Annapaola & Francesca Donateo present. ASTRONOMY.

Annapaola & Francesca Donateo

present

ASTRONOMY

What’s astronomy?It’s the branch of geography which helps us to get acquainted with the

sky. It is also the study of the sun, the moon, the planets and other

astronomical bodies. It includes learning about the Earth, because the

Earth, too, is a planet.

When we observe the sky on a clear, dark night, the first thing that we note are the stars, seen as little pinpoints of light.But …

What are stars?

StarsStars are astronomical body of

gaseous composition, animated by nuclear reactions, able to give out

energy in the form of electromagnetic radiations. They are

made of helium and hydrogen.

Often stars appear grouped in pictures that we called constellations. However stars aren’t at the same distance … it’s

only an illusion of the observer. The most important constellations are …

OrionOrion is a

constellation formed by 130 stars

and the alignment of three of them

form the so-called Orion’s belt.

Ursa Maiorand Ursa Minor

Ursa Major is a constellation of typical boreal skies, its seven brightest stars, grouped in the famous Big Dipper asterism, are visible throughout the year in the northern hemisphere.

Ursa Minor is a constellation of the northern sky. It is especially known because within it lies the north celestial pole, although its

position is subject to a continuous, slow movement due to the precession of the Earth's rotation. The Little Dipper is easily

identifiable because, once detected the Big Dipper, you can reach the Pole Star, the brightest star in Ursa Minor

CassiopeiaCassiopeia is a northern

constellation, representing

Cassiopeia, the legendary queen of

Ethiopia. The constellation is easily

recognized by its shape W or M.

Observing the sky, it seem that everything revolve around the Earth, that appeared to be the motionless of the universe. But today we know that only the moon revolves around the planet. The Earth itself travels around the Sun with other seven planets in the Solar System.

The Sun is one of numerous stars that form our galaxy, called the Milky Way.

The Sun is the centre of the Solar System, around which everything revolves. It is also the only

source of energy, the same that terrestrial organisms

exploit to perform their normal activities.

It’s an enormous discus of stars (100 milliards) long about 100 000 light-years and thick 10 000 light-

years. It’s characterized by a central swelling , called galactic nucleus,

from which depart arms, where the density of the stars is higher.

Milky way

The solar system

The solar system is the planetary system formed by a variety of

celestial bodies kept in orbit by the force of gravity of the Sun, the Earth

also belongs to it. Is composed of eight planets, by their natural

satellites, five dwarf planets and billions of small bodies. The planets

that compose it are …

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Thanks for your attention.

The end