Eyes on a Mysterious Star

by Steve Beyer on

Hayden Planetarium Blog

Tabby’s Star in the constellation Cygnus
Arrow points to location of Tabby’s Star in the constellation Cygnus.
Credit: Roberto Mura

Back in 2015, we hesitated a bit before posting our blog about a faint 12th magnitude star designated KIC 8462852, 1,400 light years from us in the constellation Cygnus.  More commonly known as Tabby’s star, it’s a curious object, which in the past seven years was seen to be draped by a series of remarkable dimming episodes. Before our previous post, we wanted to be sure nothing in that report suggested an extraterrestrial civilization had been found. However speculation continues about Tabby’s star and interest has grown considerably. It’s time to revisit the story.

A strange phenomenon at KIC 8462852 was discovered by Darryll M. LaCourse, a citizen scientist volunteer with the Planet Hunters team scrutinizing data from the Kepler planet seeking mission. The star jumped out of the vast Kepler data set due to cycles of dramatic and inexplicable dimming noticed by the human eye, but missed by automated computer searches. A report describing the discovery was published in the April 2016 Monthly Notices of the Royal Astronomical Society, authored by astronomer Tabetha S. Boyajian, now with Louisiana State University. She and Benjamin Montet summarize happenings regarding KIC 8462852 in the June 2017 issue of Sky and Telescope magazine.

If a Jupiter-sized exoplanet orbiting a host star the size of the Sun gets directly between us and the star, starlight would be reduced by about one percent. Observations from the Kepler mission revealed Tabby’s star demonstrated ten dips in brightness, ranging from 0.5% up to 20% over a period of about four years. In addition, analysis of astronomical photographs in the archive of Harvard Observatory show a 15% dimming of Tabby’s star between 1890 and 1989. Furthermore, data from Kepler indicate the star had an irregularly paced brightness loss of 3% during the four years of scrutiny beginning in 2009.

A number of explanations for the unique light variations of Tabby’s Star have been proposed, all of which have been questioned. Among suggested scenarios for the strange brightness changes are, an onset of giant starspots, or perhaps a huge swarm of orbiting comets or asteroids, and most recently, the possibility a large cloud of fragments left over after the star fractured, which was then absorbed by a circling planet during the past 10,000 years. Observations show no unusually high amounts of infrared radiation from the direction of Tabby’s star, and to avoid such an IR excess any combination of obscuring “stuff” would have to orbit a good distance from that star, at least as far as main belt asteroids are from the Sun. Another suggestion has been made that passing patches of interstellar dust might cause of the strange diming of Tabby’s star. But no comparable phenomena have been observed elsewhere in the sky.

By far, the most radical suggestion is that Tabby’s star may be providing evidence of a technologically advanced civilization, perhaps improving its quality of life by conserving energy from its native star. Such a plan was described in 1937 by science fiction writer Olaf Stapledon, who in turn inspired Freeman Dyson’s 1960 model. In 1964, Russian astrophysicist Nikolai Kardashev outlined a similar scenario with three levels of technological sophistication. Level II being characterized by a civilization’s ability to harness the entire energy output of its native star, perhaps by constructing a “Dyson Sphere.” This would be a gigantic structure encompassing the star, thereby conserving much of its radiant energy.

As intriguing as it is to ponder the possibility we may have some evidence we’re not alone in the universe, let’s consider several earlier speculations concerning civilizations beyond Earth.

During the autumn of 1892, English observer Alice Everett reported seeing a broad white band obscuring part of the well-known Martian surface feature Syrtis Major. A few weeks later she reported another site on the red planet, Mare Cimmerium, had temporarily become invisible. More reports of transient phenomena on Mars followed as telescopes improved in size and quality, and speculation began about the cause of those features.

During its 1956 opposition, when Mars was about as close as it ever gets to Earth, it was hoped large new telescopes might at last help solve the mystery of Martian canals. If they indeed existed, perhaps something might even be discerned about their origins. Were they natural features or dug by Martians?

