NASA continues to study pulsars, 50 years after their chance discovery

August 01, 2017

A little bit of "scruff" in scientific data 50 years ago led to the discovery of pulsars -- rapidly spinning dense stellar corpses that appear to pulse at Earth.

Astronomer Jocelyn Bell made the chance discovery using a vast radio telescope in Cambridge, England. Although it was built to measure the random brightness flickers of a different category of celestial objects called quasars, the 4.5 acre telescope produced unexpected markings on Bell's paper data recorder every 1.33730 seconds. The pen traces representing radio brightness revealed an unusual phenomenon.

"The pulses were so regular, so much like a ticking clock, that Bell and her supervisor Anthony Hewish couldn't believe it was a natural phenomenon," said Zaven Arzoumanian of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Once they found a second, third and fourth they started to think differently."

The unusual stellar objects had been previously predicted but never observed. Today, scientists know of over 2,000 pulsars. These rotating "lighthouse" neutron stars begin their lives as stars between about seven and 20 times the mass of our sun. Some are found to spin hundreds of times per second, faster than the blades of a household blender, and they possess enormously strong magnetic fields.

Technology advances in the past half-century allowed scientists to study these compact stellar objects from space using different wavelengths of light, especially those much more energetic than the radio waves received by the Cambridge telescope. Several current NASA missions continue to study these natural beacons.

The Neutron star Interior Composition Explorer, or NICER, is the first NASA mission dedicated to studying pulsars. In a nod to the anniversary of Bell's discovery, NICER observed the famous first pulsar, known today as PSR B1919+21.

NICER launched to the International Space Station in early June and started science operations last month. Its X-ray observations - the part of the electromagnetic spectrum in which these stars radiate both from their million-degree solid surfaces and from their strong magnetic fields - will reveal how nature's fundamental forces behave within the cores of these objects, an environment that doesn't exist and can't be reproduced anywhere else. "What's inside a pulsar?" is one of many long-standing astrophysics questions about these ultra-dense, fast-spinning, powerfully magnetic objects.

The "stuff" of pulsars is a collection of particles familiar to scientists from over a century of laboratory studies on Earth -- neutrons, protons, electrons, and perhaps even their own constituents, called quarks. However, under such extreme conditions of pressure and density, their behavior and interactions aren't well understood. New, precise measurements, especially of the sizes and masses of pulsars are needed to pin down theories.

"Many nuclear-physics models have been developed to explain how the make-up of neutron stars, based on available data and the constraints they provide," said Goddard's Keith Gendreau, the principal investigator for NICER. "NICER's sensitivity, X-ray energy resolution and time resolution will improve these by more precisely measuring their radii, to an order of magnitude improvement over the state of the art today."

The mission will also pave the way for future space exploration by helping to develop a Global Positioning System-like capability for the galaxy. The embedded Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT, demonstration will use NICER's X-ray observations of pulsar signals to determine NICER's exact position in orbit.

"You can time the pulsations of pulsars distributed in many directions around a spacecraft to figure out where the vehicle is and navigate it anywhere," said Arzoumanian, who is also the NICER science lead. "That's exactly how the GPS system on Earth works, with precise clocks flown on satellites in orbit."

Scientists have tested this method using computer and lab simulations. SEXTANT will demonstrate pulsar-based navigation for the first time in space.

NICER-SEXTANT is the first astrophysics mission dedicated to studying pulsars, 50 years after their discovery. "I think it is going to yield many more scientific discoveries than we can anticipate now," said Gendreau.
-end-
NICER-SEXTANT is a two-in-one mission. NICER is an Astrophysics Mission of Opportunity within NASA's Explorer program, which provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined, and efficient management approaches within the heliophysics and astrophysics science areas. NASA's Space Technology Mission Directorate supports the SEXTANT component of the mission, demonstrating pulsar-based spacecraft navigation.

More about NICER: https://www.nasa.gov/nicer/

Read about five famous pulsars from the past 50 years: https://nasa.tumblr.com/post/163637443034/five-famous-pulsars-from-the-past-50-years

By Clare Skelly
NASA's Goddard Space Flight Center, Greenbelt, Md.

NASA/Goddard Space Flight Center

Related Pulsar Articles from Brightsurf:

Why pulsars shine bright: A half-century-old mystery solved
Pulsars act like stellar lighthouses, shooting beams of radio waves from their magnetic poles.

Astronomers capture a pulsar 'powering up'
A Monash-University-led collaboration has, for the first time, observed the full, 12-day process of material spiralling into a distant neutron star, triggering an X-ray outburst thousands of times brighter than our Sun.

An eclipsing binary millisecond pulsar discovered by FAST
Using the data obtained by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), a research team led by Professor PAN Zhichen and Prof.

Pulsar-white dwarf binary system confirms general relativistic frame-dragging
A century after it was first theorized, researchers have detected the effects of Lense-Thirring precession -- an effect of relativistic frame-dragging -- in the motion of a distant binary star system, a new study reports.

NASA's Fermi Mission links nearby pulsar's gamma-ray 'halo' to antimatter puzzle
NASA's Fermi Gamma-ray Space Telescope has discovered a faint but sprawling glow of high-energy light around a nearby pulsar.

RIT and IAR observe pulsars for the first time from South America
A team from RIT and the Instituto Argentino de Radioastronomía (IAR) upgraded two radio telescopes in Argentina that lay dormant for 15 years in order to study pulsars, rapidly rotating neutron stars with intense magnetic fields that emit notably in radio wavelengths.

NASA's NICER delivers best-ever pulsar measurements, 1st surface map
Astrophysicists are redrawing the textbook image of pulsars (the dense, whirling remains of exploded stars) thanks to NICER, an X-ray telescope aboard the International Space Station.

Astrophysicists link brightening of pulsar wind nebula to pulsar spin-down rate transition
Astrophysicists have discovered that the pulsar wind nebula (PWN) surrounding the famous pulsar B0540-69 brightened gradually after the pulsar experienced a sudden spin-down rate transition (SRT).

Astronomers find 'cannonball pulsar' speeding through space
VLA image shows the trail of a speeding pulsar pointing directly back at the center of the debris shell from the supernova that created it.

NASA's Fermi Satellite clocks 'cannonball' pulsar speeding through space
Astronomers have found a runaway pulsar hurtling through space at nearly 2.5 million miles an hour -- so fast it could travel the distance between Earth and the Moon in just 6 minutes.

Read More: Pulsar News and Pulsar Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.