Medescape

Skepticism, Medicine and Science News

Remember To Set Your Clocks!

This coming New Years Eve everybody needs to remember to change the time of their clock….by one whole second. It sounds daft, but this happens every three years because the earth gets too out of sync. When the clock strikes 00:59:59 on New Years Eve,  make sure to pause time for about one second, and then let it strike 01:00:00. The insertion of this leap second was prescribed by the International Earth Rotation Service in Paris due to the fact that the earth tends to lag behind the extremely precise atomic clocks. So, happy leap second-year!

December 10, 2008 Posted by | General Science | , , , , , , , , , | Leave a comment

Chandra X and the Crab Nebula

In 1999 NASA launched the Chandra X-Ray Observatory, which is part of NASA’s Great Observatories together with HubbleSpitzer, and Compton. Chandra X recently took a beautiful picture of the Crab Nebula

According to NASA, this is the first picture clearly showing the faint boundary of the nebula‘s X-ray emitting pulsar wind nebula. The white dot in the center is the neutron star (or pulsar) powering the nebula. Pulsars are essentially highly magnetized neutron stars that emit concentrated beams of electromagnetic radiation, which can only be observed when directed directly at earth. A pulsar will thus appear to pulsate (hence the name) when observed, and the regularity of this pulsing effect has been shown to be extremely precise, even to the level of an atomic clock. Anyhow, the rapid rotation of the pulsar in question combined with the intense electromagnetic field generated creates jets of matter and antimatter shooting out from the poles of the pulsar, and a strong wind flowing out in the equatorial direction. The inner ring surrounding the pulsar is possibly a shock wave serving as a boundary between the nebula and the matter/antimatter jets, and electrons and positrons flow outward from it, producing an extended X-ray glow. The shape of the nebula is related to the strong magnetic field, and the dark spots on the right and left is thought to be the result of a toroidal (doughnut) shaped magnetic field from a progenitor star.

November 7, 2008 Posted by | Astronomy | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , | Leave a comment