If a supernova were to go off somewhere in our galaxy, the minimum safe distance for Earthbound life would be about 50 light years. Any closer than that, and we would experience an intense blast of high energy radiation and an eventual shower of radioactive particles. It would be like nuclear bombs were set off all around the Earth, causing little destruction but a lot of radioactive fallout. Supernovae are incredibly powerful to be able to cause such damage at 50 light years, but even at larger distances, we can see evidence of their effects here on Earth. A team of...
They may look like they are standing still, but galaxies are all spinning. Spiral galaxies have the lovely regular spin of a disk, while elliptical galaxies are all over the place, a buzzing hive of stars. We don’t see this rotation in real time because it takes millions of years for it to be noticeable. The Milky Way takes 250 Million years to spin just once around it’s axis. Looking at this rotation rate vs. distance from the galactic center was what originally led to the discovery of dark matter. Some galaxies do in fact spin slower than others, but how does...
When the Rosetta spacecraft entered orbit around comet 67P/Churyumov-Gerasimenko, first images captured deep circular depressions among the other surface features. Now that the orbiter has taken significant observations of the comet’s surface, the science team has concluded that these depressions are actually sinkholes that form by the same processes that form sinkholes 500 Million kilometers away here on Earth. Sinkholes on Earth form when subsurface material is eroded away. Though not initially visible on the surface, the material falls deep underground leaving a circular cavern. Once enough material has eroded away, the top of the cavern collapses, leaving a large...
A vast number of Galaxies in the Universe have a central black hole that is incredibly massive. The Black Hole at the centre of the Milky Way, dubbed Sag A*, is estimated to have a mass as high as three Million Suns. We generally can’t see black holes, but when they start to pull in matter from surrounding gas and dust clouds, the material forms a disk around the star. This accretion disk can heat up to incredible temperatures and emit X-rays and other high energy light, allowing us to see where the black holes are. Sometimes the light from...
If you guessed that I was referring to the Pleiades, you are correct. The small open star cluster, Messier 45, is about 440 Light Years from Earth, relatively close for a star cluster. We are able to see it with the naked eye in Autumn and Winter here in the Northern Hemisphere. The stars in the Pleiades are young and bright blue, meaning they are very massive and hot. By young, I mean somewhere around a hundred Million Years, about 40 times younger than the Sun. The smears of blue in the above photo show that the cluster is still...
