CONCEPTS

 

The physical sciences seek to understand matter and its relationship with energy.

Cosmology is the study of the universe as a whole.

Astronomy is the study of objects in the universe.

People have looked at the stars for thousands of years. Most of what we know about the universe comes from what we see - in other words, from light.

All light is produced by atoms!

Light travels at a speed of 299,792.458 kilometers per second (300,000 km/sec or 186,000 miles per second). Because of the great distances involved, the light that reaches us from distant objects in the universe has been traveling a long time. Light from the Sun, for instance, takes eight minutes to reach us, so that we see the Sun as it was eight minutes ago. Astronomical distances are often expressed in light-years.

The Universe has been expanding since the time of the Big Bang , spreading the available energies over greater distances. Don't think of the Big Bang as an explosion that sent bits of the cosmos in all directions into a preexisting space. A more accurate model is an expanding balloon. If you think of space as the surface of the balloon, and the galaxies as dots of ink on that surface, the recession of the galaxies (moving away from one another) is due to the expansion of space, not the distribution of debris through space.

A combination of today's best theories about the life of the Universe assumes maximum concentrations of energies at the point of the Big Bang.

The Universe includes .... well, everything!

 
Constellations are patterns in the stars as seen from the Earth. The International Astronomical Union (IAU) officially recognizes 88 constellations. There are definitive boundaries between constellations, which extend out beyond the star figures, so that every star, nebula, or galaxy, no matter how faint, now lies within the limits of one constellation. For today's astronomer, constellations refer not so much to the patterns of stars, but to precisely defined areas of the sky.

The constellations in the diagram above represent the signs of the zodiac. These particular constellations are used in astrology, which is something less than an exact science.

Different constellations are visible in different places in the sky as the Earth moves around the sun. Star charts can be used to locate the constellations.

Some Basic Constellations:

CONCEPTS (continued)
 

As our galaxy rotates, the Sun completes a circuit of the galaxy about every 240 million years. Obviously, The Milky Way covers an enormous amount of space. Since galaxies are so large, how many can there possible be?

This picture was taken with the Hubble telescope. The bright white object marked with the arrow is a star in our galaxy. All other objects in the picture are galaxies!

If a dime is held 75 feet in front of your eyes, it would cover the area of the sky in this picture.

Our Sun is one of about 1 X 1011 (100 billion) stars located in the rotating, spiral-shaped galaxy we call the Milky Way. The Sun contains more than 99.8% of the total mass of our solar system, which is located about two thirds of the way out on one of the arms of the galaxy, about 30,000 light years from the center.

Facts about Our Sun.

 
There are several classification systems for stars. All are based on some physical characteristic; such as diameter, mass, color, or temperature.

One simple system uses a combination of characteristics to designate star types by letters:

  • O - 30,000 to 60, 000 Kelvins - Blue - 60 solar masses
     
  • B - 10,000 to 30, 000 Kelvins - Blue-White - 18 solar masses
     
  • A - 7,500 to 10, 000 Kelvins - White - 3.2 solar masses
     
  • F - 6,000 to 7,500 Kelvins - Yellow-White - 1.7 solar masses
     
  • G - 5,000 to 6, 000 Kelvins - Yellow - 1 solar mass

    Our Sun is a G-Type Star

  • K - 3,500 to 5, 000 Kelvins - Orange - 0.8 solar mass
     
  • M - 2,000 to 3,500 Kelvins - Red - 0.3 solar mass
OH, BE A FINE GIRL, KISS ME

 

Analyzing the Light From Stars

Lines in the spectrum indicate the presence of specific chemical elements in the Sun.

The spectra of other stars are similar, indicating the same elements are present in those stars.

Using the spectroscopic signatures of elements from the light of stars and other celestial objects, scientists have estimated that the universe is nearly 75% hydrogen and nearly 25% helium. Only 1 to 2 percent is made up of all the other elements together.

Quiz