Pulsar in Galactic Halo
In 1967 the first pulsar was discovered by graduate student Jocelyn Bell with her thesis advisor Anthony Hewish. The pulsar's regular radio pulse was at first thought to be a signal from extraterrestrials. Today they are theorised to be rapidly rotating neutron stars sending beams into Space like lighthouses. 40 years after discovery, the source of pulsar's enormous energy has remained a mystery. For their work on pulsars Hewish was awarded a Nobel Prize, Bell was not. (Memo: Leave thesis advisor out of research.) This year Jocelyn Bell was named a Dame of the British Empire.
Caltech astrophysicist Fritz Zwicky was known for speaking his mind. He described certain colleagues as "spherical bastards" meaning they appeared as such from any angle! Zwicky's expertise on spherical matters was unquestionable. In the 1930's he used the Virial Theorem on the Coma Cluster of galaxies to deduce a halo of invisible mass. In the 1970's astronomer Vera Rubin used galactic rotation curves to similiarly conclude that most of a galaxy's mass was dark. Nature of the "dark" mass surrounding our galaxy has long been a mystery.
This year one discovery may shed light on both mysteries. Astronomer Robert Rutledge of McGill University and colleagues have reported Discovery of an Isolated Compact Object at High Galactic Latitude. Object J141256.0+792204 is apparently a pulsar located in our Milky Way's dark halo, approximately 5100 parsecs above the galactic disk. This object was discovered by the ROSAT spacecraft with further observations by SWIFT, the Chandra X-ray Observatory and our Gemini North telescope on Mauna Kea.
A pulsar's twin beams propagate along magnetic field lines. Their axis is independent of the neutron star's spin axis, causing them to be dragged around like lighthouse beams. Some pulsars are magnetars, with magnetic fields too powerful for our physics to describe. Twin beams of radiation and a magnetic field are both signs of a Black Hole.
The Black Hole could not have been created by the neutron star, or even by the supernova explosion that created the pulsar. The singularity must have been there billions of years before, when the progenitor star was first created. How stars collapsed from diffuse gas has also been a mystery. Black Holes provide the missing link to understand star formation.
The Big Bang created billions of singularities. These were formed from tiny quantum fluctuations grown large by expansion of the Universe. Size of a primordial Black Hole is limited by a horizon related to the speed of light. Because c was much higher, PBH's formed in a variety of sizes. The largest formed voids, clusters and galaxies. Smaller Black Holes were drawn to the big ones, creating dark haloes around galaxies. Many times these smaller holes have collided with the galaxy's dusty disk, and we are the result.
A Black Hole colliding with a dust cloud will draw matter to it but not suck everything up. The small amount that is eaten will turn into energy and cause the rest to grown extremely hot. Heat of millions of degrees is the ONLY process that can ignite nuclear fusion and the birth of a star. Infant stars, which astronomers call Herbig-Haro objects, exhibit the twin beams of a Black Hole. While most of the Sun's energy comes from nuclear fusion, the Black Hole is quietly contributing to the star's power output. Presence of the Black Hole caused the Sun to collapse in the first place, and allows it to burn steadily for billions of years.
Our theories of the Sun have advanced over time. As late as the 1920’s most astronomers would lecture that our Sun was made of iron, and glowed in the sky like a hot poker. Only a young astronomer named Cecilia Payne suggested that the Sun’s spectral lines could be interpreted as hydrogen. Because Payne was a woman, her idea was roundly dismissed. The equations of nuclear fusion were still being worked out, and most scientists doubted that Black Holes exist.
Black Hole energy and nuclear fusion are two of many processes occuring inside stars. As our knowledge of physics advances, so must theories of the Sun. Physicists have long sought to produce energy via nuclear fusion. Despite decades of work and billions of dollars, they have been unable to produce a sustained reaction. Hint: You need a Black Hole.
Only occasionally will a Black Hole reveal its presence. If a dying star is over Chandrasekhar's limit of 1.4 solar masses, it will eventually collapse catastrophically. Sudden influx of a star's mass into the Black Hole is the ONLY mechanism powerful enough to ignite a supernova. This titanic explosion rips the outer layers away, leaving behind a small dense remnant, a neutron star. If the Black Hole has enough angular momentum, it will produce a magnetic field and twin jets. Because the jet axis is often different from the neutron star's rotation axis, the jets will rotate through Space exactly as observed. A Black Hole is the ONLY mechanism that could produce twin jets and a magnetic field.
A Black Hole is the ONLY object that can make billions of clouds collapse into stars, the ONLY mechanism that can power a supernova, and the ONLY mechanism that can create the jets and magnetic field of a pulsar. Black Holes could be ubiquitous, from the galactic halo to the interior of our Sun. The 95.49% of our Universe that is not baryons could be dominated by Black Holes.
Discovery of a pulsar in the Milky Way's dark halo may also be seen as discovery of a Black Hole. Ruttledge's team notes that this pulsar in the galactic halo could be the tip of an iceberg. For every Black Hole that can be found by its pulsar jets, there could be many more without jets. The galaxy's invisible halo of dark mass could be filled with Black Holes. There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.
This week Advanced Nanotechnology hosts the Carnival Of Space!