How amateur astronomers discovered a never-before-seen nebula around the Andromeda Galaxy

Always try to see things from a different perspective. That may be the moral of this story. Three amateur astronomers caused a surprise when, on Monday, January 9, they announced the discovery of a nebula around the Andromeda galaxy. It is the closest large neighbor to the Milky Way.explains François Hammer, an astronomer at the Paris Observatory. Located 2.5 million light-years from Earth, the Andromeda Galaxy (also called M31) is the best-documented, most viewed, and most studied galaxy.

“The Andromeda Galaxy is the best we know of, perhaps even more so than our own.”

François Hammer, astronomer at the Paris Observatory

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So it’s hard to imagine finding new objects by scanning this part of the sky. However, Frenchman Yann Sainty, a freelance graphic designer and astrophotographer for two and a half years, managed to put his finger on a nebula (a cloud of very hot gas) near Andromeda. It’s the arc seen in this image in blue, to the upper left of the galaxy. Screenshot posted a week later on the NASA blog (in English).

Yann Sainty says that in 2022 he decided to devote himself to “Project Comfort” After completing another grueling and demanding astrophotography job. I chose Andromeda because it is a bright object that is relatively easy to photograph., Slips. To take his shots, he uses a filter that focuses on a specific class of oxygen, which is generally not recommended. “It is accepted that there is no point in firing an oxygen filter on a galaxy because it will do nothing but complicate the treatment.”, he explains. At the same time, he chose to couple this filter with long pauses in the faint hope of capturing a planetary nebula that had not yet been referenced.

Nobody noticed it yet

After eight hours of observation, Jan Senti sent his images to the duo formed by Frenchman Xavier Strutner and German Marcel Drechsler, two amateur astronomers known worldwide as nebula hunters, with some 350 discoveries over the course of the hour. After analysis, the pair indicates “A whiter area in one corner of the image”. “We detected a very weak arc that seemed unknown to us, so we asked him to continue his observations and images to intensify this signal.”Xavier Struttner recalls.

“On my own, had it not been for Xavier and Marcel, I would have thought I had made a mistake, and I certainly would not have seen the arc.”

Jan Senti, amateur astrophotographer

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So the three men embark on a more in-depth search. Living in an apartment without a garden, Yann Sainty doubles round trips to go to remote areas where light pollution is limited. After 22 nights of work, 111 hours of observation, and about 5 000 How far it goes, it gets enough data to clearly highlight the arc.

Once you get this first confirmation, you must make sure that it is not a defect in the monitoring tools used or any other problem. Next, the trio contacted astrophotographers and other scientists (including professionals) spread across several continents to validate the whole thing thanks to additional observations made with different equipment in order to rule out any bias. Checked, the existence of the nebula was well confirmed. American Bray Falls, who was involved in the process, details it in the video below (in English) :

How could this nebula have gone unnoticed in this region of the sky like this ? First explanation Xavier Struttner explains that the most powerful telescopes like those of NASA are largely focused on Andromeda, keeping the nebula out of sight.

“Professional telescopes have very limited fields of view. In their field, we will see the Andromeda galaxy but we will not see its immediate neighborhood. Unlike the telescope that Yan Sinti used, which allows us to see the galaxy M31 but also everything that surrounds it.”

Xavier Strottner, amateur astronomer

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At the origin of this discovery is also a filter used by Yann Sainty, which isolates oxygen lines, along with an extended exposure. “Amateurs have something precious, it’s time”Xavier Struttner notes. In fact, the newly discovered nebula is of such a dim brightness that it can only be seen with long observation ranges, which professionals do not always have the opportunity to do. In the end, this configuration “never happened in the past”The amateur astronomer notes.

supernova remnant ?

If the existence of the nebula is officially determined, only a few items will be available regarding its formation and origin. One thing is for sure : the arc contains doubly ionized oxygen, that is, oxygen molecules that are missing two electrons. It is a chemical element that is regularly found in the interstellar medium.Comments, Xavier Strottner. The presence of any other elements remains to be determined.

The origin and formation of the nebula, dubbed “Strottner-Drechsler-Sainty Object 1,” remain unknown. At this point, we don’t know its exact size, whether it’s approaching or moving away from the Andromeda Galaxy, or even the distance between the two objects. As for its origin, there are several hypotheses on the table. It could be a very old planetary nebula, or the remnant of a supernova, that is, the explosion of a massive star.

Perhaps further analyzes, already underway, will allow more to be known, which is uncertain because the nebula is large and not very bright. Meanwhile, Yann Sainty encourages amateur astronomers to get started.

“We are at a time when the development of more and more advanced equipment means we are at a tipping point, and hobbyists have a bigger and bigger role to play.”

Jan Senti, amateur astrophotographer

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“We have a lot of citizen science developing around research on comets, asteroids, and exoplanets [des planètes hors de notre système solaire]. More and more buffs allow new items to be brought in.”Xavier Strottner, who smiles as he conjures, abounds “Adrenaline Finder, Treasure Hunter”. How to make invitations ?