AstroSpace Update – December 2009
AstroSpace Update
December 2009
Gathered by Don Lynn from NASA and other sources
Cassini (Saturn mission), using its radar on Titan, has observed seasonal changes in the surface that appear to be caused by drying up of the lakes of liquid methane. The reflectivity of the lakes changed (toward that seen in dry lake beds) and the shorelines changed. The most probable reason for this is that the lakes are evaporating as the season changes. Calculations showed that the liquid level probably dropped about a yard in an Earth year. A Titan year is 29 Earth years, so seasons change much more slowly there.
Spitzer (infrared space telescope) has found a huge doughnut-shaped (torus) ring about Saturn, much larger, thicker and tilted than the other rings. The moon Phoebe lies within the rings, and is probably ejecting the material that forms the ring when it is struck by meteorites. Phoebe is the most distant moon (from Saturn) of substantial size. The ring is composed of ice and dust particles, and is quite tenuous. The dark material covering about half of the moon Iapetus could possibly be dust from the newly discovered ring that drifted inward toward the planet and collided with Iapetus. Phoebe and the ring orbit retrograde, that is, in the opposite direction from the other major moons. Though the ring stood out in infrared, it is so dim in visible light that it has never been detected.
IBEX is a spacecraft that measures neutral particles that originate just beyond the planets of our solar system, where the stellar wind hits the interstellar medium. This area has been penetrated by only the 2 Voyager spacecraft, but IBEX maps it remotely, from its position near Earth. The first map of this stellar wind boundary has just been released, and it shows a huge ribbon of particle emission. Both Voyagers missed the ribbon, so did not hint at its existence. It is unknown what produced the ribbon. The direction of the ribbon is perpendicular to the magnetic field of the Milky Way, and this may be significant in explaining it.
Cassini also has an instrument that detects neutral particles (and also charged particles) from the stellar wind boundary, and its first map of this region was also just released. It had long been assumed that this boundary region would be comet shaped, a result of the solar system’s motion through the interstellar medium; ahead of motion would be rounded, with a tail streaming behind the direction of motion. But the map from Cassini shows it to be more of a spherical bubble. This implies that the pressure of the stellar wind or the strength of the Sun’s magnetic field control the shape of the boundary, not the pressure of the interstellar medium against the moving solar system.
Spirit (Mars rover) has been stuck in soft soil since April 23, when it broke through a hard crust covering talcum-like material. After extensive testing of alternative moves, using test rovers here on Earth, a plan to try to free Spirit has been approved. Steering of wheels has begun and a drive attempt is scheduled for November 17. The first move will be back the direction from which the rover came. Rover controllers are not at all sure the attempt will succeed. Even if successful, it may take many weeks. Efforts to free Spirit may last until February, when a mission review is scheduled. The current state of the solar panels is such that Spirit should endure the next Martian winter, even if it does not move to a more sunlight-optimized position. Of course winds can either add or remove dust from the panels and change that state.
Opportunity (the other Mars rover) found another meteorite less than half a mile from the last one, which was found in July. From the appearance and proximity, it probably broke off the same meteoroid body and fell the same time. The previous meteorite was determined to be quite old, falling perhaps 3 billion years ago. 2 weeks later the rover found yet another meteorite, its 4th.
LCROSS (lunar impact mission) –The LCROSS rocket body impacted Cabeus Crater on October 9, followed about 4 minutes later by the spacecraft impacting, as planned. The plume from the rocket impact fell back to the lunar surface in a matter of minutes. The plume was composed of 2 parts: one upward, and a curtain that spread outward. Only the upward part reached sunlight, and therefore became visible in ordinary light. The entire plume was visible in infrared wavelengths. The crater floor was heated by the rocket impact from its normal temperature of minus 380° F. to about 1300°. Preliminary results show that the LCROSS spectrometers definitely detected water in infrared and hydroxyl (a break-down product from water) in ultraviolet in the plume (both parts) of the first impact. Also detected were sodium and carbon dioxide. Further analysis is expected to identify other materials. Determining the total water displaced by the impact will require more work, but it has been determined that about 25 gallons were present in the part of the plume analyzed by the infrared spectrometer. This amount of water points toward the impact hitting ice (as opposed to vapor or liquid water), but further analysis will be done to confirm this. As hypothesized, the permanently shadowed regions of polar craters have now been shown to trap and preserve water and other material.
