Solar tsunamis are surges of material sent crashing across the Sun as the result of a solar flare being launched into space. They can travel at speeds up to 1.6 million km (1 million miles) per hour. These solar tsunamis are made of hot plasma and magnetic energy.

The first was observed by Gail Moreton in 1959, and since then several more studies have been conducted by the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO) spacecraft, both of which orbit the Earth.

Solar tsunamis are formed when the Sun emits a coronal mass ejection (CME) – a massive burst of solar wind commonly associated with solar flares. Around the ejection point, a circular wave extends outwards in all directions and travels across the surface of the Sun at a super-fast rate. In February 2009, the two STEREO spacecraft watched as a billion-ton cloud of gas was hurled off the surface of the Sun from a CME.

The result of this ejection was a massive solar tsunami that towered 100,000km (60,000 miles) high and which sped across the star’s surface at about 900,000km (560,000 miles) per hour. It was estimated to contain the same energy as 2.4 million megatons of TNT.

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Solar wind streams from the Sun at a blistering 400 kilometres (250 miles) per second. The intense heat of the corona – the outermost portion of the Sun’s atmosphere – energises particles to such a level that the Sun’s gravitational field can no longer hold on to them and they escape into space.

Solar wind strength varies, creating space weather capable of disrupting technology, like global positioning system (GPS) satellites.

The movement of solar wind has a characteristic pattern that resembles a rope wobbling up and down – technically known as an Alfvén wave (after Hannes Alfvén). These magnetic strings can be observed as the greenish light that appears during the polar auroras.

Until recently scientists have struggled to understand this unusual wave behaviour, but a new set of models – based on similar waves generated by polarised light – might enable us to understand, and even predict, future fluctuations in solar wind.




Most stars are born in a huge cloud of gas and dust, called a nebula. The story starts when the nebula begins to shrink, then divides into smaller, swirling clumps. As each clump continues to collapse, the material in it becomes hotter and hotter. When it reaches about 18 million F (10 million C), nuclear reactions start and a new star is made.

Nebulas can be different colors. The color comes from the dust in the nebula, which can either absorb or reflect the radiation from newborn stars. In a blue nebula, light is reflected by small dust particles. A red nebula is caused by stars heating the dust and gas.

This is one of three huge fingers of cool hydrogen gas and dust. At the top of this finger, hot young stars shine brightly among the dark dust. Eventually these stars will blow the dust away and become clearly visible as a new star cluster.

Not all nebulas are colorful. The black Horsehead Nebula is a cloud of cold dust and gas that forms part of the Orion Nebula. The horse’s head shows up against the red nebula behind it, which is heated by stars. Many stars have formed in the Orion Nebula within the last million years.

The Pleiades cluster lies in the constellation of Taurus. It is also known as the Seven Sisters, because up to seven of its massive, white-hot stars can be seen with the naked eye. There are more than 300 young stars in the cluster, surrounded by a thin dust cloud that shows as a pale blue haze.

V838 Monocerotis is a red supergiant star, located about 20,000 light-years away from Earth. In March 2002, this star suddenly flared to 10,000 times its normal brightness. The series of images below shows how a burst of light from the star spread out into space, reflecting off the layers of dust that surround the star. This effect is called a light echo. The images make it look as if the nebula itself is growing, but it isn’t. The spectacular effect is caused by light from the stellar flash sweeping outward and lighting up more of the nebula.

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Sweat is produced by dedicated sweat glands, and is a mechanism used primarily by the body to reduce its internal temperature. There are two types of sweat gland in the human body, the eccrine gland and the apocrine gland. The former regulates body temperature, and is the primary source of excreted sweat, with the latter only secreting under emotional stresses, rather than those involved with body dehydration.

Eccrine sweat glands are controlled by the sympathetic nervous system and, when the internal temperature of the body rises, secrete a salty, water-based substance to the skin’s surface. This liquid then cools the skin and the body through evaporation, storing and then transferring excess heat into the atmosphere.

Both the eccrine and apocrine sweat glands only appear in mammals and, if active over the majority of the animal’s body, act as the primary thermoregulatory device. Certain mammals only have eccrine glands in specific areas – such as paws and lips – warranting the need to pant to control their temperature.

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The red colour that we usually see in images of Mars is actually the result of iron rusting. Rocks and soil on the surface of Mars contained a dust composed mostly of iron and small amounts of other elements such as chlorine and sulphur. The rocks and soil were then eroded by wind and the resulting dust was blown across the planet’s surface by the activity of ancient volcanoes. Recent evidence suggests dust was also spread across Mars by water, a theory backed up by the presence of channels and ducts across the planet’s surface.

The iron contained within the dust then reacted with the oxygen in the atmosphere, producing the distinctive red rust colour, while the sky appears red because storms carried the red dust high up into the planet’s atmosphere. This dusty surface, which is between a few millimetres and two metres deep, also sits above a layer of hardened lava which is mostly composed of basalt. The concentration of iron that is found in this basalt is much higher than it is in basalt on Earth, and this also contributes to the red appearance of Mars.


When we breathe in, the inhaled air can contain dust, chemicals and other irritants that can be harmful to the body, particularly to organs in the respiratory system like the lungs. While the tiny hairs inside the nostrils (cilia) trap many of these particles, some will often get through. To help you out, your body reacts to try and forcibly expel the offending particles via the sneeze reflex arc.

There are a number of other reasons why we sneeze, including to clear the nasal passages when you have a cold, to expel allergens if you are allergic to something, and even bright sunlight can cause some people to sneeze.

