SSA22 Protocluster

Lore & Background

The SSA22 Protocluster was originally discovered in 1998. In 2005, Ryosuke Yamauchi from Tohoku University in Sendai, Japan, and his colleagues discovered a multifilamentary structure coinciding with the protocluster, announced in 2006. This structure is made up of lyman-break galaxies and large gas bubbles, such as lyman-alpha blobs and lyman-alpha emitters gaseous filaments. Some of the gas bubbles are up to 400,000 light-years across, over twice the diameter of the Andromeda Galaxy. The galaxies and gas bubbles line up along three curved filaments, or arms, that formed approximately 2 billion years after the Big Bang. These filaments were observed with the help of the Subaru and Keck telescopes located on the Mauna Kea volcano in Hawaii.

Reader's Guide

The SSA22 Protocluster and its associated filamentary structure are significant because they represent a very distant object, with astronomers looking at something from 12 billion years ago. The structure is not only incredibly large, measuring 200 million light-years in width, but also very dense: the galaxies located in each of the filaments are four times closer to each other than the universe's average. Before its discovery, astronomers had predicted the existence of a structure like this one. According to computer models, several of the most massive galaxies originated in structures like this, believed to have formed as a result of blobs like those constituent to this structure collapsing under their own gravity. Since the densest areas in the universe are thought to be the places where galaxies formed first, this structure may be one of the earliest to have formed. Some scientists believe that the giant gas bubbles formed after massive stars born in the early universe exploded as supernovae and ejected their surrounding gases.

Did You Know?

• The SSA22 Protocluster is also known as EQ J221734.0+001701.
• The multifilamentary structure coinciding with the protocluster measures 200 million light-years in width.
• The structure was discovered in 2005 by Ryosuke Yamauchi from Tohoku University in Sendai, Japan, and his colleagues.