Gigapixels of Andromeda: One of our closest neighboring galaxies, the famous Andromeda galaxy, has been imaged like never before. You might have seen jaw-dropping pictures of this amazing spiral galaxy in the past, as it probably is the most photographed because of its size and proximity to Earth. However in 2015 Hubble produced an image of Andromeda so sharp and detailed that you can zoom in multiple times and see the individual stars!
The Andromeda galaxy is a spiral galaxy approximately 2,5 million light-years away from Earth. It is located in the constellation Andromeda in the vicinity of Cassiopeia. It is also known as Messier 31, M31 or NGC 224 and is often referred to as the Great Andromeda Nebula in older texts.
Andromeda is the nearest spiral galaxy to our own, the milky way. As it is visible as a faint smudge on a moonless night, it is one of the faintest objects visible to the naked eye, and can be seen even from urban areas with binoculars. It glows at an apparent magnitude of 3.4 and it renowned for being one of the brightest Messier objects. Although it appears more than 6 times as wide as the full moon when photographed through a larger telescope, only the brighter central region is visible with the naked eye.
Credits: NASA Goddard
Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way, the Triangulum Galaxy, and about 30 smaller galaxies. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains roughly one trillion stars, several times more than the number of stars in our own galaxy.
Because of its proximity to Earth, brightness and size, the Andromeda galaxy is probably one of the most photographed objects in the night sky and surely the most photographed galaxy. Powerful telescopes on Earth owned by scientific observatories have taken extraordinary pictures of M31 in the past, and even today amateurs still impress the large public with vibrant and dazzling imagery.
In 2015, the Hubble Space telescope once again changed the game forever. The achievement was two fold. It not only managed to produce the most detailed and sharpest image of M31 to date but it also collected enough data to make its altogether largest image ever assembled. This sweeping bird’s-eye view of a portion of the Andromeda galaxy is the sharpest large composite image ever taken of our galactic next-door neighbor. Though the galaxy is over 2 million light-years away, The Hubble Space Telescope is powerful enough to resolve individual stars in a 61,000-light-year-long stretch of the galaxy’s pancake-shaped disk. It’s like photographing a beach and resolving individual grains of sand. And there are lots of stars in this sweeping view — over 100 million, with some of them in thousands of star clusters seen embedded in the disk.
Never before have scientists been able to study the arrangement of individual stars in their own neighborhood of the galaxy. This ambitious photographic cartography of the Andromeda galaxy represents a new benchmark for precision studies of large spiral galaxies that dominate the universe’s population of over 100 billion galaxies.
NASA writes: ‘Hubble traces densely packed stars extending from the innermost hub of the galaxy seen at the left. Moving out from this central galactic bulge, the panorama sweeps from the galaxy’s central bulge across lanes of stars and dust to the sparser outer disk. Large groups of young blue stars indicate the locations of star clusters and star-forming regions. The stars bunch up in the blue ring-like feature toward the right side of the image. The dark silhouettes trace out complex dust structures. Underlying the entire galaxy is a smooth distribution of cooler red stars that trace Andromeda’s evolution over billions of years.’
The Hubble Space Telescope usually images galaxies and objects that are billions of light years away. By using the same power of magnification for an object that is ‘only’ 2.5 million light-years from us, the Hubble survey had to assemble no less than 7,398 exposures taken over 411 individual pointings into a huge image mosaic. Without those many exposures, astronomers would still have been able to study the individual stars and clusters but it would have been impossible analyze these in a much larger system like an arm or whole side of the galaxy.
NASA continues: ‘The panorama is the product of the Panchromatic Hubble Andromeda Treasury (PHAT) program. Images were obtained from viewing the galaxy in near-ultraviolet, visible, and near-infrared wavelengths, using the Advanced Camera for Surveys and the Wide Field Camera 3 aboard Hubble. This cropped view shows a 48,000-light-year-long stretch of the galaxy in its natural visible-light color, as photographed with Hubble’s Advanced Camera for Surveys in red and blue filters.
It would take about 600HD TVs to show the original Gigapixels of Andromeda picture in full quality. Since it quite hard to do this, the mosaic can be viewed in a user-friendly interactive version here: https://www.spacetelescope.org/images/heic1502a/zoomable/
Gigapixels of Andromeda: You can just zoom in from the original 1.5-billion-pixel image several times and still see amazing details. This cartography encompasses the dark lanes of hydrogen gas and dust, star nurseries like clusters and nebulae, and of course the unfathomable number of stars. As you zoom in to the maximum, you are looking at the individual stars in still excellent quality. The image also helps reveal the colors of those stars, which is a vital element for scientists because it gives them information on their temperature and life cycle. As you sweep through these seemingly unending fields of stars, you will blue, white, yellow and red stars.
To put things into perspective, remember that it has been established that each of these stars virtually possesses at least one planet with possible moons. How can you not think life doesn’t exist elsewhere in a not-so-distant galaxy? Amazing Gigapixels of Andromeda