When a stimuli is detected by the nerve endings in the nose, impulses are sent to the brain, which initiates a chain of physiological events that enable the body to rid itself of the unwelcome item.


If you look up into the sky on a clear night, you will see thousands of stars, but how do you know which star is which? Luckily, the stars form groups known as constellations, which can help you find your way around the heavens.

Early astronomers noticed that the stars formed groups and that these groups moved in a regular way across the heavens. They began to use characters, animals, and objects from their myths and legends to remember these groups. Most of the constellation names we use today date from Greek and Roman times, but some go back even further to the Egyptians, Babylonians, and Sumerians.

Finding the North Star
The North Star sits almost directly above the North Pole, which makes it an excellent way to find due north. It is visible all year in the northern hemisphere at the tip of a constellation called Ursa Minor (the Little Bear). To find it, you can use another constellation called Ursa Major (the Great Bear). Seven of its stars form a shape that is known as the Big Dipper. The two stars that form the front of this shape point to the North Star, which is the next bright star you see.

A group of 12 constellations can be seen in both hemispheres. The ancients called them the zodiac, from the Greek word for animals. Most of them are named after animals, but some are human and one is an object. The zodiac runs along a path in the sky called the ecliptic, which is at an angle of 23 degrees to the equator. The Sun, Moon, and planets also move on paths close to the ecliptic.



Genetics is the scientific study of genes – the instructions that govern a person’s growth, development, and health.

These are passed down from parents to children via sexual reproduction. Each cell in the human body has more than 20,000 genes stored in the cell’s nucleus. They provide the entire genetic code for a person and vary so that, apart from identical twins, each person has slightly different genes and has their own unique set of features.

Genes are found contained within long ribbon-like strands of deoxyribonucleic acid(DNA) molecules. Pairs of DNA molecules wind round in what is called a double helix. They are linked by chemical substances called bases, which are found in pairs. Long sequences of base pairs form genes. DNA can copy itself when cell division occurs so that a precise copy of the DNA is present in the new cell.

DNA is packaged into 23 pairs of chromosomes inside a cell. Twenty-two of these pairs are similar in men and women. The 23rd pair are the sex chromosomes. These consist of two X chromosomes in females (XX) and one X and one Y chromosome in males (XY). Male and female sex cells (sperm and eggs) contain just one of the two sex chromosomes. A male child develops if the sperm contains the Y chromosome.

Three generations of the same family share many similar features as a result of a parent and child sharing 99.95 per cent of the same DNA. A child inherits half of their chromosomes from their father and half from their mother. Sometimes, the genes from each parent, such as hair colour, do not match. In these cases, the dominant gene wins and is inherited by the child.

Genome is all the genetic material contained in a full set of chromosomes. In 1990, an international project began to identify all the thousands of genes and the sequences of the nearly 3,100 million base pairs in human DNA. The identification was completed in 2003, but research continues to understand more about how genes work and how gene therapy might be able to replace faulty genes.

Crime-fighting agencies use DNA fingerprinting to trace identities of criminals and victims.

A DNA fingerprint is constructed by first taking a sample of DNA from a person’s blood, hair, or a swab inside their mouth. A complex series of processes sees DNA extracted from the nucleus of a cell, cut into smaller pieces, processed, and imaged using X-ray photography. New DNA samples can be compared to those already held in order to try to find a match.

Scientists are able to produce copies of individual genes, cells, and, in some cases, entire organisms, in processes called cloning. Scientists have cloned many animals, including sheep and cats. These creatures were created using somatic cell nuclear transfer. This is where the cell nucleus from an adult animal is placed inside an egg cell that has had its own nucleus removed.



Calories measure energy and can be used to describe any fuel from petrol to bread. One calorie is the amount of energy required to raise the temperature of one gram (0.035 ounces) of water by one degree Celsius (1.8 degrees Fahrenheit). Food labels often quote energy content in kilocalories (kcal), because food is so rich in energy that it makes more sense to label 1,000 calories at a time.

The number of calories in any given item of food is calculated by measuring how much energy is released when a substance is burned. Inside our bodies, molecular machinery is responsible for burning the fuel we eat, but in the lab, using a spark gives the same result. The traditional method of calorie calculation is to put the food inside a sealed unit known as a bomb calorimeter.

The food is surrounded by an atmosphere of oxygen to ensure it will burn well, and the container is sealed and surrounded by a known volume of water. A spark ignites the food inside and allows it to burn until it is reduced to charcoal, releasing all of the energy contained inside.

The energy is converted to heat, which in turn raises the temperature of the water. By measuring the water’s temperature change, you can then find out exactly how much energy has been released and calculate the calories from there.

Today, many food manufacturers use a different system to create nutritional labels; instead of burning the food item whole, they simply add up the calories of the different components, such as fats, carbohydrates and proteins.



Stars twinkle when there appear to be variations in their brightness. Astronomers call this phenomenon atmospheric scintillation, and it’s caused by motion in the atmosphere.

Specifically, changes in atmospheric temperature cause small fluctuations in the air’s density. As starlight passes through the atmosphere, it’s refracted or slightly alters direction, creating a twinkling effect.

This is more obvious when viewing stars closer to the horizon because there’s a thicker layer of atmosphere. Astronomers compensate for atmospheric scintillation by using special adaptive optics on the most sophisticated telescopes. Space-based observatories like the Hubble also allow us to view stars and other objects without atmospheric scintillation.