600 million light-years away from Earth lies Markarian 231 (Mrk 231). The galaxy is best known as the nearest galaxy to Earth that contains a quasar.
When astronomers pointed the Hubble Space Telescope at Mrk 231, they found the quasar is powered by a double black hole. When looking back at Hubble archival observations of ultraviolet radiation coming from the center of this galaxy, the astronomers found “extreme and surprising properties.”
Before I touch on what the astronomers found, let’s look at what should appear when there is one black hole. When one black hole is present, the entire accretion disk of hot gas glows in ultraviolet rays. In Mrk 231, the astronomers found this glow of ultraviolet gas suddenly drops off near the center. This hints at a large donut hole in the disk. Why? The presence of another black hole.
As you can see in the artist illustration above, the gravitational effects of the two black holes orbiting each other produce a large donut hole region in the middle.
Youjun Lu of the National Astronomical Observatories in China explains what the findings mean for the search for more binary black holes. “We are extremely excited about this finding because it not only shows the existence of a close binary black hole in Mrk 231, but also paves a new way to systematically search binary black holes via the nature of their ultraviolet light emission.”
Xinyu Dai, the co-investigator from the University of Oklahoma, says binary black holes “are natural consequences of these mergers of galaxies.”
The central black hole is massive. It’s estimated to be 150 times the mass of our sun. The second black hole comes in much smaller, but still huge at 4 million solar masses. The black hole pair orbits each other every 1.2 years. In the next few hundred thousand years, they will collide with each other.
Here’s a more traditional look at Markarian 231. You are looking at a galaxy as it appeared 581 million years ago.
The best recent Hubble images
You can keep track of every Hubble Space Telescope image here. Below, you can check out a few of my favorite recent Hubble images over the past year or so.
Twin Jet Nebula
I wrote about the Twin Jet Nebula last week. You are looking at the end stages of a star that is similar in size to our sun. There are actually two stars in this image. The larger one is responsible for the bright center glow in the image above. The second star has already moved on and has become a white dwarf.
Jupiter’s Great Red Spot Gets a Visitor
It’s not full of color as we are used to, but this image is incredible in its own right. We are looking at Jupiter’s Great Red Spot being filled in some by Ganymede’s shadow.
A gravitational tug-o’-war with NGC 7714
The smoke-ring-like structure seen in NGC 7714 is the result of gravitational interactions with nearby NGC 7715. According to astronomers, “the close encounter has compressed interstellar gas to trigger bursts of star formation seen in bright blue arcs extending around NGC 7714’s center.”
This will make you feel tiny. The image above comes from a composite of exposures taken in 2002 to 2012. You are looking at approximately 10,000 galaxies extending back to a time within a few hundred million years of the big bang.
Image credits: NASA, Hubble, ESA
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