GALAXIES AND STARS

Galaxy – grouping of millions to trillions of stars all gravitationally bound together.
Galaxies exist in groups called clusters and even larger groups, known as superclusters.

Globular clusters – large sphere clusters of old stars found in outlying regions of galaxies.

Voids – huge regions in the universe where very few galaxies reside.

 
Andromeda Galaxy

MAIN TYPES OF GALAXIES

Spiral galaxies (ex. Milky Way, Andromeda) –
consist of a central nuclear bulge and arched spiral arms of stars that trail beyond the galaxy.

Barred spiral galaxies (ex. )
similar to spiral galaxies, although these have a bar of stars crossing the bulge.

Elliptical galaxies (ex. )
elliptical or round in shape and contain no arms of stars. Most of these consist mostly of low mass, long life stars.

Interaction between galaxies may change the structure of them. This is believed to be the theory of how lenticular (disk shaped) and irregular (ex. Large Molecular Cloud) galaxies formed.

This is the spiral galaxy NGC-3992, in the star constellation of URSA MAJOR. Patchy areas of bright blue stars trace out the loose spiral to help natural forces determine its shape. Global clusters, as well as indiviual stars and planets, owe their impressive spherical symmetry to gravity's relentless inward pull. Spiral galxies rank among the most striking forms because of their estravagant shapes and variations.

TYPES OF STARS

1. Main sequence stars - stars burning or fusing hydrogen into helium in their core (90% of stars in solar system)

2. Giants (includes red giants) and Supergiants - large and hence more luminous stars.(-1% of stars in solar system)

3. White Dwarfs - small hot stars at their end stages, like our sun (remnants of supernovas, about 9% of stars in solar system)

This is said to be the hellish interior of an exploding star, scientists can learn a great deal about about how stars evolve by studying the supernova. As it explodes, it suddenly increases in brightness, by a factor of billons and after a few weeks fades out, to wane amongst its neighboring stars. It may be blacked out but can remain years after the blast, until it's nothing but a dim white dwarf.

OB ASSOCIATION

(Hertsprung-Russell Diagram, classifies stars by spectra & stellar temp.) OBAFGKM (Oh, be a fine guy, kiss me)

TOTAL ECLIPSE
Suddenly it's there! Eyes open. Masks off.
It's there!Amazingly unreal at first,
Then intense. An overwhelming presence
Of nature looms just above us,
We can almost touch it.

A transitory spectacle unparalleled.
Streamers of irregular blue-whiteness
Radiate from the pure black disk.
That was our moon. A halo radiating power
That fills us with awe.

How the ancients must have
Prostated themselves in fear
And worshipped the god that could create
This miracle. And for centuries after
We followed, and forgot the cause.

Now we see it too.
Cameras whirr and click.
And se see Venus, Saturn, Aldebaran, Rigel.
"A total physical and emotional experience."
Midway up the sky. Suspended. so close
You can almost feel it spreading
Everywhere. The dust haze helps to fill
The heavens with softness.

You are in the cathdral of the skies
And can understand main's attempt
To complete with nature, with flying arches,
Vaulted ceilings, and illuminated sculpture
Radiating down on us or His flock,
All part of man's efforts to cope
With the enormity of a solar eclipse,
Which visits at unexpected intervals
Over so many thousands of years.

We are all sun worshippers now,
Gathered to witness and to marvel,
.Drawn by habit or by hearsay.

The minutes hurtle by,
To bring us to the brilliant burst
That shutters the unsuspecting soul.
A diamond of unequaled beauty
Pours forth its radiance with
Splendor that pierces the atmosphere.
An intense emanation that roars out
From the sun in silence so total
That it chills the spine.

It grows. And grows. And finally
The masterpiece is destroyed
As the sun illuminates us once more.
And the mystical corona returns
To its corner where we cannot see it,
Only be aware of its calming presence
As life goes on.

And now the memory lingers. The corona
Suspended forever in our minds,
Midway up the sky.

Everyone hastily comparing notes.
In awe. It was worthwhile, wasn't it?
Touch and go for a while, wasn't it?
Sun burnt the clouds away, didn't it?

Tape recorders, rewound, replayed
To live a little.
We cannot always trust our memories
We need those enormites.
We need those photos.
And tapes. And slides. And movies.
How else can we be sure it is was real?

-GERRIT VERSCHUR,1973.

An elcipse is observed when a celestial body seems to move in front of another. The MOON is eclipsed when the Earth casts its shadow on it. The Galilean satellites of Jupiter eclipse one another. Some close BINARY STARS are eclipsing binaries. The word eclipse is a general one; when the Moon moves in front of a star, however, the event is called an OCCULTATION, and when Mercury or Venus moves between the Earth and the Sun, the event is called a TRANSIT. Eclipses of the Sun and Moon have long made a deep impression on humankind. The blotting out of light from a familiar and apparently predictable source was generally considered a bad omen. Predicting eclipses was one of the duties of ancient Chinese astronomers, who labored under the threat of death if they failed. Today eclipses can be predicted to within seconds./
No photograph can capture all the visual sensations, experienced during totality of the elipse, but photographers use very special lenses and tricks to capture as many as they can. An eclipse of the moon can only be total, or partial, not annular.These pictures range from the "fisheye view" of the entire sky, to the close up view of the inner corona and chromosphere. In the first picture, the light clouds obsutruct the eclipse for a few seconds, as the photographer (Carl Koppeschaar) uses a 300mm f/4 lens for the 1/30 second exposure w/ Kodak photomicrography color film 2483. In the second, a special astronmers gradient filter was used to show the corona as obserbed in our naked eyes. The final picture, shows the six point jewel that the photgrapher was able to capture w/ a hexagonal f/stop diaphragm in thier 35-mm camera, in Massachusetts.

Astronimical artist Pamela Lee, (not the Baywatch girl), shows here a planet, with an orbit of that like Earth, that is about to be swallowed by the sun, the expading giant red star, with an intense heat that could boil the planets oceans and blow its atmosphere out like a comet's tail. Soon pulling the scorched body down into its fiery interior, making another mystery for science to unravel.