The Pressure Inside Every Proton is 10x That Inside Neutron Stars

Neutron stars are famous for combining a very high-density with a very small radius. As the remnants of massive stars that have undergone gravitational collapse, the interior of a neutron star is compressed to the point where they have similar pressure conditions to atomic nuclei. Basically, they become so dense that they experience the same amount of internal pressure as the equivalent of 2.6 to 4.1 quadrillion Suns!

In spite of that, neutron stars have nothing on protons, according to a recent study by scientists at the Department of Energy’s Thomas Jefferson National Accelerator Facility. After conducting the first measurement of the mechanical properties of subatomic particles, the scientific team determined that near the center of a proton, the pressure is about 10 times greater than the pressure in the heart of a neutron star.

The study which describes the team’s findings, titled “The pressure distribution inside the proton“, recently appeared in the scientific journal Nature. The study was led by Volker Burkert, a nuclear physicist at the Thomas Jefferson National Accelerator Facility (TJNAF), and co-authored by Latifa Elouadrhiri and Francois-Xavier Girod – also from the TJNAF.

Cross-section of a neutron star. Credit: Wikipedia Commons/Robert Schulze

Basically , they found that the pressure conditions at the center of a proton were 100 decillion pascals – about 10 times the pressure at the heart of a neutron star. However, they also found that pressure inside the particle is not uniform, and drops off as the distance from the center increases. As Volker Burkert, the Jefferson Lab Hall B Leader, explained:

“We found an extremely high outward-directed pressure from the center of the proton, and a much lower and more extended inward-directed pressure near the proton’s periphery… Our results also shed light on the distribution of the strong force inside the proton. We are providing a way of visualizing the magnitude and distribution of the strong force inside the proton. This opens up an entirely new direction in nuclear and particle physics that can be explored in the future.”

Protons are composed of three quarks that are bound together by the strong nuclear force, one of the four fundamental forces that government the Universe – the other being electromagnetism, gravity and weak nuclear forces. Whereas electromagnetism and gravity produce the effects that govern matter on the larger scales, weak and strong nuclear forces govern matter at the subatomic level.

Previously, scientists thought that it was impossible to obtain detailed information about subatomic particles. However, the researchers were able to obtain results by pairing two theoretical frameworks with existing data, which consisted of modelling systems that rely on electromagnetism and gravity. The first model concerns generalized parton distributions (GDP) while the second involve gravitational form factors.

Quarks inside a proton experience a force an order of magnitude greater than matter inside a neutron star. Credit: DOE’s Jefferson Lab

Patron modelling refers to modeling subatomic entities (like quarks) inside protons and neutrons, which allows scientist to create 3D images of a proton’s or neutron’s structure (as probed by the electromagnetic force). The second model describes the scattering of subatomic particles by classical gravitational fields, which describes the mechanical structure of protons when probed via the gravitational force.

As noted, scientists previously thought that this was impossible due to the extreme weakness of the gravitational interaction. However, recent theoretical work has indicated that it could be possible to determine the mechanical structure of a proton using electromagnetic probes as a substitute for gravitational probes. According to Latifa Elouadrhiri – a Jefferson Lab staff scientist and co-author on the paper – that is what their team set out to prove.

“This is the beauty of it. You have this map that you think you will never get,” she said. “But here we are, filling it in with this electromagnetic probe.”

For the sake of their study, the team used the DOE’s Continuous Electron Beam Accelerator Facility at the TJNAF to create a beam of electrons. These were then directed into the nuclei of atoms where they interacted electromagnetically with the quarks inside protons via a process called deeply virtual Compton scattering (DVCS). In this process, an electron exchanges a virtual photon with a quark, transferring energy to the quark and proton.

