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Runaway black hole creates a trail of stars

An intergalactic “monster” is hurtling through space, leaving behind a never-before-seen “contrail” of newborn stars. The supermassive black hole weighs as much as 20 million suns and travels so quickly that if it were in our solar system, it could travel from Earth to the Moon in just 14 minutes. 

The trail it has left behind is almost 200,000 light-years long, twice the diameter of our Milky Way galaxy, and is the result of a rare game of galactic billiards among three massive black holes.

Instead of gobbling up stars ahead of it, as a cosmic Pac-Man would, this supermassive black hole is plowing into gas in front of it to trigger new star formation along a narrow corridor. 

Image Credit: ARTWORK: NASA, ESA, Leah Hustak (STScI)

“We think we’re seeing a wake behind the black hole where the gas cools and is able to form stars. So, we’re looking at star formation trailing the black hole,” explained Pieter van Dokkum of Yale University.

The black hole is traveling so fast that it is unable to stop for a snack, so it triggers new star formation as it moves through gas. This phenomenon has never been seen before, but it was captured by accident using NASA’s Hubble Space Telescope. The trail must have lots of new stars, given that it is almost half as bright as the host galaxy it is linked to.

The black hole lies at one end of the column, which stretches back to its parent galaxy. There is a remarkably bright knot of ionized oxygen at the outermost tip of the column. Researchers believe gas is probably being shocked and heated from the motion of the black hole hitting the gas, or it could be radiation from an accretion disk around the black hole.

“This is pure serendipity that we stumbled across it,” said van Dokkum. He was initially looking for globular star clusters in a nearby dwarf galaxy when he stumbled upon the trail. “I was just scanning through the Hubble image, and then I noticed that we have a little streak. I immediately thought, ‘oh, a cosmic ray hitting the camera detector and causing a linear imaging artifact.’ When we eliminated cosmic rays, we realized it was still there. It didn’t look like anything we’ve seen before.”

Van Dokkum and his team did follow-up spectroscopy with the W. M. Keck Observatories in Hawaii because the phenomenon was so unusual. He describes the star trail as “quite astonishing, very, very bright and very unusual.” This led to the conclusion that he was looking at the aftermath of a black hole flying through a halo of gas surrounding the host galaxy.

This intergalactic phenomenon is likely the result of multiple collisions of supermassive black holes. According to astronomers, the first two galaxies merged, perhaps 50 million years ago. This brought together two supermassive black holes at their centers. They whirled around each other as a binary black hole.

Then another galaxy came along with its own supermassive black hole. This led to a chaotic and unstable configuration, with the three black holes mixing it up. 

One of the black holes robbed momentum from the other two and was thrown out of the host galaxy. The original binary may have remained intact, or the new interloper black hole may have replaced one of the two that were in the original binary and kicked out the previous companion.

The binary black holes and the single black hole displayed opposite directions when the latter departed. Researchers have spotted a feature on the opposite end of the host galaxy, which they suspect to be the runaway binary black hole. 

Supporting this notion is the absence of any active black hole at the center of the galaxy. To confirm the presence of the black hole, NASA plans to conduct additional observations with the James Webb Space Telescope and Chandra X-ray Observatory.

NASA’s upcoming Nancy Grace Roman Space Telescope boasts a wide-angle view of the universe with Hubble’s superior resolution. The telescope is designed for surveying, and scientists anticipate that it may detect more rare and unlikely “star streaks” in other parts of the universe. 

According to van Dokkum, machine learning algorithms will likely be necessary to identify these peculiar shapes among the vast amounts of astronomical data collected.

More about black holes

Black holes are some of the most fascinating objects in the universe. They are formed when massive stars collapse under their own gravity, creating a region of space where the gravitational pull is so strong that nothing, not even light, can escape. This phenomenon is called the event horizon, which is the boundary of the black hole from which no information can be retrieved.

Black holes come in different sizes, ranging from a few times the mass of our Sun to billions of times its mass. The smaller ones are called stellar black holes, while the larger ones are known as supermassive black holes, which are found at the centers of most galaxies, including our Milky Way.

One of the most interesting properties of black holes is that they warp space and time around them. This effect is known as gravitational lensing, which causes light to bend as it passes near a black hole. This phenomenon has been observed by astronomers, and it has been used to study the properties of black holes and the galaxies in which they reside.

Another remarkable property of black holes is that they emit radiation, called Hawking radiation, named after the physicist Stephen Hawking, who first predicted its existence. This radiation is emitted from the vicinity of the event horizon and causes the black hole to lose mass over time.

Despite their fascinating nature, black holes are still not fully understood, and there is much that remains unknown about them. However, their study has been a significant field of research in astrophysics, and new discoveries are continually being made.

In summary, black holes are one of the most intriguing objects in the universe, and their study has provided us with insights into the workings of the cosmos. However, there is still much to learn about them, and they continue to be a source of fascination for astronomers and the general public alike.

The research is published in The Astrophysical Journal Letters.

More about the Hubble Space Telescope

The Hubble Space Telescope (HST) is a giant orbiting observatory that has transformed our understanding of the universe. Launched in 1990, the HST is a joint project of NASA and the European Space Agency (ESA) and is named after the famous astronomer Edwin Hubble.

The telescope orbits the Earth at an altitude of about 340 miles (547 kilometers) and has a diameter of 94.5 inches (2.4 meters). It is equipped with a suite of scientific instruments that allow it to observe the universe in visible, ultraviolet, and infrared light.

One of the most significant contributions of the HST is its role in determining the age of the universe. Using its powerful instruments, the HST has observed distant galaxies and measured their distances and velocities. This information has allowed astronomers to calculate the expansion rate of the universe and estimate its age.

The HST has also provided stunning images of distant galaxies, nebulae, and other celestial objects. Its images have not only been scientifically significant but also captivating to the public, raising awareness and interest in astronomy.

The HST has undergone several upgrades and repairs since its launch, including the installation of new instruments and the replacement of aging parts. These upgrades have extended the life of the telescope and allowed it to continue making groundbreaking discoveries.

In summary, the Hubble Space Telescope has revolutionized our understanding of the universe and continues to provide us with invaluable information about the cosmos. Its observations have inspired scientists and the public alike, reminding us of the wonder and beauty of our universe.


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