanwhile, the spacecraft continues its journey to comet Hartley 2 for observations there, its extrasolar investigation limited by the exigencies of the cometary mission.

But Venus Express, now in orbit around the second planet, is likewise helping us learn about distant worlds by a closer examination of our own. As seen through the cameras aboard the spacecraft, the Earth spans less than a pixel, which is all we can expect to see when we get the technologies in place to isolate light from Earth-sized worlds elsewhere in the cosmos. We need to know how to interpret potential habitability, in other words, with precious little information, and Venus Express can help.

It will be useful to know, for example, whether green plants, bright in the near infrared, can be discerned. For that matter, spectral observations can reveal information about planetary weather systems and the location of glaciers and oceans. Thus far the team is finding the work a challenge. “We see water and molecular oxygen in Earth’s atmosphere, but Venus also shows these signatures. So looking at these molecules is not enough,” says Giuseppe Piccioni (IASF-INAF, Rome).

A necessary next step is to compare the spectra of Earth’s oceans with spectra taken when continents dominate the view. David Grinspoon (Denver Museum of Nature & Science), who suggested these observations, calls this “…the first sustained program of Earth observation from a distant platform,” unlike the fleeting EPOXI images.

Image: This image composite shows the signatures of methane (CH4), carbon dioxide (CO2), ozone (O3) and nitrous oxide (N2O), minor species of the Earth’s atmosphere but powerful greenhouse gases, detected by the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS) on board ESA’s Venus Express at infrared wavelengths, while the spacecraft was pointing Earth along its orbit around Venus. Our planet was just a pixel in VIRTIS’s field of view. These observations are relevant as they proof that a distant planet such as an extra-solar planet can reveal to an instrument like VIRTIS the signatures of chemical compounds composing the atmosphere and surface. Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA (Earth views: Solar System Simulator JPL-NASA).

Approximately forty images of our planet have been collected in both the visible and near-infrared regions of the spectrum. What can they tell us about Earth’s atmosphere and its life-bearing capacities? With Kepler on the horizon and COROT engaged in active work in space, we may one day soon find our attention riveted by a planet whose orbital characteristics point toward habitability. Planet hunter missions beyond these should, perhaps in fifteen years, be able to resolve exoplanets down to terrestrial size. Building the necessary tools will teach us how to proceed when that welcome day arrives.

Then again, nothing about Enceladus should surprise us any longer, including an apparent change in the intensity of the plume, within which trace amounts of organics have been detected. The October 9 approach takes us to a distance closer than any previous flyby of a Saturnian moon, a mere 25 kilometers from the surface, a key objective being to study the composition of the plume with the spacecraft’s field and particle instruments. Thus Tamas Gambosi (University of Michigan, Ann Arbor):

“We know that Enceladus produces a few hundred kilograms per second of gas and dust and that this material is mainly water vapor and water ice. The water vapor and the evaporation from the ice grains contribute most of the mass found in Saturn’s magnetosphere. One of the overarching scientific puzzles we are trying to understand is what happens to the gas and dust released from Enceladus, including how some of the gas is transformed to ionized plasma and is disseminated throughout the magnetosphere.”

Image: This graphic shows the trajectories for the Cassini spacecraft flybys planned for Oct. 9 (E5) and 31, 2008 (E6). During Cassini’s Oct. 9 flyby, the spacecraft’s fields and particles instruments will venture deeper into the plume than ever before, directly sampling the particles and gases. The emphasis here is on the composition of the plume rather than imaging the surface. Image credit: NASA/JPL.

The October 31 flyby, closing to 196 kilometers, will image the tiger stripe region again, with both encounters offering the chance to find still further changes around this deeply interesting object. With four more Enceladus flybys planned for the next two years of the Cassini Equinox Mission — the name for Cassini’s extended mission — we can hope to learn more about what powers its geysers. We may also find clues to the moon’s past, since the different isotopes found in that environment could help to identify the temperatures at work during the formation of Enceladus.

Note: NASA’s Cassini flyby blog is now active.

David Morrison (NASA Ames) has written about the public response to a small impact scenario, a fact I’m drawing from the recent update of NEO News sent to me by Larry Klaes. Also available is a report from spaceweather.com of a visual sighting of the event, sent along by Jacob Kuiper, general aviation meteorologist at the National Weather Service in the Netherlands::

“Half an hour before the predicted impact of asteroid 2008 TC3, I informed an official of Air-France-KLM at Amsterdam airport about the possibility that crews of their airliners in the vicinity of impact would have a chance to see a fireball. And it was a success! I have received confirmation that a KLM airliner, roughly 750 nautical miles southwest of the predicted atmospheric impact position, has observed a short flash just before the expected impact time 0246 UTC. Because of the distance it was not a very large phenomenon, but still a confirmation that some bright meteor has been seen in the predicted direction.”

