Odd job: cataloging a billion stars

[neufer]

Click to play embedded YouTube video.

The Gaia spacecraft's Deployable Sunshield Assembly (DSA) unfurls.
The timelapse shown here speeds up the ~20 minute process.

Click to play embedded YouTube video.

Click to play embedded YouTube video.

Gaia Prepares for Ultimate Galactic Census
Posted by Jason Davis, Planetary Society, 2013/10/06

<<The European Space Agency’s Gaia spacecraft is set to embark on a five-year mission to catalog a billion stars—yes, that's billion, with a 'b.' The two-ton probe will become one of ESA’s flagship astronomy missions, joining heavyweights like Rosetta, Herschel and BepiColumbo. Launch is currently scheduled for November 20 from French Guiana. The European Space Agency's Gaia spacecraft will construct the largest, most precise three-dimensional map of our galaxy ever created.

Gaia was formerly known as GAIA, the Global Astrometric Interferometer for Astrophysics. The original design called for an interferometer, which combines the light from two or more telescopes to create a higher resolution image, while sacrificing the overall amount of light collected. Although the final design still uses two telescopes, the interferometry technique was dropped. GAIA, therefore, became plain old Gaia.

Each telescope has a rectangular slit on the side of the spacecraft's cylindrical core, which allows starlight to bounce around a system of five mirrors (ten total for both telescopes). Eventually, the light focuses on what the ESA says is the largest focal plane ever installed in a space telescope: a 0.38-square-meter charge-coupled device (CCD) capable of resolving a billion pixels.

It's gotta stay cool, though.

While not requiring the extreme chilliness found onboard infrared telescopes like the now-retired Herschel Space Observatory, Gaia still needs solid protection from the Sun's energy. After launching into space atop a Soyuz rocket, Gaia will be propelled by a Fregat upper stage onto a three-month journey to the L2 Lagrangian Point. A deployable sunshield will unfurl to protect the spacecraft's CCD and science instruments, maintaining a constant -120 degree Celsius.

Three different science instruments will process the light that Gaia collects. First, there’s ASTRO, the astrometric instrument, which maps out the position of each star. Over the course of five years, ASTRO will be able to track each star’s parallax (used to calculate distance) and proper motion (the star’s two-dimensional position change from our point of view). Next, the radial velocity spectrometer, or RVS, will measure each star’s Doppler shift, which is used to determine radial velocity. Radial velocity is a measure of how fast a star is moving toward or away from us.

By combining distance, proper motion and radial velocity, scientists will be able to get each star's true space velocity; that is, its actual three-dimensional speed and direction.

The third science instrument is BP/RP, a blue/red photometric instrument. BP/RP will capture a low-resolution measurement of each star's spectra, which provides basic details like temperature, mass and chemical composition.

Gaia will slowly spin as it travels around the sun in line with the Earth, eventually capturing the entire swath of our sky. The European Space Agency's Gaia spacecraft will map a billion stars as it slowly scans the Milky Way, creating a three-dimensional map. The result: a billion-star map, complete with true velocities and basic compositional data. Great—Now what?

The applications listed by the ESA are pretty wide-ranging. One tantalizing use of the data is assisting with the so-called dark matter problem. Dark matter is the mysterious stuff spread throughout our universe that interacts gravitationally on objects, but gives off no light. One of the keys to learning about dark matter is measuring how stars interact with it. A billion-star distance and velocity map would certainly seem to be a big help.>>

[Ann]

I'm so, so looking forward to Gaia, and I so, so hope it will be successful!

Ann

[Ann]

Oh, by the way, I forgot, Beyond. The letter Å is used in physics as an incredibly tiny unit of length. Å stands for Ångström, a Swedish physicist or some other kind of scientist. (I don't remember anything about him, and I don't have the strength to google him.) But anyway, the unit of length is named after him. An Å is ten times shorter than a nanometer. So 4725 Å is the same thing as 472.5 nm! Unsurprisingly, this wavelength corresponds to a blue color!

Ann

[Chris Peterson]

Oh, by the way, I forgot, Beyond. The letter Å is used in physics as an incredibly tiny unit of length. Å stands for Ångström, a Swedish physicist or some other kind of scientist. (I don't remember anything about him, and I don't have the strength to google him.) But anyway, the unit of length is named after him. An Å is ten times shorter than a nanometer. So 4725 Å is the same thing as 472.5 nm! Unsurprisingly, this wavelength corresponds to a blue color! :D

Note, however, that the Ångström is a deprecated unit, not part of the SI system. Its use hangs on in a few areas, but in general it shouldn't be used (I knock a few points off my students' scores if they use it instead of nanometers, or some other SI unit).

