Centaur (minor planet) Centaurs are small Solar System bodies with a semi-major axis between those of the outer planets. They have unstable orbits that cross or have crossed the orbits of one or more of the giant planets, and have dynamic lifetimes of a few million years. Centaurs typically behave with characteristics of both asteroids and comets. They are named after the mythological beings that were a mixture of horse and human, centaurs. The first centaur to be discovered, under the definition of the Jet Propulsion Laboratory (JPL) and the one used here, was 944 Hidalgo in 1920. However, different institutions have different criteria for classifying borderline objects, based on particular values of their orbital elements: Centaurs with measured diameters listed as possible dwarf planets according to Mike Brown's website include 10199 Chariklo, 2060 Chiron, and 54598 Bienor. The diagram at right illustrates the orbits of all known centaurs in relation to the orbits of the planets.
Terrestrial planet Structure Solar terrestrial planets Relative masses of the terrestrial planets of the Solar System, including the Moon 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. Density trends The uncompressed density of a terrestrial planet is the average density its materials would have at zero pressure. The densities of the solar terrestrial planets, the Moon, and the three largest asteroids are shown below. The main exception to this rule is the density of the Moon, which probably owes its lesser density to its unusual origin. It is unknown whether extrasolar terrestrial planets in general will also follow this trend. Extrasolar terrestrial planets During the early 1990s, the first extrasolar planets were discovered orbiting the pulsar PSR B1257+12, with masses of 0.02, 4.3, and 3.9 times that of Earth's, by pulsar timing. Frequency Types
List of minor planets This is a list of numbered minor planets in the Solar System, in numerical order. The following are lists of minor planets by physical properties, orbital properties, or discovery circumstances: Numbering and naming conventions Total, numbered, and named minor planets from 1995 to 2014. After discovery, asteroids generally receive a provisional designation (such as "1989 AC"), then a sequential number (such as 4179), and finally (optionally) a name (such as "Toutatis"), in that order. In modern times, an asteroid receives a sequential number only after it has been observed several times over at least 4 oppositions. Only after a number is assigned is the asteroid eligible to receive a name. For the reasons mentioned above, the sequence of numbers only approximately matches the timeline of discovery. Index to lists of minor planets The minor planets are listed in the following: See also By criteria References Further reading External links
Sex Chromosome Specialization and Degeneration in Mammals To view the full text, please login as a subscribed user or purchase a subscription. Click here to view the full text on ScienceDirect. Sex chromosomes—particularly the human Y—have been a source of fascination for decades because of their unique transmission patterns and their peculiar cytology. Register an Account If you do not have an account, create one by clicking the button below, and take full advantage of this site's features.
CH star CH stars are particular type of carbon stars which are characterized by the presence of exceedingly strong CH absorption bands in their spectra. They belong to the star population II, meaning they're metal poor and generally pretty middle-aged stars, and are underluminous compared to the classical C–N carbon stars. Many CH stars are known to be binaries, and it's reasonable to believe this is the case for all CH stars. Like Barium stars, they are probably the result of a mass transfer from a former classical carbon star, now a white dwarf, to the current CH-classed star. Ceres (dwarf planet) From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, and hence even at its brightest it is too dim to be seen with the naked eye except under extremely dark skies. Piazzi's book "Della scoperta del nuovo pianeta Cerere Ferdinandea" outlining the discovery of Ceres, dedicated the new "planet" to Ferdinand I of the Two Sicilies One of the astronomers selected for the search was Giuseppe Piazzi at the Academy of Palermo, Sicily. By this time, the apparent position of Ceres had changed (mostly due to the Earth's orbital motion), and was too close to the Sun's glare for other astronomers to confirm Piazzi's observations. The early observers were only able to calculate the size of Ceres to within about an order of magnitude. The name Ceres is pronounced /ˈsɪəriːz/ (SEER-eez). The old astronomical symbol of Ceres is a sickle, 〈⚳〉 ( ), similar to Venus's symbol 〈♀〉 but with a break in the circle, with a variant 〈 Ceres (bottom left), the Moon and the Earth, shown to scale
Organic farming is rarely enough Organic farming is sometimes touted as a way to feed the world's burgeoning population without destroying the environment. But the evidence for that has been hotly debated. Now, a comprehensive analysis of the existing science, published in Nature1, suggests that farming without the use of chemical fertilizers and pesticides could supply needs in some circumstances. maxim.photoshelter.com/Alamy Strawberries are among the few crops that grow almost as well on organic farms as in conventional agriculture. “I think organic farming does have a role to play because under some conditions it does perform pretty well,” says Verena Seufert, an Earth system scientist at McGill University in Montreal, Canada, and the study’s lead author. Area under inspection Seufert's meta-analysis reviewed 66 studies comparing the yields of 34 different crop species in organic and conventional farming systems. Fruitful farming “This is where yield increases are most needed,” says Seufert.
