The Hubble Space Telescope has provided a new image. It shows a huge elliptical galaxy that is 100 million light-years away from us.
It is about two and a half times larger than the Milky Way. The structure is mostly featureless and nearly round, but with layers of shells around the central core.
Astronomers want to know what happened. The answer might be in the future vision of the future Milky Way and the AndromedaGalaxy.
Galaxies change over time. The first ones were very small. They formed larger structures. The process of merging and cannibalization is still going on.
It adds variety to its stellar populations. The process includes our own Milky Way. It is cannibalizing the Sagittarius DwarfGalaxy.
Between 5 and 11 smaller ones have been merged with it.
The Milky Way will continue to be part of the merger process.
It will start to merge with the nearby M31 about 4.5 to 5 billion years from now. M31 will have moved a lot closer to us in the intervening time.
The TriangulumGalaxy might also participate in this dance.
This will happen when the Sun runs out of hydrogen in its core and becomes a red giant. It will be an interesting time. You should mark your calendars.
NASA et al.
The image was taken by NASA, the European Space Agency, and John Moores University.
Astronomers think that the stars will look similar after their merger. They will not be two beautiful spirals anymore. They will produce an elliptical galaxy that is almost featureless.
How will that happen? The shapes of the two galaxies will be distorted by the strong gravity of each one. Giant streamers of gas and dust will be pulled out of each universe. There might be central shells of material.
There is one other hallmark of a merger, and that is starburst knots. They are sites of star formation after a merger.
Clouds of gas and dust are pushed together by the activity. As long as there is enough material available to the starbirth nurseries, that will happen.
The burst of starbirth will eventually stop. A boring-looking elliptical shape will be assumed by the new galaxy.
That is what happened to NGC 474. Milkdromeda is a featureless elliptical that used to be two beautiful spiral galaxies.
There are a few theories about why the shells are odd. One idea is that it was in contact with another galaxy billions of years ago. The shells were created in a similar way to throwing a rock into a pond.
There are other shells with collision-caused ones. About 10 percent of ellipticals have these features. That could be a clue to their history.
There is another interesting thing about the shelled galaxies. The odd ones occupy relatively empty stretches of space.
They might have been able to cannibalize nearby galaxies and thus cleared out their neighborhoods.
There is a spiral galaxy called NGC 470.
The image was processed by Jen Miller (Gemini Observatory/NSF).
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The shells might have been caused by a collision with a very gas-rich galaxy.
The evidence is the shells. Hubble gives a more detailed look at that central region.
The article was published by Universe Today. The original article is worth a read.
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