Could be something to do with the Templar's secret adoration of ISIS, the Dog star.
Could also be that dogs make great pets and people like to tweet about their pets.
https://en.m.wikipedia.org/wiki/Dog_days
It appears to pulsate and flash red, blue and white when it sinks into the horizon soon after sundown. I think the effect is magnified when the light has to travel through more of our atmosphere as it sets in the west.
I wonder if its binary neighbor Sirius B contributes to what we see from our perspective.