Galaxy Mergers Archives

February 27, 2022February 27, 2022 by Andy Tomaswick

Astronomers see an Enormous Shockwave, 60 Times Bigger Than the Milky Way

Astronomers have a thing for big explosions and collisions, and it always seems like they are trying to one-up themselves in finding a bigger, brighter one. There’s a new entrant to that category – an event so big it created a burst of particles over 1 billion years ago that is still visible today and is 60 times bigger than the entire Milky Way.

October 20, 2021October 20, 2021 by Evan Gough

The Large Magellanic Cloud Stole one of its Globular Clusters

The Milky Way with the Small and Large Magellanic Clouds on the left. Image Credit: ESO/Y. Beletsky. CC 4.0

Astronomers have known for years that galaxies are cannibalistic. Massive galaxies like our own Milky Way have gained mass by absorbing smaller neighbours.

Now it looks like smaller galaxies like the Large Magellanic Cloud have also feasted on smaller neighbours.

June 15, 2021June 15, 2021 by Andy Tomaswick

Rare Triple Galaxy Merger With at Least Two Supermassive Black Holes

One of the best things about that universe is that there is so much to it. If you look hard enough, you can most likely find any combination of astronomical events happening. Not long ago we reported on research that found 7 separate instances of three galaxies colliding with one another. Now, a team led by Jonathan Williams of the University of Maryland has found another triple galaxy merging cluster, but this one might potentially have two active supermassive black holes, allowing astronomers to peer into the system dynamics of two of the universe’s most extreme objects running into one another.

May 12, 2021May 10, 2021 by Paul M. Sutter

Astronomers see a Rare “Double Quasar” in a Pair of Merging Galaxies

Artist's conception of a double quasar. Image credit: ASA, ESA, Joseph Olmsted (STScI)

What’s better than a quasar? That’s right, two quasars. Astronomers have spotted for the first time two rare double-quasars, and the results show us the dynamic, messy consequences of galaxy formation.

February 2, 2021February 2, 2021 by Evan Gough

When Galaxies Collide, Black Holes Don’t Always Get the Feast They Were Hoping for

What happens when galaxies collide? Well, if any humans are around in about a billion years, they might find out. That’s when our Milky Way galaxy is scheduled to collide with our neighbour the Andromeda galaxy. That event will be an epic, titanic, collision. The supermassive black holes at the center of both galaxies will feast on new material and flare brightly as the collision brings more gas and dust within reach of their overwhelming gravitational pull. Where massive giant stars collide with each other, lighting up the skies and spraying deadly radiation everywhere. Right?

Maybe not. In fact, there might be no feasting at all, and hardly anything titanic about it.

February 1, 2021February 1, 2021 by Paul M. Sutter

Galaxy Mergers can Boost Star Formation, and it can Also Shut it Down

It is known today that merging galaxies play a large role in the evolution of galaxies and the formation of elliptical galaxies in particular. However there are only a few merging systems close enough to be observed in depth. The pair of interacting galaxies picture seen here — known as NGC 3921 — is one of these systems. NGC 3921 — found in the constellation of Ursa Major (The Great Bear) — is an interacting pair of disc galaxies in the late stages of its merger. Observations show that both of the galaxies involved were about the same mass and collided about 700 million years ago. You can see clearly in this image the disturbed morphology, tails and loops characteristic of a post-merger. The clash of galaxies caused a rush of star formation and previous Hubble observations showed over 1000 bright, young star clusters bursting to life at the heart of the galaxy pair.

Galaxy mergers are beautiful sights, but ultimately deadly. In the midst of the collision, the combined galaxy will shine brighter than it ever has before. But that glory comes with a price: all those new stars use up all the available fuel, and star formation grinds to a halt.

October 23, 2020October 23, 2020 by Evan Gough

Astronomers Find the Hollowed-Out Shell of a Dwarf Galaxy that Collided With the Milky Way Billions of Years Ago

The Karl Jansky Very Large Array at night, with the Milky Way visible in the sky. Credit: NRAO/AUI/NSF; J. Hellerman

In 2005 astronomers found a dense grouping of stars in the Virgo constellation. It looked like a star cluster, except further surveys showed that some of the stars are moving towards us, and some are moving away. That finding was unexpected and suggested the Stream was no simple star cluster.

A 2019 study showed that the grouping of stars is no star cluster at all; instead, it’s the hollowed-out shell of a dwarf spheroidal galaxy that merged with the Milky Way. It’s called the Virgo Overdensity (VOD) or the Virgo Stellar Stream.

A new study involving some of the same researchers shows how and when the merger occurred and identifies other shells from the same merger.

July 16, 2020July 16, 2020 by Evan Gough

A Stellar Stream of Stars, Stolen from Another Galaxy

The all-sky view that the Gaia survey would have of a simulated Milky-Way-like galaxy. [Credit: Sanderson et al. The Astrophysical Journal, January 6, 2020, DOI: 10.3847/1538-4365/ab5b9d]

Modern professional astronomers aren’t much like astronomers of old. They don’t spend every suitable evening with their eyes glued to a telescope’s eyepiece. You might be more likely to find them in front of a super-computer, working with AI and deep learning methods.

One group of researchers employed those methods to find a whole new collection of stars in the Milky Way; a group of stars which weren’t born here.

November 25, 2019November 25, 2019 by Evan Gough

Astronomers Find a Galaxy Containing Three Supermassive Black Holes at the Center

Not all galaxies are neatly shaped, as this new NASA/ESA Hubble Space Telescope image of NGC 6240 clearly demonstrates. NGC 6240 is the result of three galaxies merging. Image Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

NGC 6240 is a puzzle to astronomers. For a long time, astronomers thought the galaxy is a result of a merger between two galaxies, and that merger is evident in the galaxy’s form: It has an unsettled appearance, with two nuclei and extensions and loops.

September 27, 2019September 27, 2019 by Evan Gough

Astronomers Have Found a Place With Three Supermassive Black Holes Orbiting Around Each Other

The three black holes at the center of three separate galaxies as imaged by Chandra and other telescopes. Image Credit: Credit: X-ray: NASA/CXC/George Mason Univ./R. Pfeifle et al.; Optical: SDSS & NASA/STScI

Astronomers have spotted three supermassive black holes (SMBHs) at the center of three colliding galaxies a billion light years away from Earth. That alone is unusual, but the three black holes are also glowing in x-ray emissions. This is evidence that all three are also active galactic nuclei (AGN,) gobbling up material and flaring brightly.

This discovery may shed some light on the “final parsec problem,” a long-standing issue in astrophysics and black hole mergers.