A division of astronomical objects between rocky objects, liquid objects, gaseous objects (including gas giants and stars), and plasma objects may be natural and informative.
The astronomy of such gaseous objects may be called gaseous-object astronomy.
The surface of the Sun emits in the red (621 to 750 nm) wavelengths.
When any effort to acquire a system of laws or knowledge focusing on an astr, aster, or astro, that is, any natural body in the sky especially at night, succeeds even in its smallest measurement, astronomy is the name of the effort and the result.
Def. matter "that can be contained only if it is fully surrounded by a solid (or in a bubble of liquid) (or held together by gravitational pull); it can condense into a liquid, or can (rarely) become a solid directly" is called a gas.
"Turbines have been around for a long time—windmills and water wheels are early examples. The name comes from the Latin turbo, meaning vortex, and thus the defining property of a turbine is that a fluid or gas turns the blades of a rotor, which is attached to a shaft that can perform useful work."
Def. relating "to, or existing as, gas" is called gaseous.
Theoretical gaseous-object astronomy
Here's a theoretical definition:
Def. astronomy that studies gaseous objects is called gaseous-object astronomy.
Def. any physical or material thing, entity, or substance is called a body.
- 1.a: "any natural luminous body visible in the sky [especially] at night",
- 1.b: "a self-luminous gaseous celestial body of great mass whose shape is [usually] spheroidal and whose size may be as small as the earth or larger than the earth's orbit".
is called a star.
The right image is the first X-ray image ever made of Venus. It "shows a half crescent due to the relative orientation of the Sun, Earth and Venus. The X-rays from Venus are produced by fluorescent radiation from oxygen and other atoms in the atmosphere between 120 and 140 kilometers above the surface of the planet." The fluorescent source of the X-rays places Venus in the gas dwarf category even though a rocky object lies some 120 km beneath this layer.
While natural objects in the sky, especially at night, may be sensed by sight, sound, smell, taste, or touch (vibration), many have been seen from the light they emit, absorb, reflect, transmit, or fluoresce.
"[T]he evolution of star accretion onto a supermassive gaseous object in the central region of an active galactic nucleus [may be addressed using] a gaseous model of relaxing dense stellar systems".
Gaseous objects have at least one chemical element or compound present in the gaseous state. These gaseous components make up at least 50 % of the detectable portion of the gaseous object.
The familiar red H-alpha [Hα 656 nm] spectral line of hydrogen gas, which is the transition from the shell n = 3 to the Balmer series shell n = 2, is one of the conspicuous colors of the universe. It contributes a bright red line to the spectra of emission or ionization nebula, like the Orion Nebula, which are often H II regions found in star forming regions. In true-color pictures, these nebula have a distinctly pink color from the combination of visible Balmer lines that hydrogen emits.
A "high-resolution spectrum of the Becklin-Neugebauer (BN) infrared point source located in [the region of the Orion Nebula] ... with the Steward Observatory 2.29 m (90 inch) telescope ... [confirmed] the reality of [the 2.12 μ] line ... on 1976 January 15 and 16. The line was then identified by R. Treffers as the S(1) line of the 1-0 vibration-rotation quadrupole spectrum of H2. Six other lines of the same band were also found. The presence of two of our lines has been confirmed by Grasdalen and Joyce (1976). Electronic transitions of interstellar H2 have previously been observed in the ultraviolet (Carruthers 1970; Smith 1973; Spitzer et al. 1973)."
Depending primarily upon gas temperature, the presence of gas may be used to determine the composition of the gas object observed, at least the outer layer. Early spectroscopy of the Sun using estimates of "the line intensities of several lines by eye [to derive] the abundances of ... elements ... [concluded] that the Sun [is] largely made of hydrogen."
"[H]igh-resolution spectral measurements of Mercury show emission in sodium D lines (Potter and Morgan 1985a). This suggests a substantial sodium population in Mercury's atmosphere ... possibly due to photo-sputtering of the planetary surface". At least in emission yellow astronomy, Mercury is a dwarf gaseous object.
Violet photographs of the planet Venus taken in 1927 “recorded two nebulous bright streaks, or bands, running ... approximately at right angles to the terminator” that may be from the upper atmosphere.
When imaged in visible light (upper left) Venus appears like a gas dwarf rather than a rocky body. The same image result occurs when it is viewed in the ultraviolet (right).
When Venus is viewed by radiation astronomy in addition to ultraviolet astronomy and visual astronomy, it is discovered to have a rocky interior suggesting that it is better understood and studied from the perspective of planetary science as a rocky object.
The Earth's atmosphere is a relatively bright source of gamma rays produced in interactions of ordinary cosmic ray protons with air atoms. In gamma-ray and X-ray astronomy, Earth is a dwarf gaseous object.