The best case scenario I can imagine for getting us to develop the tools needed for asteroid deflection is having the occasional small event like this making news around the globe. And indeed, we should have no shortage of events to point to, according to Don Yeomans, who toils at the Near-Earth Object Office at the Jet Propulsion Laboratory:

“We estimate objects this size enter Earth’s atmosphere once every few months. The unique aspect of this event is that it is the first time we have observed an impacting object during its final approach.”

Even so, we had little lead time, with the object being discovered only a day before its encounter with Earth. And if we found a much larger object on an equivalent course? We know that Tunguska-class events may occur as frequently as every 100 years, a grim reminder that space debris is wildly variable in size and can create catastrophe where it falls. Let’s hope it doesn’t take another Tunguska to awaken the public to the need for robust space-faring technologies that can nudge incoming asteroids into safer trajectories.

Emily Lakdawalla did an outstanding job on this story for the Planetary Society weblog. Let me quote from her thoughts on public reaction to a larger object:

But of course we now have to ask ourselves: what would have happened if the object was much bigger than 2 meters in diameter? Reassuringly, the first thing that would have happened is that the detection most likely would have happened much earlier. The bigger and more hazardous an object is, the brighter it is, and the sooner we will detect it. We will likely have way more than 20 hours’ warning of an incoming dangerous object. Still, though, the warning time for a tens-of-meter-diameter object could only be measured in days. If we’d had three days’ warning of a dangerous impactor heading for Sudan, what could the world have done? The remote location of the impact would have been fortunate for humanity in general, but disastrous for the few people who lived out in that remoteness. Could the developed world have done anything to prevent yet another humanitarian disaster from befalling the Sudanese?

These are highly theoretical questions at the moment, but they could become far more pointed at any time. All the more reason to be thinking, as the Association of Space Explorers continues to do, about the possibilities of crafting an international response. That one is dependent upon politics more than technology, and an equally tough challenge. For more on the public response to small impacts, see Morrison, D. “The Impact Hazard: Advanced NEO Surveys and Societal responses,” In Comet/Asteroid Impacts and Human Society (P. Bobrowsky & H. Rickman, eds.) Springer, New York (2007).

Then you look a little more closely at the new find. For one thing, the COROT mission depends not upon radial velocity measurements but planetary transits. More significantly, COROT-exo-3b is roughly the size of Jupiter but is fully twenty times as massive. Orbiting an F-class dwarf with metallicity values much like the Sun, the object opens up a new perspective, for we’ve found planets twelve times as massive as Jupiter and stars seventy times as massive, but nothing in the range in between. A brown dwarf or a planet? We’re in the so-called ‘brown dwarf desert’ between star and planet with this one.

Image: Relative sizes of the Sun, COROT-exo-3b and Jupiter, an artist’s impression. Credit: OAMP.

Says Francois Bouchy (Institut d’Astrophysique de Paris), a member of the discovery team:

“COROT-exo-3b might turn out to be a rare object found by sheer luck. But it might just be a member of a new-found family of very massive planets that encircle stars more massive than our Sun. We’re now beginning to think that the more massive the star, the more massive the planet.”

This discovery reminds us that we’re still trying to draw the line between planets and brown dwarfs, the latter being ‘almost’ stars that cannot sustain fusion at the core. Considered as a planet, COROT-exo-3b is the most massive and the densest yet found, and it raises questions about massive planetary formation in an environment this close to a star. Surely migration from further out in the system is at work here, but we have much study ahead before we can draw confident conclusions.

The paper on this work sums up the situation nicely:

CoRoT-Exo-3b reopens the debate about the existence of a hitherto non-detected brown-dwarf population at short orbital periods but also about the definition of a planet, such as the common one which, in this range of mass, relies on the deuterium burning limit. The exact nature of this new object is therefore still doubtful. Its parameters are in pretty good agreement with the model predictions for brown-dwarfs and if that is that case, it might simply be the first secure and well-characterized object at the lowest mass end of the stellar population. If CoRoT-Exo-3b is indeed a brown-dwarf one should review as well the other massive planets like XO-3b, HAT-P2b and WASP-14b as potential members of this class. An alternative explanation is that CoRoT-Exo-3b belongs to a new, yet unexplored, very massive planet population, widening the variety of exoplanets. The currently ambiguous nature of CoRoT-Exo-3b makes it therefore a very worthwhile object for further deeper studies.