[Beyond]

Oh, by the way, I forgot, Beyond. The letter Å is used in physics as an incredibly tiny unit of length. Å stands for Ångström, a Swedish physicist or some other kind of scientist. (I don't remember anything about him, and I don't have the strength to google him.) But anyway, the unit of length is named after him. An Å is ten times shorter than a nanometer. So 4725 Å is the same thing as 472.5 nm! Unsurprisingly, this wavelength corresponds to a blue color!

Ann

and/or . Would you believe i never gave it a thought about it pertaining to the color blue???? Yeah... shame on me

[neufer]

The letter Å is used in physics as an incredibly tiny unit of length. Å stands for Ångström, a Swedish physicist or some other kind of scientist. (I don't remember anything about him, and I don't have the strength to google him.) But anyway, the unit of length is named after him. An Å is ten times shorter than a nanometer. So 4725 Å is the same thing as 472.5 nm! Unsurprisingly, this wavelength corresponds to a blue color!

and/or . Would you believe i never gave it a thought about it pertaining to the color blue???? Yeah... shame on me

• The refrÅngible Ånn is a one-Årmed, unÅdorned, dyeing blue poo eater
  for "not having the strength" to Google Swedish physicist Anders Jonas Ångström

<<Anders Jonas Ångström (13 August 1814, Lögdö, – 21 June 1874) was a Swedish physicist and one of the founders of the science of spectroscopy.

Anders Angstrom was born in Medelpad, he moved to, and was educated at Uppsala University, where in 1839 he became docent in physics. In 1842 he went to the Stockholm Observatory to gain experience in practical astronomical work, and the following year he was appointed keeper of the Uppsala Astronomical Observatory.

Becoming interested in terrestrial magnetism he made many observations of magnetic intensity and declination in various parts of Sweden, and was charged by the Stockholm Academy of Sciences with the task, not completed till shortly before his death, of working out the magnetic data obtained by the Swedish frigate "Eugénie" on her voyage around the world in 1851–1853.

[b][color=#0000FF]Ångström is a small lunar impact crater located on the border between Oceanus Procellarum to the west and Mare Imbrium to the east. To the south is a formation of mountains rising out of the mare named the Montes Harbinger. To the east are some wrinkle ridges named the Dorsum Bucher and Dorsum Argand. This crater is bowl-shaped, with a circular rim and inner walls that slope down to the small central floor. It has a higher albedo than the surrounding maria.[/color][/b]

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In 1858, he succeeded Adolph Ferdinand Svanberg in the chair of physics at Uppsala. His most important work was concerned with the conduction of heat and with spectroscopy. In his optical researches, Optiska Undersökningar, presented to the Royal Swedish Academy of Sciences in 1853, he not only pointed out that the electric spark yields two superposed spectra, one from the metal of the electrode and the other from the gas in which it passes, but deduced from Leonhard Euler's theory of resonance that an incandescent gas emits luminous rays of the same refrangibility as those it can absorb. This statement, as Sir Edward Sabine remarked when awarding him the Rumford medal of the Royal Society in 1872, contains a fundamental principle of spectrum analysis, and though overlooked for a number of years it entitles him to rank as one of the founders of spectroscopy.

From 1861 onwards, he paid special attention to the solar spectrum. His combination of the spectroscope with photography for the study of the Solar System resulted in proving that the Sun's atmosphere contains hydrogen, among other elements (1862), and in 1868 he published his great map of the normal solar spectrum in Recherches sur le spectre solaire, including detailed measurements of more than 1000 spectral lines, which long remained authoritative in questions of wavelength, although his measurements were inexact by one part in 7000 or 8000, owing to the metre he used as a standard being slightly too short.

Ångström was the first, in 1867, to examine the spectrum of the aurora borealis, and detected and measured the characteristic bright line in its yellow green region; but he was mistaken in supposing that this same line, which is often called by his name, is also to be seen in the zodiacal light.

He was elected a member of a number of learned societies, including the Royal Swedish Academy of Sciences in 1850, the Royal Society in 1870 and the Institut de France in 1873. He died in Uppsala on 21 June 1874. The crater Ångström on the Moon is named in his honour. One of the main building complexes of Uppsala University, the Ångström Laboratory, is named in his honour.>>

[jadenicon]

So how much is the salary for this?