2020 Gumbo Final - Book - Page 37
Tabby’s Star
Story: Gunnar Viator
Photo: LSU Media Relations
Design: Chloe Bryars
T
Tabetha Boyajian is an assistant professor of
astronomy and astrophysics at LSU. She is also the
namesake for Tabby’s Star.
abetha Boyajian is an assistant professor of
astronomy and astrophysics here at LSU. She
is also the namesake for Tabby’s Star, a star
some 1000 lightyears away that has perplexed
astronomers for years.
The star’s fame comes from its seemingly
inexplicable and random cycles of brightening
and dimming. Astronomers have debated about
what might be obstructing its light, and possible
ideas have ranged from planet collections to
mobile alien megaships.
In 2017 Boyajian worked on a science team
in a citizen-science program that involved the
general public contributing observations based
on data and images from NASA; Tabby’s Star
eventually became a focal point. A colleague
from Penn State University eventually referred to
the celestial body as “Tabby’s Star,” and the title
stuck.
According to Boyajian, suspicions of extraterrestrial causes helped propel the story to
stardom.
“Another colleague remarked that we simply
couldn’t figure out what’s happening with the
star and that it made for an interesting target in
the search for extraterrestrial life,” Boyajian said.
“That interpretation is how the star got really
popular.”
These explanations arose because Tabby’s
Star seemingly really does defy conventional
explanations. But as posited by Boyajian in
a paper in 2017, space dust is currently the
predominant theory about Tabby’s Star. Dust
seems consistent with the waning brightness, but
the explanation is not without holes.
“If space dust is orbiting the star and absorbing
its visible light, you expect it to reemit light in the
infrared. That’s not what we see,” Boyajian said.
The absence of infrared emissions is still a
source of some confusion, but the dust-theory
has been reconciled with new data looking
at what parts of the visible light spectrum are
absorbed. Observations show that whatever
is obstructing the light from Tabby’s Star has
differential absorptions consistent with space
dust. That is, visible light, such as red or blue
light, is as a percentage absorbed at rates
comparable to the known absorptions measured
in space dust around other stars.
Another potential problem is the source of this
space dust, according to Boyajian.
“We have to think about the mechanism that
produces the dust,” Boyajian said. “When you
have a star (like Tabby’s Star) burning hydrogen
or helium in their cores, they lack dust. It’s all
been blown away.”
In the latest news, other astronomers have
hypothesized that the dust comes from an
exomoon stripped from its planet by the star.
In theory, the exomoon’s orbit was somehow
perturbed and eventually burnt up by the
star. The resulting debris orbits the star and
eventually melts.
While the star cycles between bright and dim,
its net apparent brightness has been observed
for many years to be arcing towards increasingly
faint. Boyajian said the star is now 20% fainter
than it was 100 years ago. The exomoon theory
sources the obstruction, but it is also apparently
consistent with this gradual dimming.
Boyajian is still actively watching the star. She
noted there was a detection two years ago of
two dimming events that lasted for over eight
months. She and her team hope to determine a
pattern in the star’s fluctuations.
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