Astronomy:
Stars
What’s a Star ??
Man has always lifted his head towards the
black sky to observe it
it was always fascinated by the stars that
shine above him
First he considered that stars were just
spots that shone in the sky and were almost
essential to the navigation…
but When he discover the telescope the
open view change and men know what
means a star ! ( suns )
So why Do the stars shine? and how can it
help us to navigate in the huge seas?
The Picture Bellow represent a night
dark sky full of stars
The Definition of a Star
A star is a massive, luminous sphere of
plasma Held together by gravity. The
nearest star to Earth is the Sun, Which is
the source of MOST of the energy on the
planet. Some other stars are visible from
Earth falling on the night When They are
not obscured by atmospheric phenomena,
Appearing as a multitude of fixed luminous
point Because of Their immense distance.
Historically, The most prominent stars on
the celestial sphere Were grouped together
into constellations and asterisms, and the
brightest stars Gained proper names.
Extensive catalogs of stars Have Been
assembled by astronomers, Which Provide
STANDARDIZED star designations.
Constellation
In modern astronomy, a constellation is an Internationally
Defined area of the celestial sphere. These are grouped
around asterisms Areas (Themselves Which are
Generally Referred to in non-technical language as
"constellations") Which patterns are Formed by
prominent stars Within apparent proximity to one another
on Earth's night sky.
Constellation Of Orion
Constellation of Lion
Constellation of the fish
Constellation of the Draco
Chapter 2
The Formation of Star (!)
Différent Stars in
diffrent ages
The Birth Of a Star
Star formation
Star formation is the process by which dense regions within molecular
clouds in interstellar space, commonly referred to as "stellar
nurseries", collapse into spheres of plasma to form stars. As a branch
of astronomy, star formation includes the study of the interstellar
medium and giant molecular clouds (GMC) as precursors to the star
formation process, and the study of young stellar objects and planet
formation as its immediate products. Star formation theory, as well as
accounting for the formation of a single star, must also account for the
statistics of binary stars and the initial mass function.
Nebulas the nursuries of the
formation of stars
Orion Nebula
Nebula of the Eye Cat
Nebula of the fox
The life of a star
The End of a Star
How it Becomes When it’s not a
massive Star
Characteristics
of a star
•
Age :Most stars are between 1 billion and 10 billion years old. Some stars may even be close to 13.8
billion years old—the observed age of the universe. The oldest star yet discovered, HE 1523-0901, is an
estimated 13.2 billion years old.
•
Chemical composition : When stars form in the present Milky Way galaxy they are composed of about
71% hydrogen and 27% helium,
•
Magnetic field: The magnetic field of a star is generated within regions of the interior
where convective circulation occurs. This movement of conductive plasma functions like a dynamo,
generating magnetic fields that extend throughout the star.
•
ClassificationSurface
Different Stellar Classes[134]ClassTemperatureSample starO33,000 K or moreZeta OphiuchiB10,500–
30,000 KRigelA7,500–10,000 KAltairF6,000–7,200 KProcyon AG5,500–6,000 KSunK4,000–
5,250 KEpsilon IndiM2,600–3,850 KProxima CentauriMain article: Stellar classification
The Sun Composition
Conclusion
• Thanks For being With till now