Astronomers get rare chance to see ancient galaxy’s demise

The primordial gas of the Little Cub dwarf galaxy is being stripped away by its much larger neighbour


This the spiral galaxy NGC 3359, situated 50 million light years from us. Image credit: NASA/ESA/HST

The mammoth spiral galaxy NGC 3359 has been caught devouring its ancient neighbouring dwarf, the Little Cub galaxy. While astronomers observe the gas being stripped from the Little Cub, they also believe the pint-sized structure could provide clues about the early universe.

The Sloan Digital Sky Survey (SDSS) originally discovered the gas-rich dwarf galaxy, but further examination was required. This prompted the combined use of the 3-metre Shane Telescope at the Lick Observatory, and the 10-metre telescope at the W.M. Keck Observatory.

Astronomers have deduced that the star forming gas in the Little Cub is being stolen due the gravity of NGC 3359, eventually the dwarf galaxy will have no material to continue forming stellar generations. Although that may sound depressing, astronomers are excited as they get the rare chance to observe the galactic demise.

This false colour image shows NGC 3359 and the contours for the Little Cub, both are separated by 200 – 300 thousand light years of space. Image credit: SDSS Collaboration

“We may be witnessing the quenching of a near-pristine galaxy as it makes its first passage about a Milky Way-like galaxy. It is rare for such a tiny galaxy to still contain gas and be forming stars when it is in close proximity to a much larger galaxy so this is a great opportunity to see just how this process works.” Says Tiffany Hsyu, a graduate student in the Department of Astronomy & Astrophysics at UC Santa Cruz. “Essentially the larger galaxy is removing the fuel that the Little Cub needs to form stars, which will eventually shut down star formation and lead to the smaller galaxy’s demise.”

Astronomers also believe that the gas that makes up this dwarf galaxy originates from the same gas expelled from the Bin Bang, as it seems to have been unaffected by its surroundings. Dr Ryan Cooke of Durham University’s Centre for Extragalactic Astronomy says, “We know by studying the chemistry of the Little Cub that it is one of the most primitive objects currently known in our cosmic neighbourhood.”

Cooke continues: “By measuring the relative number of hydrogen and helium atoms in the Little Cub we might be able to learn more about what made up the universe in the moments after it began 13.7 billion years ago.” Hopefully this provides a platform to find more pristine galaxies that can explain the early universe.

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