The Andromeda and Milky Way galaxies merge

See bigger. | Real size of the Andromeda galaxy? Yes. This image really shows what the night sky would look like if the Andromeda galaxy – the neighboring galaxy – were brighter. Original moon background photo by Stephen Rahn. Andromeda Galaxy image via Nasa. Photo composed by Tom Buckley-Houston. The composite appeared on Reddit few years ago. Not convinced? Here is a similar image via APOD. As the Andromeda-Milky Way merger continues, the Andromeda Galaxy will appear larger and larger in our sky.

The merger of the Milky Way and Andromeda has begun

The Andromeda Galaxy, the closest spiral galaxy to our Milky Way, is not noticeable in our night sky unless you look for it. Under dark skies, however, you can see it without optical aid, but only as a faint blurry patch of light. But one day, in the distant future, Andromeda will shine in our sky, growing bigger and bigger… as it gets closer to us. And even though the two galaxies are still 2.5 million light-years apart, the eventual merger of our two galaxies has, in fact, already begun.

Galaxy near the gibbous moon.
See bigger. | Here is another composite image showing the actual size in our sky of the Andromeda Galaxy. This one is from astrophotographers Adam’s Block and Tim Puckett. It was the Astronomy photo of the day for August 1, 2013.

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The great expanse of galactic halos

The Andromeda galaxy is currently moving towards our Milky Way at a speed of about 70 miles (113 km) per second. With that in mind, our merger will occur in five billion years. But, in August 2020, the Peer-reviewed Astrophysical Journal published new search revealing that the collision between our galaxies is already underway.

News from the Andromeda Galaxy came from AMIGA projectwho uses the The Hubble Space Telescope to observe the distant surroundings of the Andromeda galaxy. AMIGA stands for Absorption Map of Ionized Gas in Andromeda. Nasa called him:

… the most comprehensive study of a halo surrounding a galaxy.

The Andromeda Galaxy, our Milky Way and other galaxies are all shrouded in a large envelope – called a galactic halo – which is made up of gas, dust and stray stars. Galaxy halos are faint, so faint, in fact, that detecting them is no small feat. These astronomers measured the size of the Andromeda Galaxy’s halo by examining how well it absorbed light from background quasars. They were surprised to find that the halo of the Andromeda galaxy extends a lot, many far beyond its visible limits.

Indeed, it extends up to half the distance to our Milky Way (1.3 million light-years) and even further in other directions (up to 2 million years). -light).

Do the halos still touch each other?

So, does this mean that the halos of the Andromeda and Milky Way galaxies are touching?

It turns out that from our vantage point inside the Milky Way, we can’t easily measure the characteristics of our galaxy’s halo. However, since the two galaxies are so similar in size and appearance, scientists assume that the Milky Way’s halo would also be similar.

In other words, it’s the faint halos of the galaxies that actually seem to have started touching. So, in a way, the collision between our two galaxies has already begun.

Visualize Andromeda’s halo in our sky

Huge blurry purple sphere against star field with many pink dots inside and around it.
Observing 43 background quasars, scientists used the Hubble Space Telescope to map the halo of the spiral galaxy closest to our Milky Way, the Andromeda Galaxy. Light from these very distant quasars (emission from very bright galaxies fed by a central supermassive black hole) is absorbed on its journey through the halo. By studying the change in absorption depending on where you look in the halo, scientists not only see the large extent of the halo, but also its composition. Artwork via Nasa/ ESA/ E. Wheatley (Space Telescope Science Institute).
Earth's night sky above a ridgeline, with a huge purple halo around a galaxy.
This illustration shows what the Andromeda galaxy is gaseous Halo might look like if it were visible to humans on Earth. At 3 times the size of the Big Dipper, the halo would easily be the largest feature in the night sky, according to Nasa. Recent measurements of the halo show that the collision between the Milky Way and Andromeda galaxies has already begun. Picture via Nasa/ ESA/ J. DePasquale and E. Wheatley (STScI)/ Z. Levay.

So what will the Andromeda merger look like?

NASA released the images below in 2012. These are artistic conceptions of what someone on Earth might see as the Andromeda Galaxy hurtles towards us.

