My Science School

The International Astronomical Union  (IAU) is the only internationally recognized authority for assigning astronomical designations to celestial objects and surface features on them. The purpose of this is to ensure that names assigned are unambiguous. There have been many historical star catalogues, and new star catalogues are set up on a regular basis as new sky surveys are performed. All designations of objects in recent star catalogues start with an "initialism", which is kept globally unique by the IAU. Different star catalogues then have different naming conventions for what goes after the initialism, but modern catalogs tend to follow a set of generic rules for the data formats used.

The International Astronomical Union (IAU) is the officially recognized authority in astronomy for assigning designations to celestial bodies such as stars, planets, and minor planets, including any surface features on them. In response to the need for unambiguous names for astronomical objects, it has created a number of systematic naming systems for objects of various sorts.

 

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Since then, astronomers – who study the universe and everything in it, like planets – have used bigger and better telescopes to find rings around all of the outer gas giant planets: Jupiter, Saturn, Neptune and Uranus. These planets, unlike others in our system, consist largely of gas.

The first theory states that the rings formed at the same time as the planet. Some particles of gas and dust that the planets are made of were too far away from the core of the planet and could not be squashed together by gravity. They remained behind to form the ring system.

The second theory, and my personal favourite, is that the rings were formed when two of the moons of the planet, which had formed at the same time as the planet, somehow got disturbed in their orbits and eventually crashed into each other (an orbit is the circular path that the moon travels on around the planet). 

The other thing that all rings systems share is that they are all made of small particles of ice and rock. The smallest of these particles are no bigger than dust grains, while the largest of the particles are about 20 metres in diameter – about the size of a school hall. All the rings around the planets also contain gaps that are sometimes many kilometres wide and at first nobody could figure out why. We later learned that the gaps were caused by small moons that had gobbled up all the material in that particular part of the ring system.

 

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Tiangong-1 is a single-module space station operated by the China National Space Administration. The module was launched in 2011 and hosted two crews of taikonauts (Chinese astronauts) in 2012 and 2013. Since China's space agency discloses less information about its missions than other space agencies, the details surrounding the space station are not widely known. 

The orbit of the space station passes over most of the civilized world, with the exclusion of northern latitudes that include the United States, Russia and Canada, as well as the extreme south of the world, including Antarctica and the tip of South Africa. However, most of the Earth is covered by water, reducing the chances of a crash in a populated area.

Tiangong-1 (whose name means "Heavenly Palace") weighs about 8.5 metric tons, and is about 34 feet long by 11 feet wide (10.4 meters by 3.4 meters). It contains an experiment module — where the astronauts live and work — and a resource module that contains propellant tanks and rocket engines.

A primary goal for the module was to help the Chinese practice space dockings, which is an important skill for nations looking to build larger space stations or to send multiple spacecraft to the moon, Mars or other locations in the solar system.

 

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The Chang'e 1 lunar orbiter was China's first deep space mission. The program was divided into three phases: circling the Moon, landing on the Moon and returning from the Moon. The program goals were to be accomplished between 2007 and 2020.

The goal of this first mission, besides proving basic technologies and testing out several engineering systems, was to create a 3D map of the lunar surface, to analyze the distribution of certain chemicals on the lunar surface, to survey the thickness of the lunar soil, to estimate helium 3 resources, and to explore the space environment (solar wind, etc.) in near-lunar space.

The Chinese Lunar Exploration Program is designed to be conducted in four phases of incremental technological advancement: The first is simply reaching lunar orbit, a task completed by Chang'e 1 in 2007 and Chang'e 2 in 2010. The second is landing and roving on the Moon, as Chang'e 3 did in 2013 and Chang'e 4 did in 2019. The third is collecting lunar samples from the near-side and sending them to Earth, a task for the future Chang'e 5 and Chang'e 6 missions. The fourth phase consists of development of a robotic research station near the Moon's south pole. The program aims to facilitate a crewed lunar landing in the 2030s and possibly build an outpost near the south pole.

 

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In 2009, NASA launched a spacecraft called Kepler to look for exoplanets. Kepler looked for planets in a wide range of sizes and orbits. And these planets orbited around stars that varied in size and temperature.

Kepler detected exoplanets using something called the transit method. When a planet passes in front of its star, it’s called a transit. As the planet transits in front of the star, it blocks out a little bit of the star's light. That means a star will look a little less bright when the planet passes in front of it.

When a planet passes in front of a star as viewed from Earth, the event is called a “transit”. On Earth, we can observe an occasional Venus or Mercury transit. These events are seen as a small black dot creeping across the Sun—Venus or Mercury blocks sunlight as the planet moves between the Sun and us. Kepler finds planets by looking for tiny dips in the brightness of a star when a planet crosses in front of it—we say the planet transits the star.

