Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.
Many astronomers have seem mysterious events in the night sky. Like many astronomy curiosities out there, it’s these blips in the cosmic picture that can draw new interest and excitement into astronomy. Tabby’s Star, which I cover in a separate article, is one example. Let’s take a look at some stellar observations have the mysteries that have entailed from them…
In September 1984, Bill Katz along with Bruce Waters and Kai Millyard saw at the time many head on meteors in the direction of the Pleiades. In fact, they spotted so many that it couldn’t be by chance so something was generating them. When they went into he archives they found that more had been spotted in the past and over the next 3 months 5 more flashers were seen and revealed to not be meteors but instead energetic particle events. They were 0-3 in magnitude and lasted for less than a second each time (making a definite position reading difficult at best). All that was known was their direction in the Pleiades and Aries. Theory seemed to indicate that it was a new type of burster and a gamma ray source. Other ideas were a SMBH merger or a neutron star collision, something that could generate such an energetic event. But the only event which could be energetic enough and repeat would be a hypernova. The Aries Flasher became known as the OGRE, or the Optical Gamma Ray Emitter as more data was collected. In 1985 follow up observations refined the duration of the flash to about 0.25 seconds and a magnitude of -1, but this time in the direction of Perseus. This trend of a wandering flasher continued as the source never seemed to be in the same spot twice. The total angular spread of all the flashers ended up being 6 degrees, which is way too large a span for a single object, but if something closer like a satellite were emitting the rays then that could be possible. This has seemed to settle the astronomy community, but what satellite was doing it? The answer remains unknown (Seargent 163-7, Katz).
On July 1-2, 1988, Dr. Reinhold Hafner spotted an interesting star in the direction of Ophiuchus that disappears sometimes, only to reappear a few minutes later. This was too soon for any known eclipsing binary! Follow-up observations did show that a companion object 25,000 times fainter than PG 1550+131 around it. The main star was very blue, with just a slight variable output in its brightness. After some work on the theory, science had ah answer. This binary system was a rare type known as a pre-cataclysmic binary. In this subset, one of the stars is a dwarf with the other being a main sequence star of low density that burns primarily hydrogen. The proximity of the two lets the main sequence star get material from its surface sucked up by the dwarf, establishing a nova situation in the buildup. That’s why this is a pre-situation and not a post, for the dwarf hadn’t gone nova yet (Seargent 169-172, Haefner).
A True Mystery
On December 15, 1900 Hertzpring (of HR-Diagram fame) took 2 photographic plates of the sky at 1 hour apart. Years later on April 1, 1927, he reexamines them in his search for variable stars when he spots a bright object. Unable to pinpoint its exact location, he did find that the diameter of the object increased from one plate to another. However, different plates of the same stretch of sky turned up nothing. It was possibly a solar system object if the diameter changed so visibly, likely a result of the travel towards the sun. A comet? Didn’t have any of the features associated with it. An asteroid collision? The uniformness of the object indicated this to be unlikely. The common answer at the time was that it was a variable star of undetermined location. From our modern perspective this is no longer an option because no variable activity has been seen since. Its not a more recent development like a gamma ray source nor a fast radio burst. Maybe is a new type of object, waiting to act up again…or its just plate errors. You decide (Seargent 172-7).
A Rare Event
On October 31, 2006 Akihiko Tago spotted an unusual star in the direction of Cassiopeia which was not of a variable nature. However it did grow in brightness by over 50x its original amount! And on top of that the Central Bureau of Astronomical Telegrams also spotted the star so it wasn’t a mistake. The brightening was fast in its build up and fast in its decline and no unusual changes in the spectrum were seen. Plates from the past indicated no variable action, so what happened? The best theory is a microlensing effect, a consequence of relativity. But for an object the size of a star the total arcing effect is less than 0.001 seconds of arc, very small. The only way one would known it had happened is by the light amplification the star would undergo briefly. Based on cluster distributions, such a microlensing effect happens once every 30 years. If what people saw was indeed such an event, the odds of looking at the right patch of sky and seeing it are astounding (178-180).
