Sunday, November 1, 2015

Alien Megastructure Around Distant Star? Interesting Idea, Says Cambridge Astronomer

Artist's rendering of a hypothetical Dyson sphere around a star. It is a megastructure that completely encompasses a star and captures most or all of its power output. Image Credit: Jay Wong

Recently, a mysterious, distant star, named KIC 8462852 has baffled astronomers around the world. The star, lying approximately 1,500 light years away from Earth is showing unusual light fluctuations, indicating that a cluster of unknown objects is orbiting it. But what are those objects? Scientists are pondering different explanations, including a group of comets or a megastructure built by an advanced alien civilization. In an interview with, astronomer Mark Wyatt of the Institute of Astronomy at the University of Cambridge and one of the co-authors of the paper describing the puzzling discovery, discusses the latest findings. What is so special and unusual about this star's light fluctuations?

Mark Wyatt: The star's light-curve is unusual in exhibiting periods lasting several days during which it gets fainter by up to 20 percent. These dips in brightness occur irregularly and are interspersed by long periods when the star looks otherwise normal. Have you seen anything like it or similar when observing other stars?

Wyatt: This was the only star in the Kepler dataset of more than 150,000 stars to show this behavior. Some very young stars are known to show aperiodic brightness variations, but the dips have a different character [e.g., they occur much more frequently] and are thought to be related to the protoplanetary disk known to surround these stars. Do you think KIC 8462852 has exoplanets orbiting it?

Wyatt: Given what we know about other main sequence stars of its spectral type, it would not be too surprising if the KIC 8462852 system did contain exoplanets. However, that comment applies to all stars, and for now we can only speculate about what exoplanets exist in this system.

UK Infrared telescope (UKIRT) image of KIC 8462852 and another bright star for comparison. Image Credit: Tabetha Boyajian et al.
UK Infrared telescope (UKIRT) image of KIC 8462852 and another bright star for comparison. Image Credit: Tabetha Boyajian et al. It is considered that this star is surrounded by some alien megastructure, a so-called Dyson sphere, what do you think about this possibility?

Wyatt: It's an interesting idea. We did not explicitly consider the possibility of a Dyson sphere in our paper. However, we did consider several “scenario-independent constraints” that material causing the dips has to abide by. For example, the duration and shape of the dips as well as their lack of repetition during the Kepler lifetime, imply the material orbits at several Astronomical Units from the star - if the orbits are circular - and is made up of clumps that are comparable in size to the sun. We also pointed out that the scenarios are constrained by the non-detection of infrared emission from the material causing the dips, since it is inevitable that the material will absorb the stellar radiation and re-emit that in the infrared. This is problematic for scenarios in which the material has a spherical distribution, since this implies that the material we saw to pass in front of the star is just a small fraction of that present. Could a group of comets or disintegrated planet be an explanation of these irregular light fluctuations?

Wyatt: Our preferred explanation in the paper was that the dips are caused by a group of comets orbiting the star. The constraints on the orbits mentioned above are not so stringent if the orbits are highly eccentric, like those of comets in the solar system. If the material shares a common orbit then this also explains the non-detection of infrared emission - the observed dips do not require large quantities of unseen material, we just happen to be at a location where that orbit passes in front of KIC 8462852, which is reasonable given the rarity of objects that show a similar phenomenon. Do you plan further observations of this star?

Wyatt: We will for sure be performing follow-up observations of this star to help figure out what is going on.


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