NGC 4753 is a prime example of what happens after galaxies merge. It looks like a twisted mess, with dust lanes surrounding a huge galactic core. Astronomers have long wondered what happened to this galaxy, but clear new images created by the Gemini South telescope can finally explain its troubled past. Ta.
Officially, NGC 4753 is classified as a “peculiar” galaxy due to its strange appearance. However, like other survivors of galactic mergers and acquisitions, it has likely had several “shapes” throughout its history. Most galaxies are classified as spiral galaxies, elliptical galaxies, lenticular galaxies, or irregular galaxies. Astronomers suspect that this object was once a lenticular object with a sizable disk, rather than something like a spiral arm. Then, over a billion years ago, it encountered and became entangled with a neighboring dwarf galaxy. A team led by Indian University astronomer Tom Steiman Cameron studied this galaxy in detail to understand how it came to be the way it is today. “Galaxies that swallow another galaxy often look like train wrecks, and this is a train wreck galaxy,” he said.
NGC 4753 is located approximately 60 million light-years away in the Virgo Galaxy Cluster. It lies within its own small cluster of galaxies called the NGC 4753 group. The galaxy itself appears to have a shell of dark matter, with about 1,000 globular clusters orbiting its center. Although its unique dust lane first attracted the attention of astronomers in his 20th century, the galaxy itself was discovered by William Herschel in his 1784 year.
Galactic Mergers and Acquisitions
Galaxies have been merging throughout the history of the universe. First, small pieces of galaxies mixed with neighboring galaxies to form larger galaxies. That process continued, producing the amazing variety of galactic forms we see today. When galaxies meet like this, stars and matter mix. Gravity scrapes the galaxy, and the shock waves trigger a wave of star birth. This makes galaxies very dynamic objects, changing over time as they meet and mix with neighboring galaxies.
We see this process going on throughout the universe. Our Milky Way galaxy is the result of numerous galaxy mergers since it began forming about 13 billion years ago. Each collision injected new stars, interstellar gas, and dust, changing the galaxy’s appearance. Today, the Milky Way is a bar-like spiral, but in the early universe it began as an indistinct mass of stars, gas, and dust. The history of mergers continues even today. Astronomers are tracking our galaxy swallowing several smaller galaxies, including Sagittarius Dwarf. Furthermore, the Milky Way and Andromeda galaxies will merge in about 5 billion years. In the process, the shape also changes radically, creating a vast galaxy known as Milk Dromeda.
The story of NGC 4753’s galactic merger
When NGC 4753 began its cosmic dance, it tangoed with a gas-rich dwarf galaxy. A burst of star formation caused by the collision (and an influx of gas) injected large amounts of dust into this region. The galaxy followed a spiral path leading to the collision, which smeared the dust into the disk. Ultimately, this activity gave the galaxy its unique appearance. “For a long time, no one knew what to make of this strange galaxy,” Steiman-Cameron said. “But by starting with the idea that the accreted material is smeared into a disk and analyzing its three-dimensional geometry, the mystery was solved. Thirty years later, this highly detailed image by Gemini South I’m incredibly excited now to see it.”
Steiman-Cameron and his team explain this galaxy’s peculiarity with a phenomenon known as “differential precession.” Precession occurs when the axis of rotation of a rotating object, such as a spinning top, changes orientation. Differential means that the rate of precession is different depending on the radius. For the dusty accretion disk orbiting around the galactic nucleus in this collision, the precession speed is faster toward the center and slower near the edges. The galaxy’s wobble-like motion is due to the angle at which NGC 4753 and its former dwarf companion collided. The result was a strongly twisted dust lane running through the galaxy.
Impact on other unusual galaxies
Interestingly, this galaxy certainly looks strange enough in Gemini’s images, but it’s all a matter of perspective. We are looking at it from the side. By doing so, you can find dust lanes and other features within the disk.
However, if you could fly directly to the “north” of NGC 4753 in a spacecraft and get a “top-down” view, it would look much like a standard spiral galaxy. Now that astronomers know its history of galactic mergers, they can conduct further research to understand the interaction of its stellar population and their strange dust lanes. And that history may go a long way toward explaining the appearance of other “strange” galaxies in the universe.