Messier 33 - The Triangulum Galaxy

The VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile has captured this beautifully detailed image of the galaxy Messier 33, often called the Triangulum Galaxy. This nearby spiral, the second closest large galaxy to our own galaxy, the Milky Way, is packed with bright star clusters, and clouds of gas and dust. This picture is amongst the most detailed wide-field views of this object ever taken and shows the many glowing red gas clouds in the spiral arms with particular clarity.

Image credit: ESO

Note: For more information, see Triangulum Galaxy Snapped by VST.

Messier 33 - The Triangulum Galaxy

The spiral galaxy M33, also known as the Triangulum Galaxy, is one of our closest cosmic neighbors, just three million light-years away. Home to some forty billion stars, it is the third largest in the Local Group of galaxies after the Andromeda Galaxy (M31) and our own Milky Way.

M33 is popular with astrophotographers and from exceptionally dark sites it can even be seen with the naked eye. Thanks to its orientation, we can enjoy a face-on view of the beautiful spiral structure of the galaxy's disc.

This image, from ESA's Herschel space observatory, shows M33 in far-infrared light, revealing the glow of cosmic dust in the interstellar medium that permeates the galaxy. The patchy, disorganized structure of M33's spiral arms resembles a tuft of wool, leading astronomers to classify it as a flocculent spiral galaxy.

The brightest spots sprinkled along the spiral arms are dense pockets of gas and dust where massive stars are born. The most prominent of these is NGC 604, visible in the upper left spiral arm. This is an enormous star-forming region where hundreds of thousands of stars are taking shape.

The image is a composite of the wavelengths: 70 microns (blue), 100 microns (green) and 160 microns (red). At the shortest wavelengths, astronomers trace warmer dust, revealing individual regions of star formation and parent clouds. At longer wavelengths, they detect emission from colder dust, outlining some of the cool dust reservoir along the galaxy’s winding spiral arms. This is where stars may be born in the future.

The image spans about one degree on each side; north is up and east is to the left. The data were collected with Herschel's PACS instrument as part of the Herschel M33 extended survey (HerM33es) Key Programme to study the star formation in the Triangulum Galaxy.

Image credit: ESA/Herschel/PACS/HerM33es Key Programme/C. Kramer/M. Boquien

NGC 604 in Messier 33

Stars are sometimes born in the midst of chaos. About 3 million years ago in the nearby galaxy M33, a large cloud of gas spawned dense internal knots which gravitationally collapsed to form stars. NGC 604 was so large, however, it could form enough stars to make a globular cluster.

Many young stars from this cloud are visible in this image from the Hubble Space Telescope, along with what is left of the initial gas cloud. Some stars were so massive they have already evolved and exploded in a supernova. The brightest stars that are left emit light so energetic that they create one of the largest clouds of ionized hydrogen gas known, comparable to the Tarantula Nebula in our Milky Way's close neighbor, the Large Magellanic Cloud.

Photo credit: NASA

Messier 33 - The Triangulum Galaxy

This image captured by NASA's Wide-field Infrared Survey Explorer, or WISE, shows of one of our closest neighboring galaxies, Messier 33. Also named the Triangulum galaxy (after the constellation it's found in), M33 is one of largest members in our small neighborhood of galaxies -- the Local Group. The Local Group consists of about 30 galaxies that are gravitationally bound and travel together through the universe. M33 is the third largest member of the Local Group, dwarfed only by the Andromeda galaxy (M31) and our very own home galaxy, the Milky Way.

M33 is extremely close as far as galaxies go, residing only 3 million light-years away. Its proximity, along with it being conveniently tilted towards Earth (about 54 degrees to the line of sight), make it very easy for astronomers to study in detail. The infrared images that WISE produces contribute to astronomers' overall understanding of a variety of processes happening in the galaxy. Areas in the spiral arms that are hidden behind dust in visible light shine through brightly in infrared light, showing where clouds of cool gas are concentrated. Star-forming regions are easy to spot in infrared (green and red areas in this image). Notice that there isn't a lot of star formation occurring near the center of M33. It would be difficult to deduce this lack of activity in the core by only looking a visible-light image, where the core appears to be the brightest feature. This infrared image also shows that the galaxy is surprisingly bigger than it appears in visible light. The cold dust seen by WISE extends much further out from the core than anticipated.

The bright yellow-orange 'blobs' scattered throughout M33 are areas where stars are forming at an especially intense rate. The largest one in the spiral arm to the upper left has its own name, NGC 604. It's an "H II" region -- an area of gas that is being heated and ionized by powerful young stars recently born inside of it. The Orion nebula is an example of a nearby H II region within our own Milky Way galaxy. NGC 604, however, is the largest such region in the entire Local Group of galaxies. It is over 40 times larger than the Orion nebula and much brighter. If NGC 604 were at the same distance from Earth as the Orion nebula, it would be the brightest object in the night sky (besides the Moon).

M33 is over 50,000 light years across (about half the size of the Milky Way). Because it is so close it appears quite large to us, covering a piece of sky nearly four times bigger than the full moon. Its relatively low surface brightness makes it difficult for human eyes to see, however. Even so, under exceptionally dark skies it can be seen with the unaided eye, making it one of the farthest objects visible without a telescope.

These images were made from observations by all four infrared detectors aboard WISE. Blue and cyan, or blue-green, represent infrared light at wavelengths of 3.4 and 4.6 microns, which is primarily light from stars. Green and red represent light at 12 and 22 microns, which is primarily light emitted from warm dust.

Photo credit: NASA/JPL-Caltech/UCLA