by Paul Gilster | Apr 30, 2005 | Exoplanetary Science
The race to confirm the first image of an exoplanet takes yet another turn with the announcement that a young brown dwarf some 200 light years from Earth really is orbited by a planet that is five times the mass of Jupiter. We looked at this brown dwarf, called 2M1207A, in an entry last September. When the object visually near it was first discovered about a year ago, there remained the possibility that the apparent planet was a background star. But new observations seem to rule this out.
“Our new images show convincingly that this really is a planet, the first planet that has ever been imaged outside of our solar system,” says Gael Chauvin, astronomer at ESO and leader of the team of astronomers who conducted the study.
And Benjamin Zuckerman, UCLA professor of physics and astronomy and a member of the international team working on 2M1207A, adds this:
“The two objects – the giant planet and the young brown dwarf – are moving together; we have observed them for a year, and the new images essentially confirm our 2004 finding. I’m more than 99 percent confident.”
The giant world now called 2M1207b is located some 55 AU from its parent, which would place it well beyond the orbit of Pluto in our Solar System. 2M1207b is 100 times fainter than the brown dwarf it apparently orbits, and its spectrum shows the signature of water molecules, confirming its low temperature. Spectral data and analysis of the gravitational field of the object suggest the 5 Jupiter-mass finding, although the final determination could be somewhat less.
The team’s paper on this work has been accepted by Astronomy & Astrophysics. Another paper from the same team, about which more later, will suggest the imaging of a companion some 13 to 14 times the mass of Jupiter orbiting the star AB Pictoris, some 150 light years from Earth. That places the object on the borderline between brown dwarf and planet, a boundary that will doubtless be the subject of increasing study as more such findings emerge. For more on 2M1207b, see this European Southern Observatory press release.
by Paul Gilster | Apr 29, 2005 | Culture and Society
The possible asteroid belt around the star HD69830, covered here in a recent entry, caused several days of pondering and a scouring of the Centauri Dreams library. This exoplanetary belt seems to be 25 times as dense as our own, and as close to its parent star as the orbit of Venus is to ours. That would make for an unforgettable celestial display every night, a belt of light cutting across the sky. The idea of a ‘ringed star’ finally drew forth the memory: an old Murray Leinster story called “Proxima Centauri.”
Published in the March 1935 issue of Astounding Stories (an issue in which future Astounding editor John Campbell would have two stories, one of them under his pseudonym Don A. Stuart), “Proxima Centauri” tells the story of the Adastra, a vast starship a mile in diameter as it makes the first interstellar crossing. Ahead in the viewfinders, Proxima Centauri reveals itself to be surrounded by a glowing ring that comes into view long before the planets in the Proxima system. That ring stayed in my subconscious all these years since I first read the story in Isaac Asimov’s collection Before the Golden Age (New York: Doubleday & Company, 1974).
Make no mistake: “Proxima Centauri” is a creaky tale, freighted with an
implausible (and irritating) romance, and its technology is pure 1930s. Today we talk about starships driven by sails far lighter than the transparent film that wraps a pack of cigarettes. In Leinster’s story, the enormous ship is described as ‘monstrous’ and ‘apparently too huge to be stirred by any conceivable power,” although as the story opens, we see her decelerating:
At a dozen points there flowed out tenuous purple flames. They gave little light, those flames — less than the star ahead — but they were the disintegration blasts from the rockets which had lifted the Adastra from the surface of Earth and for seven years had hurled it on through interstellar space toward Proxima Centauri, nearest of the fixed stars to humanity’s solar system.
Leinster, in reality pulp writer and inventor Will F. Jenkins, would write numerous stories that helped define early science fiction, including many with much more to recommend them than “Proxima Centauri.” His “First Contact” is still remembered as a classic of the genre, as is “Exploration Team,” on the man vs. machine debate for examining other worlds, and “Sideways in Time,” an early tale of parallel universes.
His characters could be one-dimensional but what recommends Leinster and so much writing from this period is the sheer audacity of the concepts. We forget today how breathtaking the fictionalization of interstellar flight once was, bombarded as we are with television and movie images that make these vast journeys routine. Leinster’s crew would encounter a lethal intelligence in the form of a race of intelligent plants before a deus ex machina solution would open up the Centauri system to human colonization. Like I said, it’s a creaky tale, but one of the first in the American science fiction magazines to make the Centauri crossing and a reminder of that sense of participatory awe that readers in that era felt. Can we recapture that awe today?
Not long ago a friend asked why, once the hubbub of the Titan landing had passed, the media seemed to have forgotten Cassini. It’s a question worth pondering in a week that brought us a workable desktop fusion device. The answer to the world’s power power problems it’s not, but Seth Putterman’s team at UCLA has delivered a tool that offers new options in ion propulsion and the prospect of a deeper understanding of fusion’s deep mysteries.
Part of the Centauri Dreams library is a collection of old pulp magazines, garish covers largely intact, culled from dealers and other collectors over the decades. How odd that their innocent incredulity and hope of future wonders should now appear dated, when the remarkable events of today — from finding new exoplanets to creating fusion in a device the size of a toaster — should rightfully produce even more awe in us.
