by Paul Gilster | Nov 22, 2010 | Sail Concepts |
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 observations operating without the now exhausted coolant needed to chill its longest wavelength detectors. WISE is covering the gamut, from asteroids to stars and galaxies, but now focuses largely on comets and asteroids, and those include the near-Earth objects whose orbit takes them near our planet.
The latest WISE treat is a vivid look at the planetary nebula NGC 1514, the ‘Crystal Ball’ nebula discovered in 1790 by William Herschel. Have a look at these images, one from an Earth-side telescope, the other the view from WISE, and ponder how useful it is to have the WISE detectors operational in space. We’re looking at a pair of stars, one a dying giant larger than the Sun, the other a white dwarf originally formed from an even larger star. The aging of the giant star involves its losing outer layers of material to form a ‘bubble’ around both stars.
Image: This image composite shows two views of a puffy, dying star, or planetary nebula, known as NGC 1514. The view on the left is from a ground-based, visible-light telescope; the view on the right shows the object in infrared light, as seen by NASA’s Wide-field Infrared Survey Explorer, or WISE. Credit: NASA/JPL-Caltech/UCLA/Digitized Sky Survey/STScI.
The vivid imagery is the result of jets of material from the white dwarf colliding with the bubble wall drawn out of the giant, creating the orange rings as dust is heated and glows with infrared light. The green cloud is an inner shell of shed material that, in the visible image, appears in bright blues (and note an outer shell in the visible light image that does not appear in the infrared). As to color coding in the WISE image, infrared light with a wavelength of 3.4 microns is blue; 4.6-micron light is cyan; 12-micron light is green; and 22-micron light is red.
WISE science team member Michael Ressler puts it best: “This object has been studied for more than 200 years, but WISE shows us it still has surprises.” That’s the benefit of having infrared eyes that can tease out structure that would otherwise be obscured by brightly fluorescing clouds of gas. We can only assume WISE will be delivering up more surprises, and plenty of them given the sheer amount of WISE data that have been accumulating these past months. The first data release to the astronomical community is in the spring of 2011.
Snow Showers Around Hartley 2
Nor are we through with the EPOXI mission, which we now learn imaged clouds of large ice particles — from golf ball-size to the size of a basketball — coming off the comet. Says Michael A’Hearn, principal investigator for the Deep Impact and EPOXI missions:
“When we visited Hartley 2, it was in the midst of a cometary ice storm generated by jets of carbon dioxide gas carrying a couple of tons of water ice off the comet every second. At the same time, a different process was causing water vapor to come out of the comet’s mid-section.
“This is the first time we’ve ever seen individual chunks of ice in the cloud around a comet or jets definitively powered by carbon dioxide gas. We looked for, but didn’t see such ice particles around Tempel 1.”
Image: This zoomed in image from the High Resolution Instrument shows particles swirling in a “snow storm” around the nucleus of comet Hartley 2. From these images we can estimate the size of the particles and we use a combination of other data to determine that these are icy particles rather than dust. Although the largest particles are golfball to basketball sized, they are very porous and fluffy. Credit: NASA/JPL-Caltech/UMD
Mission co-investigator Pete Schultz (Brown University) likens the cloud of particles to what you would see in a crystal snow globe and adds “When we first saw all the specks surrounding the nucleus, our mouths dropped.” The findings show that at least part of Hartley 2 operates differently from other comets whose nuclei have been imaged by spacecraft, with CO2 being the key. The rough areas of Hartley 2 see jets of CO2 blasting out water ice from below to produce clouds of ice and ‘snow,’ whereas the smooth middle area of the comet is more like the surface of Tempel 1, with water evaporating below the surface and percolating out through the dust.
So the smooth and rough areas of the comet appear to respond differently to heating from the Sun and have different mechanisms to get water out of the cometary interior. We get blasts of particles in one area and water vapor close to the smoother cometary surfaces. How all this occurs, and whether it’s the result of dry-ice inhomogeneities dating back to the comet’s formation or due to subsequent changes, will be the subject of further study. But what an accomplishment for a spacecraft that, target after target, continues to yield up new insights into ancient objects.
by Paul Gilster | Nov 19, 2010 | Tau Zero Foundation |
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 with several Tau Zero practitioners to discuss various points of view on how best to make progress. Also, the Tau Zero public website has been transferred to other service providers for necessary updates to that information.