The bare masses of all 6 flavors of quarks, proton and electron, shown in proportional volume. Credit: Wikipedia/Incnis Mrsi

Shortly thereafter, the proton releases this energy by emitting another photon while remaining intact. Through this process, the team was able to produced detailed information of the mechanics going on in inside the protons they probed. As Francois-Xavier Girod, a Jefferson Lab staff scientist and co-author on the paper, explained the process:

“There’s a photon coming in and a photon coming out. And the pair of photons both are spin-1. That gives us the same information as exchanging one graviton particle with spin-2. So now, one can basically do the same thing that we have done in electromagnetic processes — but relative to the gravitational form factors, which represent the mechanical structure of the proton.”

The next step, according to the research team, will be to apply the technique to even more precise data that will soon be released. This will reduce uncertainties in the current analysis and allow the team to reveal other mechanical properties inside protons – like the internal shear forces and the proton’s mechanical radius. These results, and those the team hope to reveal in the future, are sure to be of interest to other physicists.

“We are providing a way of visualizing the magnitude and distribution of the strong force inside the proton,” said Burkert. “This opens up an entirely new direction in nuclear and particle physics that can be explored in the future.”

Perhaps, just perhaps, it will bring us closer to understanding how the four fundamental forces of the Universe interact. While scientists understand how electromagnetism and weak and strong nuclear forces interact with each other (as described by Quantum Mechanics), they are still unsure how these interact with gravity (as described by General Relativity).

If and when the four forces can be unified in a Theory of Everything (ToE), one of the last and greatest hurdles to a complete understanding of the Universe will finally be removed.

Further Reading: Jefferson Lab, Cosmos Magazine, Nature

What Are The Parts Of An Atom?

Since the beginning of time, human beings have sought to understand what the universe and everything within it is made up of. And while ancient magi and philosophers conceived of a world composed of four or five elements – earth, air, water, fire (and metal, or consciousness) – by classical antiquity, philosophers began to theorize that all matter was actually made up of tiny, invisible, and indivisible atoms.

Since that time, scientists have engaged in a process of ongoing discovery with the atom, hoping to discover its true nature and makeup. By the 20th century, our understanding became refined to the point that we were able to construct an accurate model of it. And within the past decade, our understanding has advanced even further, to the point that we have come to confirm the existence of almost all of its theorized parts.

Continue reading “What Are The Parts Of An Atom?”

Cosmologist Thinks a Strange Signal May Be Evidence of a Parallel Universe

In the beginning, there was chaos.

Hot, dense, and packed with energetic particles, the early Universe was a turbulent, bustling place. It wasn’t until about 300,000 years after the Big Bang that the nascent cosmic soup had cooled enough for atoms to form and light to travel freely. This landmark event, known as recombination, gave rise to the famous cosmic microwave background (CMB), a signature glow that pervades the entire sky.

Now, a new analysis of this glow suggests the presence of a pronounced bruise in the background — evidence that, sometime around recombination, a parallel universe may have bumped into our own.

Although they are often the stuff of science fiction, parallel universes play a large part in our understanding of the cosmos. According to the theory of eternal inflation, bubble universes apart from our own are theorized to be constantly forming, driven by the energy inherent to space itself.

Like soap bubbles, bubble universes that grow too close to one another can and do stick together, if only for a moment. Such temporary mergers could make it possible for one universe to deposit some of its material into the other, leaving a kind of fingerprint at the point of collision.

Ranga-Ram Chary, a cosmologist at the California Institute of Technology, believes that the CMB is the perfect place to look for such a fingerprint.

This image, the best map ever of the Universe, shows the oldest light in the universe. This glow, left over from the beginning of the cosmos called the cosmic microwave background, shows tiny changes in temperature represented by color. Credit: ESA and the Planck Collaboration.
The cosmic microwave background (CMB), a pervasive glow made of light from the Universe’s infancy, as seen by the Planck satellite in 2013. Tiny deviations in average temperature are represented by color. Credit: ESA and the Planck Collaboration.

After careful analysis of the spectrum of the CMB, Chary found a signal that was about 4500x brighter than it should have been, based on the number of protons and electrons scientists believe existed in the very early Universe. Indeed, this particular signal — an emission line that arose from the formation of atoms during the era of recombination — is more consistent with a Universe whose ratio of matter particles to photons is about 65x greater than our own.

