2011 HM102

2011 HM₁₀₂, also written 2011 HM102, is the ninth Neptune trojan discovered. It was first observed on April 29, 2011 by the New Horizons KBO Search Survey. It has the same orbital period as Neptune and orbits at the L₅ Lagrangian point about 60 degrees backwards of Neptune.

Orbit

2011 HM₁₀₂ follows a low-eccentricity (0.08) orbit, and its semi-major axis (30.05 AU) is very similar to Neptune's (30.10 AU), orbiting in a 1:1 mean-motion resonance with it. It has a high orbital inclination of 29.42°. This large value makes 2011 HM₁₀₂, as of July 2013, the highest-inclination Neptune trojan known.2011 HM₁₀₂ has been observed 145 times, over two oppositions.

Physical properties

With an absolute magnitude of 8.1, it has a diameter somewhere between 90 kilometres (56 mi) and 180 kilometres (110 mi). This makes 2011 HM₁₀₂, as of October 2012, the brightest L₅ trojan in the entire Solar System.

2013 New Horizons flyby

In October 2012, 2011 HM₁₀₂ was the closest known object of any kind to the New Horizons spacecraft. In mid- to late-2013, New Horizons was scheduled to pass within 1.2 AU of 2011 HM₁₀₂, where it would be detectable with one of the onboard instruments. An observation from New Horizons would measure the phase curve of 2011 HM₁₀₂ at phase angles unobtainable from the Earth. The New Horizons team eventually decided that they would not target 2011 HM₁₀₂ for observations (as the preparations for the Pluto approach took precedence).

New Horizons

New Horizons is an interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a team led by S. Alan Stern, the spacecraft was launched with the primary mission to perform a flyby study of the Pluto system, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs).

On January 19, 2006, New Horizons was launched from Cape Canaveral Air Force Station directly into an Earth-and-solar escape trajectory with a speed of about 16.26 kilometers per second (58,536 km/h; 36,373 mph). After a brief encounter with asteroid 132524 APL, New Horizons proceeded to Jupiter, making its closest approach on February 28, 2007, at a distance of 2.3 million kilometers (1.4 million miles). The Jupiter flyby provided a gravity assist that increased New Horizons' speed; the flyby also enabled a general test of New Horizons' scientific capabilities, returning data about the planet's atmosphere, moons, and magnetosphere.

M2 Browning

The M2 Machine Gun or Browning .50 Caliber Machine Gun is a heavy machine gun designed towards the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, which was chambered for the .30-06 cartridge. The M2 uses the much larger and much more powerful .50 BMG cartridge, which was developed alongside and takes its name from the gun itself (BMG standing for Browning Machine Gun). It has been referred to as "Ma Deuce", in reference to its M2 nomenclature. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly armored vehicles and boats, light fortifications and low-flying aircraft. The M2 machine gun has been produced longer than any other machine gun.

The Browning .50 caliber machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1930s to the present. It was heavily used during World War II, the Korean War, the Vietnam War, the Falklands War, the Iraq War and the War in Afghanistan in the 2000s and 2010s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries. The M2 has been in use longer than any other small arm in U.S. inventory except the .45 ACP M1911 pistol, also designed by John Browning.

Neptune trojan

Neptune trojans are bodies in orbit around the Sun that orbit near one of the stable Lagrangian points of Neptune. They therefore have approximately the same orbital period as Neptune and follow roughly the same orbital path. Twelve Neptune trojans are currently known, of which nine orbit near the Sun–Neptune L₄ Lagrangian point 60° ahead of Neptune and three orbit near Neptune's L₅ region 60° behind Neptune. The Neptune trojans are termed 'trojans' by analogy with the Jupiter trojans.

The discovery of 2005 TN53 in a high-inclination (>25°) orbit was significant, because it suggested a "thick" cloud of trojans (Jupiter trojans have inclinations up to 40°), which is indicative of freeze-in capture instead of in situ or collisional formation. It is suspected that large (radius ≈ 100 km) Neptune trojans could outnumber Jupiter trojans by an order of magnitude.

In 2010, the discovery of the first known L₅ Neptune trojan, 2008 LC18, was announced. Neptune's trailing L₅ region is currently very difficult to observe because it is along the line-of-sight to the center of the Milky Way, an area of the sky crowded with stars.

Machine gun

A machine gun is a fully automatic mounted or portable firearm, designed to fire bullets in quick succession from an ammunition belt or magazine, typically at a rate of 300 to 1800 rounds per minute. Fully automatic weapons are generally categorized as submachine guns, assault rifles, battle rifles, automatic shotguns, machine guns, or autocannons.

As a class of military firearms, true machine guns are fully automatic weapons designed to be used as support weapons and generally used when attached to a mount or fired from the ground on a bipod or tripod. Light machine guns are small enough to be fired hand-held, but are more effective when fired from a prone position. The difference between machine guns and other categories of weapons is based on caliber, with autocannons using calibers larger than 20 mm, and whether the gun fires conventional bullets, shotgun cartridges, or explosive rounds. Fully automatic guns firing shotgun cartridges are usually called automatic shotguns, and those firing large-caliber explosive rounds are generally considered either autocannons or automatic grenade launchers ("grenade machine guns"). Submachine guns are hand-held automatic weapons for personal defense or short-range combat firing pistol-caliber rounds. In contrast to submachine guns and autocannons, machine guns (like rifles) tend to have a very high ratio of barrel length to caliber (a long barrel for a small caliber); indeed, a true machine gun is essentially a fully automatic rifle, and often the primary criterion for a machine gun as opposed to a battle rifle is the presence of a quick-change barrel, heavyweight barrel, or other cooling system. Battle rifles and assault rifles may be capable of fully automatic fire, but are not designed for sustained fire.