Hubble Discovers Dwarf Galaxy Playing ‘Where’s Waldo’ in Our Own Backyard

The Hubble Space Telescope recently uncovered Bedin 1, a previously-unknown galaxy hiding in our own galactic neighborhood. This family of stars was found accidentally, as astronomers photographed the globular star cluster NGC 6752.

The Cosmos is filled with objects of many different forms — stars, galaxies, nebula, globular clusters, and other objects to catch the eye of — and distract — astronomers. This was the case here, as Bedin 1 was found “hiding” behind the closer, brighter objects seen in the star cluster.

“The object is classified as a dwarf spheroidal galaxy because it measures only around 3,000 light-years at its greatest extent (barely 1/30th the diameter of the Milky Way), and it is roughly a thousand times dimmer than the Milky Way,” the Hubble Science Team reports.

Bedin 1 seen hiding behind members of the globular star cluster NGC 6752. Image credit: NASA, ESA, and L. Bedin (Astronomical Observatory of Padua, Italy)

This dwarf spheroidal galaxy is believed to be roughly 13 billion years old, and is so far from other galaxies that it rarely interacts with other, similar bodies. These conditions make it a kind of galactic “living fossil.” This remarkable age, if confirmed by further observations, would rank Bedin 1 as one of the oldest galaxies in the Universe.

Astronomers who made the discovery believe Bedin 1 is likely a “loner,” winding its way through space, although it may be a distant satellite of the giant spiral galaxy NGC 6744.

The stars within Bedin 1 are old, and there appears to be little new star formation within the body. The stars within that system consist, mostly, of hydrogen and helium, the main building blocks of the early Universe.

Bedin 1 lies roughly 28 million light years from Earth, and is found in the constellation of Pavo, the Peacock, visible from the southern hemisphere. Bedin 1 sits roughly 2300 times further away from Earth than the globular cluster which blocks it from view.

Bedin 1 seen in perspective — no wonder it remained hidden for so long! Image credit: NASA, ESA, and L. Bedin (Astronomical Observatory of Padua, Italy), and Digitized Sky Survey 2

Dwarf galaxies are the most common type of galaxy in the Universe, containing between 100 million to a few billion stars. This is an extremely small number when compared to the 200–400 billion stars residing in our own Milky Way Galaxy.

As their name suggests, spheroidal dwarf galaxies are close to spherical in shape, but they only contain around 10 percent of the number of stars found in other dwarf galaxies, making them even smaller and dimmer than their already diminutive brethren. Due to the difficulty of finding them, spheroidal dwarf galaxies have only been seen (so far) in our local group of the 40-odd galaxies closest to our home.

The newly-discovered galaxy was seen in images of NGC 6752 taken between September 9–13, 2018, utilizing the Wide Field Channel of the Advanced Camera for Surveys (ACS/WFC) aboard the Hubble Space Telescope.

Analysis of the discovery was detailed in the journal Monthly Notices of the Royal Astronomical Society.