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Messier 94
Messier 94 (also known as NGC 4736) is a spiral galaxy in the mid-northern constellation Canes Venatici. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier two days later. Although some references describe M94 as a barred spiral galaxy, the "bar" structure appears to be more oval-shaped. The galaxy has two ring structures. Structure M94 is classified as having a low ionization nuclear emission region (LINER) nucleus. LINERs in general are characterized by optical spectra that reveal that ionized gas is present but the gas is only weakly ionized (i.e. the atoms are missing relatively few electrons). M94 has an inner ring with a diameter of 70 arcseconds (″) (given its distance, about ) and an outer ring with a diameter of 600″ (about ). These rings appear to form at resonance points in the disk of the galaxy. The inner ring is the site of strong star formation activity and is sometimes referred to as a starburst ring. This star form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messier Object
The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only interested in finding comets, he created a list of those non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as ''the Messier catalogue''. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier numbers. The catalogue includes most of the astronomical deep-sky objects that can easily be observed from Earth's Northern Hemisphere; many Messier objects are popular targets for amateur astronomers. A preliminary version first appeared in 1774 in the ''Memoirs'' of the French Academy of Sciences for the year 1771. The first version of Messier's catalogue conta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pierre Méchain
Pierre François André Méchain (; 16 August 1744 – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep-sky objects and comets. Life Pierre Méchain was born in Laon, the son of the ceiling designer and plasterer Pierre François Méchain and Marie–Marguerite Roze. He displayed mental gifts in mathematics and physics but had to give up his studies for lack of money. However, his talents in astronomy were noticed by Jérôme Lalande, for whom he became a friend and proof-reader of the second edition of his book "L'Astronomie". Lalande then secured a position for him as assistant hydrographer with the Naval Depot of Maps and Charts at Versailles, where he worked through the 1770s engaged in hydrography, hydrographic work and coastline surveying. It was during this time—approximately 1774—that he met Charles Messier, and apparently, they became friends. In the same year, he also produced his ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Journal
''The Astronomical Journal'' (often abbreviated ''AJ'' in scientific papers and references) is a peer-reviewed monthly scientific journal owned by the American Astronomical Society (AAS) and currently published by IOP Publishing. It is one of the premier journals for astronomy in the world. Until 2008, the journal was published by the University of Chicago Press on behalf of the AAS. The reasons for the change to the IOP were given by the society as the desire of the University of Chicago Press to revise its financial arrangement and their plans to change from the particular software that had been developed in-house. The other two publications of the society, the ''Astrophysical Journal'' and its supplement series, followed in January 2009. The journal was established in 1849 by Benjamin A. Gould. It ceased publication in 1861 due to the American Civil War, but resumed in 1885. Between 1909 and 1941 the journal was edited in Albany, New York. In 1941, editor Benjamin Boss arran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Starburst (astronomy)
A starburst is an astrophysical process that involves star formation occurring at a rate that is large compared to the rate that is typically observed. This starburst activity will consume the available interstellar gas supply over a timespan that is much shorter than the lifetime of the galaxy. For example, the nebula NGC 6334 has a star formation rate estimated to be 3600 solar masses per million years compared to the star formation rate of the entire Milky Way of about seven million solar masses per million years. Due to the high amount of star formation a starburst is usually accompanied by much higher gas pressure and a larger ratio of hydrogen cyanide to carbon monoxide emission-lines than are usually observed. Starbursts can occur in entire galaxies or just regions of space. A starburst region is a region of space that is undergoing a large amount of star formation. For example, the Tarantula Nebula is a nebula in the Large Magellanic Cloud which has one of the highest s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Formation
Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space, sometimes referred to as "stellar nurseries" or "-forming regions", and form s. As a branch of , star formation includes the study of the interstellar medium (ISM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resonance
Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied Periodic function, periodic force (or a Fourier analysis, Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an Oscillation, oscillating force is applied at a resonant frequency of a dynamic system, the system will oscillate at a higher Amplitude, amplitude than when the same force is applied at other, non-resonant frequencies. Frequencies at which the response amplitude is a relative maximum are also known as resonant frequencies or resonance frequencies of the system. Small periodic forces that are near a resonant frequency of the system have the ability to produce large amplitude oscillations in the system due to the storage of vibrational energy. Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, orbital resonance, acoustic resonance, Electromagnetic radiation, electromagnet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arcsecond
