Practice English Speaking&Listening with: Milky Way Versus Andromeda As Seen from Earth

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Astronomers have used the Hubble Space Telescope to forecast a future cosmic pile up: the titanic

collision of the Milky Way and the Andromeda galaxy in about four billion years time.

The Andromeda Galaxy, some 2.2 million light-years away, is the closest spiral galaxy to our

home, the Milky Way. For around a century, astronomers have known it is moving towards

us, but whether or not the two galaxies would actually collide, or simply fly past each

other, remained unclear. Now, a team of astronomers has used the Hubble Space Telescope to shed

light on this question, by looking at the motion stars in the Andromeda Galaxy.

We wanted to figure out how Andromeda was moving through space. So in order to do that

we measured the location of the Andromeda stars relative to the background galaxies.

In 2002 they were in one place, and in 2010 they were in a slightly different place. And

that allowed us to measure the motion over a period of eight years.

The motion is actually incredibly subtle, and not obvious to the human eye, even when

looking at Hubble's sharp images. However, sophisticated image analysis revealed tiny

movements that the scientists were able to project into the future.

Based on these findings, it is finally possible to show what will happen to the Milky Way

over the next eight billion years, as the galaxies drift closer, then collide and gradually

merge into a single, larger, elliptical galaxy with reddish stars. And yet the Solar System

should in fact survive this huge crash.

The reason we think that our Solar System will not be much affected by this collision

between the Milky Way and Andromeda is that galaxies are mostly empty space.

Even though our galaxy, as well as the Andromeda Galaxy, has a hundred billion stars in it,

they are very far apart. So if two galaxies actually collide with each other, the stars

basically pass right between each other and the chance of two stars directly hitting each

other is really, really small. So the likelihood that our Solar System will be directly impacted

by another star, for example, in Andromeda as we collide with it is really, really small.

Well, if life is still present on Earth when this happens, the changes in the sky will

be quite spectacular. Now they will be very very slow because the timescales on the scales

of galaxies in the Universe are very very long. So you have to think, millions of years

but even then over these timescales over millions of years, we will see big changes. If we wait

a few billion years, Andromeda will be huge on the sky. It will be as big as our Milky

Way because we'll be very close to it.

And then later, when the galaxies merge, the merged remnant of the Milky Way Galaxy and

Andromeda will look more like an elliptical galaxy and we'll be sitting right in it.

So the view of the Milky Way on the night sky will be completely gone and this band

of light will be replaced by a more spheroidal distribution of light.

And so, the Sun, born in the Milky Way almost 5 billion years ago will end its life in a

new orbit, as part of a new galaxy.

The Description of Milky Way Versus Andromeda As Seen from Earth