Artists' conception of the Kepler-10 system. (Credit: NASA/Ames/JPL/CALTech).
15.03.11: A Borderline Brown Dwarf.
Oh Be A Fine Girl/Guy Kiss Me Now… the mnemonic for stellar classification running from hottest to coldest has been long overdue overhaul, as brown dwarf classes L, T, and now Y have been placed on the cool end of the scale. And in the past month, a paper by Kevin Luhman and colleges at Pennsylvania State University have reported what may be the coolest brown dwarf known.
Astronomers may have found a cosmological missing link in the realm of galactic evolution. The early universe was a crowded place; galaxy mergers must have been much more common in the primeval universe than they are today. But studying those early collisions has been problematic; the immense distances involved over time and space mean that resolving clusters and individual stars are out of the question. Now, a team from the University of Western Ontario led by Sara Gallagher has published a study of an object which may serve as a "living fossil" of those early times; Hickson Compact Group 31. A cluster of irregular galaxies "only" 166 million light years away in the constellation Eridanus, this merger has somehow escaped coalescence over 10 billion years of cosmic history to just begin merging. "Because HCG 31 is so nearby," Gallagher notes, "we can indentify individual star clusters." In fact, two main components of HCG 31 approach visual magnitude +13 and have been snared by amateur instruments. HCG 31 is approximately 75,000 light years in diameter, and will probably one day form one huge elliptical galaxy. To conduct this study, Gallagher utilized time and instruments that spanned the spectrum, from Hubble in visible light to Spitzer in infrared to Galex and Swift in the ultraviolet. It is amazing that astronomers now have such capabilities in their bag of tricks at their ready disposal!
19.04.10- The Rise of WISE.
NASA has a new orbiting infrared eye on the universe. WISE, the Wide-field Infrared Space Explorer, is now open for business, and returning some fairly cool images. Launched out of Vandenberg AFB on December 12th of last year, the telescope is now parked in a sun-synchronous orbit at an inclination of 97.5° degrees. This allows WISE to keep its solar panels in a sunward orientation, while the telescope itself looks off at right angles to the Sun. This will also allow it to image continuous swaths of the sky as it orbits the Earth. WISE sports a 16" 40cm gold-plated mirror (talk about tricked out!) optimized for IR work and will conduct an all-sky survey with an unprecedented resolution across its 47 arc minute field of view. A successor to the IRAS and Spitzer, which ran out of coolant last year, WISE has an on-board supply on frozen hydrogen that should sustain it for a 10 month mission. To perform its mission, WISE must be cooled to -430° F, or about 15 Kelvins. It will also narrow in on possible targets for the James Webb Space telescope to be launched in 2014. JWST is much touted as the "successor to Hubble" but will actually be optimized for work in the infrared as well. IR work is virtually impossible to do from ground based telescopes, due to the absorption of IR wavelengths by water vapor in our atmosphere. Already, WISE has discovered comets, Near Earth objects, and opened a new window on nebulae and star formation… more discoveries to come!
17.04.10- The Case of the Vanishing Moon: Solved.
Since its discovery by Giovanni Cassini in 1671, Saturn's moon Iapetus has confounded astronomers. Even early on, observers knew something curious was going on with this far off moon; Iapetus varies in brightness between +10 & +12th magnitude as it orbits the ringed planet, nearly vanishing from sight for half its orbit! Late last year, NASA's Cassini spacecraft and the Spitzer Space Infrared Telescope fingered the culprit; a tenuous outer ring of material now known as the Phoebe Ring that is raining down material on its surface. Like our own Moon, Iapetus is tidally locked in its 79 day orbit. As a consequence, the leading edge plows through this dusty stream of debris. This also causes sunlight to warm and sublimate icy material on the leading side, which streams and re-condenses on the trailing end. This nicely explains the sharply defined and complex boundary seen between the two hemispheres. Alas, no monolith as depicted in Clarke's original 2001 novel adaptation. .. but perhaps a fine site one day for a cosmic ski resort!
Move over Europa ; yet another moon may harbor a subsurface sea. Saturn's moon Enceladus has been inching its way up the charts as of late as a candidate world for extraterrestrial life. Barely 300 miles in diameter, the tiny world is repeatedly flexed by Saturn's gravity and an increased orbital eccentricity pumped up by the nearby moon Dione. This has caused the tiger-striped surface seen by the Cassini space probe, a surface that shows evidence of repeated fissuring and freezing that almost certainly covers a liquid interior. In fact, Cassini has caught several of the geysers in the act during four recent flybys of the moon. One flyby was close enough that Cassini actually flew through a geyser plume! Activity on Enceladus is now known to almost exclusively contribute to Saturn's E ring…and recently, a much broader ring system has been revealed by the Spitzer space telescope. Sodium chloride has also been detected in the E ring, presumably from the interior of Enceladus…clearly, the Saturnian system is a dynamic place warranting more scrutiny. Let's hope that NASA approves Cassini's seven year mission extension!