[ad_1]
Neutron stars are covered with “mountains” a few fractions of a millimeter in height, according to new research, which means these bumps are hundreds of times smaller than previous estimates suggested.
Neutron stars are compact stellar objects, similar in size to a large city with a diameter of about 6.2 miles (10 kilometers), that weigh at least 1.4 solar masses (1.4 times the weight of the sun). They are born from the explosive death of stars weighing between 10 and 25 solar masses. As a result, they are among the densest objects in the universe and have an incredibly strong gravitational field, about 2 billion times stronger than Earth‘s. This extreme gravity crushes neutron stars into near-perfect spheres that are surrounded by a smooth, solid crust. However, crustal deformations create mountains on the surface of these stars, according to previous research.
Now new findings, presented at the 2021 UK National Astronomy Meeting on July 19, suggest these mountains are likely to be hundreds of times smaller than scientists previously thought.
Related: 9 epic space discoveries you may have missed in 2020
“They should probably be called ‘bumps’ or ‘hills’, not ‘mountains’,” lead researcher Fabian Gittins, a doctoral student at the University of Southampton in the UK, told Live Science.
An imperfect sphere
The crust of a neutron star is a solid layer on the outside of the star, similar to the earth’s crust, made up of broken heavy element nuclei that contain the ultra-dense soup of neutrons inside the star. ‘star, according to Espace.com. It is about 1 kilometer thick and is the region of the star with the lowest density, Gittins said.
Mountains are formed when the crust is put under tremendous pressure and begins to crack. “There are plenty of ways [for] these mountains are forming, “Gittins said.” All that is needed is for the star to change shape. “
Possible explanations for the formation of the mountain include increased tension due to its strong electromagnetic field or the fact that they spin slower over time. But it can also be caused by a phenomenon known as glitch, in which the star suddenly begins to spin faster, Gittins said.
But whatever the cause of the formation of mountains, their size is limited by the amount of stress the crust can withstand before it breaks. “The stronger the crust, the bigger the mountains it can support,” Gittins said.
Smaller than expected
Gittins and his team predicted the size of mountains of neutron stars by creating computer models that accurately simulate the crust of a neutron star.
“We subjected these models to a variety of mathematical forces that gave rise to mountains,” Gittins said. “We increased the amplitude of the forces until the crust broke.”
This allowed the team to predict the largest possible size of mountains that neutron stars could support without breaking. Their new prediction suggests that earlier estimates that stared at these mountains up to one centimeter in height may have been significantly flawed.
“In examining this problem, we found that previous studies had technical issues with their approach,” Gittins said.
One of the main problems is that previous predictions assumed that the crust of neutron stars had a shape that maximally stretched the crust at each point, but that turned out to be physically impossible, Gittins said. “Our approach did not stretch the crust as much as possible at each point but at a single point,” he added.
Ripples in space-time
Neutron stars are known to spin quickly due to the angular momentum they retain from their exploding mother stars, Gittins said.
“When a neutron star that is asymmetrically deformed spins, it causes ripples in the tissue of space-time around her, ”Gittins said. “These ripples are known as gravitational waves. “
Researchers first gravitational waves detected, emanating from two rotating black holes, using the Laser interferometer gravitational wave observatory (LIGO) in 2015, Live Science already reported. LIGO has since detected two separate gravitational wave events resulting from the collision of neutron stars, Previously reported live science, but lone neutron stars have remained elusive.
“Currently, we have not been able to detect gravitational waves spinning neutron stars, ”Gittins said. But these non-detections also tell a lot to scientists about neutron stars, he added.
The smaller the mountains on neutron stars, the smaller the gravitational waves they produce. Therefore, their lack of detection may support Gittins’ predictions.
“Since we know the sensitivity of our detectors, we can set upper limits for the size of mountains on neutron stars,” Gittins said. “The general trend is that the upper limits are getting smaller and smaller.”
Therefore, it may be some time before scientists can build detectors large enough to detect the spatiotemporal ripples emitted by these rapidly rotating microscopic bumps.
The study was first published online on November 21, 2020 in the journal Monthly notices from the Royal Astronomical Society.
Originally posted on Live Science.
[ad_2]
Source link