Glossary

Glossary of words used in this website
Burnham Robert Burnham, Jr., author of Burnham's Celestial Handbook. This is an excellent survey of the amateur astronomer's night sky, annotated with much scholarly background information. Published in 3 volumes by Dover Publications.

C5 The model number of the Celestron C5 telescope. The primary mirror of this telescope has a diameter of 5 inches.

CCD camera A specialized digital camera built to work in low light conditions. The camera fits on the back of a telescope, where an eyepiece would be otherwise.

Galaxy An immense collection of stars. The universe consists of untold numbers of galaxies, generally separated from each other by vast distances. Whatever may lie between the galaxies, it is not stars. Our star, the Sun, is one of more than a billion stars that we collectively call the Milky Way Galaxy. The nearest galaxy to the Milky Way Galaxy is the Andromeda Galaxy, about 2,000,000 light years away.

Globular cluster A dense collection of stars which as a group orbits a galaxy. Typically these clusters consist of very old stars, possibly formed soon after the time of formation of the galaxy. Most globular clusters in our galaxy consist of hundreds of thousands of stars.

Light year A measure of distance, despite the reference to a year. A light year is the distance that light travels in one year. Since light travels about 186,000 miles in one second, a light year is very great distance indeed.

LX200 The model number of the Meade telescope in my observatory. The primary mirror of this telescope has a diameter of 12 inches.

Open Cluster A group of relatively young stars, all formed from a common cloud of interstellar gas. Stars in open clusters are usually young (ages measured in millions of years), compared to the age of the Sun (age about 6 billion years.) Also, many of the stars in open clusters are large and therefore very hot, with mass 10 to 15 times that of the Sun.

Planetary nebula A glowing cloud of gas which has been blown free of a dying star. The star is said to be dying because it has used up all or nearly all of its fuel for nuclear fusion. The expanding cloud of gas is often made visible to us because radiation from the central star is ionizing the gas and causing it to glow.

Reflection nebula A cloud of interstellar material made visible by reflecting light from nearby stars.

Waning Decreasing. In the case of the moon, when the portion of the moon that we see as lit by the sun is waning, or decreasing, we see the visible portion of the moon get smaller from day to day. The rate of decrease is steady and slow. You can actually see a difference by the hour if you look closely.

Waxing Increasing. In the case of the moon, when the portion of the moon that we see as lit by the sun is waxing, or increasing, we see the visible portion of the moon get larger from day to day. The rate of increase is steady and slow. You can actually see a difference by the hour if you look closely.

White dwarf The remains of a sun-like star that has burned all its fuel. With the outward pressure of nuclear fusion gone, the star collapses on itself due to self-gravity and becomes a very dense object about the size of a planet. The material is so dense that it is neither gas, liquid nor solid; it is called degenerate matter. The material is so dense that a teaspoon full of white dwarf material brought to Earth would weigh as much as an elephant.

Glossary of words used in this website
Burnham	Robert Burnham, Jr., author of Burnham's Celestial Handbook. This is an excellent survey of the amateur astronomer's night sky, annotated with much scholarly background information. Published in 3 volumes by Dover Publications.
C5	The model number of the Celestron C5 telescope. The primary mirror of this telescope has a diameter of 5 inches.
CCD camera	A specialized digital camera built to work in low light conditions. The camera fits on the back of a telescope, where an eyepiece would be otherwise.
Galaxy	An immense collection of stars. The universe consists of untold numbers of galaxies, generally separated from each other by vast distances. Whatever may lie between the galaxies, it is not stars. Our star, the Sun, is one of more than a billion stars that we collectively call the Milky Way Galaxy. The nearest galaxy to the Milky Way Galaxy is the Andromeda Galaxy, about 2,000,000 light years away.
Globular cluster	A dense collection of stars which as a group orbits a galaxy. Typically these clusters consist of very old stars, possibly formed soon after the time of formation of the galaxy. Most globular clusters in our galaxy consist of hundreds of thousands of stars.
Light year	A measure of distance, despite the reference to a year. A light year is the distance that light travels in one year. Since light travels about 186,000 miles in one second, a light year is very great distance indeed.
LX200	The model number of the Meade telescope in my observatory. The primary mirror of this telescope has a diameter of 12 inches.
Open Cluster	A group of relatively young stars, all formed from a common cloud of interstellar gas. Stars in open clusters are usually young (ages measured in millions of years), compared to the age of the Sun (age about 6 billion years.) Also, many of the stars in open clusters are large and therefore very hot, with mass 10 to 15 times that of the Sun.
Planetary nebula	A glowing cloud of gas which has been blown free of a dying star. The star is said to be dying because it has used up all or nearly all of its fuel for nuclear fusion. The expanding cloud of gas is often made visible to us because radiation from the central star is ionizing the gas and causing it to glow.
Reflection nebula	A cloud of interstellar material made visible by reflecting light from nearby stars.
Waning	Decreasing. In the case of the moon, when the portion of the moon that we see as lit by the sun is waning, or decreasing, we see the visible portion of the moon get smaller from day to day. The rate of decrease is steady and slow. You can actually see a difference by the hour if you look closely.
Waxing	Increasing. In the case of the moon, when the portion of the moon that we see as lit by the sun is waxing, or increasing, we see the visible portion of the moon get larger from day to day. The rate of increase is steady and slow. You can actually see a difference by the hour if you look closely.
White dwarf	The remains of a sun-like star that has burned all its fuel. With the outward pressure of nuclear fusion gone, the star collapses on itself due to self-gravity and becomes a very dense object about the size of a planet. The material is so dense that it is neither gas, liquid nor solid; it is called degenerate matter. The material is so dense that a teaspoon full of white dwarf material brought to Earth would weigh as much as an elephant.

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