Hello Space Fans and welcome to another edition of Space Fan News.
In this episode, new measurements from ESA’s Gaia Spacecraft have adjusted predictions
for when and how the Milky Way will collide with the nearby Andromeda galaxy.
Turns out it’s not gonna happen the way we thought, or when we thought.
Stick around.
Most of you who’ve been watching SFN for a while now are well aware that our galaxy,
the Milky Way, is on a collision course with the Andromeda Galaxy, a sister galaxy much
like our own, both are giant spiral galaxies and while astronomers used to think that the
Andromeda galaxy was about three times more massive than ours,recently they’ve learned
that both galaxies have about 800 billion stars worth of mass in them.
That’s what so great about better observations using better techniques and telescopes, they
allow us to refine what we know is going on in the night sky.
So thanks to the brand Gaia space telescope operated by the European Space Agency and
it’s improved measurements of billions of stars, astronomers are now refining the details
of the upcoming collision between our two galaxies.
In case you didn’t know, the Andromeda galaxy is heading our way and was expected to collide
with our galaxy in about 3.9 billion years, let’s round that to 4 billion.
And, somewhat disconcertingly, it was expected to hit us head on.
These estimates were based on decades of observations from ground-based and space-based telescopes
and they all came with their own sets of error bars but more or less.
And while it won’t really matter to you and I personally, our Sun was expected to
be around when it happens.
The Sun is expected to turn into a Red giant in about 4.5 billion years, so it was conceivable
our Sun and anybody who may still be on Earth then could actually witness the event.
But then Gaia came along and changed things a bit.
I’ve reported on Gaia several times on SFN but what it does is measure the locations
and distances of stars within the Milky Way and our local group of Galaxies, more accurately
than has ever been done before.
It scans the sky making a map of around one billion stars, measuring the motion of each
star in its orbit around the centre of the Galaxy.
By the time it’s done, it will have observed each of it’s one billion stars at least
70 times resulting in a record of the brightness and position of each source over time.
This information is very useful in lots of ways, and astronomers are hoping to use Gaia
data to find exoplanets around other stars, asteroids in our Solar System, icy bodies
in the outer Solar System, brown dwarfs, and far-distant supernovae and quasars.
All kinds of really cool stuff.
So, when Gaia looked at 1,084 of the brightest stars within Andromeda and measured their
motions, it provided astronomers with the most accurate data yet of the proper motions
within the galaxy and from those, they we able to run models that updated the Milkomedia
(milkomeda?, milkdromeda?)
Collision.
According to the second data release of Gaia, from which these measurements were based,
things haven’t changed all that much, they two galaxies are still going to collide, but
not head on.
They are going to hit each other in glancing blows and they when it will happen has been
delayed 600 million years, the two galaxies won’t collide for another 4.5 billion years.
Right about when the Sun is expected to turn into a Red Giant.
That’s gonna be a busy time around here.
At their first close approach, the two galaxies will be about 420,000 light-years apart, or
far enough from one another that the disks will not interact.
But, galaxies are embedded in a large amount of dark matter, and as the Milky Way and Andromeda
pass one another, those dark haloes will snag.
That causes friction, which causes them to slow down and lose energy—and fall back
together.
THEN the galaxies will U-turn and actually collide, pass through one another, whip around,
and collide again.
This will happen over and over until eventually those collisions have sculpted them into a
single galaxy.
Probably something like an elliptical galaxy, the oldest and largest galaxies in the universe.
Here on Earth, I think people (if there are any) will be more worried about the Sun turning
into a Red Giant than the galaxy collision, and rightfully so.
The galaxy collision will just provide an amazing show in the night sky, but the Sun
is likely to turn the Earth into charcoal, so I’m sure that will take up most of our
attention.
Well, that’s it for this episode Space Fans.
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Thanks to all of you for watching and as always, Keep Looking UP!