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
Another GalaxyCredit: ESA/Hubble & NASA
Thursday, December 27, 2012
Galaxy ESO 318-13 lies millions of light-years from Earth, but Hubble Space Telescope shows it with remarkable clarity in this image. The bright star that appears to shine from within the galaxy actually belongs to our galaxy, the Milky Way, and sits much closer to us than ESO 318-13. Other galaxies appear as tiny discs throughout the photograph. A distant spiral galaxy clearly shines through ESO 318-13 at the right hand side of the image.
Herschel and Keck take census of the invisible universe
By combining the observing powers of ESA’s Herschel space observatory and the ground-based Keck telescopes, astronomers have characterised hundreds of previously unseen starburst galaxies, revealing extraordinary high star-formation rates across the history of the Universe.
Starburst galaxies give birth to hundreds of solar masses’ worth of stars each year in short-lived but intense events. By comparison, our own Milky Way Galaxy on average produces the equivalent of only one Sun-like star per year.
Starburst galaxies generate so much starlight that they should outshine our Galaxy hundreds to thousands of times over, but the enormous quantities of gas fuelling them also contain vast amounts of dust as a result of the frantic star formation.
The dust absorbs much of the visible light, meaning that many of them look quite insignificant in that part of the spectrum. However, the dust is warmed by the surrounding hot stars and re-emits the energy at far-infrared wavelengths.
Using ESA’s infrared Herschel space observatory, astronomers measured the temperature and brightness of thousands of dusty galaxies. From these, their star-formation rate could be then calculated.
To provide context to the observations and understand how star formation has changed over the Universe’s 13.7 billion year history, the distances to the galaxies were also needed.
With Herschel signposting the way, astronomers used spectrometers on the twin 10-metre W.M. Keck telescopes on Mauna Kea, Hawai‘i, and obtained the redshifts of 767 of the starburst galaxies.
Redshifts provide astronomers with a measure of how long the light from each galaxy has travelled across the Universe, which, in turn, indicates when in cosmic history the light from each galaxy was emitted.
For most of the galaxies it was found that the light has been travelling towards us for 10 billion years or less. About 5% of the galaxies are at even greater redshifts: their light was emitted when the Universe was only 1–3 billion years old.
How such large numbers of starburst galaxies formed during the first few billions of years of the Universe’s existence poses a vital problem for galaxy formation and evolution studies.
One leading theory proposes that a collision between two young galaxies could have sparked an intense short-lived phase of star formation. Another theory speculates that, when the Universe was young, individual galaxies had much more gas available to them to feed from, enabling higher rates of star formation without the need of collisions.
“Before Herschel, the largest similar survey of distant starbursts involved only 73 galaxies – we’ve improved on that by over a factor of ten in this combined survey with Keck to determine the characteristics of this important galaxy population,” adds Göran Pilbratt, ESA’s Herschel project scientist.
Image credit: ESA–C. Carreau/C. Casey (University of Hawai’i); COSMOS field: ESA/Herschel/SPIRE/HerMES Key Programme; Hubble images: NASA, ESA