Hiding in the secretive hearts of perhaps every large galaxy in the Universe, they lurk with sinister intent, waiting for their unfortunate dinner to come to them. These strange and mystifying gravitational beasts are supermassive black holes, and they can weigh millions to billions of times more than our Sun, as they dine with a terrible, and sometimes seemingly insatiable, hunger on any doomed object that innocently passes too close to their powerful gravitational embrace. Supermassive black holes are thought to grow in mass through galactic mergers, whereby the black holes inhabiting the wreckage of a duo of colliding galaxies, also merge together themselves–therefore increasing in mass. In November 2016, astronomers using the sensitive and extremely sharp radio vision of the National Science Foundation’s Very Long Baseline Array (VLBA), announced that they have discovered the shredded remnants of an unlucky small galaxy that catastrophically passed through a larger galaxy. Alas, this galactic wreck left in its wake the smaller galaxy’s nearly naked supermassive black hole–screeching like a banshee as it emerged unclothed from the mess, flying away at over 2,000 miles per second!
The duo of colliding galaxies are members of a galactic cluster situated more than 2 billion light-years from our planet. The close encounter of the catastrophic kind, that occurred millions of years ago, tore away most of the doomed smaller galaxy’s lovely veil of sparkling stars and clouds of gas. The only thing remaining was the uncovered supermassive beast and a relatively small galactic relic a mere 3,000 light-years across. By comparison, our large barred-spiral Milky Way Galaxy is about 100,000 light-years across.
The discovery of this galactic tragedy was made as part of a program to spot supermassive black holes where they lurk hungrily in the secretive hearts of their host galaxies. Many astronomers propose that large galaxies grow in size by eating their smaller neighbors. In such hideous cases, the supermassive black holes of both galaxies are predicted to orbit each other in a macabre celestial dance, and then ultimately merge together.
“We were looking for orbiting pairs of supermassive black holes, with one offset from the center of a galaxy, as telltale evidence of a previous galaxy merger. Instead, we found this black hole fleeing from the larger galaxy and leaving a trail of debris behind it,” noted Dr. James Condon in a November 2, 2016 National Radio Astronomy Observatory (NRAO) Press Release. Dr. Condon is of the NRAO.
“We’ve not seen anything like this before,” Dr. Condon added.
Galaxies That Go Bump In The Night
Astronomers have known for years that perhaps every large galaxy in the Universe has a supermassive beast dwelling in its heart. Anything that is unlucky enough to wander too close to the clutches of these gravitational monsters is doomed, doomed, doomed, and can never escape from its sad fate as the black hole’s buffet. Not even light can escape from the clutches of its voracious and greedy gravitational captor.
Our own large starlit spiral Milky Way Galaxy has not merged with another large galaxy for a very long time. However, these collisions did occur in our Galaxy’s past, leaving behind their tattle-tale “fossil” remnants to tell the tale of past catastrophic encounters. Furthermore, in about 4 to 5 billion years our Milky Way is destined to experience a catastrophic collision and merger with another large galaxy–the somewhat larger neighboring spiral, the Andromeda galaxy (M31).
Whirling like two enormous star-blazing, beautiful pin-wheels in space, our own Galaxy and Andromeda are the two largest galactic inhabitants of the Local Group of galaxies. The Local Group hosts 54 galaxies in all, most of which are small dwarf galaxies, and its center is situated approximately between our Milky Way and Andromeda.
The Local Group, in turn, resides near the outer regions of the Virgo Cluster, whose glaring big heart is about 50 million light years from our planet. The many groups of galaxies and clusters of galaxies are all smaller components of enormous web-like filaments and thin, broad expanses, often referred to as the Great Wall. The Great Wall is a sheet-like collection of galactic constituents that is located about 200 million light years from Earth. A kindred structure, referred to as the Great Attractor, is pulling mercilessly with its powerful gravity, on the entire Virgo Cluster. Our Milky Way, Andromeda, and all of the smaller galaxies of the Local Group are carried away with the rest at a dizzying velocity of several hundred kilometers per second.
