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HR Delphini
HR Delphini, also known as Nova Delphini 1967, was a nova which appeared in the constellation Delphinus in 1967. It was discovered by George Alcock at 22:35 UT on 8 July 1967, after searching the sky for over 800 hours with binoculars. At the time of discovery it had an apparent magnitude of 5.0. It reached a peak brightness of magnitude 3.5 on 13 December 1967, making it easily visible to the naked eye around that time. Pre-outburst photographs taken with the Samuel Oschin telescope showed it as a ~12th magnitude star which might have been variable. HR Delphini was discovered 158 days before it reached peak brightness, and its light curve around the peak was very well observed. It had a very slow rise to maximum brightness, when compared to other classical novae. It took 230 days for HR Delphini to fade from its peak by 3 magnitudes, which makes it a "slow" nova. Its decline from peak brightness showed several brief outbursts, leading to its light curve being class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delphinus (constellation)
Delphinus (Pronounced or ) is a small constellation in the Northern Celestial Hemisphere, close to the celestial equator. Its name is the Latin version for the Greek word for dolphin (). It is one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations recognized by the International Astronomical Union. It is one of the smaller constellations, ranked 69th in size. Delphinus' five brightest stars form a distinctive asterism symbolizing a dolphin with four stars representing the body and one the tail. It is bordered (clockwise from north) by Vulpecula, Sagitta, Aquila, Aquarius, Equuleus and Pegasus. Delphinus is a faint constellation with only two stars brighter than an apparent magnitude of 4, Beta Delphini (Rotanev) at magnitude 3.6 and Alpha Delphini (Sualocin) at magnitude 3.8. Mythology Delphinus is associated with two stories from Greek mythology. According to myth, the first Greek god Poseidon wanted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectral Type
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grating into a spectrum exhibiting the Continuum (spectrum), rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The ''spectral class'' of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters ''O'', ''B'', ''A'', ''F'', ''G'', ''K'', and ''M'', a sequence from the hottest (''O'' type) to the coo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1967 In Science
The year 1967 in science and technology involved some significant events, listed below. Anthropology * October 12 – Desmond Morris publishes ''The Naked Ape''. Astronomy and space exploration * January 27 – Astronauts Gus Grissom, Ed White, and Roger B. Chaffee are killed in a fire during a plugs-out test for Apollo 1. * January 27 – The United States, Soviet Union and UK sign the Outer Space Treaty. * April 20 – Surveyor 3 probe lands on the Moon. * April 24 – Soviet cosmonaut Vladimir Komarov is killed during the landing of Soyuz 1. * October 18 – The Soviet Venera 4 probe descends through the Venusian atmosphere, which it analyzes. * October 19 – Mariner 5 probe flies by Venus. * November 9 – Apollo program: NASA launches a Saturn V rocket carrying the unmanned Apollo 4 test spacecraft from Cape Kennedy. * November – Pulsars discovered by Jocelyn Bell Burnell working with Antony Hewish at the University of Cambridge, for which Hewish is awarded a Nobel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Novae
A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramatic appearance of a nova vary, depending on the circumstances of the two progenitor stars. All observed novae involve white dwarfs in close binary systems. The main sub-classes of novae are classical novae, recurrent novae (RNe), and dwarf novae. They are all considered to be cataclysmic variable stars. Classical nova eruptions are the most common type. They are likely created in a close binary star system consisting of a white dwarf and either a main sequence, subgiant, or red giant star. When the orbital period falls in the range of several days to one day, the white dwarf is close enough to its companion star to start drawing accreted matter onto the surface of the white dwarf, which creates a dense but shallow atmosphere. This atmosphe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned both as a vital research tool and as a public relations boon for astronomy. The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center (GSFC) controls the spacecraft. Hubble features a mirror, and its five main instruments observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. Hubble's orbit outside the distortion of Earth's atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes. It has recorded some of the most detaile ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forbidden Mechanism
In spectroscopy, a forbidden mechanism (forbidden transition or forbidden line) is a spectral line associated with absorption or emission of photons 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. For example, in a situation where, according to usual approximations (such as the electric dipole approximation for the interaction with light), the process cannot happen, but at a higher level of approximation (e.g. magnetic dipole, or electric quadrupole) the process is allowed but at a low rate. An example is phosphorescent glow-in-the-dark materials, which absorb light and form an excited state whose decay involves a spin flip, and is therefore forbidden by electric dipole transitions. The result is emission of light slowly over minutes or hours. Should an atomic nucleus, atom or molecule be raised to an excited state and should the transiti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H-alpha