There is a 30% chance that this mysterious signal is just noise, and not really a signal at all; however, it is also possible that it is real, and exists because a parallel universe dumped some of its matter particles into our own Universe.

After all, if additional protons and electrons had been added to our Universe during recombination, more atoms would have formed. More photons would have been emitted during their formation. And the signature line that arose from all of these emissions would be greatly enhanced.

Chary himself is wisely skeptical.

“Unusual claims like evidence for alternate Universes require a very high burden of proof,” he writes.

Indeed, the signature that Chary has isolated may instead be a consequence of incoming light from distant galaxies, or even from clouds of dust surrounding our own galaxy.

SO is this just another case of BICEP2? Only time and further analysis will tell.

Chary has submitted his paper to the Astrophysical Journal. A preprint of the work is available here.

What’s the Big Deal About the Pentaquark?

“Three quarks for Muster Mark!,” wrote James Joyce in his labyrinthine fable, Finnegan’s Wake. By now, you may have heard this quote – the short, nonsensical sentence that eventually gave the name “quark” to the Universe’s (as-yet-unsurpassed) most fundamental building blocks. Today’s physicists believe that they understand the basics of how quarks combine; three join up to form baryons (everyday particles like the proton and neutron), while two – a quark and an antiquark – stick together to form more exotic, less stable varieties called mesons. Rare four-quark partnerships are called tetraquarks. And five quarks bound in a delicate dance? Naturally, that would be a pentaquark. And the pentaquark, until recently a mere figment of physics lore, has now been detected at the LHC!

So what’s the big deal? Far from just being a fun word to say five-times-fast, the pentaquark may unlock vital new information about the strong nuclear force. These revelations could ultimately change the way we think about our superbly dense friend, the neutron star – and, indeed, the nature of familiar matter itself.

Physicists know of six types of quarks, which are ordered by weight. The lightest of the six are the up and down quarks, which make up the most familiar everyday baryons (two ups and a down in the proton, and two downs and an up in the neutron). The next heaviest are the charm and strange quarks, followed by the top and bottom quarks. And why stop there? In addition, each of the six quarks has a corresponding anti-particle, or antiquark.

Six types of quark, arranged from left to right by way of their mass, depicted along with the other elementary particles of the Standard Model. The Higgs boson was added to the right side of the menagerie in 2012. (Image Credit: Fermilab)

An important attribute of both quarks and their anti-particle counterparts is something called “color.” Of course, quarks do not have color in the same way that you might call an apple “red” or the ocean “blue”; rather, this property is a metaphorical way of communicating one of the essential laws of subatomic physics – that quark-containing particles (called hadrons) always carry a neutral color charge.

For instance, the three components of a proton must include one red quark, one green quark, and one blue quark. These three “colors” add up to a neutral particle in the same way that red, green, and blue light combine to create a white glow. Similar laws are in place for the quark and antiquark that make up a meson: their respective colors must be exactly opposite. A red quark will only combine with an anti-red (or cyan) antiquark, and so on.

The pentaquark, too, must have a neutral color charge. Imagine a proton and a meson (specifically, a type called a J/psi meson) bound together – a red, a blue, and a green quark in one corner, and a color-neutral quark-antiquark pair in the other – for a grand total of four quarks and one antiquark, all colors of which neatly cancel each other out.

Physicists are not sure whether the pentaquark is created by this type of segregated arrangement or whether all five quarks are bound together directly; either way, like all hadrons, the pentaquark is kept in check by that titan of fundamental dynamics, the strong nuclear force.

The strong nuclear force, as its name implies, is the unspeakably robust force that glues together the components of every atomic nucleus: protons and neutrons and, more crucially, their own constituent quarks. The strong force is so tenacious that “free quarks” have never been observed; they are all confined far too tightly within their parent baryons.