Fermi (gamma-ray space telescope) has completed 1 year of operation and has observed over 1000 discrete sources of gamma rays, 5 times the number previously known. Nearly half of these have been identified with objects known from other wavelengths of light. The most common sources are blazars, with substantial numbers of pulsars, and a few binary stars involving a neutron star. In May, Fermi observed a short gamma-ray burst (GRB) later found to be 7.3 billion light-years away. Since the burst contained a very high energy gamma-ray photon, it was an opportunity to verify one aspect of Einstein’s Relativity. Some competing theories predict that high-energy gamma ray photons should travel slightly slower than low-energy ones. Fermi’s observations showed essentially no difference in speed for the high-energy ray. Fermi has also observed 3 record-setting GRBs: the highest ejection speed of material in a burst, the highest energy gamma ray photon in a burst, and the greatest total energy in a burst.
Most distant object – Back in June I reported the discovery of a GRB that was found to be the most distant object every seen. Further observations and analysis have shown: The total energy was above average for a GRB, but not nearly a record; in radio light, the afterglow of the burst remained visible for over 2 months; the burst was the result of a large, but not monster, star ending its life in a supernova; this was proof that large stars existed this early after the Big Bang (the light left there only 630 million years into the life of the Universe), which had been long assumed, but not proven; the blast was nearly spherical and expanded into tenuous and relatively uniform gas.
White dwarfs are the remnants of less massive stars that have nuclearly fused all their fuel. More massive stars explode as supernovas when they run out of fuel. Theorists have long predicted that less massive white dwarfs form when they run out of hydrogen and helium as fuel, while slightly more massive stars would be able to ignite carbon also as fuel, which should produce much oxygen and neon as “ash”. But astronomers have never found the predicted oxygen-rich white dwarfs, until now. A search of data from the Sloan Digital Sky Survey produced 2 oxygen-rich white dwarfs. Some theorists had claimed that the oxygen of such stars would be trapped in the core, and so would not show up in spectra of the surface. But the fact that such stars are now known to exist requires theorists to explain how oxygen moves up to the surface, at least in some cases. It has been proposed that only stars near the mass limit above which they go supernova would be able to expose the oxygen.
New type of supernova – It is known that a Type Ia supernova occurs when a companion star dumps enough hydrogen onto a white dwarf star until it explodes. Some theorists have pointed out that some stars would dump helium, not hydrogen, onto their companion white dwarf. Then the explosion should be about 10 times less bright, and 10 times quicker in rising to peak brightness and then fading. Some theorists have dubbed this a Type .Ia supernova (point one a). A search of old supernova data produced one that fits this description, 2002bj. The spectra taken 7 years ago also fit the predictions. This type of supernova should not be powerful enough to form a neutron star. On the other hand, it is 1000 times more powerful than an ordinary nova.
Yet another – It is known that a Type II supernova occurs when a very massive star runs out of nuclear fuels, having produced an iron core, the heaviest “ash” possible from nuclear fusion. With no power source supplying the energy that supports the star against gravity, the core collapses and the outer parts explode. Theorists have proposed that extremely massive stars should have their cores collapse by a different mechanism before fusion fuel runs out: the supporting energy, in the form of light, can become unstable when photons break into electron-positron pairs. A recent paper announces that 5 supernovas have been found that fit the predictions for this “pair instability” mechanism as far as peak brightness (very bright in ultraviolet) and longevity of the rise and fading. Yet another type of supernova has now been found. Based on the number found, it was estimated that less than 1 in 10,000 Type II supernovas are of this new type.
Cassiopeia A is the remnant of a supernova that occurred over 300 years ago, but went unnoticed. It was long expected that there should be a neutron star near the center of the nebulosity, the remainder of the star that exploded. A possible candidate was found in 1999. New observations by Chandra (X-ray space telescope) have shown conclusively that this candidate is indeed a neutron star. No other object could give off the array of X-rays seen. But the observations revealed a new mystery: the neutron star has a carbon atmosphere. Previously studied neutron stars have all had hydrogen atmospheres. Incidentally, neutron star atmospheres are only about 4 inches high, due to the extremely high surface gravity. One proposal is that the extreme heat (about 1 billion degrees) at the time a neutron star is formed fuses all the hydrogen into carbon. Now theorists have to explain how older neutron stars all accumulate a replacement hydrogen atmosphere.
