Smithsonian.com

A black hole that trumps all others in size was detected by two NASA satellites and announced by researchers, led by Andrea Prestwich at the Harvard-Smithsonian Center for Astrophysics. The black hole is a hefty 24 to 33 times larger than the Sun (the previous best was 16 times larger).

Sitting 1.8 million light years away in the constellation Cassiopeia, this new record-breaker is a black hole of the stellar-mass variety, meaning it was formed when a massive star died and collapsed inward upon itself.

The team at the Harvard-Smithsonian Center for Astrophysics was able to estimate the black hole’s mass because it orbits another star that ejects gas, which spirals toward the black hole (above), heats up and emits revealing X-rays before being gobbled up by the hole.

Some suspected that the black hole bulked up as a result of an insatiable appetite, slurping up whatever was within its vicinity. But the study found that it has only gained one or two solar masses since its metamorphosis from star to black hole. Instead of shedding pounds, as most stars do before imploding, this one carried its mass into its black hole afterlife. Experts say the black hole was “born fat, it didn’t grow fat.”

The finding expands researchers’ understanding of just how massive a black hole can be. “We now know that black holes that form from dying stars can be much larger than we had realized,” Prestwich says.

(This artist’s conception shows the biggest stellar-mass black hole, upper left, which weighs 24 to 33 times as much as the Sun. It is pulling gas from a companion Wolf-Rayet star lower right. Aurore Simonnet/Sonoma State University/NASA.)

J. Allen Hynek got the call at 6:30 p.m., October 4, 1957.

The associate director of the Smithsonian Astrophysical Observatory, near Boston, hung up and told a colleague: “There’s a Russian satellite up.”

Sputnik’s launch shocked the public: scientists were surprised only that the Russians did it first—earlier that year, researchers worldwide had agreed their countries would send up satellites to study the planet. In anticipation, observatory director Fred Whipple had summoned amateur astronomers—to be called Moonwatchers—to track any satellites. After Sputnik, 83 teams in 20 countries (above, in Pretoria, South Africa) rushed to their posts. By 1959, some 230 teams were tracking two dozen satellites; the teams’ data led to an accurate measure of the Earth’s size and shape.

Cameras replaced the Moonwatchers by 1975. Hynek, who died in 1986, went on to study UFOs. In 1972 he coined the phrase “close encounters of the third kind.”

(Courtesy of the Smithsonian Institution Archives, image #96-960)