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PKS 0521-365
PKS 0521-365 is an active galactic nucleus in the constellation Columba. The source (BL Lac object) is a strong emitter from radio to gamma frequencies Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq .... The object is at z = 0.055. BL Lacertae objects Columba (constellation) {{galaxy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parkes Catalogue Of Radio Sources
The Parkes Catalogue of Radio Sources, also known as the Parkes Southern Radio Source Catalog, consists of 8264 astronomical radio sources, mostly south of declination +27. The catalogue was mostly compiled by John Bolton and his colleagues for 20 years. Both the Molonglo 408-MHz survey and the 80-MHz Culgoora measurements of Slee et al have contributed to the usefulness of the catalogue. For now, the catalogue only contains sources originally found in the Parkes 2700-MHz survey. The catalogue contains radio sources that have a frequency range of 80 - 22,000 MHz. Objects * PKS 0521-365 * PKS 0637-752 * PKS 1209-51/52 * PKS 1302-102 * PKS 0548-322 * PKS 1727-21 (Kepler’s Supernova) * PKS 2000-330 * PKS 2014-55 * PKS 2155-304 * PKS 2201+044 * PKS-2349-014 * PKS 2357+00 (PGC 1) See also * Astronomical catalogues *List of astronomical catalogues An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a instant, moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a Astronomical object, celestial body, as they are subject to Perturbation (astronomy), perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or Perihelion and aphelion, aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Columba (constellation)
Columba is a faint constellation designated in the late sixteenth century, remaining in official use, with its rigid limits set in the 20th century. Its name is Latin for dove. It takes up 1.31% of the southern celestial hemisphere and is just south of Canis Major and Lepus. History * Early 3rd century BC: Aratus's astronomical poem ''Phainomena'' (lines 367–370 and 384–385) mentions faint stars where Columba is now but does not fit any name or figure to them. * 2nd century AD: Ptolemy listed 48 constellations in the ''Almagest'' but did not mention Columba. * c. 150–215 AD: Clement of Alexandria wrote in his ''Logos Paidogogos''"Αἱ δὲ σφραγῖδες ἡμῖν ἔστων πελειὰς ἢ ἰχθὺς ἢ ναῦς οὐριοδρομοῦσα ἢ λύρα μουσική, ᾗ κέχρηται Πολυκράτης, ἢ ἄγκυρα ναυτική," (= " hen recommending symbols for Christians to use let our seals be a dove or a fish or a ship running in a good ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BL Lac Object
A BL Lacertae object or BL Lac object is a type of active galactic nucleus (AGN) or a galaxy with such an AGN, named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization. Because of these properties, the prototype of the class ( BL Lac) was originally thought to be a variable star. When compared to the more luminous active nuclei ( quasars) with strong emission lines, BL Lac objects have spectra dominated by a relatively featureless non-thermal emission continuum over the entire electromagnetic range. This lack of spectral lines historically hindered identification of the nature and distance of such objects. In the unified scheme of radio-loud active galactic nuclei, the observed nuclear phenomenology of BL Lacs is interpreted as being due to the effects of the relativistic jet closely aligned to the line of sight of the observer. BL Lac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Galactic Nucleus
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess non-stellar emission has been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an "active galaxy". The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy. Active galactic nuclei are the most luminous persistent sources of electromagnetic radiation in the universe, and as such can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on models of the cosmos. The observed characteristics of an AGN depend on several properties such as the mass of the central black hole, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way. Subsequent observations have identified a number of different sources of radio emission. These include stars and galaxies, as well as entirely new classes of objects, such as radio galaxies, quasars, pulsars, and masers. The discovery of the cosmic microwave background radiation, regarded as evidence for the Big Bang theory, was made through radio astronomy. Radio astronomy is conducted using large radio antennas referred to as radio telescopes, that are either used singularly, or with multiple linked telescopes utilizing the techniques of radio interferometry and aperture synthesis. The use of interferometry allows radio astronomy to achieve high angular resolution, as the resolving power of an interferometer is set ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma-ray Astronomy
Gamma-ray astronomy is the astronomical observation of gamma rays,Astronomical literature generally hyphenates "gamma-ray" when used as an adjective, but uses "gamma ray" without a hyphen for the noun. the most energetic form of electromagnetic radiation, with photon energies above 100 keV. Radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy. In most known cases, gamma rays from solar flares and Earth's atmosphere are generated in the MeV range, but it is now known that gamma rays in the GeV range can also be generated by solar flares. It had been believed that gamma rays in the GeV range do not originate in the Solar System. As GeV gamma rays are important in the study of extra-solar, and especially extra-galactic, astronomy, new observations may complicate some prior models and findings. The mechanisms emitting gamma rays are diverse, mostly identical with those emitting X-rays but at higher energies, including electron–positro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. There is no known limit for long and short wavelengths. Extreme ultr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redshift
In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in frequency and energy, is known as a negative redshift, or blueshift. The terms derive from the colours red and blue which form the extremes of the visible light spectrum. In astronomy and cosmology, the three main causes of electromagnetic redshift are # The radiation travels between objects which are moving apart (" relativistic" redshift, an example of the relativistic Doppler effect) #The radiation travels towards an object in a weaker gravitational potential, i.e. towards an object in less strongly curved (flatter) spacetime (gravitational redshift) #The radiation travels through expanding space (cosmological redshift). The observation that all sufficiently distant light sources show redshift corresponding to their distance from Earth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BL Lacertae Objects
A BL Lacertae object or BL Lac object is a type of active galactic nucleus (AGN) or a galaxy with such an AGN, named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization. Because of these properties, the prototype of the class ( BL Lac) was originally thought to be a variable star. When compared to the more luminous active nuclei ( quasars) with strong emission lines, BL Lac objects have spectra dominated by a relatively featureless non-thermal emission continuum over the entire electromagnetic range. This lack of spectral lines historically hindered identification of the nature and distance of such objects. In the unified scheme of radio-loud active galactic nuclei, the observed nuclear phenomenology of BL Lacs is interpreted as being due to the effects of the relativistic jet closely aligned to the line of sight of the observer. BL Lac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
