Tour: Chandra Determines What Makes a Galaxy's Wind Blow

On Earth, wind can transport particles of dust and debris across the planet, with sand from the Sahara ending up in the Caribbean or volcanic ash from Iceland being deposited in Greenland. Wind can also have a big impact on the ecology and environment of a galaxy, just like on Earth, but on much larger and dramatic scales.

A new study using NASA’s Chandra X-ray Observatory shows the effects of powerful winds launched from the center of a nearby galaxy, NGC 253, located 11.4 million light-years from Earth. This galactic wind is composed of gas with temperatures of millions of degrees that glows in X-rays. An amount of hot gas equivalent to about two million Earth masses blows away from the galaxy’s center every year.

NGC 253 is a spiral galaxy, making it similar to our Milky Way. However, stars are forming in NGC 253 at a higher rate than our home galaxy. Some of these young stars are massive and generate a wind by ferociously blowing gas from their surfaces. Powerful winds are also unleashed when, later in their relatively short lives, these stars explode as supernovas, and hurl waves of material out into space.

NGC 253 gives astronomers a keyhole through which to study this important phase in the stellar life cycle. The material that the young stars send out into intergalactic space across hundreds of light-years is enriched with elements forged in their interior. These elements, which include many responsible for life on Earth, are folded into the next generations of stars and planets.

A team of researchers used deep Chandra observations, taken over four days, to study the properties of the wind. They found that the densities and temperatures of the gas in the wind are the highest in the central 800 light-years — and then decrease with distance away from the center of the galaxy. This is an important clue to some of the details of the physics happening in this galaxy.

More work is needed to match up theoretical models with the data from Chandra and other telescopes of NGC 253. Astronomers will also need more observations in the future of other galaxies with winds to better understand this important process.