who came up with the solar nebula theory
Immanuel Kant
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Nebular hypothesis The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests that the Solar System is formed from the nebulous material. The theory was developed by Immanuel Kant and published in his "Allgemeine Naturgeschichte und Theorie des Himmels" ("Universal Natural History and Theory of the Heavens"), published in 1755. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the Universe. The widely accepted modern variant of
Nebular hypothesis
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primordial Earth had formed. The formation and evolution of the Solar System bodies occurred in tandem with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disc, which the planets then grow out of in tandem with the star. A nebula contains gas, ice grains and dust (including primordial nuclides). In nebular theory, planetesimals commence forming as particulate matter accrues by cohesive clumping and then by gravity. The assembly of the primordial Earth proceeded for 10–. Earth's atmosphere and oceans were formed
Land
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leaving behind solids collected at the core, with the resulting smaller fragments pushed far out into space and the larger fragments staying behind and accreting into planets. He suggested the Moon was just such a surviving core. In 1960, 1963, and 1978, W. H. McCrea proposed the "protoplanet theory", in which the Sun and planets individually coalesced from matter within the same cloud, with the smaller planets later captured by the Sun's larger gravity. It includes fission in a protoplanetary nebula and there is no solar nebula. Agglomerations of floccules (which are presumed to compose the supersonic turbulence assumed to
History of Solar System formation and evolution hypotheses
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light-years in diameter and has a mass of 30,000 solar masses. The total mass of the Omega Nebula is an estimated 800 solar masses. It is considered one of the brightest and most massive star-forming regions of our galaxy. Its local geometry is similar to the Orion Nebula except that it is viewed edge-on rather than face-on. The open cluster NGC 6618 lies embedded in the nebulosity and causes the gases of the nebula to shine due to radiation from these hot, young stars; however, the actual number of stars in the nebula is much higher - up to 800,
Omega Nebula
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form an acceptable variant. Another convention capitalizes "Earth" when appearing as a name (e.g. "Earth's atmosphere") but writes it in lowercase when preceded by "the" (e.g. "the atmosphere of the earth"). It almost always appears in lowercase in colloquial expressions such as "what on earth are you doing?" The oldest material found in the Solar System is dated to (Bya). By the primordial Earth had formed. The bodies in the Solar System formed and evolved with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten
Earth
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by 0.3 arcsec. Nebula mass is estimated as . Luminosity is estimated to be . The central star is unusual in that it has brightened and faded over a period of 20 years. Its temperature went up by 40,000°C An explanation for this is that it has undergone a helium flash. Stingray Nebula The Stingray Nebula (Hen 3-1357) is the youngest known planetary nebula (PN). The Stingray is located in the direction of the southern constellation Ara (the Altar), and is located 18,000 light-years away. Although it is some 130 times the size of the Solar System, the Stingray Nebula
Stingray Nebula
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The nebula has an overall bubble shape, but with complex filamentary structures. The nebula contains several hundred solar masses of ionised material, plus several thousand more of unionised gas. It is largely interstellar material swept up by winds from the central star, although some material does appear to be enriched with the products of fusion and is likely to come directly from the star. The expansion rate of different portions of the nebula varies from 10 km/s to at least 30 km/s, leading to age estimates of 78,500 - 236,000 years. The nebula has been studied at radio and x-ray
NGC 2359
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the planets and angular momentum distribution provided the magnetic coupling is an acceptable idea, but not explained are twinning, the low mass of Mars and Mercury, and the planetoid belts. It was Alfvén who formulated the concept of frozen-in magnetic field lines. Gerard Kuiper (in 1944) argued, like Ter Haar, that regular eddies would be impossible and postulated that large gravitational instabilities might occur in the solar nebula, forming condensations. In this, the solar nebula could be either co-genetic with the Sun or captured by it. Density distribution would determine what could form: either a planetary system or a stellar
History of Solar System formation and evolution hypotheses
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dense star, with an estimated 0.6 solar mass and 0.028 solar radius, has an apparent magnitude of 17.5. NGC 2440 NGC 2440 is a planetary nebula, one of many in our galaxy. Its central star, HD62166, is possibly the hottest known white dwarf. The nebula is situated in the constellation Puppis. It was discovered by William Herschel on March 4, 1790. He described it as "a beautiful planetary nebula of a considerable degree of brightness, not very well defined." The nebula is located about 1.23 kiloparsecs (3.79×10 m) or about 4,000 light years from the Sun. HD 62166 has an
NGC 2440
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produces. One of the best examples of this is the Crab Nebula, in Taurus. The supernova event was recorded in the year 1054 and is labeled SN 1054. The compact object that was created after the explosion lies in the center of the Crab Nebula and its core is now a neutron star. Still, other nebulae form as planetary nebulae. This is the final stage of a low-mass star's life, like Earth's Sun. Stars with a mass up to 8–10 solar masses evolve into red giants and slowly lose their outer layers during pulsations in their atmospheres. When a star
Nebula
90794
solar abundance, while argon with its higher sublimation temperature was enriched relative to the solar abundance. Together these observations indicate that the interior of Hale–Bopp has always been colder than 35–40 K, but has at some point been warmer than 20 K. Unless the solar nebula was much colder and richer in argon than generally believed, this suggests that the comet formed beyond Neptune in the Kuiper belt region and then migrated outward to the Oort cloud. Comet Hale–Bopp's activity and outgassing were not spread uniformly over its nucleus, but instead came from several specific jets. Observations of the material
Comet Hale–Bopp
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and neon, which were always in the gaseous phase in the nebula. Ices, like water, methane, ammonia, hydrogen sulfide, and carbon dioxide, have melting points up to a few hundred kelvins. They can be found as ices, liquids, or gases in various places in the Solar System, whereas in the nebula they were either in the solid or gaseous phase. Icy substances comprise the majority of the satellites of the giant planets, as well as most of Uranus and Neptune (the so-called "ice giants") and the numerous small objects that lie beyond Neptune's orbit. Together, gases and ices are referred
Solar System
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in 2011 after numerical models indicated that this is more likely to reproduce the current Solar System. The following is a version of the five-planet Nice model that results in a late instability and reproduces a number of aspects of the current Solar System. The early Solar System may have evolved differently, however, with the instability occurring soon after the dissipation of the gas nebula, or with the giant planets beginning in another resonance chain. The Solar System ends its nebula phase with Jupiter, Saturn, and the three ice giants in a 3:2, 3:2, 2:1, 3:2 resonance chain with semi-major
Five-planet Nice model
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Decepticons acquire an Earth satellite, the Solar One, which could harness solar energy, and used it to direct the sun's energy to a small world he had enslaved in a dark nebula off in space, where he was having a massive Transtector constructed for himself. With the Transtector now powered up by the solar energy, Zarak initiated a plan of his own, scheming to blow up Mars and harness the plasma energy released. To stop the Autobots, Zarak boarded his Transtector and travelled to Mars, where combined with it to battle Fortress Maximus, proclaiming that he was no longer Zarak
Scorponok
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lighter fluid "below" the heavier fluid takes the form of larger bubble-like plumes. This process is evident not only in many terrestrial examples, from salt domes to weather inversions, but also in astrophysics and electrohydrodynamics. RT instability structure is also evident in the Crab Nebula, in which the expanding pulsar wind nebula powered by the Crab pulsar is sweeping up ejected material from the supernova explosion 1000 years ago. The RT instability has also recently been discovered in the Sun's outer atmosphere, or solar corona, when a relatively dense solar prominence overlies a less dense plasma bubble. This latter case
Rayleigh–Taylor instability
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the only significant difference between the two bodies is the amplitude of the solar cycle, which appears to be much greater for 18 Scorpii. While the bulk of material in any star is hydrogen and helium, there is a significant variation in the amount of heavier elements (metals). A high proportion of metals in a star correlates to the amount of heavy material initially available in the protoplanetary disk. A smaller amount of metal makes the formation of planets much less likely, under the solar nebula theory of planetary system formation. Any planets that did form around a metal-poor star
Planetary habitability
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was the first to correctly posit that the material in meteor showers is cometary debris. Kirkwood also identified a pattern relating the distances of the planets to their rotation periods, which was called Kirkwood's Law. This discovery earned Kirkwood an international reputation among astronomers; he was dubbed "the American Kepler" by Sears Cook Walker, who claimed that Kirkwood's Law proved the widely held Solar Nebula Theory. The "Law" has since become discredited as new measurements of planetary rotation periods have shown that the pattern doesn't hold. In 1891, at age 77, he became a lecturer in astronomy at Stanford University.
