Astronomers Spot Distant Star Dimming So Unpredictably, They Can’t Explain It

Astronomers have so far spotted as many as 28 dips in the star's brightness, all pf them totally random. E.T. is that you?

There’s a distant star in the universe that’s so strange, experts don’t know what to think of it, and there’s a chance it may be home to an alien megastructure.

A binary star located 350 light-years away, in the constellation of Libra, dims in an unpredictable way and has baffled astronomers who have not managed to figure out what’s going on with the distant star.

Binary star systems are those that contain two stars.

In this case, the researchers – led by S. Rappaport, of the Kavli Institute of Astrophysics and Space Research – have discovered one thanks to the data gathered by the extended K2 mission of the Kepler telescope.

The Star’s name: EPIC 249706694 (HD 139139).

Its brightness dips strangely

Astronomers have so far spotted as many as 28 dips in the star’s brightness. That on itself is not strange, but there’s an issue.

The dips in brightness are totally random and inconsistent.

Led by MIT’s Kavli Institute for Astrophysics and Space Research, astronomers have gone through a plethora of possible scenarios, but have come out empty-handed without being able to explain what’s going on.

The Kepler space telescope states at a part of the sky and records the brightness levels of distant stars. If the star’s brightness dips, it may be an indication that there’s something–like an exoplanet–passing in front of it, causing the brightness of the star to dip briefly.

An artists rendering of an alien Dyson sphere around a distant star. Shutterstock.
An artists rendering of an alien Dyson sphere around a distant star. Shutterstock.

But one dip isn’t enough.

Scientists need more. They need something called periodicity, which is basically several dips of the same brightness, happening at equal intervals.

If these criteria are met, it could suggest there’s a possible exoplanet traveling around the star.

Spotting weirdly dimming stars isn’t new.

We’ve spotted them before, and one perfect example is KIC 8462852, also known as Tabby Star. It does not have a regular brightness, nor an observed periodicity, but nonetheless, the data astronomers have gathered so far gives us a lot of room for explanations, like come swarms of gigantic dust clouds.

Understanding the phenomenon

Astronomers have revealed that although EPIC 249706694’s light curve has shown radical, unexpected dips in brightness, it does fit other observations of transits, even though the surprising depth of dimming remains an enigma.

But the universe is massive, and we don’t really understand everything. And three’s nothing in the universe we know of that can account for a star with dips with the same light curve while lacking periodicity.

This means that whatever is orbiting around EPIC 249706694, is unlike anything we’ve ever seen before.

During Kepler’s 15th observational campaign (23 August – 20 November 2017), it gathered 87 days of data observing the distant star.

During that time, it spotted as many as 28 dips in brightness, only two of which had the same depth, in other words, the amount by which the star eventually dipped.

And that’s unusual, reveal astronomers.

“The unusual aspect of these dips … is that they exhibit no periodicity, and their arrival times could just as well have been produced by a random number generator,” the researchers wrote in their paper.

“We show that no more than four of the events can be part of a periodic sequence.”

What’s orbiting the stars?

So, what could possibly orbit the binary system then? According to calculations, the researchers have revealed that the size of the object that would cause this specific dimming would need to be as much as twice the size of Earth for one star, and a Jupiter-sized world fo the other star.

But the lack of periodicity has ruled that out.

Dust-emitting asteroids might be another theory, but these would only produce random brightness dips.

Another bet is planets orbiting the binary system. The celestial bodies could reduce periodicity because everything is in motion, and the stars also move, so not every planetary body would produce a transit, potentially resulting in random dips.

However, the scientists could not replicate a single simulation that yielded more than five observed dips.

It also remains an enigma as to which of the two stars produces the dimming events.

Since the star is very old, it is not likely that the observed dips in brightness are the results of fragments from an accretion disc. The star is around 1.5 billion years old.

Furthermore, the observations revealed that the light curves are much more similar to planets than to clumps of debris.

“All transit scenarios that we have been able to conjure up appear to fail,” the researchers explained.

So far, we’ve discovered 12 oddly-dimming stars in the universe.

Monthly Notices of the Royal Astronomical SocietyScience Alert
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