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ESA's Second Batch of Gaia Data Coming in April 2018

posted by mrpg on Tuesday January 02 2018, @10:15AM   
from the as-long-as-it-doesn't-arrive-in-april-1st dept.

takyon writes:

The European Space Agency's Gaia space observatory was launched in 2013 and is currently making the most detailed 3D star map ever, containing over a billion Milky Way stars. Gaia DR1 was released on September 14, 2016, and contained positions and magnitudes for around 1.1 billion stars. The second data release will contain positons, parallaxes, and proper motions for around a billion stars, as well as red and blue photometric data and some radial velocity measurements. DR2 will also include data for 10,000 solar system objects. Both batches of data contain some extragalactic stars, allowing studies of nearby galaxies:

The first batch of Gaia data, released in 2016 and based on 14 months of science operations, contained the position and brightness of more than one billion stars. Most of these stars are located in the Milky Way, but a good fraction are extragalactic, with around ten million belonging to the [Large Magellanic Cloud (LMC)].

For all these stars and more, the second release of Gaia data – planned for April 2018 – will also contain measurements of their parallax, which quantifies a star's distance from us, and of their motion across the sky. Astronomers are eagerly awaiting this unprecedented data set to delve into the present and past mysteries of our Galaxy and its neighbours.

By analysing the motions of individual stars in external galaxies like the LMC, Andromeda, or Triangulum, it will be possible to learn more about the overall rotation of stars within these galaxies, as well as the orbit of the galaxies themselves in the swarm they are part of, known as the Local Group.

In the case of the LMC, a team of astronomers have already attempted to do so by using a subset of data from the first Gaia release, the Tycho–Gaia Astrometric Solution (TGAS), for which parallaxes and proper motions had also been provided by combining the new data with those from ESA's first astrometry mission, Hipparcos. In the TGAS data set, consisting of two million stars, they identified 29 stars in the LMC with good measurements of proper motions and used them to estimate the rotation of the galaxy, providing a taster of the studies that will become possible with future releases of Gaia data.

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Original Submission

• Re:Celestia data (Score: 3, Interesting) by takyon on Wednesday January 03 2018, @01:19AM

  by takyon (881) <takyonNO@SPAMsoylentnews.org> on Wednesday January 03 2018, @01:19AM (#617010) Journal

  It would likely come in as a huge addon.

  Here's something relevant (but slightly outdated) from the Space Engine forum [spaceengine.org]:

  *SPOILER* (click to show) *SPOILER* (click to hide)

  "Currenly SE uses this data per star:
  Coordinates (XYZ or RA/Dec/Dist) - 3 floats (12 bytes)
  Luminosity or app mag - 1 float (4 bytes)
  Spectral class - currently packed to 1 short (2 bytes), but probably must be extended to 1 int (4 bytes).

  But don't forget about name or catalog ID. Currently SE uses a csv format where everything is a text, but older versions used a separate file with names, like Celestia. Adding an 32-bit index for the database ID (which is enough to identify 4 billions stars) adds 4 bytes.

  Also, future versions of SE will use proper motion data, so stars in SE will have velocities (and maybe it will be possible to observe change in constellation shape, who knows). So add another 3 floats (12 bytes).

  So total we'll have 34 bytes per star. Probably some floats may be packed to 16-bit half-precision (2 bytes), so maybe this can be reduced to 32 bytes (computers likes power-of-two)."

  So, if the final Gaia Catalogue is about 1,142,679,769 stars then having 34 bytes per star that would mean that the addition of this to Space Engine corresponds to a 36,2 GB addon. Since very few people would download that mountruos addon it is probable that it would be stored on an internet server (when SE reaches this capability) and with your internet connection you would download chunks of the catalogue while flying through the galaxy (more or less like Google Earth where you don't need to download the 3 thousand terabyte database). That's why Vladimir cautiosly said a year ago:

  "to handle 1 billion stars (when final data set will be released in 2022), some adaptive loading/rendering algorithm is needed, similar to those used for planet textures. Space must be subdivided in cubes which are streamed from the disk as needed. However, maybe in 2022 one can simply load everything into memory, like SE handles HIPPARCOS catalog now"

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