Crab Pulsar
(Flash Warning: repeating gif)
The supernova of 1054 left behind more than one remnant that has been crucial to astronomical studies. The remnant of interest this week is located at the center of the Crab Nebula. It is the not-so-uniquely named Crab Pulsar. Despite shifting our focus away from archeoastronomy, the Crab pulsar and pulsars alike have made an impact on culture but much more recently. I will start by describing what a pulsar is and then detail the Crab Pulsar’s discovery and importance.
Credit: NASA / CXC / SAO / F. D. Seward, W. H. Tucker, R. A. Fesen
The image of the Crab Pulsar above was captured on December 27th, 2008, by the Chandra X-Ray Observatory and spans 9 light-years of the Crab Nebula’s distance (NASA).
What is a Pulsar?
As mentioned in greater detail in my post titled “Crab Nebula”, neutron stars are created because of the core collapse of high mass stars triggered by supernovas. The neutron star left behind is a degenerate ball of neutrons meaning that electron degeneracy pressure* is the only thing holding this ball together against gravity. Neutron stars are hot, dim, and small because during core collapse the supernova highly compresses the core into a smaller surface area. This also explains why neutron stars are so dense and spin so fast. As the mass of the neutron star increases its radius decreases which causes a faster rotation. This relationship is explained by and is a good example of the conservation of angular momentum. This spinning along with the neutron star emitting beams of electromagnetic radiation out of its magnetic poles is known as a pulsar. The large magnetic field surrounding the neutron star acts as a funnel for the particles to flow out from the poles causing the beams of radiation.
A neutron star can come in different forms but the most common are radio pulsars. Check out “9 Breathtaking Types of Neutron Stars…” by Singularity to learn more about them.
As the radio pulsar spins the radiation beams appear to pulse at a known but not always constant frequency like a lighthouse. Its motion is illustrated by the animation below and includes pulses at the bottom to demonstrate the transverse wave* pattern the light makes. The rotation rate varies from pulsar to pulsar but on average a radio pulsar rotates about one time each second. The fastest rotating pulsar is the PSR J1748−2446ad which rotates about 716 times per second (NASA/ADS).
V.I.P. Section
The Crab Pulsar was officially discovered in November of 1968 by Richard V. E. Lovelace with the classification NP 0532. While David H. Staelin and Edward C. Reifenstein III detected two radio pulses months earlier than Lovelace but could not definitively connect them to the Crab Nebula. Staelin and Reifenstein classified these radio pulses as NP 0532 and NP 0527. Soviet astronomer, L. I. Matveenko, also reported a radio source in late 1968 as well. The period in which the pulsar was discovered remains a very crucial era for astronomical advancement. From the mid 1950s to mid 70s the Space Race ensued due to high tensions between the United States and Soviet Union because of the Cold War. The Space Race ultimately led to the creation of NASA. And in response to the Soviet ballistic missile Sputnik, the United States began the Apollo Missions in preparation for human space flight. The Race approached the finish line as the United States landed on the moon after four failed attempts by the Soviet Union to launch a similar mission. A joint mission between the U.S. Apollo and Soviet Soyuz vessels occurred in 1975 in which the commanders of both vessels shook hands, marking the gradual repair in relations (History.com).
Additionally, the expected beams from the poles, the Crab Pulsar’s charge particles form a kind of wind as it interacts with magnetic field which flows from the sides. This is seen in the beautiful image from the Chandra Observatory featured at the beginning of this post. According to NASA, the Crab Pulsar has a similar density to an atomic nucleus (2.4e−14 W/m^2) and is more massive than our Sun.
Thanks for reading! Next week I will introduce the field of linguistic anthropology and conduct a mini linguistic study of words that relate to astronomical events.
Definitions
- electron degeneracy pressure: created because of electrons being forced into higher and higher energy states and moving at faster and faster speeds
- transverse wave: wave with oscillations perpendicular the direction of the waves motion
References
APOD: 2008 December 27 — Crab Pulsar Wind Nebula. (n.d.). https://apod.nasa.gov/apod/ap081227.html
Astronomers Discover Fastest-Spinning Pulsar. (n.d.). NASA/ADS. https://ui.adsabs.harvard.edu/abs/2006nrao.pres. . ..3./abstract
Christiansen, J. (2015, October 13). Pop Culture Pulsar: The Science Behind Joy Division’s Unknown Pleasures Album Cover. Scientific American Blog Network. https://blogs.scientificamerican.com/sa-visual/pop-culture-pulsar-the-science-behind-joy-division-s-unknown-pleasures-album-cover/
History.com Editors. (2022, February 23). The Space Race. HISTORY. https://www.history.com/topics/cold-war/space-race
