by Paul Gilster | Feb 7, 2013 | Exoplanetary Science |
Returning from Huntsville after the Tennessee Valley Interstellar Workshop, I was catching up on emails at the airport when the latest news about exoplanets and red dwarfs popped up on CNN. It was heartening to look around the Huntsville airport and see that people who had been reading or using their computers were all looking up at the screen and following the CNN story, which was no more than a thirty second summary. The interest in exoplanets is out there and may bode good things for public engagement in space matters. At least let’s hope so.
The workshop was a great success, and congratulations are owed to Les Johnson, Robert Kennedy, Eric Hughes and the entire team that made this happen (a special nod to Martha Knowles and Yohon Lo!). This morning I want to focus on the exoplanet news as a way of getting back on schedule, but tomorrow I’ll start going through my notes and talking about the Huntsville gathering. I’m hoping to have several articles in coming weeks from participants in the event on the work they are doing, and I have plenty of comments about the presentations, so the Huntsville coverage that begins tomorrow should extend into next week.
As to the exoplanet news, Courtney Dressing (Harvard-Smithsonian Center for Astrophysics) went to work on the Kepler catalog of 158,000 stars to cull out all the red dwarfs. She and the CfA’s David Charbonneau found that almost all of the identified stars were smaller and cooler than had been thought, which has the effect of lowering the size of the detected planets. An additional result is to move the habitable zone somewhat further in. The duo could find 95 planet candidates among these red dwarfs.
Image: This artist’s conception shows a hypothetical habitable planet with two moons orbiting a red dwarf star. Astronomers have found that 6 percent of all red dwarf stars have an Earth-sized planet in the habitable zone, which is warm enough for liquid water on the planet’s surface. Since red dwarf stars are so common, then statistically the closest Earth-like planet should be only 13 light-years away. Credit: David A. Aguilar (CfA)
Let’s pause for a moment on the analysis. Dressing and Charbonneau were comparing the observed colors of the stars to a model developed by the Dartmouth Stellar Evolutionary Program. The final sample in the study contained 3897 dwarf stars with revised temperatures cooler than 4000 K, and the revisions to stellar temperatures brought the stars down 130 K in temperature while reducing their size by 31 percent. The analysis proceeded to refit the light curves of the planet candidates to get a better understanding of their radii.
I wish I could have tracked the news conference live but was in transit at the crucial moments. Those of you who also missed it may want to check the archived version at the CFA’s site. The key point is on the opening slide: “Earth-like Planets Are Right Next Door.” Which is something of a stretch because we are talking about M-class stars where a planet in the habitable zone is probably tidally locked. Assuming (and it’s an open question) whether a benign climate for carbon-based life could exist on such a planet, it’s still an environment much different from the Earth, with a star that stays in the same position in the sky and night and day are endless.
Still, this is interesting news: The 95 planetary candidates imply statistically that at least 60 percent of red dwarfs have planets smaller than Neptune. Out of the 95, only three were close enough to Earth in terms of size and temperature to be considered ‘Earth-like.’ In other words, about six percent of all red dwarfs are found to have a planet like the Earth. 75 percent of the closest stars to the Sun are red dwarfs, leading Dressing to calculate that the closest Earth-like world is likely to be no more than 13 light years away. Again, this is for red dwarfs. The analysis of other stellar types like the intriguing G- and K-class stars Centauri A and B continues.
Here’s the payoff, from the paper. The authors have just noted that the high rate of habitable zone planets around nearby stars means that future missions designed to study these worlds will have plenty to work with::
Given that there are 248 early M dwarfs within 10 parsecs, we estimate that there are at least 3 Earth-size planets in the habitable zones of nearby M dwarfs awaiting the launch of TESS and JWST. Applying a geometric correction for the transit probability and assuming that the space density of M dwarfs is uniform, we ?nd that the nearest transiting Earth-size planet in the habitable zone of an M dwarf is less than 29 pc away with 95% con?dence. Removing the requirement that the planet transits, we ?nd that the nearest non-transiting Earthsize planet in the habitable zone is within 7 pc with 95% con?dence. The most probable distances to the nearest transiting and non-transiting Earth-size planets in the habitable zone are 18 pc and 4 pc, respectively.