Putterman’s work is presented in “Observation of nuclear fusion driven by a pyroelectric crystal,” Nature 434, 1115-1117 (28 April 2005). The best collection of Murray Leinster’s short stories is First Contacts: The Essential Murray Leinster (Framingham, MA: New England Science Fiction Association, 1998).
by Paul Gilster | Apr 28, 2005 | Astrobiology and SETI
Is biology as much a driver for interstellar travel as technology? Hungarian engineer Csaba Kecskes argues that it may be so; indeed, biology may hold the answer to Enrico Fermi’s famous ‘where are they?’ question about extraterrestrials. While most scenarios for the growth of technological civilizations assume a ‘galactic empire’ model — colonization modeled after 16th Century explorers, or the spread of Polynesian cultures through the islands of the Pacific — Kecskes uses a different analogy: the migration of life from water to land. As he writes in a 2002 paper in Acta Astronautica:
Using this analogy, the [Fermi] paradox simply disappears; fishes never meet lizards or rats. (In the Earth’s biosphere there are large groups of animals which live in a mixed water/land environment, but every analogy has its limits. Man’s adaptation to the space environment, especially to weightlessness, probably will create a very effective and final barrier).
In other words, technical civilizations may eventually lose interest in planets as they undergo biological adaptation to space-based environments. Here, then, is a possible growth path for an interstellar civilization, listed in order of development:
Planet dwellers biologically adapted to strong gravity, high air pressure and natural food resources who utilize raw materials mined from the planet’s crust.
Asteroid dwellers who live inside asteroids, biologically adapted to conditions like near-zero gravity, low air pressure and closed-cycle biological support systems. They draw energy from solar cells and mine raw materials from the asteroids around them.
Interstellar travelers, who live in limited-range interstellar spaceships, biologically adapted to smaller closed-cycle life support systems and higher levels of radiation, who draw energy from stellar systems they stop at as they explore.
Space dwellers, who live in unlimited-range interstellar spaceships, biologically adapted to even smaller life-support systems, who use the interstellar medium for raw materials, drawing energy from hydrogen fusion or other exotic resources.
It’s a fascinating paper, worth digging up if you have a nearby engineering library (or access to the right online databases). Kecskes surveys the possible scenarios leading to a level 2 asteroid-based culture, from the ‘escapist’ scenario (oppressed minorities create a new homeland in space) to the ‘power show’ scenario, a kind of updated race to the Moon based on competing superpowers. The author thinks the latter, backed by massive government support, is the most likely outcome, and that the development of space manufacturing technologies will follow as a consequence of this colonization. A genuine asteroid-based society will develop industrial capabilities that should provide the first wave of growth into the interstellar medium.
Image: Asteroid 951 Gaspra, photographed on October 29, 1991 by the Galileo spacecraft. Could asteroids like this become the home of a future technological civilization? Credit: NASA.
Centauri Dreams‘ take: the Fermi paradox still seems robust at this end. Biologically adapted or not, space-based civilizations will surely have enough curiosity to want to examine the planets they encounter in their travels. They may not be empire-builders, but they will remain explorers. On the other hand, detecting traces of such advanced cultures may be more difficult than we suppose. I am reminded of Michio Kaku’s caution that the chances of a civilization like ours detecting a Type III Kardashev civilization (one capable of using the resources of an entire galaxy) would be like a stream of ants encountering an interstate highway and understanding it to be an artifact.
Kecskes’ paper is “Scenarios Which May Lead to the Rise of an Asteroid-Based Technical Civilization,” in Acta Astronautica Vol. 50, No. 9, pp. 569-577 (2002). This follows the earlier paper “The Possibility of Finding Traces of Extraterrestrial Intelligence on Asteroids” that the author wrote for the Journal of the British Interplanetary Society in 1998 (Vol. 51, p. 175).
by Paul Gilster | Apr 27, 2005 | Outer Solar System
Scientists anticipated that Titan would be a model laboratory for studying the organic chemistry that eventually led to life on the primitive Earth. So the discovery of complex mixtures of hydrocarbons and carbon-nitrogen compounds came as no surprise. What was unusual was where they found them: in Titan’s upper atmosphere.
Organic materials were expected on Titan because nitrogen and methane, the two primary components of its atmosphere, should form complex hydrocarbons when exposed to sunlight or energetic particle radiation from Saturn’s magnetosphere. But the frigid temperatures on the Saturnian moon led most researchers to believe such hydrocarbons would condense and eventually wind up on the moon’s surface. Instead, Cassini’s ion and neutral mass spectrometer helped them find hydrocarbons galore in Titan’s outer atmosphere.
Image: This natural color composite (taken during the April 16 flyby) shows approximately what Titan would look like to the human eye: a hazy orange globe surrounded by a tenuous, bluish haze. The orange color is due to the hydrocarbon particles which make up Titan’s atmospheric haze. This obscuring haze was particularly frustrating for planetary scientists following the NASA Voyager mission encounters in 1980-81. Fortunately, Cassini is able to pierce Titan’s veil at infrared wavelengths. Credit: NASA/JPL/Space Science Institute.
