Why does the ‘most mysterious star in the universe’ act this way?
More than 1,000 light-years away, there is a star that has been baffling astronomers since it was first observed in data collected by the Kepler mission. KIC 8462852 is 50% bigger than our sun, and 1,000 degrees hotter.
It’s now largely known as Tabby’s Star, named for Tabetha Boyajian, a Louisiana State University Department of Physics and Astronomy assistant professor.
Boyajian has been researching and authoring papers about the star since citizen scientists participating in the Planet Hunters project identified its odd behavior to her science team in 2015. A colleague, Penn State Department of Astronomy and Astrophysics Assistant Professor Jason Wright, called it “Tabby’s Star” in an interview, and the name caught on.
The latest research paper from Boyajian, Wright and their research team was published in Astrophysical Journal Letters on Wednesday.
For no obvious reason, Tabby’s Star has been dimming and brightening in strange and unpredictable ways. It has dimmed for a few days or a week at a time. And then there’s the fact that it grew fainter over the past century.
It’s an F star, which is supposed to maintain constant brightness. The long and short fluctuations in light didn’t make sense.
The logical conclusion: Something had to be blocking it. Suggestions from fellow astronomers included a mass of planets, or even an alien megastructure.
The Kepler data revealed that the star dropped in brightness by as much as 22%, Boyajian said. If a mass of planets were involved, there would have to be more than 50 of them, perfectly aligned and “marching” in front of the star to create such a dip.
The data set collected by the Kepler mission, which began in 2009, wasn’t enough to help astronomers debunk all of the theories swirling around the star’s mystery. They needed more observations, in different wavelengths, for a better picture.
A Kickstarter for data
More than 1,700 people donated to a Kickstarter campaign to help the astronomers buy observation time through the Las Cumbres Observatory in California. They raised more than $100,000, which granted the researchers a wide window to observe the star from March 2016 to December 2017.
“All of our supporters were interested in seeing data be collected so they could help us figure out what it was,” Boyajian said. “We made no promises. We’re not going to search for signs of ET. The project was to see what happened next.”
The Las Cumbres Observatory is the only global robotic telescope network in the world to provide continuous observations. As the sun rises where one telescope is located, the observation moves to another telescope. It comprises “21 telescopes at eight sites around the world working together as a single instrument,” according to the observatory.
Data collected by the observatory would also help the astronomers confirm that the data collected by Kepler was “good” and not faulty, and they would mark the first observations made in real time, rather than looking through data that were years old.
Over the past six months, the team observed a “family” of dips, which they named Elsie, Celeste, Skara Brae and Angkor. The first name is a play on the abbreviation for the Las Cumbres Observatory. The second name had personal significance for a member of the team whose mother died during the time the event was observed. And the last two dips were named for ancient lost cities.
So what is the most likely cause of the dips?
‘This is definitely something new and exciting’
Hint: Not an alien megastructure. That theory has been debunked by the latest data set.
“Dust is most likely the reason why the star’s light appears to dim and brighten,” Boyajian said. “The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure.”
Dust is everywhere in the universe, so astronomers are familiar with its signature, Boyajian said. And dust corresponds best with all of the unusual things about the star, like the different periods of dimming.
If anyone feels disappointed that the main culprit is most likely dust, rather than an alien megastructure, Boyajian offers this: “This is definitely something new and exciting. Even if it is dust, what kind of dust does this?”
But this finding only creates more questions. Where is the dust, how was it produced, and why is it existing in front of the star? Could multiple factors have created this phenomenon? Is it something that astronomers haven’t even thought of yet?
There are theories about the origin of the dust, which could be from comets, caused by the star consuming a planet or expelling moons.
Only time, and more continuous observation, will tell, Boyajian said.
The researchers were anticipating an excess of infrared in the dips, but that wasn’t the case. The James Webb Space Telescope, which is expected to launch within the next year, would be able to provide a detailed look in infrared, should Boyajian’s team be granted observation time.
“Is this the only one of these stars out there?” Boyajian asked. “It’s unique to anything we’ve ever observed, but space is still very much unexplored.”