Daniel Kirkwood
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million years, the young Sun's solar wind would have cleared away all the gas and dust in the protoplanetary disc, blowing it into interstellar space, thus ending the growth of the planets. The planets were originally thought to have formed in or near their current orbits. From that a minimum mass of the nebula i.e. the protoplanetary disc, was derived that was necessary to form the planets - the minimum mass solar nebula. It was derived that the nebula mass must have exceeded 3585 times that of the Earth. However, this has been questioned during the last 20 years. Currently,
Formation and evolution of the Solar System
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IC 2149 IC 2149 is a planetary nebula in the constellation of Auriga. It is a small, bright planetary nebula with something to offer in telescopes of most sizes. Visually it has an apparent magnitude of 10.6 and an apparent size of 12 arc seconds and like other objects of its class a nebular filter may help on its observation. Its distance to the Solar System has been estimated to be around 1.1 kiloparsecs, having a total mass of 0.03 solar masses and being thought to have been produced by a low-mass star. Some authors have proposed the planetary nebula
IC 2149
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is O7 + [WR]–type star Calculations suggest the PNN is over one solar mass, from a theoretical initial 5 solar masses. The central Wolf-Rayet star has a radius of (452,000 km). The Cat's Eye Nebula, given in some sources, lies about three thousand light-years from Earth. The Cat's Eye was the first planetary nebula to be observed with a spectroscope by William Huggins on August 29, 1864. Huggins' observations revealed that the nebula's spectrum was non-continuous and made of a few bright emission lines, first indication that planetary nebulae consist of tenuous ionised gas. Spectroscopic observations at these wavelengths are
Cat's Eye Nebula
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young and massive stars inside it. As of 2011, approximately 400 stars of spectral types O and B have been identified within the nebula. Subsequent studies have confirmed not only at least 15 O-type stars but also 3 Luminous Blue Variable/Wolf-Rayet star candidates. They also have calculated the total mass of the stars associated with the Dragonfish nebula as 10 solar masses, a mass only comparable with that of the super star cluster Westerlund 1, the most massive stellar association and the brightest nebula known in our galaxy. Dragonfish nebula The Dragonfish Nebula, as it is known for its appearance
Dragonfish nebula
1711422
outer envelope in a planetary nebula. In stars with masses between 8 and 11 solar masses, the carbon-oxygen core is under degenerate conditions and carbon ignition takes place in a "carbon flash", that lasts just milliseconds and disrupts the stellar core. In the late stages of this nuclear burning they develop a massive stellar wind, which quickly ejects the outer envelope in a planetary nebula leaving behind an O-Ne-Na-Mg white dwarf core of about 1.1 solar masses. The core never reaches high enough temperature for further fusion burning of heavier elements than carbon. Stars with more than 11 solar masses
Carbon-burning process
370820
of stars. As the region that would become the Solar System, known as the pre-solar nebula, collapsed, conservation of angular momentum caused it to rotate faster. The centre, where most of the mass collected, became increasingly hotter than the surrounding disc. As the contracting nebula rotated faster, it began to flatten into a protoplanetary disc with a diameter of roughly 200 AU and a hot, dense protostar at the centre. The planets formed by accretion from this disc, in which dust and gas gravitationally attracted each other, coalescing to form ever larger bodies. Hundreds of protoplanets may have existed in
Solar System
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and apparent magnitude of +4.31. Mu Orionis Aa has 2.1 solar masses, and a radius of 2.9 solar radii and a luminosity 32x that of the Sun. Mu Orionis Ab is a G5V dwarf orbiting Aa at a distance of 0.077 AU, .2x the orbit of mercury. Mu Orionis Ba and Bb are F5V dwarfs with 1.4 solar masses and apparent magnitudes of 6.91. They are separated from eacu other by 0.078 AU. μ Orionis falls just outside an unrelated planetary nebula Abell 12. The bright star makes detecting the faint nebula difficult and it has been nicknamed The Hidden.