Intermediate black hole – Though known black holes of stellar mass (roughly 10 times the Sun’s mass) and supermassive ones (millions or billions of times the Sun’s mass) at the centers of galaxies have now become common, black holes with intermediate mass are rare and not well verified. Observations of an ultraluminous X-ray source (ULX) in galaxy NGC 5408 have shown that it is probably an intermediate mass black hole. XMM-Newton (orbiting X-ray telescope) has detected quasi-periodic oscillations, that is, a nearly regular flickering, believed to be caused by hot gas in the accretion disk of material falling into a black hole. The flickering was slower and the X-rays brighter than that of a stellar mass black hole, both indicating a greater mass. The best estimate of its mass, made from a variety of observations, is between 1000 and 9000 times the Sun’s mass. It appears from further observations that a massive star is in close orbit about the black hole, dumping material into it.
Lithium (the element) – Astronomers have long known that the Sun and a few other stars have very low abundances of lithium, less than 1% of that found in the majority of stars. A study of the spectra of 500 nearby stars finally shed light on what makes the low-lithium stars different. The answer is planets. All the stars in the new study that are known to have planets also had low lithium abundance. Additionally, the study ruled out factors other than planets from correlating with low lithium. Most lithium in the Universe was produced in the Big Bang, and thus all stars should have roughly the same amount of lithium, at least when they form. That amount turns out to be the higher abundance observed. That means that the low-lithium stars have destroyed their original supply of the element. The mechanism by which forming or keeping planets destroys lithium is not known, but theorists are now feverishly working on it. The observational astronomers, on the other hand, are treating this as a new way to find planets: just observe stars with low lithium in their spectra.
Cosmic Microwave Background (CMB) is the leftover light from the time about 400,000 years after the Big Bang that the Universe cooled enough to become transparent. The QUaD telescope at the South Pole has been observing the polarization of the CMB, and the first analysis of the observations has been released. It confirms the previous CMB results from the WMAP satellite and others, this time matching the theoretical spectrum even more closely, due to reduced noise. The CMB could have been produced only by a Universe containing 5% ordinary matter (made of protons and neutrons), and about 25% non-ordinary matter (dark matter) and 70% energy (dark energy).
Planet formation – Infrared spectra of 88 very distant galaxies showed the signature of circumstellar dust disks, the material out of which planets are formed. The galaxies are too distant to see individual stars or the disks themselves, but the sum of all such disks in each galaxy shows up. Further work was suggested to determine the rates of planet formation over time. This is possible because the more distant galaxies are seen as they were farther back in time.
Cosmic rays are particles, including protons, moving with extremely high energy. The mechanism that accelerates particles to such high energy has been debated for about a century. One theory is that exploding stars (supernovas) and stellar winds accelerate such particles. To test this, a team of astronomers decided to measure the cosmic rays in M82, a galaxy known to have far more massive stars than our Milky Way has, and therefore has far more supernovas and stars with strong stellar winds. Unfortunately we can’t measure cosmic rays remotely, only when they strike our instruments. But cosmic rays interact with interstellar gas and produce gamma rays, which we can detect remotely. The VERITAS earth-bound gamma ray detector was used and it found the cosmic ray density in M82 is about 500 times that in the Milky Way. Thus the supernova/stellar wind theory is supported. It required about 2 years of exposure by VERITAS to detect M82.
Large Hadron Collider (world’s largest particle accelerator, in Switzerland) – A beam of charged particles was run around the Large Hadron Collider in the clockwise direction in late October. This is the first time particles have been thrust inside it since it was shut down due to a massive magnet failure during a test run in September 2008. For full operation, particles must also be sent counterclockwise, and then collided with the other beam. In early November, a bird dropped a piece of bread into an outdoor piece of the collider, which overheated parts and caused a shutdown of the collider. It was not running particles through it at the time. Officials say this latest incident will not delay further test runs, which are planned to achieve particle collision in December.
NASA competitions have been held for the last few years for those outside the organization to develop technology that is expected to be needed on future space missions. In October the annual Regolith Excavation Challenge was held. The idea was to make a robot with self-contained power source, weighing under 176 pounds, that could excavate and dump into a container over 330 pounds of simulated lunar soil within 30 minutes. No one had succeeded at this in the past 3 years, but this time 3 teams did, and split $750,000 in prizes. 1st prize went to an excavator that loaded 1103 pounds during its half hour.
