Sailing a Starry Sea

Credit: ESA/Hub­ble & NASA

A spi­ral galaxy seems to sail across this image of the Hick­son Com­pact Group 7 from the NASA/ESA Hub­ble Space Telescope.

Explore the var­i­ous galaxy types in this image. What sto­ries or pic­tures do you see? Leave a note below. HCG 7 is a close group­ing of sev­eral galax­ies. Three spi­ral galax­ies and a lens-shaped, or lentic­u­lar, galaxy make up this tight-knit group. Look for the many far-off galax­ies scat­tered through­out the image.

Gen­er­ally, galax­ies are scat­tered far apart through­out the uni­verse. The clos­est large galaxy to our Milky Way Galaxy is the mas­sive Androm­eda Galaxy about two mil­lion light-years away. Sci­en­tists study­ing HCG 7 find that star for­ma­tion has been con­stant through­out the life of the galaxy. What puz­zles astronomers is the galax­ies seem to be using up their sup­plies of gas and dust as if the galax­ies had inter­acted in the past. A close look at the galax­ies in HCG 7 don’t show tell-tale signs of galac­tic inter­ac­tion and col­li­sion, such as warped disks, long tails of mate­r­ial, or large amounts of hot, blue new stars.

Hick­son Com­pact Groups is based on a cat­a­log of 100 galaxy groups pub­lished by Paul Hick­son in 1982. The most famous group on Hickson’s list is Stephan’s Quin­tet. Although HCG 7 is found about 200 mil­lion light-years from Earth toward the con­stel­la­tion of Cetus the Whale, the galaxy group­ing is still con­sid­ered to be fairly close to our Milky Way Galaxy.