Mu Orionis
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study CK Vulpeculae have found the first convincing evidence of radioactive debris outside the Earth's Solar System. The molecule in question is made up of a radioactive isotope of aluminium with 13 protons and 13 neutrons bound together with atoms of fluorine. In the past, a luminous red nova merger, very late thermal pulse, or a diffusion-induced nova have all been suggested but there are problems with all these explanations. An analysis of the structures and isotopic abundances in the remaining nebula using the Atacama Large Millimeter Array (ALMA) in 2018 concluded that the nova and associated nebula were caused
CK Vulpeculae
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atoms in the nebula, causing them to emit radiation themselves producing the emission nebula we see. The mass of the nebula is estimated to be around 10,000 solar masses. A survey of the nebula with the Chandra X-ray Observatory has revealed the presence of numerous new-born stars inside optical Rosette Nebula and studded within a dense molecular cloud. Altogether, approximately 2500 young stars lie in this star-forming complex, including the massive O-type stars HD 46223 and HD 46150, which are primarily responsible for blowing the ionized bubble. Most of the ongoing star-formation activity is occurring in the dense molecular cloud
Rosette Nebula
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and Theory of the Heavens", wherein he argued that gaseous clouds (nebulae) slowly rotate, gradually collapse and flatten due to gravity, eventually forming stars and planets. Pierre-Simon Laplace independently developed and proposed a similar model in 1796 in his "Exposition du systeme du monde". He envisioned that the Sun originally had an extended hot atmosphere throughout the volume of the Solar System. His theory featured a contracting and cooling protosolar cloud—the protosolar nebula. As this cooled and contracted, it flattened and spun more rapidly, throwing off (or shedding) a series of gaseous rings of material; and according to him, the
Nebular hypothesis
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distance from the host star and instead show up as dark silhouettes due to the self-obscuration of cooler dust and gases from the disk itself. Some proplyds show signs of movement from solar irradiance shock waves pushing the proplyds. The Orion Nebula is approximately 1,500 light-years from the Sun with very active star formation. The Orion Nebula and the Sun are in the same spiral arm of the Milky way Galaxy. A proplyd may form new planets and planetesimal systems. Current models show that the metallicity of the star and proplyd, along with the correct planetary system temperature and distance
Proplyd
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not yet condensed in the inner, warmer regions of the nebula, were lost. This fractionation process is the reason why the terrestrial planets and asteroid belt are relatively enriched in heavy elements in respect to the Sun or the gas planets. A certain type of meteorites, CI-chondrites, have a chemical composition that is almost identical to the solar photosphere, except for the abundances of volatiles. Because the Sun contains 99.86% of the mass of the Solar System, they are considered to have the same composition as the solar nebula with the exception of volatile loss and are therefore representative of
Chondritic uniform reservoir
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the material from which the terrestrial planets, including the Earth, were formed. Chondritic uniform reservoir The CHondritic Uniform Reservoir or CHUR is a scientific model in astrophysics and geochemistry for the mean chemical composition of the part of the Solar Nebula from which, during the formation of the Solar System, chondrites formed. This hypothetical chemical reservoir is thought to have been similar in composition to the current photosphere of the Sun. When the Sun formed from its protostar, around 4.56 billion years ago, the solar wind blew all gas particles from the central part of the Solar Nebula. In this
Chondritic uniform reservoir
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Chondritic uniform reservoir The CHondritic Uniform Reservoir or CHUR is a scientific model in astrophysics and geochemistry for the mean chemical composition of the part of the Solar Nebula from which, during the formation of the Solar System, chondrites formed. This hypothetical chemical reservoir is thought to have been similar in composition to the current photosphere of the Sun. When the Sun formed from its protostar, around 4.56 billion years ago, the solar wind blew all gas particles from the central part of the Solar Nebula. In this way most lighter volatiles (e.g. hydrogen, helium, oxygen, carbon dioxide), that had
Chondritic uniform reservoir
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eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs. The history of the Earth can be organized chronologically according to the geologic time scale, which is split into intervals based on stratigraphic analysis. The standard model for the formation of the Solar System (including the Earth) is the solar nebula hypothesis. In this model, the Solar System formed from a large, rotating cloud of interstellar dust and gas called the solar nebula. It was composed of hydrogen
History of Earth
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Cometary knot Cometary knots are structures observed in several nearby planetary nebulae, including the Helix Nebula (NGC 7293), the Ring Nebula (NGC 6720), the Dumbbell Nebula (NGC 6853), the Eskimo Nebula (NGC 2392), and the Retina Nebula (IC 4406). It is believed that they are a common feature of the evolution of planetary nebulae, but can only be resolved in the nearest examples. They are generally larger than the size of the Solar system (i.e. the orbit of Pluto), with masses comparable to that of the Earth. The knots represent "the ionized 'skin' of a dense, dusty molecular globule" that
Cometary knot
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almost twice as large as the difference between O and O. Originally this was interpreted as evidence of incomplete mixing of O-rich material (created and distributed by a large star in a supernova) into the Solar nebula. However, recent measurement of the oxygen-isotope composition of the Solar wind, using samples collected by the Genesis spacecraft, shows that the most O-rich inclusions are close to the bulk composition of the solar system. This implies that Earth, the Moon, Mars and asteroids all formed from O- and O-enriched material. Photochemical dissociation of carbon monoxide in the Solar nebula has been proposed to
Mass-independent fractionation
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Frost line (astrophysics) In astronomy or planetary science, the frost line, also known as the snow line or ice line, is the particular distance in the solar nebula from the central protostar where it is cold enough for volatile compounds such as water, ammonia, methane, carbon dioxide, carbon monoxide to condense into solid ice grains. This condensation temperature depends on the volatile substance and the partial pressure of vapor in the protostar nebula. The actual temperature and distance for the snow line of water ice depend on the physical model used to calculate it and on the theoretical solar nebula
Frost line (astrophysics)
542109
giant molecular clouds, which are generally warmer, produce stars of all masses. These giant molecular clouds have typical densities of 100 particles per cm, diameters of , masses of up to 6 million solar masses (), and an average interior temperature of 10 K. About half the total mass of the galactic ISM is found in molecular clouds and in the Milky Way there are an estimated 6,000 molecular clouds, each with more than . The nearest nebula to the Sun where massive stars are being formed is the Orion nebula, away. However, lower mass star formation is occurring about
Star formation
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they produce small fragments that occasionally fall on Earth. These rocks are called meteorites and provide information about the primordial solar nebula. Most of these fragments have the size of sand grains. They burn up in the Earth's atmosphere, causing them to glow like meteors. A comet is a small Solar System body that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail—both primarily from the effects of solar radiation upon the comet's nucleus, which itself is a minor body composed of rock, dust, and ice. The Kuiper belt, sometimes called the Edgeworth–Kuiper belt,
