Scientists Believe A Black Hole Just Launched A Star Cluster Toward Earth
Being able to report science news of the magnitude that we did earlier this week is incredible. Science geeks all over the world speculated rabidly and awaited Monday’s announcement like it was Christmas, which it was, and then some. The only problem with such news — and I’m not complaining, mind you — is that the science news that comes after it may seem a bit less momentous. Not every discovery can be the Holy Grail, though, and of course every discovery about our planet and our universe matters. In the grand scheme of things, we still know far, far less than what we don’t know, and there are even more things we don’t know we don’t know. Such is the awesomeness of space, which has given us a few other amazing stories this week, including the news that there’s a star cluster currently barreling through the cosmos in our direction.
As we’ve reported before, the universe is expanding at an accelerating rate, which is a little bit weird because you’d think that the forces of gravity would produce the opposite effect. Scientists believe that the mysterious force they call dark energy is at least partially responsible for this. Given that the universe is expanding, most points in the universe are getting farther away from Earth. The light from those galaxies gets stretched out as it passes through the increasing distance, which makes their wavelengths appear red — they’re called redshifts. Blueshifts, on the other hand, are just the opposite — light from cosmic entities that is reaching us faster than it used to because, unlike most of the rest of the universe, it’s getting closer.
Scientists recently found a blueshift that trumps all others we’ve ever seen (not counting explosions that might send debris toward us at a faster rate). It’s a star cluster that seems to have been launched our way by a black hole. Blueshifts are common within smaller distances, as the effects of gravity work differently on a smaller scale. The Andromeda Galaxy is a blueshift, headed toward Earth at 300 kilometers per second. One of the stars in that galaxy held the previous blueshift record of 780 kilometers per second, but the star cluster recently detected by scientists has a blueshift of 1,026 kilometers per second.
Astronomers at the Harvard-Smithsonian Center for Astrophysics, the institution responsible for this week’s big announcement, were studying stars’ Doppler shifts in the Virgo Cluster, which is over 50 million light-years from Earth and contains a bunch of galaxies. One of those galaxies, M87, has a black hole bigger than the Milky Way at its center. About a decade ago, scientists learned that when a two-star system gets close to a black hole, one of the stars will tumble into the hole and the other will speed away — it’s called hypervelocity. In this recent case, though, the astronomers think there may be two black holes in orbit around each other, getting pulled together by gravity. The orbital energy they lose would transfer to the star cluster, which would then shoot away from the black holes in our direction. This is the first star cluster to exhibit hypervelocity.
Using the Hubble Telescope, astronomers will try to pinpoint the distance of the cluster to verify that it is indeed closer to Earth than the rest of the M87 galaxy. It won’t hit us — it’s not on a straight trajectory toward Earth and will likely wobble around a bit, setting it up for a future of hanging out in between other star clusters.