Gaia’s Galaxy

Don’t know what Gaia is? In Greek mythology Gaia is a goddess and the mother of all Earthly life.  Gaia is also Earth, the planet we live on. There’s way more to it but not for this article.

The Gaia I’m talking about is an exploration spacecraft developed by ESA (the European Space Agency) and launched atop a Soyuz rocket in 2013. It’s the successor to ESA’s Hipparcos (1989-1993). I know, that’s nearly 10 years ago, so why talk about it now? Because Gaia’s mission is HUGE. The information it produces will be on the same level of importance as the James Webb Space Telescope.

The Gaia (Global Astrometric Interferometer for Astrophysics) spacecraft looks like a Spanish Gaucho hat, weighs 1392 kilograms or 3069 pounds, and is organized as a payload (instrument) module and service (control and power) module. The Gaucho hat brim is a Sun shield, covered with silver and gold foil, to keep sunlight from interfering with the instrument’s measurements. After launch on December 19, 2013, its mission began on July 25th, 2014.

Gaia’s mission, sit down, is to make a 3-D map of our Milky Way galaxy by precisely following more than a billion stars as they travel within the Milky Way. Ultimately, Gaia’s data will help us understand our galaxy’s formation, composition, and evolution.

The spacecraft rotates once every 6 hours, its two telescopes gathering data as the star field slowly sweeps past. Specifically, the data for a select billion stars is collected onto 106 CCDs, each with 4,500 x 1,996 pixels – that’s nearly a billion pixels! The data collected includes spectra, luminosity/magnitude and position.

Since it started collecting data, Gaia has transmitted three datasets, in 2015, 2018, and a split set 2020/2022.  It’s expected to send more datasets well into the 2020s.  Here are some it its notable results beyond its primary missions:

-The discovery of Gaia Enceladus (Gaia Sausage), the remains of a merger of our Milky Way with dwarf galaxy Enceladus more than 10 billion years ago. This merger added over a dozen globular clusters to our galaxy.

-The discovery of Antila-2, a dwarf galaxy orbiting our Milky Way. Its about the size of the Large Magellanic Cloud but 10,000 times fainter. The lowest surface brightness galaxy discovered so far.

-The discovery of hyper-velocity stars exiting and entering the Milky Way. 20 hyper-velocity stars were followed and a surprising 7 were found to be exiting the galaxy. Even more surprising, 13 were detected entering the Milky Way.

-The discovery of the nearest wave of associated molecular clouds, stellar nurseries, extending 8,800 light years within the Milky Way. It’s named the Radcliffe Wave, after the Radcliffe Institute for Advanced Study.

-The discovery of extrasolar planets

-Using Gaia’s data, the most accurate Hertzsprung – Russell diagram to date has been completed.

What’s in the Sky?

June 10; after sunset; south: Bright orange Antares is a little more than 2 degrees below and left of a waxing gibbous Moon. Binoculars enhance the view.