
What Astronomers Are Learning from Gaia’s New Milky Way Map - GW150914
https://www.quantamagazine.org/what-astronomers-are-learning-from-gaias-new-milky-way-map-20180508/
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bryanh
The great YouTube channel "PBS Space Time" did a video on Gaia and how it is
changing astronomy:
[https://www.youtube.com/watch?v=Jdy09y0A4t0](https://www.youtube.com/watch?v=Jdy09y0A4t0).
I highly recommend the channel. I really appreciate that they don't pull any
punches, you'll often see math formulas on screen! Most astronomy education
material (think classic Discovery channel) tends to be extremely watered
down...

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ninkendo
Agreed, I just watched this earlier today. Space Time is the only series on
YouTube where I subscribe to their patreon and continue to renew. It's my
favorite series on the whole site, probably.

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typpo
If anyone is interested in playing with GAIA data, I created a simple
interactive visualization using WebGL. Here's the source:
[https://github.com/typpo/gaia](https://github.com/typpo/gaia)

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obelix_
5 years to count ~.1 to 1% of the stars in 1 galaxy. What ants we are?

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antognini
It's not so much that it takes a long time to image all of these stars, but
that Gaia is measuring parallax which inherently requires taking measurements
for 6 months in order for the Earth to go halfway around the Sun. If you want
multiple measurements to reduce your uncertainty, you have to do it in 6 month
blocks. 10 measurements per star gives you 5 years.

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shostack
I'll preface this by saying I know next to nothing about these sorts of
measurements. But if you want multiple measurements, isn't time just one
variable when measuring parallax? Couldn't we potentially image it from
different viewpoints--say, distant satellites relaying messages back for
analysis, where time is more a function of the scale of the "imaging web?"

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wcoenen
A second satellite could be put in the same orbit around the sun as the Earth,
but on the other side of the sun. That would give us stereo vision for the
parallax measurements.

But it's cheaper to have just 1 satellite (which is also easier to communicate
with because near Earth), and then compare images 6 months apart to get the
same data.

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sanxiyn
A practical problem is that it is hard to communicate with the other side of
the sun.

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8bitsrule
Amazing read - I had no idea how much this was going to change things. 500km/s
streams? 1.3B velocities? White dwarfs flung at high velocities? Satellites
with massive black holes? 'satellite galaxies ... all ... currently at the
closest points in their orbits'? Well - this will liven up discussions for a
LONG time.

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lodi
Lots of sources are saying that with star position/velocity information,
scientists can rewind or fast-forward time to see how the Milky Way looked
hundreds of millions of years in the past/future.

Does anybody know how they're solving a 1B+ element n-body problem with enough
precision to make that kind of claim? I thought these things were so chaotic
that this kind of prediction was impossible?

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vanni
[https://en.wikipedia.org/wiki/Gaia_(spacecraft)](https://en.wikipedia.org/wiki/Gaia_\(spacecraft\))

