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H II region

Index H II region

An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. [1]

106 relations: Andromeda Galaxy, Angular resolution, Astronomical object, Astronomical spectroscopy, Astronomy, Atom, Barnard's Loop, Bart Bok, Bok globule, California Nebula, Carina Nebula, Chandra X-ray Observatory, Chemical element, Density, Density gradient, Doubly ionized oxygen, Einstein Observatory, Electric charge, Electric field, Electron, Electron density, Elliptical galaxy, Emission nebula, Energy level, Forbidden mechanism, Galaxy, Galaxy cluster, Galileo Galilei, Gas, H I region, Helium, Henry Norris Russell, Hertzsprung–Russell diagram, Horsehead Nebula, Hubble Space Telescope, Hydrogen, Hydrogen atom, Infrared, Interstellar medium, Inverse Laplace transform, Ion, Ionization, Irregular galaxy, Johann Bayer, Kelvin, Large Magellanic Cloud, Light, Light-year, Local Group, Magnetic field, ..., Margaret Lindsay Huggins, Metastability, Milky Way, Molecular cloud, Molecule, Monthly Notices of the Royal Astronomical Society, Naked eye, Nanometre, Nebulium, NGC 604, NGC 7822, Nicolas-Claude Fabri de Peiresc, Nucleosynthesis, OB star, Optical spectrometer, Orion (constellation), Orion Molecular Cloud Complex, Orion Nebula, Parsec, Photon, Planetary nebula, Pleiades, Proplyd, Proton, Protoplanetary nebula, Radiation pressure, Radio, Reflection nebula, SN 1987A, Solar mass, Solar System, Spectral line, Speed of sound, Spiral galaxy, Star, Star cluster, Star formation, Starburst galaxy, Stellar evolution, Stellar wind, Strömgren sphere, Sun, Supernova, Supersonic speed, Tarantula Nebula, Telescope, Tesla (unit), Theta1 Orionis C, Trapezium Cluster, Triangulum Galaxy, Ultraviolet, Wavelength, William Herschel, William Huggins, Wolf–Rayet star, X-ray. Expand index (56 more) »

Andromeda Galaxy

The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way.

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Angular resolution

Angular resolution or spatial resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution.

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Astronomical object

An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe.

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Astronomical spectroscopy

Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects.

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Astronomy

Astronomy (from ἀστρονομία) is a natural science that studies celestial objects and phenomena.

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Atom

An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element.

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Barnard's Loop

Barnard's Loop (catalogue designation Sh 2-276) is an emission nebula in the constellation of Orion.

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Bart Bok

Bartholomeus Jan "Bart" Bok (April 28, 1906 – August 5, 1983) was a Dutch-born American astronomer, teacher, and lecturer.

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Bok globule

In astronomy, Bok globules are isolated and relatively small dark nebulae, containing dense cosmic dust and gas from which star formation may take place.

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California Nebula

The California Nebula (NGC 1499) is an emission nebula located in the constellation Perseus.

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Carina Nebula

The Carina Nebula (catalogued as NGC 3372; also known as the Grand Nebula, Great Nebula in Carina, or Eta Carinae Nebula) is a large, complex area of bright and dark nebulosity in the constellation Carina, and is located in the Carina–Sagittarius Arm.

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Chandra X-ray Observatory

The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space observatory launched on STS-93 by NASA on July 23, 1999.

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Chemical element

A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or Z).

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Density

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume.

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Density gradient

Density gradient is a spatial variation in density over an area.

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Doubly ionized oxygen

In astronomy and atomic physics, doubly ionized oxygen is the ion O2+ (also known as O III in spectroscopic notation).

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Einstein Observatory

Einstein Observatory (HEAO-2) was the first fully imaging X-ray telescope put into space and the second of NASA's three High Energy Astrophysical Observatories.

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Electric charge

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.

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Electric field

An electric field is a vector field surrounding an electric charge that exerts force on other charges, attracting or repelling them.

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Electron

The electron is a subatomic particle, symbol or, whose electric charge is negative one elementary charge.

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Electron density

Electron density is the measure of the probability of an electron being present at a specific location.

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Elliptical galaxy

An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless image.

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Emission nebula

An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths.

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Energy level

A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy.

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Forbidden mechanism

In spectroscopy, a forbidden mechanism (forbidden transition or forbidden line) is a spectral line associated with absorption or emission of light by atomic nuclei, atoms, or molecules which undergo a transition that is not allowed by a particular selection rule but is allowed if the approximation associated with that rule is not made.

