A bright quasar, powered by a supermassive black hole, is blasting radiation that blows away clouds of gas in its surroundings to generate winds that reach speeds of about 36 million miles per hour (58 million kilometers per hour). Oh, and the quasar is also almost as old as the universe itself.
The discovery, made by a team of scientists led by University of Wisconsin-Madison astronomers, shows the role that feeding supermassive black holes at the hearts of so-called “active galactic nuclei,” or “AGNs,” can play in sculpting the wide. the galaxies around them.
The researchers reached their findings using eight years of data on the quasar SBS 1408+544, located 13 billion light-years away in the constellation Boots. These data were collected by the Black Hole Reverberation Mapping Project conducted by the Sloan Digital Sky Survey (SDSS). Light from SBS 1408+544 has been traveling to Earth for 13 billion years; that’s about as long as the 13.8 billion year universe has existed.
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While supermassive black holes with masses equivalent to millions, or sometimes billions, of suns are thought to exist in the hearts of most galaxies, not all of these power quasars. Quasar black holes are surrounded by matter in a flattened rotating cloud called an “accretion disk” that gradually feeds them material.
The immense gravitational pull of a quasar’s central supermassive black hole causes friction and tidal forces that heat the material of the accretion disk, causing it to glow intensely. Furthermore, matter not fed by the supermassive black hole is channeled to the cosmic titan’s poles by powerful magnetic fields, where it is accelerated to near-light speeds and exploded as closely aligned jets. These double jets from each pole of the black hole are also accompanied by emissions of electromagnetic radiation.
Not only does this radiation make some quasars brighter than the combined light of every star in the galaxies around them, but this light also shapes those galaxies and provides a useful gauge for astronomers to measure the impact that black holes have on galaxies in general.
“The material in that [accretion] The disk is always falling into the black hole, and the friction of this tug and pull heats the disk and makes it very, very hot and very, very bright,” said team leader and professor of astronomy at the University of Wisconsin-Madison , Catherine Grier. Statement “These quasars are truly luminous, and because there is a large temperature range from the inner to the outer parts of the disk, their emission covers almost the entire electromagnetic spectrum.”
The bright light from this particular quasar allowed Grier and colleagues to trace winds of gaseous carbon. This was done by measuring gaps in the broad spectrum of electromagnetic radiation emitted by the quasar, which indicated that light was being absorbed by carbon atoms.
The team found that every time they measured this absorption spectrum over 130 observations of SBS 1408+544, there was a shift from the correct position of the carbon absorption “shadow”. This increased over time as radiation from the quasar removed material from around it. This material formed supermassive black hole winds that reached speeds of up to 36 million miles per hour (58 million kilometers per hour), which is about 45,000 times the speed of sound.
“This change tells us that the gas is moving faster and faster all the time,” said team co-leader and University of Wisconsin-Madison astronomy graduate Robert Wheatley. “The wind is accelerating because it’s being pushed by radiation blasting from the accretion disk.”
Scientists have suspected that they have seen accelerated supermassive black hole winds before, but this is the first time the observation has been backed up with hard evidence. Such cosmic winds are of great interest to astronomers because the gas they displace serves as the building blocks of stars. That is, if black hole winds are strong enough, they can stop star formation, “killing” their host galaxies. They can also deprive the central supermassive black hole of fuel, ending their days as quasar machines.
This can turn an active galaxy into a quiescent one like the Milky Way, which, in addition to forming stars at a very slow rate, also has a “sleeping giant” black hole at its heart. Sagittarius A* (Sgr A*), our black hole, is surrounded by so little matter that its diet of gas and dust is equivalent to a human eating a grain of rice every million years. Alternatively, winds from supermassive black holes could crush the gas instead of blowing it away, which would trigger new bouts of star formation in their host galaxies.
Black hole winds like those seen by the team can also travel beyond their own galaxies, affecting neighboring galaxies and, eventually, the neighboring supermassive black holes at the heart of those galaxies.
“Supermassive black holes are big, but they’re really small compared to their galaxies,” Grier said. “That doesn’t mean they can’t ‘talk’ to each other, and it’s a way for one to talk to the other that we’ll have to account for when we model the effects of these types of black holes.”
The team’s research was published in June in The Astrophysical Journal.
