curiouser and curiouser!

Our universe is very curious at the very big scale and the very small. I have already commented on the very small - quantum physics. Now Astronomy magazine reports on two interesting observations at the cosmic scale.

black hole bounced

The General Theory of Relativity predicts that when two black holes merge within a galaxy, gravitational waves rush out of the galaxy at the speed of light. Following Newton's second law, this effectively propels the black hole in the opposite direction, sometimes fast enough to eject it from the galaxy completely.

The magazine reports that a team from the Max Planck Institute for Extraterrestrial Physics has observed a black hole with a mass of several hundred million of our suns moving at a speed of 2650 km/sec (more than 9 million km/hr) and completely leaving the galaxy.

looking way back in time

Images of nine ultradense galaxies, 11 billion years ago. Photo: NASA (Hubble telescope)

The universe is believed to be about 14 billion years old. It has expanded fast since the start of the big bang, and earth is now an enormous distance from "the other side" of the universe. So far, in fact, that it is believed that some parts of the universe are so far away and rushing away from us so fast that light from them can never reach us. We cannot see anything that may be beyond this "event horizon".

Almost as far away are galaxies whose light has taken billions of years to reach us. We effectively see them (only in the Hubble telescope and one or two others!) as they were billions of years ago.

Scientists have recently observed several such galaxies 11 billion light years away, and thus seen as they were very early in the universe's life - after only 3 billion years. Astronomy reports that they found that these galaxies had a similar number of stars to our galaxy but are only a fraction of the size. This was unexpected, and would require them to have expanded rapidly in the time since then to look like the galaxies we are more familiar with.

Truly, the more we learn, the more curious it all gets.