Vigilant amateur asteroid hunters keep watch for menacing space rocks

In the Mojave Desert of Southern California, Bob Stephens has a wide view of the cosmos, where space rocks whiz in all directions.

But Stephens is intent on making sense of that chaos. Some of his latest projects: tracking an asteroid he suspects to have a moonlet; co-authoring a couple of scientific papers on asteroids in Jupiter's midst; and observing an unusual asteroid that appears to be tumbling rather than spinning like a top.

It sounds like a full-time job, but this is just his pastime. Stephens, 66, is an accountant, slowly easing into retirement.

"I fell into a bad crowd and got associated with a bunch of professional astronomers," he told Mashable.

People like Stephens are dubbed "amateur asteroid hunters." They live for the thrill of chasing down the rocky rubble left over from the formation of the solar system about 4.6 billion years ago. Most of that ancient detritus is too far away to pose a threat to Earth. But the slim chance of existential crisis motivates many to join the planetary neighborhood watch.

Bob Stephens, an amateur astronomer in California, helps professionals characterize asteroids as a hobby. Credit: Bob Stephens

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Nations are developing warning systems and defense strategies, in case an asteroid or comet should ever meander into an orbit that could jeopardize civilization. As a test, NASA launched a spacecraft in November, known as the DART mission, to intentionally crash into a harmless asteroid in deep space to try to shift its trajectory. DART is expected to strike in late September or early October.

Amateurs used to discover new asteroids left and right, but that period largely ended two decades ago when NASA invested in professional surveys to monitor most of the sky. (These surveys now find hundreds of sizable near-Earth objects annually.) Today there are largely two camps of amateurs: those who confirm asteroids detected by professionals, and those who answer important questions about them, like how fast they rotate, do they have anything circling them, and what do they look like?

Their efforts play a crucial crowd-sourcing role in planetary defense, especially given the limited time at professional observatories to do that research. Scientists know of about 30,000 near-Earth objects right now, including 10,000 over 460 feet wide. Of these giant rocks, they estimate there are some 15,000 more waiting to be discovered.

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Planetary defense

That's why The Planetary Society, a nonprofit organization focused on advancing space science, has awarded over $500,000 in grants to non-professional astronomers to update or enhance their equipment, said Bruce Betts, its chief scientist. Professionals desperately need asteroid hunters to collect precise measurements over hours, days, and even weeks to predict orbits and determine whether objects could ever hit Earth.

"If you take [amateurs] away, you're missing things," Betts said. "That's dangerous in this world."

Asteroid hunters are hard to think of as mere hobbyists. They're not just pulling out a telescope from their closet once a year and pointing it at the sky. Many have built out elaborate observatories, stocked with high-powered telescopes. Where eyepieces used to be, they've mounted sophisticated cameras.

That's what has allowed Stephens, who lives about 100 miles from his group's 13-telescope observatory, the Center for Solar System Studies, to conduct astronomy from home, glancing at his computer screens every half-hour or so.

Few people in this arena actually have their eyes glued to the scopes anymore. With automation and remote capabilities, even the pros are hardly needed on site.

The Center for Solar System Studies conducts research on asteroids with an observatory of 13 telescopes. Credit: Bob Stephens

"The dirty little secret is astronomers who sit in domes all night long, yeah, occasionally [they] reach over and press a button or something, but in reality, you're sitting there cruising on Facebook," said Stephens, who has visited many of the world's large observatories. "You're playing music, you're trying to do anything and everything to stay awake all night long."

Gary Hug, another amateur asteroid hunter, has a shorter commute to his telescopes. One, the Sandlot Observatory, is literally located in his backyard. His club's facility in Northeast Kansas, Farpoint Observatory, is about 20 or 30 miles away. Between the two, he and fellow asteroid hunters have received about 1,000 designations from the Minor Planet Center.

Hug and Stephens' passions for astronomy began in childhood, with both men putting telescopes on hold for love and careers. Their stories mirror each other in surprising ways.

Both received three-inch reflector telescopes as Christmas gifts as kids. Both took astronomy classes in college that reignited the fire. Both consider viewing Saturn and its rings to be one of the "gateway drugs" into their addiction. Both resumed their hobbies in the late 1990s.

Telescopes old and new

For Hug, now 71, his initial interest was less about the cosmos and more about magnification. He was enthralled by looking through the viewfinder and reading a street sign — albeit upside down and backward — from a block away. That love for tinkering and learning how things work drove him to eventually become a machinist, someone who makes tools and parts for mechanical equipment.

