The gigantic Smith Cloud is making a comeback run for Milky Way. The humongous gas cloud is expected to crash in our galaxy’s outer disk in 30 million years time.
Since its discovery in the 1960s, Smith Cloud has been a fascinating study object. Plummeting towards the Milky Way at the moment, Smith Cloud could be studied in a detailed fashion. Scientists were particularly interested in the composition of the giant gas cloud. Any clues found in the gas cloud’s composition are also relevant for understanding the cloud’s origin.
The findings of the study suggest that the gas cloud would have originated at the Milky Way’s outer edges. Other theories maintain that Smith Cloud originated inside the galaxy. Nonetheless, an extreme event would have pushed it further and further away from the Milky Way.
As the gigantic Smith Cloud is making a comeback run for the Milky Way, here are a few facts. The gas cloud eerily shaped as a comet stretches 11,000 light-years in length and about 2,500 light-years in width. Provided Smith Cloud could be observed in visible light, it would cover the sky with a diameter 30 times that of the moon. As for the comeback run, scientists aren’t joking. Although it would take Smith Cloud another 30 million years to impact our galaxy, it’s still speeding at 700,000 miles/hour.
When the impact does occur, the collision could spur 2 million suns in the Milky Way. To unlock the door to the giant cloud’s composition researchers used Hubble Space Telescope images and Green Bank Telescope data. Previously, it was believed the cloud’s composition was mostly hydrogen.
Now, astronomers have discovered that Smith Cloud also contains heavy elements. The results yield proof that the giant gas cloud originated in our galaxy. Heavy elements are the signature of stars. Milky Way’s outer disk is a region rich in sulfur. The outer disk, located 40,000 light years from Milky Way’s center as well as 15,000 light-years beyond the solar system has collected material from stars. Heavy elements, the chemical signature of stars are found in the Smith Cloud as well. According to the researchers, about 70 million years ago the giant gas cloud was expelled from our galaxy’s outer disk. Now, the gigantic Smith Cloud is making a comeback run for Milky Way.
The gas cloud is a high-velocity cloud. Its orbit has been studied and determined since its discovery in the 1960s. Hubble Space Telescope’s Cosmic Origins Spectrograph was used to observe the ultraviolet light emitted by the cores of the three other galaxies found beyond the cloud. As Smith Cloud absorbs light from the cores of these galaxies, the astronomers could gain deeper insight into the chemical makeup of the gigantic gas cloud.
The study is published in the Astrophysical Journal Letters.
Photo Credits: hubblesite.org