Gaia Space Telescope Blasts Off Today On A 5-year Milky Way Mission

Soyuz VS06, carrying the Gaia space observatory, lifted off from Europe’s Spaceport, French Guiana today Dec. 19. Shock waves surround the speeding rocket. Credit: ESA

Early this morning the European Space Agency (ESA) successfully launched the Gaia space telescope from the Kourou Spaceport in French Guiana. Its mission: to create a precision three-dimensional map of the Milky Way galaxy by studying a billion stars over five years time. Yes, that’ one billion stars – about 1% of the total population of stars in the galaxy.

Illustration of the L2 point showing the distance between the L2 and the Sun, compared to the distance between Earth and the Sun. Gaia will take up residence at this gravitationally stable point in space away from much of the heat and light from Earth and sun. Credit: ESA

Gaia is now cruising toward the gravitationally-stable L2 point located 932,000 miles (1.5 million km) on the opposite side of the Earth from the sun. It will arrive there in about 20 days. Four months later, during which instruments will be turned on, checked and calibrated, Gaia will begin its 5-year mission.

Like petals surrounding the heart of a sunflower, Gaia’s sun shield unfolded shortly after launch and will prevent heat and light from the sun and Earth from interfering with ultra-precise measurements of the stars’ positions and compositions.

“Repeatedly scanning the sky, Gaia will observe each of the billion stars an average of 70 times each over the five years. It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition,” writes the agency.

Its sun shield unfolded, Gaia maps the stars of the Milky Way in this artist’s illustration using a sophisticated billion-pixel camera. Credit: ESA/ATG medialab; background image: ESO/S. Brunier

Gaia will take advantage of the changing perspective on the stars it observes as it orbits the sun during the year, using parallax and basic math to measure precise distances to all one billion stars. Over the five years, it will be able to track the stars’ motions across the galaxy, helping us discover from where they originated in the Milky Way and where they’re headed.

Plotting stellar motion may even lead us to a grander synthesis about the origin and evolution of the galaxy itself –  how it was assembled from the merger of smaller galaxies and what fate holds for our big, beautiful home.

By comparing its repeated scans of the sky, Gaia will also discover tens of thousands of supernovas. Small periodic wobbles in the positions of some stars caused by tugging planets should reveal the presence of planets in orbit around them. Closer to home, the probe will discover new asteroids flitting around the solar system and test Einstein’s General Relativity Theory.

Animation showing Gaia’s journey to its operating orbit. Credit: ESA

Much of what we know about stars, nebulas, galaxies and all the rest is based upon having accurate distances to them. The earlier ESA Hipparcos mission cataloged positions of 120,000 stars; Gaia will survey almost 10,000 times as many at roughly 40 times higher precision.

Humanity is reaching out to the stars in a big way here. It gives me hope that our distant descendants will one day roam the galaxy.

For more information on Gaia, please refer to today’s ESA press release.

6 Responses

  1. Giorgio Rizzarelli

    The other day I was wondering how many Km from cities one should be to avoid light pollution…1.5 million Km makes sense!

  2. RC

    I was curious how much time it takes Gaia to make an observation of each star. Since I already did the math, I thought I’d share:

    Gaia will work for 5 years: 5 years = 1825 days = 43,800 hours = 2,628,000 minutes = 157,680,000 seconds.

    Gaia will make 70 observations of 1,000,000,000 stars: =70,000,000,000 observations.

    157,680,000 seconds / 70,000,000,000 observations = 0.00225 seconds per observation! (or 444 observations per second!) That is incredibly fast if you ask me.

    1. astrobob

      Your math is impeccable and the number is amazing yet nonetheless true according to ESA. That’s almost 40 million measurements per day!

      1. Richard Keen

        I’d guess the actual observation rate is more than a thousand per second, since most stars will be observed more than once over five years.
        Some more math….
        Spaceflight Now lists the total cost of the mission as $1.3 billion
        or $1.30 per star to record so much data about each of those billion stars. In addition, there will be a Gaia catalog that names each star.
        Those star reg*stries charge $30 and up per star just to give it a “name”.
        So Gaia is a bargain!

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