Fantasist & Futurist
- Nov 23, 2002
I know it's only been a few days since the last roundup, but there have been too many exciting news stories to ignore:
1. Uranus was struck by planet
Uranus spins at an odd angle compared to the rest of the planets in the solar system, suggesting a major collision in the past. Now a study suggests that Uranus was struck a glancing blow by a planet twice the mass of Earth: 'Cataclysmic' collision shaped Uranus' evolution
The big question is: if another planet hit Uranus, where did that go?The research could also help explain the formation of Uranus' rings and moons, with the simulations suggesting the impact could jettison rock and ice into orbit around the planet. This rock and ice could have then clumped together to form the planet's inner satellites and perhaps altered the rotation of any pre-existing moons already orbiting Uranus.
The simulations show that the impact could have created molten ice and lopsided lumps of rock inside the planet. This could help explain Uranus' tilted and off-centre magnetic field.
2. Asteroid belt had few parents
Studies of the asteroid belt between Jupiter and Mars suggest most of the rocks there may have originated from the destruction of 5 minor planets: Study reveals secret origins of asteroids and meteorites
This follows on from recent studies suggesting that many of the asteroids shared familiar chemical compositions, suggesting shared sources. Perhaps one of them really was Phaeton?at least 85 percent of 200,000 asteroids in the inner asteroid belt—the main source of Earth's meteorites—originate from five or six ancient minor planets. The other 15 percent may also trace their origins to the same group of primordial bodies, said Stanley Dermott, lead author and a theoretical astronomer at the University of Florida.
3. Japanese reach asteroid - samples soon
Meanwhile, the Japanese probe Hayabusa 2 has arrived in orbit around the asteroid Ryugu - with the intention of taking a sample to return with to Earth. Phil Plait provides a further explanation of the strange dynamics of the diamond-shaped asteroid: What would it be like to stand on the surface of Ryugu?
Also worth mentioning is that the BBC reports that Ryugu has a retrograde orbit, which may suggest an extrasolar origin.
4. Ceres' gleaming crater up close
NASA's Dawn spacecraft, now in orbit around the dwarf planet Ceres, has made its closest approaches yet - allowing it to take clearer picture of the mysterious Occator Crater: Dawn's latest orbit reveals dramatic new views of Occator crater
5. Our galaxy just got a lot bigger
A study of metallic elements in stars suggests the Milky Way might be bigger than originally thought: How Long Would It Take to Cross the Milky Way at Light Speed?
That's a heck of a change, and likely to have all kinds of ramifications, not least when accounting for the number of stars and mass within the Milky Way. Perhaps our future merger with Andromeda will be more one-sided than we expected?When looking beyond the previously assumed boundary of the Milky Way's disk, scientists were surprised to see stars with compositions resembling those of disk stars.
The new study estimates the size of the Milky Way's disk at 200,000 light-years across. Past studies have suggested the Milky Way is between 100,000 light-years and 160,000 light-years across.
6. BONUS! Maths story: Drop Pi for Tau
The number pi is famous, but there's a growing movement to demote it for tau, aka 2pi - because 2pi appears in far more formulas than just pi: Why Tau Trumps Pi
At its heart, pi refers to a semicircle, whereas tau refers to the circle in its entirety. Mathematician and poet Mike Keith ... said that thinking in terms of pi is like reaching your destination and saying you're twice halfway there.
Also, don't forget other stories posted to our Science & Nature section, not least: First confirmed image of a newborn planet.