Once detected, the planet's orbital size can be calculated from the period (how long it takes the planet to orbit once around the star) and the mass of the star using Kepler's Third Law of planetary motion. The size of the planet is found from the depth of the transit (how much the brightness of the star drops) and the size of the star. From the orbital size and the temperature of the star, the planet's characteristic temperature can be calculated. 

 

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Gamma Cephei Ab is an exoplanet approximately 45 light-years away in the constellation of Cepheus (the King). The planet was confirmed to be in orbit around Gamma Cephei A in 2002, but was first suspected to exist around 1988 (making this planet arguably the first true exoplanet discovered).

The first indications of Gamma Cephei Ab were reported in July 1988. The planet was tentatively identified by a Canadian team of astronomers, which was led by Bruce Campbell, Gordon Walker, and Stephenson Yang, while its existence was also announced by Anthony Lawton and P. Wright in 1989. Though not confirmed, this would have been the first true discovery of an extrasolar planet, and it was hypothesized based on the same radial velocity technique later used successfully by others. However, the claim was retracted in 1992 due to the quality of the data not being good enough to make a solid discovery.

On September 24, 2002, Gamma Cephei Ab was finally confirmed. The team of astronomers (including William D. Cochran, Artie P. Hatzes, et al.) at the Planetary Systems and their Formation Workshop announced the preliminary confirmation of a long-suspected planet Gamma Cephei Ab with a minimum mass of 1.59 MJ (1.59 times that of Jupiter). The parameters were later recalculated when direct detection of the secondary star Gamma Cephei B allowed astronomers to better constrain the properties of the system.

 

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Seconds after swallowing, food enters the stomach, the J-shaped, stretchy bag that links the oesophagus to the small intestine. While food is stored in the stomach it is churned into a creamy liquid called chime. This is released gradually into the small intestine, where digestion is completed.

Two types of digestion happen in the stomach. Firstly, food is doused in acidic gastric juice that contains pepsin, an enzyme that digests proteins. Secondly, muscles in the stomach’s wall create waves of contractions that crush and churn food into mushy chyme.

The stomach secretes acid and enzymes that digest food. Ridges of muscle tissue called rugae line the stomach. The stomach muscles contract periodically, churning food to enhance digestion. The pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.

 

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The abdomen contains hardworking organs from many of the body’s systems. Most of them help to digest food, clean the blood, or dispose of waste. Supporting them from beneath is a strong framework of bone and muscle called the pelvis.

The abdomen is the body region found between the thorax and the pelvis. Its superior aperture faces towards the thorax, enclosed by the diaphragm. Inferiorly the abdomen is open to the pelvis, communicating through the superior pelvic aperture (pelvic inlet). These two apertures, together with abdominal walls, bound the abdominal cavity.

The pelvis opens superiorly to the abdomen through the pelvic inlet, while its inferior opening (the pelvic outlet) is closed by the pelvic floor (levator ani and coccygeus muscles). The pelvic inlet is the boundary between the greater pelvis superiorly and lesser pelvis inferiorly.

 

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Because humans walk upright on two feet, it leaves our hands free to take on other tasks. Human hands are incredibly versatile tools, able to perform a huge range of movements.

The hand’s adaptability is made possible by the combination of a framework of small, flexible bones, including long finger bones and a highly moveable thumb. This structure is overlain with an intricate network of muscles and tendons, which move the bones.

Hand function has great significance for occupational performance. The greater the difficulties with hand function, the greater the impairment in skills that allow for independence and participation in academic and social activities.

The human arm, supported and controlled by a large number of muscles, together with the elbow and wrist joints, gives freedom to a hand that has become the willing servant of the human intellect. The hands are, as Kant is reported to have said, "Man’s outer brain."

 

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Body movement is controlled by skeletal muscle. About 650 skeletal muscles move the arms, legs, fingers and toes.

The muscle is attached to the bones via flexible cords, called tendons. The series of ridges across the muscle show its two interlocking proteins, actin and myosin. When the actin slides over myosin, the muscle contracts. The darker areas show actin and myosin overlapping, while the paler areas show actin alone. When skeletal muscle contracts, its tendon pulls on bone to make the body move.

Muscles are ennervated by motor neurons. A motor neuron and the muscle fibers ennervated by it form a motor unit. Size of motor units varies in the body, depending on the function of the muscle. Fine movements (eyes) have fewer muscle fibers per neuron to allow for fine movement. Muscles that require a lot of strength have many muscle fibers per unit. The body can control strength by deciding how many motor units it activates for a given function.

 

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Muscles must be kept strong and healthy, so the body can move easily and function properly. Diet and exercise play a major part in building and maintaining muscle.