Operations and Priorities
One observation is that there are apparently misconceptions about our priorities and how we operate. In retrospect that is understandable since we have been operating, so far, on an opportunistic basis – relying on the self-initiated work of our Practitioners. Examples include; Project Icarus, FOCAL mission studies, the Living (Statistical) Drake Equation, Frontiers of Propulsion Science, publications from other practitioners, Faces From Earth, and the long-running Centauri Dreams news forum.
The time has now come to be more deliberate as we move forward. Ideally, we want to cover all the technologies and implications related to the ultimate goal of reaching other habitable worlds, and we want to do that in a manner where you can count on the accuracy of our information (which is why we include reference citations so that you can check any questionable assertions). This span includes understanding ‘what’s out there,’ examining all the options for ‘how to get there,’ and being sure to tie this all to its ‘relevance to humanity.’
One of the most hotly debated items is how best to get out there. To be explicit, Tau Zero covers the full span of options, from the seemingly simple solar sails to the seemingly impossible faster-than-light travel. For each option within that span, there are different levels of readiness and performance, and accordingly different types of work. One consistent finding – which is nonetheless contentious amongst our readership – is that there is no single “best” choice of propulsion. We have also found that individuals tend to have a favorite within that span, but our interests cover the full span. So, rather than prematurely arguing over which engine is best, we intend to give you reliable, traceable information about the status and next-steps for all those options.
So far we’ve been providing this service mostly through Paul Gilster’s Centauri Dreams news forum, and by corralling a suite of practitioners who can keep us up to date. Many of these practitioners have voluntarily begun projects to make progress on specific topics. As we move forward, we will have to solicit additional funding to better cover these possibilities. We are also considering options on how our readership – you – can influence which options get more attention.
Ongoing Projects
With that said and with the changes to come, here now is a short reflection on our progress to date. Considering that this resulted from volunteer work with only modest financial contributions (for conference travel and operating expenses), this bodes well for our future productivity.
- PROJECT ICARUS
Led by Kelvin Long and Richard Obousy, Project Icarus is a sequel to the renowned 1978 Project Daedalus study of the British Interplanetary Society for a fusion-based interstellar probe. This is a joint collaboration with the British Interplanetary Society. The first year of the 5-year study has commenced right on schedule and several papers were presented at the 2010 International Astronautical Congress in Prague to spread the news and get valuable feedback from the astronautical community. As this study progresses it will deliver realistic estimates for what such technology could accomplish along with estimates of what other milestones would be needed to make it happen. Examples of those intermediate steps include the business case for mining Helium-3 from the atmosphere of Uranus, and the communication network for deep space exploration. By reaching beyond near-term horizons, such work sets the stage for the next wave of advancements to follow.
- INTERSTELLAR PRECURSOR MISSION STUDIES
Rather than wait until interstellar probes are fully viable, much can be learned by traveling to intermediate destinations offering challenges much closer to home. This includes studying the FOCAL mission to confirm the physics and use of the gravitational lensing of our own Sun beyond 550 AU. The champion of this idea, Claudio Maccone, recently published a book called Deep Space Flight and Communications about such ambitions and also presented his progress at the 2010 International Astronautical Congress.
- FRONTIERS OF PROPULSION SCIENCE
Marc Millis and Eric Davis compiled and edited the assessments from 18 different lead authors to produce the first-ever scholarly book about non-propellant space drives, gravity control, and faster than light physics. Published as a technical volume within the American Institute of Aeronautics and Astronautics, Frontiers of Propulsion Science is a 739 page reference that describes past approaches, critical issues, and identifies next-step research approaches. This work was also presented at the 2010 International Astronautical Congress.
- STATISTICAL DRAKE EQUATION
Claudio Maccone has taken the Drake Equation and advanced it to a statistical format so that the implications of its uncertainties can be understood. He recently extended this method to the Fermi Paradox, and then to estimates of the distance to the nearest potentially habitable planets (88+/- 39 light years). Papers on all of these have been presented and this work will continue to be refined.
