Data and images from the Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer (FUSE) revealed a corona protecting the Large and Small Magellanic Clouds.
The Magellanic Clouds are two galaxies that orbit one another. The Milky Way is pulling them toward itself with its higher gravity.
Without the corona, the Milky Way would be siphoning dust and gas away from the Magellanic Clouds at a high enough rate to make it difficult for them to form stars. As it is, the two galaxies are leaving behind a trail of dust and gas as the Milky Way pulls them in.
What Is This Corona?
Coronas are clouds of material that surround most galaxies and are left over from their coalescing into coherent galaxies billions of years ago. Astronomers detected similar coronas around dwarf galaxies, but they are hard to see even with powerful telescopes. In the case of the Magellanic Clouds, it took detailed analysis of ultraviolet light and advanced computer modeling to detect the thin corona surrounding them.
These coronas protect galaxies from the effects that they can have on one another through gravity. Like a shield, coronas protect their galaxies by “taking the hit” and losing their own material so their galaxies stay relatively intact. They can also shield galaxies from large collisions by absorbing some of the impact.
Of course, the coronas won’t help a galaxy that is merging with another one, as the Andromeda Galaxy is projected to do in 4 billion years. In fact, the halos belonging to the Andromeda Galaxy and Milky Way Galaxy are already touching. When the two galaxies finish merging and things start settling down about seven billion years from now, it will form one big elliptical galaxy.
Yes, the corona or “halo” can really be that big. Researchers estimate that the one protecting the Magellanic Clouds stretches as far as 100,000 light-years from the central galaxies.
The Magellanic Cloud’s corona improved modeling of these two galaxies.
According to astronomers’ models of the Magellanic Clouds, these two galaxies would have fallen apart a long time ago without the corona. They certainly would not have enough integrity to continue to form new stars.
FUSE only operated from 1999 to 2007, but the data it generated is still available to be combed through by astronomers. By going through archives of data produced by the Hubble Space Telescope and FUSE, astronomers could generate a more accurate model that included the corona.
Astronomers already suspected that the Large Magellanic Cloud was big enough to have a halo. The recent study published in the journal Nature confirmed it.
“We discovered that if we included a corona in the simulations of the Magellanic Clouds falling onto the Milky Way, we could explain the mass of extracted gas for the first time,” says Elena D’Onghia, a co-author of the research paper.
What are the Magellanic Clouds, anyway?
You might be thinking that it’s weird to call a couple of irregular dwarf galaxies in the southern celestial hemisphere “clouds,” and you’re probably right. The Large Magellanic Cloud is actually a star-forming powerhouse for a small galaxy and resides about 200,000 light-years from Earth. (Yes, that is pretty close for another galaxy.) The Small Magellanic Cloud is 210,000 light-years away.
These two galaxies look like fuzzy clouds to the naked eye, and famous Portuguese navigator Ferdinand Magellan probably thought they were weird celestial clouds when he was navigating his way around the world in the early 1500s and recorded observing them for the first time.
Their proximity does make them ideal for observations of other galaxies. Astronomers studying star formation like to observe the Large Magellanic Cloud’s Tarantula Nebula because it’s the brightest stellar nursery in the cosmic neighborhood, for instance.
It also makes the Magellanic Clouds more suitable for refining models of the evolution of small galaxies. Adding scientific data from observations made by the Hubble Space Telescope and FUSE revealed a corona that makes modeling the Magellanic Clouds more accurate.