YSM Issue 90.1

From space, most stars never twinkle. Some dim periodically, betraying
the clocklike passage of planets. But there is one star that flickers
unlike any other seen before. Known as “Tabby’s Star,” this astronomical
enigma has captured the imaginations of thousands of scientists
and amateurs alike. Its mysterious blinking behavior was first spotted
by amateurs and was subsequently investigated by former Yale postdoctoral
fellow Tabetha Boyajian ’16. Because the behavior of Tabby’s Star
is completely unlike that of similar stars, scientists have resorted to an
array of wild theories as potential explanations—from a massive comet
chain to an alien megastructure. New research suggests that the star is
even more peculiar than previously thought, complicating attempts to
explain its behavior and reinforcing the need for continued study of its
idiosyncrasies.
Tabby’s Star (more formally known as KIC 8462852, and more colloquially
as the “WTF”—Where’s The Flux?— Star) was observed from
2009 to 2013 by NASA’s Kepler Space Observatory. This orbiting telescope
is designed to detect the shadows of exoplanets as they pass in
front of stars. But because of its foreign behavior, Tabby’s Star was not
detected automatically; it took the relatively untrained eyes of citizen
scientists—amateur astronomy enthusiasts who volunteered to pore
through Kepler’s data with their own eyes—to spot the bizarre signal.
“When they first showed the data to me, I just thought it was bad data”,
Boyajian said. “Our automated pipelines missed this feature because it
was unlike anything we had seen before,” she added.
So just what is it about Tabby’s Star that is so perplexing? Most stars
exhibit small, periodic, and symmetrical dips in their brightness, if they
exhibit observable periods of dimness at all. These dips are the result of
the regular passage of an orbiting planet in between the star and the telescope,
a planetary eclipse of sorts. But research by Boyajian demonstrated
that Tabby’s Star exhibits frequent and irregular dips in its brightness
too large to be caused by a planet. New research led by postdoctoral researcher
Benjamin Montet of the University of Chicago revealed another
feature not seen in any nearby or similar stars: a dramatic, long-term
dimming over the four-year course of the Kepler study.
The sum of these observations leads to a troubling but fascinating dilemma:
nothing like Tabby’s Star has been seen before, and no single
theory can make sense of all of the star’s unique characteristics. “There is
no good explanation for what’s going on,” Boyajian said. All explanations
must involve an event far larger than anything of its kind seen before,
or a controversial phenomenon that has been theorized but never observed.
One of the favored explanations presented by Boyajian’s team
consists of a comet swarm around the star that causes its fluctuations
in brightness; however, all comet swarms observed so far are hardly a
tenth of the size that would be necessary to produce such a large signal.
The most well-known explanation for the star’s behavior is an energy
harvesting system built by extraterrestrial life (known as a Dyson sphere
or Dyson swarm). That said, any theory of such elaborate proportions,
particularly one based on phenomena that have yet to be observed, must
be regarded with suspicion.
When Kepler refocused in 2013 on a new mission, it appeared that
researchers would have to rely on only four years of data to solve this
astronomical Rubik’s cube. But once again, astronomy enthusiasts came
to the rescue: a Kickstarter project initiated by Boyajian raised over
$100,000—enough to fund a year of constant observation of the star
through Las Cumbres Observatory Global Telescope Network. With
continuous monitoring of Tabby’s Star at multiple wavelengths, Boyajian’s
team will be able to observe long-term trends. They will also be able
to react in real time to short-term changes in the star’s intensity, which
astronomy
FEATURE
wasn’t possible during the Kepler observations. Sudden changes will set
off a “real-time trigger” that will cue the team to take a burst of higher
resolution images, allowing them to better capture unprecedented rapid
fluctuations in the star’s brightness. Subsequent analyses of these images
have the potential to shed light on the cause of these fluctuations.
While conclusions regarding Tabby’s Star are pending further observation,
one message has already manifested: citizen science is a force
with which to be reckoned. The discovery of Tabby’s Star and its continuing
observation are the result of the massive amount of support that
astronomy enthusiasts can provide; in addition being tracked by the
global network of professional telescopes, Tabby’s Star will be monitored
by the American Association of Variable Star Observers (AAVSO), an
organization comprised primarily of amateurs.
There are, of course, limitations to citizen science in the realm of astronomy.
AAVSO is providing observations of Tabby’s Star to Boyajian’s
team, collected by the home-operated telescopes of astronomy enthusiasts.
Though these observations are useful, they are not as sophisticated
or coordinated as those provided by a professional network. While this
data may prove to be a helpful supplement, AAVSO is unable to provide
a “real-time trigger” in the way that the Las Cumbres Observatory Global
Telescope Network can. The numerous observation stations operated
by AAVSO are not entirely standardized. As a result, observations from
one station are systematically offset from others, precluding the use of
AAVSO to identify short-term fluctuations.
But what citizen science lacks in finesse, it makes up for in both manpower
and willpower. “We were quite surprised by how many people
were interested in supporting this project,” Boyajian said. Unlike many
citizen scientist projects that rely on the human brain’s exceptional
ability to recognize patterns in images— ‘pretty pictures,’” as Boyajian
termed it—signing up for the Kepler project guaranteed hours of staring
at graphs. That didn’t stop over 300,000 citizen scientists from contributing
to the project and from being the first to spot this bizarre star. “Not
a lot of astronomers take advantage of this immense resource,” Boyajian
said. “I can definitely see citizen-science like this growing in the future.”
IMAGE COURTESY OF WIKIMEDIA
►A theoretical diagram of Dyson Rings, an extraterrestrial energy
harvesting device that has been proposed as a possible, albeit farfetched,
explanation for the observations of Tabby’s Star.
www.yalescientific.org
December 2016
Yale Scientific Magazine
33