STARS....

Are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies.

STARS:of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

Is define as a luminous ball of chiefly Hydrogen, producing its own light and other radiation by atomic fusion

( Hydrogen to Helium) and its stellar components held together by its own gravity.

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

Consequently, the study of the birth, life, and death of stars is central to the field of astronomy

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

Basic Characteristics of Star:

Compose of 90% of galaxiesEmissions of all forms of particle and electro magnetic radiations resulting from atomic fusion of hydrogen to Helium

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

Production of steady light although when viewed on earth, starlight's seem to twinkle resulting from the refraction of light by movement of the earth’s atmospheric gases.

Brightness is expressed in magnitude. Apparent magnitude refers to the observed brightness of a star or star brightness based on distance from the viewer. Absolute magnitude refers to star brightness based on actual energy produced.Stars moved in space following definite orbits at an average speed of 100 miles/sec.

The colour of the stars raging from the deepest red through all intermediate shades of orange and yellow to an intense white- blue depends directly on their temperature. The coolest stars are red ( Approximately 3,500 ˚C) and the hottest stars are blue ( approximately 500,000˚C).Stars undergo life cycles

=A star system or stellar system is a small number of stars which orbit each other,  bound by gravitational attraction. A large number of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems. Star systems are not to be confused with Planetary system, which include planets and similar bodies.

What is Stellar System?

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

The Sun

The Sun is the star at the center of the Solar System. It is almost spherical and consists of hot plasma interwoven with magneticfields It has a diameter of about 1,392,684 km (865,374 mi),  around 109 times that of Earth, and its mass (1.989×1030 kilograms, approximately 330,000 times the mass of Earth) accounts for about 99.86% of the total mass of the Solar System.Chemically, about three quarters of the Sun's mass consists of hydrogen, whereas the rest is mostly helium. The remaining 1.69% (equal to 5,600 times the mass of Earth) consists of heavier elements, including oxygen, carbon, neon and iron, among others.

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

Different Kinds

of Stars:

1. Yellow Dwarf StarsLifetime: 4 - 17 billion yearsEvolution: early, middleTemperature: 5,000 - 7,300 °CSpectral Types: G, FLuminosity: 0.6 - 5.0Radius: 0.96 - 1.4Mass: 0.8 - 1.4Prevalence: 10%The Sun, Alpha Centauri A, and Kepler-22 are yellow dwarfs.

These stellar cauldrons are in the prime of their lives because they are burning hydrogen fuel in their cores. This normal functioning places them on the `main sequence', where the majority of stars are found. The designation `yellow dwarf' may be imprecise, as these stars typically have a whiter color. However, they do appear yellow when observed through the Earth's atmosphere.

2. Orange Dwarf StarsLifetime: 17 - 73 billion yearsEvolution: early, middleTemperature: 3,500 - 5,000 °CSpectral Types: KLuminosity: 0.08 - 0.6Radius: 0.7 - 0.96Mass: 0.45 - 0.8Prevalence: 11%Alpha Centauri B and Epsilon Eridani are orange

dwarf stars. These are smaller, cooler, and live longer than yellow dwarfs like our Sun. Like their larger counterparts, they are main sequence stars fusing hydrogen in their cores.

3. Red Dwarf StarsLifetime: 73 - 5500 billion yearsEvolution: early, middleTemperature: 1,800 - 3,500 °CSpectral Types: MLuminosity: 0.0001 - 0.08Radius: 0.12 - 0.7Mass: 0.08 - 0.45Prevalence: 73%Proxima Centauri, Barnard's Star and Gliese 581 are all red

dwarfs. They are the smallest kind of main sequence star. Red dwarfs are barely hot enough to maintain the nuclear fusion reactions required to use their hydrogen fuel. However, they are the most common type of star, owing to their remarkably long lifetime that exceeds the current age of the universe (13.8 billion years). This is due to a slow rate of fusion, and an efficient circulation of hydrogen fuel via convective heat transport.

4. Brown DwarfsLifetime: unknown (long)Evolution: not evolvingTemperature: 0 - 1,800 °CSpectral Types: L, T, Y (after M)Luminosity: ~0.00001Radius: 0.06 - 0.12Mass: 0.01 - 0.08Prevalence: unknown (many)Brown dwarfs are substellar objects that never accumulated enough

material to become stars. They are too small to generate the heat required for hydrogen fusion. Brown Dwarfs constitute the midpoint between the smallest red dwarf stars and massive planets like Jupiter. They are the same size as Jupiter, but to qualify as a brown dwarf, they must be at least 13 times heavier. Their cold exteriors emit radiation beyond the red region of the spectrum, and to the human observer they appear magenta rather than brown. As brown dwarfs gradually cool, they become difficult to identify, and it is unclear how many exist.

