14827 Hypnos, provisional designation 1986 JK, is a highly eccentric, sub-kilometer-sized carbonaceous asteroid that is thought to be an extinct comet. It is classified as near-Earth object and potentially hazardous asteroid of the Apollo group.
|Discovered by||C. S. Shoemaker|
E. M. Shoemaker
|Discovery site||Palomar Obs.|
|Discovery date||5 May 1986|
|MPC designation||(14827) Hypnos|
(Greek god of sleep)
|Apollo · NEO · PHA |
|Orbital characteristics |
|Epoch 4 September 2017 (JD 2458000.5)|
|Uncertainty parameter 0|
|Observation arc||19.32 yr (7,058 days)|
|4.79 yr (1,749 days)|
|0° 12m 21.24s / day|
|Earth MOID||0.0147 AU · 5.7 LD|
|Jupiter MOID||0.5249 AU|
> 0.74 km
0.9 km (Gehrels 1994)
0.907 km (derived)
< 0.067 (radar)
B–V = 0.684 
U–B = 0.492 
|18.3 · 18.65±0.22 · 18.94|
Hypnos orbits the Sun at a distance of 0.9–4.7 AU once every 4 years and 9 months (1,749 days). Its orbit has a high eccentricity of 0.67 and an inclination of 2° with respect to the ecliptic. It is frequently perturbed by Jupiter.
In 1958, Hypnos passed less than 0.03 AU from both Earth and Mars. Neither planet has been approached so closely by Hypnos since the 862 AD pass of Earth, or will be until the 2214 pass of Earth. It is also a Mars-crosser.
As of 2018, no rotational lightcurve of Hypnos has been obtained from photometric observations. The asteroids rotation period and spin axis remains unknown. It has a low brightness amplitude of 0.05 magnitude which indicates that the body has a rather spheroidal shape.
According to the NEOSurvey carried out by NASA's Spitzer Space Telescope, Hypnos measures 520 meters in diameter and its surface has an albedo of 0.22 based on an absolute magnitude of 18.65, while infrared radiometry gave a radar albedo of no more than 0.067 and a diameter of at least 740 meters.
The Collaborative Asteroid Lightcurve Link assumes a standard optical albedo for carbonaceous asteroids 0.057 and derives a diameter of 907 meters with an absolute magnitude of 18.94. The diameter agrees with Tom Gehrels 1994-publication Hazards due to Comets and Asteroids in which he estimated a mean-diameter of 900 meters for Hypnos.
This minor planet was named after Hypnos from Greek mythology. He is the god of sleep, son of Nyx and Erebus and twin brother of Thanatos. He enters the sleep of mortals and gives them dreams of foolishness or inspiration. The English word "hypnosis" is derived from his name. The official naming citation was published by the Minor Planet Center on 6 January 2003 (M.P.C. 47301).
The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth (> 1 AU) but perihelion distances less than the Earth's aphelion distance (q < 1.017 AU).As of December 2018 the number of known Apollo asteroids is 10,485, making the class the largest group of near-Earth objects (cf. the Aten, Amor and Atira asteroids), of which 1,409 are numbered (asteroids are not numbered until they have been observed at two or more oppositions), and 1,648 are identified as potentially hazardous asteroids.The closer their semi-major axis is to Earth's, the less eccentricity is needed for the orbits to cross. The February 15, 2013 Chelyabinsk meteor that exploded over the city of Chelyabinsk in the southern Urals region of Russia, injuring an estimated 1000 people with flying glass from broken windows, was an Apollo class asteroid.Carolyn S. Shoemaker
Carolyn Jean Spellmann Shoemaker (born June 24, 1929) is an American astronomer and is a co-discoverer of Comet Shoemaker–Levy 9. She once held the record for most comets discovered by an individual.Although Carolyn had earned degrees in history, political science and English literature, she had almost no interest in science until after she met and married Eugene M. ("Gene") Shoemaker in 1950-51). She said later that his explanations of his work thrilled her. Despite her relative inexperience and her lack of a relevant scientific degree, Caltech had no objection to her joining Gene's team at the California Institute of Technology as a research assistant. Carolyn had already showed herself to be unusually patient, and she had already demonstrated exceptional stereoscopic vision, both qualities were extremely valuable in a career looking for objects in near-earth space.Comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times the Earth's diameter, while the tail may stretch one astronomical unit. If sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° (60 Moons) across the sky. Comets have been observed and recorded since ancient times by many cultures.
Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars and the galactic tide. Hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition.
Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma (the central part immediately surrounding the nucleus) and the tail (a typically linear section consisting of dust or gas blown out from the coma by the Sun's light pressure or outstreaming solar wind plasma). However, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System. The discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. In the early 21st century, the discovery of some minor bodies with long-period comet orbits, but characteristics of inner solar system asteroids, were called Manx comets. They are still classified as comets, such as C/2014 S3 (PANSTARRS). 27 Manx comets were found from 2013 to 2017.As of July 2018 there are 6,339 known comets, a number that is steadily increasing as they are discovered. However, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System (in the Oort cloud) is estimated to be one trillion. Roughly one comet per year is visible to the naked eye, though many of those are faint and unspectacular. Particularly bright examples are called "great comets". Comets have been visited by unmanned probes such as the European Space Agency's Rosetta, which became the first ever to land a robotic spacecraft on a comet, and NASA's Deep Impact, which blasted a crater on Comet Tempel 1 to study its interior.Comet nucleus
The nucleus is the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun. A typical comet nucleus has an albedo of 0.04. This is blacker than coal, and may be caused by a covering of dust.Results from the Rosetta and Philae spacecraft show that the nucleus of 67P/Churyumov–Gerasimenko has no magnetic field, which suggests that magnetism may not have played a role in the early formation of planetesimals. Further, the ALICE spectrograph on Rosetta determined that electrons (within 1 km (0.62 mi) above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma. On 30 July 2015, scientists reported that the Philae spacecraft, that landed on comet 67P/Churyumov-Gerasimenko in November 2014, detected at least 16 organic compounds, of which four (including acetamide, acetone, methyl isocyanate and propionaldehyde) were detected for the first time on a comet.Eugene Merle Shoemaker
Eugene Merle Shoemaker (April 28, 1928 – July 18, 1997), also known as Gene Shoemaker, was an American geologist and one of the founders of the field of planetary science. He is best known for co-discovering the Comet Shoemaker–Levy 9 with his wife Carolyn S. Shoemaker and David H. Levy. This comet hit Jupiter in July 1994: the impact was televised around the world.
Shoemaker was also well known for his studies of terrestrial craters, such as Barringer Meteor Crater in Arizona. Shoemaker was also the first director of the United States Geological Survey's Astrogeology Research Program.Extinct comet
An extinct comet is a comet that has expelled most of its volatile ice and has little left to form a tail and coma. In a dormant comet, rather than being depleted, any remaining volatile components have been sealed beneath an inactive surface layer.
Due to the near lack of a coma and tail, an extinct or dormant comet may resemble an asteroid rather than a comet and blur the distinction between these two classes of small Solar System bodies. When volatile materials such as nitrogen, water, carbon dioxide, ammonia, hydrogen and methane in the comet nucleus have evaporated away, all that remains is an inert rock or rubble pile. A comet may go through a transition phase as it comes close to extinction.Hypnos (disambiguation)
Hypnos is the personification of sleep in Greek mythology.
Hypnos may also refer to:
Hypnos (genus), a genus of electric rays in the family Torpedinidae
"Hypnos" (short story), a short story by H. P. Lovecraft
Hypno, a Pokémon
Hypnos T-type Tyrant, an enemy in the video game Resident Evil Survivor
Hypnos (record label), an independent record label
14827 Hypnos, an asteroid
Citroën Hypnos, a concept car
Hypnos (band), a Czech death metal band
Hypnos Entertainment, a video game developerList of Earth-crossing minor planets
An Earth-crosser is a near-Earth asteroid whose orbit crosses that of Earth as observed from the ecliptic pole of Earth's orbit. The known numbered Earth-crossers are listed here. Those Earth-crossers whose semi-major axes are smaller than Earth's are Aten asteroids; the remaining ones are Apollo asteroids. (See also the Amor asteroids.)
An asteroid with an Earth-crossing orbit is not necessarily in danger of colliding with Earth. The orbit of an Earth-crossing asteroid may not even intersect with that of Earth. This apparent contradiction arises because many asteroids have highly inclined orbits, so although they may have a perihelion less than that of Earth, their paths can never cross. An asteroid for which there is some possibility of a collision with Earth at a future date and which is above a certain size is classified as a potentially hazardous asteroid (PHA). Specifically, an asteroid is a PHA if its Earth minimum orbital intersection distance (MOID) is <0.05 AU and its absolute magnitude is 22 or brighter. The concept of PHA is intended to replace the now abandoned strict definition of ECA (Earth-crossing asteroid) which existed for a few years. Determining if an asteroid was an ECA required calculation of its orbits millennia into the future, including planetary gravitational perturbations, to assess whether a collision with Earth was possible and this has proved to be impractical.Having a small MOID is not a guarantee of a collision. On the other hand, small gravitational perturbations of the asteroid around its orbit from planets that it passes can significantly alter its path. For instance, 99942 Apophis will approach Earth so closely in 2029 that it will get under the orbit of the Earth's geostationary satellites.Of the Earth-crossing asteroids, 3753 Cruithne is notable for having an orbit that has the same period as Earth's.List of Mars-crossing minor planets
A Mars-crossing asteroid (MCA, also Mars-crosser, MC) is an asteroid whose orbit crosses that of Mars. The known numbered Mars-crossers are listed here. They include the two numbered Mars trojans 5261 Eureka and (101429) 1998 VF31.
