Aug. 21, 2019

Mysterious STEVE gets ‘mint’ treatment

Celestial phenomenon studied by University of Calgary space physicists turned into silver coin
STEVE aurora
The Royal Canadian Mint has recognized the STEVE phenomenon with a $20 fine silver collectors’ coin. Chris Cully, Faculty of Science

STEVE, a mysterious mauve ribbon of light arcing across the night sky, now makes a lot of cents literally.

The Royal Canadian Mint has recognized the STEVE phenomenon with a new $20 fine silver collectors’ coin. It is the second coin in the mint’s three-coin Sky Wonders series, featuring three different naturally occurring light displays in the sky.

The Mint contacted the University of Calgary Faculty of Science’s Department of Physics and Astronomy, which has conducted extensive research on STEVE, before producing the coin.

“It’s a tangible piece of evidence that something that we’ve done has really connected with people,” says space physicist Dr. Eric Donovan, PhD, professor in the Department of Physics and Astronomy and director of the Auroral Imaging Group at UCalgary. “It’s because so many millions of people have seen the STEVE story and connected with this story.”

STEVE was first reported to scientists at UCalgary and NASA by the Alberta Aurora Chasers. Members of the citizens’ science group have taken spectacular photographs of the unmistakably bright ribbon of light.

STEVE and UCalgary’s research on the phenomenon attracted worldwide attention, from an episode on CBC TV’s The Nature of Things and international media coverage including a story in The New York Times, to numerous UCalgary studies published in scientific journals.

“Here you have a piece of University of Calgary research which has involved and flowed from interaction with citizen scientists, and depended upon those interactions,” Donovan says.

“To see the contributions to science from the Alberta Aurora Chasers community recognized in a collectors’ coin from the Royal Canadian Mint is nothing short of amazing,” says member Chris Ratzlaff, who first named the phenomenon. “The design of the STEVE coin not only accurately reflects the structure of STEVE, but it's also incredibly beautiful and it glows!”

The STEVE coin

The STEVE coin features a design created by Ontario artist Tony Bianco.

Royal Canadian Mint

Design created with digital technology

The STEVE coin features a design created by Ontario artist Tony Bianco. It depicts an engraved lakeside campsite and shining on the horizon is the well-known aurora borealis. Overhead, STEVE’s distinct mauve ribbon, accompanied by characteristic green bands of light, arcs across the dark sky.

“I wanted to make STEVE the star in an already astonishing show,” Bianco says.

Bianco has been creating designs for coins for about 20 years. He once painted on canvas to produce a design, but he now uses several software programs to build a file of digital images that get transferred to the coin. “The great thing about working digitally is that it’s direct,” he says. “I can choose the exact colours that will be printed.”

To make the coin, the Royal Canadian Mint’s engravers digitally sculpt the artist’s design using 3D software, says mint spokesperson Alexandre Reeves. A hydraulic press is used to strike a “blank” (a metal disc with no images) with the images that appear on both sides of the coin. Each blank is cut from a long strip of silver refined to 99.99 per cent purity.

Unlike circulation coins that can be produced at a rate of 800 per minute on a high-speed automatic press, collector coins are manually struck up to three times on a hydraulic press to achieve a flawless, high-relief strike, Reeves says.

Ultraviolet-reactive paint is then applied to achieve the bright, colourful appearance of STEVE, he says. “By shining a UV flashlight over the coin, the visual effect stands out, just as it does in the night sky.”

The STEVE coin, with a limited mintage of 5,000 coins worldwide, is 99.99 per cent pure silver, 38 millimetres in diameter and weighs nearly 32 grams. The other two coins in the Sky Wonders series are Fire Rainbow, issued in June, and Light Pillars, available this October.

STEVE still getting attention

TELUS provided funding for a new 25-minute documentary, Chasing STEVE, made by Vancouver-based All in Pictures. The film, which focuses on the Alberta Aurora Chasers, includes interviews with UCalgary’s Donovan and Dr. Elizabeth MacDonald, PhD, a space physicist at NASA.

In newly published research, UCalgary’s Auroral Imaging group has confirmed its initial findings that STEVE (which stands for Strong Thermal Emission Velocity Enhancement) is not an aurora. Visible aurora are caused by electrons coming down Earth’s magnetic field lines and hitting the upper atmosphere, where they energize atoms and molecules into transition states that emit specific wavelengths of light. 

Using a ground-based spectrograph instrument in Saskatchewan, the research team discovered that STEVE’s brightness is produced across the entire wavelength spectrum, “which cannot correspond just to atomic and molecular transitions,” Donovan notes. “But now we have this mystery because the atmosphere up there is too rarified to have a continual emission.”

So while it’s now possible to hold a version of STEVE in your palm, the real thing remains a touch elusive to coin a phrase.