SUMMARY / RELATED TOPICS

Sednoid

A sednoid is a trans-Neptunian object with a perihelion greater than 50 AU and a semi-major axis greater than 150 AU. Only three objects are known from this population: 90377 Sedna, 2012 VP113, 2015 TG387, but it is suspected that there are many more. All of them have perihelia greater than 64 AU; these objects lie outside an nearly empty gap in the Solar System starting at about 50 AU, have no significant interaction with the planets. They are grouped with the detached objects; some astronomers, such as Scott Sheppard, consider the sednoids to be inner Oort cloud objects, though the inner Oort cloud, or Hills cloud, was predicted to lie beyond 2,000 AU, beyond the aphelia of the three known sednoids. This definition applies for 2013 SY99 which has a perihelion at 50.02 AU, far beyond the Kuiper cliff, but it is thought not to belong to the Sednoids, but to the same dynamical class as 2004 VN112, 2014 SR349 and 2010 GB174. With these high eccentricities > 0.8 they can be distinguished from the high-perihelion objects with moderate eccentricities which are in a stable resonance with Neptune, 2015 KQ174, 2015 FJ345, 2004 XR190, 2014 FC72 and 2014 FZ71.

The sednoids' orbits cannot be explained by perturbations from the giant planets, nor by interaction with the galactic tides. If they formed in their current locations, their orbits must have been circular, their present elliptical orbits can be explained by several hypotheses: These objects could have had their orbits and perihelion distances "lifted" by the passage of a nearby star when the Sun was still embedded in its birth star cluster. Their orbits could have been disrupted by an as-yet-unknown planet-sized body beyond the Kuiper belt such as the hypothesized Planet Nine, they could have been captured from around passing stars, most in the Sun's birth cluster. The three published sednoids, like all of the more extreme detached objects, have a similar orientation of ≈ 0°; this is not due to an observational bias and is unexpected, because interaction with the giant planets should have randomized their arguments of perihelion, with precession periods between 40 Myr and 650 Myr and 1.5 Gyr for Sedna.

This suggests that more undiscovered massive perturbers may exist in the outer Solar System. A super-Earth at 250 AU would cause these objects to librate around ω = 0°±60° for billions of years. There are multiple possible configurations and a low-albedo super-Earth at that distance would have an apparent magnitude below the current all-sky-survey detection limits; this hypothetical super-Earth has been dubbed Planet Nine. Larger, more-distant perturbers would be too faint to be detected; as of 2016, 27 known objects have a semi-major axis greater than 150 AU, a perihelion beyond Neptune, an argument of perihelion of 340°±55°, an observation arc of more than 1 year. 2013 SY99 is not considered a sednoid. On 1 October 2018, 2015 TG387 was announced with perihelion of 65 AU and a semimajor axis of 1094 AU. With an aphelion of 2123 AU, it brings the object further out than Sedna. In late 2015, V774104 was announced at the Division for Planetary Science conference as a further candidate sednoid, but its observation arc was too short to know whether its perihelion was outside Neptune's influence.

The talk about V774104 was meant to refer to 2015 TG387 though V774104 is the internal designation for non-Sednoid 2015 TH367. Sednoids might constitute a proper dynamical class; each of the proposed mechanisms for Sedna's extreme orbit would leave a distinct mark on the structure and dynamics of any wider population. If a trans-Neptunian planet were responsible, all such objects would share the same perihelion. If Sedna had been captured from another planetary system that rotated in the same direction as the Solar System all of its population would have orbits on low inclinations and have semi-major axes ranging from 100–500 AU. If it rotated in the opposite direction two populations would form, one with low and one with high inclinations; the perturbations from passing stars would produce a wide variety of perihelia and inclinations, each dependent on the number and angle of such encounters. Acquiring a larger sample of such objects would therefore help in determining which scenario is most likely.

"I call Sedna a fossil record of the earliest Solar System", said Brown in 2006. "Eventually, when other fossil records are found, Sedna will help tell us how the Sun formed and the number of stars that were close to the Sun when it formed." A 2007–2008 survey by Brown and Schwamb attempted to locate another member of Sedna's hypothetical population. Although the survey was sensitive to movement out to 1,000 AU and discovered the dwarf planet Gonggong, it detected no new sednoids. Subsequent simulations incorporating the new data suggested about 40 Sedna-sized objects exist in this region, with the brightest being about Eris's magnitude. Following the discovery of 2015 TG387, Sheppard et al. concluded that it implies a population of about 2 million Inner Oort Cloud objects larger than 40 km, with a total mass in the range of 1×1022 kg. New icy body hints at planet lurkin

Temnospondyli

Temnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including fresh water and coastal marine environments, their life history is well understood, with fossils known from the larval stage and maturity. Most temnospondyls were semiaquatic, although some were fully terrestrial, returning to the water only to breed; these temnospondyls were some of the first vertebrates adapted to life on land. Although temnospondyls are considered amphibians, many had characteristics, such as scales and armour-like bony plates, that distinguish them from modern amphibians. Temnospondyls have been known since the early 19th century, were thought to be reptiles, they were described at various times as batrachians and labyrinthodonts, although these names are now used.

