Science & Technology

Check Out the Most Detailed Map of Our Galaxy Ever

Look at the night sky. How many stars can you see? For an average observer under a dark sky, you might count a few thousand twinkling lights. A new set of satellite images, however, tracks almost two billion stars — the most high-precision map of the sky yet.

Knowing where the stars are located is just one step to understanding the sky around us, though. With this data from the European Space Agency (ESA) Gaia mission, scientists can launch all sorts of scientific investigations. For example, they can look for "runaway" stars streaking across the sky, or continue the hunt for the sun's lost siblings.

Runaway Star, Never Going Back

Gaia is a spacecraft that launched in 2013 to a faraway location four times further out than the moon. That's an incredible 930,000 miles (1.5 million kilometers) from Earth, where the entire sky is visible. Gaia's goal is map-making: to create the best chart ever of the Milky Way's stars, building on past all-sky surveys such as Hipparcos.

The results sent out on April 25 are based on 22 months of observations between July 2014 and May 2016. That encompasses 1.7 billion stars for some types of results! The findings are so comprehensive that it's hard for a single article to describe them all. But as a starting point, Gaia's data will help astronomers catch fleeing stars in the act.

That's because the spacecraft can track a star's proper motion as it moves around our galaxy, the Milky Way. While all stars move in the sky, a runaway star stands out because it speeds faster than other stars in its birthplace. It's hard to define how fast that speed is, because it depends on where the star is located and what environment it's in. But for perspective, it takes an incredible speed of 50,000 to 70,000 miles per hour (80,500 to 113,000 kilometers per hour) to break free of the galaxy's gravitational pull.

Scientists have found several of these weird stars lately. For example, astronomers recently hunted down the birthplace of two runaway stars speeding away in opposite directions, at almost 30 times the speed of other stars in their gas cloud. When the Hubble Space Telescope found a third runaway, scientists traced the stars' paths back to their origins and concluded all three stars came from a multiple-star system before breaking free. The results were published in March in Astrophysical Journal Letters.

Another research group saw a rare type of supergiant star careening at high speed in the Small Magellanic Cloud, which is a satellite galaxy to the Milky Way. What's more bizarre is the star will keep evolving and changing until it runs out of fuel, researchers said. "The star will continue speeding through space until it too blows up as a supernova, likely in another three million years or so," Lowell Observatory (which participated in the Astronomical Journal study) stated in March.

Seeking the Sun's Siblings

Most stars are born in families. They grow in vast clouds of gas and dust and eventually push each other away through gravitational interactions. Our sun must have some siblings out there somewhere, but astronomers don't know exactly where. The search isn't over yet, but Gaia data will likely help scientists find the sun's family members.

An Australian survey called GALactic Archaeology with HERMES (GALAH) is looking at 350,000 nearby stars to analyze their chemical composition. If they find a match to the sun, we can presume those distant stars are related. Gaia's work will help the GALAH researchers, the GALAH group says on their website, because Gaia provides information on the distances, motion, and positions of other stars. The two surveys together will provide a mini-history of our galaxy's development.

But before we get too excited about future studies, let's appreciate the scientific achievement Gaia represents. The new release has vast troves of data concerning stars with variable brightness, the color of stars, and even objects such as asteroids (space rocks), quasars (galaxies with black holes), and the proper motion of star clusters and dwarf galaxies.

Scrutinizing Star Evolution

"The observations collected by Gaia are redefining the foundations of astronomy," stated Günther Hasinger, ESA's director of science.

One example is adding even more detail to the Hertzsprung-Russell diagram that maps star populations and evolution. Gaia provided a lot more information on white dwarfs — the dead remnants of sun-like stars that shed their outer layers. Through those white dwarf studies, astronomers discovered the chemical "signature" of a hydrogen core star is different than a helium core star.

You can check out the results for yourself in raw format here. If virtual reality is more your thing, ESA has you covered with a set of 3-D visualizations. And for the scientific observers reading this article, more information about the study is forthcoming in a special edition of the journal Astronomy & Astrophysics.

Written by Elizabeth Howell April 26, 2018

Curiosity uses cookies to improve site performance, for analytics and for advertising. By continuing to use our site, you accept our use of cookies, our Privacy Policy and Terms of Use.