Reshared post from +annarita ruberto
Pulsars, a kind of cosmic lighthouses
The Pulsars (Pulsating Radio Sources) are rapidly rotating neutron stars with a very high magnetic field, which emit a collimated beam of radio waves.
The radio emission, coming from the magnetic poles of the star, is confined within a small cone of emission and, if the magnetic axis is not aligned with the rotational one, the neutron star acts as a sort of cosmic lighthouse and an observer on Earth will see a sequence of pulses of radio waves.
Let's see how a pulsar comes into being.
When a massive star, exhausted its nuclear fuel, ends its life, it happens a supernova explosion and it remains a compact remnant . This object, named Neutron Star, has a radius of about 10 km and a mass equal about to 1.5 that one of the sun (whose radius is 700,000 miles). A Neutron Star is thus the "ash" that remains when a massive star collapses on itself and burns. The gravity force prevails on the electronic force that holds the atoms separated from each other and compresses them into a mass ten trillion times denser than a lead block. A single teaspoon of neutron star material weighs as much as an entire mountain!
Because of the angular momentum conservation (the principle according to which, for example, a skater rotates on himself faster when approaching the arms to the body) the collapsed star, having drastically decreased its radius, is born with an extremely high rotational period .
The discovery of pulsars is curiously tied to women!
The first radio pulsar, named PSR B1919 +21, was in fact discovered in 1967 by British astrophysicist S. Jocelyn Bell Burnell, when she was still a PhD student at the University of Cambridge, along with her thesis supervisor Anthony Hewish, during of an experiment on the scintillation produced by the interplanetary medium of extragalactic radio sources. Thanks to this discovery, Anthony Hewish earned the Nobel Prize for physics, in 1974.
In 2005, the young Italian astrophysicist Marta Burgay, currently a researcher at the Astronomical Observatory of Cagliari (http://www.oa-cagliari.inaf.it/index.php?set_language=1), discovered, along with team colleagues Andrea Possenti and Nichi D'Amico, the existence of PSR J0737-3039, the first double pulsar (two pulsars orbiting each other), through using the 64-meter Parkes radio telescope in Australia.
Marta Burgay is part of the international group PulSE (Pulsar Science in Europe), awarded with the Descartes Prize 2005 " Excellence in collaborative scientific research."
Watch the video:
Joanna Rankin on Pulsars
Further reading for deepening:
Source gif: http://intothecontinuum.tumblr.com/