This is kind of cool. Astronomers using the Gemini and Keck observatories on Mauna Kea, Hawai’i have spotted clouds in the atmosphere of Saturn’s largest moon, Titan. This isn’t the first time clouds have been found; astronomers have also seen them at Titan’s south pole and reasoned that they were caused by solar heating of the polar region.
However, these new clouds were spotted in early 2004 at the mid-latitudes of the moon, and are not likely to be caused by solar heating. So, what could be driving the formation of cloudy features in Titan’s nitrogen atmosphere? One explanation could be something happening on the surface that affects the atmosphere, like methane geysers or volcanoes that spout icy slush instead of lava (called cryovolcanism). It’s also possible that these features are being driven by some sort of changes in the global winds that circulate in the upper parts of Titan’s atmospheric blanket. The good news is that astronomers have a reporter “on site” in the form of the Cassini-Huygens mission. It’s likely the spacecraft has also recorded observations of these clouds and we may hear more about them from Cassini mission scientists. Incidentally, those researchers are gearing up for a big event on Christmas Day, 2004: the launch of the Huygens probe toward Titan, and an eventual surface landing sometime in the middle of January. Keep an eye out for more Titan news in the coming days and weeks!
Courtesy Space Telescope Science Institute, Chandra X-Ray Center,Spitzer Space Telescope
A somewhat drab-looking object in optical telescopes is all that’s left of a supernova that flared in 1604 and dubbed “Kepler’s Supernova.” However, the optical view of the universe only shows us a tiny part of this object’s story. The Chandra X-Ray Observatory, the Spitzer Space Telescope, and the Hubble Space Telescope show how the catastrophic death of a star looks in visible, x-ray, and infrared wavelengths of light. Here the story the three observatories are telling:
The combined image unveils a bubble-shaped shroud of gas and dust that is 14 light-years wide and is expanding at 4 million miles per hour (2,000 kilometers per second). Observations from each telescope highlight distinct features of the supernova remnant, a fast-moving shell of iron-rich material from the exploded star, surrounded by an expanding shock wave that is sweeping up interstellar gas and dust.
Each color in this image represents a different region of the electromagnetic spectrum, from X-rays to infrared light. These diverse colors are shown in the panel of photographs below the composite image. The X-ray and infrared data cannot be seen with the human eye. By color-coding those data and combining them with Hubble’s visible-light view, astronomers are presenting a more complete picture of the supernova remnant.
Visible-light images from the Hubble telescope’s Advanced Camera for Surveys [colored yellow] reveal where the supernova shock wave is slamming into the densest regions of surrounding gas.
The bright glowing knots are dense clumps from instabilities that form behind the shock wave. The Hubble data also show thin filaments of gas that look like rippled sheets seen edge-on. These filaments reveal where the shock wave is encountering lower-density, more uniform interstellar material.
The Spitzer telescope shows microscopic dust particles [colored red] that have been heated by the supernova shock wave. The dust re-radiates the shock wave’s energy as infrared light. The Spitzer data are brightest in the regions surrounding those seen in detail by the Hubble telescope.
The Chandra X-ray data show regions of very hot gas, and extremely high-energy particles. The hottest gas (higher-energy X-rays, colored blue) is located primarily in the regions directly behind the shock front. These regions also show up in the Hubble observations, and also align with the faint rim of glowing material seen in the Spitzer data. The X-rays from the region on the lower left (colored blue) may be dominated by extremely high-energy electrons that were produced by the shock wave and are radiating at radio through X-ray wavelengths as they spiral in the intensified magnetic field behind the shock front. Cooler X-ray gas (lower-energy X-rays, colored green) resides in a thick interior shell and marks the location of heated material expelled from the exploded star.
Kepler’s supernova, the last such object seen to explode in our Milky Way galaxy, resides about 13,000 light-years away in the constellation Ophiuchus.