But there is one place in the Universe where quarks may exist in and of themselves, in a kind of meta-nuclear state: in an extraordinarily dense type of neutron star. In a typical neutron star, the gravitational pressure is so tremendous that protons and electrons cease to be. Their energies and charges melt together, leaving nothing but a snug mass of neutrons.

Physicists have conjectured that, at extreme densities, in the most compact of stars, adjacent neutrons within the core may even themselves disintegrate into a jumble of constituent parts.

The neutron star… would become a quark star.

The difference between a neutron star and a quark star (Chandra)
The difference between a neutron star and a quark star. (Image Credit: Chandra)

Scientists believe that understanding the physics of the pentaquark may shed light on the way the strong nuclear force operates under such extreme conditions – not only in such overly dense neutron stars, but perhaps even in the first fractions of a second following the Big Bang. Further analysis should also help physicists refine their understanding of the ways that quarks can and cannot combine.

The data that gave rise to this discovery – a whopping 9-sigma result! – came out of the LHC’s first run (2010-2013). With the supercollider now operating at double its original energy capacity, physicists should have no problem unraveling the mysteries of the pentaquark even further.

A preprint of the pentaquark discovery, which has been submitted to the journal Physical Review Letters, can be found here.

Weekly Space Hangout – June 5, 2015: Stephen Fowler, Creative Director at InfoAge

Host: Fraser Cain (@fcain)
Special Guest: This week we welcome Stephen Fowler, who is the Creative Director at InfoAge, the organization behind refurbishing the TIROS 1 dish and the Science History Learning Center and Museum at Camp Evans, Wall, NJ.

Jolene Creighton (@jolene723 /
Morgan Rehnberg ( / @MorganRehnberg )

Continue reading “Weekly Space Hangout – June 5, 2015: Stephen Fowler, Creative Director at InfoAge”

Russian Proton Rocket Fails After Launch, Destroys Satellite: Reports

About nine minutes after launching towards space, a Russian Proton rocket reportedly crashed Friday (May 16), destroying an advanced satellite being carried on board. The incident happened about 540 seconds after liftoff, after the events of the video shown above.

Russian news site RT (among others) reported that the rocket and Express-AM4R mainly burned up in the atmosphere, meaning no physical damage would be caused to the ground. But this failure marks the latest of several for the Russian rocket type in recent years.

“The exact cause is hard to establish immediately; we will be studying the telemetry. Preliminary information points to an emergency pressure drop in a steering engine of the third stage of the rocket,” said Oleg Ostapenko, the head of the Russian Federal Space Agency (Roscosmos), in a quote cited in RT.

The third stage is called a Breeze-M and reportedly experienced an emergency engine shutdown after the rocket veered on to a different trajectory than it was supposed to. Proton launches have ceased at the Baikonur Space Center in Kazakhstan pending an investigation.

The satellite was supposed to provide “TV and radio broadcasting, broadband Internet access, multimedia services, telephony, [and] mobile communications,” according to the Russian Satellite Communications Company.

Media reports say there have been six failures of this rocket type in the last three or four years. You can read about some of the past failures on Universe Today here:

Rocket Failures May Spur Change In Russian Federal Space Agency: Report (October 2013)

Russian Rocket Fails During Launch, Explodes After Liftoff (July 2013)

– Weekend Update: SpaceX Success, Russian Launch Failure (December 2010)

Satellite Fails To Reach Proper Orbit (March 2008)

Rocket Failures May Spur Change In Russian Federal Space Agency: Report

It appears that the Russian government wants to take action over the string of unmanned mission failures beleaguering Roscosmos, or the Russian Federal Space Agency. A recent example includes the loss in June of three GLONASS navigation/positioning satellites in a launch failure. In 2011, Roscosmos lost four major missions, including the Phobos-Grunt spacecraft that was bound for the Martian moon Phobos.

RIA Novosti reports that Dmitry Rogozin, Russia’s deputy prime minister, plans to create a new state entity to take over space manufacturing. The proposed United Rocket and Space Corporation, the report says, will reduce the reliance on imported parts to get missions off the ground, among other aims.