5. Blue Giant StarsLifetime: 3 - 4,000 million yearsEvolution: early, middleTemperature: 7,300 - 200,000 °CSpectral Types: O, B, ALuminosity: 5.0 - 9,000,000Radius: 1.4 - 250Mass: 1.4 - 265Prevalence: 0.7%Blue giants are defined here as large stars with

at least a slight blueish coloration, although definitions do vary. A broad definition has been chosen because only about 0.7% of stars fall into this category.

6. Red Giant StarsLifetime: 0.1 - 2 billion yearsEvolution: lateTemperature: 3,000 - 5,000 °CSpectral Types: M, KLuminosity: 100 - 1000Radius: 20 - 100Mass: 0.3 - 10Prevalence: 0.4%Aldebaran and Arcturus are red giants. These stars are in a

late evolutionary phase. Red giants would previously have been main sequence stars (such as the Sun) with between 0.3 and 10 solar masses. Smaller stars do not become red giants because, due to convective heat transport, their cores cannot become dense enough to generate the heat needed for expansion. Larger stars become red supergiants or hypergiants.

7. Red Supergiant StarsLifetime: 3 - 100 million yearsEvolution: lateTemperature: 3,000 - 5,000 ºCSpectral Types: K, MLuminosity: 1,000 - 800,000Radius: 100 - 1650Mass: 10 - 40Prevalence: 0.0001%Betelgeuse and Antares are red supergiants. The

largest of these types of stars are called red hypergiants. One of these is 1650 times the size of our Sun (NML Cygni), and is the largest known star in the universe. NML Cygni is 5,300 light years away from the Earth.

8. White DwarfsLifetime: 1015- 1025 yearsEvolution: dead, coolingTemperature: 4,000 - 150,000 ºCSpectral Types: D (degenerate)Luminosity: 0.0001 - 100Radius: 0.008 - 0.2Mass: 0.1 - 1.4Prevalence: 4%Stars less than 10 solar masses will shed their outer layers

to form planetary nebulae. They will typically leave behind an Earth-sized core of less than 1.4 solar masses. This core will be so dense that the electrons within its volume will be prevented from occupying any smaller region of space (becoming degenerate). This physical law (Pauli's exclusion principle) prevents the stellar remnant from collapsing any further.

9. Black DwarfsLifetime: unknown (long)Evolution: deadTemperature: < -270 °CSpectral Types: noneLuminosity: infinitesimalRadius: 0.008 - 0.2Mass: 0.1 - 1.4Prevalence: ~0%Once a star has become a white dwarf, it will slowly

cool to become a black dwarf. As the universe is not old enough for a white dwarf to have cooled sufficiently, no black dwarfs are thought to exist at this time.

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

BLACk DWARFS

10. Neutron StarsLifetime: unknown (long)Evolution: dead, coolingTemperature: < 2,000,000 ºCSpectral Types: D (degenerate)Luminosity: ~0.000001Radius: 5 - 15 kmMass: 1.4 - 3.2Prevalence: 0.7%When stars larger than about 10 solar masses exhaust

their fuel, their cores dramatically collapse to form neutron stars. If the core has a mass above 1.4 solar masses, electron degeneracy will be unable to halt the collapse. Instead, the electrons will fuse with protons to produce neutral particles called neutrons, which are compressed until they can no longer occupy a smaller space (becoming degenerate).

Life Cycle of a Star Stars are formed in clouds of gas and dust, known as nebulae. 

Nuclear reactions at the centre (or core) of stars provides enough energy to make them shine brightly for many years. The exact lifetime of a stardepends very much on its size. Very large, massive stars burn their fuel much faster than smaller stars and may only last a few hundred thousand years. Smaller stars, however, will last for several billion years, because they burn their fuel much more slowly.Eventually, however, the hydrogen fuel that powers the nuclear reactions within stars will begin to run out, and they will enter the final phases of their lifetime. Over time, they will expand, cool and change colour to become red giant stars. The path they follow beyond that depends on the mass of the star.

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.