I mentioned the G- and K-class stars Centauri A and B above, but I don’t want to leave the third element of the trio out, it being a red dwarf. The radial velocity work on Proxima Centauri continues, allowing us to constrain the size of possible planets usefully. This is not part of Dressing and Charbonneau’s study, but I’ll mention it here because it’s obviously germane. Using seven years of UVES spectrograph data from the European Southern Observatory, Michael Endl (University of Texas) and team have found no planet of Neptune mass or above out to 1 AU from Proxima, and no ‘super-Earths’ above 8.5 Earth masses in orbits of less than 100 days.
As to Proxima’s tight habitable zone (0.022 to 0.054 AU), no ‘super-Earths’ above about two to three Earth masses exist here. The habitable zone around Proxima corresponds to orbits ranging from 3.6 to 13.8 days, and you can see that we still have plenty of room for an interesting Earth or Mars-sized world around this closest of all stars to Earth. Adding more data points to what we already have on Proxima should gradually allow us to get to a better idea of what’s actually there.
But back to Dressing and Charbonneau’s red dwarfs. The three habitable zone candidates are Kepler Object of Interest (KOI) 1422.02 (90 percent Earth size in a 20-day orbit); KOI 2626.01 (1.4 Earth size in a 38-day orbit); and KOI 854.01 (1.7 times Earth size in a 56-day orbit). None of these are closer than 300 light years. The paper points out that while Kepler will need several more years of observation to detect Earth-size planets in the habitable zones of G-class stars (this is due to higher than expected stellar noise), the observatory is already able to detect Earth-size planets in the habitable zone of red dwarfs. We get not one but many transits per year and we have 1.8 times more likelihood of a transit than around a star like the Sun.
Thus we get this:
…the transit signal of an Earth-size planet orbiting a 3800K M star is 3.3 times deeper than the transit of an Earth-size planet across a G star because the star is 45% smaller than the Sun. The combination of a shorter orbital period, an increased transit probability, and a deeper transit depth greatly reduces the di?culty of detecting a habitable planet and has motivated numerous planet surveys to target M dwarfs…
Another advantage of M dwarfs is that confirming a planetary candidate is made easier because the radial velocity signal of a habitable planet here is considerably larger than that of a habitable zone planet around a G-class star. Given that the James Webb Space Telescope should be able to take spectra of Earth-sized planets in the habitable zone around M-dwarfs — and that it cannot do this for comparable planets around more massive stars — our first atmospheric readings from a habitable zone planet are probably going to come from these small red stars.
The paper is Dressing and Charbonneau, “The Occurrence Rate of Small Planets Around Small Stars,” to be published in The Astrophysical Journal (draft version online).
by Paul Gilster | Feb 3, 2013 | Culture and Society |
Air travel presents us with challenges we seldom anticipate. Flying into Charlotte on Sunday I had developed a ferocious headache. I was headed to the Tennessee Valley Interstellar Workshop in Huntsville and had a long enough layover in Charlotte to seek out a pain reliever with decongestant properties. The ridiculous thing was that I couldn’t get the plastic mini-pack open. The little symbol showed me tearing off the corner of the packet, but it wouldn’t tear for me, and it wouldn’t tear for the guy who happened to be sitting next to me at the USAir gate.
It became clear that I needed something sharp to get into this packet, but it was also clear that I was in an airport, the very definition of which these days is to prevent passengers from having anything sharp. I finally took the packet back to the kiosk I bought it from and demanded redress. The lady looked askance at me, looked at the packet, and opened it effortlessly. Further comment seems superfluous.
