Milky Way ties with neighbor in galactic arms race

February 14, 2018, International Centre for Radio Astronomy Research
The Milky Way and Andromeda prior to the merger. Credit: ICRAR

Astronomers have discovered that our nearest large neighbour, the Andromeda galaxy, is roughly the same size as the Milky Way. It had been thought that Andromeda was two to three times the size of the Milky Way, and that our own galaxy would ultimately be engulfed by our supposedly bigger neighbour. But the latest research, published today, evens the score between the two galaxies.

The study found the weight of the Andromeda is 800 billion times heavier than the sun, on par with the Milky Way. Astrophysicist Dr Prajwal Kafle, from the University of Western Australia node of the International Centre for Radio Astronomy Research, said the study used a new technique to measure the speed required to escape a galaxy. "When a rocket is launched into space, it is thrown out with a speed of 11 km/s to overcome the Earth's ," he said. "Our home galaxy, the Milky Way, is over a trillion times heavier than our tiny planet Earth so to escape its gravitational pull we have to launch with a speed of 550 km/s. We used this technique to tie down the mass of Andromeda."

Dr Kafle said the research suggests scientists previously overestimated the amount of dark matter in the Andromeda galaxy. "By examining the orbits of high stars, we discovered that this galaxy has far less than previously thought, and only a third of that uncovered in previous observations," he said. The Milky Way and Andromeda are two giant spiral galaxies in our local Universe, and light takes a cosmologically tiny two million years to get between them.

With Andromeda no longer considered the Milky Way's big brother, new simulations are needed to find out what will happen when the two eventually collide. Dr Kafle used a similar technique to revise down the weight of the Milky Way in 2014, and said the latest finding had big implications for our understanding of our nearest galactic neighbours. "It completely transforms our understanding of the local group," he said.

The Milky Way and Andromeda during the merger. Credit: ICRAR
"We had thought there was one biggest galaxy and our own Milky Way was slightly smaller but that scenario has now completely changed. It's really exciting that we've been able to come up with a new method and suddenly 50 years of collective understanding of the local group has been turned on its head."

University of Sydney astrophysicist Professor Geraint Lewis said it was exciting to be at a time when the data was getting so good. "We can put this gravitational arms race to rest," he said.

In about 5 billion years time, nearby massive galaxy Andromeda will merge with our own galaxy, the Milky Way. There haven't been any large mergers with our galaxy recently, but we can see the remnants of galaxies that have previously been snacked on by the Milky Way. We're also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds sometime in the future.

This simulation shows what will happen when the Milky Way and Andromeda get closer together and then collide, and then finally come together once more to merge into an even bigger galaxy. Credit: Simulation Credit: Prof Chris power (ICRAR-UWA), Dr Alex Hobbs (ETH Zurich), Prof Justin Reid (University of Surrey), Dr Dave Cole (University of Central Lancashire) and the Theoretical Astrophysics Group at the University of Leicester. Video Production Credit: Pete Wheeler, ICRAR.

Explore further: Distant galaxy group contradicts common cosmological models, simulations

Related Stories

Hubble sees spiral in Andromeda

February 10, 2017

The Andromeda constellation is one of the 88 modern constellations and should not be confused with our neighboring Andromeda Galaxy. The Andromeda constellation is home to the pictured galaxy known as NGC 7640.

Astronomers measure weight of galaxies, expansion of universe

July 30, 2014

Astronomers at the University of British Columbia have collaborated with international researchers to calculate the precise mass of the Milky Way and Andromeda galaxies, dispelling the notion that the two galaxies have similar ...

Galaxy orbits in the local supercluster

December 8, 2017

A team of astronomers from Maryland, Hawaii, Israel, and France has produced the most detailed map ever of the orbits of galaxies in our extended local neighborhood, showing the past motions of almost 1400 galaxies within ...

