[ad_1]
If two black holes dance in space but astronomers can’t see them, can we admire their striking dance moves?
Because black holes have such a strong gravitational pull that even light cannot escape, they cannot be observed directly and are therefore difficult to study. But a pair of black holes has made astronomers fall in love with a complicated celestial dance that periodically produces extremely bright flashes of light, explosions that are brighter than a trillion stars, and even the entire Milky Way galaxy.
By studying the timing of these bright flashes of light, the researchers have attempted to map the complex choreography of black hole movements and predict exactly when the system will explode again. After more than 120 years of observations and decades of building computer models, astronomers have finally figured out what these black holes are doing, thanks to data from the now-retired NASA. Spitzer Space Telescope.
Video: Pair of black holes produces flares ‘brighter than 1 trillion stars’
Related: The Greatest Spitzer Exoplanet Discoveries of All Time
The two “dancing” black holes are located 3.5 billion light years from Earth at the center of a galaxy called OJ 287. The larger of the two is one of the largest black holes ever found, weighing in at over 18 billion times. mass of the sun Orbiting around this large black hole is a much smaller black hole that is approximately 150 million times the mass of the sun. Twice every 12 years, the smallest black hole passes through the largest accretion disk, or the flat band of dust and gas that falls into the black hole, creating bright flashes of light.
Because the small black hole’s orbit is irregular, its position changes with each 12-year cycle around its partner, these flashes do not occur on a regular schedule. Sometimes they can occur as little as a year apart, while other times it can take up to a decade between outbreaks. The apparently random timing of flares has made it difficult for astronomers to figure out exactly what kind of “dance” these black holes are doing.
A computer simulation in 2010 was able to predict the outbreaks in one to three weeks. In 2018, another group of researchers led by Lankeswar Dey, a graduate student at the Tata Institute for Fundamental Research in Mumbai, published a new model that they say could predict the occurrence of eruptions in four hours. In a new study, published Tuesday (April 28) in The Astrophysical Journal Letters, Dey’s group reports that Spitzer’s observations of a flare on July 31, 2019 confirm that his model is correct.
The Spitzer Space Telescope, which NASA decommissioned in January, was in the right place at the right time to observe the flare that day, when no other telescope on Earth or in space could see it. At that time, OJ 287 was on the opposite side of the sun from Earth’s perspective.
Spitzer was 158 million miles (254 million km) from Earth at the time, and from his point of view, the telescope had a clear view of OJ 287 for just over a month, from July 31 to early September, NASA officials said in a statement. statement.
“When I first verified the visibility of OJ 287, I was surprised to find that it became visible to Spitzer just the day the next flare was forecast,” said Seppo Laine, a Caltech / IPAC scientist in Pasadena, California, who oversaw the Spitzer’s observations on the system, he said in the statement. “It was extremely fortunate that we were able to capture the peak of this flare with Spitzer, because no other man-made instrument was able to accomplish this feat at that specific time.”
To arrive at this accurate prediction, the researchers not only looked at the orbital mechanics of the system. They also had to account for gravitational waves, or waves in space-time created when massive objects move through space, deforming their surroundings. Astronomers expect the black hole system in OJ 287 to generate gravitational waves that are strong enough to alter the orbit of the smallest black hole, according to the statement.
By incorporating gravitational waves into their calculations, the researchers were able to predict a 1.5-day time frame in which the system will produce an outbreak. But they narrowed it down even further, to just four hours, given the “hairless theorem” of black holes, an idea Stephen Hawking doubted. This theorem postulates that the surfaces of black holes are featureless and symmetrical, rather than irregular and irregular. (Black holes do not literally have a “surface” but an invisible boundary known as the event horizon, where even light cannot escape the black hole’s gravitational pull.)
If the large black hole in the center of OJ 287 were bumpy, with its mass unevenly distributed, its gravitational pull on the smaller black hole would be inconsistent, affecting the orbit of the smaller black hole and the timing of eruptions. But the symmetric, spirograph-shaped orbit of the smaller object supports the no hair theorem, the new study says.
“It is important to black hole scientists that we prove or disprove the no hair theorem,” said Mauri Valtonen, an astrophysicist at the University of Turku in Finland and co-author of the study, in the statement. “Without it, we can’t trust black holes like those envisioned by Hawking and others.”
Email Hanneke Weitering at [email protected] or follow her @hannekescience. Follow us on twitter @Spacedotcom and in Facebook.
[ad_2]