Those skills came in handy later when he was building his own backyard observatory. The telescope, protected under a roll-top roof, weighs about 1,200 pounds.

"I put a lot of heavy metal into it," he said. "Not the music so much but just regular, heavy metal."

Gary Hug, 71, works on his backyard telescope in the "Sandlot Observatory." Credit: Gary Hug

By necessity, Stephens had to develop handy skills, too. As a college student living at home, he used his dad's shop tools to build a telescope. Within four years, he had one of the biggest in his astronomy club. He mounted the telescope on a trailer and hauled it around the local mountains, trying to take dazzling pictures of the sky.

"It looked like a cannon, like an artillery piece," he said. "I was always afraid of getting pulled over by the cops."

And both say they couldn't become the asteroid hunters they are today without their wives supporting their expensive and time-consuming hobby. Hug's three children, none of whom have taken up astronomy, have less-than-rosy memories of being pulled out of bed in the middle of the night to stand in the cold and look at what Dad found.

But in 1998, Hug discovered a main-belt asteroid, meaning it is located between the orbits of Jupiter and Mars. He named it after his wife, Cynthia, which helped ingratiate her to his pastime, although she's often snarked about having a "big, fat rock" named after her, Hug said.

Now settled in his retirement, he often leaves the dinner table for the laundry room, where he's "off to save the world again." That's where Hug monitors the telescopes from a computer screen. Many nights he spends five or six hours looking at what's coming through, guzzling coffee and jerking awake to the rumbles and clangs of the washing machine.

He shrugs off sleep, telling himself he'll catch up during the rainy season.

Gary Hug photographed the sky from his backyard in Kansas. Credit: Gary Hug

A potentially hazardous asteroid

But sometimes adrenaline is all he needs to stay up.

One cold, clear night in January 2013, he found a "potentially hazardous asteroid." Most asteroids are of no consequence to Earth, but a small percentage of big ones come within 4.6 million miles of Earth's orbit around the sun. This one was estimated to be at least as big as the Statue of Liberty.

He rushed to submit his data to the Minor Planet Center, which beat the Catalina Sky Survey, a NASA-funded program based at the University of Arizona, by several hours. Like ships passing in the night, he told his wife the news as he crawled into bed and she was starting her day.

To find such a significant and rare object was one of the most thrilling moments in his life. He likens the feeling to panning for gold or finding a diamond in a pile of junk.

"Main belt asteroids, while they're fun to discover, they're kind of a dime a dozen," he said.

Among his accomplishments, Hug also discovered a comet, an icy dirtball that formed in the outer solar system, with a fellow club member, Graham Bell. Now known as Comet Hug-Bell 178P, it's a faint comet whose orbit is determined by the gravitational pull of Jupiter and returns every seven years.

Small world of astronomy

Stephens has accolades, too, (as well as a namesake asteroid), but some of the highlights of his asteroid hunts have been the special people he's met along the way.

Bob Stephens photographs the starry night sky over the Mojave Desert in California. Credit: Bob Stephens

In 2010, he was in Northern Chile at the Cerro Tololo Inter-American Observatory with astronomer Linda French when they spotted 878 Mildred, a main-belt asteroid that became famous for getting lost. The asteroid was discovered in 1916 by astronomers Seth Nicholson and Harlow Shapley, who named the rock after his then infant daughter, Mildred.

Mildred, the asteroid, was rediscovered 75 years later in 1991.

Stephens did a "light curve" on the asteroid, which plots its brightness as it sails through space. Such an analysis can reveal whether an asteroid is alone or has something else orbiting it, how fast it's rotating, and whether it's solid or a loose pile of rubble. A paper published on the analysis stated that the asteroid is part of the "Mildred family," a subgroup of objects composed of perhaps 1,200 members.

Through connections in the tight-knit astronomy community, Stephens learned that Mildred, the person, had not gone off the grid like her asteroid. He sent her a letter with a copy of the paper. Mildred Shapley Matthews had apparently followed in her parents' footsteps, becoming a writer and editor of astronomy books.

"I'm shocked upon reading your paper to learn that I have a family," the nonagenarian wrote in a letter back to him. "Shows how far behind I have slipped while science marches on."

Stephens later met her in person for lunch to talk shop.

"It's things like that which are more fun than even the supposed discoveries," he said.