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.
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.
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.