Crater 2 has been circling “above” our own galaxy.

Researchers from the University of Cambridge made a stunning discovery while scanning the skies – there’s a big galaxy in an uncharted cosmic realm right in the neighborhood of the Milky Way.

Named as Crater 2, after the constellation of Crater, the low-surface-brightness galaxy had been overlooked due to its sheer size: it’s so immense that it ranks as the fourth largest galaxy in orbit around our own. Its orbital path places it directly overhead the Milky Way, allowing the galaxy to remain in obscurity until last year.

A map of the Milky Way neighborhood. Credit: FutureTimeline.net

Nevertheless, now that astronomers have acknowledged its existence, some awkward facts have come to light about Crater 2.

The University of Cambridge scientists explain in a study published in the Monthly Notices of the Royal Astronomical Society last April that despite its size and proximity, Crater 2 is an exceedingly dim galaxy. In fact, it's one of the faintest galaxies ever identified. This, coupled with its more luminous celestial neighbors, allowed this galaxy to remain concealed until this moment.

The discovery of Crater 2 prompts an understanding that our knowledge about the Milky Way’s neighborhood has suffered a serious blow. Perhaps astronomers and space agencies should zoom telescopic lenses on closer objects rather than search for distant galaxies.

Crater 2 is approximately 380,000 light-years from Earth and is a dwarf spheroidal galaxy. Its size is believed to be 6,950 light-years. Crater 2 stars were first studied in 2016 via the VLT Survey Telescope in Chile; it took several years for researchers to realize it was a distinct galaxy.

In 2018, another dwarf galaxy, called Antila 2, was confirmed to be circling at the edge of the Milky Way. 

Read more about Crater 2 in the study “The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater.” 

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