Great Bear’s Little Cub is dying, offering answers about the Universe

Scientists have the unique opportunity of studying the death of a pristine dwarf galaxy as it is consumed by its neighbour. 

Some 50 million light years from Earth, in the Ursa Major or Great Bear constellation, lays an ancient dwarf galaxy, fittingly called Little Cub. Astronomers say that this particular galaxy is almost pristine, in the sense that it has changed little over time. But Little Cub is dying out.

The dwarf galaxy is being slowly devoured by its neighbouring galaxy, situated at 200 to 300 thousand light years away. The NGC 3359 as it is called resembles our own Milky Way and it’s slowly stripping off the gases the Little Cub needs to continue its star formation.

Researchers form the University of California Santa Cruz, USA, and Durham University, in the United Kingdom are now monitoring the Little Cub’s faith hoping that it will offer answers about the chemical signature of the Universe just minutes after the Big Bang.

“We may be witnessing the quenching of a near-pristine galaxy as it makes its first passage about a Milky Way-like galaxy,” said lead author Tiffany Hsyu, a graduate student in the Department of Astronomy & Astrophysics at UC Santa Cruz. “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. 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.”

Since the galaxy is pristine, scientists argue that it could contain helium and hydrogen atoms formed during the Big Bang and they plan to study those atoms as they are being illuminated by the small number of very bright stars within the Little Cub.

“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”, said research co-author Dr Ryan Cooke.”Such galaxies, which have remained dormant for most of their lives, are believed to contain the chemical elements forged a few minutes after the Big Bang. 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.”

Scientist are hopeful that other pristine galaxies will be found and they will reveal important clues about the formation of our Universe.

A paper describing the discovery of Little Cub has been submitted for publication in the Astrophysical Journal Letters.