by Paul Gilster | Jun 14, 2007 | Exoplanetary Science |
My younger son Alec can be forgiven a certain amount of confusion over the term ‘Planet X.’ Back in the 1980s, I told him all about the marvelous Edgar G. Ulmer film The Man from Planet X, a favorite since my own childhood. Ulmer was a gifted director who is rarely talked about today (see his 1945 film Detour for a glimpse of just how gifted). And 1951’s The Man from Planet X was compelling in a way that few B movies of the era achieved, with an alien whose spooky presence has stuck with me ever since I first saw him on an old black-and-white set.
But then Alec encountered a different ‘Planet X’ in an astronomy class, learning that some astronomers had searched for a planet beyond Pluto, although at that point with notable lack of success. Planet X was supposed to account for various orbital oddities exhibited by Pluto and become emblematic of a fabulous, unknown place at the very edge of the system that was the ultimate catch for the next Clyde Tombaugh. I didn’t think it existed until Mike Brown came along.
Image: Actress Margaret Field approaches the alien vessel amidst a fine Scottish fog in Edgar G. Ulmer’s The Man from Planet X. Ulmer worked with the smallest of budgets but created suspense as much by what he didn’t show as what he did.
Brown, an astronomer at the California Institute of Technology, identified the world we’ve come to know as Eris, a place larger than Pluto and on an even more eccentric orbit well off the ecliptic. No wonder it took so long to find it. And just when we thought we had a real Planet X, my son was told that it wasn’t a planet at all. Oddly, finding an object larger than Pluto only reinforced the growing belief that Pluto itself was just one of many (perhaps hundreds, perhaps thousands) of large Kuiper Belt objects. The IAU made it official and now we have just eight planets.
The latest news about the demoted Planet X more or less makes the same point. New data from Brown and grad student Emily Schaller show that Eris is 27 percent more massive than Pluto. Says Brown:
“This was Pluto’s last chance to be the biggest thing found so far in the Kuiper belt. There was a possibility that Pluto and Eris were roughly the same size, but these new results show that it’s second place at best for Pluto.”
The data tell us that Eris is made up of ice and rock, thus similar to Pluto in composition. It’s bound to be a dark and lonely place, currently 97 AU from the Sun and sporting temperatures below -240 degrees Celsius. That orbit will eventually swing back around, highly elliptical as it is, to bring Eris within 38 AU, but right now it’s pretty much at aphelion, orbiting along with its moon Dysnomia in the outer dark. A fine, interesting object, but no longer fit to be declared a planet.
Sigh. The Man from Planet X has not, to my knowledge, made it onto DVD, but I managed to acquire, some ten years ago, a good videotape of it, and I was delighted to find that it has worn well over all the years. Sure, it’s schmaltzy and over-acted and it makes its points a little too heavily, but this is a B movie, remember? And the sets, the lighting, the fog over the Scottish moors where the odd glow of the alien craft can be seen at night, these are things that, to this day, put a chill up my spine.
Eris isn’t Planet X, but then we’re discovering plenty of worlds around other stars that should prove even more interesting. And as for the might-have-been Planet X, the new paper is Brown and Schaller, “The Mass of Dwarf Planet Eris,” Science Vol. 316, No. 5831 (June 15, 2007), p. 1585 (abstract available).
by Paul Gilster | Jun 13, 2007 | Deep Sky Astronomy & Telescopes |
Gamma-ray bursts (GRBs), those titanic explosions in distant galaxies that some consider to be the most powerful events since the Big Bang, can be more luminous than anything else in the universe, at least for a while. But their moment in the spotlight is brief, less than a second to as much as a few minutes, and questions about their origins abound. Astronomers expecting speeds close to the 300,000 km/s of light itself for the material exploding from these bursts have now been vindicated by measurements made at the European Southern Observatory’s La Silla facility.
Image: Light curve of the gamma-ray burst of 7 June 2006, GRB 060607A. The red dots are the data obtained with the REM telescope observing the afterglow (in the near-infrared H-band) of the burst from 73 seconds after the explosion. The blue line is a fit to the data, allowing the astronomers to determine the peak of the light curve and so, derive the velocity of the material. (c) ESO.
Space-to-ground coordination is needed to examine GRBs like the two under study, which were first detected by the Swift satellite and followed up by La Silla’s robotic Rapid-Eye Mount (REM) telescope on April 18, 2006 and again on June 7 of that year. The two bursts, some 9.3 and 11.5 billion light years away respectively, created an afterglow visible at optical and near-infrared wavelengths, the result of exploding material ramming into surrounding gas. Direct measurements of the velocity of the exploding material arrived at a value of 99.9997% of the speed of light.
“Matter is thus moving with a speed that is only different from that of light by three parts in a million,” says Stefano Covino, co-author of the study. “While single particles in the Universe can be accelerated to still larger velocities – i.e. much larger Lorentz factors – one has to realise that in the present cases, it is the equivalent of about 200 times the mass of the Earth that acquired this incredible speed.”