- FACES FROM EARTH
Faces from Earth provides information and organizes events to educate the public about space and astronomy and to promote deep space missions, aiming to compile messages to put on board future spacecraft. The organizers hope to offer an exciting educational opportunity for students of every age: Project One Kg Message is about designing and building a time capsule of roughly 1 kg content, which could possibly fly on board a future deep space mission; the E.T. are You out there? campaigns are designed to introduce the notions of possible extraterrestial life and METI to secondary school students; Mosaic Earth builds Earth images like the famous Blue Marble, as a mosaic composition – from portraits of people participating in the project, in the belief that sending a message to E.T. is a deeply human endeavour.
Practitioner Publications
Here is a just a partial list of recent books from Tau Zero Practitioners, with more in progress:
Matloff, Johnson, and Bangs (2007) Living Off the Land in Space: Green Roads to the Cosmos. New York: John Wiley & Sons.
Vulpetti, Johnson, and Matloff (2008) Solar Sails: A Novel Approach to Interplanetary Travel. Springer.
Millis & Davis (eds.) (2009) Frontiers of Propulsion Science. Vol. 227 of Progress in Astronautics and Aeronautics. American Institute of Aeronautics and Astronautics (AIAA).
Maccone (2009) Deep Space Flight and Communications: Exploiting the Sun as a Gravitational Lens. Springer Praxis.
Johnson, Matloff, and Bangs (2009) Paradise Regained: The Regreening of Earth. Springer.
In closing, I am pleased to share this progress with you and look forward to being able to escalate these efforts. If you want to see more progress, please consider donating:
Donate to Tau Zero, where all these activities are covered.
Donate directly to Project Icarus, if you are a fan of that work.
Donate directly to Faces from Earth.
by Paul Gilster | Nov 18, 2010 | Exoplanetary Science |
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 way to the remote future and looks out upon a desolate world populated by huge, crab-like creatures. On the beach he has the view of the swollen Sun, bloated and entering what we would now call its red giant phase. Wells writes:
I moved on a hundred years, and there was the same red sun–a little larger, a little duller–the same dying sea, the same chill air, and the same crowd of earthy crustacea creeping in and out among the green weed and the red rocks. And in the westward sky, I saw a curved pale line like a vast new moon.
‘So I travelled, stopping ever and again, in great strides of a thousand years or more, drawn on by the mystery of the earth’s fate, watching with a strange fascination the sun grow larger and duller in the westward sky, and the life of the old earth ebb away. At last, more than thirty million years hence, the huge red-hot dome of the sun had come to obscure nearly a tenth part of the darkling heavens.
The imagery was powerful in late Victorian England and it’s still powerful today. The dread of ‘that remote and awful twilight’ overcomes the time traveler, who makes his way back to his own time for a last encounter with his friends before disappearing forever. Maybe because of an early reading of Wells’ novel, I’ve always been fascinated with stars at the end of their lifetimes, stars that, like our Sun, will exhaust their hydrogen fuel and grow into red giants, engulfing their inner planets and possibly offering an opportunity for life on outer worlds and moons.
Image: I think that’s a Richard Powers cover on this old Berkley paperback (check out the handling of the time machine itself, surely a Powers signature). In any event, it gets across the beach scene in the novel, with the suggestion of a crab-like creature at right and, in the sky, a swollen, dying Sun.
Dying Stars, Migrating Planets
Enter HIP 13044 b, a newly discovered planet around a most interesting star. This is a gas giant with a minimum mass 1.25 times that of Jupiter, and it’s intriguing because it has survived the period of massive stellar expansion. HIP 13044, its host star, has contracted once again and is now burning helium in its core, a ‘horizontal branch star’ of the kind that planet hunters have generally had little to do with. But the European team using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has its eye on dying stars and the planets that have survived their death throes, says Johny Setiawan (Max-Planck-Institut für Astronomie):
“This discovery is part of a study where we are systematically searching for exoplanets that orbit stars nearing the end of their lives. This discovery is particularly intriguing when we consider the distant future of our own planetary system, as the Sun is also expected to become a red giant in about five billion years.”
