by Paul Gilster | Dec 6, 2004 | Exoplanetary Science
It was two years ago that astronomers at the Geneva Observatory in Sauverny, Switzerland, released their findings on the star HD 202206. The conclusion: An object 17 times as massive as Jupiter orbits the star at 0.82 AU. A second planet has now been found at 2.55 AU, this one over twice as massive as Jupiter.
So is the heavier object a planet or a brown dwarf? The issue is called into question by the second discovery. Science News is running a story in its November 27 issue pointing out that by the standards of the International Astronomical Union, brown dwarfs must be heavy enough to burn deuterium at their core, while remaining light enough so as not to burn any other nuclear fuel. The heavy object around HD 202206 fits this category well, since brown dwarfs normally range from 13 times the mass of Jupiter to 75.
But there’s a twist. The two objects are gravitationally locked in a peculiar synchrony that has not previously been observed, with the inner body orbiting the star exactly five times for every single orbit of the more distant one. And here’s where it gets intriguing: the orbital mechanics imply that both objects were born simultaneously, in which case, the supposed brown dwarf would actually be the heaviest planet ever discovered.
Here is a precis of this work, which was led by Alexandre Correia of the University of Aveiro in Portugal:
Long-term precise Doppler measurements with the CORALIE spectrograph reveal the presence of a second planet orbiting the solar-type star HD 202206. The radial-velocity combined fit yields companion masses of 17.4 M_Jup and 2.44 M_Jup, semi-major axis of a = 0.83 AU and 2.55 AU, and eccentricities of e = 0.43 and 0.27, respectively. A dynamical analysis of the system further shows a 5/1 mean motion resonance between the two planets. This system is of particular interest since the inner planet is within the brown-dwarf limits while the outer one is much less massive. Therefore, either the inner planet formed simultaneously in the protoplanetary disk as a superplanet, or the outer Jupiter-like formed in a circumbinary disk, the former explanation being favored by the observed mean-motion resonance. We believe this singular planetary system will provide important constraints upon planetary formation and migration scenarios.
The abstract for “A pair of planets around HD 202206 or a circumbinary planet?,” can be found here, with a link to the full paper (PDF warning).
We are left with a question of definition. Can some massive objects that otherwise fit our understanding of brown dwarfs actually be planets, while others match our theories of brown dwarf formation? The jury on this one is still out, at least until we understand more about synchrony and its causes in extrasolar planetary systems.
by Paul Gilster | Dec 4, 2004 | Culture and Society
As promised earlier in the week, here is a snippet of Frederick Turner’s “Worlds Without Ends” essay from 1996; more on what he means by the ‘charm industries’ in a later posting. I’m not aware of an online version of this piece, but it’s well worth seeking out in your local library.
The arts and pleasures of the charm industries take up time and space; they also paradoxically increase both time and space by their magical powers of illusion, delay, inner articulation, and concentrated attention. But time and space, with the present buildup of physical, temporal, and cultural waste product on our planet, are becoming increasingly scarce and increasingly at a premium. We are swamped by mountains of junk information, junk production, junk cultural overflow. We will be prepared to pay top dollar for silence, horizons, the threat and presence of death, the strange and mystical experience of uneventful time. Japanese Heian princes, with all the resources of a rich civilization open to them, sought the exquisite boredom of glacially slow Noh drama and court music. American and European millionaires outfit one-man ocean-going yachts and, on the fine edge of loneliness, terror, and tedium, sail round the world. Our civilization as a whole will seek out the ultraviolet-ravaged red wastes of Mars, the voiceless empty grandeur of the Jovian moons.
New planetary habitats obviously offer enormous amounts of empty space. Less obviously, they also offer huge quantities of empty time. Outer space has an inexhaustible resource, which is temporal separation from the home planet. Nobody on Mars can have a phone conversation with anyone on Earth, because the light that carries the message takes time to get from place to place, and even a one-minute time lag puts a gap between two people almost as great as the grave: Mars is at least three minutes away, and sometimes as much as 20. The times of Mars and Ganymede are empty of Earthly chatter and Earthly information overload. The relativistic time-separation from Earth of even the closest planets imposes an impenetrable barrier of privacy, and creates huge unexploited temporal niches for the coming charm industries. The tragic existential choices that faced emigrants to the New World, and that made possible their creation of new societies and new alternatives for the human race, will once again be possible.
From Frederick Turner, “Worlds Without Ends, originally in Reason, June 1996, Vol. 28, Issue 2.
by Paul Gilster | Dec 3, 2004 | Astrobiology and SETI, Outer Solar System
The Huygens probe remains on schedule to separate from the Cassini Saturn orbiter early on December 25, entering Titan’s atmosphere to parachute to the still mysterious surface. Whether the probe will land on organic goo, an ocean of liquid methane, ethane and nitrogen or a solid surface is still unknown.
