A multi-year study of the Whirlpool galaxy (M51) has changed our understanding of giant molecular clouds, in which stars are born. The new study, which mapped 1,500 such clouds, shows that, instead, they are embedded in a kind of molecular fog, which permeates the whole of the galactic disc. Pressure exerted by this fog is crucial in determining whether or not new stars will form within the clouds. The study, led by Eva Schinnerer from the Max Planck Institute for Astronomy, made extensive use of the millimeter telescopes of IRAM, the Institut de Radioastronomie Millimétrique.
Most of a galaxy’s stars are born within giant molecular clouds - accumulations of hydrogen molecules with total masses between a thousand and several million times that of our Sun. As a region within such a cloud collapses under its own gravity, it contracts until pressure and temperature are high enough for nuclear fusion to set in: a new star is born.
Galactic Rotation and Dark Matter:
Stars near the center of a spiral galaxy orbit at roughly the same velocity as stars near the edge of a galaxy, for the Milky Way this is about 220km per second, or 140 miles per second. And that is weird. very weird.
Normally objects in orbital motion move much slower the further away from the center they get, like the planets around the sun - earths velocity is less than that of Venus. So when astronomers discovered this they knew that it must mean there is mass that cannot be seen, and not centered in the same way as regular matter (not all concentrated at the center of the galaxy.)
This is one of the main pieces of evidence for dark matter.
Models with dark matter spread throughout the galaxy and further confirm this, so now imagine the galaxy as a solid, uniform sphere rather than a bunch of point masses congregating towards the center. Objects orbiting within a uniform sphere only experience the gravitation pull of matter below their orbit, and basically completely ignore everything above them. Its one of those nice mathematically-provable things where everything cancels out. This means that as an object moves further away from the center the net gravitational pull increases exactly proportionally so its speed stays the same.
At first glance a spiral galaxy may look as if the edge stars are slower than the center ones, but in reality if that were true the arms would become so elongated and twisted that it would be hard to tell one spiral arm from its neighbors.
This same effect can be applied to the solar system - Neptune’s orbit is faster than it should be. however the effect does not compare to the effect seen on the galactic scale.
According to the laws of physics, a planet in the shape of a doughnut (toroid) could exist. Physicist Anders Sandberg says that such planets would have very short nights and days, an arid outer equator, twilight polar regions, moons in strange orbits and regions with very different gravity and seasons.
Read more: http://bit.ly/1kPLXGT via io9
petition to turn the earth into a fucking doughnut
We’re on board.