Just how difficult is it to discover a planet moving around another star? The Kepler space telescope finds planets by observing the brightness of stars over long periods. If a planet passes in front of its star, the light will dim slightly. But it doesn’t dim very much, so it takes some serious data analysis to discover. Read more…
One Universe at a Time
On October 19 of this year the comet C/2013 A1 (more commonly known as Siding Spring) will make a very close approach to Mars. At its closest point, the comet could be only 120,000 km from the surface of Mars. There’s no chance it will hit the planet, but such a near miss could have an effect on both the planet and the probes orbiting it.
The orbits of three of the moons of Jupiter (Io, Europa and Ganymede) have an interesting pattern. For every time Ganymede orbits Jupiter, Europa orbits twice, and Io orbits four times. In other words, the periods of their orbits follow the ratio of 1:2:4. This is known as an orbital resonance, and it occurs a number of times in our solar system. Saturn’s moons of Hyperion and Titan have a 3:4 resonance, and Pluto and Neptune a 2:3.
The magnetic field of the Earth is often portrayed as a large magnet that runs through the center of the Earth, with the magnetic poles located basically at the north and south poles of the Earth, but this is only a rough approximation. Earth’s magnetic field is generated in its core. The core of the Earth has a solid central region surrounded by a fluid outer region. This outer region undergoes convection, and its motion generates the magnetic field through what is known as a dynamo effect.