Muscle food

Protein, such as that found in pulses such as beans and lentils, meat, nuts, and fish, is needed for building repairing muscle. Carbohydrates such as cereals, bread, and pasta provide energy for muscles t work. A balanced, healthy diet will provide enough protein and carbohydrate for muscles to stay healthy and active.

Resistance training

Some people build bigger muscles by resistance training. Regular exercise of this kind forces muscles to contract respectively, which builds and strengthens them. It also tears muscle fibres, which then grow back bigger, weight training, gymnastics, and some kinds of dancing are all forms of resistance training.

 

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Muscles are either fast-twitch or slow-twitch. Fast-twitch muscles contract quickly to generate lots of power. Slow-twitch muscles contract slowly and generate less power, but they work for longer without tiring. A healthy body has an equal split of fast- and slow-twitch muscle.

Slow-twitch muscle fibers have high concentrations of mitochondria and myoglobin. Although they are smaller than the fast-twitch fibers, they are surrounded by more capillaries. This combination supports aerobic metabolism and fatigue resistance, particularly important for prolonged submaximal (aerobic) exercise activities. 

Fast-twitch fibers have a high threshold and will be recruited or activated only when the force demands are greater than the slow-twitch fibers can meet. Fast-twitch fibers can generate more force, but are quicker to fatigue when compared to slow-twitch fibers. Strength and power training can increase the number of fast-twitch muscle fibers recruited for a specific movement. Fast-twitch fibers are called “white fibers” because do not contain much blood, which gives them a lighter appearance than slow-twitch fibers. 

Genetics determines how much of each muscle-fiber type you possess; however, identifying whether you are fast- or slow-twitch dominant would require an invasive muscle biopsy. Therefore, if you find that you tend to enjoy more endurance-based activities and that they are relatively easy for you, you probably have a greater number of slow-twitch fibers. Conversely, if you really dislike going for long runs, but enjoy playing sports that rely on short bursts of explosive movements, or if you like weight training because it is relatively easy, you are probably fast-twitch fiber dominant. 

 

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Muscles work by contracting, which means they shorten. As a muscle contracts, it pulls on whatever it is attached to. In general, the larger the muscles, the more pulling power it has. Muscles can pull but not push, which is why they work in pairs, acting in opposite directions. When one muscle pulls, its partner muscle relaxes.

Pulling together

All the skeletal muscles work in pairs, in the upper arm, the biceps and triceps muscles work as a team to bend and straighten the arm. The triceps pulls the forearm down, and the biceps pulls it up again.

Triceps

When the triceps muscle contracts, it straightens the arm at the elbow. The biceps, opposite the triceps, is relaxed.

Muscle attachment

The triceps is attached to the shoulder blade at this point.

Firmly fixed

The biceps is attached to the shoulder blade at these two points.

Biceps

When the biceps contracts, it pulls the forearm bones up and bends the arm. The triceps muscle is relaxed.

Tendons

Muscles are firmly attached to bones by tendons.

 

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Muscles receive their instructions from nerves. Signals from the brain travel down the spinal cord, and then go out to the muscles along nerves. Nerves branch out so they reach each part of the muscle. The signals tell the muscles to contract, and the body moves.

Nerves and muscles, working together as the neuromuscular system, make your body move as you want it to. They also make sure you do things you don’t even think about, such as breathe.

Nerves have cells called neurons. Neurons carry messages from the brain via the spinal cord. The neurons that carry these messages to the muscles are called motor neurons.

Each motor neuron ending sits very close to a muscle fibre. Where they sit together is called a neuromuscular junction. The motor neurons can release a chemical, which is picked up by the muscle fibre. This tells the muscle fibre to contract, which makes the muscles move.

 

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Muscles are packed full of parallel bundles of fibres. These consist of many cells, called myocytes. When they contract, the muscle shortens and so creates a pulling action. There are three types of muscle in the body.

Skeletal muscle

This type of muscle pulls on bones to move the skeleton. Skeletal muscle is made of long, cylindrical cells called muscle fibres, each crammed with threads called myofibrils. These contain long protein filaments that slide over each other to make muscles contract.

Smooth muscles

Arranged in muscular sheets, smooth muscle makes things move along inside the body. For example, it mixes food in the stomach and pushes it through the intestines. It is the weakest type of muscle but has an essential role in moving food along the digestive tract and maintaining blood circulation through the blood vessels.

Smooth muscle acts involuntarily and cannot be consciously controlled.

Heart muscles

This type of muscle is found only in the heart, where it is used to pump blood around the body. Heart muscle never gets tired, and it never stops working. This type of muscle is strong and acts involuntarily.

 

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