Many databases, for instance the JPL Small-Body Database (JPL SBDB), only list asteroids with a perihelion greater than 1.3 AU as Mars-crossers. An asteroid with a perihelion less than this is classed as a near-Earth object even though it is crossing the orbit of Mars as well as crossing (or coming near to) that of Earth. Nevertheless, these objects are listed on this page. A grazer is an object with a perihelion below the aphelion of Mars (1.67 AU) but above the Martian perihelion (1.38 AU). The JPL SBDB lists 13,500 Mars-crossing asteroids. Only 18 MCAs are brighter than absolute magnitude (H) 12.5, which typically makes these asteroids with H<12.5 more than 13 km in diameter depending on the albedo. The smallest known MCAs have an absolute magnitude (H) of around 24 and are typically less than 100 meters in diameter.List of Solar System objects by size
This is a partial list of Solar System objects by size, arranged in descending order of mean volumetric radius, and subdivided into several size classes. These lists can also be sorted according to an object's mass and, for the largest objects, volume, density and surface gravity, insofar as these values are available. This list contains the Sun, the planets, dwarf planets, many of the larger small Solar System bodies (which includes the asteroids), all named natural satellites, and a number of smaller objects of historical or scientific interest, such as comets and near-Earth objects.
The ordering may be different depending on whether one chooses radius or mass, because some objects are denser than others. For instance, Uranus is larger than Neptune but less massive, and although Ganymede and Titan are larger than Mercury, they have less than half Mercury's mass. This means some objects in the lower tables, despite their smaller radii, may be more massive than objects in the upper tables because they have a higher density.
Many trans-Neptunian objects (TNOs) have been discovered, and their approximate locations in this list are shown, even though there can be a large uncertainty in their measurement.
Solar System objects more massive than 1021 kilograms (one yottagram [Yg]) are known or expected to be approximately spherical. Astronomical bodies relax into rounded shapes (ellipsoids), achieving hydrostatic equilibrium, when the gravity of their mass is sufficient to overcome the structural strength of their material. Objects made of ice become round more easily than those made of rock, and many icy objects are spheroidal at far lower sizes. The cutoff boundary for roundness is somewhere between 100 km and 200 km in radius.The larger objects in the mass range between 1018 kg to 1021 kg (1 to 1000 zettagrams [Zg]), such as Tethys, Ceres, and Mimas, have relaxed to an oblate-spheroid equilibrium due to their gravity, whereas the less massive rubble piles (e.g. Amalthea and Janus) are roughly rounded, but not spherical, dubbed "irregular".
Spheroidal bodies typically have some polar flattening due to the centrifugal force from their rotation, and can sometimes even have quite different equatorial diameters (scalene ellipsoids such as Haumea). Unlike bodies such as Haumea, the irregular bodies deviate significantly from the shape of an ellipsoid.
There can be difficulty in determining the diameter (within a factor of about 2) for typical objects beyond Saturn. (See 2060 Chiron as an example.) For TNOs there is some confidence in the diameters, but for non-binary TNOs there is no real confidence in the masses/densities. Many TNOs are often just assumed to have Pluto's density of 2.0 g/cm3, but it is just as likely that they have a comet-like density of only 0.5 g/cm3. For example, if a TNO is poorly assumed to have a mass of 3.59×1020 kg based on a radius of 350 km with a density of 2 g/cm3 and is later discovered to only have a radius of 175 km with a density of 1 g/cm3, the mass estimate would be only 2.24×1019 kg.
The sizes and masses of many of the moons of Jupiter and Saturn are fairly well known due to numerous observations and interactions of the Galileo and Cassini orbiters. But many of the moons with a radius less than ~100 km, such as Jupiter's Himalia, still have unknown masses. Again, as we get further from the Sun than Saturn, things get less clear. There has not yet been an orbiter around Uranus or Neptune for long-term study of their moons. For the small outer irregular moons of Uranus, such as Sycorax, which were not discovered by the Voyager 2 flyby, even different NASA web pages, such as the National Space Science Data Center and JPL Solar System Dynamics, have somewhat contradictory size and albedo estimates depending on which research paper is being cited.
Data for objects has varying reliability including uncertainties in the figures for mass and radius, and irregularities in the shape and density, with accuracy often depending on how close it is to Earth or whether it has been visited by a probe.