WASHINGTON — It’s a double cosmic conundrum: Lots of stuff that was once already invisible has long past lacking.
Astronomers have discovered a far off galaxy the place there is no dark matter.
Dark matter is known as “dark” as a result of it will possibly’t be observed. It’s the mysterious and invisible skeleton of the universe that scientists determine makes up about 27 p.c of the cosmos. Scientists handiest know dark matter exists as a result of they are able to follow the way it pushes and pulls issues they are able to see, like stars.
It’s intended to be far and wide.
But Yale University astronomer Pieter van Dokkum and co-workers spied a limiteless, outdated galaxy with moderately few stars the place what you notice in reality is what you get. The galaxy’s stars are dashing round and not using a obvious affect from dark matter, in keeping with a learn about printed in Wednesday’s magazine Nature.
Instead of shaking the very foundations of physics, scientists say this absence of dark matter might lend a hand turn out the lifestyles of, stay up for it, dark matter.
“Not sure what to make of it, but it is definitely intriguing,” wrote Case Western Reserve astronomer Stacy McGaugh, who was once no longer phase of the learn about, in an e mail. “This is a weird galaxy.”
Van Dokkum research diffuse galaxies, ones that quilt monumental spaces however have moderately few stars. To search for them he and co-workers constructed their very own makeshift telescope out of 48 telephoto lenses that he first examined by means of the usage of a toy flashliDragonfly,e a mild on a paper clip. The bug-eyed telescope, known as Dragonfly, friends into the sky from New Mexico.
Using Dragonfly, van Dokkum and co-workers discovered a big, sparse galaxy known as NGC1052-DF2 within the northern constellation Cetus, sometimes called the whale. It’s as large because the Milky Way however with just one p.c of its stars. Then they used better telescopes on Hawaii and ultimately the Hubble Space Telescope to review the galaxy.
Even regardless that the galaxy is most commonly empty, they discovered clusters of densely grouped stars. With measurements from the telescopes, van Dokkum and co-workers calculated how briskly the ones clusters moved. If there have been a standard quantity of dark matter the ones clusters can be dashing round at about 67,000 mph (108,000 kilometers according to hour). Instead, the clusters had been shifting at about 18,000 mph (28,000 kilometers according to hour). That’s about how briskly they might transfer if there have been no dark matter in any respect, van Dokkum mentioned.
The staff additionally calculated the overall mass of the galaxy and located the celebrities account for the entirety, with very little room left for dark matter.
“I find this unlikely in all possible contexts,” mentioned McGaugh, who is a proponent of a “modified gravity” idea that excludes the lifestyles of dark matter altogether. “That doesn’t make it wrong, just really weird.”
How may just this absence of dark matter lend a hand turn out that it exists? By probably disproving changed gravity theories that recommend gravity acts in some way that the cosmos is smart with out dark matter. But the ones choice theories require stars on this galaxy to zip a minimum of two times as rapid as they had been observed shifting on this learn about.
Other outdoor scientists mentioned the preliminary have a look at the calculations seem to be right kind, regardless that the consequences are confounding. A galaxy with so few stars will have to have extra dark matter than others, no longer none.
“These are very strong scientists and so I take the results very seriously,” mentioned Marc Kamionkowski, a physicist at Johns Hopkins University.
One outsider recommended that most likely the “galaxy” van Dokkum studied is so diffuse that it would possibly not actually be a galaxy. Another recommended that the dark matter would possibly simply be outdoor of the world that van Dokkum measured.
Van Dokkum pushed aside each chances. “It’s sort of non-negotiable. There’s nothing else, just the stars,” he mentioned. The handiest means this will also be defined is if dark matter exists within the universe, simply no longer in that galaxy, he mentioned.
There’s no excellent cause of why and the way this galaxy has no dark matter, van Dokkum mentioned. He proposed 4 other chances — all unproven. His favourite: That the galaxy shaped within the very early universe in some way astronomers have by no means observed or understood.
“It’s not so often you get a true surprise,” van Dokkum mentioned.