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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. Bok globules are found within H II regions, and typically have a mass of about two to 50 solar masses contained within a region about a light year or so across (about ). They contain molecular hydrogen (H2), carbon oxides and helium, and around 1% (by mass) silicate dust. Bok globules most commonly result in the formation of double- or multiple-star systems. History Bok globules were first observed by astronomer Bart Bok in the 1940s. In an article published in 1947, he and Edith F. Reilly hypothesized that these clouds were "similar to insect's cocoons" that were undergoing gravitational collapse to form new stars, from which stars and star clusters were born. This hypothesis was difficult to verify due to the observational difficulties of establishing what was happening inside a dense dark cloud that obscured all visible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Finger Of God Globule
The "Finger of God" globule is a Bok globule and dark nebula located around 7,300 light-years away from Earth, within the Carina Nebula. It is ~2 light years across, and got its name due to the finger-like shape located directly on top of the main nebula. Etymology The name "Finger of God" came from the structure located on the northern tip of the globule. It is also informally called "God's Birdie" or the "Defiant Finger", named for its resemblance to a hand with its middle finger raised, which is sometimes referred to as "flipping the bird". Location The globule is located near the Keyhole nebula, Keyhole Nebula, which itself is located within the Carina Nebula. It is positioned near many other small Bok globules, and is one of the larger objects in its area. Description The Finger of God is a relatively small Bok globule located inside of the Carina Nebula. It has an elongated shape, and 2 distinct regions. The first is the "hand" or "wrist", which is the large, bulging p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Year
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astronomical Union (IAU), a light-year is the distance that Speed of light, light travels in vacuum in one Julian year (astronomy), Julian year (365.25 days). Despite its inclusion of the word "year", the term should not be misinterpreted as a unit of time. The ''light-year'' is most often used when expressing distances to stars and other distances on a Galaxy, galactic scale, especially in public understanding of science, non-specialist contexts and popular science publications. The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years). Definitions As defined by the International Astronomical Union (IAU), the light-year is the product of the Julian year (astronomy), Julian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bipolar Outflow
A bipolar outflow comprises two continuous flows of gas from the poles of a star. Bipolar outflows may be associated with protostars (young, forming stars), or with evolved post-AGB stars (often in the form of bipolar nebulae). Protostars In the case of a young star, the bipolar outflow is driven by a dense, collimated jet. These astrophysical jets are narrower than the outflow and very difficult to observe directly. However, supersonic shock fronts along the jet heat the gas in and around the jet to thousands of degrees. These pockets of hot gas radiate at infrared wavelengths and thus can be detected with telescopes like the United Kingdom Infrared Telescope (UKIRT). They often appear as discrete knots or arcs along the beam of the jet. They are usually called molecular bow shocks, since the knots are usually curved like the bow wave at the front of a ship. Occurrence Typically, molecular bow shocks are observed in ro-vibrational emission from hot molecular hydro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbig–Haro Object
Herbig–Haro (HH) objects are bright patches of nebula, nebulosity associated with newborn stars. They are formed when narrow jets of partially plasma (physics), ionised gas ejected by stars collide with nearby clouds of gas and dust at several hundred kilometers per second. Herbig–Haro objects are commonly found in Star formation#Stellar nurseries, star-forming regions, and several are often seen around a single star, aligned with its axis of rotation, rotational axis. Most of them lie within about one parsec (3.26 light-years) of the source, although some have been observed several parsecs away. HH objects are transient phenomena that last around a few tens of thousands of years. They can change visibly over timescales of a few years as they move rapidly away from their parent star into the gas clouds of interstellar space (the interstellar medium or ISM). Hubble Space Telescope observations have revealed the complex evolution of HH objects over the period of a few years, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of red light (the longest waves in the visible spectrum), so IR is invisible to the human eye. IR is generally (according to ISO, CIE) understood to include wavelengths from around to . IR is commonly divided between longer-wavelength thermal IR, emitted from terrestrial sources, and shorter-wavelength IR or near-IR, part of the solar spectrum. Longer IR wavelengths (30–100 μm) are sometimes included as part of the terahertz radiation band. Almost all black-body radiation from objects near room temperature is in the IR band. As a form of EMR, IR carries energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. It was long known that fires e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visible Spectrum
