Hubble finds two dwarf galaxies heading for the ‘big city’

12 Aug 2016

Hubble captured the glow of new stars in these small, ancient galaxies, called Pisces A and Pisces B (above). The dwarf galaxies have lived in isolation for billions of years and are just now beginning to make stars. Image via NASA, ESA, and E. Tollerud (STScI)

NASA’s most consistently entertaining space mission, the Hubble Space Telescope, has just discovered two isolated tiny dwarf galaxies heading for a ‘big city’ cluster of galaxies.

Coming in from the ‘local void’, an area 150m light-years across, Pisces A and B have travelled through what NASA calls the “vast cosmic wilderness”.

Now approaching their key destination, the young galaxies are set to blow off some steam via a firestorm of starbirth – each had been relatively dormant for billions of years.

Future Human


“These galaxies may have spent most of their history in the void,” said lead researcher Erik Tollerud. “If this is true, the void environment would have slowed their evolution.

The reason Tollerud and his team know A and B are from the void is an abundance of hydrogen in them, a key signifier for young galaxies and a key ingredient to star formation.

“These galaxies seem to retain that more primitive composition, rather than the enriched composition of contemporary galaxies, due to a less vigorous history of star formation.

“The galaxies also are quite compact relative to the typical star-forming galaxies in our galactic neighbourhood.”

Hubble Dwarf Galaxy

Hubble has captured the glow of Pisces A (19m light-years away from Earth) on the left and Pisces B (30m light-years away from Earth) is on the right. Image via NASA, ESA, and E. Tollerud (STScI)

The relatively small number of stars due to form from these two dwarf galaxies is due to that gas make-up. Each galaxy contains about 20 to 30 bright blue stars, a sign that they are very young, less than 100m years old.

“The galaxies could even probably stop forming stars altogether, because they will stop getting new gas to make stars,” Tollerud said.

“So they will use up their existing gas. But it’s hard to tell right now exactly when that would happen, so it’s a reasonable guess that the star formation will ramp up, at least for a while.”

Gordon Hunt was a journalist with Silicon Republic