By the time I got off the plane in Huntsville the headache was much better, and I was surprised to find my shoulder tapped by Andreas Hein, who heads Icarus Interstellar’s worldship project, called Hyperion. We shared a taxi to the hotel, where the lobby was stuffed with interstellar folk like Rob Swinney, now project head for Project Icarus, Claudio Maccone (who will give a keynote on Tuesday), Kelvin Long (head of the Institute for Interstellar Studies) and my buddy Al Jackson, just in from Houston. Al was kind enough later to drive me over to the venue for the evening reception, pictures of which you see here. Al and I owe much to his Garmin GPS.
Image: Andreas Hein (left) and Rob Swinney, of Icarus Interstellar.
The conference — or in this case ‘workshop’ — dilemma is again facing me. There was a day when I thought ‘live blogging’ would make sense for Centauri Dreams, but the more examples of live blogging I read, the less I like the idea. At both 100 Year Starship conferences I mainly sent out tweets, finding Twitter an interesting platform for conference coverage, but one that nonetheless distracted me from making the kind of detailed notes I needed to be working with, just as live blogging did. So this time around, although I may do the occasional tweet (@centauri_dreams), I’ll mostly be paying attention to the speakers and making notes that will turn into more coverage after the workshop is over.
Image: A cordial host, MSFC’s Les Johnson, co-editor of Going Interstellar (Baen, 2012).
So bear with me if Centauri Dreams is off its regular schedule for a few days, though I’ll slip things in wherever possible, and next week we’ll take a close look at the papers here. Meanwhile, there should be no interruption in comment moderation, which I’ll get to as time allows. I will tell you this for now. Robert Kennedy (The Ultimax Group) makes a drink called the Alpha Centauri Sunrise, and I have not only had one, but have also snapped a surreptitious photo of the recipe. Robert later said it would be OK for me to share it, so at some point during the week, I’ll explain how to make this estimable drink. Hint: Three berries are involved. And moonshine.
by Paul Gilster | Feb 1, 2013 | Culture and Society |
These days we know that perhaps a million objects the size of the Tunguska impactor or larger are moving through nearby space, and talk of how to deflect asteroids has become routine. Given our increasing awareness of near-Earth objects, it wouldn’t be a surprise to hear of a new Hollywood treatment involving an Earth-threatening asteroid. But I wouldn’t have expected a science fiction series that ran from 1959 to 1960 would have depicted an asteroid mission and the dangers such objects represent.
Nonetheless, I give you “Asteroid,” from the show Men Into Space, with script by Ted Sherdeman. Viewers on November 25, 1959 saw the show’s protagonist Col. Edward McCauley (William Lundigan) take a crew to ‘Skyra,’ a 3.5-kilometer long rock that scientists believed might hit the Earth. The crew assesses whether the asteroid is salvageable for use as a space station and decides there is no other choice but to destroy Skyra, which they do at the cost of considerable suspense as McCauley works to save an astronaut separated from the others while the clock ticks down. The suspense would have been heightened by the fact that this was a show on which astronauts sometimes died and hard sacrifices were the order of the day.
I report on all this with the help of John Fredriksen’s new book Men Into Space (BearManor Media, 2013), which arrived in the mail the other day. Like me, Fredriksen had watched the show in its all too short run while growing up in the Sputnik era. He was taken with the understated but tough role of McCauley, who was depicted as participating in all the significant space missions of his time, from the first lunar journeys to building a space station and, at the time of the show’s cancellation, two attempted flights to Mars that were plagued by problems and aborted.
You could say that Mars as a destination hovers over all this show’s plots. Its final episode, “Flight to the Red Planet,” did get McCauley and team as far as Phobos, where their ship was damaged enough to force an early departure without landing on Mars itself. The Mars of this episode is a compelling target, because from Phobos, in these years not long before Mariner 4, the crew can see waterways that seem to be feeding an irrigation system. This is Percival Lowell’s Mars in an episode surely designed to build into a second season, but that season was unfortunately not to be.