And just what happens to a planet in a situation like this? We have much to learn, but we do know that HIP 13044 b is, at its closest point in an elliptical orbit, less than a single stellar diameter from the surface of the star, about 0.055 AU, completing an orbit every 16.2 days. The researchers believe the planet’s orbit might once have been larger, but contracted during the red giant phase that would have swallowed the star’s inner planets, assuming they existed.
But at least some evidence points to their existence. HIP 13044’s fast rotation, higher than the norm for a horizontal branch star, can be explained by assuming that the star swallowed its inner planets during the red giant phase, which would have caused its spin to increase.
An Extragalactic Wanderer
The same fate probably awaits HIP 13044 b, for its host star will begin to expand once again in what could be a glimpse of the future for planets like our own Jupiter. But HIP 13044 b intrigues us on other grounds as well. Its primary contains few metals, elements above hydrogen and helium, causing Setiawan to add, “It is a puzzle for the widely accepted model of planet formation to explain how such a star, which contains hardly any heavy elements at all, could have formed a planet. Planets around stars like this must probably form in a different way.”
Moreover, the new planet orbits a star that is not native to the Milky Way at all, but a part of the Helmi stream, a collection of stars born in a dwarf galaxy and captured by the Milky Way between six and nine billion years ago. So we have a planet that is, despite its long tenure in our own galaxy, an extragalactic world, one found through radial velocity studies using the FEROS spectrograph. HIP 13044 b is about 2000 light years from Earth in the constellation Fornax.
We’ve had tentative detections of planets in other galaxies through gravitational microlensing, but no extragalactic planet has yet been confirmed, so HIP 13044 b is the next best thing, a galactic wanderer that found its way to the Milky Way before our own system had even formed. What for H.G. Wells was a scene of the remotest futurity may have played itself out in the unthinkably remote past for any beings that may have existed in the HIP 13044 system. In any case, it’s a system that has much to tell us about planetary fates around red giant stars.
The paper is Setiawan et al., “A Giant Planet Around a Metal-poor Star of Extragalactic Origin,” Science Express 18 November 2010 (abstract).
by Paul Gilster | Nov 17, 2010 | Sail Concepts |
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 LightSail story before on Centauri Dreams, but do read the Planetary Society’s backgrounder on the mission.
Meanwhile, sneaking up on us almost surrepetitiously, comes the news that NASA is in the final stages for the launch of NanoSail-D, designed to be the first NASA sail deployed in low-Earth orbit. One goal of the NanoSail-D project is to demonstrate the ability to pack and deploy a large sail from a highly compacted volume. The Japanese IKAROS sail has proven the sail concept, but much work lies ahead in optimizing deployment strategies not only for sails but future thin film sensor or solar arrays.
Image: NanoSail-D deployment: Fully deployed, the sail area measures 107 square feet. It is comprised of four, triangular membranes supported by thin metal tape booms. Full deployment takes just 5 seconds. Credit: NASA/MSFC/D. Higginbotham
Dean Alhorn, principal investigator for the mission at MSFC, says the sail, made of a polymer called CP1 that is no thicker than single-ply tissue paper, will be wrapped around a spindle before being packed into a container smaller than a loaf of bread. Deployment will involve four booms that should unfurl the sail within five seconds. Adds Alhorn:
“The deployment works in the exact opposite way of carpenter’s measuring tape. With a measuring tape, you pull it out, which winds up a spring, and when you let it go it is quickly pulled back in. With NanoSail-D, we wind up the booms around the center spindle. Those wound-up booms act like the spring. Approximately seven days after launch, it deploys the sail off the center spindle.”
You’ll recall the earlier NanoSail-D, which perished in a launch attempt back in 2008 and led to a call in these pages for the spare to be launched on a future flight. This is that backup, one that has been tweaked and refined for this mission and committed to a 17-week flight in a circular orbit 650 kilometers above the Earth (although the actual flight time may range from 70 to 120 days). In addition to what we’ll learn about sail deployment, the de-orbiting of NanoSail-D as the result of atmospheric drag will offer information about future methods for returning old satellites to Earth. And down the road, NanoSail-D points to a next generation design called FeatherSail.
