comets could pass in front of the star at

varying intervals, so their tails, which can

grow millions of km long, would block out

some of the starlight for days or weeks.

However, the theory encounters the same

problem as if the "shadow" had been produced

by dust from planets and asteroids. The water

vapour in the comet tails will be heated by the

starlight, causing heat radiation, and

scientists have not observed any signs of this.

However, the theory has not been totally

forgotten. The shadow could be caused by a

host of free-flying comets located in empty

space between the star and Earth. Such

comets have not yet been spotted , but they

could exist, as comets emit so little light that

they cannot be seen by a telescope, if they

are located outside the Solar System.

OLD PHOTOS, NEW QUESTIONS

The mystery became even more tricky, when

astronomy professor Bradley Schaefer

scrutinised an archive with photographs of

the star dating back to 1890. Much to his

surprise, Schaefer discovered that the light

from Tabby’s Star has become 14 % weaker

over the past 100 years, which ought not be

possible in the case of an ordinary star.

The accuracy of old observations is

always doubtful, and consequently,

astronomer Benjamin Montet from the

California Institute of Technology in the US

analysed the Kepler telescope’s recordings

of the star once again. According to his

analyses, the brightness is still reduced, and

even faster than it used to. During the first

three years of the observation period, the

brightness was reduced by 0.3 % per year.

During the next seven months, the

brightness was reduced at a speed

equivalent to 2.5 % per year. And during the

last five months of the observations, the

light was stable.

So, astronomers not only need to explain

the major, sudden dimmings, but also the

gradual dimming over the past 100 years.

CONSTRUCTION CASTS SHADOWS

A few theories, which can each explain

everything, have already been introduced.

According to some scientists, an unseen planet

orbiting the star could be inhabited by a

sophisticated civilization, which has built huge

solar power plants around Tabby’s star over

centuries. Over time, the scattered clusters of

solar power plants have grown so large that

they block out ever more of the star's light.

The numerous minor/major dimmings are

due to the fact that

what, so the members contacted their

mentor, astronomer Tabetha Boyaijian from

the US Louisiana State University US. At first,

she thought that the dimmings were due to

an error in the analyses of the Kepler data,

but everything was perfect, and in late 2015,

she and the Planet Hunters published the

surprising observations of the star, which

was nicknamed Tabby’s Star.

NO THEORIES FIT COMPLETELY

Astronomers were speechless, as they had

never before seen a Sun-like star behave so

strangely. Scientists throughout the world

immediately set out to investigate it.

Astronomers soon ruled out the most

obvious explanations. The huge dimmings

cannot be due to planets, as even large gas

giants would only dim the light by a few % at

the most. Moreover, planets block out

starlight at regular intervals, when, during

their orbits, they pass between the star and

Earth, but the changes in the brightness of

Tabby’s Star are completely chaotic. The star

might also be surrounded by huge dust

clouds, which originate, when planets or

asteroids collide, destroying each other.

However, this is not likely. When the light

from a star hits dust clouds, they are heated

and emit infrared heat radiation, but several

telescopes have already been unsuccessfully

looking for increased infrared radiation.

Personally, Tabetha Boyajian first thought

that the major and irregular starlight

dimmings could be due to huge comet

clusters. If the clusters were affected by the

gravity of a neighbouring star, groups of

Apart from the network,

the Green Bank telescope

is listening for radio

signals from aliens.

Telescope network monitors star

In the coming year, the KIC 8462852 star will be

constantly monitored by a global network of

coordinated, robotic telescopes.

The observations will be made by the Las Cumbres

Observatory network, which consists of 18 land-based

telescopes throughout the world. One of them is always

"on duty", and if it spots a light dimming, several

telescopes will immediately focus on the star to observe

the process at different wavelengths. This could give us

an indication of what blocks out the star’s light.

TELESCOPES

SIDING SPRING

OBSERVATORY

OBSERVATORYALI

OBSERVATORYTEIDE

INTER-AMERICAN CERRO TOLOLO

OBSERVATORY

OBSERVATORYMCDONALD

HALEAKALA
OBSERVATORY

WISE

OBSERVATORY

SOUTH AFRICAN

ASTRONOMICAL OBSERVATORY

GBT

14

% is the general reduction of

brightness over 100 years.

SPACE STARS