by Paul Gilster | Nov 19, 2007 | Exoplanetary Science |
Where will we be in the exoplanet hunt by the year 2020? A few of my own guesses would take this form: We should, within even the next year or two, have detected a terrestrial world in a truly unambiguous position within the habitable zone of a star. That star will doubtless be a red dwarf, like Gliese 581, but we can hope for a result that doesn’t lend itself to so many conflicting interpretations. The detection method will surely be planetary transit, but even by 2020 we may not know if life exists there.
It’s also easy to surmise that by 2020 we’ll have a terrestrial-class world located within a stellar system not completely dissimilar to our own; i.e., one involving a star much like the Sun, orbited by a rocky world in the habitable zone. We can hope that by 2020 the tools will have been put in place to do spectroscopic observations of the planetary atmospheres involved in small rocky worlds, though so much depends on budgets and the needed tuning up of exquisitely sensitive technologies.
I have a number of other guesses that could come into play, but I’m already second-guessing myself. And now I’m drawn up short by Drake Deming (NASA GSFC), who reminded the recent conference at the Space Telescope Science Institute that going back thirteen years instead of forward, we would remember that only the pulsar planets were known to us at the time. Planets around pulsars were incredibly exciting back then, and we know now that PSR B1257+12, the first pulsar involved, actually has at least three planets instead of the two first discovered.
But one thing pulsar planets are not and that is likely homes to anything like life as we know it. Alien to the point of absurdity, they basically proved something about the likelihood of planets being found elsewhere, but who would have guessed from them that we would find such things as ‘hot Jupiters’ or triple star systems with planets of their own? No, making guesses in a field expanding this rapidly is a dangerous game, one I’m nonetheless glad that Deming and the other scientists at this meeting were willing to play.
The conference, which ended on November 15, was titled “Astrophysics 2020: Large Space Missions Beyond the Next Decade.” Its goal was to look at the groundwork that will be laid by emerging technologies in that time. Ponder: The Ares V heavy launch vehicle means that some of the barriers to putting massive astronomical observatories into space will disappear. Moreover, we’re getting better at robotics, leading ultimately to construction and servicing jobs in space that would previously have been impossible. All this was fodder for conference discussion.
I couldn’t be at the STScI conference, but I’m listening to Dr. Deming’s presentation right now as he discusses the possibilities emerging in the field of transit observations. The entire conference is now available, thirty presentations and panel discussions online in PowerPoint as well as low and high-bandwidth streaming or downloadable video. Need I point out what an educational opportunity webcasts like this provide? As more and more conferences take STScI’s lead, the ability for those unable to attend to learn from the conference experience will become the kind of resource we only used to dream about.
I thank STScI’s Ian Jordan for passing along the much appreciated link to these webcasts, thus allowing me to confound my family by watching presentations all weekend. Fortunately, my wife is a patient woman…
And so back to Drake Deming, who is explaining in a video window on my desktop that direct detection of planets will be occurring in the not so distant future — direct detection means separating planetary photons from stellar photons, no easy task but increasingly feasible nonetheless. But even before that goal is reached, there’s a great deal we can discover about planetary atmospheres. Dr. Deming is moving on to discuss how transits can be used to identify habitable planets around M dwarfs, so he’s lighting up practically every synapse I have, obsessed as I am with the M dwarf planetary question.
We have already identified 20 known transiting exoplanets and the discovery rate is accelerating — twelve were announced just this year. As Dr. Deming discusses a temperature inversion in the atmosphere of HD 209458b, I’m reminded that even now we are making the kind of observations of planetary atmospheres (and indeed, constructing the crudest of maps based on temperature data from secondary eclipses as the planet passes behind the star) that no one thought we could do just a few years ago. The ‘hot Neptune’ GJ 436b likewise shows how transits can reveal surface temperatures.
You can see why the lowest mass M dwarfs are so attractive as we shoot for still smaller planets: Here the habitable zone lies close to the star, meaning short orbital periods and a higher probability of transits. And the small size of the star means that rocky planets can more easily be detected (Dr. Deming covers this in detail). M dwarfs also outnumber stars like the Sun by ten to one. “The nearest habitable planet to Earth,” Deming is saying as I write, “probably orbits an M dwarf, just because there are so many of them.”
