Supernova remnant

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SN 1054 remnant (Crab Nebula). Crab Nebula.jpg
SN 1054 remnant ( Crab Nebula ).

A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.

Contents

There are two common routes to a supernova: either a massive star may run out of fuel, ceasing to generate fusion energy in its core, and collapsing inward under the force of its own gravity to form a neutron star or a black hole; or a white dwarf star may accrete material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion.

In either case, the resulting supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light (or approximately 30,000 km/s) and a strong shock wave forms ahead of the ejecta. That heats the upstream plasma up to temperatures well above millions of K. The shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds or thousands of years and over tens of parsecs before its speed falls below the local sound speed.

One of the best observed young supernova remnants was formed by SN 1987A, a supernova in the Large Magellanic Cloud that was observed in February 1987. Other well-known supernova remnants include the Crab Nebula; Tycho, the remnant of SN 1572, named after Tycho Brahe who recorded the brightness of its original explosion; and Kepler, the remnant of SN 1604, named after Johannes Kepler. The youngest known remnant in the Milky Way is G1.9+0.3, discovered in the Galactic Center. [1]

Stages

An SNR passes through the following stages as it expands: [2]

  1. Free expansion of the ejecta, until they sweep up their own weight in circumstellar or interstellar medium. This can last tens to a few hundred years depending on the density of the surrounding gas.
  2. Sweeping up of a shell of shocked circumstellar and interstellar gas. This begins the Sedov-Taylor phase, which can be well modeled by a self-similar analytic solution (see blast wave). Strong X-ray emission traces the strong shock waves and hot shocked gas.
  3. Cooling of the shell, to form a thin (< 1  pc), dense (1 to 100 million atoms per cubic metre) shell surrounding the hot (few million kelvin) interior. This is the pressure-driven snowplow phase. The shell can be clearly seen in optical emission from recombining ionized hydrogen and ionized oxygen atoms.
  4. Cooling of the interior. The dense shell continues to expand from its own momentum. This stage is best seen in the radio emission from neutral hydrogen atoms.
  5. Merging with the surrounding interstellar medium. When the supernova remnant slows to the speed of the random velocities in the surrounding medium, after roughly 30,000 years, it will merge into the general turbulent flow, contributing its remaining kinetic energy to the turbulence.
15-044a-SuperNovaRemnant-PlanetFormation-SOFIA-20150319.jpg
15-044b-SuperNovaRemnant-PlanetFormation-SOFIA-20150319.jpg
Supernova remnant ejecta producing planet-forming material

Types of supernova remnant

There are three types of supernova remnant:

Supernova remnants
PIA22564-SupernovaRemnant-HBH3-20180802.jpg
HBH 3 (Spitzer Space Telescope; August 2, 2018)
PIA22569-SuperNovaRemnant-G54.1+0.3-20181116.jpg
G54.1+0.3 (November 16, 2018)

Remnants which could only be created by significantly higher ejection energies than a standard supernova are called hypernova remnants, after the high-energy hypernova explosion that is assumed to have created them. [3]

Origin of cosmic rays

Supernova remnants are considered the major source of galactic cosmic rays. [4] [5] [6] The connection between cosmic rays and supernovas was first suggested by Walter Baade and Fritz Zwicky in 1934. Vitaly Ginzburg and Sergei Syrovatskii in 1964 remarked that if the efficiency of cosmic ray acceleration in supernova remnants is about 10 percent, the cosmic ray losses of the Milky Way are compensated. This hypothesis is supported by a specific mechanism called "shock wave acceleration" based on Enrico Fermi's ideas, which is still under development. [7]

In 1949, Fermi proposed a model for the acceleration of cosmic rays through particle collisions with magnetic clouds in the interstellar medium. [8] This process, known as the "Second Order Fermi Mechanism", increases particle energy during head-on collisions, resulting in a steady gain in energy. A later model to produce Fermi Acceleration was generated by a powerful shock front moving through space. Particles that repeatedly cross the front of the shock can gain significant increases in energy. This became known as the "First Order Fermi Mechanism". [9]

Supernova remnants can provide the energetic shock fronts required to generate ultra-high energy cosmic rays. Observation of the SN 1006 remnant in the X-ray has shown synchrotron emission consistent with it being a source of cosmic rays. [4] However, for energies higher than about 1018 eV a different mechanism is required as supernova remnants cannot provide sufficient energy. [9]

It is still unclear whether supernova remnants accelerate cosmic rays up to PeV energies. The future telescope CTA will help to answer this question.

