calibration

As Planck scans the microwave sky, looking out at the early Universe, it also sees things much closer to home.  Now and again, a planet will appear in the path of Planck's beams as it spins around the sky.  The planets move around the sky, and so don't always appear in the same place, and are normally observed only a couple of times a year.  As of November 2009, Planck has seen Mars, Jupiter and Neptune.  Saturn and Uranus will be later this year an

Last week, the Planck satellite observed the Crab Nebula, also known as M1 from Messier's catalogue, and Tau A to radio astronomers. The Crab Nebula is one of the brightest objects in the sky at radio and sub-mm wavelengths, and is used by many astronomers to calibrate their instruments. It is the remnants of a star which underwent a violent and catastrophic explosion at the end of its life, an event known as a supernova.