Even though galaxies are huge, it’s not always easy to spot them. As you may know, space is vast, more expanded than the human brain can even fully comprehend. However, astronomers from MIT wouldn’t let the vastness of the cosmos hide objects from humanity. They have discovered several unusual galactic neighbourhoods never observed before. They observed that some galaxy clusters are often misidentified as a single, bright galaxy as they look atypical. Such galaxies amount to roughly 1% of all observations.
A galaxy cluster is one with hundreds to thousands of galaxies that are bound together by gravity. Moving through intracluster medium, a hot mixture of gas, with a mass more than all the stars in all the galaxies within it. This same mixture emits X-rays, forming a fuzzy halo around the clusters, which can be identified by telescopes.
One such cluster was discovered in 2012 by MIT Associate Professor Michael McDonald called the Phoenix Cluster. Shining bright like a point source, it revealed itself in an X-ray observation. It housed a grand black hole, engulfing all matter and emitting energy and X-Rays. It had a blueish hue usually associated with young star population instead of the typical red hue of aging stars. The star forming rate in this cluster is nearly 500 times faster than other observed galaxies.
With this unusual discovery, Clusters Hiding in Plain Sight (CHiPS) survey was born.
Taweewat Somboonpanyakul, from MIT, began by selecting potential candidates from archived X-Ray data. He used data from multiple telescopes including ground-based telescopes in Hawaii and New Mexico, Magellan telescopes in Chile as well as space-based Chandra X-Ray Observatory and Hubble Space Telescope. The six-year long CHiPS survey is finally published in the the Astrophysical Journal.
Three new clusters have been identified in the survey. CHIPS1911+4455 is quite similar to the Phoenix cluster.
“It’s super unique compared to all the galaxy clusters that we now know,” said Somboonpanyakul.
The question to resolve is whether all clusters are strange like the Phoenix or these clusters go through an atypical phase. The newly launched eROSITA X-Ray telescope will possibly add a lot more to our knowledge bank about space but these atypical galaxies could keep getting missed unless these clusters are studied more closely.
“If you miss 1 percent of the clusters, there’s a fundamental limit to how well you can understand the universe,” says McDonald.