"While we are excited to find so many black holes in Andromeda, we think it's just the tip of the iceberg," Robin Barnard, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said in a statement. "Most black holes won't have close companions and will be invisible to us."
Most of the newfound black holes have about five to 10 times the mass of our sun, and resulted from the deaths of giant stars. Seven of the new candidates were found within 1,000 light-years of the center of the Andromeda galaxy — more than the number of black holes near the core of our own Milky Way.
"We are particularly excited to see so many black hole candidates this close to the center, because we expected to see them and have been searching for years," Barnard said.
Scientists expected more black holes at our neighbor galaxy's center because Andromeda's bulge, the dense blob of stars at its middle, is larger than the Milky Way's.
"When it comes to finding black holes in the central region of a galaxy, it is indeed the case where bigger is better," co-author Stephen Murray of Johns Hopkins University and the Center for Astrophysics said in a statement. "In the case of Andromeda, we have a bigger bulge and a bigger supermassive black hole than in the Milky Way, so we expect more smaller black holes are made there as well."
The new black holes were discovered using NASA's Chandra X-ray Observatory, which made 150 separate observations over 13 years to detect them.
The researchers studied the peculiarities in the X-ray light given off by the objects to determine whether they were more likely to be black holes or dense objects called neutron stars. They discriminated black holes belonging to Andromeda from brighter, more distant supermassive black holes at the center of other galaxies by studying the patterns of variation in their brightness. Follow-up observations by the European Space Agency's XMM-Newton X-ray observatory added support to the idea that these 26 objects are indeed black holes.
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By Clara Moskowitz, SPACE.com Assistant Managing Editor
Leisure activities account for two-thirds of all lightning-related fatalities recorded in the United States each year.
Thousands of residents in eastern Australia were forced to evacuate on Thursday as excessive rainfall from former Severe Tropical Cyclone Debbie triggered major flooding.
Communities from the Ohio Valley to the Gulf Coast will be at risk of severe thunderstorms capable of producing tornadoes and damaging winds into Friday.
The warmest air since September will surge across Germany on Friday into Saturday.
After harsh winter conditions finally subside, automotive experts say this time of year is a great opportunity to do some spring cleaning and routine maintenance on your vehicle.
Rain returned to the United Kingdom at midweek and will linger into the weekend.
An outbreak of severe weather unfolded across the south-central United States on Tuesday and continued to impact parts of Oklahoma and Texas into Wednesday morning.