The Hubble Flare of 2006
On February 21, 2006 the Hubble Space Telescope was observing in the direction of Bootes when it spotted SCP 06F6 growing in brightness for 100 days, peaking, then fading out over the next 100 days. X-ray emissions steadily decreased during the whole then then petered out at the end. At first people thought it might be a supernova but those are a 70 day event at most. Nor was it a gamma ray burst, a gravitational lensing, or a regular nova for all of those are also fast events. The spectrum wasn’t much help either for the lines were weirdly shifted to something never before seen though it was theorized that they were highly shifted carbon lines, indicating the object was moving away from us at high speed. And as it turns out, once they realized the high speed of the object, they realized that the spectrum lines had been shifted from a familiar scenario: a black hole tearing apart a carbon-rich star. The red shift indicates the event happened about 1.8 billion light-years (Seargent 182-3, Courtland).
In 1961, Antoni Przybylski spotted HD 101065 and noted right away that the spectrum of the object was quite peculiar. It had lots of rare elements that a star normally wouldn't contain, and in 2008 it was determined that the star even has heavy radioactive elements known as actinides. Why is this special? Well, these elements have only been made on Earth in particle accelerators and shouldn't be found in nature due to their quick radioactive decay breaking them down into lighter elements. If these actinides are really there, it implies that something must be replenishing them then, and theories point to an island of stability as a possible candidate. This would be an elemental state of very high mass that would exist for long spans of time (millions of years!) and would be a paradise for atomic physicists. But before we get too excited, it should be mentioned that nothing like this has been spotted before. Is this star all that it seems to be? In 2017, Vladmir Dzuba (University of South Wales) and his team develop a theory where a nearby supernova could have sparked the formation of our star and seeded it with the heavy elements that would be mixed throughout the star. Their decay would therefore be present in their spectral lines, which originate from the atmosphere. But Przybylski’s star is 6,600 degrees Kelvin, which should be too hot to allow a stable place for such a scenario to play out. But, such a hot environment would allow for ions to form and allow free electrons to fly around. This could alter the spectral lines of the star, meaning we are not actually spotting the special decay patterns we think we are. So, what is really going on with Przybylski’s star remains unknown, but intriguing (Clark 54-5).
The Mysterious Supernova
Supernova iPTF14hls was officially uncovered in 2014 but an archival search has revealed that this object may have been a supernova as far back as 1954! This was investigated because over a two-year span it went supernova 5 times, something that should not be possible. Spectroscopy revealed nothing unusual in the spectrum of the (former?) star, instead showing a normal supernova each time until one day when it just stopped. So far, there is no conclusive or accepted answer but theories do exist. The best one is itself a little wild but explains a lot: the star was massive with an interior hot enough to create antimatter. Upon contacting normal matter, explosions ensued and forced shells of gas off the surface without compromising the structural integrity of the star. Eventually, a supernova did occur and the shockwave from it all those shells that had flown off over the years, making a repeating supernova seemingly appear. If this is correct, then the first explosion should have stripped the hydrogen from the star and so that spectral line should be missing from other shells, yet they all matched (56).
Located 550 light-years away, this star has been seen over the years to have inconsistent luminosity outputs, with dimming effect of 10 times fainter lasting up to 2 days being seen. Lots of infrared readings have been seen, indicating dust is present because of its scattering abilities. This would imply that a disc of material is around our star, implying youth. However, other data also matches our star to a red giant in the making which would have no debris around it because of the outflowing radiation. According to the December 21 Astrophysical Journal, it’s neither of these things. Data from XMM-Newton, the Shane 3-meter and the Keck-1 10-meter telescopes instead point to a star which is too old to be young with a disc and too young to be a red giant. Instead, it could be a star that is destroying planets around it (Parks).
Let’s face it: This was a small sample of all the wonders that are out there. Want to know more about a different object? Let me know below, and I will update with new information.
Clark, Stuart. “Cannibals, runaways, and supergiants.” New Scientist. New Scientists Ltd., 21 Dec. 2019. Print. 54-6.
Courtland, Rachel. “Update on Hubble Mystery Object.” Skyandtelescope.com. Sky & Telescope Media, 07 Jun. 2009. Web. 26 Sept. 2018.
Katz, et. al. “Optical Flashes in Perseus.” The Astrophysical Journal. 01 Aug. 1986. Print.
Haefner, R. “The Spectacular Binary System PG 1550+131.” ESO Messenger. Mar. 1989. Print.
Parks, Jake. “Mysterious ‘Winking’ Star Could Be Devouring Planets.” Astronomy, Apr. 2018. Print. 20.
Seargent, David A.J. Weird Astronomy. Springer, New York. 2011. 163-7, 169-183.
© 2019 Leonard Kelley