Twin Stars Prove Einstein at Least 99.99% Right

Artistic impression of the Double Pulsar system, where two active pulsars orbit each other in just 147 min. The orbital motion of these extremely dense neutrons star causes a number of relativistic effects, including the creation of ripples in spacetime known as gravitational waves. The gravitational waves carry away energy from the systems which shrinks by about 7mm per days as a result. The corresponding measurement agrees with the prediction of general relativity within 0.013%. The picture at high resolution and two alternative versions (1b, 1c) are accessible in the left column. [less] © Michael Kramer/MPIfR

More than a hundred years have passed since Einstein formalized his theory of General Relativity (GR), the geometric theory of gravitation that revolutionized our understanding of the Universe. And yet, astronomers are still subjecting it to rigorous tests, hoping to find deviations from this established theory. The reason is simple: any indication of physics beyond GR would open new windows onto the Universe and help resolve some of the deepest mysteries about the cosmos.

One of the most rigorous tests ever was recently conducted by an international team of astronomers led by Michael Kramer of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany. Using seven radio telescopes from across the world, Kramer and his colleagues observed a unique pair of pulsars for 16 years. In the process, they observed effects predicted by GR for the first time, and with an accuracy of at least 99.99%!

Continue reading “Twin Stars Prove Einstein at Least 99.99% Right”

Astronomers can use Pulsars to Measure Tiny Changes of Acceleration Within the Milky Way, Scanning Internally for Dark Matter and Dark Energy

Using pulsars to measure mass distribution in the Milky Way. Credit: Dana Berry, IAS

As our Sun moves along its orbit in the Milky Way, it is gravitationally tugged by nearby stars, nebulae, and other masses. Our galaxy is not a uniform distribution of mass, and our Sun experiences small accelerations in addition to its overall orbital motion. Measuring those small tugs has been nearly impossible, but a new study shows how it can be done.

Continue reading “Astronomers can use Pulsars to Measure Tiny Changes of Acceleration Within the Milky Way, Scanning Internally for Dark Matter and Dark Energy”

Astronomers Measure a 1-billion Tesla Magnetic Field on the Surface of a Neutron Star

Artist's impression of an Accreting X-Ray Pulsar drawing material from its companion star. - NASA

We recently observed the strongest magnetic field ever recorded in the Universe. The record-breaking field was discovered at the surface of a neutron star called GRO J1008-57 with a magnetic field strength of approximately 1 BILLION Tesla. For comparison, the Earth’s magnetic field clocks in at about 1/20,000 of a Tesla – tens of trillions of times weaker than you’d experience on this neutron star…and that is a good thing for your general health and wellbeing.

Neutron stars are the “dead cores” of once massive stars which have ended their lives as supernova. These stars exhausted their supply of hydrogen fuel in their core and a power balance between the internal energy of the star surging outward, and the star’s own massive gravity crushing inward, is cataclysmically unbalanced – gravity wins. The star collapses in on itself. The outer layers fall onto the core crushing it into the densest object we know of in the Universe – a neutron star. Even atoms are crushed. Negatively charged electrons are forced into the atomic nuclei meeting their positive proton counterparts creating more neutrons. When the core can be crushed no further, the outer remaining material of the star rebounds back into space in a massive explosion – a supernova. The resulting neutron star, made of the crushed stellar core, is so dense that a single sugar-cube-sized sampling would weigh billions of tons – as much as a mountain (though if you’re “worthy” you MIGHT able to lift it since Thor’s Hammer is made of the stuff). Neutron stars are typically about 20km in diameter and can still be a million degrees Kelvin at the surface.

But if they’re “dead,” how can neutron stars be some of the most magnetic and powerful objects in the Universe?

Composite image of the maelstrom at the heart of the Crab Nebula powered by a neutron star – Chandra X-Ray Observatory
Continue reading “Astronomers Measure a 1-billion Tesla Magnetic Field on the Surface of a Neutron Star”

Why Pulsars Are So Bright

Pulsars are fast-spinning neutron stars that emit narrow, sweeping beams of radio waves. A new study identifies the origin of those radio waves. NASA’s Goddard Space Flight Center
Pulsars are fast-spinning neutron stars that emit narrow, sweeping beams of radio waves. A new study identifies the origin of those radio waves. NASA’s Goddard Space Flight Center

When pulsars were first discovered in 1967, their rhythmic radio-wave pulsations were a mystery. Some thought their radio beams must be of extraterrestrial origin.

We’ve learned a lot since then. We know that pulsars are magnetized, rotating neutrons stars. We know that they rotate very rapidly, with their magnetic poles sending sweeping beams of radio waves out into space. And if they’re aimed the right way, we can “see” them as pulses of radio waves, even though the radio waves are steady. They’re kind of like lighthouses.

But the exact mechanism that creates all of that electromagnetic radiation has remained a mystery.