We can expect future COROT finds to aid these investigations. Indeed, the mission seems made to order for planets in short orbital periods. With the capability of monitoring up to 12,000 stars simultaneously in each observing run, covering a span of 150 days of nearly continuous observations, the instrument is obviously sensitive to such worlds, whose study can then be followed up with radial velocity techniques.

The paper is Deleuil et al., “Transiting exoplanets from the CoRoT space mission VI. CoRoT-Exo-3b: The first secure inhabitant of the brown-dwarf desert,” accepted for publication in Astronomy & Astrophysics (abstract).

Image: Looking for dimmed starlight — the basic method at work in the TAOS survey. The experiment follows 3000 stars five times per second in its search. Credit: TAOS.

TAOS works with small, wide-field robotic telescopes on peaks near the Yu-Shan (Jade Mountain) National Park in Taiwan. The current results represent 200 hours of collected data using these instruments. And thus far TAOS has come up blank — no occultations. Perhaps the outer Solar System is not as packed with material as we had believed, an indication that smaller bodies have already merged to form the larger objects like Pluto/Charon, Eris, Haumea and their numerous cousins. Collisions may have ground smaller KBOs to a size we cannot observe, even with the equipment involved in the TAOS survey, a potential insight into the history of planetary formation in our Solar System.

The paper on this work explains the mechanisms involved in the Kuiper Belt:

The size distribution of Kuiper Belt Objects (KBOs) is believed to reflect a history of agglomeration during the planetary formation epoch, when relative velocities between particles were low and collisions typically resulted in particles sticking together, followed by destructive collisions when the relative velocities were increased by dynamical processes after the giant planets formed… The slope of the distribution function for larger objects reflects the early phase of agglomeration, while the shallower distribution for smaller objects reflects a subsequent phase of destructive collisions. The location of the break moves to larger sizes with time, while the distribution for smaller objects is expected to evolve towards a steady state collisional cascade…

Given that some theories suggest a crowded Kuiper Belt, getting firm parameters on its density will be helpful. What we have thus far is that the upper size range of Kuiper Belt objects is well represented, with more than sixty bodies with a radius of over 100 kilometers having been detected. And with the help of TAOS, we now have the strongest data yet on the paucity of smaller KBOs in the range the survey is equipped to study. The work at TAOS continues, with a fourth telescope scheduled for deployment in the near future.

The paper is Zhang et al., “First Results From The Taiwanese-American Occultation Survey (TAOS),” Astrophysical Journal 685 (2008), p. L157 (abstract).

One More Thing: If you’re hoping to keep abreast of the latest Kuiper Belt news, do be aware of the Kuiper Belt Newsletter. Its stated goal: “…to provide researchers with easy and rapid access to current observational and theoretical studies of the Kuiper Belt, directly related objects (e.g., Pluto, Centaurs), and other areas of research that are explicitly applied to the Kuiper Belt.”

As you would imagine, controversy follows such thoughts, and the follow-on that we are probably a rather typical civilization with only a tiny window for getting into space that should be exploited as soon as possible. Most species go extinct — will we be any different in the face of pandemic, nuclear war or incoming asteroid? The latest Carnival of Space is now up at Alice’s Astro Info, including Wayne Hall’s description of Dr. Gott’s talk on these matters at the IdeaFestival in Louisville at the end of September. From which this:

Contrary to most science fiction, we’re likely to be one of the bigger and more successful civilizations in the universe. But if we are not alone, he says that other intelligent species may still be on their home planets or have become extinct through a random event, because they quit the effort to colonize space.

If our survival is important - we after all spend billions on defense in the United States - then getting to space permanently should be considered a defense strategy.

It would take some doing to get everyone as fired up about the space imperative as Story Musgrave, an astronaut and friend of Gott, who says he would have volunteered at any time for a one-way ticket to Mars or the Moon. But there are many who are deeply committed to a permanent human future in space, whether or not they ever go themselves. They are people whose vision may shake loose the research funding and engineering to make a successful off-world colony a reality one day. I always speak in these pages about incremental strategies for moving forward to new technologies, but reading Dr. Gott occasionally reminds me that not everyone is so sanguine about the amount of time available to us. I’ve quoted him before on this but it’s still germane: “…one of the things we should understand about time is that we have just a little.”

Adaptive optics involves real-time corrections made at high speed, feeding a computer-controlled deformable mirror that interprets the atmospheric distortion by examining light from the chosen guide stars. Normally, the method works with a single guide star, but that allows for atmospheric corrections only in a tiny region of sky. The new MAD methods significantly overcome this limitation. The false-color infrared Jupiter we see here is proof of the result, not only startlingly crisp but scientifically useful in the identification of an apparent shift to the south in the planet’s equatorial haze, a change that shows up clearly when this image is compared to Hubble images from 2005.

