The iconic Hubble Space Telescope has made many discoveries over its three-decade career.
Now he may have solved another mystery – how the Milky Way’s two largest satellite galaxies remain intact and capable of forming stars.
The phenomenon has long baffled astronomers because, for billions of years, the Large and Small Magellanic Clouds have collapsed and left behind trails of gaseous debris as they orbit each other and are drawn to our home galaxy.
Despite this, however, dwarf galaxies are still able to create stellar matter when one would expect they would not have enough gas to do so.
Thanks to data from Hubble, the answer to the riddle appears to lie in the fact that Magellan’s system is surrounded by a protective shield of supercharged hot gas called the corona.
Theory: Hubble may have discovered how the Large and Small Magellanic Clouds are able to form stars despite the presence of trails of gaseous debris. The system is surrounded by a protective shield of hot gases that prevents their gas supply from being siphoned off by the Milky Way.
This shrouds the two dwarf galaxies, preventing their gas supplies from being siphoned off by the nearby Milky Way, and thus allowing them to continue forming new stars.
“A lot of people were struggling to explain how these streams of material could be there,” said Dhanesh Krishnarao, an assistant professor at Colorado College.
“If this gas was removed from these galaxies, how do they still form stars? »
He and his team discovered why with the help of Hubble and a retired satellite called Far Ultraviolet Spectroscopic Explorer (FUSE).
“Galaxies envelop themselves in gaseous cocoons, which act as defensive shields against other galaxies,” said co-researcher Andrew Fox of the Space Telescope Science Institute in Baltimore, Maryland.
Astronomers predicted the existence of the corona many years ago.
“We found that if we included a corona in simulations of the Magellanic Clouds falling over the Milky Way, we could explain the mass of gas extracted for the first time,” said co-investigator Elena D’Onghia. the University of Wisconsin-Madison.
“We knew the Large Magellanic Cloud had to be massive enough to have a corona.”
Although the corona extends more than 100,000 light-years from the Magellanic Clouds and covers much of the southern sky, it is effectively invisible.
Mapping it meant astronomers had to sift through 30 years of archived data for proper measurements.
They believe that the crown of a galaxy is a remnant of the primordial gas cloud that collapsed to form the galaxy billions of years ago.
Although coronas have been observed around more distant dwarf galaxies, astronomers have never been able to probe one in such detail.
“There are many predictions from computer simulations of what they should look like, how they should interact over billions of years, but from an observational point of view we can’t really test most of them. because dwarf galaxies are usually too difficult to detect,” Krishnarao said.
Although the corona extends more than 100,000 light-years from the Magellanic Clouds and covers much of the southern sky, it is effectively invisible.
Because they are right on our doorstep, the Magellanic Clouds provide an ideal opportunity to study how dwarf galaxies interact and evolve.
Looking for direct evidence of Magellan’s corona, the team scoured the Hubble and FUSE archives for ultraviolet sightings of quasars billions of light-years behind it.
Quasars are the extremely bright nuclei of galaxies that harbor massive active black holes.
The team theorized that although the corona is too dark to see on its own, it should be visible as a kind of fog obscuring and absorbing the distinct patterns of bright light from the quasars in the background.
Hubble observations of quasars have been used in the past to map the corona surrounding the Andromeda Galaxy.
By analyzing ultraviolet light patterns from 28 quasars, the team was able to detect and characterize the material surrounding the Large Magellanic Cloud and confirm the existence of the corona.
The Hubble Space Telescope (pictured) has been observing the universe for more than 30 years
As expected, the quasar spectra are imbued with the distinct signatures of carbon, oxygen and silicon that make up the hot plasma halo that surrounds the galaxy.
The ability to detect corona required extremely detailed ultraviolet spectra.
“The resolution of Hubble and FUSE was crucial for this study,” Krishnarao said. “The corona gas is so diffuse it’s barely there.”
Additionally, it is mixed with other gases, including streams drawn from the Magellanic Clouds and material from the Milky Way.
Mapping the results, the team also discovered that the amount of gas decreases with distance from the center of the Large Magellanic Cloud.
“It’s a perfect telltale signature that this crown is really there,” Krishnarao said. “It’s really about cocooning the galaxy and protecting it.”
So how can such a thin envelope of gas protect a galaxy from destruction?
“Anything that tries to pass through the galaxy has to pass through this material first, so it can absorb some of that impact,” Krishnarao said.
“Also, the crown is the first material that can be extracted. By giving up some of the corona, you are protecting the gas that is inside the galaxy itself and is capable of forming new stars.
The discovery was published in the journal Nature.
NASA’s Hubble Space Telescope is still operating and has made more than 1.5 million observations since its mission began in 1990
The Hubble Telescope was launched on April 24, 1990 via Space Shuttle Discovery from Kennedy Space Center in Florida.
It is named after the famous astronomer Edwin Hubble, born in Missouri in 1889.
He is arguably most famous for discovering that the universe is expanding and the rate at which it is doing so – now inventing the Hubble constant.
The Hubble Telescope is named after famous astronomer Edwin Hubble, who was born in Missouri in 1889 (pictured)
Hubble has made more than 1.5 million observations since its mission began in 1990 and has contributed to the publication of some 18,000 scientific papers.
It circles the Earth at a speed of approximately 17,000 mph (27,300 km/h) in low Earth orbit at an altitude of approximately 340 miles.
Hubble has a pointing accuracy of 0.007 arcseconds, which is equivalent to being able to shine a focused laser beam on Franklin D. Roosevelt’s head from about 200 miles (320 km) away.
The Hubble Telescope is named after Edwin Hubble, responsible for creating the Hubble Constant and one of the greatest astronomers of all time.
Hubble’s main mirror is 2.4 meters (7 feet, 10.5 inches) in diameter and in total 13.3 meters (43.5 feet) long – the length of a large school bus.
The launch and deployment of Hubble in April 1990 marked the most significant advance in astronomy since the Galileo telescope.
Through five servicing missions and over 25 years of operation, our view of the universe and our place within it has never been the same.
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