Continue reading “Why Pulsars Are So Bright”

A Star Has Been Found That Pulsates, But Only on One Side

An artist’s impression of the star with its tidally locked red dwarf companion. Credit: Gabriel Pérez Díaz (IAC)

In the 17th century, astronomers witnessed many stellar events that proved that the starry sky was not “fixed and eternal.” This included stars whose brightness varied over time – aka. “variable stars.” By the 20th century, many variable stars had been cataloged and astronomers have discerned subclasses of them as well – notably, stars that swell and shrink, known as pulsating variables.

In all cases, these variable stars were found to have rhythmic pulsations that were visible from all sides. But a recent discovery by an international team has confirmed that there are variable stars that can pulse from only one side. This pulsating star, part of a system known as HD 74423, is located about 1,500 light-years from Earth and is the first of its kind to be found.

Read more

Halo Around a Pulsar could Explain Why We See Antimatter Coming from Space

Astronomers have been watching a nearby pulsar with a strange halo around it. That pulsar might answer a question that’s puzzled astronomers for some time. The pulsar is named Geminga, and it’s one of the nearest pulsars to Earth, about 800 light years away in the constellation Gemini. Not only is it close to Earth, but Geminga is also very bright in gamma rays.

Continue reading “Halo Around a Pulsar could Explain Why We See Antimatter Coming from Space”

Astronomers Map the Surface of a Pulsar

Simulation of a possible quadrupole magnetic field configuration for a pulsar with hot spots in only the southern hemisphere. Credits: NASA's Goddard Space Flight Center

When stars exhaust their supply of fuel, they collapse under their own weight and explode, blowing off their outer layers in an event known as a “supernova”. In some cases, these events leave behind neutron stars, the smallest and densest of stellar objects (with the exception of certain theoretical stars) that sometimes spin rapidly. Pulsars, a class of neutron star, can spin up to several hundred times per second.

One such object, designated J0030+0451 (J0030), is located about 1,100 light-years from Earth in the Pisces constellation. Recently, scientists using NASA’s Neutron star Interior Composition Explorer (NICER) were able to measure the pulsar’s size and mass. In the process, they also managed to locate the various “hot spots” on its surface, effectively creating the first map of a neutron star.

Continue reading “Astronomers Map the Surface of a Pulsar”

This is the Milky Way’s Magnetic Field

A representation of how our Galaxy would look in the sky if we could see magnetic fields. The plane of the Galaxy runs horizontally through the middle, and the Galactic centre direction is the middle of the map. Red–pink colours show increasing Galactic magnetic field strengths where the direction is pointing towards the Earth. Blue–purple colours show increasing Galactic magnetic field strengths where the direction is pointing away from the Earth. The background shows the signal reconstructed using sources outside our Galaxy. The points show the current measurements for pulsars. The squares show the measurements from this work using LOFAR pulsar observations. Image Credit: Sobey et al, 2019.

The Milky Way galaxy has its own magnetic field. It’s extremely weak compared to Earth’s; thousands of times weaker, in fact. But astronomers want to know more about it because of what it can tell us about star formation, cosmic rays, and a host of other astrophysical processes.

Continue reading “This is the Milky Way’s Magnetic Field”

Neutron Star Suffers a “Glitch”, Gives Astronomers a Glimpse Into How They Work

An image of the Vela pulsar in combined optical and xray. Image Credit: NASA/Chandra

What, exactly, is the inside of a neutron star like?

A neutron star is what remains after a massive star goes supernova. It’s a tightly-packed, ultra-dense body made of—you guessed it—neutrons. Actually, that’s not absolutely true.

Continue reading “Neutron Star Suffers a “Glitch”, Gives Astronomers a Glimpse Into How They Work”

Pulsar Seen Speeding Away From the Supernova That Created it

Observations using the Very Large Array (orange) reveal the needle-like trail of pulsar J0002+6216 outside the shell of its supernova remnant, shown in image from the Canadian Galactic Plane Survey. The pulsar escaped the remnant some 5,000 years after the supernova explosion. Credit: NRAO

When a star exhausts its nuclear fuel towards the end of its lifespan, it undergoes gravitational collapse and sheds its outer layers. This results in a magnificent explosion known as a supernova, which can lead to the creation of a black hole, a pulsar or a white dwarf. And despite decades of observation and research, there is still much scientists don’t know about this phenomena.

Luckily, ongoing observations and improved instruments are leading to all kinds of discoveries that offer chances for new insights. For instance, a team of astronomers with the National Radio Astronomy Observatory (NRAO) and NASA recently observed a “cannonball” pulsar speeding away from the supernova that is believed to have created it. This find is already providing insights into how pulsars can pick up speed from a supernova.

Continue reading “Pulsar Seen Speeding Away From the Supernova That Created it”