How big is Virgo Cluster? | Scale of the Universe

The Virgo Cluster is the nearest large cluster of galaxies, a crowd of about 2,000 galaxies about 54 million light-years from Earth. Its main body is about 11 to 14 million light-years across, depending on where the edge is drawn. A light-year is the distance light travels in one year, about 9.46 trillion kilometers.

Size

A galaxy cluster has no sharp edge, so its size depends on which part is measured. The center of the Virgo Cluster is usually placed at its giant galaxy M87.

A 2020 study found that within about 1.7 megaparsecs of the center, the cluster's gravity holds galaxies in orbit. A megaparsec is a million parsecs, about 3.26 million light-years. That region, inside what astronomers call the virial radius, is about 11 million light-years across.

A 2001 study weighed the cluster using the galaxies within 8 degrees of M87 on the sky. At the cluster's distance, 8 degrees reaches about 2.2 megaparsecs from the center, which makes the cluster about 14 million light-years across. The cluster is also deep. Hubble Space Telescope measurements of its elliptical and similar galaxies found them spread over 2.4 megaparsecs, about 8 million light-years, from front to back.

Farther out, galaxies are still falling toward the cluster. Its pull wins over the expansion of the universe out to about 7.0–7.3 megaparsecs from the center, or 23–24 million light-years.

Size comparisons

Seen from Earth, the region inside the virial radius is about 12 degrees across, about 23 times the width of the full Moon.
The main body is about 110–140 times as wide as the Milky Way, which is about 100,000 light-years across.
It is 4 to 6 times as wide as the distance from the Milky Way to the Andromeda Galaxy, about 2.5 million light-years.
The cluster is roughly twice as wide as the Local Group, the group of galaxies that includes the Milky Way, but it has about 330 times as much mass.
If the Milky Way were shrunk to the size of a basketball, the main body of the cluster would be 27–34 meters (87–113 feet) across, and it would be about 130 meters (420 feet) away.

Its galaxies

M87, a giant elliptical galaxy at the center, is the cluster's dominant member. It is also a radio galaxy, one that gives off strong radio waves, and in that role it is called Virgo A. Charles Messier found M87 in 1781. Ten years earlier he had found M49, the first object discovered in the Virgo Cluster.

The cluster is made of several clumps. The largest, around M87, is about 16.7 megaparsecs from Earth, and a smaller one around M49 is about 16.4 megaparsecs away. Because the cluster covers so much of the sky, it was left out of the two main catalogs of galaxy clusters, published in 1958 and 1961.

Its pull on the Local Group

Measured from the motions of its galaxies, the main body of the cluster has about 630 trillion times the mass of the Sun. Its gravity also slows the Local Group as the universe expands. A 2020 study found that the Local Group is falling toward the Virgo Cluster at about 135 kilometers per second, compared with where the expansion alone would carry it.