Small Galactic Caterpillar

Credit: NASA/JPL-Caltech/STScI

A long tail flows behind this galac­tic cater­pil­lar. NASA’s Spitzer Space Tele­scope takes a big view of the Small Mag­el­lanic Cloud.

Astronomers turned their satel­lite eyes on the Small Mag­el­lanic Cloud because it is close. This allows them to study the life cycle of stars close up. It also gives them hints about galaxy for­ma­tion. The Mag­el­lanic Clouds resem­ble young galax­ies thought to pop­u­late the early uni­verse. The Small Mag­el­lanic Cloud and its larger sis­ter galaxy, the Large Mag­el­lanic Cloud, are weak in heavy ele­ments such as car­bon. Heavy ele­ments are cre­ated in huge stel­lar explo­sions called super­nova. The stars of the Mag­el­lanic Clouds have not been around long enough to cre­ate large amounts of these ele­ments. On Earth, these ele­ments were nec­es­sary for the for­ma­tion of life.

Explore the image. Near the top of the image, find the blue col­ored stars light­ing up their dust clouds of red and green. Spitzer’s tele­scope shows us the uni­verse in infrared. It sees object in space that are warm and hot. The col­ors are not what we’d actu­ally see with our eyes. The col­ors rep­re­sent dif­fer­ent parts of the light seen by Spitzer. The results are still spec­tac­u­lar. The tail con­tains only gas, shown in green. Astronomers believe that the Mag­el­lanic Clouds inter­acted with each other and the Milky Way Galaxy start­ing a wave of new star for­ma­tion. Using infor­ma­tion from the images from Spitzer, astronomers show that the tail area has recently been torn off the main body of the galaxy. Find the two red dots in the tail. These are star clus­ters still sur­rounded by their birth clouds.

The Small and Large Mag­el­lanic Clouds were once con­sid­ered to be satel­lite galax­ies to the Milky Way. Recent mea­sure­ments, how­ever, show that the smaller galax­ies are just pass­ing by, inter­act­ing with the Milky Way and with each other. One day, the Large Mag­el­lanic Cloud may con­sume its smaller com­pan­ion. The galax­ies are named after the sea­far­ing explorer Fer­di­nand Mag­el­lan. He described them dur­ing his expe­di­tion around the world in the early 1500s. Euro­pean explor­ers referred to them as large and small clouds. The ear­li­est men­tion of the star clouds was by Per­sian astronomer Al Sufi in 964. He called what we know as the Large Mag­el­lanic Cloud al-Bakr, or the White Ox. He also noted that it was invis­i­ble from north­ern Ara­bia but could be seen by south­ern Arabs.