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Table of contents

Astronomy: Learning Standards

Difference between astronomy and astrology

Viewing space from here on Earth

Light pollution

Earth-Moon system

Planets and dwarf planets

Solar system: Our earliest ideas

Solar System: Medieval ideas

Solar System: Our modern view


Our Sun, and nuclear fusion

Black holes


Light pollution

The Big Bang theory

The universe

History of Astronomy

Ancient Greeks (tbd)

Ulugh Beg, medieval Samarkand/Uzbekistan, astronomer

Copernicus, Tycho Brahe, Kepler and Galileo Galilei

Special topics

SETI: Search for Extraterrestrial Intelligence

Proof that the Earth is revolving

Leap seconds

Neutrino astronomy

Gravitational repulsion and the Dipole Repeller


Sims & Apps

Science Sims @ CCNY

The largest objects in the sky!

Look up at the night sky – Are there immensely huge things that are just a bit too faint for the human eye to see? You betcha! Check out this amazing composite photo. This shows the actual apparent size of deep space objects, in our night sky, if they were brighter.

Here are the same object labeled

Actual size of deep space objects if they were brighter labeled

The images are in scale with one another, including the Moon, but not to the Milky Way background.

1. The Moon.
2. Andromeda Galaxy.
3. Triangulum Galaxy.
4. Orion Nebula.
5. Lagoon Nebula.
6. Pinwheel Galaxy.
7. Sculptor Galaxy.
8. Supernova remnant 1006.
9. Veil Nebula.
10. Helix Nebula.
11. Sombrero Galaxy.
12. Crab Nebula.
13. Comet Hale-Bopp (c. 1997)
14. Venus.
15. Jupiter.
16. International Space Station.

Astronomy Amateur 3 V2CC BY-SA 3.0view terms User Halfblue on en.wikipedia

Astronomy Amateur 3 V2CC BY-SA 3.0view terms
User Halfblue on en.wikipedia

What is an astronomy?

An astronomer admires the beauty of the stars and other celestial objects and wants to learn what they are and how they work. An astronomer is a scientist who tries to understand and interpret the Universe beyond Earth, and the Earth within the Universe. Using observational tools like space and ground-based observatories, computers and the good old paper and pencil, astronomers attempt to build up a picture, not only of what the Universe is like today, but what it was like billions of years ago, right back to the “Big Bang”.

To do this Astronomers have to understand the behaviour of matter in conditions that simply do not exist on Earth, whether at extreme temperatures or involving exotic objects and particles. They must use whatever kind of light, from radio to gamma rays, and particles (from cosmic rays to neutrinos) make it to Earth, along with sophisticated computers to piece together what happens beyond our planet.

Observational astronomers might look for new planets, try to understand stars, galaxies, black holes, and other phenomena, or try to map the entire sky. More theoretical researchers might measure magnetic fields or simulate the structural build-up of the stars, figure out how galaxies formed and how the expansion of the Universe evolved. To summarise, they build models of the Universe from fundamental physics and endeavour to make it understandable.

+ International Astronomical Union website


“Interestingly, according to modern astronomers, space is finite. This is a very comforting thought– particularly for people who can never remember where they have left things.”

– Woody Allen

“Ask ten different scientists about the environment, population control, genetics and you’ll get ten different answers, but there’s one thing every scientist on the planet agrees on. Whether it happens in a hundred years or a thousand years or a million years, eventually our Sun will grow cold and go out. When that happens, it won’t just take us. It’ll take Marilyn Monroe and Lao-Tzu, Einstein, Morobuto, Buddy Holly, Aristophanes .. and all of this .. all of this was for nothing unless we go to the stars.”

– Writer J. Michael Straczynski, from a character’s speech (Commander Sinclair) in Babylon 5, season 1, “Infection”


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