ESA Gaia: 'Go' for Science

[bystander]

Gaia: 'Go' for Science
ESA Space Science | Gaia | 2014 July 29

Click to play embedded YouTube video.

Inside Gaia’s billion-pixel camera - Credit: ESA

Following extensive in-orbit commissioning and several unexpected challenges, ESA’s billion-star surveyor, Gaia, is now ready to begin its science mission.

The satellite was launched on 19 December 2013, and is orbiting a virtual location in space 1.5 million kilometres from Earth.

Gaia’s goal is to create the most accurate map yet of the Milky Way. It will make extremely accurate measurements of the positions and motions of about 1% of the total population of roughly 100 billion stars in our home Galaxy to help answer questions about its origin and evolution.

Repeatedly scanning the sky, Gaia will observe each of its billion stars an average of 70 times each over five years. Small apparent motions in the positions of the stars will allow astronomers to determine their distances and movements through the Milky Way.

In addition, Gaia will also measure key physical properties of each star, including its brightness, temperature and chemical composition. ...

http://asterisk.apod.com/viewtopic.php?t=29043
http://asterisk.apod.com/viewtopic.php?t=29562
http://asterisk.apod.com/viewtopic.php?t=32274
http://asterisk.apod.com/viewtopic.php?t=32621
http://asterisk.apod.com/viewtopic.php?t=32876

[MargaritaMc]

I thought that this arxiv paper might be of interest. It's to appear in the proceedings of the SPIE 9143, 2014 Astronomical Instrumentation and Telescopes conference.

This is the abstract:

http://arxiv.org/abs/1408.3039

Enabling Gaia observations of naked-eye stars

J. Martín-Fleitas, A. Mora, J. Sahlmann, R. Kohley, B. Massart, J. L'hermitte, M. Le Roy, P. Paulet
(Submitted on 13 Aug 2014)

The ESA Gaia space astrometry mission will perform an all-sky survey of stellar objects complete in the nominal magnitude range G = [6.0 - 20.0]. The stars with G lower than 6.0, i.e. those visible to the unaided human eye, would thus not be observed by Gaia. We present an algorithm configuration for the Gaia on-board autonomous object observation system that makes it possible to observe very bright stars with G = [2.0-6.0). Its performance has been tested during the in-orbit commissioning phase achieving an observation completeness of ~94% at G = 3 - 5.7 and ~75% at G = 2 - 3. Furthermore, two targeted observation techniques for data acquisition of stars brighter than G = 2.0 were tested. The capabilities of these two techniques and the results of the in-flight tests are presented. Although the astrometric performance for stars with G lower than 6.0 has yet to be established, it is clear that several science cases will benefit from the results of the work presented here.

[MargaritaMc]

ESA http://www.esa.int/Our_Activities/Space ... _supernova

Click to view full size image

Supernova Gaia14aaa and its host galaxy

12 September 2014
While scanning the sky to measure the positions and movements of stars in our Galaxy, Gaia has discovered its first stellar explosion in another galaxy far, far away.

This powerful event, now named Gaia14aaa, took place in a distant galaxy some 500 million light-years away, and was revealed via a sudden rise in the galaxy’s brightness between two Gaia observations separated by one month.

Gaia, which began its scientific work on 25 July, repeatedly scans the entire sky, so that each of the roughly one billion stars in the final catalogue will be examined an average of 70 times over the next five years.
... To confirm the nature of this supernova, the astronomers complemented the Gaia data with more observations from the ground, using the Isaac Newton Telescope (INT) and the robotic Liverpool Telescope on La Palma, in the Canary Islands, Spain.

A high-resolution spectrum, obtained on 3 September with the INT, confirmed not only that the explosion corresponds to a Type Ia supernova, but also provided an estimate of its distance. This proved that the supernova happened in the galaxy where it was observed.

“This is the first supernova in what we expect to be a long series of discoveries with Gaia,” says Timo Prusti, ESA’s Gaia Project Scientist.

Supernovas are rare events: only a couple of these explosions happen every century in a typical galaxy. But they are not so rare over the whole sky, if we take into account the hundreds of billions of galaxies that populate the Universe.

Astronomers in the Science Alert Team are currently getting acquainted with the data, testing and optimising their detection software. In a few months, they expect Gaia to discover about three new supernovas every day.
...

[BDanielMayfield]

Since during Gaia’s five year mission it will be examining every piece of the sky an average of 70 times that means that, on average, each area of the celestial sphere will be surveyed each (365 x 5)/70 days, or approximately 26 days. And that’s just an overall average. It always will be looking away from near the Sun of course, so when it is sweeping an area the duration between a point being in one of it’s two fields of view will be much shorter.

With such frequent coverage all manor of transient events will be detected.