The Milky Way

The Milky Way is a large band of stars, dust and gas that make up our galaxy. It contains billions of stars. Our sun and the solar system is only one of them. The Milky Way is only one of billions of galaxies that make up our universe. It has a diameter of about 100,000 light years and is as old as the universe itself. The name probably refers to how we see our galaxy - a white blurry band that looks like spilled milk.

The Milky Way has the shape of a thin disk with six spiral arms coming out of a bulge in the center . This bulge consists of a cluster of large stars, gas and dust as well as a strong magnetic field. The whole galaxy rotates around this inner bar of stars. New stars are constantly formed around the spiral arms. Most of the stars in our galaxy are red dwarfs, cold stars that are much smaller than our sun.

 The galaxy gets flatter towards the edges. The center of the Milky Way consists of a black hole; an invisible object that has such a strong gravitational pull that not even light cannot escape. The galaxy is surrounded by a gigantic halo made up of old stars and gas that stretches hundreds of thousands of light years into the universe.

Our solar system is located on the inner edge of one of the spiral arms, about 30,000 light years from the centre. It completes one orbit around the centre about every 240 million years.

 Astronomer Edwin Hubble was the first to find out that the Milky Way is only one of many galaxies in our universe. The nearest is Andromeda, which is often referred to as our sister galaxy. It is estimated that in about 4 billion years the Milky Way and Andromeda will collide.

Words

• astronomer = a scientist who studies the sky and the stars
• bar = band
• billion = a thousand million
• blurry = unclear
• bulge = a thick curved mass
• cluster = very many
• collide = crash
• constantly = always
• contain = is made up of
• diameter = the distance from one end of a circle to the other
• disk = round flat shape
• dust = very small particles of dirt
• dwarf = a creature that looks like a very small man
• edge = border, rim
• escape = get away
• estimate = guess, think
• gravitational pull = the force that pulls something towards it
• halo = circle of light
• invisible = something that cannot be seen
• light years = the distance that light travels in one year ( about 6 000 000 000 000 miles)
• located = exists, can be found
• orbit = to move around an object in a circle
• refer = is about
• rotate = to go around
• spill = when a liquid flows over the edge of a container by accident
• spiral = to move in a curve that gets nearer to or farther from the center as it goes around
• stretch = reach from one place to another
• surrounded = around it

Lightning

Lightning 

 Lightning is a form of electricity that is set free during a storm. Energy is suddenly released in a cloud when charges are built up. Although lightning is most common in tropical and subtropical regions, it can happen wherever hot air mixes with cold air. Thunderstorms produce about 8 million lightning bolts a day.

For a long time lightning was a big mystery. Ancient people thought that god was punishing people by sending a bolt of lightning down to Earth.

 How lightning forms

Water droplets and ice crystals in a cloud have electric charges, positive and negative ones. Lightning happens when too many negative charges build up in a cloud and positive charges develop on the ground.

The particles want to meet and race towards each other. A flash of lightning is a sign of this meeting. Such a charge of light can be very hot, up to 20,000 degrees Celsius. It can be up to 5 km long. Large clouds produce more electric charges and eventually a very strong electrical current.

Lightning can also occur between two clouds or within a single cloud. In rare cases negative charges can form on the ground and lighting moves upwards, as is the case when a rocket starts.
Lightning strikes very quickly, several times within a second, but single bolts of lightning are impossible to see with a naked eye. A series of such bolts appear as a single flash.

Thunder accompanies lightning. It forms when electricity travels quickly through the air and starts vibrating. The hot air surrounding a bolt of lightning causes the air to expand, causing noise.

 Effects

Lightning can do damage to buildings, cars or other objects when it hits.  It can also kill or injure human beings. During a thunderstorm people should stay away from doors, windows and electrical devices.  You should also stay away from phones and wires because lightning can travel through them. When you’re in the open do not try to protect yourself by hiding under a tree.

You can protect your house or other buildings surrounding your home by installing a lightning rod on the roof. It attracts the lighting that would otherwise hit the building and leads it to the surface.

Lightning can also have positive effects. It produces nitrates and other compounds when it is created in the air. These nutrients fall down to Earth and enrich the soil for good farming.

Words

• accompany = go with; to happen together with
• although = while
• ancient =  old
• attract = pull towards itself
• bolt =lightning that appears as a white line in the sky
• charge = here: small amount of electricity 
• common = often seen
• damage = destroy
• develop = grow
• device = object, tool, machine
• droplet = small drop
• electrical current = flow of electricity
• enrich = to make better
• eventually = in the end
• expand = become larger
• flash = white burst
• human being = person
• injure = hurt
• install = put in, set up
• lightning rod = metal wire that is fixed to the top or side of a building  and is used to protect the it from lightning
• nitrate = substance that has nitrogen and oxygen in it and is used to make plants grow better
• nutrient = chemical or food that gives plants what they need to grow
• occur = happen
• otherwise  = or else
• punish = to make someone suffer because they have done something wrong
• race = move quickly
• rare = not very often
• release = set free
• series = one after the other
• several = many
• sign = signal
• soil = top layer of earth on which plants grow
• suddenly = unexpectedly, all of a sudden
• surface = the top part of something
• surrounding = around
• towards = in the direction of
• wire = thin cable of metal that can carry electricity

Astronomy

 

Astronomy

Astronomy is about studying space, the universe, stars and the planets in our solar system. Astronomers are scientists who try to find answers to questions relating to our universe. They observe planets, faraway stars and galaxies as well as certain events that occur in space. They examine the structure of the universe and try to find out how it all began.

Ancient Astronomy

Astronomy has been around for thousands of years.  In ancient times, people observed the sun and the stars on a daily basis. They planted crops and held certain events relating to the movement of objects in the sky.

Ancient civilizations, like the Greeks and Romans, however did not have the instruments that later generations had. They had to observe the skies and stars with their naked eye.  It helped them navigate the seas and guide them to other places.

They saw that stars were arranged in patterns that looked like humans or animals.
In ancient times, people thought that the Earth was the centre of the universe and that everything revolved around it. Towards the end of the Middle Ages some astronomers were not quite convinced about this  theory. In the early 16th century Nicolaus Copernicus, a Polish astronomer, was the first to show that in fact the sun was the centre of the solar system and planets revolved around it. Almost a century later Italian astronomer Galileo used the first telescope to observe space. His studies supported Copernicus’ theories. German mathematician Johannes Kepler proved that planets travel around the sun in elliptical paths. Isaac Newton used Kepler’s findings to explain how gravity worked.

 Modern astronomy

The discovery of the telescope changed the way scientists could observe space. While ancient people only were able to see objects near Earth, telescopes were able to find Uranus, Neptune and Pluto, the distant planets of our solar system.

Astronomers also found that an asteroid belt moves around the sun between the Earth and Mars. With the help of powerful telescopes, they were able to  map the surface of the moon and other planets in great detail.

Modern astronomy uses powerful telescopes on earth to see objects far away from our solar system. It also relies on images sent to earth from orbiting telescopes, like the Hubble Space Telescope, which has been in operation since 1990.

Unmanned spacecraft that land on the moon and other planets give astronomers large amounts of data and images that they can use for their work. Astronomers also study samples of rocks that spacecraft have brought back to Earth.

Today, astronomers use computers to simulate movements and events that may happen in space. For example, they can predict how close an asteroid can come to earth or when certain comets appear.

Astronomers measure distances in light years – how far light can travel in one year, which is about 6 trillion miles (9.4 trillion km). They have found out that our galaxy, the Milky Way, has a diameter of 100,000 light years. The nearest star is Proxima Centauri, about four light years away from Earth.