The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optical spectrum is sometimes considered to be the same as the visible spectrum, but some authors define the term more broadly, to include the ultraviolet and infrared parts of the electromagnetic spectrum as well, known collectively as ''optical radiation''. A typical human eye will respond to wavelengths from about 380 to about 750 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 400–790 Terahertz (unit), terahertz. These boundaries are not sharply defined and may vary per individual. Under optimal conditions, these limits of human perception can extend to 310 nm (ultraviolet) and 1100 nm (near infrared). The spectrum does not contain all the colors that the human visual system can distinguish. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Cluster
A star cluster is a group of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters, tight groups of ten thousand to millions of old stars which are gravitationally bound; and open clusters, less tight groups of stars, generally containing fewer than a few hundred members. As they move through the galaxy, over time, open clusters become disrupted by the gravitational influence of giant molecular clouds, so that the clusters we observe are often young. Even though they are no longer gravitationally bound, they will continue to move in broadly the same direction through space and are then known as stellar associations, sometimes referred to as ''moving groups''. Globular clusters, with more members and more mass, remain intact for far longer and the globular clusters we observe are usually billions of years old. Star clusters visible to the naked eye include the Pleiades and Hyades (star cluster), Hyades open clusters, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sky, night; their immense distances from Earth make them appear as fixed stars, fixed points of light. The most prominent stars have been categorised into constellations and asterism (astronomy), asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated to stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy. A star's life star formation, begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and traces of heavier elements. Its stellar mass, total mass mainly determines it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitational Collapse
Gravitational collapse is the contraction of an astronomical object due to the influence of its own gravity, which tends to draw matter inward toward the center of gravity. Gravitational collapse is a fundamental mechanism for structure formation in the universe. Over time an initial, relatively smooth distribution of matter, after sufficient accretion, may collapse to form pockets of higher density, such as stars or black holes. Star formation involves a gradual gravitational collapse of interstellar medium into clumps of molecular clouds and potential protostars. The compression caused by the collapse raises the temperature until thermonuclear fusion occurs at the center of the star, at which point the collapse gradually comes to a halt as the outward thermal pressure balances the gravitational forces. The star then exists in a state of dynamic equilibrium. During the star's evolution a star might collapse again and reach several new states of equilibrium. Star formation A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cocoon (silk)
A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages thereof being egg, larva, pupa, and imago. The processes of entering and completing the pupal stage are controlled by the insect's hormones, especially juvenile hormone, prothoracicotropic hormone, and ecdysone. The act of becoming a pupa is called pupation, and the act of emerging from the pupal case is called eclosion or emergence. The pupae of different groups of insects have different names such as ''chrysalis'' for the pupae of butterflies and ''tumbler'' for those of the mosquito family. Pupae may further be enclosed in other structures such as cocoons, nests, or shells. Position in life cycle The pupal stage follows the larval stage, or in some cases a prepupal stage, and precedes adulthood ('' imago'') in insects with compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edith F
Edith is a feminine given name derived from the Old English word , meaning ''wealth'' or ''prosperity'', in combination with the Old English , meaning ''strife'', and is in common usage in this form in English, German, many Scandinavian languages and Dutch. Its French form is Édith. Contractions and variations of this name include Ditte, Dita, and Edie. It was a common first name prior to the 16th century, when it fell out of favour. It became popular again at the beginning of the 19th century and has remained in steady use. It has been among the top hundred most popular names for newborn girls in England and Wales since 2017. It has been among the top 1,000 names for girls in the United States since 1880 and was among the top 50 names for American girls between 1880 and 1927, the height of its popularity. It was ranked as the 513th most popular name for American newborn girls in 2022, according to the Social Security online database. It was the 518th most popular name for newb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Star
A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars using a telescope, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough, they can gravitationally distort each other's outer stellar atmospheres. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
