New space observatory helps solve mystery of massive black holes

Most galaxies form around huge black holes. While many of them are comparatively docile, like the one at the center of our Milky Way Galaxy, some are ferocious and devour the material around them, unleashing huge, incredibly bright jets of high-energy particles into space.

Using data from the recently launched imaging X-ray Polarimetry Explorer (IXPE) orbital observatory, researchers on Wednesday offered an explanation for how these jets become so luminous: subatomic particles called electrons are energized by shock waves. that move at supersonic speed away from the black hole.

The researchers studied an exotic object called a blazar at the center of a large elliptical galaxy, Markarian 501, located about 460 million light-years from Earth in the constellation of Hercules. A light year is the distance that light travels in one year, 9.5 trillion kilometers.

Blazars are a subset of objects called quasars that are powered by supermassive black holes that feed on gas and other material at the center of galaxies and send two jets of particles in opposite directions into space. Blazars are oriented so that one of their two jets, from our vantage point on Earth, is coming straight at us.

“Blazars are the most persistently bright objects in the observable universe. They are the most energetic, they have the biggest and scariest black holes. Everything that happens around them is very fascinating,” said astronomer Yannis Liodakis of the Finnish Center for ESO Astronomy, lead author of the research published in the journal Nature.

Scientists have long sought to understand how the jets launched by blazars become so luminous, and the behavior of the particles in them. The jets from this blazar extend to a distance of approximately one million light-years.

The IXPE, launched last December in a collaboration between the US space agency, Nasa, and the Italian Space Agency, measures the brightness and polarization – a property of light that involves the orientation of electromagnetic waves – of light in X-rays from sources cosmic. Different phenomena, such as shock waves or turbulence, have polarization “signatures”.

The researchers found evidence that jet particles become energized when hit by a shock wave that propagates outwards within the stream and emits X-rays as they accelerate. A shock wave is produced when something moves faster than the speed of sound through a medium like air — like a supersonic jet flying through Earth’s atmosphere — or a region with particles and magnetic fields called plasma, as in this one. case.

“The light we see from the jets comes from electrons,” said Boston University astrophysicist Alan Marscher, co-author of the study. “X-rays of the type we observed in Markarian 501 can only come from extremely high-energy electrons.”

The driving force behind this drama is a black hole, an extraordinarily dense object with such powerful gravity that not even light can escape. The supermassive black hole at the center of Markarian 501 has a mass around a billion times the mass of our Sun — about 200 times more than the mass of Sagittarius A*, the Milky Way’s supermassive black hole.

“Black holes are unique laboratories for studying fundamental physics under extreme conditions that we cannot reproduce on Earth,” said Liodakis.

“However, before we can use them as such, we need to understand all the physical processes that occur. We’ve been observing high-energy light from these sources for many years, and we had some theories of how the particles that emit this light would be energized. The capabilities of X-ray polarization at IXPE allowed us for the first time to directly test our theories,” said Liodakis.