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Side Note: The two images shown above are mere crop outs from ESA’s recent hit: The 9 Billion Pixel Image of 84 Million Stars. These two focus on the bright center of the image for the purpose of highlighting what a peak at 84,000,000 stars looks like.
Astronomers at the European Southern Observatory’s Paranal Observatory in Chile have released a breathtaking new photograph showing the central area of our Milky Way galaxy. The photograph shows a whopping 84 million stars in an image measuring 108500×81500, which contains nearly 9 billion pixels.
It’s actually a composite of thousands of individual photographs shot with the observatory’s VISTA survey telescope, the same camera that captured the amazing 55-hour exposure. Three different infrared filters were used to capture the different details present in the final image.
The VISTA’s camera is sensitive to infrared light, which allows its vision to pierce through much of the space dust that blocks the view of ordinary optical telescope/camera systems.
Fermi bubbles are burps from a star-eating black hole
Last year, astronomers analysing data from Fermi Gamma Ray Telescope made an extraordinary announcement: two giant bubbles emanating from the centre of the galaxy, stretching some 20,000 light years above and below the galactic plane. Today, scientists from The University of Hong Kong say the bubbles are the remnants of stars that have been eaten by the supermassive black hole at the centre of the galaxy.Our galaxy’s supermassive black hole is huge (4 million times more massive than the Sun), and a star falls into it every 1000 years or so. When this happens, part of the star is devoured by the black hole, while the rest is burped back out into space in the form of high energy protons that heat up the gas and dust surrounding the black hole creating an expanding bubble of high energy electrons.
This cannot expand far in the plane of the galaxy where it is absorbed. But the electrons can travel far into the space above and below the galactic plane, creating the gamma ray bubbles seen by Fermi. This explains why the edge of the bubble is so well defined. But it also explains another of the great puzzles that astronomers are sweating over: the strange energy distribution of cosmic rays.
It’s easy to imagine that higher energy cosmic rays ought to be rarer than lower energy ones. But when astronomers plot the number of cosmic rays against energy, there are far more high energy ones than there ought to be. These form a ‘knee’ in the graph, hence the name of the problem. The new model explains this knee: the extra high energy cosmic rays must be protons created during this star-eating process that have made their way to Earth. So it is the sheer size and energy of the black hole burp that generates the extra high energy protons in the spectrum.
Ref: arxiv.org/abs/1109.6087: “Fermi Bubbles as a Result of Star Capture in the Galactic Center”
A new study suggests the Milky Way doesn’t need a makeover: It’s already just about perfect.
Astronomers base that assertion on their discovery of a vast section of a spiral, star-forming arm at the Milky Way’s outskirts. The finding suggests that the galaxy is a rare beauty with an uncommon symmetry — one half of the Milky Way is essentially the mirror image of the other half.
Thomas Dame and Patrick Thaddeus of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts say the structure they’ve discovered is most likely the outer extension of the Scutum-Centaurus arm from the inner galaxy. The finding suggests that Scutum-Centaurus wraps all the way around the Milky Way, making it a symmetric counterpart to the galaxy’s other major star-forming arm, Perseus.
The two arms appear to extend from opposite ends of the galaxy’s central, bar-shaped cluster of stars, each winding around the galaxy, the researchers note in an upcoming issue of Astrophysical Journal Letters.
Image: A newly discovered star-forming arm at the fringes of the Milky Way may be a vast, outer extension of the arm Scutum-Centaurus. The finding suggests that the Milky Way has a rare symmetry, with one half of the galaxy the mirror image of the other half. (T. Dame/Robert Hurt)