Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific developments and more.
Not all science is conducted by people in white lab coats under the fluorescent lights of academic buildings. Every now and then the trajectory of the scientific record is forever changed in a pub over a pint of beer.
Such is the case for the overwhelming purple and green lights that can hover above the horizon in the Northern Hemisphere. The phenomenon resembles an aurora, but is actually something completely different.
It’s called Steve.
The rare light show has caused a bit of a stir this year as the sun enters its most active period, increasing the number of dazzling natural phenomena appearing in the night sky – and leading to new reports of people seeing Steve in areas where it is is the case. are generally not found, such as parts of the United Kingdom.
But about eight years ago, when Elizabeth MacDonald, a space physicist at NASA’s Goddard Space Flight Center, was in Calgary, Alberta, for a seminar, she had never seen the phenomenon in real life. And it didn’t have a name yet.
In fact, few scientists actively studying auroras and other night sky phenomena had witnessed a Steve, which appears closer to the equator than auroras and is characterized by a purple-pink arc accompanied by green, vertical stripes.
After giving a talk at a nearby university, MacDonald met some citizen scientists – mostly photographers who spend nights hoping to capture the next stunning image of colors dancing in the Canadian sky – at the Kilkenny Irish Pub.
“I had already contacted the local aurora hunters in Alberta (in) a Facebook group, which was quite small at the time,” MacDonald said, “but was very keen to share their observations and communicate with NASA.”
The photographers arrived with their photos in hand, eager to show off the mysterious light show they had captured.
Naming the spectacle
At the time, “we don’t know exactly what it was,” MacDonald said of the phenomenon seen in the footage.
Neil Zeller, a citizen scientist or expert in photography – as the aurora-chasing photographers are sometimes called – was at that meeting.
“I started discovering what we used to call a proton arc in 2015,” Zeller said. “It had been photographed in the past but misidentified, and so when I attended that meeting in the Kilkenny Pub… we were discussing a bit about (whether) I had seen a proton arc.”
Dr. Eric Donovan, a professor at the University of Calgary who was in the pub with MacDonald that day, assured Zeller that he had not seen a proton arc, which, according to a paper Donovan later co-authored, “is subvisual, broad and diffuse.” ‘whereas a Steve’ is visually clear, narrow and structured.
“And the conclusion of that night was, we don’t know what this is,” Zeller said. “But can we stop calling it a proton arc?”
Shortly after that pub meeting, another aurora hunter, Chris Ratzlaff, suggested a name for the mysterious lights on the group’s Facebook page.
Members of the group were working to better understand the phenomenon, but “I suggest we call it Steve until then,” Ratzlaff wrote in a February 2016 Facebook post.
The name is taken from “Over the Hedge,” the 2006 DreamWorks animated film in which a group of animals are frightened by a towering green bush and decide to name it Steve. (“I’m a lot less afraid of Steve,” declares a porcupine.)
The name stuck. Even after the phenomenon could be better explained. Even after explanations for Steve began to take shape in scientific articles.
Scientists later developed an acronym to fit the name: Strong Thermal Emission Velocity Enhancement.
And that meeting in a small Canadian pub was a turning point.
“That was the face-to-face meeting that was one of the parts that gave it more momentum to eventually collect more and more observations in a more and more rigorous way so that we could correlate those with our satellite,” MacDonald said.
What is Steve?
Ultimately, MacDonald said a satellite directly observed a Steve, collecting crucial data and leading to a 2018 study that suggested the lights are a visual manifestation of something called subauroral ion drift, or SAID.
SAID refers to a narrow stream of charged particles in the Earth’s upper atmosphere. Researchers already knew SAID existed, MacDonald said, but they didn’t realize it could occasionally be visible.
Steve is visually different from auroras, which are caused by electrically charged particles that glow when they interact with the atmosphere and appear as dancing ribbons of green, blue or red. Steve is – if caused by SAID – largely made of the same stuff. But it appears at lower latitudes and appears as a streak of mauve-colored light accompanied by distinctive green bands, often referred to as a picket fence.
Steve can be frustratingly difficult to spot and appears next to auroras with little regularity. Sometimes seeing Steve is a matter of luck, says Donna Lach, a photographer from the Canadian province of Manitoba.
Lach has seen and photographed Steve about twenty times, a rare feat in the world of aerial photography. She said she uses her family farm on a remote plot of land in southern Manitoba where there is little to no light pollution.
She always checks the space weather before heading out. She looks for conditions that are at least Kp3 – an index of space weather that ranges from Kp0 to Kp9, with higher numbers indicating more activity.
It appears, Lach said, that the phenomenon begins with the SAR arc — a stable red polar arc — visible near the auroral oval.
“It may eventually migrate south… to the equatorial side of the aurora and form a Steve,” Lach said.
A Steve will always appear next to an aurora, Lach and Zeller said, but not all auroras have a Steve present.
Where and how to see Steve
Earth is entering a period of increased solar activity, or solar maximum, which occurs about every eleven years, MacDonald said.
During this time, spectators can expect more visible light shows in the sky and – possibly – the chance to witness a Steve at low latitudes. Light phenomena have been seen as far south as Wyoming and Utah, she said.
“There have been recent storms that have been visible across the U.S. – just a little bit – as far away as Death Valley,” MacDonald said. “And recently the one in November … was visible at its southernmost point over Turkey, Greece and Slovakia, and even in China, which is very rare.”
However, Steve is best seen through the lens of a camera.
To the naked eye, it can appear as nothing more than what appears to be a faint contrail of an airplane streaking through the sky, Zeller and Lach noted, and it can be easily overlooked.
Cameras are much more sensitive to light and capture Steve’s vibrant colors through their lenses.
Even a phone camera can work, MacDonald added.
“This is the first solar maximum, I would say, where most people’s cell phones can take a good photo of aurora,” she said.
According to Zeller and Lach, the Steve phenomenon will likely be captured around the spring and fall equinoxes. (This year’s autumnal equinox occurred on September 23.)
“I don’t think it’s Steve that is more common during the equinox, but larger aurora storms are known to occur more frequently around the equinoxes,” MacDonald noted. And because Steve tends to appear next to aurora, the phenomenon is more likely to be observed in March or September.
Zeller and Lach said they typically see Steve between the evening and midnight.
“It’s not an all-nighter thing,” Zeller said. “The longest duration I’ve seen Steve was an hour from start to finish.”
Zeller added that he waits until an Arctic storm begins to subside before pointing his camera east — from his vantage point in Canada — or straight up, and then “you start to see this purple river.”
That’s Steve.
How do you become a citizen scientist?
MacDonald encourages anyone interested in photographing auroras (or a Steve) to get involved in online communities. Aurorasaurus, a website that connects photographers with scientists, is a project she says she cares deeply about, noting its crucial role in helping scientists formally identify Steve.
The photos contributed by the public continually help scientists improve their understanding of these light shows, she said.
“Scientists are not as good at aurora hunters as the passionate public,” she said. “We don’t stay up all night, and we’re not photographers either.”
For more CNN news and newsletters, create an account at CNN.com