Basic Astronomy & Cosmology Webster’s Dictionary defines Astronomy as "the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties." Truthfully, though, you could say that astronomy is the study of everything, because everything is a part of the Universe. Cosmology is the metaphysical study of the origin and nature of the universe. The branch of astrophysics that studies the origin and evolution and structure of the universe. Fargo-Moorhead Astronomy Club Homepage

Our Universe A Guided tour of the 13-14 billion year old place we call, "our universe". From our perspective... All pictures are thumbnails

Our star (the sun), is a common star (with a common age, size and color), in a common solar system, in a common galaxy, in a common cluster of Galaxies (the Local Group), in a common super cluster (the Local Group is on the edge of the Virgo Super Cluster)...

A light-year is the distance light travels in one year, racing at a speed of 186,000 miles per second. It's equal to about 5.88 trillion miles, or 9.46 trillion kilometers. Light-year = 9.46053e12 km (= 5,880,000,000,000 miles = 63,239 AU); the distance traveled by light in a year.  Astronomical unit (AU) = 149,597,870 km; the average distance from the Earth to the Sun.

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Our Solar System The Stars near us The Stars around us We are in what we call the Orion Arm of the Milky Way Our Galaxy, the Milky Way     The center of the Milky Way   Our section of the Local Group The Local Group       Our Cluster Our Super Cluster     The Universe from our view point The Universe from outside

On a clear dark night away from city lights, the heavens can create an overwhelming sense of infinity. Seemingly countless points of light, so far away, urge one to contemplate the insignificance of a lone planet amid the incomprehensible breadth of the universe.

Almost all of the sky objects visible to the naked eye are stars that reside in our galaxy. In fact the bulk of those you can see are relatively nearby, within a few thousand light-years. Most are actually within a few hundred light-years, with the exception of a few intrinsically brilliant stars that are many thousands of times more luminous than the Sun.

There are roughly 300 billion stars in the Milky Way. At most, 8,479 of them are visible from Earth to someone with perfect vision under ideal conditions. Not all these stars can be seen from any one location, of course. You miss about half of them by not traveling to the Southern Hemisphere, for example. The horizon, as well as the seasons, place further limits. Roughly 2,500 stars are available to the unaided eye in ideal conditions from a single spot at a given time.

Basic Astronomy

Stargazing sometimes intimidates beginners because they feel the night sky itself is so complex. To make things easier, the heavens were divided into 88 constellations, most of which are visible from the at different times of the year from most places on Earth.  At any given moment on a clear, moonless night, a thousand or more stars are visible. Throw in five planets, a few star clusters, a spiral galaxy, a stellar nursery, and the odd bright comet, and the catalog of objects visible to the unaided eye is truly impressive -- and overwhelming. To bring this complexity down to earth a bit, veteran stargazers suggest an "inside-out" strategy: begin your sky watching adventures indoors before you venture out into those big, starry skies.  This usually guarantees that it will rain that night, but nevertheless it is a good idea.

Start with a good guide to the night sky or a meeting of a local astronomy club. Clubs often host special events for beginners, with experienced members offering tips on what to look for, where to go, and what equipment to take along. The only instrument that most beginners need is their eyes. Our eyes can detect subtle variations in brightness, determine the colors and relative temperatures of stars, and track the motions of the Moon and planets from one night to the next.

Finally, you need a good viewing spot. Start with your back yard, even if you live in the city. Then, as you gain experience, escape from city lights into the darkness of the countryside. Find a state park or other safe, accessible spot. And try a night without moonlight, so you can see shooting stars and the subtle glow of the Milky Way. A constellation is a group or pattern of stars. Centuries ago, people saw images in these patterns and gave them the names of animals or characters from ancient myths. Of course, different people saw different pictures in the same patterns of stars. And in some cases, two cultures saw similar pictures, but included slightly different groups of stars in their constellations.

Annual Meteor Showers

Quadrantids: January
Virginids: March/April
Lyrids: April
Scorpiids: May
Delta Aquarids: July
Perseids August
Piscids: September
Orionids: October
Leonids: November

Life of a Star

Stars are born in nebulae. Huge clouds of dust and gas collapse under gravitational forces, forming protostars. These young stars undergo further collapse, forming main sequence stars.

Stars expand as they grow old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright. This is a red giant or a red super giant (depending on the initial mass of the star). It will eventually collapse and explode. Its fate is determined by the original mass of the star; it will become either a black dwarf, neutron star, or black hole.

Links
Telescope FAQ
Clear Sky Clock
International Dark Sky Association
American Astronomical Society
Astronomy Picture of the Day
Interactive Sky Chart
Space Weather
Solar Pictures of the Day
Aurora Forecast