A sea-change will occur in both spirals when our Milky Way and Andromeda collide. The two large spirals will undergo a metamorphosis, merging into a single new galaxy that exhibits an elliptical shape, as opposed to a spiral shape. The enormous new galaxy has been playfully dubbed the Milkomeda Galaxy by some astronomers.
Currently, our Milky Way and Andromeda are rushing towards one another at the stupendous rate of 250,000 miles per hour. When the two galactic pin-wheels smash into each other the wreck is likely to be messy. Right now, Andromeda is flying straight in our direction, and when it finally crashes into our Milky Way, it will eat it. This is because Andromeda is the larger of the doomed duo.
The supermassive black hole dwelling in the heart of the great Milkomeda Galaxy, will be the extremely massive merged black holes of the current Milky Way and Andromeda galaxies–after having combined into one.
Supermassive black holes can grow to be at least as enormous as our entire Solar System. These mysterious, magnificent entities are well-known for their great mass and greed.
A Bare Black Hole Screeches Like A Banshee Through Space!
The astronomers who found the small shredded galaxy’s bare black hole began their chase using the VLBA to make very high-resolution images of over 1,200 galaxies that had already been found by large-scale sky surveys using radio and infrared telescopes. The VLBA observations revealed that the supermassive black holes haunting the hearts of almost all of these galaxies were located at the center of their galactic hosts.
However, one object stood out in the crowd. The strange object was located in a cluster of galaxies dubbed ZwCI 8193, and it did not fit into the pattern. Additional studies revealed that this mysterious object, named B3 1715+425, was a supermassive black hole surrounded by a galaxy much dimmer and smaller than would be expected. Furthermore, this strange object was rushing away from the center of a much larger galaxy–leaving a trail of ionized gas behind.
The astronomers came to the conclusion that B3 1715+425 is all that remains of a doomed galaxy that had catastrophically passed through the larger galaxy, and as a result had most of its gas and stars ripped away. The lingering relic of this galactic smash-up? The “nearly naked” supermassive black hole!
This speeding relic of a cosmic disaster will likely lose more mass and stop forming sparkling new baby stars, according to the team of astronomers.
“In a billion years or so, it probably will be invisible,” Dr. Condon noted in the November 2, 2016 NRAO Press Release. This indicates, he added, that there could be many more similar objects left in the wake of earlier galactic collisions that astronomers are unable to detect.
The astronomers are going to keep on exploring the Universe, on the hunt for such objects, in their long-term study using the VLBA. Because their project does not depend on time, Dr. Condon continued to explain, they use “filler time” when the telescope is not being used for more time-critical observations that are being conducted by other astronomers.
“The data we get from the VLBA is very high quality. We get the positions of the supermassive black holes to extremely good precision. Our limiting factor is the precision of the galaxy positions seen at other wavelengths that we use for comparison,” Dr. Condon said in the November 2, 2016 NRAO Press Release. With new optical telescopes scheduled to come on line in future years, such as the Large Synoptic Survey Telescope (LSST), he added, they will then have improved images that can be compared with the VLBA images. The astronomers hope that this will enable them to discover more objects like B3 1714+425.
“And also maybe some of the binary supermassive black holes we originally sought,” he continued.
Dr. Condon worked with Dr. Jeremy Darling of the University of Colorado; Dr. Yuri Kovalev of the Astro Space Center of the Lebedev Physical Institute in Moscow, Russia; and Dr. Leonid Petrov of the Astrogeo Center in Falls Church, Virginia. The scientists are reporting their findings in the Astrophysical Journal.
The VLBA is part of the Long Baseline Observatory. It uses ten, 25-meter-diameter dish antennas distributed from Hawaii to St. Croix in the Caribbean. It is operated from the NRAO’s Domenici Science Operations Center in Socorro, New Mexico. All ten antennas work together as a single telescope with great resolving power.