Astrophysicists have discovered that an object discovered by an amateur astronomer is actually a new dwarf galaxy.

Astronomy enthusiast Giuseppe Donatiello discovered the galaxy while searching through publicly available astronomical data collected in the DESI Legacy Imaging Surveys conducted by a range of different telescopes.

The findings were followed up by professional astrophysicists, led by Dr. David Martinez-Delgado from the Instituto de Astrofisica de Andalucia, who used deeper images taken with the Telescopio Nazionale Galileo to confirm the dwarf galaxy.

Designated as Pisces VII/Triangulum III (Pisces VII/ Tri III) the dwarf galaxy is either an isolated dwarf galaxy, or it is a satellite galaxy of Messier 33 (M33), also known as the Triangulum galaxy (M33) located around 3 million light-years from Earth.

If Pisces VII/ Tri III is isolated, it will be the faintest field galaxy—a galaxy that doesn’t belong to a larger group or cluster and is gravitational alone—ever detected.

On the other hand, if the dwarf galaxy is an extension of M33 which lies around 230,000 light-years from its main body, it could act as an important confirmation of current models that describe how galaxies form and evolve. That means, that whichever of these things prove to be true, the discovery is an important one for astrophysics.

“Theoretical knowledge about galaxy formation means we’d expect to see many more little galaxies orbiting the Triangulum galaxy, M33. However, so far it only has one known satellite,” University of Surrey Ph.D. student, Emily Charles, who worked on the investigation, said. “If this newly identified galaxy does belong to M33, it might imply that there are many more that haven’t been uncovered yet as they are too faint to show up in previous surveys of the system.

“M33 currently challenges astrophysicists’ assumptions, but this new finding starts reassuring us that our theories are correct.”

The team, whose findings are published in the journal Monthly Notices of the Royal Astronomical Society, will now attempt to accurately measure the distance to Pisces VII/ Tri III, to assess if how it is moving in relation to M33.

This investigation, which will require further imaging with other telescopes, will tell them if the new dwarf galaxy is a field galaxy or a satellite of M33. Settling this will also help settle on which name the dwarf galaxy keeps, Pisces VII if it wanders the Universe alone, Tri III if it forms part of the larger M33/Triangulum galaxy.

M33 is itself a satellite galaxy, the largest belonging to the Andromeda galaxy. A spiral galaxy like the Milky Way, M33 is also one of the most massive galaxies in the local group also containing our galaxy. With a diameter of around 52,000 light-years, M33 is still only around half the size of the Milky Way, however.

“Deep imaging from Hubble would allow us to reach fainter stars which act as more robust distance estimators, as they have a standard brightness,” team member and University of Surrey Ph.D. student Noushin Karim, said. “To confirm the new galaxy’s movement, we need imaging from an 8m or 10m telescope, like Keck or Gemini.”

Messier 33 The Triangulum Galaxy
The Triangulum galaxy Messier 33(M33). An amateur astronomer has discovered a new dwarf galaxy which is a satellite galaxy of M33.
ESA/M. Durbin/J. Dalcanton/B. F. Williams/NASA



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