If there was a nightmare I could tell you about the night sky, Eta Carinae would be a good candidate. Easily the brightest "far away" star in the sky (sorry Northern Hemisphere) this star defines scary. First, it is not one star but two. The small star is roughly 80 times as massive as the sun... the bigger star is over 100. Each of these giants, if placed in the center of our solar system, would be larger than the orbit of the earth, maybe Mars. These two giants orbit each other in less than a five and a half years, but that does not explain what is scary about them. They orbit a common center called a barycenter, much like Pluto and Charon do. But they are about as far apart as the Sun and Uranus; Uranus takes 84 years to orbit so imagine to massive stars whipping around each other in that big of a circle only 15x faster.

In 1843, something went bad. Eta Carinae became the second brightest star in the sky and then went unstable, at times one of the 5 brightest stars in the night sky and then fading to be barely visible to the naked eye. BUT! and here is the blow your mind fact. We are now starting to record the evidence of that explosion... TODAY. You see, there is a massive nebula behind Eta Carinae, roughly 140 light years behind it. We are now starting to see this reflection nebula grow brighter... This is the light from 1843 that went off in all directions, some went to us, some hit that nebula and then bounced back our way, only 280ish years later.

Astronomers are literally looking at light from a major event that bounced off a wall of gas and headed back towards earth.