Peak 2020? Scientists say our galaxy is probably colliding with its closest neighbour

CTV National News: An epic cosmic collision Scientists have detected a big bang believed to be the most massive merging of two black holes ever encountered. Vanessa Lee has more.

TORONTO — As if COVID-19, murder hornets and having to confront the painful ennui that is human existence weren't enough, 2020 is now offering us a cosmic calamity as well.

Scientists have found probable evidence that our galaxy has begun to collide with Andromeda, its closest neighbour.

Using the Hubble Space Telescope, an American research team found that the mostly gaseous "halos" around Andromeda and the Milky Way are overlapping each other.

Their findings, which were published last week in The Astrophysical Journal, provide the most detailed glimpse yet at Andromeda's halo and the first evidence that it is touching our galaxy.

Halos at the edge of galaxies contain gases created by supernovas within the galaxy, some of which may be used in the formation of new stars.

Lead researcher Nicolas Lehner, an astrophysicist at the University of Notre Dame in Indiana, said in a press release that Andromeda's halo has two distinct components, which combine to extend approximately two million light-years beyond the galaxy.

“We find the inner shell that extends to about a half million light-years is far more complex and dynamic,” he said.

“The outer shell is smoother and hotter. This difference is a likely result from the impact of supernova activity in the galaxy’s disk more directly affecting the inner halo.”

Only small parts of the outer halo are in contact with the Milky Way, however. Lehner's team found that most of the halo extends for about 1.3 million light-years – much farther than previous estimates, but only about half the average distance to our galaxy.

Scientists have not been able to calculate the depth of the halo of any other galaxy, not even our own. However, Lehner's team says the measurements it recorded of Andromeda's halo leave them confident that it and the Milky Way's halo have "likely" made contact.

It is well established that the two similar-sized galaxies are on a collision course, and will eventually merge to form one large galaxy. This will have far-reaching effects, with more than one trillion stars being flung into different orbits.

There's no reason for anybody alive today to fear the collision, though, as the merger is estimated to be at least four billion years away and will take another three billion years to complete.

By that time, the sun will have turned into a red giant star and grown large enough to engulf the Earth – making everything 2020 has thrown at us seem like child's play by comparison.