Dark Sky Island
The gorgeous Isle of Sark, the smallest self-governing island in Europe, is located in the English channel 130 miles off the southern English coast. In January 2011 it became the world’s first “Dark Sky island” by controlling light pollution. The island’s single electricity source is an oil-fired power station, and there are no cars, streetlights or even paved roads: you can only get around by bike, horse, carriage or tractor-drawn bus. Due to the lack of light pollution, the Milky Way stretches gloriously overhead—from horizon to horizon across the pristine black sky.
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.
Black hole naps amidst stellar chaos
Nearly a decade ago, NASA’s Chandra X-ray Observatory caught signs of what appeared to be a black hole snacking on gas at the middle of the nearby Sculptor galaxy. Now, NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), which sees higher-energy X-ray light, has taken a peek and found the black hole asleep.
“Our results imply that the black hole went dormant in the past 10 years,” said Bret Lehmer of the Johns Hopkins University, Baltimore, and NASA’s Goddard Space Flight Center, Greenbelt, Md. “Periodic observations with both Chandra and NuSTAR should tell us unambiguously if the black hole wakes up again. If this happens in the next few years, we hope to be watching.” Lehmer is lead author of a new study detailing the findings in the Astrophysical Journal.
The slumbering black hole is about 5 million times the mass of our sun. It lies at the center of the Sculptor galaxy, also known as NGC 253, a so-called starburst galaxy actively giving birth to new stars. At 13 million light-years away, this is one of the closest starbursts to our own galaxy, the Milky Way.
“Black holes feed off surrounding accretion disks of material. When they run out of this fuel, they go dormant,” said co-author Ann Hornschemeier of Goddard. “NGC 253 is somewhat unusual because the giant black hole is asleep in the midst of tremendous star-forming activity all around it.”
Chandra first observed signs of what appeared to be a feeding supermassive black hole at the heart of the Sculptor galaxy in 2003. As material spirals into a black hole, it heats up to tens of millions of degrees and glows in X-ray light that telescopes like Chandra and NuSTAR can see.
Then, in September and November of 2012, Chandra and NuSTAR observed the same region simultaneously. The NuSTAR observations — the first-ever to detect focused, high-energy X-ray light from the region — allowed the researchers to say conclusively that the black hole is not accreting material.
In other words, the black hole seems to have fallen asleep. Another possibility is that the black hole was not actually awake 10 years ago, and Chandra observed a different source of X-rays. Future observations with both telescopes may solve the puzzle.
Image credit: NASA/JPL-Caltech/JHU
The Milky Way above a sea of clouds
Image credit: R. Bertero
The Milky Way and Sagittarius constellation
Image credit: Terrence Dickinson
An image of the region of sky around M74, the “Phantom Galaxy”, from the Digitized Sky Survey 2. The field-of-view is approximately 2.8 x 2.8 degrees.
Credit: NASA/ ESA/ Digitized Sky Survey 2/ Davide De Martin (ESA/Hubble)
Left: A GALEX ultraviolet image of the interacting galaxies M81 and M82, which lie 12 million light-years away in the constellation Ursa Major. The gravity from each galaxy dramatically affected the other during their last close encounter, 200 million years ago. Gas density waves rippling around M81 make it a grand design spiral. M82 is undergoing a starburst at its core, creating glowing fingers of hydrogen.
Right: A Hubble Space Telescope visible light image of bright blue star clusters found along a wispy bridge of gas that was tidally stretched between the two galaxies, and a third companion galaxy not seen in this picture. This is not the place astronomers expect to find star clusters because the density of gas is so low. Turbulence in the gas may have enhanced the density locally to trigger starbirth. The so-called “blue blobs” are clumped together in a structure called Arp’s Loop. Hubble reveals the clusters contain the equivalent of five Orion Nebulae. A Hubble plot of the stellar population in the clusters yields an age of approximately 200 million years, which coincides with the epoch of the collision.
Credit: NASA, ESA, and D. de Mello (Catholic University of America/GSFC)
The Iris Nebula
Like delicate cosmic petals, these clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula and dutifully cataloged as NGC 7023, this is not the only nebula in the sky to evoke the imagery of flowers. Still, this beautiful digital image shows off the Iris Nebula’s range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a massive, hot, young star in its formative years. Central filaments of cosmic dust glow with a reddish photo luminescence as some dust grains effectively convert the star’s invisible ultraviolet radiation to visible red light. Yet the dominant color of the nebula is blue, characteristic of dust grains reflecting starlight. Dark, obscuring clouds of dust and cold molecular gas are also present and can lead the eye to see other convoluted and fantastic shapes.
Image credit: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT