When people think of galaxies, they picture massive areas of space made up of millions, or even billions, of stars. In reality, however, galaxies come in many different shapes and sizes.

The Andromeda galaxy is the closest large-scale galaxy to our own Milky Way. Most large galaxies have smaller galaxies orbiting around them, and that seems to be what a newly spotted dwarf galaxy orbiting Andromeda seems to be.

The galaxy, which has just 40 stars in it, has been named Andromeda XXXVI. It is about 200 light-years across and extremely faint, making it hard to study.

It was first found by amateur astrophotographer Giuseppe Donatiello. He looked through images from the Pan-Andromeda Archaeological Survey, trying to spot what were called “promising, semi-resolved blobs.”

He located two of them in the images, and then teh OSIRIS+ instrument that is part of the Gran Telescopio Canarias took a closer look. This, combined with some modeling, confirmed the discovery.

The details of this study have been published on arXiv and are still waiting to be peer reviewed.

A lot still needs to be learned about XXXVI. The lead author of the paper works at the Astrophysical Institute of Andalusia in Spain. She commented, saying:

“We would need the precision of space telescopes (such as the Hubble Space Telescope) to resolve And XXXVI further and better constrain its distance, age, and metallicity. What is clear, however, is that And XXXVI is one of the faintest satellites of Andromeda found to date.”

While finding such a tiny galaxy may seem unimportant on the surface, it actually provides some important clues that can help to guide future research in many different areas. Sakowski went on to explain:

“And XXXVI points towards the possibility of an extremely faint population of satellites, waiting to be discovered. So far, we know of about 40 dwarf galaxy satellites, of which about 15 are classed as ‘ultra-faint’.

The expected number of dwarf galaxy satellites is not quite certain, as the prediction changes depending on which cosmological model of galaxy formation is adopted. However, following the popular lambda cold dark matter model [i.e. the standard model], some estimates suggest Andromeda should have around 90 satellites.

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Let’s say that we never discover any more satellites after Andromeda XXXVI – this would raise important questions regarding the accuracy of state-of-the-art cosmological simulations of galaxy formation, and even our understanding of the nature of dark matter.”

The partnership between amateur astronomers and those who work with professional-quality telescopes and other equipment is extremely important, and this discovery is a perfect example of why.

Having the help of passionate people throughout the world can help to point the powerful equipment in the right direction so that time and resources are not wasted.

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