You’ll want to watch Dr. Deming’s presentation to learn about the MEarth Project (Mt. Hopkins, AZ), using eight 16-inch telescopes to survey the 2000 nearest M dwarfs for rocky planets in their habitable zones, looking for planets that will be good candidates for spectroscopic follow-up (not with Spitzer but via the James Webb Space Telescope) to search for atmospheric biomarkers. We could be looking at extremely interesting data from the atmospheres of such planets as early as 2015.
Does that gibe with your own predictions? Those interested in all branches of astronomy and astrophysics will want to work through all these presentations to see what’s ahead as we put the latest hardware to work and continue to refine our techniques. Well done to the conference presenters for making this treasure trove available!
by Paul Gilster | Nov 17, 2007 | Exoplanetary Science |
I’ve always enjoyed Lynette Cook’s work. As you can see in the image below, this space artist captures the drama of celestial events by drawing on recent findings. Like Chesley Bonestell, Cook can take you to an exotic place and leave you staring, but her focus is tighter, homing in on exoplanets as filtered through ongoing work at observatories worldwide. The wonders she’ll have to work with as we find more and more such worlds can only be imagined. The dazzling collision below is her take on what may be happening as rocky planets form around HD 23514.
The star’s designation doesn’t jump out but its location does, the oft-studied Pleiades star cluster. Joseph Rhee (UCLA) and collaborators have been working infrared wavelengths using the Gemini North Telescope (Mauna Kea) and space-based infrared instruments, measuring the hot dust around this 100-million year old star. HD 23514 is Sun-like enough to add to the intrigue of this exercise, and it’s orbited by hundreds of thousands of times more dust than our Sun. Evidence for catastrophic collisions in an evolving planetary system? Perhaps.
Whatever is happening seems to originate in a zone between 1/4 to 2 AU from the star, the region between Mercury and Mars in our own Solar System. Benjamin Zuckerman (UCLA) thinks the sheer amount of hot dust is the result of a fairly recent collision between large rocky bodies, perhaps reminiscent of the ‘Big Whack’ that produced the Moon four billion years ago. Says Zuckerman: “Indeed, the collision that generated the Moon sent a comparable mass of debris into interplanetary orbits as is now observed in HD 23514.”
Image: Artist’s rendering of what the environment around HD 23514 might look like as two Earth-sized bodies collide. Artwork by Lynette Cook for Gemini Observatory.
This isn’t the first time Zuckerman has worked on terrestrial planet formation around Sun-like stars. It was back in 2005 that his team reported on BD+20 307, some 300 light years away in the direction of the constellation Aries. That one sports fully one million times the amount of dust that is orbiting our Sun, a step up even from HD 23514. The conclusion: Most young Sun-like stars are probably building terrestrial-style planets through recurring violent collisions. Indeed, comments Rhee, “This is the first clear evidence for planet formation in the Pleiades, and the results we are presenting strongly suggest that terrestrial planets like those in our solar system are quite common.”
Much younger stars in the 10 million year old range or younger are far more likely to have this much dust around them than stars as old as HD 23514, making it and BD+20 307 useful examples of how planet formation may occur around such ‘adolescent’ stars. The paper is Rhee et al., “Warm dust in the terrestrial planet zone of a sun-like Pleiad: collisions between planetary embryos?” accepted for publication in The Astrophysical Journal and available online. The paper on BD+20 307 is Song et al., “Extreme collisions between planetesimals as the origin of warm dust around a Sun-like star,” Nature 436 (21 July 2005), 363-365 (doi: 10.1038/nature03853). Abstract available.
by Paul Gilster | Nov 16, 2007 | Culture and Society |
Rosetta makes its reappearance at just the right time for me. The spacecraft, making its second Earth swing-by on November 13, will use its gravity assists past Earth and Mars to reach Comet 67P/Churyumov-Gerasimenko in 2014, deploying a lander onto the nucleus and spending two years orbiting the comet. The close approach produced the memorable image below. I thought I was too under the weather today to post anything, but Rosetta’s composite shot of Earth by night offers a short, memorable subject. Look at those city lights!
Image: This is a composite of four images combined to show the illuminated crescent of Earth and the cities of the northern hemisphere. The images were acquired with the OSIRIS Wide Angle Camera during Rosetta’s second Earth swing-by on Nov. 13. This image showing islands of light created by human habitation was taken with the OSIRIS WAC at 19:45 CET, about 2 hours before the closest approach of the spacecraft to Earth. At the time, Rosetta was about 80,000 km above the Indian Ocean where the local time approached midnight (the angle between Sun, Earth and Rosetta was about 160°). The image was taken with a five-second exposure of the WAC with the red filter. This image showing Earth’s illuminated crescent was taken with the WAC at 20:05 CET as Rosetta was about 75,000 km from Earth. The crescent seen is around Antarctica. The image is a color composite combining images obtained at various wavelengths. Credit: ESA ©2005 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA.
