Ever since Henrietta Leavitt discovered the period-luminosity relation for Cepheid variable stars, and Edwin Hubble used her work to demonstrate the relation between the redshifts of galaxies and their distances, we’ve had a pretty good idea that the universe was expanding. Since then we’ve gathered much more evidence on the connection between redshift and cosmic expansion, including redshift observations of distant supernovae that show the universe is undergoing cosmic inflation due to dark energy. While cosmic expansion is now well established, there have been some interesting mysteries along the way. One of these involves some seemingly strange behavior of quasars.
Kick Me
Pulsars are neutron stars, formed when a large star explodes as a supernova. Because of this, one would expect a pulsar to lie within the surrounding supernova remnant, and to move at the same relative speed. But this is not the case with the Guitar Nebula. It seems that something must have caused the pulsar to move at great speed relative to the remnant. Given it a kick, as it were, hence the term pulsar kick (or neutron star kick). Given the mass of a neutron star (greater than that of our Sun) the only thing that could have provided such a kick would be the supernova itself.
A Supernova’s Tale
A star is driven by two basic forces: gravity and pressure. Gravity tries to squeeze a star as tightly as possible. This causes tremendous heat and pressure in the center of the star, which is great enough to ignite fusion in the star’s core. For most of a typical star’s life hydrogen and helium are fusing in the core, which creates enough pressure to balance the weight of gravity.
When Stars Collide
The traditional view of Type Ia Supernovae is that they are caused by the explosion of a white dwarf after it reaches the Chandrasekhar limit. But new data shows that these supernovae are actually due to the collision of two white dwarfs.