Astrochemistry Astrochemistry is the study of the abundance and reactions of chemical elements and molecules in the universe, and their interaction with radiation. The discipline is an overlap of astronomy and chemistry. The word "astrochemistry" may be applied to both the Solar System and the interstellar medium. The study of the abundance of elements and isotope ratios in Solar System objects, such as meteorites, is also called cosmochemistry, while the study of interstellar atoms and molecules and their interaction with radiation is sometimes called molecular astrophysics. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds is of special interest, because it is from these clouds that solar systems form. Spectroscopy One particularly important experimental tool in astrochemistry is spectroscopy, the use of telescopes to measure the absorption and emission of light from molecules and atoms in various environments. Research
Peak of eternal light A peak of eternal light (PEL) is a point on a body within the Solar System which is always in sunlight. Such a peak must have high altitude and be on a body with very small axial tilt. The existence of such peaks was first postulated by Beer and Mädler in 1837. The pair said of the lunar polar mountains, "...many of these peaks have (with the exception of eclipses caused by the Earth) eternal sunshine On the Moon Peaks of eternal light on the Moon would not be perfectly "eternal", since sunlight would still be cut off occasionally by the Earth's shadow during a lunar eclipse (which can last up to six hours) and by the shadows of other mountains and plateaus. Lunar north pole Lunar south pole The lunar south pole is situated in a huge depression (leading to 16 km altitude differences over the region). On Mercury References External links
10 of the World's Deadliest Plants — And How They Kill You The predator must also, for some reason or another, want to continue to pursue this plant for the toxicity to go so high. Additionally, why this particular poison for that plant? Evolution, fascinating, indeed. I do wonder if any of these are actually the predator. Maybe, the prey provide something that helps promulgates their genes. A lot of plant toxins are geared towards insects. (If you're a plant trying to fend off a moose, poison doesn't do you as much good, because the moose is so big that by the time your poison kills it, the moose has already destroyed you and 15-20 minutes worth of your neighbors. Since insects and mammals share a common (nerve- and muscle-endowed) evolutionary ancestor, there's a fair number of chemicals that can disrupt systems in both groups.
Primary Life Support System A Portable Life Support System from the Apollo A7L suit, with its outer cover removed A Primary (or Portable or Personal) Life Support System (or /Subsystem) (PLSS), is a device connected to an astronaut or cosmonaut's spacesuit, which allows extra-vehicular activity with maximum freedom, independent of a spacecraft's life support system. The PLSS is generally worn like a backpack. The functions performed by the PLSS include: regulating suit pressureproviding breathable oxygenremoving carbon dioxide, humidity, odors, and contaminants from breathing oxygencooling and recirculating oxygen through the pressure garment, and water through a Liquid Cooling and Ventilation Garment or Liquid Cooling Garment.two-way voice communicationdisplay and/or telemetry of suit health parameterstelemetry of an indicator of the wearer's immediate health (e.g. heart rate) Apollo PLSS The interior of the Apollo PLSS. The PLSS was 26 inches (66 cm) high, 18 inches (46 cm) wide, and 10 inches (25 cm) deep.
Galilean moons The four moons were discovered in either 1609 or 1610 when Galileo made improvements to his telescope, which enabled him to observe celestial bodies more distinctly than had ever been possible before. Galileo's discovery showed the importance of the telescope as a tool for astronomers by proving that there were objects in space that cannot be seen by the naked eye. More importantly, the incontrovertible discovery of celestial bodies orbiting something other than Earth dealt a serious blow to the then-accepted Ptolemaic world system, or the geocentric theory in which everything orbits around Earth. Galileo initially named his discovery the Cosmica Sidera ("Cosimo's stars"), but the names that eventually prevailed were chosen by Simon Marius. History Discovery As a result of improvements Galileo Galilei made to the telescope, with a magnifying capability of 20×, he was able to see celestial bodies more distinctly than was ever possible before. Name I. Members