The most famously weird star in our galaxy — KIC 8462852 — is acting up again. On Friday, May 19, the star began to dim again, as it has often done mysteriously over the past century of observations.
Several observatories including the Keck telescopes and amateurs observatories have kicked into action, watching and taking spectra of the star, hoping to take advantage of this extraordinary opportunity to observe in real-time and understand the cause of the non-periodic dimming of the star’s light.
KIC 8462852’s erratic dimming has been famously attributed to a Dyson Sphere - a gigantic sphere of solar panels encircling the star, built by an advanced alien civilization.
The dimming of the light -
New Data from Observations over the Weekend.
New data from May 20 is shown below. The plot shows data from four different observatories/telescopes. The dotted line is the data from Feb 2013, known as Epoch 2, captured by the Kepler space telescope. The new data seems to roughly fit the Epoch 2 event.
David Kipping’s estimate of the transiting object size.
Note that the radius of Tabby’s star is 1.5x that of our Sun. Hence, the transiting object size would be 1.67x the diameter of Tabby’s star.
Data from Las Campanas Observatory at r’ band (Red region of the electromagnetic spectrum) -
Tabetha Boyajian also tweeted — “More dippy in B, lesser so in i'”, i.e., the light is dimmed more in the Blue region but lesser so in the Infra-red region of the spectrum. A solid object blocking the star light would show uniform dimness across the spectrum. Dust particles (or comet trails) would block higher frequencies (such as Blue) preferentially over lower frequencies like Infra-red. So, currently, the bets are on dust (caused by planet collisions or disintegration by the Star) being the primary suspect, not ETI.
Below is a figure from a new paper on another explanation for KIC 8462852 (not based on data from this weekend). Trojans are asteroids that reside in orbits 60o ahead and behind a planet, i.e., the Lagrangian points L4 and L5. The size of the postulated planet is 4.7 Jupiter radii, which is unusually large for a planet. The model predicts a relatively small dip in the current episode, the planet being behind the Star, causing a secondary eclipse.
KIC 8462852
KIC 8462852 (aka Tabby's Star, Boyajian's Star and the WTF Star, after the study's subtitle "Where's The Flux”) is located about 1,280 light-years away in the constellation of Cygnus, along the outer edges of our galaxy.
In 2015, a team of astronomers led by Yale’s Tabetha Boyajian analyzed data collected over the previous 4 years and noticed the light from the star suddenly and repeatedly dip in luminosity. The star dimmed by up to 22% before it returned to normal. Boyajian was part of a citizen science project called Planet Hunters, where volunteers can analyze Kepler data to look for planets, and they alerted her to the unusual star.
Then, in 2016, a review of old photographic plates revealed that KIC 8462852 dimmed by 14% between 1890 and 1989. The star, nicknamed Tabby’s star after Boyajian, faded by another 3% over the four years it was observed by the Kepler space observatory.
The first major dip, on 4 March 2011, reduced the star's brightness by up to 15%, and the other (on 28 February 2013) by up to 22%. In comparison, a planet the size of Jupiter would only obscure a star of this size by 1%, indicating that whatever is blocking light during the star's major dips is not a planet, but rather something covering up to half the width of the star.
What is Causing the Dimming?
Based on KIC 8462852's spectrum and stellar type, its changes in brightness could not be attributed to intrinsic variability.
Several hypotheses have been proposed to explain the star's large irregular changes in brightness, but none to date fully explain all aspects of the observations.
- Swarm of comets. A leading hypothesis, based on a lack of observed infrared light, posits a swarm of cold, dusty comet fragments in a highly eccentric orbit. From arxiv.org/… - “One way we imagine such a barrage of comets could be triggered is by the passage of a field star through the system. And, in fact, there is a small star nearby (∼ 1000 AU) which, if moving near to KIC 8462852, but not bound to it, could trigger a barrage of bodies into the vicinity of the host star. On the other hand, if the companion star is bound, it could be pumping up comet eccentricities through the Kozai mechanism.”
- A planetary disk or debris field. However, infrared observations show a complete lack of an extended protoplanetary disk structure. This is somewhat expected, since the star is estimated to be at least hundreds of millions of years old, and very unlikely to still have a disk associated with star-and-planet formation around it.
- A large number of small objects in "tight formation" orbiting the star.
- Uneven ring of dust orbiting KIC 8462852. Researchers have found less dimming in the infrared light from the star than in its ultraviolet light. Any object larger than dust particles would dim all wavelengths of light equally when passing in front of Tabby's Star.