Longer-duration gamma-ray bursts like these are thought to be the result of the explosion of massive stars; shorter duration GRBs may originate in collisions between neutron stars and black holes. The paper is Molinari et al., “REM observations of GRB060418 and GRB060607A: the onset of the afterglow and the initial fireball Lorentz factor determination,” Astronomy & Astrophysics 469, L13-L16 (2007), with abstract available online.
by Paul Gilster | Jun 12, 2007 | Outer Solar System |
An underground ocean on Titan? The apparent detection of low frequency radio waves makes liquid water beneath the surface of the huge Saturnian moon a possibility, according to research led by Fernando Simoes (Centre d’Etudes Terrestres et Planetaires, Saint Maur, France). Simoes and team have been studying what New Scientist is describing as an ‘enigmatic radio signal’ that the European Space Agency’s Huygens probe detected as it descended to Titan’s surface in 2005.
The signal seems not dissimilar to what lightning produces on Earth, where low frequency signals bounce between the ground and the upper atmosphere, in the process attenuating some frequencies while enhancing others. But Titan’s surface seems to be a poor reflector, meaning there may be a better one below. Thus the talk of an ocean, although it’s just one candidate. “We do not need a subsurface ocean but require a subsurface reflector,” Simoes told New Scientist. “If a subsurface ocean exists, the solid-liquid interface would be a good reflector.”
Still in question is the possibility of extraneous vibrations within the radio instrument itself, although the team’s testing has so far failed to reveal any evidence of this. If a body of water is there, it’s probably deep, perhaps fifty kilometers down. A vast ocean rich in ammonia is an exciting prospect indeed, but waiting for future Cassini flybys is necessary for confirmation. If an ocean can be found by analyzing Titan’s behavior under the gravitational pull of Saturn, we’ll have yet more reason for astrobiologists to ponder the outer icy moons as abodes of life.
by Paul Gilster | Jun 12, 2007 | Exoplanetary Science |
Buy a commercial telescope today, equip it with a CCD detector, and you’re arming yourself to enter the exoplanet hunt. A CCD, or charge-coupled device, is a sensor that proves far more efficient than photographic film at capturing incoming light. It wasn’t so long ago that such tools were available only at large observatories, but no more. Today’s amateur can observe a planetary transit, sensing the slight dimming that the planet causes to the starlight as seen from Earth.
The trick is knowing when and where to look, and on that score, the Transitsearch network, often working with the American Association of Variable Star Observers, offers ephemeris and transit search results for stars thought to be candidates for such detections. For those new to the term, an ephermeris (pl. ephemerides) is a table plotting the position of celestial bodies. Look to Transitsearch for an example.
Greg Laughlin (UC Santa Cruz) noted this morning on the systemic site that he was overhauling the look and capabilities of Transitsearch. The new design isn’t fully functional yet, but the data are already flowing. Says Laughlin:
“The ephemerides are incrementally updated every ten minutes, and so the transit window column now has a much finer resolution. It gives a quick overview of which planets are transiting (or potentially transiting) right now.”
And is something more in the works? Laughlin notes that large radial velocity studies are usually accompanied by photometric observations made by the same team, thus keeping transit detections more or less in-house. “Ideally, we need to get an open-source dedicated radial velocity observatory up and running to really feed Transitsearch and the systemic backend, and we are looking at avenues to make this happen.” That’s an exciting concept indeed, and one we’ll follow with great interest as the number of detected exoplanets closes on 300.
by Paul Gilster | Jun 11, 2007 | Astrobiology and SETI |
I’m glad to see Universe Today‘s review of Michael Michaud’s new book Contact with Alien Civilizations: Our Hopes and Fears about Encountering Extraterrestrials (Springer, 2006), since I haven’t gotten to it yet despite a promise early in the year. Those hoping for a thorough analysis of the Drake Equation are in luck, since Michaud evidently tweaks every parameter to see what happens as a result. Many of the issues raised here are things we’ve kicked around on Centauri Dreams, as is apparent in this excerpt from the review:
Are we alone; does the universe revolve around our species; and, is everything in existence for the use of humans? As well, should humans be trying to contact aliens; with what urgency should we start populating outer space; and, how should we react to alien contact? As an example, what would we do if it came to our attention tomorrow that aliens were colonizing Mars? These questions about our actions, our purpose and ourselves serve hopefully, to make the reader delve a little deeper into their own existence.
Interesting question with regard to Mars, and one I’ve heard raised about interstellar nano-probes that might be considered a threat by any species becoming aware of their entry into an exoplanetary system. Clearly, issues of philosophy are engaged by any species contact scenario, with the problem that our only historical references all involve human behaviors that are inevitably generalized to predict how aliens will act. As I’m behind in my reading (a major understatement), I’d appreciate any thoughts from readers on what Michaud has to say.
