Safest place to live in the Milky Way found

Astronomers have searched our galaxy to identify the safest places to live. As it turns out, we’re in a pretty good spot

Astronomers have searched the Milky Way to identify the safest places to live. As it turns out, we’re in a good spot

If the past year has made you feel ready to relocate to another planet, you might want to look towards the centre of the galaxy. The new findings were made by a group of Italian astronomers, who studied locations where powerful cosmic explosions may have killed off life. These explosions, such as supernovae and gamma-ray bursts, spew high-energy particles and radiation that can shred DNA and kill life. By this logic, regions that are more hospitable to life will be the ones without frequent explosions, the astronomers reasoned.

“Powerful cosmic explosions are not negligible for the existence of life in our galaxy throughout its cosmic history,” said Riccardo Spinelli, an astronomer at the University of Insubria in Italy. “These events have played a role in jeopardising life across most of the Milky Way.”

In addition to finding the deadliest hotspots, the astronomers also identified the safest places throughout the galaxy’s history, going back 11 billion years. The results show that we’re currently at the edge of a wide band of hospitable real estate. But in the Milky Way’s youth, the galaxy’s edges were a safer bet.

Many factors make a planet habitable. For instance, planets need to be in a ‘Goldilocks zone’, where heat and activity from their host star isn’t too much or too little… it’s just right. But in addition to these local conditions, life also has to combat harmful radiation coming from interstellar space.

Powerful cosmic events like stellar explosions stream dangerous, high-energy particles at nearly the speed of light. Not only can they kill all the life forms we know about, but these particles can also strip entire planets of their atmospheres. After such an event, the scientists

believe that planets orbiting nearby star systems would be wiped clear of life.

“For planets close to the stellar explosion, it’s plausible that there is a complete sterilisation,” Spinelli said. “In those far away, a mass extinction is more likely.” A nearby gamma-ray burst may have played a leading role in the Late Ordovician mass extinction event around 450 million years ago – the second largest in Earth’s history. While there is no concrete evidence linking a specific gamma-ray burst to this extinction event, the study authors think it could be likely, given Earth’s position in the galaxy.

Using models of star formation and evolution, the astronomers calculated when specific regions of the galaxy would have been inundated with killer radiation. Early on in our galaxy’s history, the inner galaxy out to about 33,000 light years was alight with intense star formation, which rendered it inhospitable. At this time, the galaxy was frequently rocked by powerful cosmic explosions, but the outermost regions, which had fewer stars, were mostly spared these cataclysms.

Until about 6 billion years ago, most of the galaxy was regularly sterilised by massive explosions. As the galaxy aged, such explosions became less common. Today the mid-regions, forming a ring from 6,500 light years from the galaxy’s centre to around 26,000 light years from the centre, are the safest areas for life. Closer to the centre, supernovae and other events are still common, and in the outskirts there are fewer terrestrial planets and more gamma-ray bursts.

Luckily for us, our galactic neighbourhood is getting more and more life-friendly. In the longterm galactic future, there will be fewer extreme events nearby that could cause another mass extinction from space.

“For planets close to the stellar explosion, it’s plausible that there is a complete sterilisation”

Riccardo Spinelli