This is interesting. Around 11:21 in the video below you can see the projected movement of stars in our galaxy, stars we cannot see with the naked eye. When they “turn time on” we see that some move together, but also they are going at all different rates and in different directions.
From available data we know that another star is heading for ours right now. In an estimated 1.2 million years (so the video below says) Gliese 710 is going to fly by our solar system, most likely kicking a bunch of stuff from our Ort cloud into the inner solar system.
Predictions say Gliese 710’s flyby will cause us to see several comets with the naked eye each year and the star itself will be brighter than the planet Mars as it comes by.
Gliese 710 or HIP 89825 is an orange 0.6 star in the constellation Serpens Cauda. It is projected with a reasonable probability to have a close encounter with the Sun within the next 15 million years. … It will then reach a similar brightness to the brightest planets, perhaps reaching an apparent visual magnitude of about −2.7 (brighter than Mars at opposition). Maximum total proper motion will peak around one arc minute per year, whose apparent motion will be able to be noticed over a human lifespan.
Then a few billion years after that things get even busier as the entire Andromeda galaxy will collide with our Milky Way galaxy, resulting in a great night sky… except we will need to have moved our planet away from our sun a bit to avoid an eartly doom by then. (That seems not impossible given the current rate of human technological advance … as long as we can keep progressing.)
… compared to most galaxies, the Milky Way has had a very quiet 10 billion years or so. But the new study suggests we’re only a few billion years from that quiet period coming to an end. A collision with a nearby dwarf galaxy should turn the Milky Way into something more typical looking—just in time to have Andromeda smack into it.
Scientists say it will happen four billion years from now. NASA astronomers say they can now predict the time of this collision of titan galaxies with certainty. They base this number on painstaking NASA Hubble Space Telescope measurements of the motion of the Andromeda galaxy, which is also called M31. The scientists said:
The galaxy is now 2.5 million light-years away, but it is inexorably falling toward the Milky Way under the mutual pull of gravity between the two galaxies and the invisible dark matter that surrounds them both.
Here’s a video showing how it might look: Night sky as Milky Way and Andromeda galaxies merge
This image represents Earth’s night sky in 3.75 billion years. The Andromeda galaxy (left) will fill our field of view then, astronomers say, as it heads toward a collision with our Milky way galaxy. Image Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger …
… In fact, our solar system is going to outlive our galaxy. At that point, the sun will not yet be a red giant star – but it will have grown bright enough to roast Earth’s surface. Any life forms still there, though, will be treated to some pretty spectacular cosmic choreography.
Currently, Andromeda and the Milky Way are about 2.5 million light-years apart. Fueled by gravity, the two galaxies are hurtling toward one another at 402,000 kilometers per hour. But even at that speed, they won’t meet for another four billion years. Then, the two galaxies will collide head-on and fly through one another, leaving gassy, starry tendrils in their wakes. For eons, the pair will continue to come together and fly apart, scrambling stars and redrawing constellations until eventually, after a billion or so years have passed, the two galaxies merge.
How much will our night sky change while we humans still roam the earth?