Look! Up in the sky! Dark awesomeness.

My most recent post having been about the awesomeness of last week's total solar eclipse, why not post more generally about astronomy/cosmology news? Exciting things are happening in the broader (heh!) field -- as these four recent articles from Cosmos attest.

Pink: most normal/visible mass. Blue: where most mass seems to be.

What we (think we) understand about the distribution of dark matter is inferred from observations of the motions of stars. A small fraction of stars move much faster than expected. So: what's that about? It's hard to know when so few stars are anomalous speed demons. If we had a bigger population to analyze, maybe we'd understand better. And -- leveraging a quite non-astronomical discipline -- perhaps soon we will. See "Artificial brain scans the galaxy for speeding stars: Neural networks come to astronomy as a self-adapting algorithm digs through star maps to find rogue fast-moving stars."

Is it possible that some dark matter -- whatever that is, because we simply don't know -- could take the form of failed stars? (A failed star is a large mass -- massier than Jupiter -- that failed to ignite fusion, and so is hard to see at a distance.) Probably not all dark matter, and yet perhaps a larger fraction than was originally suspected. See "100 billion brown dwarfs may populate our galaxy: New survey dramatically increases estimated number of failed stars throughout the Milky Way."

Dark energy, like dark matter, is a label for our ignorance rather than a known thing. Astrophysicists invoke dark energy to explain otherwise inexplicable observations regarding the inferred rate of expansion of the universe. So it is more than a little intriguing to read, "Can we ditch dark energy by better understanding general relativity? A new understanding of Einstein’s century-old theory may let us do away with the idea of dark energy." The basic idea: a heretofore little-questioned simplifying assumption used to apply the fiendishly challenging math of general relativity (for the mathematically inclined: ten nonlinear partial-differential equations!) may sometimes have led physicists astray.

Gravitational lensing

Emphasis on may and sometimes. Certainly general relativity has had many successes. Consider this very recent -- and very eye-catching -- example: "Supernova déjà vu, all over again: When astronomers saw a star explode they knew – thanks to Einstein – that they could watch it again a year later."