Australian Backyard Astronomer Discovers a New Galaxy

“To discover something so faint and so close to such a well researched galaxy like NGC 253 is extra special”

Dwarf Galaxy NGC 253-dw2 and the Sculptor Galaxy: image credit Michael Sidonio


The Great Canary Telescope in Spain is the largest telescope in the world. Its 34-foot mirror can collect light that originated from the edge of our observable Universe. The Hubble Space Telescope with its almost 8 foot mirror has been discovering new objects in the Universe for over 25 years. These machines represent mankind’s pinnacle of scientific and technological knowledge.

And occasionally an amateur astronomer beats them all.

Such was the case when Michael Sidonio from Australia pointed his 12-inch telescope at the dark skies above his home outside Canberra to take images of galaxy NGC 253, commonly known as the Sculptor Galaxy. This spiral galaxy lies in the southern hemisphere just over 11 million light years from Earth and has been observed for many centuries by since its discovery in 1783.

Michael Sidoni's Mt. Cambell Observatory
Michael Sidoni’s ‘Mt. Cambell Observatory’ located in his backyard in Canberra, Australia (Credit: Michael Sidonio)

However instead of zooming into the galaxy like most traditional shots, Michael collected wide-angle images of the galaxy and its surrounding area. After processing the images, he noticed a small smudge in one of the corners of his images. First checking his equipment, and then leafing through various star charts, he could find no origin of the tiny smudge. He eventually turned to other astronomers with much larger telescopes to determine if they could shed some light on what he had captured with his backyard telescope.

What Michael had discovered was a dwarf galaxy currently in the process of being devoured by the much larger Sculptor Galaxy. This dwarf galaxy (now named NGC 253-dw2) lies only 160,000 light-years from NGC 253, a mere stone’s throw away when discussing distances between galaxies. The gravitation force of the Sculptor Galaxy is slowly ripping the dwarf galaxy apart and will eventually consume it.

The existence of NGC 253-dw2 was confirmed by a team of amateur astronomers who run the 31-inch CHART32 telescope in Chile. Further detailed observations of the dwarf galaxy’s structure were made using the gigantic 27-foot Subaru Telescope in Japan. The discovery was published in the Monthly Notices of the Royal Astronomical Society last month.

Discovering a new object in space is the dream of any astronomer – both amateur and professional. Discovering a new galaxy using an off-the-shelf telescope in one’s backyard is both mind-blowing and a once-in-a-lifetime event.

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