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Map to the stars: Gaia's first data dump a piece of 3D Milky Way puzzle

Anonymous Coward

If it's in 3D

does that mean only men can visualise it?

(see Science museum article if you don't understand)

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The error in this data release is 0.0002 arc-seconds and the intended error at the end of mission is 0.000007 arc-seconds. Star positions to an accuracy of 7 arc-seconds can be achieved with a DSLR and a reasonable telephoto lens, no need for a two-billion-Euro mission at the L2 Lagrange point.

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Go

Maybe it was adjusted after your comment, but it does specifically say 7 micro arc seconds in the article...

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It didn't earlier. So hold off the downvotes smartarses.

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Anonymous Coward

Sub-arcsecond angular resolutions ...

are for measuring distances to objects via direct parallax, and for proper motion studies, not for backyard astronomy to locate a particular star with binoculars. I think it will be a while before even professional grade digital DSLR cameras will achieve that degree of angular resolution.

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Re: Sub-arcsecond angular resolutions ...

And more accurate direct parallax is what lets us better confirm that the variable stars really do work the way we say they do as galactic yardsticks for much greater distances that are impossible to measure via parallax.

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Re: Sub-arcsecond angular resolutions ...

Once you are outside the atmosphere with your 1B pixel DSLR and telephoto, send us some of the pictures, I'll be more impressed with your comment.

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"Variable stars have fluctuating brightness and can be used as cosmic yardsticks to measure galactic distances."

Some of them can. (Cepheids.) Some can't. (Long Period Variables). It depends on whether there is a reliable relationship between the frequency of variation and the brightness of the star.

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Gold badge

Bit of a long-lens-paparazzo then...

"With 106 CCDs and almost a billion pixels, Gaia has a high enough resolution to measure the diameter of a human hair at a distance of 1,000 kilometres."

Now that's what I *call* an invasion of privacy!

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Re: Bit of a long-lens-paparazzo then...

Hardly, since human hairs don't vary that much in diameter.

If they wanna measure my hairs, let 'em. I have nothing to hide. Except behind my hairs...

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Paris Hilton

Re: Bit of a long-lens-paparazzo then...

Psst. don't tell anyone what plans ESA has to re-finance the bird after the end of its science mission!

Celebrities of the world beware, they'll count the hairs on your heads!

Paris 'cause she's.

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Pleiades

As I recall, Gaia uses the same basic method for determining stellar distances as Hipparcos. And Hipparcos returned anomalous results concerning the distance to the Pleiades that didn't agree with more straightforward results from parallaxes obtained through conventional imaging devices - ordinary telescopes.

Of course, putting something like the Hubble Space Telescope in orbit around Neptune as a method of properly calibrating the technique used in Gaia or Hipparcos, or handling the parallax of extended objects like the Pleiades, which might be tricky, might be hard to justify, as it would be a tad more expensive.

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Re: Pleiades

Hipparcos data analysis is a really hairy problem - van Leeuwen spent a decade inventing new data-reduction techniques and re-running the whole analysis, the fact that the satellite was stuck in geostationary transfer orbit because its apogee motor failed to fire didn't help.

Gaia's estimate for the position of the Pleiades is in one of the free-access papers published today, and is unsurprisingly absolutely bang in the middle of the results from Earth-bound telescopes or from astrophysical arguments.

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It's already all wrong....

Because they've all moved!

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Re: It's already all wrong....

And Gaia watches them move and measures how far they've moved, so two million of the stars are annotated with velocities already and about a hundred million will be by the end of the mission.

The researchers did do the obvious experiment to see whether any velocities were changing over time, because that would be an exciting result, but didn't find any convincing examples - it turned out simply to be an excellent way to find one category of mistakes matching up stars in the fifteen-year-old Tycho catalogue.

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Coat

And when they open that 40 gigs of data

It's full of stars!

--> space coat

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Great stuff. We might well let our students practice data mining on this set. Much nicer than giving them toy sets to play with

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Hmmmm, "a tray of CCDs."

An array of CCDs?

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