Fredriksen’s book walks fans through all the episodes, with extensive quotes from the scripts and stills that capture the look and feel of the production. If some of these images seem familiar, it may be because Chesley Bonestell was asked to produce concept art for the show, resulting in sharply defined lunar landscapes reminiscent of his paintings. Lewis Rachmil, who produced Men Into Space, would have been familiar with Bonestell’s Hollywood work, which included Destination Moon (1950), When Worlds Collide (1951) and Conquest of Space (1955), not to mention the famous space series in Collier’s.
Frederic Ziv, who headed up ZIV Productions, didn’t stop with Bonestell when it came to making his show as realistic as the times would allow. Sputnik had been launched in 1957 and Ziv had been exploring doing a different kind of space show for CBS ever since. From the book:
Unlike the children-oriented science fiction programming of a few years previous, the tenor of the times now demanded an approach that was rigorously scientific to appease more mature audiences. Ziv, who prized flaunting the technical expertise assisting his programs, also believed that obtaining Department of Defense cooperation facilitated access to their extensive and elaborate space facilities. At length, his show acknowledged help from the Air Force Air Research and Development Command, the Office of the Surgeon General, and the School of Aviation Medicine. Ziv’s credibility was further enhanced with Air Force technical experts who were brought into the scripting and consulting process, receiving credits in the end titles.
Couple this with location shooting at research facilities like Edwards Air Force Base and Cape Canaveral and stock footage of missile launches of the time, along with special effects crews working with von Braun-style three-stage rockets launching capsules that were almost as tiny and cramped as Apollo. Men Into Space turned out to be complicated and expensive. Fredriksen notes that ZIV gave the Air Force the final say in keeping the show realistic, which is why the more fantastic tropes of 1950s science fiction make no appearance. Personality conflicts and equipment malfunctions took the place of ray guns and aliens.
Fredriksen gives all the details, including a summary of each of the show’s 38 episodes. It’s a nostalgic trip for those who remember watching Men Into Space, and it brings back to life memories many of us had long forgotten. After all, this was a short-lived series that survived only in occasional syndication and in some of the space suits and ship interiors that wound up being used again in episodes of The Outer Limits (I knew they looked familiar!). Nominated for a Hugo Award in 1960, the show lost out to The Twilight Zone, and critics sniped at its mundane special effects and earnest quest for authenticity. Despite the promise of Mars, the show was axed in September of that year.
But early impressions count, and it’s safe to say that this show captured more than a few young minds, not the least of them being Fredriksen’s, for whom the experience was indelible:
May future generations rekindle that sense of awe, the ability to dream a better future, and a fixed determination to cross the gulf separating imagination from reality as we did, and joyously so, in the 1950s. If Men Into Space encapsulates the essence of a departed, heroic ideal, it is also a good measure of everything we have lost as a space-faring culture.
As for me, I’ve always been a William Lundigan fan. This is a guy who walked away from Hollywood in 1943 to join the Marines, where he served with the 1st Marine Division on Peleliu, an operation that ranks with Iwo Jima in terms of the ferocity of combat and the staggering percentage of casualties. He went on to Okinawa as a combat photographer and, having received two Bronze Stars, returned to acting after the war. 1954’s Riders to the Stars was his first science fictional outing in a show about astronauts trying to capture meteorites in flight. His work with Ivan Tors on that film fed into a role in the series debut of ZIV’s Science Fiction Theater.
Of Men Into Space, Lundigan would say: “…this was not some Buck Rogers type show. It was not a science-fiction series but a science-fact series. You might even say it’s a combination of a public service show and a dramatic series.” Even he would become exasperated with the quality of writing in some of the later shows, but as Fredriksen’s book makes clear, there was still inspiration to be found here of the kind that awakens young people to careers in engineering and science. With a little better luck and a second season landing on Mars, Men Into Space might be far more than the obscure recollection it is today, and the name ‘McCauley’ might be as recognizable as ‘Kirk.’