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Galaxy

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.

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Galaxy cluster

A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity with typical masses ranging from 1014–1015 solar masses.

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Galileo Galilei

Galileo Galilei (15 February 1564Drake (1978, p. 1). The date of Galileo's birth is given according to the Julian calendar, which was then in force throughout Christendom. In 1582 it was replaced in Italy and several other Catholic countries with the Gregorian calendar. Unless otherwise indicated, dates in this article are given according to the Gregorian calendar. – 8 January 1642) was an Italian polymath.

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Gas

Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).

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H I region

An HI region or H I region (read H one) is a cloud in the interstellar medium composed of neutral atomic hydrogen (HI), in addition to the local abundance of helium and other elements.

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Helium

Helium (from lit) is a chemical element with symbol He and atomic number 2.

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Henry Norris Russell

Prof Henry Norris Russell FRS(For) HFRSE FRAS (October 25, 1877 – February 18, 1957) was an American astronomer who, along with Ejnar Hertzsprung, developed the Hertzsprung–Russell diagram (1910).

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Hertzsprung–Russell diagram

The Hertzsprung–Russell diagram, abbreviated H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective temperatures.

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Horsehead Nebula

The Horsehead Nebula (also known as Barnard 33) is a dark nebula in the constellation Orion.

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Hubble Space Telescope

The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation.

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Hydrogen

Hydrogen is a chemical element with symbol H and atomic number 1.

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Hydrogen atom

A hydrogen atom is an atom of the chemical element hydrogen.

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Infrared

Infrared radiation (IR) is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye (although IR at wavelengths up to 1050 nm from specially pulsed lasers can be seen by humans under certain conditions). It is sometimes called infrared light.

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Interstellar medium

In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy.

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Inverse Laplace transform

In mathematics, the inverse Laplace transform of a function F(s) is the piecewise-continuous and exponentially-restricted real function f(t) which has the property: where \mathcal denotes the Laplace transform.

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Ion

An ion is an atom or molecule that has a non-zero net electrical charge (its total number of electrons is not equal to its total number of protons).

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Ionization

Ionization or ionisation, is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical changes.

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Irregular galaxy

An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy.

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Johann Bayer

Johann Bayer (1572 – 7 March 1625) was a German lawyer and uranographer (celestial cartographer).

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Kelvin

The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics.

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Large Magellanic Cloud

The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way.

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Light

Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.

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Light-year

The light-year is a unit of length used to express astronomical distances and measures about 9.5 trillion kilometres or 5.9 trillion miles.

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Local Group

The Local Group is the galaxy group that includes the Milky Way.

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Magnetic field

A magnetic field is a vector field that describes the magnetic influence of electrical currents and magnetized materials.

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Margaret Lindsay Huggins

Margaret Lindsay, Lady Huggins (14 August 1848 in Dublin – 24 March 1915 in London), born Margaret Lindsay Murray, was an Irish-English scientific investigator and astronomer.

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Metastability

In physics, metastability is a stable state of a dynamical system other than the system's state of least energy.

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Milky Way

The Milky Way is the galaxy that contains our Solar System.

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Molecular cloud

A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit the formation of molecules, most commonly molecular hydrogen (H2).

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Molecule

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds.

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Monthly Notices of the Royal Astronomical Society

Monthly Notices of the Royal Astronomical Society (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics.

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Naked eye

Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical instrument, such as a telescope or microscope.

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Nanometre

The nanometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American spelling) is a unit of length in the metric system, equal to one billionth (short scale) of a metre (m).

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Nebulium

Nebulium was a proposed element found in astronomical observation of a nebula by William Huggins in 1864.

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NGC 604

NGC 604 is an H II region inside the Triangulum Galaxy.

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NGC 7822

NGC 7822 is a young star forming complex in the constellation of Cepheus.

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Nicolas-Claude Fabri de Peiresc

Nicolas-Claude Fabri de Peiresc (1 December 1580 – 24 June 1637), often known simply as Peiresc, or by the Latin form of his name Peirescius, was a French astronomer, antiquary and savant, who maintained a wide correspondence with scientists, and was a successful organizer of scientific inquiry.

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Nucleosynthesis

Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons.

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OB star

OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called OB associations.

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Optical spectrometer

An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials.

