Cosmic Diary 11 Dec 2017, 17:43 UTC A Piece of Mars: Look at the alignment of the ~100 m dunes in this 713×750 m (0.44×0.47 mi) scene. How do dunes form in such straight lines? And why don’t they always do that? It’s likely that these dunes were once long ridges stretching from the lower right to upper left. The shape of the slip faces suggests they’re formed from two winds that blow from similar directions, both of which push sand toward the upper left. To stay stable, this sort of dune needs a constant influx of sand from upwind (from the lower right), but if that flow of incoming sand lessened, then a long dune would be forced to break up into a series of smaller dunes. That may be what’s happened here. Check out the whole image, and you’ll see other long ridges that haven’t yet broke up into smaller dunes.
Starts With a Bang! 11 Dec 2017, 15:01 UTC Einstein’s theory of General Relativity has withstood every test for more than a century. From the bending of starlight to orbital decay, Einstein’s predictions for spacetime’s behavior have never failed. Since 2015, the final stages of black hole and neutron star inspirals and mergers have been observed directly. The holy grail of black hole mergers, however, would be an inspiraling system that we could monitor consistently throughout the decay process, culminating in a merger.
Astroblog 11 Dec 2017, 13:26 UTC The northern horizon at 4:00 am ACDST as seen from Adelaide on Thursday December 14. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at a similar latitude and the equivalent local time. (click to embiggen).Don't forget the Geminid meteor shower peaks this week on the morning of Thursday the 14th. This year viewing conditions are good.Full details, viewing hints and estimated rates are on my Geminid Meteor Shower Page.
Sky Lights 11 Dec 2017, 07:01 UTC Most meteor showers disappoint observers, but the Geminids almost always provide a good show. Rates at the peak (this year Dec 13–14 06:30 UT) have been as high as 120 meteors/hour, but you’ll need dark skies to see the faint ones. From a light polluted city you’ll catch only the bright fireballs — maybe one every 30 minutes. However, astronomers say the Geminid rate is gradually increasing as Jupiter’s gravity drags the debris stream’s orbit closer to Earth. And this year, the late-rising Moon won’t interfere.
Astro Watch 10 Dec 2017, 21:27 UTC A G1-class (minor) geomagnetic storm may hit the Earth on Monday or Tuesday, according to National Oceanic and Atmospheric Administration (NOAA). This is due to a fast-moving solar wind that is expected to reach our planet around December 11.As a result of the upcoming minor geomagnetic storm, auroras could be visible around Earth's poles and weak power grid fluctuations could occur. Such storm could also have minor impact on satellite operations.In general, geomagnetic storms can increase the density and distribution of density in the upper atmosphere, causing extra drag on satellites in low-earth orbit. The local heating also creates strong horizontal variations in the in the ionospheric density that can modify the path of radio signals and create errors in the positioning information provided by GPS. While the storms create beautiful aurora, they also can disrupt navigation systems such as the Global Navigation Satellite System (GNSS) and create harmful geomagnetic induced currents in the power grid and pipelines.Fast coronal hole high speed streams (CH HSSs) can impact Earth’s magnetosphere enough to cause periods of geomagnetic storming to the G1-G2 levels; although rarer cases of stronger storming may also occur. The larger and more expansive coronal holes can often be a ...
Astrobiology Magazine 10 Dec 2017, 17:00 UTC Microbes in Antarctica have a previously unknown ability to scavenge hydrogen, carbon monoxide and carbon dioxide from the air to stay alive in the extreme conditions. The find has implications for the search for life on other planets, suggesting extra-terrestrial microbes could also rely on trace atmospheric gases for survival.
The Daily Galaxy
Behemoth the Size of 800 Million Suns--"Discovery a Clue to How Black Holes Grew So Big So Fast In the Early Universe"10 Dec 2017, 16:52 UTC Astronomers have profound questions about the first billion years of the universe: what burned off the fog of the cosmic dark ages? Was it the formation of stars or supermassive black holes, or both? And how did those black holes grow so big in so little time? The answer may have arrived in the form of a monster the size of 800 million suns, the the most-distant supermassive black hole ever observed. A team of astronomers led by Carnegie’s Eduardo Bañados used Carnegie’s Magellan telescopes to discover the most-distant supermassive black hole ever observed. It resides in a luminous quasar and its light reaches us from when the universe was only 5 percent of its current age—just 690 million years after the Big Bang. “That night I couldn’t even sleep,” he said about the discovery. Quasars (illustrated below) are tremendously bright objects comprised of enormous black holes accreting matter at the centers of massive galaxies. This newly discovered black hole has a mass that is 800 million times the mass of our Sun. “Gathering all this mass in fewer than 690 million years is an enormous challenge for theories of supermassive black hole growth,” Bañados explained. To grow black holes ...
SPACE.com 10 Dec 2017, 13:24 UTC