At the McDonald Observatory, in Texas, astronomer Gerard P. Kuiper used a binocular eyepiece providing 900x magnification at the 82-inch telescope (stopped down to 28-inches for better sharpness) during a month of observations surrounding Mars’ closest approach on September 10. The instrument provided an apparent diameter of six angular degrees for Mars, an impressive view for that time, equivalent to seeing a quarter at the distance of 10 inches. Several observers, including Percival Lowell, believed they had seen Martian canals, and many believed the canals could well have been the work of intelligent beings on the red planet. On August 23, Kuiper reported “After prolonged examination of the Martian surface with seeing 4+ (nearly perfect images, at 900x magnification), the impression is recorded that the representation of canals so often seen is entirely incredible. The image of the planet was extraordinarily beautiful.”

It was very disappointing to observers that in late August a huge dust storm began to develop and eventually obscured most of the planet. Tongue in cheek speculations that “Martians” had somehow known Earth was watching and generated a vast smokescreen for privacy!

Modern space-based observations confirm that what Ms. Everett and many others had seen were Martian dust storms kicked up when the planet was at points of its orbit less distant to both Earth and wind-inducing warmth from the Sun. A high altitude cloud probably was responsible of an event widely and imaginatively reported in the late 19th century.

On August 2, 1894, the journal Nature noted that three days earlier, telegraph wires around the world were hot with news from the Central Bureau (for astronomical telegrams) about  “A Strange Light On Mars.” The observation was attributed to astronomer M. Javelle at the Nice Observatory where on July 28 of that year he had seen a bright glow at the darkened western zone of the red planet’s gibbous phase. Nature noted: “…so it is to be expected that the old idea that the Martians are signaling to us will be revived.”

H.G. Wells happened to be working as a reviewer for Nature at that time, and the strange Martian light didn’t escape his notice. His subsequent story The War of the Worlds imagined such a light to be muzzle flash from a Martian civilization’s great cannon, launching craft toward Earth with no good intentions. Wells’ tale lived on in versions including Orson Welles’ 1938 radio broadcast (that induced thousands of Manhattanites to head for bridges and tunnels to escape before Martians arrived), a 1953 movie (that kept me awake), and Steven Spielberg’s 2005 production starring Tom Cruise.

Another episode that briefly associated perplexing astronomical observations with space aliens occurred after the 1967 discovery of pulsars by Jocelyn Bell, a student of Antony Hewish at the University of Cambridge. During November of that year she noticed an extraterrestrial radio source producing a series of short, less than 0.3 second, pulses each being separated by about 1.3 seconds. Nothing like it had ever been observed by astronomers and no known source initially explained the pulsations.

Some members of the discovery team, half in jest, referred to the object as “the LGM (Little Green Men) star.” Bell later recalled, “We did not really believe that we had picked up signals from an alien civilization, but obviously the idea crossed our minds, and we had no proof that it was an entirely natural radio emission.” There were suggestions the mysterious rapid flashes might even be navigational beacons guiding an advanced civilization’s star ships. Soon, the notion of pulsars constructed by LGM soon went the way of H. G. Wells’ Martian cannons.

In 1969, Jeremiah Ostriker and James Gunn suggested extremely rapid radio pulses recently discovered from supernova remnants in the constellation Vela and the Crab nebula were magnetically aligned beams emitted by fast rotating neutron stars. Their verifiable explanation linked pulsars to neutron stars and shut down speculation about possible encounters with alien beacons.

Now, let’s get back to Tabby’s star and extraterrestrials. There was a span of about two years between each of the most recently observed episodes of dimming. However, after the last observed event, the Kepler space observatory’s guidance system failed and its further searches of that part of the sky became impossible. The next go round of obscuring may have occurred in 2015, but then no one was watching. It’s now been about four years since the last set of strange events was recorded, and with new found keenness regarding its extraordinary characteristics, many eyes are alert and aimed at this remarkable object.

Amateur astronomers with the American Association of Variable Star Observers regularly point telescopes at Tabby’s star. Another outstanding project has begun thanks to a Kickstarter Campaign with 1,762 backers providing $107,000 worth of funding. Thereby, 24/7 observations of KIC 8462852 are being provided by the Las Cumbres Observatory, a global network of robotic telescopes.

Whatever the outcome of this quest to solve yet another celestial mystery generating sotto voce talk of extraterrestrials, we look forward to new insights directly from KIC 8462852.