Geology of solar terrestrial planets
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Excluding the tails, they are (very approximately) the size of the Solar system, while each of the cusp knots are optically thick due to Lyc photons from the PNN. There are more than 20,000 cometary knots estimated to be in the Helix Nebula. The excitation temperature varies across the Helix nebula. The rotational-vibrational temperature ranges from 1800 K in a cometary knot located in the inner region of the nebula are about 2.5′ (arcmin) from the central PNN, calculated at about 900 K in the outer region at the distance of 5.6′. Helix Nebula The Helix Nebula, also known as
Helix Nebula
5473584
they expand and cool, and do so even in gas containing more oxygen than carbon, a surprising carbon chemistry made possible by the intense radioactive environment of supernovae. This special example of dust formation has merited specific review. Planetary disk formation of precursor molecules was determined, in large part, by the temperature of the solar nebula. Since the temperature of the solar nebula decreased with heliocentric distance, scientists can infer a dust grain's origin(s) with knowledge of the grain's materials. Some materials could only have been formed at high temperatures, while other grain materials could only have been formed at
Cosmic dust
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wind of the central star as it evolved along the asymptotic giant branch. The nebula is arranged in three concentric shells, with the outermost shell being about 20–30% larger than the inner shell. The owl-like appearance of the nebula is the result of an inner shell that is not circularly symmetric, but instead forms a barrel-like structure aligned at an angle of 45° to the line of sight. The nebula holds about 0.13 solar masses of matter, including hydrogen, helium, nitrogen, oxygen, and sulfur; all with a density of less than 100 particles per cubic centimeter. Its outer radius is
Owl Nebula
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formed at different times and places in the solar nebula and before the solar nebula's formation. Examples of embedded elements in cosmic dust are GEMS, chondrules, and CAIs. The arrows in the adjacent diagram show one possible path from a collected interplanetary dust particle back to the early stages of the solar nebula. We can follow the trail to the right in the diagram to the IDPs that contain the most volatile and primitive elements. The trail takes us first from interplanetary dust particles to chondritic interplanetary dust particles. Planetary scientists classify chondritic IDPs in terms of their diminishing degree
Cosmic dust
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melting in basalt. Earth is often described as having had three atmospheres. The first atmosphere, captured from the solar nebula, was composed of light (atmophile) elements from the solar nebula, mostly hydrogen and helium. A combination of the solar wind and Earth's heat would have driven off this atmosphere, as a result of which the atmosphere is now depleted of these elements compared to cosmic abundances. After the impact which created the moon, the molten Earth released volatile gases; and later more gases were released by volcanoes, completing a second atmosphere rich in greenhouse gases but poor in oxygen. Finally,
History of Earth
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pyrimidine, found in meteorites. Pyrimidine, like polycyclic aromatic hydrocarbons (PAHs), the most carbon-rich chemical found in the Universe, may have been formed in red giants or in interstellar dust and gas clouds, according to the scientists. The Solar System has its own interplanetary dust cloud, as do extrasolar systems. There are different types of nebulae with different physical causes and processes: diffuse nebula, infrared (IR) reflection nebula, supernova remnant, molecular cloud, HII regions, photodissociation regions, and dark nebula. Distinctions between those types of nebula are that different radiation processes are at work. For example, H II regions, like the Orion
Cosmic dust
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Stingray Nebula The Stingray Nebula (Hen 3-1357) is the youngest known planetary nebula (PN). The Stingray is located in the direction of the southern constellation Ara (the Altar), and is located 18,000 light-years away. Although it is some 130 times the size of the Solar System, the Stingray Nebula is only about 1/10 the size of most other known planetary nebulae. Forty years ago it was still a protoplanetary nebula in which the gas had not yet become hot and ionized. In a "Nature" article, Bobrowsky et al. described how the Hubble observations revealed a 17th-magnitude companion to the Stingray's
Stingray Nebula
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and 19.5 light years and a collective mass of . This cluster began to break apart between 135 million and 535 million years after formation. Several simulations of our young Sun interacting with close-passing stars over the first 100 million years of its life produce anomalous orbits observed in the outer Solar System, such as detached objects. Because of the conservation of angular momentum, the nebula spun faster as it collapsed. As the material within the nebula condensed, the atoms within it began to collide with increasing frequency, converting their kinetic energy into heat. The centre, where most of the
Formation and evolution of the Solar System
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distance to Wolf–Lundmark–Melotte (approximately 930,000 parsecs). Additionally, in "Second Stage Lensmen" multiple references are made to the spiral arms of Lundmark's Nebula. Wolf–Lundmark–Melotte does not possess such structures. At the time of writing of these books, the name of Lundmark was associated with such classifications and Smith may have elected to use this as a "believable" name for an entirely fictional galaxy. At the time the "Lensman" series was written, most astronomers favored the tidal theory of Solar System formation, which required that planets be formed by the close approach of another star. In order to produce the massive numbers
Wolf–Lundmark–Melotte
7865136
model: The radial position of the condensation/evaporation front varies over time, as the nebula evolves. Occasionally, the term "snow line" is also used to represent the present distance at which water ice can be stable (even under direct sunlight). This "current snow line" distance is different from the "formation snow line" distance during the formation of the Solar System, and approximately equals 5 AU. The reason for the difference is that during the formation of the Solar System, the solar nebula was an opaque cloud where temperatures were lower close to the Sun, and the Sun itself was less energetic.
Frost line (astrophysics)
4814510
gas from the solar nebula. Differentiation between these two classes of planetesimals arise due to the frost line of the solar nebula. Meteorites contain a record of accretion and impacts during all stages of asteroid origin and evolution; however, the mechanism of asteroid accretion and growth is not well understood. Evidence suggests the main growth of asteroids can result from gas-assisted accretion of chondrules, which are millimeter-sized spherules that form as molten (or partially molten) droplets in space before being accreted to their parent asteroids. In the inner Solar System, chondrules appear to have been crucial for initiating accretion. The
Accretion (astrophysics)
5473585
much lower temperatures. The materials in a single interplanetary dust particle often show that the grain elements formed in different locations and at different times in the solar nebula. Most of the matter present in the original solar nebula has since disappeared; drawn into the Sun, expelled into interstellar space, or reprocessed, for example, as part of the planets, asteroids or comets. Due to their highly processed nature, IDPs (interplanetary dust particles) are fine-grained mixtures of thousands to millions of mineral grains and amorphous components. We can picture an IDP as a "matrix" of material with embedded elements which were