“We are beginning to appreciate the role of the upper atmosphere in the complex carbon cycle that occurs on Titan,” said Dr. Hunter Waite, principal investigator of the Cassini ion and neutral mass spectrometer and professor at the University of Michigan, Ann Arbor. “Ultimately, this information from the Saturn system will help us determine the origins of organic matter within the entire solar system.”
More on these findings in this Jet Propulsion Laboratory news release. Cassini’s most recent flyby occurred on April 16, as the spacecraft approached within a little over 1,000 kilometers of the moon’s surface. It was Cassini’s sixth close approach, but 39 more are scheduled, the next on August 22.
And be aware of this interesting news re Enceladus. The Cassini encounter with the moon on July 14 will now take place at a much lower altitude than the 1,000 kilometers first planned. The new target is 175 kilometers (109 miles), the lowest altitude flyby of any object planned for the Cassini mission. The change comes amid news that Cassini has discovered dust particles near Enceladus that indicate either a dust cloud around the moon, or interaction with Saturn’s outermost ring. “It will take a few more flybys to distinguish if the dust flux is originating from the E-ring as opposed to a source at Enceladus,” said Dr. Thanasis Economou, lead researcher on Cassini’s high rate detector, part of a larger instrument aboard the craft called the cosmic dust analyzer.
by Paul Gilster | Apr 26, 2005 | Deep Sky Astronomy & Telescopes
When theories aren’t borne out by observation, the problem just may be the size of the dataset. As witness recent work on gravitational lensing, that phenomenon where light is distorted and magnified by the gravitational pull of galaxies and other matter as it makes its immense journey from distant quasars to the Earth. Such lensing has been observed for over a decade, but just how the light is magnified, and on what scale, has until now been an elusive question. And answers to it haven’t seemed to fit the standard model of cosmology, one in which visible galaxies represent only a small part of the mass of a universe seemingly filled with dark matter.
Now researchers from the Sloan Digital Sky Survey (SDSS) have been able to perform a large-scale study of such magnification, and their theories do gibe with the standard model. The team was able to measure the brightness of some 200,000 quasar sources and determine the precise magnification caused by gravitational lensing. The new calibration goes a long way toward deepening our understanding of lensing, which is a fundamental consequence of Einstein’s theory of General Relativity. The answers emerged only when enough data had been collected to see the overall pattern.
“While many groups have reported detections of cosmic magnification in the past, their data sets were not large enough or precise enough to allow a definitive measurement, and the results were difficult to reconcile with standard cosmology,” added Brice Menard, a researcher at the Institute for Advanced Study in Princeton, NJ.
Image: The left panel shows a grid of points representing background quasars. The right panel is the same grid after being “gravitationally lensed” by the cluster of galaxies shown in the center of the panel (the magnitude of the effect is exaggerated to make it apparent to the eye). As predicted by Einstein’s Theory of General Relativity, the light from the background images is bent and distorted as it passes by the gravitational potential of the galaxies and dark matter in the cluster on its way to observers on Earth. The images nearest the foreground cluster have a larger area than their counterparts in the left panel, making them brighter. This effect is known as cosmic magnification. (Image credit: Joerg Colberg, Ryan Scranton, Robert Lupton, SDSS)
The Sloan Digital Sky Survey is mapping one-quarter of the entire sky in a bid to catalog the positions and absolute brightness of hundreds of millions of celestial objects. A major part of this effort is the measurement of the distances to more than a million galaxies and quasars. The breakthrough in the current work is the ability of Sloan researchers to extract quasars from the SDSS data. They did this by using statistical techniques that allowed them to find a quasar sample ten times larger than previous studies.
“With the quality data from the SDSS and our much better method of selecting quasars, we have put this problem to rest,” researcher Ryan Scranton said. “Our measurement is in agreement with the rest of what the universe is telling us and the nagging disagreement is resolved.”
Centauri Dreams note: One of the targets for probes to the nearby interstellar medium is the gravitational lensing point some 550 AU from the Sun. A space telescope placed there would be able to see an amplified image of objects (globular clusters, for example, or intriguing exoplanets) that are occulted by the Sun (as seen from the spacecraft). Interestingly, the light from such gravity-focused objects remains along the focal line at distances greater than 550 AU; in fact, the focal line extends to infinity.
For more on this, see Gregory Matloff, “Solar Sailing for Radio Astronomy and SETI: An Extrasolar Mission to 550 AU,” Journal of the British Interplanetary Society 47 (1994), pp. 476-484. Also see Claudio Maccone, “The Quasat Satellite and its SETI Applications,” in G. Marx, ed., Bioastronomy: The Next Steps (Norwell, MA: Kluwer Academic Publishers, 1988). Quasat is a design for an inflatable radio telescope originally proposed by Alenia Spazio (Turin, Italy) in the late 1980’s; Maccone led the investigation into deep space applications for the spacecraft.