Thanks to ever better technology, innovative approaches and international cooperation, astronomy is flourishing. But while many observations help to refine or sort out theories, there are always discoveries that just don’t seem to fit. Mysterious signals, alleged violations of the laws of nature and – as yet – phenomena that cannot be explained. The public then likes to discuss whether there are traces of extraterrestrial intelligence, scientists know that in the end there is almost always a natural explanation. But the imagination is stimulated everywhere.

In a series of articles on heise online in the coming weeks we will present some of these astronomical anomalies from a recently presented collection and explain why all attempts to explain them have failed so far.

In astronomy there are always observations that cannot be explained at first. While some suspect extraterrestrials behind it, others expect new insights into the nature of the universe. They are always exciting. heise online takes a look at some of these up to now inexplicable anomalies.

The last part of our X-files is about fixed stars again. A great class of stars are mutable; they change their brightness periodically or irregularly. There are a wide variety of causes for such fluctuations in brightness, such as close double star partners that cover each other, those that periodically expand and contract due to the temperature-dependent transparency of inner layers, and those that are sometimes enveloped in dust, to name just the most important classes. In the past few years, however, several stars have been found whose brightness changes seem inexplicable. A number of explanations have been tried – including the inevitable Dyson spheres, of course – but none of them are really convincing. So what is really behind the “Great Dippers” and “Random Transitern”?

Planet hunt at your desk You don’t need a telescope to make astronomical discoveries. You don’t even have to be a scientist. Anyone can take part, for example in a Zooniverse project. There, researchers make data sets that are too extensive to be viewed by the public for analysis. Because human eyes and human mind recognize more than evaluating computer algorithms. After registering for a selected project and a short training session, it’s time to classify. What kind of object is this or that? What type is this galaxy? Which objects in the picture have moved? Does this star’s light curve have a dent?

1.6 million volunteers have signed up to to sift through the data, which is mostly presented in the form of images or graphs, free of charge and simply for the joy of taking science a little further with your personal effort. With a little luck, you can even achieve a little fame and end up as co-author of a scientific publication. Like Adam Szewczyk, Daryll LaCourse and nine other amateur researchers on a work by lead author Tabetha S. Boyajian from 2015.

The Zooniverse project “Planet Hunters”, launched by Yale professor Debra Ann Fischer, was about the light curves of the Kepler space telescope after the subtle traces of darkening which suggest planets passing in front of a parent star, if we happen to look at the edge of the orbit around the star from Earth (transit method). Kepler had dated 13. May 2009 to 12. May 2013 a field of around 190. 000 Staring at target stars in the constellation Swan and the brightness of all stars every half an hour (sometimes every 5 minutes) with 30 ppm (parts per million) accuracy measured.

That was also necessary , because a planet like the earth with 1 / 90 sun diameter hidden in transit in front of you Star like the sun only 1 / 109 ² = 0.00 0084 = 0, 0084% = 84 ppm of the sun’s surface with a correspondingly small loss of brightness. Most sunspots are significantly larger than Earth, but corresponding spots on stars cause other forms of light curves, for example because a spot on the edge of the star appears compressed in perspective, strongly elliptical and slowly becomes more circular when the rotation turns it towards the center of the star. Planetary silhouettes are always circular and they generally move much faster (within hours) in front of the star than a star spot rolls over the visible star hemisphere (within days or weeks).

The planet Mercury (small dark point half left in front of the solar disk) during its transit in front of the sun on May 9th 2016. A small group of sunspots above the center of the picture. The Kepler Space Telescope searched for such transits of planets in front of the disks of 190. 000 Target stars in the constellation Swan. In contrast to what is seen here, Kepler saw the stars only as points and had to deduce the planet from the minimal darkening caused by the shadowing of a tiny area of ​​the star. In this picture, Mercury covers about 30 ppm of the Sun’s surface. That corresponded to the brightness resolution of Kepler.

(Image: own picture, © Alderamin)

The billions of individual measurements were searched for “dips”, i.e. small dents, by various algorithms. Such dents in the light curve should be symmetrical – a planetary disc causes a mirror-symmetrical change to the entrance when exiting the star disc. They should also be U-shaped: the brightness decreases rapidly as the planet steps in front of the star disk from the first contact with the star’s edge to its full diameter, and then slowly goes down a little more as it moves away from the darkened edge of the Sterns moves closer to the lighter center, before the sequence reverses towards the exit. The algorithms did not even look for major eclipses, they could come from variable stars, but not from planets.

A bizarre dip That was probably why it was a participant in “Planet Hunters”, the amateur astronomer Adam Szewczyk from Toronto, who 2011 an asymmetrical, V-shaped, 0.5 percent deep, four-day light curve profile of the star KIC 8462852 from 21. Mai 2009 was noticed just a week after the start of the mission, which he mentioned on the Planet Hunters talk chatboard ( KIC stands for the “Kepler Input Catalog”, which contains the target stars). The Planet Hunters veteran Daryll LaCourse, who had already evaluated tens of thousands of light curves, found the “dip” (dimple, darkening) in the light curve also very strange and notified Dr. Tabetha Boyajian, who was in communication with the Planet Hunters during her postdoc at Yale. She initially thought the signal was a measurement error, but the Planet Hunters had already subjected the light curve to several plausibility tests available on the website, which they had all passed. The pros couldn’t explain the strange blackout, but they ended up looking for planets, and this didn’t look like one. Therefore, the case was initially filed.

Light curve of the star KIC recorded by the Kepler space telescope 8462852. Above: entire light curve during the Kepler mission from May 2009 to May 2013. The day scale on the x-axis counts from January 1st 2009. Ten blackouts (“dips”) are marked. Bottom left: Enlargement of dip no. 5. An asymmetrical course can be seen, which would not be expected with a cover by a planet. Bottom right: Enlargement of the section by dips 7 to 000. The completely irregular pattern is difficult to explain.

(Image: Boyajian et al., ArXiv)

On the 5th of march 2011, 792 Days after the start of the mission, KIC 8462852 caused a another drop in brightness, this time by a full 16 percent of his Brightness – a planet should have 40 percent of the star’s diameter, to cause such a strong blackout. Actually, this was already the 5th dent in the light curve; more were found in Kepler’s first two years of observation, less deep and completely aperiodic, unlike what would be expected for a circling planet. Dip number 6 followed after 1206 days on 21. April 2012, and on February 5th Dip No. 7 rang a series of four blackouts within 90 days. The last three are extremely irregular, up to 21 percent deep and with intermediate maxima, before the failure of the second of 4 impellers brought the Kepler primary mission to an abrupt end. The space telescope could later be made fit again in a special mode, but had to look for new target fields (with the sun at the back) so that KIC 8462852 could no longer be observed.