100,000 computer simulations reveal Milky Way’s fate—and it might not be what we thought.
It’s been textbook knowledge for over a century that our Milky Way galaxy is doomed to collide with another large spiral galaxy, Andromeda, in the next five billion years and merge into one even bigger galaxy. But a fresh analysis published in the journal Nature Astronomy is casting that longstanding narrative in a more uncertain light. The authors conclude that the likelihood of this collision and merger is closer to the odds of a coin flip, with a roughly 50 percent probability that the two galaxies will avoid such an event during the next ten billion years.
Both the Milky Way and the Andromeda galaxies (M31) are part of what’s known as the Local Group (LG), which also hosts other smaller galaxies (some not yet discovered) as well as dark matter (per the prevailing standard cosmological model). Both already have remnants of past mergers and interactions with other galaxies, according to the authors.
“Predicting future mergers requires knowledge about the present coordinates, velocities, and masses of the systems partaking in the interaction,” the authors wrote. That involves not just the gravitational force between them but also dynamical friction. It’s the latter that dominates when galaxies are headed toward a merger, since it causes galactic orbits to decay.
Each month, NASA shares its top tips on what to look out for in the sky over the following weeks, and June promises plenty of delights.
Planets … and the moon
The planets are out in force through the month, with Venus, Saturn, Mars, and even Mercury all putting in an appearance.
Weather permitting, you’ll be able to spot Venus — the brightest planet in our solar system — and Saturn in the eastern sky during the couple of hours before dawn each morning throughout June. Notice how Saturn rapidly climbs in the sky each day as the weeks pass by. Aligning with our nearest neighbor, you’ll find the third quarter moon next to Saturn on June 19, and a crescent moon next to Venus just a few days later on June 22.
Look our for the salmon-pink glow of Mars in the couple of hours after sunset toward the west, though NASA points out that it’s noticeably fainter than it was at the beginning of last month.
Around 16-17 June, Mars will appear to pass close to Regulus, the bright star at the heart of the constellation Leo, the lion. While the planets can be seen with the naked eye, grab a pair of binoculars or a telescope to get a decent view of Mars and Regulus appearing as close as the width of the full moon.
Mercury, too, is putting in an appearance this month, though it’ll be at its highest and most visible right at the end, on June 27. Look for it quite low in the west, just as the glow of sunset is fading.
June also offers an ideal opportunity to view the stunning Milky Way galaxy, comprising hundreds of billions of stars, as well as vast amounts of cosmic dust and gas. The Milky Way, of which Earth is a part, appears as a faint band of hazy light arching across the night sky, and it’s a sight to behold. “You just need to be under dark skies away from bright city lights to see it,” NASA says, adding: “What you’re looking at is the bright central core of our home galaxy, seen edge-on, from our position within the galaxy’s disk.” Again, while it’s possible to view the Milky Way with the naked eye, a pair of binoculars or a telescope will significantly enhance what you see.
June solstice
The upcoming solstice, which marks the moment when the sun reaches its northernmost point in the sky, resulting in the longest day of the year in the Northern Hemisphere and the shortest in the Southern Hemisphere, is on June 20.
NASA describes the event as “a consistent astronomical signpost that humans have observed for millennia. Ancient structures from Stonehenge to Chichén Itzá were built, in part, to align with the solstices, demonstrating how important these celestial events were to many cultures.”
It adds that if you find a quiet spot to watch the sunset on this special day, “you’ll be participating in one of humanity’s oldest astronomical traditions, connecting you to observers across thousands of years of human history.”