Cosmic dust
13861938
that our Sun will produce will be similar to this one, but smaller. IC 2149 IC 2149 is a planetary nebula in the constellation of Auriga. It is a small, bright planetary nebula with something to offer in telescopes of most sizes. Visually it has an apparent magnitude of 10.6 and an apparent size of 12 arc seconds and like other objects of its class a nebular filter may help on its observation. Its distance to the Solar System has been estimated to be around 1.1 kiloparsecs, having a total mass of 0.03 solar masses and being thought to have
IC 2149
446125
of 13 and 46 days and masses 8.3 and 10.1 times that of Earth, respectively. The discovery of a binary brown dwarf system named Luhman 16 only 6.6 light-years away, the third-closest system to the Solar System, was announced on 11 March 2013. Of the deep-sky objects of interest in Vela is a planetary nebula known as the NGC 3132, nicknamed the 'Eight-Burst Nebula' or 'Southern Ring Nebula' (see accompanying photo). It lies on the border of the constellation with Antlia. NGC 2899 is an unusual red-hued example. This constellation has 32 more planetary nebulae. The Gum Nebula is a
Vela (constellation)
3175565
the Sun making it one of the most luminous stars in the Milky Way. Pistol Nebula The Pistol Nebula is located in the constellation Sagittarius. It surrounds one of the most luminous stars known, the Pistol Star. Both are located 25,000 light years away from Earth in the Quintuplet cluster, near the center of the Milky Way galaxy. The nebula contains approximately 9.3 solar masses worth of ionized gas that was ejected by the star several thousand years ago. The nebula was named in the 1980s for its shape as seen in low resolution images that were available at the
Pistol Nebula
3175564
Pistol Nebula The Pistol Nebula is located in the constellation Sagittarius. It surrounds one of the most luminous stars known, the Pistol Star. Both are located 25,000 light years away from Earth in the Quintuplet cluster, near the center of the Milky Way galaxy. The nebula contains approximately 9.3 solar masses worth of ionized gas that was ejected by the star several thousand years ago. The nebula was named in the 1980s for its shape as seen in low resolution images that were available at the time. The Pistol Star, a luminous blue variable is 1.6 million times brighter than
Pistol Nebula
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a luminosity of about 20 solar luminosities and a visual magnitude of 11.5. This strong ultraviolet irradiation from the central star creates the characteristic fluorescent green tint of the nebula via the radiation of doubly ionized oxygen. The object overall has a visual magnitude of 8 and a radial velocity of 28 miles per second towards the Earth. The nebula is 1 degree west of the star Nu Aquarii. The central portion measures 25″ × 17″, while the outer shell extends to 41″ × 35″. The object is on many "best of" observing lists. Saturn Nebula The Saturn Nebula or
Saturn Nebula
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again. Sulu agreed, but on the way out of the nebula they were in, came up with a plan to disable the Klingon ship by igniting the sirillium that was also present in that nebula. After this succeeded, they set course once more for Qo'noS, before being attacked again by three Klingon battlecruisers – an attack that killed Lieutenant Dimitri Valtane. As Tuvok watched Valtane die, the memory appeared once more, and in Sickbay, the neural engrams destabilize, preventing the meld from being broken. On the "Excelsior", Sulu could suddenly see Janeway, who was supposed to merely be an observer.
Flashback (Star Trek: Voyager)
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a binary star formed of an O3.5V star plus an O7.5V companion. This star has a mass of roughly 80 solar masses, and a luminosity up to 1 million times that of the Sun. The cluster's age has been estimated to be 1–2 million years. The descriptive names reflect impressions of the shape of the central pillar rising from the southeast into the central luminous area. The name "Star Queen Nebula" was introduced by Robert Burnham, Jr., reflecting his characterization of the central pillar as the Star Queen shown in silhouette. Images taken by Jeff Hester and Paul Scowen using
Eagle Nebula
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of interaction between rapid bi-polar outflow and the gas that was ejected when the star was passing through its asymptotic giant branch phase. The lobes are inclined about 24° to the line of sight. The energy being radiated from the nebula consists of scattered light from the star at the core, light being emitted from a compact HII region surrounding the star, and energy from the shock-excited gas in the lobes. The core star is believed to be of spectral class B0 and has 12,200 times the solar luminosity. Westbrook Nebula Westbrook Nebula (CRL 618) is an aspherical protoplanetary nebula
Westbrook Nebula
867206
that the diffuse blue region is predominantly produced by synchrotron radiation, which is radiation given off by the curving motion of electrons in a magnetic field. The radiation corresponded to electrons moving at speeds up to half the speed of light. Three years later the theory was confirmed by observations. In the 1960s it was found that the source of the curved paths of the electrons was the strong magnetic field produced by a neutron star at the centre of the nebula. Even though the Crab Nebula is the focus of much attention among astronomers, its distance remains an open
Crab Nebula
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hydrogen clouds of the Orion Nebula. Each bullet is ten times the diameter of Pluto's orbit and tipped with iron atoms glowing in the infra-red. They were probably formed one thousand years ago from an unknown violent event. Interstellar clouds like the Orion Nebula are found throughout galaxies such as the Milky Way. They begin as gravitationally bound blobs of cold, neutral hydrogen, intermixed with traces of other elements. The cloud can contain hundreds of thousands of solar masses and extend for hundreds of light years. The tiny force of gravity that could compel the cloud to collapse is counterbalanced
Orion Nebula
4814514
its wake a population of dynamically stable objects that could never be affected by its orbit (the Kuiper belt proper), and a population whose perihelia are close enough that Neptune can still disturb them as it travels around the Sun (the scattered disk). Because the scattered disk is dynamically active and the Kuiper belt relatively dynamically stable, the scattered disk is now seen as the most likely point of origin for periodic comets. The classic Oort cloud theory states that the Oort cloud, a sphere measuring about in radius, formed at the same time as the solar nebula and occasionally
Accretion (astrophysics)
2547940
Starflight 2: Trade Routes of the Cloud Nebula Starflight 2: Trade Routes of the Cloud Nebula is a 1989 science fiction video game developed by Binary Systems and published by Electronic Arts as the sequel to the successful "Starflight". It features a combination of space exploration, role-playing and strategy within a futuristic setting. The player commands a spaceship capable of traveling to the game world's 150 solar systems, communicating with or attacking other spaceships, and landing on planetary surfaces which may be explored with a manned rover for plot clues, minerals and alien lifeforms. Game mechanics and the overall look
Starflight 2: Trade Routes of the Cloud Nebula
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in 1993. In November 2011, Electronic Arts re-released a compilation of both "Starflight" games through GOG.com. Starflight 2: Trade Routes of the Cloud Nebula Starflight 2: Trade Routes of the Cloud Nebula is a 1989 science fiction video game developed by Binary Systems and published by Electronic Arts as the sequel to the successful "Starflight". It features a combination of space exploration, role-playing and strategy within a futuristic setting. The player commands a spaceship capable of traveling to the game world's 150 solar systems, communicating with or attacking other spaceships, and landing on planetary surfaces which may be explored with
Starflight 2: Trade Routes of the Cloud Nebula
2028786
