This brings a whole new scope to the concept of stealth. A typical secret maneuver on this planet might cover a few miles or so. But when an entire galaxy starts creeping, it has a space of 59 million light years to cover. That’s almost six trillion miles, the approximate distance between the galaxy Messier 90 and our own Milky Way. While we’re not anticipating imminent collision or anything, M90 is getting closer. And astrophysicists say it is a bit weird for the galaxy to be moving in our direction.
A stunning bit of photographic evidence of the light year leaping MS90 was published as the Hubble Space Telescope’s “Picture of the Week” in May 2019. This sophisticated snapshot came from NASA/ESA Hubble Space Telescope’s Wide Field and Planetary Camera 2, which did its work between 1994 and 2010. Part of the time it focused on the constellation of Virgo and its colossal Virgo Cluster, according to a statement from Hubble. And along with the glamor shots, the camera provided NASA scientists information that helped them realize M90 was bucking the trend and moving closer to the Milky Way. Here’s how and why that one galaxy is going rogue:
One of Messier’s many objects
M90 is a spiral galaxy, part of the Virgo Cluster, and quite simply bright and beautiful. The “arms” in its spirals don’t have many stars, but the trillion stars and 1,000 or so globular clusters in its bright core more than compensate. Messier 90 is one of the many “objects” that still go by the catalog number assigned by French astronomer Charles Messier starting in 1760. He found M90 in 1781 while examining some of the other 2,000 or so galaxies that make up the Virgo Cluster. Messier is also credited as the first in France to observe the projected return of Halley’s Comet in 1758. While his 1781 discover is both bold and beautiful, what sets it apart in the 21st century is its path. Unlike most its peers, M90 appears to be making its way towards the Milky Way instead of away from it.
How cameras caught M90 creeping
The Hubble camera was able to help scientists detect M90’s unusual Milky-Way bound motion because the galaxy gave off a certain type of light. The term is “blueshifted,” according to the Hubble statement. “In simple terms, the galaxy is compressing the wavelength of its light as it moves towards us, like a slinky being squashed when you push on one end. This increases the frequency of the light and shifts it towards the blue end of the spectrum. As our Universe is expanding, almost all of the galaxies we see in the Universe are moving away from us, so we see their light as redshifted, but Messier 90 appears to be a rare exception.”
How to explain this galaxy’s unique path? Astronomers point back at the Virgo Cluster. Its stupendous mass is responsible for “accelerating its members to high velocities on bizarre and peculiar orbits,” the Hubble statement concluded, “sending them whirling around on odd paths that take them both towards and away from us over time. While the cluster itself is moving away from us, some of its constituent galaxies, such as Messier 90, are moving faster than the cluster as a whole, making it so that from Earth we see the galaxy heading towards us.”
See the M90 show each May
It’s not like M90 will get dramatically closer to earthlings in our lifetimes. But it’s still worth trying to get a look at this stunning spiral galaxy in the night sky. May is when amateur astronomers only need binoculars to see M90, as long as the sky is clear and dark. For an enhanced view featuring the bright core and arms, telescopes are helpful. But to know that it’s moving ever closer to the Milky Way? For that, you’d need your own Hubble Space Telescope and maybe an astrophysicist or two.