
Gaia space telescope plots a billion stars - okket
http://www.bbc.com/news/science-environment-37355154
======
okket
The Gaia Data Release 1 Archive:
[http://gea.esac.esa.int/archive/](http://gea.esac.esa.int/archive/)

Some information about the archive:
[http://www.cosmos.esa.int/web/gaia/dr1](http://www.cosmos.esa.int/web/gaia/dr1)

Press conference from earlier today:
[https://www.youtube.com/watch?v=5pAjvQ5uu7I](https://www.youtube.com/watch?v=5pAjvQ5uu7I)

Gaia's first sky map (incl. downloads up to 15360×7831):
[http://sci.esa.int/gaia/58209-gaia-s-first-sky-
map/](http://sci.esa.int/gaia/58209-gaia-s-first-sky-map/)

~~~
netcraft
Visualization of the data:
[http://gea.esac.esa.int/visualization/index.html](http://gea.esac.esa.int/visualization/index.html)

~~~
pc2g4d
Seems like there are two smaller galaxies in the bottom right. Does anybody
know what those are?

~~~
netcraft
I had the same question, found the answer here:
[http://sci.esa.int/gaia/58209-gaia-s-first-sky-
map/](http://sci.esa.int/gaia/58209-gaia-s-first-sky-map/) it says > The two
bright objects in the lower right of the image are the Large and Small
Magellanic Clouds, two dwarf galaxies orbiting the Milky Way. Other nearby
galaxies are also visible, most notably Andromeda (also known as M31), the
largest galactic neighbour to the Milky Way, in the lower left of the image.
Below Andromeda is its satellite, the Triangulum galaxy (M33).

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mnw21cam
T'was back in December 2008, I applied for a university sideways move to a job
analysing the data from the yet to be launched Gaia probe. Turns out I was
over-qualified (which was their way of saying that the university was already
paying me more than they were willing to pay for that position), and they
recommended I apply for a position analysing data for the Planck probe
instead. Went to that interview too, where I was told I was _under_ qualified.
Every time either of those two probes turns up in the news is a nice trip down
memory lane. The engineering involved in building them was quite remarkable,
and sifting through the data would have been fun.

~~~
TeMPOraL
I wonder why they couldn't be honest with you? What bad things would happen if
they simply told you "we're only able to pay X for this position, take it or
leave it"?

~~~
mnw21cam
Because it was a sideways move (in other words, I was already working for the
same university) it would have been illegal for them to lower my pay.

Ironically, them telling me I was underqualified (specifically, I didn't have
doctorate) spurred me on to go and get one. I had basically hit the ceiling
for a Mr. in a university.

------
EA
"There may be 2-3 times more stars in the Milky Way Galaxy than we thought"

~~~
biot
Looks like they found the dark matter.

------
netcraft
> The one billion to be catalogued by Gaia is still only 1% of the Milky Way's
> total

I mean, wow. We are so tiny.

> The called-for specification was to get to know the brightest objects'
> coordinates down to an error of just seven micro-arcseconds. This angle is
> equivalent to the size of a euro coin on the Moon as seen from Earth.

This is quite an impressive feat of engineering!

~~~
pmoriarty
And there are more galaxies in the known universe then there are stars in our
galaxy.

~~~
okket
Yes, there may be more galaxies than stars in our milky way. But almost all of
them are extremely far away and we will never have a chance to interact, or
even visit them. Worse, the rate they are moving away from our galaxy/local
cluster is accelerating. We have a bit time to study those galaxies before
they fade into the eternal redshift, but the real interesting stuff, what at
least has a decent chance to matter beyond pure curiosity is what Gaia
observes.

~~~
jobigoud
> We have a bit time to study those galaxies before they fade into the eternal
> redshift

Just want to point that we do receive light from galaxies that are receding
from us faster than the speed of light and always have been.

~~~
okket
Until they are so far redshifted that they fade into background noise. And the
expansion of the universe is accelerating. We have a bit time to watch this
spectacle, but the fate seems it is just our local cluster that will matter,
for most of the time while stars generate heat. That is why I am not so keen
on emphasising the billions and billions of galaxies. It's only a nice good-
bye firework.

Edit: I still think there are much more galaxies in our universe than stars in
our milky way: The universe must be bigger than our observable part and there
is no reason to believe that it is much different there (read less or no
galaxies) than where we happen to be. So the "eternal redshift" already
happened for many galaxies (from mutual perspective).

------
Rexxar
I have some questions on the "stellar parallax" illustration.

If I remember correctly the speed of Sun around the milky way is much bigger
than the speed of earth around the Sun. So the position of the earth is
completely different in June and December, because the sun has moved. So

-> Do the parallax computation works only in one direction ? (perpendicularly to the sun trajectory ?)

-> Does it works for nearest stars because they have roughly the same speed and direction than Sun ?

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GFK_of_xmaspast
> they have roughly the same speed and direction than Sun

Are you sure about that?

[https://en.wikipedia.org/wiki/Barnard%27s_Star](https://en.wikipedia.org/wiki/Barnard%27s_Star)
: "The proper motion of Barnard's Star corresponds to a relative lateral speed
of 90 km/s. The 10.3 seconds of arc it travels annually amount to a quarter of
a degree in a human lifetime, roughly half the angular diameter of the full
Moon."

[https://en.wikipedia.org/wiki/Alpha_Centauri](https://en.wikipedia.org/wiki/Alpha_Centauri)
"All components of Alpha Centauri display significant proper motions against
the background sky, similar to the first-magnitude stars Sirius and Arcturus.
Over the centuries, this causes the apparent stellar positions to slowly
change. Such motions define the high-proper-motion stars"

