Thu. Jan 27th, 2022

Three years ago, Filippo Fraternalli and his colleagues have seen half a dozen mysteriously scattered galaxies that look like they and vast cities of gas. But with almost every galaxy we see, including our own Milky Way, they do not seem to be covered by a massive mass of dark matter, which would normally hold these stellar metropolises with their gravity. Scientists chose one to zoom in on a medium-sized galaxy about 250,000 light-years away, and they pointed to 27 radio telescope antennas in a very large array in New Mexico.

After collecting 40 hours of price data, they mapped out the stars and gas and confirmed what previous snapshots indicated: “The amount of dark matter we estimate in this galaxy is much, much smaller than you expected,” said Fraternalli, in the Netherlands. Captain is an astronomer at the Astronomical Institute of Groningen University. If teams or their competitors find such galaxies, it could be a challenge for scientists. See Dark Matter, An influential perspective in the field for at least 20 years. Brotherhood and his team Published their results In December Monthly notification of the Royal Astronomical Society.

Based on decades of telescope observation and computer simulation, scientists have come to think of Dark Matter as the hidden skeleton of the universe; Its “conjunction” is a huge mass of invisible particles that host large and small galaxies. But Fraternali is not the first to find exceptions to that rule. A few years ago, Peter van Dukkum, an astronomer at Yale, and his colleagues Discovered With similar galaxies Hubble Telescope Which also seemed to lack a dark substance. “These galaxies that we found in 2018 created a lot of debate and discussion and follow-up work because they were unexpected and difficult to explain,” said Van Dokkum.

These other galaxies lived in crowded environments, where larger, neighboring galaxies often flew, probably dragging dark matter along with them. In contrast, the fraternal galaxy is quite isolated, with no disturbing neighbors, so its lack of dark matter cannot be explained in this way. “It could be very significant,” Van Dokkum said. “How do you get stars and gas together in that position without the help of dark matter?”

These strange objects have been called “scattered galaxies”. They are extremely expressive: in terms of their mass, they are small, but they are spread over huge distances. Some are as big as galaxies, but only have one hundred stars — or less. They are so close to being transparent that it is difficult for them to spy on the night sky. “They are a bit weak in the center, so it is difficult to identify them. Now, with better telescopes and deeper observation, they have become more familiar, “said Miriam Montes, an astronomer at the Space Telescope Science Institute in Baltimore and an expert on such galaxies.

Beginning in the 1960’s, American astronomer Vera Rubin and others first discovered the possible existence of unseen or “dark” matter when measuring how fast the galaxy’s stars revolved around the center, showing that the inner stars revolve at different speeds than the outer ones. Based on the rotation of these stars, scientists calculated how much mass they needed to keep orbiting the galaxy without going into space. For many galaxies, this mass was many times larger than all the stars added. Scientists have solved the problem by assuming the presence of some kind of dark matter, which does not emit or reflect light, and which, of course, is creating the rest of the mass that holds the galaxy together.

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