Reynolds determined, through the analysis of short-lived nuclides within meteorites, that the elements of the Solar System were formed before the Solar System itself which began to establish a timeline of the processes of the early Solar System. Meteorites are one of the most important tools that cosmochemists have for studying the chemical nature of the Solar System. Many meteorites come from material that is as old as the Solar System itself, and thus provide scientists with a record from the early solar nebula. Carbonaceous chondrites are especially primitive; that is they have retained many of their chemical properties since
Cosmochemistry
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Milky Way Galaxy, though approximately 1,300 light years from the solar system. This makes the Orion Nebula one of the closest HII regions to Earth, a mass of hydrogen that has been ionized by nearby, hot, young stars. Regions like this are called stellar nurseries, nurturing the birth of multiple young stars such as the Orion Nebula Star Cluster. These stars are a significant feature of the Sword asterism. "42 Orionis," also called c Ori, is a B1V magnitude star in the northern half of the Orion nebula. "Theta Orionis" has a more central position in the nebula, and is
Orion's Sword
2639037
illuminated by T Tauri, and thus also varies in brightness. The nebula NGC 1554 was likewise associated with T Tauri and was observed in 1868 by Otto Wilhelm von Struve, but soon disappeared or perhaps never existed, and is known as "Struve's Lost Nebula". The T Tauri wind, so named because this young star is currently in this stage, is a phase of stellar development between the accretion of material from the slowing rotating material of a solar nebula and the ignition of the hydrogen that has agglomerated into the protostar. A protostar is the denser parts of a cloud
T Tauri
13834903
NGC 1360 NGC 1360, also known as the Robin's Egg Nebula, is a planetary nebula in the constellation of Fornax. It was identified as a planetary nebula due to its strong radiation in the OIII (oxygen) bands. Reddish matter, believed to have been ejected from the original star before its final collapse, is visible in images. It is slightly fainter than IC 2003. In 2017 it was discovered the central source was a long period double degenerate in a 142-day orbit, with masses of 0.555 (Central Star) and 0.70 (White Dwarf Companion) Solar Masses respectively. Although it was suspected to
NGC 1360
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and nitrogen-15 (N), which is indicative of their retention of an interstellar heritage. The chemical composition of comets should reflect both the conditions in the outer solar nebula some 4.5 × 10 ayr, and the nature of the natal interstellar cloud from which the Solar system was formed. While comets retain a strong signature of their ultimate interstellar origins, significant processing must have occurred in the protosolar nebula. Early models of coma chemistry showed that reactions can occur rapidly in the inner coma, where the most important reactions are proton transfer reactions. Such reactions can potentially cycle deuterium between the
Theoretical astronomy
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Ray Reynolds and Chris McKay. He maintained that, because of its rockier composition, Pluto formed in a carbon monoxide-rich outer solar nebula rather than a planetary nebula surrounding the dwarf planet. Simonelli and Ray Reynolds suggested that Pluto's density is a result of a collision which also created its largest moon, Charon. From 1991, after returning to Cornell, Simonelli led a team studying smaller bodies in the Solar System, for example the satellites Io, Phoebe, Thebe, Amalthea, Metis and Phobos, and the asteroids 243 Ida, 951 Gaspra and 52 Europa. His expertise in planning observations and command sequences for the
Damon Simonelli
11868602
visible to the naked eye. The first planetary nebula discovered was the Dumbbell Nebula in the constellation of Vulpecula, observed by Charles Messier in 1764 and listed as M27 in his catalogue of nebulous objects. To early observers with low-resolution telescopes, M27 and subsequently discovered planetary nebulae somewhat resembled the gas giants, and William Herschel, discoverer of Uranus, eventually coined the term 'planetary nebula' for them, although, as we now know, they are very different from planets. The central stars of planetary nebulae are very hot. Their luminosity, though, is very low, implying that they must be very small. Only
History of Solar System formation and evolution hypotheses
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Hertzsprung-Russell diagram. These rings are very evenly spaced, suggesting that the mechanism responsible for their formation ejected them at very regular intervals and at very similar speeds. The total mass of the rings is about 0.1 solar masses. The pulsations that formed the rings probably started 15,000 years ago and ceased about years ago, when the formation of the bright central part began (see above). Further out, a large faint halo extends to large distances from the star. The halo again predates the formation of the main nebula. The mass of the halo is estimated as 0.26–0.92 solar masses. Cat's
Cat's Eye Nebula
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Impacts on the parent body are recorded by impact-breccias and high-pressure mineral phases (e.g. coesite, akimotoite, majorite, ringwoodite, stishovite, wadsleyite). Water bearing minerals are an indicator for hydrothermal activity on the parent body (e.g. clay minerals). Radiometric methods can be used to date different stages of the history of a meteorite. Condensation from the solar nebula is recorded by calcium–aluminium-rich inclusions and chondrules. These can be dated by using radionuclides that were present in the solar nebula (e.g. Al/Mg, Mn/Cr, U/Pb, I/Xe). After the condensed material accretes to planetesimals of sufficient size melting and differentiation take place. These processes can
Meteoritics
1615212
this effect is due to Leó Szilárd and Thomas A. Chalmers. Radioactive primordial nuclides found in the Earth are residues from ancient supernova explosions that occurred before the formation of the solar system. They are the fraction of radionuclides that survived from that time, through the formation of the primordial solar nebula, through planet accretion, and up to the present time. The naturally occurring short-lived radiogenic radionuclides found in today's rocks, are the daughters of those radioactive primordial nuclides. Another minor source of naturally occurring radioactive nuclides are cosmogenic nuclides, that are formed by cosmic ray bombardment of material in
Radioactive decay
615432
there would probably have been simple hydrides such as those now found in gas giants like Jupiter and Saturn, notably water vapor, methane, and ammonia. As the solar nebula dissipated, the gases would have escaped, partly driven off by the solar wind. The next atmosphere, consisting largely of nitrogen, carbon dioxide, and inert gases, was produced by outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids. A major part of carbon dioxide emissions were soon dissolved in water and built up carbonate sediments. Water-related sediments have been found dating from as early
Paleoclimatology
3775912
NGC 3603 NGC 3603 is a nebula situated in the Carina spiral arm of the Milky Way around 20,000 light-years away from the Solar System. It is a massive HII region containing a very compact open cluster (probably a super star cluster) HD 97950. NGC 3603 was observed by John Herschel on the 14th of March 1834 during his visit to South Africa, who remarked that it was "a very remarkable object...perhaps a globular cluster". Herschel catalogued it as nebula 3334 in his "Results of Astronomical Observations made at the Cape of Good Hope", published in 1847. In 1864 the
NGC 3603
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Their size, radius, and density are all similar. Terrestrial planets have numerous similarities to plutoids (objects like Pluto), which also have a solid surface, but are primarily composed of icy materials. During the formation of the Solar System, there were probably many more (planetesimals), but they have all merged with or been destroyed by the four remaining worlds in the solar nebula. The terrestrial planets all have roughly the same structure: a central metallic core, mostly iron, with a surrounding silicate mantle. The Moon is similar, but lacks a substantial iron core. Three of the four solar terrestrial planets (Venus,
