Friday, August 26, 2011

A pulsar planet with a diamond core?

PSR J1719−1438 is a pulsar, which is a rapidly spinning neutron star. Such an object is called a pulsar because its powerful magnetic field shoot jets of energetic particles out along its magnetic poles. This also makes the spinning neutron star appear to pulse as its jet sweeps past an astronomer on Earth.

Slight variations in the timing of the neutron star's pulses can indicate the presence of an unseen planet that is also orbiting the pulsar. Indeed, the first known extra-solar planet was discovered via pulsar timing variations. Matthew Bailes (Swinbourne University in Australia) discovered the timing variations in pulsar PSR J1719−1438, and they are due to a Jupiter-mass planet in a very close two-hour orbit about the neutron star. He and his colleagues also show that this planet must be very small and dense to avoid having been ripped apart by the neutron star's gravitational tide. This planet's minimum density is about 20 times that of Jupiter's, and the planet's core is likely made of carbon. If so, then carbon at the center of this very dense planet will have crystallized, possibly into one giant planetary core-sized diamond. See this press release for more details.

Saturday, August 13, 2011

Streaks at Martian crater suggest a watery flow

This is the upper edge of the Newton crater on Mars, imaged my the Mars Reconnaissance Orbiter (MRO). The dark streaks extending downslope are very interesting; they are only seen in spring and summer, and fade away during the colder seasons. These streaks might be due to a flow of subsurface water that is likely a salty brine due to long-term contact with the martian rocks. Salt lowers the freezing point, which might allow subsurface ice to melt and seep down the crater's slope. This might be the cause for the seasonal stains that are seen in the crater's soil. Additional details can be found at the MRO website, including this nice movie of streaks forming and then fading. If these streaks are in fact watery seeps, they will be of great biological interest because wet soil will be a natural place to look for microbial life on Mars.

Monday, August 1, 2011

Vesta is groovy

The giant asteroid Vesta, as seen by the Dawn spacecraft, which has been orbiting Vesta since July 15. See the Dawn website for more information. This movie of Vesta's rotation is also interesting...evidently, Vesta is quite `groovy'.