At right is an X-ray image of Mars. X-radiation from the Sun excites oxygen atoms in the Martian upper atmosphere, about 120 km above its surface, to emit X-ray fluorescence. A faint X-ray halo that extends out to 7,000 km above the surface of Mars has also been found. The Chandra X-ray Observatory image on the right is the first look at X-rays from Mars.
In X-ray astronomy, Mars is a gas dwarf.
"Four hydrogen (H2) lines have been detected in a spectrum of Mars observed with the Far Ultraviolet Spectroscopic Explorer. ... The line intensities correspond to [an] H2 abundance ... above 140 kilometers on Mars. ... Analysis of [deuterium] fractionation among a few reservoirs of ice, water vapor, and molecular hydrogen on Mars implies that a global ocean more than 30 meters deep was lost since the end of hydrodynamic escape. Only 4% of the initially accreted water remained on the planet at the end of hydrodynamic escape, and initially Mars could have had even more water (as a proportion of mass) than Earth."
Green astronomy indicates Io is a dwarf gaseous object.
At right is an "eerie view of Jupiter's moon Io in eclipse ... acquired by NASA's Galileo spacecraft while the moon was in Jupiter's shadow. Gases above the satellite's surface produced a ghostly glow that could be seen at visible wavelengths (red, green, and violet). The vivid colors, caused by collisions between Io's atmospheric gases and energetic charged particles trapped in Jupiter's magnetic field, had not previously been observed. The green and red emissions are probably produced by mechanisms similar to those in Earth's polar regions that produce the aurora, or northern and southern lights. Bright blue glows mark the sites of dense plumes of volcanic vapor, and may be places where Io is electrically connected to Jupiter."
Saturn is a larger gaseous object from X-ray and ultraviolet astronomy.
Saturn is a gas giant.
Titan like Venus is another gas dwarf when viewed in visible light. Much as with Venus prior to the Space Age, the dense, opaque atmosphere prevented understanding of Titan's surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in the polar regions.
Titan has a mean radius of 2576 ± 2 km.
In optical and visual astronomy, Uranus is a gaseous object in orbit around the Sun.
"Uranus's atmosphere [has a] primary composition of hydrogen and helium [and] contains more "ices" such as water, ammonia, and methane, along with traces of hydrocarbons. ... The helium molar fraction, i.e. the number of helium atoms per molecule of gas, is 0.15 ± 0.03 in the upper troposphere, which corresponds to a mass fraction 0.26 ± 0.05. ... The third most abundant constituent of the Uranian atmosphere is methane (CH4). ... Methane molecules account for 2.3% of the atmosphere by molar fraction below the methane cloud deck at the pressure level of 1.3 bar (130 kPa); this represents about 20 to 30 times the carbon abundance found in the Sun. The mixing ratio is much lower in the upper atmosphere owing to its extremely low temperature, which lowers the saturation level and causes excess methane to freeze out. The abundances of less volatile compounds such as ammonia, water and hydrogen sulfide in the deep atmosphere are poorly known. ... Along with methane, trace amounts of various hydrocarbons are found in the stratosphere of Uranus, which are thought to be produced from methane by photolysis induced by the solar ultraviolet (UV) radiation. They include ethane (C2H6), acetylene (C2H2), methylacetylene (CH3C2H), and diacetylene (C2HC2H). Spectroscopy has also uncovered traces of water vapor, carbon monoxide and carbon dioxide in the upper atmosphere, which can only originate from an external source such as infalling dust and comets."
Neptune's atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, contains a higher proportion of "ices" such as water, ammonia, and methane. Traces of methane in the outermost regions in part account for the planet's blue appearance.
At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium. A trace amount of methane is also present. Prominent absorption bands of methane occur at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue, although Neptune's vivid azure differs from Uranus's milder cyan. Since Neptune's atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune's colour.
A gas detector is a device which detects the presence of various gases within an area or volume.
The combination of nanotechnology and microelectromechanical systems (MEMS) technology allows the production of a hydrogen microsensor that functions properly at room temperature. One type of MEMS-based hydrogen sensor is coated with a film consisting of nanostructured indium(III) oxide (In2O3) and tin oxide (SnO2). A typical configuration for mechanical Pd-based hydrogen sensors is the usage of a free-standing cantilever that is coated with Pd. In the presence of H2, the Pd layer expands and thereby induces a stress that causes the cantilever to bend. Pd-coated nano-mechanical resonators have also been reported in literature, relying on the stress-induced mechanical resonance frequency shift caused by the presence of H2 gas. In this case, the response speed was enhanced through the use of a very thin layer of Pd (20 nm). Moderate heating was presented as a solution to the response impairment observed in humid conditions.
- Gaseous objects have a discernable shape.
- Philip B. Gove (ed.). Webster's Seventh New Collegiate Dictionary. Springfield, Massachusetts 1963: G. & C. Merriam Company. p. 1221.
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