H-alpha (Hα) is a specific deep-red visible spectral line in the Balmer series with a wavelength of 656.28 nm in air and 656.46 nm in vacuum; it occurs when a hydrogen electron falls from its third to second lowest energy level. H-alpha light is the brightest hydrogen line in the visible spectral range. It is important to astronomers as it is emitted by many emission nebulae and can be used to observe features in the Sun's atmosphere, including solar prominences and the chromosphere. Balmer series According to the Bohr model of the atom, electrons exist in quantized energy levels surrounding the atom's nucleus. These energy levels are described by the principal quantum number ''n'' = 1, 2, 3, ... . Electrons may only exist in these states, and may only transit between these states. The set of transitions from ''n'' ≥ 3 to ''n'' = 2 is called the Balmer series and its members are named sequentially by Greek letters: *''n'' = 3 to ''n'' = 2 is called Balmer-alpha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emission Nebula
An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emission nebulae are H II regions, in which star formation is taking place and young, massive stars are the source of the ionizing photons; and planetary nebulae, in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them. General information Usually, a young star will ionize part of the same cloud from which it was born, although only massive, hot stars can release sufficient energy to ionize a significant part of a cloud. In many emission nebulae, an entire cluster of young stars is contributing energy. Stars that are cooler than around 25,000K don't give off enough ultraviolet radiation with wavelengths shorter than 91.2nm (the wavelength needed in order to ionize Hydrogen atoms). This results in the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nova Remnant
A nova remnant is made up of the material either left behind by a sudden explosive fusion eruption by classical novae, or from multiple ejections by recurrent novae. Over their short lifetimes, nova shells show expansion velocities of around 1000 km/s, whose faint nebulosities are usually illuminated by their progenitor stars via light echos as observed with the spherical shell of Nova Persei 1901 or the energies remaining in the expanding bubbles like T Pyxidis. Form Most novae require a close binary system, with a white dwarf and a main sequence, sub-giant, or red giant star, or the merging of two red dwarfs, so probably all nova remnants must be associated with binaries. This theoretically means these nebula shapes might be affected by their central progenitor stars and the amount of matter ejected by novae. The shapes of these nova nebulae are of much interest to modern astrophysicists. Nova remnants when compared to supernova remnants or planetary nebulae generate muc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name ''white dwarf'' was coined by Willem Luyten in 1922. White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen- fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nova
A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramatic appearance of a nova vary, depending on the circumstances of the two progenitor stars. All observed novae involve white dwarfs in close binary systems. The main sub-classes of novae are classical novae, recurrent novae (RNe), and dwarf novae. They are all considered to be cataclysmic variable stars. Classical nova eruptions are the most common type. They are likely created in a close binary star system consisting of a white dwarf and either a main sequence, subgiant, or red giant star. When the orbital period falls in the range of several days to one day, the white dwarf is close enough to its companion star to start drawing accreted matter onto the surface of the white dwarf, which creates a dense but shallow atmosphere. This atmosphe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Bank Observatory
The Green Bank Observatory (previously National Radio Astronomy Observatory, Green Bank) is an astronomical observatory located in the National Radio Quiet Zone in Green Bank, West Virginia, U.S. It is the operator of the Robert C. Byrd Green Bank Telescope, the world's largest fully steerable radio telescope. The observatory was established as the National Science Foundation's (NSF) National Radio Astronomy Observatory (NRAO) in 1956 and made its first observations in 1958. It served as the NRAO's headquarters until 1966, after which the facility was known as the National Radio Astronomy Observatory, Green Bank. In October 2016, the observatory became an independent institution following a 2012 recommendation that the NSF fully divest itself from the facility by October 1, 2016. Green Bank Observatory subsequently retained partial NSF funding, established private contracts, and formed a partnership with West Virginia University. It is operated by the nonprofit Associated Univ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
