Sparks in the Dark


Violent things can come in small faint packages as shown in this NASA/ESA Hubble Space Telescope image of the starburst galaxy NGC 3738.

Explore the glowing red reservoirs of hydrogen gas, filaments of dust, and diffuse glow of thousands of stars in this faint irregular galaxy. What shapes and stories do you see? Leave a note in the comments below.

NGC 3738 is a dwarf galaxy in the middle of extreme star formation. The glowing red areas are full of hydrogen, the stuff that helps make new stars. Gravity pulls together gas and dust in pockets within the cloud. As the pocket becomes more massive, it begins to heat up until eventually it can become hot enough to fuse hydrogen atoms in a sustainable nuclear reaction. These new stars give off strong stellar winds and ultraviolet radiation that excites hydrogen atoms in the rest of the cloud causing it to glow a characteristic red.

This galaxy is relatively close to Earth; just 12 million light-years from the Sun; meaning light, traveling nearly 6 trillion miles per year, took 12 million years to cross the intergalactic distance. NGC 3738 is a compact bluish dwarf galaxy, the faintest of starburst galaxies. Blue compact dwarfs are generally blue because of large clusters of hot, blue and young stars. These stars tend to be massive, meaning they burn through their supply of hydrogen fuel within just a million years. If they are massive enough, they will end their lives in cataclysmic stellar explosions called supernovae. For a time, a single star can outshine an entire galaxy, releasing more energy in a few moments than our Sun produces in its entire expected lifespan of 8 billion years.

As you explore NGC 3738, you may notice it seems jumbled and disorganized. These galaxies don’t have spiral arms nor bright center bulges. Some astronomers believe these galaxies resemble some of the earliest galaxies that formed in the early Universe and may provide clues into how stars and galaxies formed during that time. As you pan across the image, look for dozens of faint and faraway galaxies scattered throughout this deep image of the cosmos.

NGC 3738, first observed by British astronomer William Herschel in 1789, is found in the constellation Ursa Major, The Great Bear or Big Dipper. It belongs to the Messier 81 group of galaxies, a nearby galactic cluster.

Send as an ECard

Leave a Reply


The ancient peoples saw pictures in the sky. From those patterns in the heavens, ancient storytellers created legends about heroes, maidens, dragons, bears, centaurs, dogs and mythical creatures...
Read More

Latest Comments