Of course, what gets my attention is that this is what a technological civilization — the only one we know exists — looks like by night to an approaching spacecraft. Will we one day have interstellar probes that can make a Rosetta-style pass around a world like this in another solar system? For that matter, will we ever have the kind of spectacular close-up images that could result from advanced sunshade concepts like New Worlds, showing us the lights of alien cities? Let’s hope the answer is yes, and that our technologies will one day find signs of extraterrestrial intelligence. If that doesn’t happen, those city lights Rosetta found on Earth begin to look like a reminder of how fragile sentient life may be.
Addendum: More Rosetta images, including Europe at night, available here.
by Paul Gilster | Nov 15, 2007 | Culture and Society |
About the only thing that went wrong on my Washington DC trip (noted earlier here) was having to fight a persistent head cold and trying to avoid shaking hands with our eminent panelists so as not to contaminate them (I want these guys healthy, and working!). But the fates smiled Wednesday morning when I moderated “The Future of the Vision for Space Exploration,” my voice back from what had been near-laryngitis the evening before, and we had a fascinating discussion in the Rayburn House Office Building on Capitol Hill talking about where space exploration is going and what policy decisions loom large at the moment.
Louis Friedman, executive director of The Planetary Society, presented a look at current projects to explore the Solar System, many of which are somewhat off our radar, including Indian lunar missions like Chandrayaan-1 and the Chinese lunar orbiter Chang’e I (images expected by the end of this month). Japan’s space activities beyond the ongoing Hayabusa asteroid return mission also drew attention recently with the Kaguya spacecraft, orbiting Luna since mid-October. The Japan Aerospace Exploration Agency (JAXA) is sending back high-definition videos that should, as Friedman noted, be in their own way as spectacular as the first Apollo 8 images we saw of a newly risen Earth.
What Steven Squyres wouldn’t do with high-definition equipment on his Mars rovers! Squyres, principal investigator for the science payload on the Mars Exploration Rover Project, showed the kind of unforgettable imagery we’ve almost come to take for granted of the Red Planet’s battered surface. At least, we start to take it for granted until we stop and think the matter through. I can remember, as a graduate student, pacing the floor waiting for that first TV image from Viking to come through (the one where they thought they were looking at a blue sky, but subsequently had to re-program to derive the now familiar salmon-colored atmosphere). So I found myself, as others in the room doubtless did, becoming energized about Mars through Squyres’ images all over again.
I think Steven Squyres is a man who has found the exact niche he wanted in life. He is so enthusiastic about what he does, even irrepressible, that when he speaks of addressing an audience of 20,000 students in Detroit (at Ford Field, where the Lions play), you realize how much good he is doing not just as planetary scientist but educator extraordinaire. And he told me that having that constant stream of new Mars imagery coming in each and every day is just what he and other mission planners had in mind. No sequestering of data that would only reach the public in dribbles much later. Instead, a communications-age feast of imagery that gets the attention of even the least space-minded.
Edward Belbruno is going to be doing an interview with me that I’ll publish on Centauri Dreams in installments (we’ll schedule that soon), but for now I’ll note how interesting is the synergy between what Dr. Belbruno does with ‘chaotic’ orbits (applying chaos theory to spacecraft trajectories) and our plans for moving further into the Solar System. This is the man who got the Japanese Hiten spacecraft to the Moon after the failure of the Hagoromo mission, with which all communications had been lost. Hiten was never intended to go to the Moon but was designed solely as a communications relay for Hagoromo. With scant fuel, only a Belbruno-style low fuel route would turn Hiten into a lunar voyager.
The subsequent success brought Belbruno’s work front and center for future mission concepts. You may recall that ESA’s lunar mission SMART-1 used similar orbital strategies. And one thing Belbruno brought up in the panel discussion was that as we move deeper into space, low-energy orbits could play a role in providing the needed supplies. You wouldn’t want to put a human crew on a vehicle that took years to reach a destination like the Moon, but if you’re talking about sending supplies to stock an initial base — or re-supply to a manned outpost on the Moon or Mars — such orbits make immediate sense. What Belbruno described sounded to me like a self-sustaining space-based infrastructure, rather than a series of one-shot missions that would never be repeated.