“A new state corporation will be created to take over manufacturing facilities from the Federal Space Agency, whose prestige has been severely dented in recent years by a string of failed rocket launches,” the report says. “The proposed United Rocket and Space Corporation will enable the trimming away of redundant departments replicated elsewhere in the space industry.”

As for Roscosmos itself, the report hints that other changes could be on the way. Its envisioned role is to “act as a federal executive body and contracting authority for programs to be implemented by the industry.” There are expected to be changes in management, among other measures.

The agency was formed after the breakup of the Soviet Union in 1991 and is responsible for most of Russia’s space activities. Russia’s heritage in space actually stretches back to the dawn of the space age in the 1950s and 1960s, when the country became the first nation to launch a satellite (Sputnik) and a human (Yuri Gagarin), among other milestones.

Read the whole report in Roscosmos.

Measuring Fundamental Constants with Methanol

Diagram of the methanol molecule



Key to the astronomical modeling process by which scientists attempt to understand our universe, is a comprehensive knowledge of the values making up these models. These are generally measured to exceptionally high confidence levels in laboratories. Astronomers then assume these constants are just that – constant. This generally seems to be a good assumption since models often produce mostly accurate pictures of our universe. But just to be sure, astronomers like to make sure these constants haven’t varied across space or time. Making sure, however, is a difficult challenge. Fortunately, a recent paper has suggested that we may be able to explore the fundamental masses of protons and electrons (or at least their ratio) by looking at the relatively common molecule of methanol.

The new report is based on the complex spectra of the methane molecule. In simple atoms, photons are generated from transitions between atomic orbitals since they have no other way to store and translate energy. But with molecules, the chemical bonds between the component atoms can store the energy in vibrational modes in much the same way masses connected to springs can vibrate. Additionally, molecules lack radial symmetry and can store energy by rotation. For this reason, the spectra of cool stars show far more absorption lines than hot ones since the cooler temperatures allow molecules to begin forming.

Many of these spectral features are present in the microwave portion of the spectra and some are extremely dependent on quantum mechanical effects which in turn depend on precise masses of the proton and electron. If those masses were to change, the position of some spectral lines would change as well. By comparing these variations to their expected positions, astronomers can gain valuable insights to how these fundamental values may change.

The primary difficulty is that, in the grand scheme of things, methanol (CH3OH) is rare since our universe is 98% hydrogen and helium. The last 2% is composed of every other element (with oxygen and carbon being the next most common). Thus, methanol is comprised of three of the four most common elements, but they have to find each other, to form the molecule in question. On top of that, they must also exist in the right temperature range; too hot and the molecule is broken apart; too cold and there’s not enough energy to cause emission for us to detect it. Due to the rarity of molecules with these conditions, you might expect that finding enough of it, especially across the galaxy or universe, would be challenging.

Fortunately, methanol is one of the few molecules which are prone to creating astronomical masers. Masers are the microwave equivalent of lasers in which a small input of light can cause a cascading effect in which it induces the molecules it strikes to also emit light at specific frequencies. This can greatly enhance the brightness of a cloud containing methanol, increasing the distance to which it could be readily detected.

By studying methanol masers within the Milky Way using this technique, the authors found that, if the ratio of the mass of an electron to that of a proton does change, it does so by less than three parts in one hundred million. Similar studies have also been conducted using ammonia as the tracer molecule (which can also form masers) and have come to similar conclusions.


Particle Collider

Particles made up of three quarks are called baryons; the two best known baryons are the proton (made up of two up quarks and one down) and the neutron (two down quarks and one up). Together with the mesons – particles comprised of a quark and an antiquark – baryons form the hadrons (you’ve heard of hadrons, they’re part of the name of the world’s most powerful particle collider, the Large Hadron Collider, the LHC).

