Hubble peers through the mysterious shells of this gigantic elliptical galaxy

Take a good look at the latest image provided by the Hubble Space Telescope. It shows a huge elliptical galaxy called NGC 474 which lies about 100 million light-years away from us.

At about two and a half times larger than our Milky Way, it really is a monster. Notice its odd structure – mostly featureless and almost round, but with layered shells wrapped around the central core.

Astronomers want to know what caused these shells. The answer could be in what this galaxy represents: a vision of the future Milky Way and the Andromeda galaxy.

The Fate of the Milky Way: When Galaxies Collide!

Galaxies change over long time scales. More than 13 billion years ago, the first were small fragments of matter. They merged to form larger and larger structures. This process of merging and cannibalization continues to this day.

It influences the “look” of a galaxy and adds variety to its stellar populations. Our own Milky Way is part of this process. Currently, it is cannibalizing the Sagittarius dwarf galaxy.

It has also merged or swallowed between 5 and 11 smaller ones during its lifetime.

Astronomers already know that the Milky Way will continue to be part of the galaxy merging process.

In about 4.5 to 5 billion years, it will begin to merge with the neighboring Andromeda galaxy (M31). Of course, M31 will have come very close to us in the meantime.

As a bonus, the Triangle Galaxy (M33) could also participate in this galactic dance.

For those of you keeping track of these things, it will happen when the Sun runs out of hydrogen in its core and begins to evolve into a red giant. So it will be an interesting time. Mark your calendars.

NGC 474 predicts the future of the Milky Way

(NASA et al.)

Full image credit: NASA, ESA and D. Carter/Liverpool John Moores University; Image processing: G. Kober/NASA Goddard/Catholic University of America

NGC 474 looks a lot like what astronomers think the Milky Way and Andromeda will look like after they merge. They will no longer be two beautiful spirals. Instead, their gravitational interaction will produce a nearly featureless elliptical galaxy.

How will this be? As the two galaxies approach each other, the strong gravity of each will distort their shapes. Giant streamers of gas and dust will be extracted from each galaxy. There might even be central shells of material, as in NGC 474.

In addition to all this activity, there is another characteristic of a merge: star nodes. These are star formation sites that occur as a result of a merger.

The activity pushes clouds of gas and dust together, eventually creating piles of hot young stars. This will happen as long as there is enough material available for starbirth nurseries.

Eventually, the burst of star birth will slow down and stop. The resulting new galaxy will take on a rather boring elliptical shape.

That, in a nutshell, is what happened to NGC 474. And that’s the fate of Milkdromeda: a (probably) featureless elliptical that was once two beautiful spiral galaxies.

Explaining these shells in NGC 474

In the case of NGC 474, astronomers have a few theories as to why it has these weird shells. One idea is that it interacted with another galaxy billions of years ago. This created the seashells in a process similar to throwing a rock into a pond and watching the ripples roll away from it.

NGC 474 is not the only one to have shells caused by collisions. About 10% of all ellipticals have these features. This could be a clue to their formation and fusion histories that astronomers will study.

There is another interesting thing about these shell galaxies. While most ellipticals are clustered, these eccentrics take up relatively empty stretches of space.

It is possible that they cannibalized neighboring galaxies and thus emptied their neighborhoods of any galactic competition.

Other theories about NGC 474

SpiralGalaxyAndEllipticalGalaxyNGC474NGC 474 next to spiral galaxy NGC 470. (DES et al.)

Full image credit: DES/DOE/Fermilab/NCSA & CTIO/NOIRLab/NSF/AURA Acknowledgements: Image processing: DES, Jen Miller (NSF Gemini Observatory/NOIRLab), Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin

It is also possible for NGC 474 to take gas away from a neighbor called NGC 470.

Another idea is that the shells could be caused by a collision with a very gas-rich galaxy. Not only did they meet once, but they had a second collision which led to their eventual merger.

The shells are proof of this long merged galaxy. Hubble’s view gives a more detailed look at this central region and these mysterious shells.

This article was originally published by Universe today. Read it original article.

#Hubble #peers #mysterious #shells #gigantic #elliptical #galaxy

Leave a Comment

Your email address will not be published. Required fields are marked *