More on all this when I interview Dr. Belbruno for these pages, and I also have a similar interview lined up with Gregory Matloff, whose talk on solar sail technologies ran through the basics and touched on more exotic uses, such as solar sail methods to assist in asteroid deflection. I thought Dr. Matloff had the best line of the session when he opined in our panel discussion that anyone voting not to fund Arecibo’s planetary radar should be arraigned before the World Court in The Hague for crimes against humanity. That’s how strongly some of us feel about losing Arecibo’s watchdog capabilities to help us find potentially dangerous asteroids, and it was good to hear this being said on Capitol Hill.
For many people (though probably not regular Centauri Dreams readers), solar sails are purely theoretical constructs, so I was glad to hear Matloff explaining the history of the concept, dating back to 1974, when the Mariner 10’s mission to Mercury used the radiation pressure from solar photons for attitude control. That ad hoc demonstration said all that needed to be said about the utility of the momentum imparted by photons, and later missions, like the Russian Znamya reflectors or the 1996 thin film antenna unfurled from the Space Shuttle, kept the concept in play (the Znamya missions, to be sure, had their share of problems).
Louis Friedman, of course, had put huge amounts of time and effort into COSMOS-1, which would have been the first sail to go fully operational in space, but that 2005 launch failure was but a temporary setback. The Japanese had already demonstrated sail deployment in 2004 from a suborbital rocket — we’re learning how to do these things. Thinking back, too, to Dr. Friedman’s talk and the array of international missions now in the works, it’s striking that countries less concerned about democratic participation, like China, have in some ways an easier time at articulating a long-term space goal. Democracy is sprawling, messy, and it assumes the public’s support is a major factor in building space policy. Governments without elections to contend with set their own agendas.
Ponder the solar sail itself as seen through the prism of NASA. Work at Marshall Space Flight Center has progressed to the point that the solar sail is close to or at the status of operational viability. In other words, it wouldn’t take much to launch and deploy an actual sail mission in terms of technology. But without the needed funding, such missions don’t happen, which is why space policy can be so difficult to sort out, and so frustrating. That’s one price you pay for democracy, and while I certainly would never want to live under any other form of government, it does account for the fact that our ventures into space sometimes seem to proceed by fits and stars rather than in a stable continuum.
More on all these matters later, but for now, thanks to those who put this session together, especially Lee Billings and Sarah Glasser at Seed Media Group, and thanks, too, to a panel that gathered on relatively short notice and made it all happen. Lee tells me we may have video available of part or all of these sessions, so I’ll plan to link to that whenever possible. I’m struck (once again) by the enthusiasm and vitality space professionals bring to the job at hand. Despite its sometimes daunting setbacks, our venture into space seems unstoppable to me if we can move beyond our focus on the immediate and place it in the context of a gradual, inevitable migration that will help to preserve our planet while opening up vistas that one day will make the Moon and Mars seem tame.
by Paul Gilster | Nov 14, 2007 | Culture and Society |
By Larry Klaes
Tau Zero journalist Larry Klaes looks at Jon Lomberg’s stunning Galaxy Garden in Hawaii. Lomberg told Larry that working on the garden had made him appreciate on a primal level just how many objects there are in even a ‘small’ section of the Milky Way. So there’s one answer to the Fermi Paradox: If extraterrestrial civilizations are out there, maybe they’re simply too busy exploring to have gotten around to us!
There is a galaxy on Hawaii. Not an actual galaxy, of course, as a typical island of stars contains many billions of suns and spans hundreds of thousands of light years. The galaxy residing on the largest of that particular chain of Pacific islands is a 100-foot wide living representation of the vast stellar realm our planet and humanity dwells in, the Milky Way.
Called the Galaxy Garden, the idea for this unique project began about eight years ago in the mind of artist Jon Lomberg, who worked with Cornell University astronomer Carl Sagan on his Cosmos PBS television series and created the artwork placed on the golden Voyager Interstellar Record.
“The galaxy has always fascinated me,” says Lomberg. “One of the biggest misconceptions the public has is what a galaxy is. People can’t grasp the scale. They often confuse galaxy with solar system. I wanted to have a way to help people see and understand the Milky Way on a scale they can relate to.”
