OBSERVING THE NIGHT SKY

 

WHAT DO WE SEE IN THE NIGHT SKY

Sun, Moon, Planets and their moons, Comets, Asteroids Meteors, Nebula and Stars.

WHAT DO WE SEE IN THE SKY FROM EARTH

During daylight we only see our Sun and sometimes the moon.At night we see all the shining objects mentioned above against the dark sky.

HOW DO WE FIND STARS IN THE SKY

Some of the brighter stars appear to form groups in the sky, these we call constellations. Most constellations were named a very long time ago by the Greeks or Arabs. People thought they could see the shapes of animals or their gods and named the constellations after them. In most cases it is very hard to imagine how they saw the shape that the star pattern is supposed to represent but we still use the same names today. In the first 3 or 4 months of the year we see the winter constellations which include three very beautiful and interesting ones. These are called ORION the hunter, ANDROMEDA a Greek goddess and TAURUS the Bull.

Constellations are not necessarily associations of stars, some groups of stars are not groups at all but are just in the same line of sight as seen from Earth. If you were able to view what we call a constellation from some other part of the sky (say looking at Orion from a planet orbiting a star in Taurus) it would look very different from the way we see it from Earth. Some stars appear bright in our sky because they are close to us, others may appear bright because they are giant bright stars. Some dim stars are actually very bright but are a very long way from us.

We as humans always like to put things into groups so that we can sort them out in our minds, we do this with everything even with people so we do it with stars too. We are also quite good at remembering shapes and we often have good imaginations so just as we can see shapes of rabbits and elephants in the clouds it is not surprising therefore that we see shapes in the stars, these are the Constellations.To find your way around the sky, one other constellation can always be used to find your bearings, this is URSA MAJOR the Great Bear or Plough. Ursa Major is always visible in the northern sky, it is bright and easy to find. It is shaped like a saucepan with four stars forming the square shape of the pan and three more stars forming the handle. The two stars of the pan furthest from the handle are called the pointers because an imaginary line drawn through them points to the north star called Polaris. The pole star does not move in the sky and is always north of the point directly above us. By finding Polaris and turning around half a turn we will be facing south, and will then be able to use our star maps.

 

WHY DO STARS APPEAR TO MOVE ACROSS THE NIGHT SKY

There are actually two different reasons why stars appear to move across our sky. The first is because the Earth is spinning and second because the Earth itself is moving around the Sun.

As the Earth travels around the sun (once a year), it is as if we are sitting on a Waltzer ride at the funfair. If the whole Waltzer moved around on its track with the cars not spinning, we would see everything around the ride appear to be sweeping past once with every revolution.  Standing on the surface of Earth, as it makes its journey around the Sun we see the stars passing by until after a whole revolution around the Sun, taking a year, we will have seen all the stars pass by.

At the same time as the Earth is moving around the sun it is spinning on it own axis (once a day). So just as the Waltzer cars spin, we see the the other fairground attractions pass by, then we see the centre of the Waltzer structure. On one turn of the car we might see the Big Wheel the next turn of the car we see the fairground a little further around the track with the Dodgems in view. Similarly as the Earth spins we can see the stars at that position in the orbit around the Sun by night and the Sun at the centre of the ride during the day. Each day the Earth will have moved one 365th of its orbit around the Sun. The result is that we see some different stars coming into view as the Earth spins from night to night and other stars move out of view. The fairground behind the centre of the Waltzer is blocked from our view just as the stars are invisible in the direction of the Sun because of the glare of daylight.

If the waltzer had no roof, the sky overhead would appear to be spinning around a point directly above the car. This area of sky would always be visible to us no matter where the car was on the track. This is the same for the stars around the north star Polaris. Because Polaris is close to the point in the sky directly above the axis of spin of the Earth (the north pole) it is always visible. The stars within 40 degrees of Polaris appear to rotate around it and do not set below the horizon, these stars are said to be ‘circumpolar’. Stars further than 40 degrees from Polaris disappear below the horizon for part of the year and reappear at the same time every year.

Because the Earth spins half a turn in a night, a star visible low in the east early in the evening will appear to rise and move in an arc across the southern sky and set in the west before morning. Stars in the centre of the southern sky will disappear below the western horizon halfway through the night. Other stars will rise in the east all through the night.All the stars that can be seen are always in the sky at some time during the 24 hour day but some rise while the sun is in the sky and are hidden by the glare of the bright sky. If we could block out the sun and darken the daytime sky we would see the sky still filled with stars. The only stars we could not see would be those behind the Sun or those blocked out by the Earth beneath us.

 

THE CONSTELLATIONS

There are about 100 constellations altogether with 56 that able to be seen from Britain but some of these we can only see parts of them. Below are charts showing the winter and summer night skies ans a list of the northern constellations in alphabetic order. Some of these constellations have the English meaning of the name included and some also have the names of some well known stars located in the constellation.

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The Winter Constellations
The Summer Constellations

 

CONSTELLATIONS VISIBLE FROM BRITAIN

NAME

NAME MEANS

BRIGHT STARS

Andromeda

Andromeda

 

Aquarius

The Water-Bearer

 

Aquila

The Eagle

Altair

Aries

The Ram

Hamal

Auriga

The Charioteer

Capella

Bootes

The Herdsman

Arcturus

Camelopardalis

The Giraffe

 

Cancer

The Crab

 

Canes Venatici

The Hunting Dogs

Cor Caroli

Canis Major

The Great Dog

Sirius

Canis Minor

The Little Dog

Procyon

Capricornus

The Sea Goat

 

Cassiopeia

Cassiopeia

 

Cepheus

King Cepheus

 

Cetus

The Whale

 

Coma Berenices

Brenice’s Hair

 

Corona Borealis

The Northern Crown

Alphekka

Corvus

The Crow

 

Crater

The Cup

 

Cygnus

The Swan

 

Delphinus

The Dolphin

 

Draco

The Dragon

 

Equuleus

The Foal

 

Eridanus

The River

Achernar

Gemini

The Twins

Pollux, Castor

Hercules

Hercules

 

Hydra

The Watersnake

Alphard

Lacerta

The Lizard

 

Leo

The Lion

SpringRegulus

Leo Minor

The Little Lion

 

Lepus

The Hare

 

Libra

The Balance

 

Lynx

The Lynx

 

Lyra

The Lyre

 

Monoceros

The Unicorn

 

Musca

The Fly

 

Ophiuchus

The Serpent-bearer

Rasalhague

Orion

Orion the Hunter

WinterRigel, Betelgeux

Pegasus

The Flying Horse

 

Perseus

Perseus

Mirphak, Algol

Phoenix

The Phoenix

 

Pisces

The Fishes

 

Piscis Austrinus

The Southern Fish

Fomalhaut

Sagitta

The Arrow

 

Sagittarius

The Archer

 

Scorpius

The Scorpion

Antares

Sculptor

The Sculptor

 

Scutum

The Shield

 

Serpens

The Serpent

 

Taurus

The Bull

Aldebaran

Triangulum

The Triangle

 

Triangulum Australe

The Southern Triangle

 

Ursa Major

The Great Bear (Plough) (Big Dipper (in the U.S.))

 

Ursa Minor

The Little Bear

Polaris (Pole Star)

Virgo

The Virgin

Spica

Vulpecula

The Fox

 

 

NOTE : Constellations shown in bold print are circumpolar from Britain.

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