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?
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.
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.
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.
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.
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.
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.
Right, magnetars. Perhaps one of the most ferocious beasts to inhabit the cosmos. Loud, unruly, and temperamental, they blast their host galaxies with wave after wave of electromagnetic radiation, running the gamut from soft radio waves to hard X-rays. They are rare and poorly understood.
Some of these magnetars spit out a lot of radio waves, and frequently. The perfect way to observe them
would be to have a network of high-quality radio dishes across the world, all
continuously observing to capture every bleep and bloop. Some sort of network
of deep-space dishes.
How in the world could you possibly look inside a star? You could break out the scalpels and other tools of the surgical trade, but good luck getting within a few million kilometers of the surface before your skin melts off. The stars of our universe hide their secrets very well, but astronomers can outmatch their cleverness and have found ways to peer into their hearts using, of all things, sound waves. Continue reading “Scientists are Using Artificial Intelligence to See Inside Stars Using Sound Waves”