A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth circumference is very near . A minute of arc is of a radian. A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol , is of an arcminute, of a degree, of a turn, and (about ) of a radian. These units originated in Babylonian astronomy as sexagesimal subdivisions of the degree; they are used in fields that involve very small angles, such as astronomy, optometry, ophthalmology, optics, navigation, land surveying, and marksmanship. To express even smaller angles, standard SI prefixes can be employed; the milliarcsecond (mas) and microarcsecond (μas), for instance, are commonly used in as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Spectroscopy
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects. A stellar spectrum can reveal many properties of stars, such as their chemical composition, temperature, density, mass, distance and luminosity. Spectroscopy can show the velocity of motion towards or away from the observer by measuring the Doppler shift. Spectroscopy is also used to study the physical properties of many other types of celestial objects such as planets, nebulae, galaxies, and active galactic nuclei. Background Astronomical spectroscopy is used to measure three major bands of radiation in the electromagnetic spectrum: visible light, radio waves, and X-rays. While all spectroscopy looks at specific bands of the spectrum, different methods are required to acquire the signal depending on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysical Journal Supplement
''The Astrophysical Journal'', often abbreviated ''ApJ'' (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler. The journal discontinued its print edition and became an electronic-only journal in 2015. Since 1953 ''The Astrophysical Journal Supplement Series'' (''ApJS'') has been published in conjunction with ''The Astrophysical Journal'', with generally longer articles to supplement the material in the journal. It publishes six volumes per year, with two 280-page issues per volume. ''The Astrophysical Journal Letters'' (''ApJL''), established in 1967 by Subrahmanyan Chandrasekhar as Part 2 of ''The Astrophysical Journal'', is now a separate journal focusing on the rapid publication of high-impact astronomical research. The three journals were published by the University of Chicago Press for the American Astronomical Society ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low Ionization Nuclear Emission Region
A low-ionization nuclear emission-line region (LINER) is a type of galactic nucleus that is defined by its spectral line emission. The spectra typically include line emission from weakly ionized or neutral atoms, such as O, O+, N+, and S+. Conversely, the spectral line emission from strongly ionized atoms, such as O++, Ne++, and He+, is relatively weak. The class of galactic nuclei was first identified by Timothy Heckman in the third of a series of papers on the spectra of galactic nuclei that were published in 1980. Demographics of LINER galaxies Galaxies that contain LINERs are often referred to as ''LINER galaxies''. LINER galaxies are very common; approximately one-third of all nearby galaxies (galaxies within approximately 20-40 Mpc) may be classified as LINER galaxies. Approximately 75% of LINER galaxies are either elliptical galaxies, lenticular galaxies, or S0/a-Sab galaxies (spiral galaxies with large bulges and tightly wound spiral arms). LINERs are f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Starburst Galaxy Messier 94
MicroPro International Corporation was an American software company founded in 1978 in San Rafael, California. They are best known as the publisher of WordStar, a popular early word processor for personal computers. History Founding and early success Seymour I. Rubinstein was an employee of early microcomputer company IMSAI, where he negotiated software contracts with Digital Research and Microsoft. After leaving IMSAI, Rubinstein planned to start his own software company that would sell through the new network of retail computer stores. He founded MicroPro International Corporation in September 1978 and hired John Robbins Barnaby as programmer, who wrote a word processor, WordMaster, and a sorting program, SuperSort, in Intel 8080 assembly language. After Rubinstein obtained a report that discussed the abilities of contemporary standalone word processors from IBM, Xerox, and Wang Laboratories, Barnaby enhanced WordMaster with similar features and support for the CP/ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annual Review Of Astronomy And Astrophysics
The ''Annual Review of Astronomy and Astrophysics'' is an annual peer reviewed scientific journal published by Annual Reviews. The co-editors are Ewine van Dishoeck and Robert C. Kennicutt. The journal reviews scientific literature pertaining to local and distant celestial entities throughout the observable universe, as well as cosmology, instrumentation, techniques, and the history of developments. It was established in 1963. History In November of 1960, the board of directors of the nonprofit publisher Annual Reviews began investigating the need for a new journal of review articles that covered developments in astronomy and astrophysics. The board consulted an advisory group of experts, including Ronald Bracewell, Robert Jastrow, Joseph Kaplan, Paul Merrill, Otto Struve, and Harold Urey. The editorial committee met in August 1961 to determine the authors and topics for the first volume, which was published in 1963. As of 2020, it was published both in print and electronicall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