Image (click to enlarge): Jupiter in infrared light, taken on the night of 17 August 2008 with the Multi-Conjugate Adaptive Optics Demonstrator (MAD) prototype instrument mounted on ESO’s Very Large Telescope. This false colour photo is the combination of a series of images taken over a time span of about 20 minutes, through three different filters (2, 2.14, and 2.16 microns). The image sharpening obtained is about 90 milli-arcseconds across the whole planetary disc, a real record over similar images taken from the ground. This corresponds to seeing details about 300 km wide on the surface of the giant planet.

As adaptive optics continues to sharpen our view from the ground, the way we play with light gets more ingenious all the time. Scientists studying the Cassiopeia A supernova remnant are now working with ‘light echoes’ — hot spots in silicate dust near the remnant that are the result of a short pulse of ultraviolet radiation and X-rays that occurred with the supernova. Essentially, we’re looking at an explosion whose light reached the Earth in the 17th Century, but we’re now able to use the expanding gas cloud to examine energy that is being re-radiated from the blast at infrared wavelengths. See this news release for more.

The image below identifies the location of the light echoes. As to the nature of light echoes themselves, here’s how Eli Dwek (NASA GSFC) and Richard Arendt (University of Maryland), who used Spitzer data in this work, define the phenomenon in their paper:

Short-lived luminous sources can produce echoes of their outburst in the ISM. These echoes can be manifested as line emission from the gas, or reflected and thermally re-radiated light from the dust in the ISM. They can be used to probe the morphology of the interstellar medium (ISM) through which they are expanding and to reconstruct the historical record of the temporal behavior of the light source.

Image: The Cassiopeia A supernova’s first flash of radiation makes six clumps of dust (circled) unusually hot. Credit: NASA/JPL-Caltech/E. Dwek and R. Arendt.

Out of this work comes an analysis of the burst that produced the echoes and an examination of the interstellar clouds that gave rise to them. The triggering event was the pulse of UV and X-rays of the original shock wave triggered by the formation of a neutron star, a blast that blew the star’s outer layers apart and preceded the flash in visible light. We have evidence that such ’shock breakout’ occurs in a long pulse that the Swift satellite detected in 2008 from galaxy NGC 2770. That pulse was followed by the appearance of a supernova in that galaxy a few days later.

The paper on this work is Dwek and Arendt, “Infrared Echoes Reveal the Shock Breakout of the Cas A Supernova,” Astrophysical Journal 685 (October 1, 2008), pp. 976–987 (abstract). Like the adaptive optics refinements we looked at above, this work reminds us of the way science continues to transcend apparent limitations. Atmospheric distortion is rapidly being overcome. And in a sense, astronomers are learning to overcome the limitations of time by finding light echoes that carry at least part of a cataclysmic supernova’s history.

And what of the stars? Solar sail specialist Greg Matloff has been juggling the numbers on interstellar travel via solar sail for decades now, and even with the best case scenario involving an extremely close solar pass, a thousand years to Centauri is about as good as it gets. And that’s quite a stretch in itself. Epsilon Eridani would actually make an easier mission as it’s much closer to the ecliptic, so you get 30 kilometers per second (Earth’s orbital velocity around the Sun) from scratch as you begin your solar approach. On the other hand, the resultant velocity (200 AU per year in one mission concept) takes 3500 years to reach Epsilon Eridani.

Laser propulsion is one way around the solar sail limitation, and as Matloff, along with co-authors Les Johnson and Giovanni Vulpetti, discuss in their new solar sail book, the method must be finely tuned for success. Earth-based lasers won’t do because of attenuation from Earth’s atmosphere, diminishing the beam’s intensity, and also causing it to diverge much more quickly. The result: Deeply compromised thrust on the sail. Earth’s rotation is also a major problem, making it impossible to keep the beam on the receding sail for extended periods.

Robert Forward pondered power stations in the inner Solar System to solve this problem, with the laser beam focused by a huge lens in the outer system for maximum effect. It’s interesting to see how that idea — created for its interstellar possibilities — has developed over the years. What Matloff, Johnson and Vulpetti talk about is a space-based laser in orbit around Jupiter. The orbital rotation problem is greatly eased because Jupiter orbits only once in twelve years, allowing ample time for beam adjustment and calibration. Not only that, but use a polar orbit and you can keep the sail under beam for a decade at a time.