From July to October, the Lunar Lander Challenge was held. To win, a rocket has to take off vertically, fly to a target and land, and take off again within 2.25 hrs and fly back to the starting point. No servicing of the rocket is allowed. Level 1 prizes require 1.5 minute flights over easy terrain, and Level 2 prizes require 3 minute flights over rocks and craters. One Level 1 prize was claimed last year. This year the remaining Level 1 and both Level 2 prizes were awarded to Masten Space Systems and Armadillo Aerospace companies, ending this competition. A total of $1.65 million was awarded this year.
In early November, the Space Elevator competition was held. Winners had to make a device that would climb a 3280-foot-long cable suspended vertically, using only power beamed to the device from the ground (lasers were used). A prize of $900,000 was offered for completing above 4.5 mph, and another of $1.1 million for exceeding 11.2 mph. In the previous 5 years of competition, no one had qualified for either prize, but this year a team from Seattle won the smaller prize. Next year, only the bigger prize will be offered.
Instant AstroSpace Updates
Cassini flew through the geyser plumes of Saturn’s moon Enceladus on November 2. Preliminary results are that good data and spectacular pictures resulted.
Rosetta (comet mission) made its final gravity slingshot by the Earth November 13 and headed toward putting a lander on Comet Churyumov-Garasimenko in 2014. It returned a terrific image of the crescent Earth.
A hardware problem known at launch of the planet finding spacecraft Kepler is taking considerable time to fix in software. This prevents the accuracy needed to find smaller planets (but larger ones have already been found), so small planet discoveries are now expected to begin in 2011.
Hayabusa (Japanese asteroid sample return mission) on its way back to Earth has suffered yet another failure, this time a breakdown of another of its 4 ion thrusters, leaving only 1 remaining. It is believed that voltage spikes are killing the thrusters, so controllers will do much analysis before turning on the last working thruster.
Mars Reconnaissance Orbiter has imaged the Mars Phoenix polar lander covered in dry-ice frost. Phoenix got too cold and dark to function November of last year, as expected.
Constituent gases in the atmospheres of exoplanets have been detected for the 2nd and 3rd exoplanets ever, and again they are carbon dioxide, water vapor, and methane. All are hot Jupiters (gas giant planets very close to their stars).
Results were announced of recent searches for exoplanets using HARPS, an extremely sensitive spectrograph at the European Southern Observatory in Chile. 32 more exoplanets were found, pushing the total known to 406.
Computer simulations of the atmosphere of the recently discovered rocky exoplanet COROT-7b show that it is so hot that rock vapor exists. Solid rock condenses at various altitudes, depending on composition, and falls as a pebble hail onto the surface, which is covered (on the star-facing side) with molten lava.
An asteroid estimated at only 23 feet across was discovered November 6 just hours before it passed about 9000 miles from Earth, the 3rd closest non-impact on record.
A cluster of galaxies discovered in infrared, then observed in visible light and X-rays, has been measured to be so distant that its light took 10.2 billion years to reach us, making it the farthest known galaxy cluster. More distant individual galaxies and quasars are known.
NASA and the European Space Agency have signed an agreement to jointly build and operate planned Mars orbiter and lander missions. This had been expected due to budget pressures on the space agencies.
Russia announced plans to build one more Soyuz spacecraft per year, and rent out 2 spaces on each of those extras to (rich) space tourists. It had been thought that the space tourism, at least on Soyuz vehicles, would be over when the Space Shuttles retire next year, and all Soyuz seats would be needed to take new crews to the International Space Station.
Further observations of the asteroid Apophis have refined our knowledge of its orbit and shown that it is extremely unlikely (1 chance in 250,000) to strike the Earth in 2036. But they also showed that the asteroid will return quite close to Earth in 2068, with a nearly equal (extremely unlikely) chance of striking our planet then. The possibility of collision in 2029 had already been ruled out.
The test of the Ares I-X rocket mentioned last month was a success, although there were problems with the parachutes that lower the booster to splashdown for reuse. Thrust oscillations, sometimes a problem with new rockets, were negligible.