Note this about NanoSail-D: Even at 650 kilometers out, drag effects may overpower the propulsive power of solar photons, so the deployment operation is clearly the prime motivator for the mission, as well as the de-orbiting studies. Nonetheless, if we get a successful deployment, it will point the way to future, higher-altitude missions, and serve as another demonstration of the fact that solar sailing technology is rapidly maturing, even as we await the launch of the first of the Planetary Society’s LightSails.
Launch is now scheduled for November 19 from Kodiak Island (Alaska) aboard a Minotaur 4 rocket (and thanks to Roman Kezerashvili for the reminder). The spacecraft will be part of the payload aboard the Fast, Affordable Science and Technology Satellite (FASTSAT). Among the several sites to keep an eye on, NASA’s Small Satellite Missions page should have updates and a Twitter feed is available @NanoSailD. The NanoSailD mission dashboard is scheduled to go operational once the satellite launches and SpaceFlight Now will be offering live video of the launch.
by Paul Gilster | Nov 16, 2010 | Deep Sky Astronomy & Telescopes |
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 unseen stars and the yellow, point-like clusters of stars that make up this galaxy. Lying at the center of M87, the monstrous black hole has swallowed up matter equal to 2 billion times our Sun’s mass. M87 is 50 million light-years from Earth. Credit: NASA and The Hubble Heritage Team (STScI/AURA).
The Milky Way’s massive black hole seems quiescent today, but there remains the possibility that it produced a jet in the past, a notion piqued by the recent discovery of a previously unseen structure spanning some 50,000 light years. It took intensive processing of data from the Large Area Telescope (LAT), the highest-resolution gamma-ray detector ever launched, to make the find. The LAT is the main instrument of the Fermi Gamma-Ray Space Telescope, formerly known as GLAST (for Gamma-ray Large Area Space Telescope). Doug Finkbeiner (Harvard-Smithsonian Center for Astrophysics) lays out the find in stark terms:
“What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center. We don’t fully understand their nature or origin.”
Earlier data from the Wilkinson Microwave Anisotropy Probe and the Roentgen Satellite have suggested evidence for part of the structures, now called ‘Fermi bubbles,’ near the galactic center, but the Fermi LAT results go further in suggesting the extent and surprisingly well-defined nature of the bubbles. Perhaps these are survivors of ancient jet activity, but relating the structures to jets brings its own set of problems, as the paper on this work notes:
…the north-south symmetry of the bubbles has no obvious explanation in the context of an AGN jet: there is no reason for one jet to be oriented perpendicular to the Galactic plane. The large width and rounded shape of the bubbles are also not typical of jets, which are generally much more collimated, although a precessing jet might help explain the wide opening angle of the bubbles. If the central MBH becomes active on a relatively short timescale, the Fermi bubbles may be created by a number of past jets, which combine to give rise to the symmetric and uniform Fermi bubbles.
And if past jets are not the cause, one alternative is a burst of rapid star formation, which can likewise drive a huge outflow of gas. Whatever the case, the structures may be millions of years old and they span half the visible sky. Yet they have remained undetected because particles moving near the speed of light interact with interstellar gas in the Milky Way, creating a fog of gamma rays (the ‘diffuse emission’) that has until now obscured the bubbles.
Image: The bubbles display a spectrum with higher peak energies than the diffuse gamma-ray glow seen throughout the sky. In addition, the bubbles display sharp edges in Fermi LAT data. Both of these qualities suggest that the structure arose in a sudden, impulsive event, such as an eruption from the Milky Way’s black hole or a rapid surge of star formation in the galactic center. Credit: NASA/DOE/Fermi LAT/D. Finkbeiner et al.
Centauri Dreams reader Antonio Tavani passed along links to the Italian coverage of the Fermi bubbles, and wondered whether this large, previously undetected structure might have implications for the Fermi paradox, the ‘where are they’ question that puzzles those who believe interstellar travel, even if limited to a fraction of light speed, is all but inevitable. It’s an interesting question. Are we seeing the remnant of high-energy jet activity that could have suppressed early life on worlds too near galactic center? At this point, all we can do is speculate, while noting that the emissions suggest the structure formed as the result of a large and rapid energy release.
The paper is Meng Su et al., “Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?” accepted by The Astrophysical Journal (preprint).