And here’s where things get truly ingenious. Powering up that big laser could be handled by a tether, an idea dear to Robert Forward’s heart (he built an entire company, called Tethers Unlimited, around the concept). A long conducting wire deployed deep into Jupiter’s magnetosphere would generate a huge electrical flow. As the authors note, this is the same principle that is at work when an electrical generator produces electricity in a power plant. Wires moving through intense magnetic fields produce electricity, and Jupiter’s magnetic field is the second most powerful in the Solar System, second only to that of the Sun.

Forward envisioned the use of tethers in a much different way. Properly positioned, they could adjust spacecraft orbits and fling payloads around the Solar System without the need for rockets. But he would have loved the idea of using tethers for power generation around Jupiter, meeting the laser’s formidable needs. That would enable a beamed propulsion scenario capable of getting us into nearby interstellar space and shortening those lengthy travel times to Centauri and elsewhere.

From the book:

This is by no means the only scenario in which lasers might be used to push our sails. But it is certainly a likely one. A mission might proceed something like this: A sailcraft departs from Earth on a sunward bound trajectory. The craft falls toward the Sun and orients its sail to maximize solar thrust at perihelion, giving it an incredible boost toward the outer solar system. Sunlight continues to push on the sail until it reaches the orbit of Jupiter, at which point our tether-driven laser sends a beam of light to reflect from the sail, picking up from where the now-feeble sunlight leaves off. The laser maintains its aim point on the sail, providing continuous additional thrust, until the diffraction limit of the laser results in no net thrust being applied to the sail — somewhere in deep space…

There are, of course, alternatives to lasers when it comes to beamed propulsion. We’ll be talking soon with James Benford, the leading specialist on microwave beaming (I hope to have that interview up within the next couple of weeks), and particle beaming options using futuristic versions of a nuclear accelerator are also well worth considering. The point here is the flexibility of the sail itself. It’s a spacecraft concept that offers abundant applications right here in the Solar System, while holding out the promise of future adaptations that may well propel our first targeted star mission to its destination.

The euphoria comes from Hubble’s sharp vision. The Local Volume encompasses galaxies beyond the Local Group, with distances in the survey ranging from 6.5 million light years to 13 million light years from Earth. That’s actually close enough that the right tools for seeing — Hubble’s Advanced Camera for Surveys and Wide Field Planetary Camera 2 — can pull individual stars out of what had been an indistinct galactic background. Out of that we stand to learn something about star formation in different types of galaxies.

The study ranges from galaxies in which star formation is active and ongoing to those made up entirely of ancient stars. Julianne Dalcanton (University of Washington), leader of the ANGST survey, sums up what the findings point to:

“When we look back in time at distant, young galaxies, we see lots of vigorous star formation. However, we can only guess as to what those galaxies might eventually turn into. Using the galaxies in the nearby universe as a ‘fossil record,’ we can compare them with young galaxies far away. This comparison gives us a history of star formation and provides a better understanding of the masses, structures, and environments of the galaxies.”

The image below suggests the level of detail involved. It’s a composite of three close-up views of NGC 300, a member of the Sculptor Group of galaxies.

Image: At far left, Hubble resolves a dense swarm of stars, patches of dust, and a bright central star cluster. This cluster lies at the very nucleus of the galaxy. Similar clusters are thought to be related to the formation of supermassive black holes. The image at center shows a star-forming region a few thousand light-years farther from the galaxy’s center. The yellow blobs are the glow from hot gas that has been heated by radiation from the nearest young, blue stars. The image at far right reveals more diffuse groupings of young, blue stars, farther away from the galaxy’s center, along with faint shells of hot gas. Credit: NASA, ESA, and J. Dalcanton and B. Williams (University of Washington).

Interesting in terms of astrobiology is the work on M81 that draws on data from this survey. Here I’m quoting from a Hubble news release (the relevant paper isn’t yet online), but Benjamin Williams (University of Washington) notes that stars in the outer disk of massive spiral galaxies like this one formed in the early universe. In M81’s case, we’re talking about periods of heavy star formation occurring seven billion years ago — half the current age of the cosmos. What’s intriguing here is the rapid enrichment of heavy elements via supernova explosions. Says Williams: “We were surprised by how quickly the elements formed and how the subsequent star-formation rate for the bulk of the stars in M81 changed after that.”

Image: The spiral galaxy M81. If stars in its outer disk formed seven billion years ago and the galaxy was rapidly filled with heavy elements via supernovae, could civilizations have emerged a billion or more years before our Sun even formed? Credit: Jonathan Irwin/DSS2.

There’s our old friend Fermi again, teasing us with the possibility of civilizations far more ancient than our own. The paper is Williams et al., “The ACS Nearby Galaxy Survey Treasury I. The Star Formation History of the M81 Outer Disk,” submitted to the Astronomical Journal.