“Two Trillion!” –The New Hubble Estimate of the Number of Galaxies in the Universe




The observable universe boasts at least 10 times as many galaxies as originally estimated, according to research published on Thursday in The Astrophysical Journal, bring the current estimate of an astounding two trillion individual galactic systems. The surprising discovery is the result of a massive galactic survey mined from 15 years’ worth of deep space observations from the Hubble Space Telescope. An international team led by University of Nottingham astrophysicist Christopher Conselice compiled the Hubble data into a three-dimensional timeline of galactic evolution over the universe’s history.

“It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied,” Conselice said in a statement. “Who knows what interesting properties we will find when we observe these galaxies with the next generation of telescopes?”

Many of these hidden systems are thought to be around the same scale of the many dwarf galaxies that orbit the Milky Way, rather than a large spiral structure like the Milky Way itself, which helps explains why they have escaped notice for so long.




As Conselice observes, we may be on the brink of rooting out these dimmer galaxies with sophisticated new instruments like the James Webb Space Telescope, set for launch in 2018, or the European Extremely Large Telescope, which is scheduled to receive first light in 2024.

In their research, Conselice and his co-authors determined that the number of galaxies is dwindling over time as these massive star systems merge into ever-larger structures. In the universe’s infancy the number of galaxies was another tenfold higher, according to the team.

“These results are powerful evidence that a significant galaxy evolution has taken place throughout the universe’s history, which dramatically reduced the number of galaxies through mergers between them—thus reducing their total number,” Conselice said. “This gives us a verification of the so-called top-down formation of structure in the universe.”

The Daily Galaxy via Hubble Space Telescope


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