Neutron stars are some of the most extreme objects in the universe: they form from the collapsed cores of supergiants and are compressed into spheres the size of cities, despite being more massive than the Sun.
The dense cores of these alien planets contain material crushed into unique conditions that can’t be replicated or studied on Earth, which is why NASA is on a mission to study neutron stars and learn about the physics that governs the matter inside them.
My colleagues and I have been helping them. Neutron Star To measure the mass, NASA data also allowed scientists to measure the star’s radius, providing the most precise information yet about the strange material inside the star.
What’s inside a neutron star?
The material in the core of a neutron star is even denser than an atomic nucleus. It is the densest, most stable material in the universe, so it is being pushed to its limits and is on the verge of collapse. Black Hole.
Understanding how matter behaves under such conditions is an important test of fundamental physics theories.
NASA Neutron Star Interior Composition Exploration (NICER) Mission We are trying to solve the mystery of this extreme problem.
NICER is an X-ray telescope on the International Space Station that detects X-rays emitted by hot spots on the surfaces of neutron stars, where temperatures reach millions of degrees.
Scientists model the timing and energy of these X-rays to map hotspots and determine the mass and size of the neutron star.
Knowing the relationship between a neutron star’s size and mass reveals the “equation of state” of the matter at its core, which allows scientists to know how soft or stiff the neutron star is — how “compressible” it is — and therefore what it is made of.
A soft equation of state suggests that the neutrons in the core are breaking down into a strange soup of smaller particles; a stiff equation of state might mean that the neutrons resist and form into a larger neutron star.
The equation of state determines how and when a neutron star is destroyed when it explodes. collide.
Unlocking the Mystery of Neutron Star Neighbors
One of NICER’s main targets is a neutron star called PSR J0437-4715, which is the nearest and most luminous neutron star in our solar system, located 10 million light-years away. Pulsar.
Pulsar A neutron star is a neutron star that emits beams of radio waves that are observed as pulses every time it rotates.
This pulsar spins 173 times per second (as fast as a mixer) and we have been observing it for nearly 30 years. MuliyanCSIRO’s Parkes Radio Telescope in New South Wales.
The team working with the NICER data faced a challenge with this pulsar: X-rays from a nearby galaxy made it difficult to accurately model hot spots on the neutron star’s surface.
Fortunately, we were able to independently measure the pulsar’s mass using radio waves — without this critical piece of information, the team would not have been able to determine its exact mass.
Timing is key in measuring the mass of a neutron star
To measure the mass of a neutron star, we rely on effects explained by Einstein’s theory. General theory of relativityThis is called the Shapiro delay.
Large, dense objects, e.g. Pulsar Pulsars, and in this case their companion star, a white dwarf, distort space and time as they orbit each other every 5.74 days.
As the pulse from the pulsar travels across the compressed space-time surrounding the white dwarf to reach us, the pulse is delayed by a factor of microseconds.
frameborder=”0″ allowfullscreen=”allowfullscreen”>
Such microsecond delays can be easily measured in milliseconds from pulsars such as PSR J0437-4715. This pulsar and other millisecond pulsars like it are Parks Pulsar Timing Array Using this pulsar Gravitational waves.
Because PSR J0437-4715 is relatively close to Earth, its orbit appears to wobble slightly from our perspective as Earth orbits the Sun. This wobble gives us more information about the shape of the orbit, which we use in combination with Shapiro delays to find the mass of the white dwarf companion and the pulsar.
Mass and size of PSR J0437-4715
I did some calculations The pulsar has a mass 1.42 times that of the Sun, which is typical of a neutron star. This is important because the size of this pulsar should also be typical of a neutron star.
Scientists working with the NICER data have determined the shape of the X-ray hotspot, The radius of a neutron star is 11.4 kilometers.From these results, Most accurate anchor points The equation of state for neutron stars at intermediate densities has yet to be discovered.
Our new picture already eliminates the equations of state for the softest and hardest neutron stars, and scientists will still have to work out exactly what this means for the presence of exotic matter in the inner cores of neutron stars.
The theory is that this matter may contain quarks. Escaped from normal residence Inside larger particles, or so-called rare particles Hyperon.
frameborder=”0″ allowfullscreen=”allowfullscreen”>
This new data adds to a new model of the interior of a neutron star. observation Gravitational waves caused by the collision of neutron stars and the resulting explosion called a kilonova.
Mulian has a long history of supporting NASA missions and is best known for receiving footage from NASA missions. Most of the Apollo 11 moonwalk.
Today, we are using this iconic telescope to “contribute” to the physics inside neutron stars, improving our fundamental understanding of the universe.
Daniel ReardonPostdoctoral Research Fellow in Pulsar Timing and Gravitational Waves, Swinburne University of Technology
This article is reprinted from conversation Published under a Creative Commons license. Original Article.