See also

Related Research Articles

<span class="mw-page-title-main">SN 1987A</span> 1987 supernova event in the constellation Dorado

SN 1987A was a type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately 51.4 kiloparsecs from Earth and was the closest observed supernova since Kepler's Supernova in 1604. Light and neutrinos from the explosion reached Earth on February 23, 1987 and was designated "SN 1987A" as the first supernova discovered that year. Its brightness peaked in May of that year, with an apparent magnitude of about 3.

Timeline of neutron stars, pulsars, supernovae, and white dwarfs

<span class="mw-page-title-main">Interstellar medium</span> Matter and radiation in the space between the star systems in a galaxy

The interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field. Although the density of atoms in the ISM is usually far below that in the best laboratory vacuums, the mean free path between collisions is short compared to typical interstellar lengths, so on these scales the ISM behaves as a gas, responding to pressure forces, and not as a collection of non-interacting particles.

<span class="mw-page-title-main">Synchrotron radiation</span> Electromagnetic radiation

Synchrotron radiation is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity. It is produced artificially in some types of particle accelerators or naturally by fast electrons moving through magnetic fields. The radiation produced in this way has a characteristic polarization, and the frequencies generated can range over a large portion of the electromagnetic spectrum.

<span class="mw-page-title-main">Fermi Gamma-ray Space Telescope</span> Space telescope for gamma-ray astronomy launched in 2008

The Fermi Gamma-ray Space Telescope, formerly called the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor, is being used to study gamma-ray bursts and solar flares.

<span class="mw-page-title-main">Advanced Composition Explorer</span> NASA satellite of the Explorer program

Advanced Composition Explorer is a NASA Explorer program satellite and space exploration mission to study matter comprising energetic particles from the solar wind, the interplanetary medium, and other sources.

<span class="mw-page-title-main">Pulsar wind nebula</span> Nebula powered by the pulsar wind of a pulsar

A pulsar wind nebula, sometimes called a plerion, is a type of nebula sometimes found inside the shell of a supernova remnant (SNR), powered by winds generated by a central pulsar. These nebulae were proposed as a class in 1976 as enhancements at radio wavelengths inside supernova remnants. They have since been found to be infrared, optical, millimetre, X-ray and gamma ray sources.

<span class="mw-page-title-main">High Energy Stereoscopic System</span> Gamma Ray Telescope System in Namibia

High Energy Stereoscopic System (H.E.S.S.) is a system of imaging atmospheric Cherenkov telescopes (IACTs) for the investigation of cosmic gamma rays in the photon energy range of 0.03 to 100 TeV. The acronym was chosen in honour of Victor Hess, who was the first to observe cosmic rays.

<span class="mw-page-title-main">W49B</span> Supernova remnant nebula in the constellation Aquila

W49B is a nebula in Westerhout 49 (W49). The nebula is a supernova remnant, probably from a type Ib or Ic supernova that occurred around 1,000 years ago. It may have produced a gamma-ray burst and is thought to have left a black hole remnant.

Fermi acceleration, sometimes referred to as diffusive shock acceleration, is the acceleration that charged particles undergo when being repeatedly reflected, usually by a magnetic mirror. It receives its name from physicist Enrico Fermi who first proposed the mechanism. This is thought to be the primary mechanism by which particles gain non-thermal energies in astrophysical shock waves. It plays a very important role in many astrophysical models, mainly of shocks including solar flares and supernova remnants.

<span class="mw-page-title-main">Outline of astronomy</span> Overview of the scientific field of astronomy

The following outline is provided as an overview of and topical guide to astronomy:

<span class="mw-page-title-main">IC 443</span> Supernova remnant in the constellation Gemini

IC 443 is a galactic supernova remnant (SNR) in the constellation Gemini. On the plane of the sky, it is located near the star Eta Geminorum. Its distance is roughly 5,000 light years from Earth.

<span class="mw-page-title-main">Shock waves in astrophysics</span> Astrophysics shock waves

Shock waves are common in astrophysical environments.

<span class="mw-page-title-main">Gamma-ray astronomy</span> Observational astronomy performed with gamma rays

Gamma-ray astronomy is a subfield of astronomy where scientists observe and study celestial objects and phenomena in outer space which emit cosmic electromagnetic radiation in the form of gamma rays, i.e. photons with the highest energies at the very shortest wavelengths. Radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy.