The depictions below are based on careful measurements of the motion of the Andromeda Galaxy by the Hubble Space Telescope, with computer modeling of the inevitable collision between the two galaxies. Furthermore, a series of studies published in 2012 showed that – rather than staring at each other, as merging galaxies sometimes do – our Milky Way Galaxy and the Andromeda Galaxy will merge into made to form a single large galaxy. ellipticalWhere shaped like a soccer ballgalaxy.

Roeland van der Marelastronomer at the Space Telescope Science Institute, says Discover the magazine in February 2022:

Whether it’s a head-on collision or more of a peek, it doesn’t really affect the end result.

And it’s a new giant elliptical galaxy.

Eight panels with views of the night sky ranging from today through a chaos of stars to a smooth background glow.
See bigger. | The merger between our Milky Way and neighboring Andromeda.
1st row, left: Today.
1st row, right: In 2 billion years, the disk of the approaching Andromeda galaxy is noticeably larger.
2nd row, left: In 3.75 billion years, Andromeda fills the field of vision.
2nd row, right: In 3.85 billion years, the sky will ignite with the formation of new stars.
3rd row, left: In 3.9 billion years, star formation will continue.
3rd row, right: In 4 billion years, Andromeda stretches in tide and the Milky Way deforms.
4th row, left: In 5.1 billion years, the nuclei of the Milky Way and Andromeda appear as a pair of bright lobes.
4th row, right: Over 7 billion years, the merged galaxies form a huge elliptical galaxy, its bright core dominating the night sky.
Picture via Nasa/ ESA/ Z. Levay and R. van der Marel, STScI/ T. Hallas/ A. Mellinger.

Another video of the Andromeda fusion

However, the Milky Way and Andromeda galaxies will not be the only ones involved in this merger. As shown in the video below, the other large galaxy in our Local Group of galaxies, i.e. M33, aka the Triangle Galaxy, will also play a role.

In the video below, you will recognize the Triangle galaxy as the smallest object near the Andromeda and Milky Way galaxies. Although the Triangle galaxy is unlikely to join in the merger, it could nevertheless at some point strike our Milky Way as it is engaged in a grand cosmic dance with the two larger galaxies.

What happens to stars and planets when galaxies merge?

across the universe, galaxies collide with each other. Astronomers observe galactic collisions – or their aftermath – using powerful telescopes. In some ways, when a galactic merger takes place, the two galaxies are like ghosts; they simply cross each other. This is because the stars inside galaxies are separated by such great distances. So stars themselves don’t usually collide when galaxies merge.

That said, stars in the Andromeda Galaxy and our Milky Way will be affected by the merger. The Andromeda Galaxy contains approximately one trillion stars. Meanwhile, the Milky Way has about 300 billion stars. Stars from both galaxies will be launched into new orbits around the newly merged galactic center. For example, according to the scientists involved in the 2012 studies:

It is likely that the sun will be propelled into a new region of our galaxy…

And yet, they said,

…our Earth and our solar system are in no danger of being destroyed.

Will humanity see the Andromeda merger?

So what about life on Earth? Will Earth Life Survive the Meltdown? Well, the sun will eventually become a red giant in about 7.5 billion years, when it increases in size and consumes the Earth. But even before that, the luminosity, or intrinsic luminosity, of the sun will increase. This will happen, ultimately, in a timeline of about four billion years.

As solar radiation reaching the Earth increases, the Earth’s surface temperature will increase. We could be experiencing a runaway greenhouse effect, similar to the one currently occurring on neighboring planet Venus. So there is a good change that life on earth will no longer be there when the merger ends.

But by then, perhaps some terrestrial inhabitants will have become spatial. Perhaps we will have left Earth, and even our solar system. We can still get the sight of Andromeda crashing into the Milky Way, just from a slightly different vantage point.

Read more: Hubble shows Milky Way is destined for head-on collision

Conclusion: the merger of the Milky Way and Andromeda has already begun. The two spiral galaxies will form a giant elliptical galaxy in 5 billion years.

Source: AMIGA Project: The Circumgalactic Environment of Andromeda*

Via Discover the magazine

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