M-100The Swirling Arms of the M100 Galaxy – M100 is a classic example of a grand design spiral galaxy, with prominent and well-defined spiral arms winding from the hot center, out to the cooler edges of the galaxy. It is located about 55 million light years away from Earth, in the little-known constellation of Coma Berenices, near to the more recognizable Leo.

In the center, we can see a prominent ring of hot, bright dust surrounding the inner galactic core. Moving further out, the spiral arms peter out towards the edges of the galaxy, where thick webs of dust dominate. Beyond the edges of the dust clouds, a faint blue glow of stars extends to the edge of the galaxys disk.

Two small companion galaxies, known as NGC 4323 and NGC 4328, appear as fuzzy blue blobs on the upper side of M100. These so-called lenticular galaxies are virtually clear of any dust, so they lack any of the red/green glow seen in their bigger neighbor. The shape of M100 is probably being perturbed by the gravity of these galaxies.

M100 was discovered in 1781, and is now known to stretch roughly 160,000 light years from one side to the other, making it about one and a half times the size of our own Milky Way galaxy. By studying these infrared images of M100, astronomers can map out the structure of the stars and dust, and study the ways in which galaxies like our Milky Way were formed.

M100 is well-known to astronomers because of the five stars that have become supernovae within the galaxy between 1901 and 2006. These exploding stars are extremely useful for helping astronomers to calibrate distance scales in the universe, and to estimate the age of the universe since its creation in the Big Bang.

The red regions reveal dust clouds that light up under the illumination of the surrounding stars. The stars themselves shine most brightly at the shorter infrared wavelengths, showing up here in blue. The blue dots covering the entire image are stars that lie between us and M100.

Infrared light with wavelengths of 3.6 and 4.5 microns are displayed in blue and green showing primarily the glow from starlight. 8 micron light is rendered in red; the small contribution from starlight at 8 microns was subtracted out from the data to better show the dust structures near the galaxys center.

This image was originally released on August 2, 2012.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit and

Newly discovered nebula…

a new Nebula

Hubble’s Messier 5

“Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] …” begins the description of the 5th entry in 18th century astronomer Charles Messier’s famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one of the oldest globulars, its stars estimated to be nearly 13 billion years old. The beautiful star cluster is a popular target for Earthbound telescopes. Of course, deployed in low Earth orbit on April 25, 1990, the Hubble Space Telescope has also captured its own stunning close-up view that spans about 20 light-years near the central region of M5. Even close to its dense core at the left, the cluster’s aging red and blue giant stars and rejuvenated blue stragglers stand out in yellow and blue hues in the sharp color image.

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