The Earth is the only world for us — for now at least. But our planet is dwarfed by the stars and galaxies that make up the universe.
Even our galaxy itself is a mere speck in a larger structure, which was just revealed for the first time by a group of scientists who created a map of more than 8,000 galaxies in an effort to understand where they fit in the universe.
The team discovered that the Milky Way resides on the outskirts of a massive, previously unknown galaxy super-cluster scientists have named Laniakea, from Hawaiian words for “immeasurable heaven.”
The finding, reported in this week’s issue of the journal Nature, stems from a new mapping technique that combines not only the distances between more than 8,000 nearby galaxies, but also their motion as the universe expands and galaxies are pulled through space by gravity.
As a video by Nature explains, the universe can be understood as a network of galaxies — a cosmic web. That leaves a void of vast, empty space in some areas; but super-clusters of galaxies form in other places. These clusters are the largest structures in existence.
The technique enables astronomers for the first time to clearly delineate where one super-cluster of galaxies ends and another begins.
The new maps show that the Milky Way galaxy, along with the Virgo cluster and some 100,000 other galaxies, are gravitationally sailing in the same gigantic cosmic pool, named Laniakea.
Most galaxies are pulled towards the heart of a super-cluster, a dense center called the great attractor. In Laniakea, though our galaxy is far far away on the edge of the system, we’re still being pulled by the great attractor’s gravity.
The super-cluster spans some 520 million light-years in diameter. One light-year is the distance that light, which moves at about 186,000 miles per second (300,000 km/s), travels in one year, or roughly 5.88 trillion miles (9.46 trillion km).
Scientists previously believed the Milky Way galaxy, which is where Earth and the rest of the solar system reside, was part of a cluster measuring about 100 million light-years in diameter. The new study shows that structure is just an appendage of the larger Laniakea.
Bordering Laniakea are the Shapley, Hercules, Coma and Perseus-Pieces super-clusters, though the far edges of the neighbouring galaxy complexes have not yet been determined. Thousands more distance measurements will be needed for that, said astronomer and lead researcher Brent Tully, with the University of Hawaii.
“We haven’t seen the edges of our neighbours and we haven’t seen far enough to understand what’s causing this full motion of our galaxy,” Tully said in an interview.
Having a clear method for identifying super-clusters is expected to help scientists piece together a better idea of how galaxies, including the Milky Way, evolve, astronomer Elmo Tempel, with the Tartu Observatory in Estonia, said in a related Nature commentary.
“Hopefully, this will initiate observational programs to carry out additional direct-distance measurements of galaxies,” Tempel wrote in an email to Reuters.
See Nature’s full video below:
(Reuters reporting by Irene Klotz; editing by Mohammad Zargham)