Pulsars and the Gravitational Constant

One Pulsar May Confirm the Gravitational Constant is Universal:

Imagine a world where gravity was different than it is here on Earth. Perhaps objects stay in place, rather than fall to the ground. This would have changed a man’s life.

Sir Isaac Newton’s study of gravity may never have come to be if that apple had stayed in its place and didn’t fall and hit him on the head.

Despite the widespread adornment towards Sir Isaac Newton, there are some who refuse to drink the Kool-aid.

Who Are These Haters?

Astronomers, Physicists and Scientists alike have challenged Sir Isaac Newton’s law of universal gravitation and that the gravitational constant is… well, constant throughout the Universe.

Let’s see if these haters are right or another bunch of newbs Sir Isaac Newton hypothetically will backhand and put in their respective places.

What is This Law of Gravitational Constant?

Nature has four fundamental forces: gravity, electromagnetism, strong nuclear and weak nuclear. Without these fundamental forces, we wouldn’t exist.

Imagine how the world would be without gravity, the Earth would just keep going. It’d be orbiting the Sun and then all of a sudden it’d just keep floating in a single direction and not be drawn back to orbit from the gravitational pull of the Sun.



“GPB circling earth” by NASA – http://goo.gl/zT7o7o. Licensed under Public Domain via Commons – https://goo.gl/rKDiOU


Sir Isaac Newton, an English mathematician, studied the fundamental forces and made huge strides in the research and knowledge of gravity.

During his studies and experiments, Sir Isaac developed an equation to help solve the questions surrounding gravity.

What is the Gravitational Constant Equation?

It’s Big G, of course.

The value of Big G, or the Gravitational Constant is:

  • 6.674×10−11 N⋅m2/kg2

Where N denotes a Newton Unit, m is the Mass.

Newton’s law shows how the product of the masses of two objects is proportionate to the gravitational force between them. Additionally, between the center of two objects, the square of the distance is inversely proportional.

F = G\frac{m_1 m_2}{r^2}\

Where F is the Attractive Force, G is the Gravitational Constant, m is the mass (object 1 and 2) and r represents the Inverse Square law.

However, some Astronomers believe that this value is gradually decreasing as time progresses along with the expansion of the universe, as suggested by the Big Bang Theory.

Despite suggestions and theories by different Astronomers, the accepted belief, is that the force of gravity remains the same everywhere and anywhere, at any given time.

What do Pulsars Have to do With All of This?

To start, Pulsars are actually really cool. They’re rotating neutron stars and emit beams of electromagnetic radiation. Astronomers use super powerful telescopes and other tools of measurement to both detect and time these Pulsars.

What is a Pulsar:

A Pulsar is a celestial object, thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves and other electromagnetic radiation at rates of up to one thousand pulses per second.



“Pulsar schematic” by User:Mysid, User:Jm smits – Made by Mysid in Inkscape, based on en:Image:Pulsar schematic.jpg by Roy Smits.. Licensed under CC BY-SA 3.0 via Commons – https://goo.gl/uDzd5y


What is a Neutron Star?

A Neutron star is a celestial object of very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons. Neutron stars are thought to form by the gravitational collapse of the remnant of a massive star after a supernova explosion, provided that the star is insufficiently massive to produce a black hole.



“Neutron star cross section” by Robert Schulze – Own work. Licensed under CC BY-SA 3.0 via Commons – https://goo.gl/tFpPAZ


Common Characteristics of Pulsars:

  • Small, usually 12 to 15 miles across
  • Pulsars rapidly spin
  • Dense remains of bigger stars, usually Neutron stars
  • Pulsars have magnetic poles which emanate as they travel through space rotating
  • Pulsars are extremely consistent in maintaining their rate of rotation
  • Cosmic laboratories study Pulsars to determine the fundamental nature of gravity, time, and space

Enter Pulsar PSR J1713+0747:

For the last 21 years, Astronomers have been studying the precise measurements of the rotating pulsations from PSR J1713+0747.

Using special telescopes and measurement devices, the Astronomers have attempted to capture the rapid spinning and exact beat from this Pulsar.

How Far Away is PSR J1713+0747?

Pulsar PSR J1713+0747 is nearly 3,750 light-years from Earth, that’s 22,044,845,149,438,528 miles away!

Is PSR J1713+0747 All Alone or Does it Have Friends?

It has a friend and companion, it orbits around a white dwarf star and after more research PSR J1713+0747 was determined to be one of the brightest and most stable pulsars known.

How Close is PSR J1713+0747 and its White Dwarf?

PSR J1713+0747 takes roughly 68 days to orbit around its white dwarf companion, which is actually a pretty large orbit for the typical pulsar and companion star.

This larger than usual distance was essential in the measurement of PSR J1713+0747 and using this orbit and pulsation to help the study of the two objects’ gravity.

What’s of special importance to Astronomers is the effect of the gravitational radiation with these two objects. Gravitational radiation is the conversion of orbital velocity to gravitational waves, usually extremely consistent.

We know about this because of a famous Scientist you might have heard of… Albert Einstein.

So What Did Astronomers Find?

As PSR J1713+0747 underwent its study for 21 years, astronomers used the Green Bank Telescope of the National Science Foundation in West Virginia.



“Green Bank 100m diameter Radio Telescope” by Image courtesy of NRAO/AUI. Licensed under CC BY 3.0 via Commons – https://goo.gl/wO0Ykd


They also used Puerto Rico’s Arecibo Observatory, as you probably remember from Carl Sagan’s famous movie: Contact.



“Arecibo Observatory Aerial View” by H. Schweiker/WIYN and NOAO/AURA/NSF.(The original uploader was Quazgaa at English Wikipedia.Later version(s) were uploaded by Jakuzem at en.wikipedia.) – Transferred from en.wikipedia to Commons by Giro720 using CommonsHelper.Original source : NSF – Download Images. Licensed under Public Domain via Commons – https://goo.gl/8amIU5


The research Astronomer’s were able to produce would become some of the best data ever collected on the measurement of the gravitational constant outside of our Solar System.

What Were Astronomer’s Findings?

Astronomers found that the orbit between PSR J1713+0747 and its white dwarf companion star, the rate and consistency of the Pulsar’s rotation and the dependability of the stellar remnant; lead Astronomers to deduce that the fundamental force of gravity is constant throughout the Universe.

So Were the Haters Right or Wrong?

Sit down haters, Sir Isaac Newton was right and your 15 seconds of fame is over.

What made this information so valuable is that we were able to prove Sir Isaac Newton was right and that 3,750 light years from Earth, the same laws of gravity hold true.

This study aimed to determine whether the gravitational constant of Newton’s Law of Gravity is truly universal or if it only holds true in and around our Solar System.

This test was able to measure the gravitational constant at a significant distance from our Solar System, using different gravitational conditions, places, and times.

The data Astronomers collected proves gravity is the same in a distant pulsar and star system as it is in our own Solar System.

These results helped them to prove the haters wrong and eliminate other theories that gravity changes as time progresses and in different parts of the Universe.

Sir Isaac Newton can remain confident his work on the gravitational constant is universal and that he can make a hater cry even after his death.



Featured image by NASA Goddard Space Flight Center, https://flic.kr/p/8t79qk

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