While things like distance and size are difficult to really comprehend when it comes to outer space, astronomers do keep track of what is nearest our galaxy and how big it is compared to other neighbors in the universe.
Markarian 231 is the nearest galaxy to our own that hosts a quasar. A quasar can be thought of as an active source of energy within a galaxy. Sometimes called “Quasi-stellar radio sources” they are like stars, but are way more powerful and emit a much broader spectrum of light and electromagnetic radiation.
“Nearest” is a relative term since Mrk 231 is actually about 600 million light years away from Earth. It was discovered in 1969 and just recently researchers using the data from the Hubble Telescope found that at it’s core, the quasar that makes it one of the mostly luminous galaxies in the universe is powered by not one, but two black holes.
It’s normal that quasars are powered by one quasar, but two is significant. Quasars are part of the class of celestial objects known as “active galactic nuclei.” At the center of a galaxy, a black hole spins, with incredible mass and energy, but they are so dense that no light can escape. However some particles of space dust and gas can be spun free of them, both above and below the black hole and these are quasars, celestial objects with the energy of the most powerful actors in the universe—black holes—behind them.
The new information about Mrk231 indicates that it might not be that unusual to have two supermassive black holes at the center of a galaxy. When galaxies merge, their respective black holes sometimes come together in what’s called a binary black hole system. Orbiting around each other like a pair of whirling dervishes, a binary black hole will produce twice the power of galaxies that only have one, and as a result their quasars will not only outshine their host galaxy, but others around them as well.
When one black hole powers a quasar, the entire disk around it, which is made up of hot gas, would glow. In Mrk231 the glow of this disk drops off, in a sort of “donut hole” near the center. Based on the models investigators were able to design, the drop off is caused by a second black hole that circles the first one. This second one appears to be on the inner edge of disk of the first one, and has its own smaller accretion whorl that also glows.
The two black holes are not equal in size. The main one, at the center of Mrk231 is thought to be about 150 million times the mass of the Sun. Its partner is smaller, but still powerful with a weight of about 4 million times that of the sun. A complete orbit around each other takes about 1.2 years.
Check out the video below for more cool facts about Markarian 231
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