Data from NASA’s Cassini spacecraft tie a shift in seasonal sunlight to a wholesale reversal, at unexpected altitudes, in the circulation of the atmosphere of Saturn’s moon Titan. At the south pole, the data show definitive evidence for sinking air where it was upwelling earlier in the mission. So the key to circulation in the atmosphere of Saturn’s moon Titan turned out to be a certain slant of light. The paper was published today in the journal Nature.
“Cassini’s up-close observations are likely the only ones we’ll have in our lifetime of a transition like this in action,” said Nick Teanby, the study’s lead author who is based at the University of Bristol, England, and is a Cassini team associate. “It’s extremely exciting to s
ee such rapid changes on a body that usually changes so slowly and has a ‘year’ that is the equivalent of nearly 30 Earth years.”
In our solar system, only Earth, Venus, Mars and Titan have both a solid surface and a substantial atmosphere – providing natural laboratories for exploring climate processes. “Understanding Titan’s atmosphere gives us clues for understanding our own complex atmosphere,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Some of the complexity in both places arises from the interplay of atmospheric circulation and chemistry.”
A jet of X-rays from a supermassive black hole 12.4 billion light years from Earth has been detected by NASA’s Chandra X-ray Observatory. This is the most distant X-ray jet ever observed and gives astronomers a glimpse into the explosive activity associated with the growth of supermassive black holes in the early universe.
The jet was produced by a quasar named GB 1428+4217, or GB 1428 for short. Giant black holes at the centers of galaxies can pull in matter at a rapid rate producing the quasar phenomenon. The energy released as particles fall toward the black hole generates intense radiation and powerful beams of high-energy particles that blast away from the black hole at nearly the speed of light. These particle beams can interact with magnetic fields or ambient photons to produce jets of radiation.
“We’re excited about this result not just because it’s a record holder, but because very few X-ray jets are known in the early universe,” said Teddy Cheung of the National Academy of Sciences, resident at the Naval Research Laboratory in Washington DC, and lead author of the paper describing these results.
Astronomers have used the Hobby-Eberly Telescope at The University of Texas at Austin’s McDonald Observatory to measure the mass of what may be the most massive black hole yet — 17 billion Suns — in galaxy NGC 1277. The unusual black hole makes up 14 percent of its galaxy’s mass, rather than the usual 0.1 percent. This galaxy and several more in the same study could change theories of how black holes and galaxies form and evolve. The work will appear in the journal Nature on Nov. 29.
NGC 1277 lies 220 million light-years away in the constellation Perseus. The galaxy is only ten percent the size and mass of our own Milky Way. Despite NGC 1277’s diminutive size, the black hole at its heart is more than 11 times as wide as Neptune’s orbit around the Sun.
“This is a really oddball galaxy,” said team member Karl Gebhardt of The University of Texas at Austin. “It’s almost all black hole. This could be the first object in a new class of galaxy-black hole systems.” Furthermore, the most massive black holes have been seen in giant blobby galaxies called “ellipticals,” but this one is seen in a relatively small lens-shaped galaxy (in astronomical jargon, a “lenticular galaxy”).
An international team led by researchers from the University of Warwick and Oxford University is now dealing with unexpected results of an experiment with strongly heated graphite (up to 17,000 degrees Kelvin). The findings may pose a new problem for physicists working in laser-driven nuclear fusion and may also lead astrophysicists to revise our understanding of the life cycle of giant planets and stars.
The researchers were attempting to get a better understanding about how energy is shared between the different species of matter, especially, how it is transferred from strongly heated electrons to the heavy ionic cores of atoms that have been left cool. The difference in temperatures between the hot electrons and cooler ions should level out quickly as the electrons interact with the ions; thus, the time it takes to reach a common temperature is a good measure of the interaction strength between the two. This interaction also defines, for instance, how heat or radiation is transported from the inside of a planet or star to its surface and, thus, planetary and stellar evolution. The process is also essential for nuclear fusion where the electrons are heated by fusion products but the ions need to be hot for more fusion to occur.
Their more precise experiment in fact shows that the equilibration of the temperatures for hot electron and cool ions is actually three times slower than previous measurements have shown and more than ten times slower than the mathematical model predicts. This means that the basic process of electron-ion interaction is only poorly understood.
Using ESA’s Herschel space observatory, astronomers have discovered vast comet belts surrounding two nearby planetary systems known to host only Earth-to-Neptune-mass worlds. The comet reservoirs could have delivered life-giving oceans to the innermost planets. Interestingly, however, there is no evidence for giant Jupiter- or Saturn-mass planets in either system.
In a previous Herschel study, scientists found that the dusty belt surrounding nearby star Fomalhaut must be maintained by collisions between comets. In the new Herschel study, two more nearby planetary systems – GJ 581 and 61 Vir – have been found to host vast amounts of cometary debris.
Herschel detected the signatures of cold dust at 200ºC below freezing, in quantities that mean these systems must have at least 10 times more comets than in our own Solar System’s Kuiper Belt.
The gravitational interplay between Jupiter and Saturn in our own Solar System is thought to have been responsible for disrupting a once highly populated Kuiper Belt, sending a deluge of comets towards the inner planets in a cataclysmic event that lasted several million years.
An international team of researchers from the National Astronomical Observatory of Japan (NAOJ) and the Japanese universities of Kobe, Hyogo, and Saitama used the Subaru Telescope to capture a clear image of the protoplanetary disk of the star UX Tauri A. The team’s subsequent, detailed study of the disk’s characteristics suggests that its dust particles are large in size and non-spherical in shape. This exciting result shows that these dust grains are colliding with and adhering to each other, a process that will lead to their eventual formation into planets.
The team made a detailed study of UX Tau A in the near-infrared wavelengths. They measured the polarization (Note 2) of infrared light to find out the distribution of the dust particles that scattered the infrared light. Polarized light reflected from dust particles gives important information about planetary formation in disks. Even though dust particles only make up a tiny fraction of the protoplanetary disk, they can develop into planetesimals (solid objects less than a kilometer in diameter), and eventually, planets.
You could call this “Pac-Man, the Sequel.” Scientists with NASA’s Cassini mission have spotted a second feature shaped like the 1980s video game icon in the Saturn system, this time on the moon Tethys. (The first was found on Mimas in 2010). The pattern appears in thermal data obtained by Cassini’s composite infrared spectrometer, with warmer areas making up the Pac-Man shape.
“Finding a second Pac-Man in the Saturn system tells us that the processes creating these Pac-Men are more widespread than previously thought,” said Carly Howett, the lead author of a paper recently released online in the journal Icarus. “The Saturn system – and even the Jupiter system – could turn out to be a veritable arcade of these characters.”
Scientists theorize that the Pac-Man thermal shape on the Saturnian moons occurs because of the way high-energy electrons bombard low latitudes on the side of the moon that faces forward as it orbits around Saturn. The bombardment turns that part of the fluffy surface into hard-packed ice. As a result, the altered surface does not heat as rapidly in the sunshine or cool down as quickly at night as the rest of the surface, similar to how a boardwalk at the beach feels cooler during the day but warmer at night than the nearby sand. Finding another Pac-Man on Tethys confirms that high-energy electrons can dramatically alter the surface of an icy moon. Also, because the altered region on Tethys, unlike on Mimas, is also bombarded by icy particles from Enceladus’ plumes, it implies the surface alteration is occurring more quickly than its recoating by plume particles.