The Odd Couple: Ohio State Astronomers' New Pair of Planets Break Rules
Planet-hunting requires infinite patience, a passion for discovery bordering on the obsessive-compulsive, really good math skills, sophisticated telescopes costing millions of dollars—and, of course, an abnormal amount of luck.
In the case of Ohio State astronomy PhD candidate Thomas Beatty, his advisor Astronomy Associate Professor Scott Gaudi, and colleagues at the Vanderbilt Initiative in Data-Intensive Astrophysics, all of the above was true, except for the part about expensive equipment.
Big Discoveries on a small budget—
Using a small telescope, called KELT, in a southern Arizona backyard that has what essentially amounts to a (4-centimeter) glorified digital camera lens hooked up to it, Beatty’s team discovered not one, but two very unusual (as in, downright freaky), planets in far-away solar systems.
KELT is short for “Kilodegree Extremely Little Telescope.” Together, Ohio State and Vanderbilt astronomers operate KELT North and its twin, KELT South which lets them fill in a large gap in available technologies for finding extrasolar planets.
Other telescopes are designed to look at very faint stars in tiny sections of the sky at very high resolution, Beatty explained. The KELTs can look at millions of very bright stars at once, over broad sections of sky, and at low resolution.
KELT’s camera takes photos every night at 13 locations around the sky, perhaps 7,000 images at each site, capturing somewhere in the neighborhood of 100,000-150,000 stars.
Then the computer scans through all of them to see if any show the telltale “dips” in light that indicate a planet has crossed in front of the star. Typically, they might see such dips in 0.01 percent or 1 in 10,000 stars.
“Finding one planet far away is definitely like looking for a needle in a haystack,” Gaudi said. And Gaudi, a seasoned planet-hunter knows. He has several such finds under his belt, but even for experienced star-trackers, exoplanets are elusive.
To realize the patience it requires to engage in planet hunting one must spend a fair amount of time with a planet-hunter.
Every astronomer knows they are out there—beyond our solar system, billions and billions of them, but finding one—there’s the rub. (One is frequently tempted to quote Shakespeare as one ponders the work of astronomers.)
Gaudi and many successful plant-hunters use the technique of transits—astronomers watch for dips of a transiting planet that grow a little dimmer every few days. But it takes a lot of eyes on the sky to catch it. Sifting through thousands of images of hundreds of thousands of stars can be exhausting.
“The process is really an emotional rollercoaster—up and down,” Beatty said. “I was looking for a year after collecting data for over five years—once you have enough data, you start looking in detail. You get your hopes up.”
Inter-planetary Dating: Brown Dwarfs, Hot Jupiters and More
He frequently compares the planet-hunting process with dating analogies.
“There may be 50 -100 things you think look good and you pick out a few that are likely. So it is a lot like Internet dating—they look good, you message each other—and then, sometimes you find there is just nothing there—they’re married; they’re in prison; it’s just bad data.”
Finding your planet in a vast, crowded universe is a bit like finding your true love. But it happens. It really took about a year of looking at the data, but Beatty had been collecting that data for over five years to find his planets.
One planet is located in the constellation Andromeda. Dubbed KELT-1b, it is a massive, super-hot, super dense ball of metallic hydrogen, located so close to its star that it whips through an entire “yearly” orbit in a little over a day.
It is actually more like a brown dwarf—too heavy to be a planet, too small to be a star. “It is weird because they are very rare around stars. Brown-dwarfs are like deserts—you see very few orbiting other stars. In short, in its 29-hour orbit to whip around its parent star, it would cover one-quarter of the sky. It resets the bar for weird,” Gaudi said.
“It is so close it is actually squeezing its star. Very small tides have spun up the star; the companion probably started out much farther away and has now reached a point where the two are locked—they are always facing each other--forever locked in each other’s gaze.
“Eventually, it will run out of hydrogen, expand and eat the brown dwarf,” Gaudi said. Again—very Shakespearean.
When he realized he had a second planet at the end of February, Beatty may have said, “Hot Jupiter,” because that’s exactly what he had found: KELT-2Ab, “right smack in the middle of the constellation Auriga and its parent star is so bright that we can do lots of follow-up, with Hubble, or even powerful ground-based telescopes. We can learn a lot,” Beatty said.
Meanwhile, more and more eyes are on the sky—Gaudi, Beatty and other professional planet-hunters are joined by increasing numbers of collaborators with small telescopes and enthusiastic amateurs looking skyward nightly—all hoping to catch a glimpse of possible new exoplanets waiting in the wings.