Fermi finds possible dark matter ties in Andromeda galaxy

February 21, 2017

NASA's Fermi Gamma-ray Space Telescope has found a signal at the center of the neighboring Andromeda galaxy that could indicate the presence of the mysterious stuff known as dark matter. The gamma-ray signal is similar to ...

Recommended for you

NASA Learns More About Interstellar Visitor 'Oumuamua

November 14, 2018

In November 2017, scientists pointed NASA's Spitzer Space Telescope toward the object known as 'Oumuamua—the first known interstellar object to visit our solar system. The infrared Spitzer was one of many telescopes pointed ...

Gravitational waves from a merged hyper-massive neutron star

November 14, 2018

For the first time astronomers have detected gravitational waves from a merged, hyper-massive neutron star. The scientists, Maurice van Putten of Sejong University in South Korea, and Massimo della Valle of the Osservatorio ...

The dance of the small galaxies that surround the Milky Way

November 14, 2018

An international team led by researchers from the IAC used data from the ESA satellite Gaia to measure the motion of 39 dwarf galaxies. This data gives information on the dynamics of these galaxies, their histories and their ...

Galaxies like Russian dolls

November 13, 2018

Jairo Méndez Abreu and Adriana de Lorenzo-Cáceres, researchers at the Instituto de Astrofísica de Canarias (IAC), have discovered a peanut-shaped structure in the inner bar of a double-barred galaxy close to the Milky ...

6 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Benni
1 / 5 (12) Feb 14, 2018
"By examining the orbits of high speed stars, we discovered that this galaxy has far less dark matter than previously thought, and only a third of that uncovered in previous observations,"

Ya just gotta love statements like this. Somewhere in the past they claim to have observed a specific quantity of Dark Matter, then years later they have observed it to be only a 1/3 of what was uncovered in previous observations.

How can things of which pictures cannot be taken be described as having been OBSERVED? Well, these are cosmologists & we know cosmologists can't do Differential Equations so we give them a pass. Right Schneibo?
691Boat
5 / 5 (5) Feb 14, 2018
"By examining the orbits of high speed stars, we discovered that this galaxy has far less dark matter than previously thought, and only a third of that uncovered in previous observations,"

Ya just gotta love statements like this. Somewhere in the past they claim to have observed a specific quantity of Dark Matter, then years later they have observed it to be only a 1/3 of what was uncovered in previous observations.

How can things of which pictures cannot be taken be described as having been OBSERVED? Well, these are cosmologists & we know cosmologists can't do Differential Equations so we give them a pass. Right Schneibo?

You have a picture of a photon I could look at? thanks.
nrauhauser
5 / 5 (3) Feb 14, 2018
We just recently became aware of dark matter and we wrestle with what it might be and how to measure it. Given that we're peering into cosmological time and space, it is to be expected that we'll see changes in estimates. Every new telescope opens new vistas, every retired and underutilized telescope is stalked by edgy astronomers with seemingly strange methods they want to test. It's an exciting time to be alive, dunno why you're such a wet blanket, Benni.
arcmetal
3.8 / 5 (4) Feb 14, 2018
"How can things of which pictures cannot be taken be described as having been OBSERVED? Well, these are cosmologists & we know cosmologists can't do Differential Equations so we give them a pass. Right Schneibo?"


I have also noticed that some have a problem with understanding the difference between "observations" and "conclusions".
TheGhostofOtto1923
5 / 5 (3) Feb 15, 2018
How can things of which pictures cannot be taken be described as having been OBSERVED? Well, these are cosmologists & we know cosmologists can't do Differential Equations so we give them a pass. Right Schneibo?
Benni's toe observes a chair in the dark as he gets up to take a pee in the middle of the night. Hurts dont it Benni? No photos needed.

Reminds me why I put this person on ignore a long time ago.
Benni
1 / 5 (3) Feb 15, 2018
Reminds me why I put this person on ignore a long time ago
.......aw c'mon ghosty, you didn't? Do you realize how much you haven't learned since you did this?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.