Geology of solar terrestrial planets
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energy from the fusion of hydrogen into helium in their cores. The Sun remains a main-sequence star today. The various planets are thought to have formed from the solar nebula, the disc-shaped cloud of gas and dust left over from the Sun's formation. The currently accepted method by which the planets formed is accretion, in which the planets began as dust grains in orbit around the central protostar. Through direct contact, these grains formed into clumps up to 200 metres in diameter, which in turn collided to form larger bodies (planetesimals) of ~10 kilometres (km) in size. These gradually increased
Formation and evolution of the Solar System
1561026
same as knowing the elemental and isotopic composition of the solar nebula. The data can be used to model how planets and other Solar System objects formed, and then extend those results to understanding stellar evolution and the formation of planetary systems elsewhere in the universe. Clearly, the ideal sample collection option would be to send a spacecraft to the Sun itself and collect some solar plasma; however, that is difficult because of the intense heat of the Sun's superheated gases, as well as the dynamic electromagnetic environment of the solar corona, whose flares regularly interfere with the electronics of
Genesis (spacecraft)
449560
sidereal day has increased by 6.5 minutes in that time span. Because of the retrograde rotation, the length of a solar day on Venus is significantly shorter than the sidereal day, at 116.75 Earth days (making the Venusian solar day shorter than Mercury's 176 Earth days). One Venusian year is about 1.92 Venusian solar days. To an observer on the surface of Venus, the Sun would rise in the west and set in the east, although Venus's opaque clouds prevent observing the Sun from the planet's surface. Venus may have formed from the solar nebula with a different rotation period
Venus
588156
from the original solar nebula. The Solar System has four terrestrial planets: Mercury, Venus, Earth, and Mars. Only one terrestrial planet, Earth, is known to have an active hydrosphere. During the formation of the Solar System, there were probably many more terrestrial planetesimals, but most merged with or were ejected by the four terrestrial planets. Dwarf planets, such as Ceres, Pluto and Eris, and small Solar System bodies are similar to terrestrial planets in the fact that they do have a solid surface, but are, on average, composed of more icy materials (Ceres, Pluto and Eris have densities of 2.17,
Terrestrial planet
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Westbrook Nebula Westbrook Nebula (CRL 618) is an aspherical protoplanetary nebula which is located in the constellation Auriga. It is being formed by a star that has passed through the red giant phase and has ceased nuclear fusion at its core. This star is concealed at the center of the nebula, and is ejecting gas and dust at velocities of up to 200 km/s. The nebula is named after William E. Westbrook, who died in 1975. This nebula began to form about 200 years ago, and primarily consists of molecular gas. The outer part of the nebula is the result
Westbrook Nebula
867217
amount of light emitted, and calculating the mass required, given the measured temperature and density of the nebula. Estimates range from about , with being the generally accepted value. The neutron star mass is estimated to be between . The predominant theory to account for the missing mass of the Crab Nebula is that a substantial proportion of the mass of the progenitor was carried away before the supernova explosion in a fast stellar wind, a phenomenon commonly seen in Wolf-Rayet stars. However, this would have created a shell around the nebula. Although attempts have been made at several wavelengths
Crab Nebula
8966698
Bipolar nebula A bipolar nebula is a distinctive nebular formation characterized by an axially symmetric bi-lobed appearance. Many, but not all, planetary nebulae exhibit an observed bipolar structure. It may be that the two types of nebulae are directly related, one preceding or superseding the other in the evolution of the nebula. Though the exact causes of this nebular structure are not known, it may be related to the physical process known as bipolar outflow in which a star ejects highly energetic streams of outflow along both poles. One theory states that these outflows collide with material surrounding the star
Bipolar nebula
2088500
on the leading edge of the LMC where ram pressure stripping, and the compression of the interstellar medium likely resulting from this, is at a maximum. 30 Doradus has at its centre the star cluster NGC 2070 which includes the compact concentration of stars known as R136 that produces most of the energy that makes the nebula visible. The estimated mass of the cluster is 450,000 solar masses, suggesting it will likely become a globular cluster in the future. In addition to NGC 2070, the Tarantula Nebula contains a number of other star clusters including the much older Hodge 301.
Tarantula Nebula
5558167
were an offshoot of the Pala dynasty of Gauda, but this theory has been totally rejected now. Another theory identifies the dynasty's founder Chandradeva as the Kannauj Rashtrakuta scion Chandra, but this theory is contradicted by historical evidence. For example, the Rashtrakutas of Kannauj claimed origin from the legendary solar dynasty. On the other hand, the Gahadavala inscriptions state they gained power "after" the destruction of the solar and the lunar dynasties. Moreover, Kumaradevi, the queen of the Gahadavala ruler Govindachandra came from a Rashtrakuta branch. Her Sarnath inscription mentions the Gahadavalas and the Rashtrakutas as two distinct families, and
Gahadavala
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primordial ×1.6 SMOW ratio suggests that ~ of has been lost to space via solar wind stripping. The cometary and asteroidal delivery of water to accreting Earth and Mars has significant caveats, even though it is favored by D/H isotopic ratios. Key issues include: An alternative to the cometary and asteroidal delivery of HO would be the accretion via physisorption during the formation of the terrestrial planets in the solar nebula. This would be consistent with the thermodynamic estimate of around two Earth masses of water vapor within 3AU of the solar accretionary disk, which would exceed by a factor
Water on terrestrial planets of the Solar System
18958718
Solar activity and climate Solar irradiance variation has been a main driver of climate change over the billion years of geologic time, but its role in the recent warming has been found to be insignificant. Earth formed around 4.54 billion years ago by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere, which contained almost no oxygen and would have been toxic to humans and most modern life. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. Over time, the planet cooled and formed a solid crust, eventually
Solar activity and climate
370814
largely of materials with lower melting points. The boundary in the Solar System beyond which those volatile substances could condense is known as the frost line, and it lies at roughly 5 AU from the Sun. The objects of the inner Solar System are composed mostly of rock, the collective name for compounds with high melting points, such as silicates, iron or nickel, that remained solid under almost all conditions in the protoplanetary nebula. Jupiter and Saturn are composed mainly of gases, the astronomical term for materials with extremely low melting points and high vapour pressure, such as hydrogen, helium,
Solar System
5408693
the age, formation process and subsequent history of the material forming the meteorite. This provides information on the history of the Solar System, how it formed and evolved, and the process of planet formation. Before the documentation of L'Aigle it was generally believed that meteorites were a type of superstition and those who claimed to see them fall from space were lying. In 1960 John Reynolds discovered that some meteorites have an excess of Xe, a result of the presence of I in the solar nebula. The presence or absence of certain minerals is indicative of physical and chemical processes.
