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A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects, neutron stars are the smallest and densest currently known class of stellar objects. Neutron stars have a radius on the order of 10 kilometres (6 mi) and a mass of about 1.4 solar masses. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei.
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the current age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are formed from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.
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A pulsar is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward Earth, and is responsible for the pulsed appearance of emission. Neutron stars are very dense and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays.
An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as extended beams along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity.
PSR J0737−3039 is the first known double pulsar. It consists of two neutron stars emitting electromagnetic waves in the radio wavelength in a relativistic binary system. The two pulsars are known as PSR J0737−3039A and PSR J0737−3039B. It was discovered in 2003 at Australia's Parkes Observatory by an international team led by the Italian radio astronomer Marta Burgay during a high-latitude pulsar survey.
Astropulse is a volunteer computing project to search for primordial black holes, pulsars, and extraterrestrial intelligence (ETI). Volunteer resources are harnessed through Berkeley Open Infrastructure for Network Computing (BOINC) platform. In 1999, the Space Sciences Laboratory launched SETI@home, which would rely on massively parallel computation on desktop computers scattered around the world. SETI@home utilizes recorded data from the Arecibo radio telescope and searches for narrow-bandwidth radio signals from space, signifying the presence of extraterrestrial technology. It was soon recognized that this same data might be scoured for other signals of value to the astronomy and physics community.
The Tolman–Oppenheimer–Volkoff limit is an upper bound to the mass of cold, non-rotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. If the mass of a neutron star reaches the limit it will collapse to a denser form, most likely a black hole.
A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magnetic field exerts a force on the plasma, effectively increasing the pressure without a comparable gain in density. As a result, the magnetized region rises relative to the remainder of the plasma, until it reaches the star's photosphere. This creates starspots on the surface, and the related phenomenon of coronal loops.
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface.
Gamma-ray burst progenitors are the types of celestial objects that can emit gamma-ray bursts (GRBs). GRBs show an extraordinary degree of diversity. They can last anywhere from a fraction of a second to many minutes. Bursts could have a single profile or oscillate wildly up and down in intensity, and their spectra are highly variable unlike other objects in space. The near complete lack of observational constraint led to a profusion of theories, including evaporating black holes, magnetic flares on white dwarfs, accretion of matter onto neutron stars, antimatter accretion, supernovae, hypernovae, and rapid extraction of rotational energy from supermassive black holes, among others.
PSR B1937+21 is a pulsar located in the constellation Vulpecula a few degrees in the sky away from the first discovered pulsar, PSR B1919+21. The name PSR B1937+21 is derived from the word "pulsar" and the declination and right ascension at which it is located, with the "B" indicating that the coordinates are for the 1950.0 epoch. PSR B1937+21 was discovered in 1982 by Don Backer, Shri Kulkarni, Carl Heiles, Michael Davis, and Miller Goss.
Fiona A. Harrison is the Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy at Caltech, Harold A. Rosen Professor of Physics at Caltech and the Principal Investigator for NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission. She won the Hans A. Bethe Prize in 2020 for her work on NuSTAR.
Heino Falcke is a German Dutch professor of radio astronomy and astroparticle physics at the Radboud University Nijmegen. He was a winner of the 2011 Spinoza Prize. His main field of study is black holes, and he is the originator of the concept of the 'black hole shadow'. In 2013, a team under his lead earned a 14 million euro research grant from the European Research Council to further studies of black holes. In 2019, Falcke announced the first Event Horizon Telescope results at the EHT Press Conference in Brussels.
Luciano Rezzolla is an Italian professor of relativistic astrophysics and numerical relativity at the Goethe University Frankfurt. His main field of study is the physics and astrophysics of compact objects such as black holes and neutron stars. It was announced in 2019 that he had been appointed honorary Andrews Professor of Astronomy at Trinity College Dublin (TCD).
Richard Van Evera Lovelace is an American astrophysicist and plasma physicist. He is best known for the discovery of the period of the pulsar in the Crab Nebula, which helped to prove that pulsars are rotating neutron stars, for developing a magnetic model of astrophysical jets from galaxies, and for developing a model of Rossby waves in accretion disks. He organized a US-Russia collaboration in plasma astrophysics, which focused on modeling of plasma accretion and outflows from magnetized rotating stars.
References
- ↑ "Afscheidsgroet van een stervende ster" (Press release) (in Dutch). Nijmegen, NL: Radboud University. 4 July 2013. Retrieved 26 July 2015.[ permanent dead link ]
- ↑ Heino Falcke; Luciano Rezzolla (2014). "Fast radio bursts: The last sign of supramassive neutron stars". Astronomy & Astrophysics. 562: A137. arXiv: 1307.1409 . Bibcode:2014A&A...562A.137F. doi:10.1051/0004-6361/201321996. S2CID 32284857.
- ↑ "Mysterious radio flashes may be farewell greetings from massive stars collapsing into black holes". ScienceDaily (Press release). July 2013.
- ↑ "Cosmic radio bursts point to cataclysmic origin". ScienceDaily (Press release). July 2013.
- 1 2 3 Thornton, D.; Stappers, B.; Bailes, M.; Barsdell, B.; Bates, S.; Bhat, N.D.R.; et al. (5 July 2013). "A population of fast radio bursts at cosmological distances". Science. 341 (6141): 53–56. arXiv: 1307.1628 . Bibcode:2013Sci...341...53T. doi:10.1126/science.1236789. PMID 23828936. S2CID 206548502.
For a popular summary see [3] [4] - ↑ "Extremely short, sharp flash of radio waves from unknown source in the universe, caught as it was happening". ScienceDaily (Press release). 19 January 2015. Retrieved 3 March 2016.
- ↑ Falcke, Heino; Rezzolla, Luciano. "Blitzars: Fast radio bursts from supramassive rotating neutron stars". Astronomy. Nijmegen, NL: Radboud University . Retrieved 8 July 2013.
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