Crab is emitting super-energetic gamma rays
Here’s another chapter for the books of “Persistence Pays Off” and “Who Woulda Thought?” A team of astronomers has discovered very energetic gamma-ray pulses emanating from the core of the Crab Nebula, in defiance of current theory. The nebula, a remnant of a 1,000 year-old supernova, is a semi-chaotic mass of gas surrounding a type of neutron star called a pulsar, the source of the gamma rays. Like all neutron stars, a pulsar is the tiny, extremely dense, collapsed core of a progenitor star; what makes these objects special is that the axis of rotation is offset from the bright magnetic poles, so that every time they spin they are observed to emit a pulse, like a lighthouse. Given its relative young age and close proximity to Earth — a mere 6,500 light-years — the Crab pulsar has been well-studied by astronomers. Theorists thought it was not possible for a pulsar to emit such energetic gamma-ray pulses, leading some of their colleagues to tell members of the team they were “crazy” for even trying to observe them. But the astronomers’ persistence paid off, and the new discovery is already changing how theorists think about these objects.
“We thought we understood the gamma-ray emission, and this was really becoming a foundational feature of our models, but that’s now thrown out,” [one of the authors of the study, Andrew] McCann explained. “The reason why this is so exciting is that it’s turning things around in the field.”
You gotta love how astronomers and physicists get excited every time a new discovery shoots down current theory. That’s exactly the kind of attitude that moves science forward.
Uranus pummeled by other planets?
The distant gaseous planet has long been a puzzle to astronomers, who have been trying to explain its peculiar axis tilt ever since it was discovered.
Most of the planets in the solar system exhibit axis tilt — this is where the axis of a planet’s rotation is at an angle to an imaginary line that runs perpendicular to the planet’s orbital plane. Mercury is alone in that it has virtually zero axis tilt, though Jupiter’s is also diminutive at just 3 degrees. The Earth’s axis tilt is 23.5 degrees, and Venus is nearly upside down with its rotation axis pointing almost completely downward (this is also somewhat of a mystery to astronomers).
Uranus is the strangest of all, as it rotates flopped over on its side. Some astronomers have hypothesized that Uranus was pummeled by another planet in the early history of the solar system, and this collision resulted in Uranus’ 98-degree axis tilt. However, another collision might be required to explain the spin of Uranus’ moons, which should otherwise spin backwards. A new simulation created by astronomers indicates that collisions with two Earth-sized planets could explain Uranus’ observed configuration. The main problem with this idea, however, is to explain where the two Earth-sized planets came from.
Evidence for water on Mars?
Astronomers have discovered seasonal dark streaks on the surface of Mars that could be signs of melted water running across the surface. Meanwhile, NASA’s Curiosity rover is slated to visit Mars next year to look for signs of water in the Gale crater. The discovery of liquid water on Mars will greatly facilitate any plans to establish future colonies there.