I'm still perplexed - Tabby's Star Update for November 2017

Update: 29 November 2017

I've been meaning to put out an update for the last several months, and just when I am poised to do so, something else happens. So, here it is is, and I may need another update soon. It' s been an eventful few months, and if you haven't been following closely, you may want to read this.

The tl;dr

Kickstarter-funded observations of the star by the Las Cumbres telescope network began in 2016. There was a Winter interruption when the star was too close to the sun, but observations resumed in the Spring. From about mid-2016 there was a prolonged dimming episode which I am tempted to assume was related to what followed. In May, we saw our first of four dips, during which the overall slow dimming stopped and turned into a slow brightening. After the last dip in mid September, the star brightened for about one month, levelled off in brightness, and lately has been slowly dimming again. There are some new preprints out that contain some interesting tidbits.

Ok, it just got weirder

A huge development tonight in Tabby's Star with publication of Ben Montet's preprint. More soon.

There will be a hangout tonight to talk about it. Message  me if you are interested in coming into the hangout, but we are limited to 10 people total.

Tabby's Star for the Perplexed

Last Update: 5 August 2016

Update: Montet/Simon Preprint
Earlier this year, Brad Schaefer stated that Ben Montet was working on the question of secular fading over the four years of Kepler primary mission data when Tabby's Star was visible, and that he was seeing fading. A preprint came out last night confirming this, and in fact the fading was quite dramatic at times. There are lots of questions, and I suppose there will be controversy, but it's quite important if it holds up. We'll have more soon.


Expecting data soon from the the Kickstarter funded observations by the LCOGT. Stand by...

Related Wow! Signal Podcast Audio Links:
    Tabby's Star for the Perplexed, Part 1
    Tabby's Star for Perplexed, Part 2
    The Slow and Fast Dimming of Tabby's Star
    DASCH Photometry with Josh Grindlay
    Audio Interview with Tabetha Boyajian
    Catching Tabby's Star in the Act - Interview with AAVSO's Stella Kafka


When it comes to Tabby's Star (also known as KIC 8462852), we are all perplexed. This post is for those who are disinclined to read technical papers by professional astronomers, but would like to know just what the heck is going on. What is all this stuff about alien megastructures, swarms of giant comets, infrared excess, and old photographic plates? We'll lay all that out here for you in non-technical terms (or we'll explain the terms as we go). Please, if there are any questions, ask in the comments below, and we'll try and figure out an answer, if there is one. The post is richly hyperlinked, so if you want more detail, you can easily find it. I hope I have given credit wherever it is due.

Let me start by stating up front, that no one knows exactly what is going on with this star. What we'll try to lay out here is why this otherwise ordinary star is strange. If you have questions, or find errors, or know of updates I should include, please leave a comment here.

The Long Delay Echoes

The subject here is a scientific mystery that was well documented by European scientists in the 1920s and 1930s, well before any man made objects were launched into outer space, and then was largely forgotten. The phenomenon has since apparently disappeared, although anecdotal reports still pop up from time to time, and a low level of interest persists. We are discussing it here, because although no one knows for sure what caused the Long Delay Echoes, one plausible explanation is Bracewell Probes. The Long Delay Echoes (LDEs) just possibly might be a clue to how to find such a probe.

Some Basic Background You may Wish to Skip

 I'm sure you know that radio waves generally travel at the speed of light, and can be bounced off of various surfaces and also off the Earth's ionosphere if the radio wavelength is long enough. The speed of radio waves can be a bit slower if they are traveling through a medium such as a plasma or water, but generally the speed is not much less than the 300,000 kilometers per second we are used to. That means, if we send a radio signal out, and see it come back to us, then to calculate the distance to the reflector, we divide the time delay in seconds by 2 (since it went out and back), and then multiply by 300,000 kilometers per second to get the distance. Then, if we send out a radio signal and it comes back 2 seconds later, it must have traveled 300,000 km each way, or most of the way to the Moon. Amateur radio operators often enjoy bouncing their signals off the moon, which generally exhibits a very weak echo delayed about 2 and one half seconds. Strong echoes, or echoes delayed longer than 2.5 seconds, are not moon echoes.

Since the 1960s, there are many radio repeaters in Geosynchronous orbit, but the round trip delay is much shorter than the moon -  less than half a second, and you generally won't see a satellite echo at all unless your signal parameters are just right - and probably illegal.