Chalk One Up for the Little Guys -- Three Amateur Astronomers Make a Major Discovery of a Never-Before-Seen Filamentary Emission Nebula – How Did They Do It?

Posted by Guy Pirro   01/12/2024 10:16PM

Chalk One Up for the Little Guys -- Three Amateur Astronomers Make a Major Discovery of a Never-Before-Seen Filamentary Emission Nebula – How Did They Do It?

An international team of amateur astronomers and scientists made a surprising discovery in August 2022. In a cross-national collaboration, the researchers and amateur astronomers studied a newly discovered giant nebula. The arc has an extent of about 1.5 by 0.45 degrees, is only 1.2 degrees from the center of M31, and is located southeast of the main body of the Andromeda galaxy. It may be the largest structure of its kind in the near vicinity in the universe. M31 is undoubtedly one of the most photographed deep sky objects ever. This makes the discovery of such a large structure in close proximity to the galaxy all the more surprising. The [OIII] emission arc appears extremely bright in the photographs, but it is an extremely faint object that can only be adequately visualized by special subtraction techniques, since the signal in the unprocessed state is almost completely outshone by the light from the galactic halo of M31. The exact origin of the [O III] emission is still unclear. (Content Credit: Royal Museums Greenwich, Astronomy Photographer of the Year 2023)(Image Credit: Marcel Drechsler/Xavier Strottner/Yann Sainty)


Chalk One Up for the Little Guys -- Three Amateur Astronomers Make a Major Discovery of a Never-Before-Seen Filamentary Emission Nebula – How Did They Do It?

With hundreds of major observatories worldwide surveying the sky and extremely high-tech camera-equipped space telescopes zipping around the Solar System, one could expect that there's nothing left in space for an amateur astronomer to discover. 

Yet in 2022 three creative amateur astronomers/astrophotographers made a remarkable find in one of the most observed and photographed areas of the night sky – the Andromeda Galaxy. 

Marcel Drechsler, Xavier Strottner, and Yann Sainty discovered and photographed a never-before-seen Oxygen-III (OIII) emission arc next to our nearest spiral galaxy. 

The hours of hard work put in by these passionate amateurs earned them the top prize in the Astronomy Photographer of the Year 2023 competition, the world’s biggest space photography competition. It also earned them a place in the history books as the discoverers of a new filamentary emission nebula -- the Strottner-Drechsler-Sainty Object 1 (SDSO-1).

Competition judge László Francsics said of their image, “This astrophoto is as spectacular as it is valuable. It not only presents Andromeda in a new way, but also raises the quality of astrophotography to a new level.” 



What did the team discover?

The Andromeda Galaxy (also known as M31) is the closest large galaxy to our Milky Way Galaxy at around 2.5 million light years away. 

The earliest known photograph of the Andromeda Galaxy was taken over 130 years ago in 1888 by Isaac Roberts. Since then it has been a hugely popular target for astrophotography. 

In August 2022, the three amateur astronomers/astrophotographers discovered a ‘huge plasma arc’ in its vicinity, recognizable as the slightly-curved blue cloud to the left of the Andromeda Galaxy.

Firstly, what is plasma? Plasmas have some similarities to gases, consisting of freely moving atoms which, through high temperature or radiation, have become split from some or all of the electrons that make them up. The result is a soup of electrons and partially ionized nuclei which gives them some weird properties.

Ninetynine  per cent of the visible universe is made of plasma - We can see it in the form of stars, nebulae, solar wind, comet tails, the aurora, and more. 

“What you see is gigantic blue arc of ionized oxygen gas that has never been seen before,” amateur astronomer and astrophotographer Marcel explains.  

The arc is an ‘emission nebula’, which is a cloud of ionized gas that emits its own light at an optical wavelength (UV, visible, or infrared). Stretching 1.5 degrees across the sky, it appears to be almost half the size of the Andromeda Galaxy.  

“As a result, it could be the largest and closest such structure to us in the Universe,” the team wrote in their application to Astronomy Photographer of the Year 2023. 

The arc has now been named the Strottner-Drechsler-Sainty Object 1 (SDSO-1). Scientists worldwide are collaborating to investigate the arc further, including its potential relationship to its neighboring galaxy. 

Why hasn’t this been seen before?

“Over 100 years, nobody has seen the arc because it's so faint and it's only visible in Oxygen 3 (OIII),” Marcel explains.

When gases like hydrogen, sulfur, and oxygen are superheated they glow in various colors, with oxygen giving off a blue color.

Telescope narrowband filters allow astronomers to look at the light from certain gases, with the most common filters being Hydrogen Alpha, Hydrogen Beta, Sulfur 2, and Oxygen 3.  

As three quarters of gas in the Universe is hydrogen, astrophotographers tend to take photos using a Hydrogen Alpha (Hα) filter in order to see this type of light. 

Oxygen, by contrast, makes up just 1% of gas in the Universe and is extremely faint, making it difficult to see.  

Photographs taken with an Oxygen 3 filter are also subject to distortions from factors such as light pollution, meaning fewer astrophotographers choose to use it.

However, for those willing to put in the long exposure times required to take photographs in Oxygen 3, many discoveries await.  