<span class="mw-page-title-main">Patrizia A. Caraveo</span> Italian astrophysicist

Patrizia Caraveo is an Italian astrophysicist.

<span class="mw-page-title-main">Hypernova</span> Supernova that ejects a large mass at unusually high velocity

A hypernova is a very energetic supernova which is believed to result from an extreme core collapse scenario. In this case, a massive star collapses to form a rotating black hole emitting twin astrophysical jets and surrounded by an accretion disk. It is a type of stellar explosion that ejects material with an unusually high kinetic energy, an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater. Hypernovae release such intense gamma rays that they often appear similar to a type Ic supernova, but with unusually broad spectral lines indicating an extremely high expansion velocity. Hypernovae are one of the mechanisms for producing long gamma ray bursts (GRBs), which range from 2 seconds to over a minute in duration. They have also been referred to as superluminous supernovae, though that classification also includes other types of extremely luminous stellar explosions that have different origins.

<span class="mw-page-title-main">Galactic superwind</span> Strong stellar winds of a galactic scale in size

A galactic superwind, or just galactic wind, is a high velocity stellar wind emanating from either newly formed massive stars, spiral density waves, or as the result of the effects of supermassive black holes. They are normally observed in starburst galaxies.

<span class="mw-page-title-main">Kesteven 75</span> Supernova remnant in the constellation Aquila

Kesteven 75, abbreviated as Kes 75 and also called SNR G029.7-00.3, G29.7-0.3 and 4C -03.70, is a supernova remnant located in the constellation Aquila.

<span class="mw-page-title-main">3C 392</span> Superovae remnant interacting with a molecular cloud

3C 392 is a supernova remnant located in the constellation Aquila. It was discovered by Gart Westerhout in 1958 as part of a study of continuous radiation in the Milky Way at a frequency of 1390 MHz.

<span class="mw-page-title-main">CTB 1</span> Large supernova remnant in the constellation Cassiopeia

CTB 1, also known as G116.9+00.1 and AJG 110, is a supernova remnant located in the constellation Cassiopeia. It was discovered as a radio source in 1960 in a study of galactic radiation carried out at a frequency of 960 MHz.

References

  1. Discovery of most recent supernova in our galaxy May 14, 2008
  2. Reynolds, Stephen P. (2008). "Supernova Remnants at High Energy". Annual Review of Astronomy and Astrophysics. 46 (46): 89–126. Bibcode:2008ARA&A..46...89R. doi:10.1146/annurev.astro.46.060407.145237.
  3. Lai, Shih-Ping; Chu, You-Hua; Chen, C.-H. Rosie; Ciardullo, Robin; Grebel, Eva K. (2001). "A Critical Examination of Hypernova Remnant Candidates in M101. I. MF 83". The Astrophysical Journal. 547 (2): 754–764. arXiv: astro-ph/0009238 . Bibcode:2001ApJ...547..754L. doi:10.1086/318420. S2CID   14620463.
  4. 1 2 K. Koyama; R. Petre; E.V. Gotthelf; U. Hwang; et al. (1995). "Evidence for shock acceleration of high-energy electrons in the supernova remnant SN1006". Nature. 378 (6554): 255–258. Bibcode:1995Natur.378..255K. doi:10.1038/378255a0. S2CID   4257238.
  5. "Supernova produces cosmic rays". BBC News . November 4, 2004. Retrieved 2006-11-28.
  6. "SNR and Cosmic Ray Acceleration". NASA Goddard Space Flight Center. Archived from the original on 1999-02-21. Retrieved 2007-02-08.
  7. S.P. Reynolds (2011). "Particle acceleration in supernova-remnant shocks". Astrophysics and Space Science. 336 (1): 257–262. arXiv: 1012.1306 . Bibcode:2011Ap&SS.336..257R. doi:10.1007/s10509-010-0559-8. S2CID   118735190.
  8. E. Fermi (1949). "On the Origin of the Cosmic Radiation". Physical Review. 75 (8): 1169–1174. Bibcode:1949PhRv...75.1169F. doi:10.1103/PhysRev.75.1169.
  9. 1 2 "Ultra-High Energy Cosmic Rays". University of Utah . Retrieved 2006-08-10.