Animals now grouped in Temnospondyli were spread out among several amphibian groups until the early 20th century, when they were found to belong to a distinct taxon based on the structure of their vertebrae. Temnospondyli means "cut vertebrae". Experts disagree over whether temnospondyls were ancestral to modern amphibians, or whether the whole group died out without leaving any descendants. Different hypotheses have placed modern amphibians as the descendants of temnospondyls, another group of early tetrapods called lepospondyls, or as descendants of both groups. Recent studies place a family of temnospondyls called the amphibamids as the closest relatives of modern amphibians. Similarities in teeth and hearing structures link the two groups. Many temnospondyls are much larger than living amphibians, superficially resemble crocodiles. Others resemble salamanders. Most have flat heads that are either blunt or elongated; the skulls are rounded or triangular in shape when viewed from above, are covered in pits and ridges.

The rugged surfaces of bones may have supported blood vessels, which could transfer carbon dioxide to the bones to neutralize acidic build up in the blood. Many temnospondyls have canal-like grooves in their skulls called sensory sulci; the sulci, which run around the nostrils and eye sockets, are part of a lateral line system used to detect vibrations in water. As semiaquatic animals, all known temnospondyls have small limbs with no more than four toes on each front foot and five on each hind foot. Terrestrial temnospondyls have larger, thicker limbs, some have claws. One unusual terrestrial temnospondyl, has long limbs for its body, lived as an active runner able to chase prey. Homologues of most of the bones of temnospondyls are seen in other early tetrapods, aside from a few bones in the skull, such as interfrontals and interparietals, that have developed in some temnospondyl taxa. Most temnospondyls have tabular horns in the backs of their skulls, rounded projections of bone separated from the rest of the skull by indentations called otic notches.

Among the most distinguishing features of temnospondyls are the interpterygoid vacuities, two large holes in the back of the palate. Another pair of holes, are present in front of these vacuities, connect the nasal passage with the mouth. Temnospondyls have teeth on their palates, as well as in their jaws; some of these teeth are so large, they are referred to as tusks. In some temnospondyls, such as Nigerpeton, tusks in the lower jaw pierce the palate and emerge through openings in the top of the skull. Little is known of the soft tissue of temnospondyls. A block of sandstone, described in 2007 from the Early Carboniferous Mauch Chunk Formation of Pennsylvania, included impressions of the bodies of three temnospondyls; these impressions show, when alive, they had smooth skin, robust limbs with webbed feet, a ridge of skin on their undersides. Trackways referable to small temnospondyls have been found in Carboniferous and Permian rocks; the trackways, called batrachichni, are found in strata deposited around freshwater environments, suggesting the animals had some ties to the water.

Unlike modern amphibians, many temnospondyls are covered in small packed scales. The undersides of most temnospondyls are covered in rows of large ventral plates. During early stages of development, they first have only rounded scales. Fossils show, as the animals grew, the scales on the undersides of their bodies developed into large, wide ventral plates; the plates overlap each other in a way. Semiaquatic temnospondyls, such as trematosaurs and capitosaurs, have no evidence of scales, they may have lost scales to make movement easier under water or to allow cutaneous respiration, the absorption of oxygen through the skin. Several groups of temnospondyls have large bony plates on their backs. One temnospondyl, has armour-like plating that covers both its back and underside; the temnospondyl Laidleria has ex

Paul J. Kern

Paul John Kern became President and Chief Operating Officer of AM General LLC on August 1, 2008. Kern is a former United States Army officer. From October 2001 to November 2004, he served as Commanding General of the United States Army Materiel Command. Kern served as the Commander, 4th Infantry Division, he was the senior military assistant to the Secretary of Defense and Deputy Secretary of Defense. Kern served as Team Chief, Light Combat Vehicle Team, Office of the Deputy Chief of Staff for Research and Acquisition, as the Program Branch Chief, Bradley Fighting Vehicle Systems, Michigan, he taught weapon systems and automotive engineering at the United States Military Academy and was the department's research officer. Kern served two tours in Vietnam with the 11th Armored Cavalry Regiment as a platoon leader and troop commander, was a battalion operations officer with the 3rd Armored Division in Germany, he commanded the 5th Battalion, 32nd Armor, 24th Infantry Division at Fort Stewart, Georgia.

Kern is a native of West Orange, New Jersey, attended West Orange High School in his hometown. He was commissioned in 1967 as an Armor officer following graduation from the United States Military Academy. In 1973 he earned master's degrees in both mechanical and civil engineering from the University of Michigan. In June 2004 Kern was chosen to head the internal military investigation of the Abu Ghraib torture scandal referred to as the Fay Report, his awards and decorations include the Defense Distinguished Service Medal, Army Distinguished Service Medal, Silver Star, Defense Superior Service Medal, Legion of Merit, Bronze Star, Bronze Star Medal, Purple Heart, Meritorious Service Medal, Army Commendation Medal, Parachutist Badge, Ranger Tab. Defense Distinguished Service Medal Army Distinguished Service Medal Silver Star Defense Superior Service Medal Legion of Merit with oak leaf cluster Bronze Star with Valor Device and oak leaf cluster, Bronze Star with two oak leaf clusters Purple Heart with two oak leaf clusters Meritorious Service Medal with four oak leaf clusters Army Commendation Medal Parachutist Badge Ranger Tab After retirement in January 2005, Kern joined the Board of Directors of EDO Corporation and iRobot Corporation, is a member of the External Advisory Board of the University of Michigan Department of Mechanical Engineering, a Senior Counselor of The Cohen Group.

Kern now serves as the Chair of Advanced Technology in the Department of Civil and Mechanical Engineering at the United States Military Academy. This article incorporates public domain material from the United States Government document ""