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Orion (constellation)

Orion is a prominent constellation located on the celestial equator and visible throughout the world.

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Orion Molecular Cloud Complex

The Orion Molecular Cloud Complex (or, simply, the Orion Complex) is a star forming region with stellar ages ranging up to 12 Myr.

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Orion Nebula

The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion.

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Parsec

The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System.

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Photon

The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles).

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Planetary nebula

A planetary nebula, abbreviated as PN or plural PNe, is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.

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Pleiades

The Pleiades (also known as the Seven Sisters and Messier 45), are an open star cluster containing middle-aged, hot B-type stars located in the constellation of Taurus.

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Proplyd

A proplyd, a syllabic abbreviation of an ionized protoplanetary disk, is an externally illuminated photoevaporating disk around a young star.

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Proton

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Protoplanetary nebula

A protoplanetary nebula or preplanetary nebula (PPN) is an astronomical object which is at the short-lived episode during a star's rapid evolution between the late asymptotic giant branch (LAGB) phase and the subsequent planetary nebula (PN) phase.

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Radiation pressure

Radiation pressure is the pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field.

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Radio

Radio is the technology of using radio waves to carry information, such as sound, by systematically modulating properties of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width.

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Reflection nebula

In astronomy, reflection nebulae are clouds of interstellar dust which might reflect the light of a nearby star or stars.

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SN 1987A

SN 1987A was a peculiar type II supernova in the Large Magellanic Cloud, a dwarf galaxy satellite of the Milky Way.

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Solar mass

The solar mass is a standard unit of mass in astronomy, equal to approximately.

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Solar System

The Solar SystemCapitalization of the name varies.

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Spectral line

A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies.

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Speed of sound

The speed of sound is the distance travelled per unit time by a sound wave as it propagates through an elastic medium.

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Spiral galaxy

Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae(pp. 124–151) and, as such, form part of the Hubble sequence.

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Star

A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.

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Star cluster

Star clusters are groups of stars.

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Star formation

Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars.

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Starburst galaxy

A starburst galaxy is a galaxy undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies.

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Stellar evolution

Stellar evolution is the process by which a star changes over the course of time.

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Stellar wind

A stellar wind is a flow of gas ejected from the upper atmosphere of a star.

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Strömgren sphere

In theoretical astrophysics, there can be a sphere of ionized hydrogen (H II) around a young star of the spectral classes O or B. The theory was derived by Bengt Strömgren in 1937 and later named Strömgren sphere after him.

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Sun

The Sun is the star at the center of the Solar System.

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Supernova

A supernova (plural: supernovae or supernovas, abbreviations: SN and SNe) is a transient astronomical event that occurs during the last stellar evolutionary stages of a star's life, either a massive star or a white dwarf, whose destruction is marked by one final, titanic explosion.

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Supersonic speed

Supersonic travel is a rate of travel of an object that exceeds the speed of sound (Mach 1).

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Tarantula Nebula

The Tarantula Nebula (also known as 30 Doradus) is an H II region in the Large Magellanic Cloud (LMC).

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Telescope

A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).

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Tesla (unit)

The tesla (symbol T) is a derived unit of magnetic flux density (informally, magnetic field strength) in the International System of Units.

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Theta1 Orionis C

Theta1 Orionis C (θ1 Orionis C) is a member of the Trapezium open cluster that lies within the Orion Nebula.

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Trapezium Cluster

The Trapezium or Orion Trapezium Cluster, also known by its Bayer designation of Theta1 Orionis, is a tight open cluster of stars in the heart of the Orion Nebula, in the constellation of Orion.

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Triangulum Galaxy

The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years (ly) from Earth in the constellation Triangulum.

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Ultraviolet

Ultraviolet (UV) is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays.

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Wavelength

In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.

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William Herschel

Frederick William Herschel, (Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer, composer and brother of fellow astronomer Caroline Herschel, with whom he worked.

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William Huggins

Sir William Huggins (7 February 1824 – 12 May 1910) was an English astronomer best known for his pioneering work in astronomical spectroscopy together with his wife Margaret Lindsay Huggins.

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Wolf–Rayet star

Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of highly ionised helium and nitrogen or carbon.

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X-ray

X-rays make up X-radiation, a form of electromagnetic radiation.

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Redirects here:

H II, H II Region, HII Region, HII region, HII regions.

References

[1] https://en.wikipedia.org/wiki/H_II_region

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