Summary
March 6, 2019: A star 440 light years away from other was observed to grow 80% dimmer for about a day. Interestingly, the rate at which it grew dark was quite rapid, but then when it grew bright again it did so much more slowly. This was most likely caused by "occultation", which as cool as that sounds, just means something passed in front of it blocking the light… but what could that something have been?
Possibilities include the following, in rough order of likelihood from "that's probably it" to "speculative fiction":
- A brown dwarf or gas giant planet with an ring system. A Ringed Planet at 40 degree angle might block light at the correct angle and duration to match what was observed.
- A fast-moving but huge cloud of space dust could do it, assuming the main body of the cloud was very dense, and the trailing tail blocked a lower percentage of light than the front wave.
- Protoplanetary Disks or Accretion Disk would also fit the bill, but these generally need something massive at their center to create them. You'd expect gravitational lensing if a black hole were at the center, or a spike in brightness if a neutron star or stellar remnant were in the way. Neither was observed, but if the center were something new, such as an unknown type of dark matter, this is a possibility.
- Some sort of stellar megastructure (such as a dyson swarm, dyson ring, alderson disk, or topopolis) that matched the silhouette or profile of any of the naturally-occurring options of the previous bullet points.
- A massive invasion fleet or space caravan of thousands of spaceships, with a dense main cluster and trailing vessels acting as a rear guard. The discrepancy in speeds or ship density could be explained if they were retreating or fleeing a doomed planet (think Battlestar Galactica), and the faster vessels couldn't afford to wait for the slower ones.
- A single enormous spacecraft with a long narrow tail, such as a generation ship with a huge solar sail on the front.
There's lots of fun options there. We don't know what blocked the light, or how far out it was from the star. So it could be something orbiting the star, or it could be a rogue planet just passing by. The telescope that observed the dimming watched for 160 days, and only experienced one day of dimming. This means that if the obstruction is orbiting the star, it has an orbital period of more than 80 days.
The star, known as EPIC 204376071, is a red dwarf star. It's a little more than half the size of our sun, but only 16% as massive. It's generally much dimmer than our sun, and only a little more than half as hot.
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Game and Story Use
- There's no reason the object has to be in the same system as the star it dimmed. The vast emptiness and distance of space makes it unlikely that something moving through the void would just happen to line up between us and EPIC 204376071. Unlikely, but not impossible. The further the occulting object is from that star, the smaller and slower it could be and still block all that light.
- Perhaps an alien civilization in the system of EPIC 204376071 is at war with Tabby's Star, and we're seeing the departure of their attack fleet or mass driver projectile.
- Perhaps the precursors seeded the universe with life and all these civilizations are reaching stellar megastructure levels of technology within a few centuries of each other. This would imply our own technological singularity is just around the corner.
- One of these stars (this one, or Tabby's Star) dims repeatedly over time, and then one day goes out entirely with no known explanation. A few years later, another star does the same, and this one is closer to the earth, and suggests something massive is headed our direction.
- This could inspire NASA or some other space agency or space force to step up their observation programs and prepare for first contact or a disaster scenario. Would this unite humanity, or be a stress so great it fractures civilization?
- If you like blending fantasy with your science fiction, the darkening of stars could be more metaphysical or magic. Have fun with that "occultation" word. Perhaps an undead dark lord is extending his reach, or an enormous creature is gobbling up planets whole.
- The original article has a fun little animation of the dimness and the possible shape and path across the sun. If you're going to use this event in your game, it's definitely worth running over to the Science Alert website and grabbing that video.