If it's in 3D
does that mean only men can visualise it?
(see Science museum article if you don't understand)
The European Space Agency has revealed the first catalogue of stars mapped during its Gaia mission today. The Gaia space probe aims to capture over a billion stars, distant galaxies and quasars to produce the largest and most detailed three-dimensional map of the Milky Way galaxy. Nearly halfway into its mission, the probe …
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.
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.
"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.
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.
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.
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.