Because they’re made up of quarks, baryons ‘feel’ the strong force (or strong nuclear force as it is also called), which is mediated by gluons. The other kind of particle which makes up ordinary matter is leptons, which are not – as far as we know – made up of anything (and as they do not contain quarks, they do not participate in the strong interaction … which is another way of saying they do not experience the strong force); the electron is one kind of lepton. Baryons and leptons are fermions, so obey the Pauli exclusion principle (which, among other things, says that there can be no more than one fermion in a particular quantum state at any time … and ultimately why you do not fall through your chair).

In the kinds of environments we are familiar with in everyday life, the only stable baryon is the proton; in the environment of the nuclei of most atoms, the neutron is also stable (and in the extreme environment of a neutron star too); there are, however, hundreds of different kinds of unstable baryons.

One big, open question in cosmology is how baryons were formed – baryogenesis – and why are there essentially no anti-baryons in the universe. For every baryon, there is a corresponding anti-baryon … there is, for example, the anti-proton, the anti-baryon counterpart to the proton, made up of two up anti-quarks and one down anti-quark. So if there were equal numbers of baryons and anti-baryons to start with, how come there are almost none of the latter today?

Astronomers often use the term ‘baryonic matter’, to refer to ordinary matter; it’s a bit of a misnomer, because it includes electrons (which are leptons) … and it generally excludes neutrinos (and anti-neutrinos), which are also leptons! Perhaps a better term might be matter which interacts via electromagnetism (i.e. feels the electromagnetic force), but that’s a bit of a mouthful. Non-baryonic matter is what (cold) dark matter (CDM) is composed of; CDM does not interact electromagnetically.

The Particle Data Group maintains summary tables of the properties of all known baryons. A relatively new area of research in astrophysics (and cosmology) is baryon acoustic oscillations (BAO); read more about it at this Los Alamos National Laboratory website …

… and in the Universe Today article New Search for Dark Energy Goes Back in Time. Other Universe Today stories featuring baryons explicitly include Is Dark Matter Made Up of Sterile Neutrinos?, and Astronomers on Supernova High Alert.


Charge of Electron

Charge of Electron


The charge of the electron is equivalent to the magnitude of the elementary charge (e) but bearing a negative sign. Since the value of the elementary charge is roughly 1.602 x 10-19 coulombs (C), then the charge of the electron is -1.602 x 10-19 C.

When expressed in atomic units, the elementary charge takes the value of unity; i.e., e = 1. Thus, the electron’s charge can be denoted by -e. Although the proton is much more massive than the electron, it only has a charge of e. Hence, neutral atoms always bear the same number of protons and electrons.

JJ Thomson is the undisputed discoverer of the electron. However, despite all those experiments he performed on it, he could only manage to obtain the electron’s charge to mass ratio. The distinction of being the first to measure the electron’s charge goes to Robert Millikan through his oil-drop experiment in 1909.

The Millikan Oil-Drop Experiment

Here’s the basic idea. If you know the density and dimensions (thus subsequently the volume) of a substance, it’s going to be easy to calculate its mass and the force that gravity exerts on it, a.k.a. weight. If you recall, weight is just m x g.

Now let’s assume these substances to be charged oil drops. If you subject these drops to gravity alone, they’ll fall freely. However, if they are allowed to fall in a uniform electric field, their trajectory will be altered depending on the direction and magnitude of the field.

If the forces due to the field are directed opposite to gravity, the downward velocity of the particles may decrease. At some point, when the upward force is equal to the downward force, the velocities may even go down to zero and the particles will stay in mid-air.

At this specific instance, if we know the magnitude of the electric field (in N/C, units defining the force per unit charge) and the weight of each particle, we can calculate the force of the electric field on a single particle and finally derive the charge.

Thus, a basic Millikan Oil-Drop Experiment setup will include an enclosure containing falling charged oil drops, a device to measure their radii, an adjustable uniform electric field, and a meter to determine the field’s magnitude.

By repeating the experiment on a large number of oil drops, Millikan and his colleague, Harvey Fletcher, obtained electron charge values within 1% of the currently accepted one.

We have some articles in Universe Today that are related to the charge of the electron. Here are two of them:

Physics World also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

GSU Hyperphysics
University of Alaska-Fairbanks