“The arc is not very easy to capture. You have to be an ambitious astrophotographer to catch this arc,” Marcel says. 

Bright oxygen clouds have already been discovered in other nebulae such as the Veil Nebula, where oxygen gas is heated, ionizes, and glows blue. 

An unexpected discovery 

So how did the team find it? Marcel explains: “It was an absolute accident. No one expected to see it and that's why it (the prize-winning image) is called Andromeda, Unexpected, because we wanted to take a beautiful image of the Andromeda Galaxy. And we looked at the first data and we spotted this hazy smudge on the edge of the image.” 

The astrophotographers originally thought the smudge could be an ‘artifact’, an anomaly or distortion which shows up on images due to interference from things like light pollution, satellite trails and scattered light. 

After much discussion, however, “we came to the conclusion no, it's not an artifact. It's real. It's a new discovery,” Marcel says. 

But why haven’t any of the extremely sophisticated cameras up in space spotted this? Essentially, while space telescopes take extremely valuable photographs, they have limitations in their scope. 

“We amateur astronomers can capture what Hubble and the James Webb Space Telescope can't because they only capture a teeny tiny fraction of the sky,” Marcel explains. “With our small and not-so-expensive telescopes, we are able to capture a wide field image of the night sky.” 

“We are faster than Hubble, we have a wider field than Hubble, and we can do more exposure times than Hubble. When you have a very tiny, bright nebula, you call Hubble, but when you have a very faint big object in the Milky Way, you call us amateur astronomers.” 

He explains that thanks to increasingly sophisticated equipment available, amateurs can act as the eyes and ears of professional astronomers due to their passion, dedication, and time. 

How did they take the photo?

Each member of the team brought their own specialism to the table to create Andromeda, Unexpected.

Marcel explains: “Xavier is a very good researcher and analyst and Yann is doing a great job in capturing the data. My part is the image editing; I'm taking the raw data and I'm making a beautiful image out of that.”

According to amateur astrophotographer Yann, “It’s a sharing of knowledge which results in everyone learning new things.” 

Firstly, Marcel and amateur astronomer Xavier discovered a potential planetary nebula and they commissioned Yann to shoot the data. 

Yann wanted to experiment and shot Andromeda with a special filter, hoping to discover a planetary nebula. But what Marcel and Xavier discovered in the data exceeded their expectations. 

Yann took photos of Andromeda using a range of filters. Upon sending the data to Marcel and Xavier, they noticed something very faint that merited further investigation. 

As a result, over a period of 22 nights, Yann diligently captured around 110 hours of data in various filters with a range of exposure times.  

Weather was an issue. Yann had to follow the weather from the north to the south of France, travelling each day to various locations that would allow a clear sky that night.  

Stacking Yann’s images taken with various exposure times allowed the team to create a ‘median’ image, toning down the noise from individual images. It also allowed them to filter out other blue-light emitters that were showing up in the Oxygen 3 filter. 

Yann’s raw data was handed over to Marcel, who processed the image: “For me as the picture editor in the team, it's most important to combine the aesthetic of astrophotography with the scientific aspect and merge it together to make it a ‘Wow’ image.” 

Yann reminisces: “The first time we saw the image we were blown away, as much by the arc as by the detail in the galaxy.” 

Data from five other telescopes in France and the USA verified the presence of the oxygen arc. 

The importance of collaboration

For Marcel, Xavier, and Yann, it was astrophotography that brought them together.

Marcel says, “Our group first met on the internet and since then we have worked together on projects remotely.” 

The team became good friends during the process of discovering the arc and learned a lot from each other, despite living far away from each other.

“We have very much the same vision, the same values. It’s very enriching to work with people like this. It was a privilege for me to work with them and get their expertise,” says Yann, who is a relative newcomer to astronomy, having taken up astrophotography in 2020 during the coronavirus lockdowns. 

The team working on the discovery has since expanded from the three photographers to include astrophysicists, astrophotographers, and scientists worldwide. 

This includes Robert Fesen, Professor of Physics and Astronomy at Dartmouth College in the USA, who was the scientific lead, alongside Professor Stefan Kimeswenger of the University of Innsbruck. Michael Shull, Professor of Astrophysics of the University of Colorado, and Professor Quentin Parker of the University of Hong Kong also provided scientific support. 

Astrophotographers Bray Falls, Christophe Vergnes, Nicolas Martino, and Sean Walker meanwhile provided astrophotography support. 

“For me, the most important message is to work together in different languages, across borders, with an international community,” says Marcel. “To combine these skills and these people around the globe made this image and this discovery possible.” 

What is the significance of the discovery for amateur astronomy?

This discovery reiterates the value of amateurs in the field, and astrophotography as both an art and a science.  

Amateur astronomers “can say we are the eyes of modern research,” suggests Marcel. 

“There are thousands of us, we have a lot of time, we have good equipment, and we are spread around the globe. It's the sheer number and the passion of us amateurs that makes the difference.”  

For those with the time and interest in astrophotography, Yann advises people not to wait. “I would say to everyone interested in astrophotography to not hesitate to take it up. Try with whatever equipment you can. With a little bit of training and learning, it can be accessible to you. It opens up marvelous doors.” 

Xavier adds: “To be able to have our name on this object forever, that’s a real legacy for the future.”


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