The Titan approach goes like this: after separation, Huygens will coast for 20 days, arriving at Titan on January 14. The probe will encounter the atmosphere at an altitude of 1270 kilometers (789 miles); Huygens will decelerate to a landing speed of 5 meters per second before touchdown. According to this news release from Britain’s Particle Physics and Astronomy Research Council, the landing bump will be the equivalent of jumping off a chair onto the ground.
Image: Titan’s atmosphere – After entering Titan’s atmosphere, Huygens’ parachute system will be deployed for the 2-2½ hour descent, during which most of the scientific measurements will be made. This artist’s impression shows the Probe suspended from the stabiliser parachute passing through the clouds that are expected at around 20 km altitude. The descent will occur during daylight to provide the best illumination conditions for imaging the clouds and surface. Credit: ESA
And in a tantalizing comment, professor Ian Halliday, chief executive of
PPARC, adds this:
“Titan is a mysterious place and raises many scientific questions. Its thick atmosphere is mostly nitrogen, but there are also methane and many other organic compounds. Some of them would be signs of life if they were on our planet. Organic compounds form when sunlight destroys methane. If sunlight is continuously destroying methane on Titan, how is methane getting into the atmosphere?”
by Paul Gilster | Dec 3, 2004 | Astrobiology and SETI
The news from Meridiani Planum continues to be encouraging. A special issue (Dec. 3) of Science offers eleven articles by scientists connected with the Mars rover missions, this marking the first peer-reviewed presentation of data from the Opportunity rover. The articles cover Opportunity’s first 90 days exploring the Eagle Crater, before it moved on to the large crater called Endurance.
From Steve Squyres, Cornell professor of astronomy, who led the team
of rover scientists along with Dr. Ray Arvidson of Washington University (St. Louis), as quoted in a Jet Propulsion Laboratory press release:
“Liquid water was once intermittently present at the Martian surface at Meridiani, and at times it saturated the subsurface. Because liquid water is a key prerequisite for life, we infer conditions at Meridiani may have been habitable for some period of time in Martian history,” according to Squyres, Arvidson and other co-authors.
And in one of the papers he wrote for Science, “In Situ Evidence for an Ancient Aqueous Environment at Meridiani Planum, Mars,” Squyres writes:
“We cannot determine whether life was present or even possible in the waters at Meridiani, but it is clear that by the time the sedimentary rocks in Eagle crater were deposited, Mars and Earth had already gone down different environmental paths. Sample return of Meridiani rocks might well provide more certainty regarding whether life developed on Mars.”
by Paul Gilster | Dec 2, 2004 | Autonomy and Robotics
One of the fascinations of nanotechnology is its ability to shrink payloads. That means a lot when every kilogram you add to a probe makes it that much more costly to propel; at interstellar distances, nanotechnology means we might one day send tiny probes at a fraction of the vast cost of comparative giants like today’s Cassini Saturn orbiter.
One project that might deploy such methods in the near future is ANTS — Autonomous Nano Technology Swarm. The acronym is apt, because ANTS is all about collective, emergent intelligence of the sort that appears in insect colonies. What scientists at NASA’s Goddard Space Flight Center envision is a massive cluster of tiny probes that use artificial intelligence to explore the asteroid belt. Each probe, weighing perhaps 1 kilogram (2.2 pounds) would have its role — while a small number of them direct the exploration, perhaps 900 of the probes would proceed to do the work, with only a few returning to Earth with data.
One key factor here is redundancy; the mission succeeds even if a large number of individual probes are lost. ANTS could serve as a testbed for numerous technologies as it spreads computing intelligence across intelligent, networked spacecraft. In particular, computer autonomy would be critical to ensuring the success of the mission.
And if ANTS wouldn’t launch any time before 2020, it’s still under active discussion today, as witness the appearance of the University of Ulster’s Roy Sterritt, who addressed NASA scientists about his work on autonomy today at Goddard. From a University of Ulster press release:
Autonomic computing operates like the human body’s autonomic nervous system which self-manages biological systems. It regulates vital functions such as telling the heart how fast to beat and monitors and adjusts blood flow without conscious effort. Mr Sterritt’s research is aimed at developing computer systems that would work in the same way without requiring constant human intervention.
Mike Hinchey, director of NASA’s Software Engineering Laboratory, said: “Autonomic computing research has been identified by NASA as having potential to contribute to their goals of autonomy and cost reduction in future space exploration missions… The [ANTS] mission is viewed as the prototype for how many future unmanned missions will be developed and how future space exploration will exploit autonomous and autonomic behaviour.”
NASA information about the ANTS mission can be found here.