Meteoritics
15587032
a man-made component of some types of concrete, forms under low pressure at a temperature of at least . These conditions of high temperature and low pressure are consistent with a hypothesis that the krotite grains found in the meteorite formed as high-temperature condensates from the solar nebula from which the solar system formed, approximately 4.6 billion years ago. Thus, they are likely to be among the earliest minerals formed in the solar system. The CAI containing the krotite was said to resemble a "cracked egg" because its rim was crosscut by cracks filled with iron and aluminum hydroxides. Researchers
Krotite
7423620
about 5 inch aperture can resolve six stars under good seeing conditions. The Trapezium is a relatively young cluster that has formed directly out of the parent nebula. The five brightest stars are on the order of 15-30 solar masses in size. They are within a diameter of 1.5 light-years of each other and are responsible for much of the illumination of the surrounding nebula. The Trapezium may be a sub-component of the larger Orion Nebula Cluster, a grouping of about 2,000 stars within a diameter of 20 light-years. The Trapezium is most readily identifiable by the asterism of four
Trapezium Cluster
17778302
the spectroscopic variations indicates large-scale structures within the stellar wind. 68 Cygni is known to be surrounded by a ring-shaped nebula, named S 119. Although it was originally proposed that this nebula was formed from 68 Cygni's stellar wind, it now appears that the nebula is simply a Strömgren sphere that is being ionized by 68 Cygni. Instead, the stellar wind is likely, due to the star's high velocity through space, forming a bow shock. The mass of the star is likely to be around 26 solar masses, according to a 2011 study by Ducati, Penteado, and Turcati. However, due
68 Cygni
8373966
The cloud was about 20 parsec (65 light years) across, while the fragments were roughly 1 parsec (three and a quarter light-years) across. The further collapse of the fragments led to the formation of dense cores 0.01–0.1 pc (2,000–20,000 AU) in size. One of these collapsing fragments (known as the "pre-solar nebula") formed what became the Solar System. The composition of this region with a mass just over that of the Sun () was about the same as that of the Sun today, with hydrogen, along with helium and trace amounts of lithium produced by Big Bang nucleosynthesis, forming about
Formation and evolution of the Solar System
20555698
figures. Such signs are called solar signs. The researcher analysed the location of those solar signs and came to a conclusion that they were put on rock surfaces in accordance with a certain system. However, not all researchers agree with the theory about the handmade origin of “solar signs”. In particular, a professor of geology Bohdan Ridush proved that those are natural reliefs of petrified sponges, which appeared in the process of sandstone weathering. Handmade petroglyphs also survived in Tustan. Individual images of animals are particularly interesting: a wolf chasing an elk, a horse and a rider. During archeological excavations
Fortress of Tustan
18588490
a study of why the nebula was not regular was conducted, resolving the previously thought single star into a double star. The two white dwarf stars forming the binary star system at the heart of the nebula orbit each other with a period of about 4 hours. The two stars have a combined mass of about 1.8 solar masses, with each star being slightly less massive than the Sun. As of 2015, they are the most massive binary double white dwarf star system known. The pair are expected to merge into a single star in about 700 million years, whereupon
Hen 2-428
4814497
and in diameter. Over millions of years, giant molecular clouds are prone to collapse and fragmentation. These fragments then form small, dense cores, which in turn collapse into stars. The cores range in mass from a fraction to several times that of the Sun and are called protostellar (protosolar) nebulae. They possess diameters of and a particle number density of roughly . Compare it with the particle number density of the air at the sea level—. The initial collapse of a solar-mass protostellar nebula takes around 100,000 years. Every nebula begins with a certain amount of angular momentum. Gas in
Accretion (astrophysics)
4563607
Sherwood Smith Sherwood Smith (born 1951) is an American fantasy and science fiction writer for young adults as well as adults. Smith is a Nebula Award finalist and a longtime writing group organizer and participant. Smith's works include the YA novel "Crown Duel". Smith also collaborated with Dave Trowbridge in writing the "Exordium" series and with Andre Norton in writing two of the books in the "Solar Queen" universe. In 2001, her short story "Mom and Dad at the Home Front" was a finalist for the Nebula Award for Best Short Story. Smith's children's books have made it on many
Sherwood Smith
19371270
Orion Nebula . She studied observations of double stars using a 38 cm astrograph . She was one of the leaders of the expedition which monitored the solar corona at various points of the USSR during the total solar eclipse on June 19, 1936. She was involved in the processing of observations made with a view to establishing the structure of the corona and the fact of its rotation. She was one of the leaders of observations during total solar eclipses of 1941, 1945, 1952 and 1954 participating in the processing of observations. She studied the fine structure of the
Yevgenia Bugoslavskaya
8308217
STACEE The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), is a gamma ray detector located near Albuquerque, New Mexico. Observations with STACEE began in October 2001 and concluded in June 2007. Gamma rays were observed from objects such as the Crab Nebula, a supernova remnant, and Markarian 421, a blazar. STACEE uses the heliostats and space on the receiver tower of the National Solar Thermal Test Facility (NSTTF) operated by the Sandia National Laboratories on the grounds of the Kirtland Air Force Base. In the daytime, the facility is used for solar energy research. During the night STACEE uses the
STACEE
8374029
in any meaningful sense, will cease to exist. The time frame of the Solar System's formation has been determined using radiometric dating. Scientists estimate that the Solar System is 4.6 billion years old. The oldest known mineral grains on Earth are approximately 4.4 billion years old. Rocks this old are rare, as Earth's surface is constantly being reshaped by erosion, volcanism, and plate tectonics. To estimate the age of the Solar System, scientists use meteorites, which were formed during the early condensation of the solar nebula. Almost all meteorites (see the Canyon Diablo meteorite) are found to have an age
Formation and evolution of the Solar System
1561040
asteroid belt. Nitrogen was a key target element because the extent and origin of its isotopic variations in Solar System materials remain unknown. Target material showed that implanted solar wind nitrogen has a N/N ratio of 2.18 × 10 (that is, ≈40% poorer in N relative to the terrestrial atmosphere). The N/N ratio of the protosolar nebula was 2.27 × 10, which is the lowest N/N ratio known for Solar System objects. This result demonstrates the extreme nitrogen isotopic heterogeneity of the nascent Solar System and accounts for the N-depleted components observed in Solar System reservoirs. A 16-member NASA Mishap
Genesis (spacecraft)
6499526
a depressurization in the observation lounge. The crew investigate and find all the furniture piled in one corner of the room. Data is visiting D'Sora, but she seems unhappy and he is acting erratically in order to find an appropriate response to make her happy. It becomes evident to the crew that the nebula is causing distortions in space; Picard orders the ship into warp to leave the nebula as quickly as possible but this speeds up the distortions. Whilst investigating them, Lieutenant Van Mayter (Georgina Shore) is killed when a distortion embeds her into the deck. Data discovers that
In Theory (Star Trek: The Next Generation)