We live in a cosmic web. Galaxies gather in clusters and along filaments and large regions referred to as voids, separate them. Laniakea is our home supercluster.
The Sun lives in what’s called the Orion arm in our spiral-armed Milky Way galaxy. Our galaxy is part of a collection of a few dozen galaxies called the Local Group. This whole group is on the outskirts of a much larger cluster of galaxies, called the Virgo Cluster. Virgo is several million light-years across and has more than 1,000 galaxies.
The Virgo Cluster forms the heart of the larger Virgo Supercluster.
In September 2014 a group of astronomers published a new way of defining superclusters according to the relative velocities of galaxies. They made a new cosmic map with an unprecedented look at the boundaries for the giant supercluster. The supercluster is home to our galaxy the Milky Way and to roughly 100,000 other galaxies. Astronomers call this supercluster, the Laniakea, which in Hawaiian means “immeasurable heaven.”
However, scientists are not stopping here. They suggest that the Laniakea supercluster may even be part of a still-larger structure they have not fully defined yet.
“We live in something called ‘the cosmic web,’ where galaxies connect in tendrils separated by giant voids,” said lead study author Brent Tully, an astronomer at the University of Hawaii at Honolulu.
Scientists can see these structures in maps derived from spectroscopic surveys.
Mapping the supercluster
Mapping our local supercluster is not easy at all. That’s because it doesn’t really have a defined edge like a solid planet. It just fades out with distance until the next supercluster comes along. Another difficulty which scientists face is that you need to get the three-dimensional location of the galaxies around us.
To observe thousands of galaxies in the local Universe, scientists had to use radio telescopes. The universe is expanding faster and faster. Thus, galaxies are floating away from us. However, their radio waves lose energy when these galaxies get farther. Astronomers call this loss of energy “redshift”. So, the farther away a galaxy is, the higher the redshift is.