- Gobbling up of a planet. A team of researchers from Columbia University and the University of California, Berkley, have suggested that the star consumed a planet around 10,000 years ago. This would have resulted in a big outburst of brightness from which the star is now recovering; and the remains of this planet could be transiting in front of the star, thus causing periodic dimming. arxiv.org/...
- Alien megastructure. Intelligent extraterrestrial life constructing a Dyson swarm megastructure surrounding the star.
Alien Megastructures
A Dyson sphere is a hypothetical megastructure of solar collectors surrounding a star, which captures most of its power output, which is then transported to target planets. The concept was first described by Olaf Stapledon in his science fiction novel Star Maker (1937), and later popularized by Freeman Dyson in his 1960 paper "Search for Artificial Stellar Sources of Infrared Radiation”.
A variant of Dyson's original conception — the Dyson swarm - consists of a large number of independent constructs or rings orbiting in a dense formation around the star.
It is estimated that a Dyson sphere in our solar system with a radius of one AU would have a surface area of around 600 million times the surface area of the Earth and be able to capture most of the Sun’s radiant energy, estimated at 4x1026 W.
Alien Megastructures as possible explanation for KIC 8462852
Astronomer Jason Wright and others who have studied KIC 8462852 hypothesized that the objects eclipsing the star could be parts of a megastructure such as a Dyson swarm, made by an alien civilization, high on the Kardashev scale. The suggestion has been that Kepler might have started observing KIC 8462852 while aliens were building a Dyson sphere around it. Hence the gradually declining brightness over the past century, as more of the star was surrounded by the sphere, and intermittent darkening as construction activity went on.
The SETI Institute's initial radio reconnaissance of KIC 8462852, however, found no evidence of technology-related radio signals from the star.
According to Wright, the likelihood of extraterrestrial intelligence being the cause of the dimming is very low; however, the star remains an outstanding SETI target because natural explanations have yet to fully explain the dimming phenomenon.
According to professor Steinn Sigurðsson of the Department of Astronomy and Astrophysics at Pennsylvania State University, the idea that the dimming is caused by an artificial megastructure is a falsifiable hypothesis and is thus scientifically valid. However, it remains an implausible explanation, disfavored by Occam's razor.
How to build a Dyson sphere in five (relatively) easy steps
Here is an article www.sentientdevelopments.com/… and video on how humanity could build a Dyson sphere or swarm. It involves mining and disassembling Mercury and perhaps other planets and asteroids!
Other Sources of Information
TEDTalk — The most mysterious star in the universe — by Tabetha Boyajian -
Related diary by DarkSyde at www.dailykos.com/…
You can follow the latest developments on the Reddit page at www.reddit.com/...
Closing Remarks
From www.theverge.com/…
And it’s really the moment that everyone has been waiting for with Tabby’s Star. It gives astronomers the opportunity to use their entire arsenal of telescopes to observe these fluctuations as they occur. Kepler only observed the light fluctuations in just one broad range of light colors. Now, we can use telescopes to observe the star’s light in numerous colors and light spectrums, and that can give us a better idea of the types of chemicals that are present when these changes occur or the properties of the objects that are blocking the light. For instance, if it is just a bunch of comets, then they’re going to be very close to the star and super hot, according to Jason Wright, and that’s something we can pick up by observing in the infrared spectrum.
References
- The ‘Alien Megastructure’ Star Is Dimming Again — www.theatlantic.com/…
- Why astronomers are scrambling to observe the weirdest star in the galaxy this weekend — www.theverge.com/...
- A Drop in Optical Flux from Boyajian's Star — www.astronomerstelegram.org/…
- Medium Resolution Spectroscopy of Boyajian's Star (KIC 8462852) — www.astronomerstelegram.org/...
- Official page for research related to “the most mysterious star in our Galaxy” — www.wherestheflux.com
- Planet Hunters X. KIC 8462852 – Where’s the flux? — arxiv.org/…
- Families of Plausible Solutions to the Puzzle of Boyajian’s Star — iopscience.iop.org/...
- Secular dimming of KIC 8462852 following its consumption of a planet — arxiv.org/…
- KIC 8462852 wiki — en.wikipedia.org/…
- Dyson sphere wiki — en.wikipedia.org/…
- How to build a Dyson sphere in five (relatively) easy steps — www.sentientdevelopments.com/…
- Reddit page — www.reddit.com/...
P.S.
Update 1 - 5/22/2017 — new section — New Data from Observations over the Weekend — and minor editorial improvements.
Update 2 - 5/23/2017 — added new info to section New Data from Observations over the Weekend.