Astronomy The Science of Stars and much more.
                     Astronomy: The Science of 
Stars and much more
INTRODUCTION
• Astronomy is the study of the sun, moon, stars, planets, comets, gas, galaxies, gas, 
dust and other non-Earthly bodies and phenomena. 
Source: www.space.com
The Scope Of Astronomy
• Since the late 19th century, astronomy has expanded to include astrophysics, the 
application of physical and chemical knowledge to an understanding of the nature of 
celestial objects and the physical processes that control their formation, evolution, 
and emission of radiation. 
Source: www.space.com
Study of the stars
• The measurable quantities in stellar astrophysics include the externally observable 
features of the stars: distance, temperature, radiation spectrum and luminosity, 
composition, diameter, mass, and variability in any of these. 
Source: www. britannica.com
Model the structure of stars 
• Theoretical astrophysicists use these observations to model the structure of stars and 
to devise theories for their formation and evolution. 
• Positional information can be used for dynamical analysis, which yields estimates of 
stellar masses.
Source: www. britannica.com
Star formation and evolution
• The range of physically allowable masses for stars is very narrow. If the star’s mass 
is too small, the central temperature will be too low to sustain fusion reactions. The 
theoretical minimum stellar mass is about 0.08 solar mass. 
Source: www. britannica.com
Measuring observable stellar properties
• The measurable quantities in stellar astrophysics include the externally observable 
features of the stars: distance, temperature, radiation spectrum and luminosity, 
composition (of the outer layers), diameter, mass, and variability in any of these. 
Source: www. britannica.com
Study of the solar system
• The solar system took shape 4.57 billion years ago, when it condensed within a large 
cloud of gas and dust. 
• Gravitational attraction holds the planets in their elliptical orbits around the Sun.
Source: www. britannica.com
Lunar exploration
• During the U.S. Apollo missions a total weight of 381.7 kg (841.5 pounds) of lunar 
material was collected; an additional 300 grams (0.66 pounds) was brought back by 
unmanned Soviet Luna vehicles. 
Source: www. britannica.com
Investigations of the smaller bodies
• More than 500,000 asteroids with well-established orbits are known, and thousands 
of additional objects are discovered each year. 
• Hundreds of thousands more have been seen, but their orbits have not been as well 
determined.
Source: www. britannica.com
Study of the Milky Way Galaxy
• Galaxies are much larger systems of stars and usually include clouds of gas and 
dust.
• The solar system is located within the Milky Way Galaxy, close to its equatorial plane 
and about 8 kiloparsecs from the galactic centre. 
Source: www. britannica.com