Pulsars: The Cosmic Communicators
What Are Pulsars?
Pulsars are highly magnetized, rapidly rotating neutron stars that emit beams of electromagnetic radiation from their magnetic poles. These beams can be detected from Earth when they sweep across our line of sight, creating a pulsed appearance similar to a lighthouse beacon. The intervals between these pulses are extremely regular, ranging from milliseconds to seconds, depending on the pulsar's rotation period.
How Do Pulsars Work?
Pulsars form from the remnants of massive stars that have undergone supernova explosions. The core collapses into a neutron star, retaining much of its angular momentum but within a significantly smaller radius, leading to rapid rotation. The misalignment between the neutron star's rotational and magnetic axes causes beams of radiation to emanate from the magnetic poles. As the star rotates, these beams sweep through space, and if aligned correctly, they can be observed from Earth as regular pulses of radiation.
Video Description
This NASA Astrophysics video explains the nature, structure, and behavior of pulsars through stunning animations and scientific explanations.
0:00 - The video begins with the NASA Astrophysics logo and background music.
0:11 - The question appears: "What is a Pulsar?"
0:16 - A rapidly spinning neutron star appears on screen. The narrator explains that a pulsar is a rapidly spinning neutron star, which is the small incredibly dense remnant of a much more massive star.
0:24 - Earth appears with the camera zooming in to New York, illustrating the incredible density of pulsar matter. The narrator states that a teaspoon of matter from a neutron star weighs as much as Mount Everest, and the neutron star is so compact that a ball about fifteen miles across contains more matter than our sun.
0:33 - The animation shows a fast-spinning pulsar with its magnetic fields. The narrator explains that neutron stars spin between seven and forty thousand times a minute and form with incredibly strong magnetic fields. Rapid spin and intense magnetic fields drive powerful beams of electromagnetic radiation including gamma rays. As the pulsar rotates, these beams sweep the sky like a lighthouse.
0:52 - From a distant observer's perspective, we see the pulsar appearing to blink on and off. The animation uses purple colors to illustrate this phenomenon.
0:57 - The video shows a pulsar near a large yellow-colored normal star, connected by streaming gas. The narrator explains that pulsars slow down as they age, but some of the oldest pulsars spin hundreds of times a second. Each of these millisecond pulsars orbits a normal star. Over time, the impact of gas pulled from the normal star has spun the pulsar up to incredible speeds. This accretion may be the cause of their weaker magnetic fields. Despite this, these pulsars also emit gamma rays.
1:22 - The video concludes with closing visuals as the music fades and characteristic pulsar-like beeping sounds are heard.
History of Discovery
The first pulsar was discovered in 1967 by Jocelyn Bell Burnell and Antony Hewish. Initially dubbed "LGM-1" for "Little Green Men", the regularity of the pulses led to speculation about extraterrestrial signals. However, it was soon understood that these signals were natural phenomena, leading to the identification of pulsars as rapidly rotating neutron stars.
| Year | Event |
|---|---|
| 1934 | Astronomers Walter Baade and Fritz Zwicky propose the existence of neutron stars, theorizing that such dense objects could result from supernova explosions. |
| 1967 | On August 6, Jocelyn Bell Burnell, a postgraduate student at the University of Cambridge, detects unusual radio signals using a radio telescope she helped construct. These signals are later identified as originating from a pulsar. |
| 1968 | The discovery of pulsars is officially announced in February. The term "pulsar" is coined to describe these pulsating radio sources. |
| 1968 | The Crab Nebula pulsar is discovered, providing a direct link between supernova remnants and neutron stars. |
| 1974 | Russell Hulse and Joseph Taylor discover the first binary pulsar, PSR B1913+16, leading to indirect evidence for the existence of gravitational waves. |
| 1982 | The first millisecond pulsar, PSR B1937+21, is discovered, rotating approximately 642 times per second. |
| 1992 | The first exoplanets are detected around the pulsar PSR B1257+12, marking the beginning of exoplanet discoveries. |
| 2016 | The Five-hundred-meter Aperture Spherical Telescope (FAST) in China becomes operational, significantly enhancing pulsar detection capabilities. |
More information
Summary
Pulsars are fascinating celestial objects that serve as natural laboratories for extreme physics. Their study has enhanced our understanding of stellar evolution, the behavior of matter under extreme conditions, and the fundamental laws of physics. Continued observations of pulsars provide valuable insights into the universe's most enigmatic phenomena.