Lomberg cites two reasons for his using a garden to showcase our galaxy. One involves having a structure that people can actually walk through to be physically present in it. The other comes from seeing parallels between plant life and celestial objects, going back to his earlier artwork which combined biological and astronomical motifs, including the dandelion seed shape of the Spaceship of the Imagination that Sagan used to travel about the Universe in the Cosmos series.
Image: The centerpiece of the Paleaku Astronomy Center is the 100 ft. diameter model of the Milky Way. The scale is 1000 light years per foot, which is about 83 light years per inch. The Galaxy Garden is set on 1/4 acre of lawn, whose gentle swell suggests the observed warp of the actual galactic disk. Credit: Jon Lomberg.
“Star forming regions like the Orion Nebula always looked like flowers to me,” explains Lomberg “This is the basis for the idea of using plants to make a large model of the Milky Way galaxy.”
After searching for a place to literally and figuratively plant his idea, Lomberg was offered a plot by Barbara DeFranco, Director of the Paleaku Peace Garden Sanctuary. Paleaku Gardens is a nine acre botanical garden in Kona, Hawaii, on the western side of the island that facilitates educational, spiritual, and cultural programs. The garden declares its mission “is to offer a sanctuary for the advancement of individuals toward peace and harmony.”
“Without [DeFranco] there wouldn’t have been a Galaxy Garden,” said Lomberg. “She offered the land for free because she thought it would enhance her gardens. Barbara is a partner in this endeavor; she knows as much about gardening as I do about astronomy.”
Major funding for the heavy equipment to build the garden, the accompanying visitor’s center, and the one thousand plants required to represent the Milky Way came from the Change Happens Foundation. The man who endows that organization is a big fan of Carl Sagan and his Cosmos series. Seed money came from the New Moon Foundation.
Making and keeping the Galaxy Garden accurate fell to UC Berkeley astronomer Leo Blitz, who co-discovered the large “bar” of stars stretching across the galactic center. Blitz spent over two years mapping out the true structure of the galaxy for the garden.
“[Blitz] is the guy who kept me honest,” declares Lomberg. “He gave me a basis to start from. Even professional astronomers who think they understand the Milky Way will find their conceptions of it deepened by the Galaxy Garden.”
To give a sense of scale to this special project, each foot of the garden equals one thousand lights years, the distance light travels in one year moving at 186,000 miles each second – about six trillion miles. Each inch equals 83 light years.
Lomberg originally thought he could represent some of the 400 billion stars of the Milky Way with some kind of small flower, but he soon realized that even they would be too large at the garden’s scale, nor could he have enough.
In their place, Lomberg turned to using the gold dust croton plant, whose yellow speckled green leaves stand in for various fields of stars. One leaf holds our Solar System and most of our neighboring suns. The croton plant was also chosen for its longevity, slow growth, lack of thorns, and high tolerance to sunlight.
Image: A small yellow crystal earring shows the position of our Earth and Sun, though our solar system is actually 1,000 times smaller than the jewel. Nearby bright stars are also shown with different colored jewels. Credit: Jon Lomberg.
The nebulae, clouds of dust and gas from which stars are born, are depicted by the colorful flowers of the hibiscus plant. Smaller planetary nebulae, the signs of a sun on its way out of existence, are shown with smaller red and white flowers such as periwinkles and vincas.
Globular clusters, spherical collections of hundreds of thousands of stars, are represented by dracaena trees. These plants were chosen to show some of the clusters which dwell “above” the plane of the Milky Way’s spiral disk, though Lomberg notes it will take several years for the thin-trunked trees to attain the proper height.
Traveling in towards the center of our galaxy, visitors will find the aforementioned galactic bar represented by an oval of small gray boulders. Inside that formation, at the very core our stellar island, is a water fountain representing the supermassive black hole residing there. Four million times more massive than our yellow dwarf sun, the galaxy’s black hole sits at the center of the Milky Way, constantly ingesting interstellar dust and gas and the occasional star.
“I was very mindful of how important it was for Carl Sagan to have people understand our place in the Cosmos,” said Lomberg. “The Galaxy Garden is an artist’s culmination of my whole career of doing galaxies. One of the first paintings Carl ever bought from me was one depicting where we were in the galaxy. We never talked about the Galaxy Garden concept, but Carl; always liked the metaphorical approach to explaining the Universe. In my heart, this garden is dedicated to Carl Sagan. It carries on the tradition of public elevation that he cared about so much.”
The Galaxy Garden, which opened to the public on October 21, can also be viewed online.
