Our galaxy is headed for an inevitable collision with its largest neighbor, the starry Andromeda! This calamity has been theorized by renowned physicists and astronomers for decades now and the speculations seem to predict a colossal change in the very nature of these galaxies, staying true to the gargantuan event itself. When the space dust of the catastrophic event clears, the galaxies are expected to look monumentally different from their parent form. The first contact is expected to happen in a billion years or so (you can relax now) and the two galaxies are expected to merge and form a large elliptical formation.
However, recent developments and research pertaining to the measurement of stars within Andromeda, made by the European Space Agency’s Gaia space telescope, are changing predictions for when, and exactly how, that collision will go down. An astronomers report in the Astrophysical Journal originally predicted the crash date to be 3.9 billion years from now. Scarily, that number has been reduced by 600 million years. While the number is of little importance relative to the average life span of a human, it is quite a monumental number in space time. However, one might envision the collision to be head on, more like rams fighting. To put things into perspective, the nature of the collision is expected to mimic one knocking off a vehicle’s rear view mirror.
“The overall picture is not too different,” says study author Roeland van der Marel of the Space Telescope Science Institute. “But the exact orbital pathways are different.” We humans are accustomed to a way of trying to prevent catastrophes by devising logical solutions and means for potential damage control. Sadly, some events such as this are inevitable. They just follow the course of nature.
Andromeda, which is currently 2.5 million light-years away, is hurtling toward the Milky Way at nearly 250,000 miles an hour. Astronomers have known this since Vesto Slipher first aimed a telescope at Andromeda and measured the galaxy’s motion in 1912. With revised technology, astronomers used the Hubble Space Telescope to examine the sideways motion of the Andromeda galaxy. This was an attempt to evaluate and predict the nature of the collision. “It is interesting, even though it is in some ways a fairly minor modification of what was known previously,” says Brant Robertson of the University of California, Santa Cruz.
That raises another question doesn’t it? What did Hubble do differently in comparison to Gaia? Gaia observed 1,084 of the brightest stars within Andromeda and measured their motions. Then, van der Marel and his team averaged those observations and calculated Andromeda’s rotation rate for the first time, as well as making new calculations of the galaxy’s side-to-side movement.
With those new numbers, the team re-derived Andromeda’s trajectory using computer models. When the galaxy was put on “fast forward”, it took a more tangential path towards the milky way, deviating from the head on collision theory. “Since we’re talking billions of years here,” she says, “even slight changes in the current motions can play out very differently when ‘fast forwarded’ over eons.”
So how will this gargantuan showdown unfold? We can assure you that it’s not the picture you have in mind. At their first close approach, the two galaxies will be about 420,000 light-years apart. Arguably, this is a safe distance away from the heart of both galaxies. So what could possibly be drawing them in? The answer to this is dark matter!
This mysterious and enigmatic cosmic form is theorized to cause friction between the two galaxies and make them lose energy. “That (dark matter) causes friction, which causes them to slow down and lose energy—and fall back together,” van der Marel says. In other words, the galaxies will U-turn and actually collide, pass through one another, whip around, and collide again. This will happen over and over until eventually those collisions have sculpted them into a single galaxy.
But hey, we as humans have one question running through our heads now? “How is this going to affect our existence?” Truth be told, we really have nothing to worry about, yet. It quite depends on the life forms that exist on this planet after the staggering time period of 4.5 billion years. “We would still find ourselves orbiting the sun on a more randomly oriented orbit within a large elliptical galaxy,” van der Marel says.
In predictive terms, as the galaxies move closer to one another, we are to behold a mesmerizing sight in the sky marking the shimmery galaxy’s entry. Andromeda will grow bigger and bigger in the night sky, eventually distorting into a deformed spiral as the Milky Way’s gravity tugs on it. Then, as the galaxies begin boomeranging and smashing together, compressed gases will ignite bursts of new star formation.
While it will certainly be a spectacular sight to behold, we question if any life forms will even exist on our beloved planet to experience this cosmic interaction. It certainly seems unlikely as this period marks the evolution of the Sun into a red giant star. As that happens, it will brighten and project outward, engulfing Mercury and Venus and reducing our beautiful planet to nothing more than the substance found in pencils! *Shivers*