One exercise that I have used in my classes to imagine sending a letter to another world in space. What would be the return address? Besides name, local address, town, zip code and country, we would have to state, “Earth.” (It is assumed that the receivers of the letter can read English.)

Then we are part of our “Solar System,” the collection of objects that orbit the sun, our star. But our solar system is but a mote in our galaxy. Since there are many galaxies near us, let’s call our galaxy, “Large Barred Spiral Galaxy,” a large pinwheel shaped galaxy with a huge bar of stars centered on our galaxy’s center.

Our galaxy is one of about three dozen galaxies that makes up the “Local “roup. Then the local group is part of the larger assemblage called the Virgo Super Cluster. Lastly, since there may be other universes as well as our own, let’s call our universe, “The Known Universe.”

So here is a complete address for our Frostburg State Planetarium: FSU Planetarium, Frostburg State University, Frostburg, MD 21532, United States, Earth, Solar System, Large Barred Spiral Galaxy, Local Group, Virgo Super Cluster, The Known Universe.

Another way of relating to our position in the universe is to describe the hierarchy of the universe, which can be done with three sentences.

1. We live on a spinning planet (earth) that orbits our star (sun). This statement, not accepted until about 350 years ago, states that the Earth is rotating (once every 24 hours) and orbiting the sun (every year). A planet is a large round object that orbits a star. A beam of light flying over Earth’s equator can go around 7.5 times in a second.

A star is a huge gaseous sphere powered by nuclear reactions. Light would take over 14 seconds to fly around the sun’s circumference. Light takes 500 seconds to travel from the sun’s surface to the Earth’s surface

2. Our sun is one of billions of stars that make up our galaxy. The sun’s placement in the galaxy was the subject of key studies during the 19th and early 20th century. Our galaxy is in the shape of a flattened disk that takes light 100,000 years to traverse.

Our sun is about one half of the way from the center to the rim of the galaxy. So our distance to the center of the galaxy is about 25,000 light years. Our sun is moving around our galaxy’s center so it completes an orbit in about 220 million years. Our galaxy is held together by the gravity of its stars, gas clouds and dark matter.

3. Our galaxy is one of billions of galaxies seen in all directions. Our galaxy is in the Local Group, a loose community of over three dozen galaxies in a region shaped like a fat sausage 3 million years across. Our most sensitive detectors aboard large space telescopes can detect galaxies out to a distance of 10 billion light years.

Our universe is expanding at an ever increasing rate, owing to its explosive origin and dark energy, which causes the repulsion of matter at great distances (sort of an antigravity force).

Our February Planetarium program that begins today is “Quick Intro to the Universe,” addressing the key concepts about the marvelous universe that we are in.

The segments include: “Our Place in the Universe,” “Looking Back in Time,” “Why is the Sky Dark at Night?”, “How did the Universe Come To Be?” and “What is the Likely Fate of the Universe?”

As usual, the program begins with a tour of the current evening sky, so our planetarium visitors can spot Mars (using Orion) and the North Star (using the Big Dipper) in their back or front yards; they can also learn about coming evening sights such as brilliant Venus in the western dusk this spring.

Free materials available to visitors include a February star map, a summary of the “Intro to Universe Program” and 2010 Night Highlights (also posted on our Web section of the Frostburg.edu Web site). Also posted in the Teachers Resource area (look in the lower right corner of the front page) are materials for teachers and homeschoolers.

Our programs are each Sunday in February in Tawes 302 (just off the front lobby), starting at 4 p.m. and 7 p.m. with convenient parking nearby. (Please disregard signs that specify what stickers you need to park in a particular area — these signs apply when classes are in session.)

There are restrooms down the main hall from the Planetarium and close by water fountains. All visitors are welcome. There is no age limit for visitors; even infants in mother’s arms are OK as they often sleep in the dark.

If you haven’t been to our planetarium before, please leave your home a little bit earlier to arrive on time. It’s quite awkward to come into the darkened chamber.

The brightest evening stars now form a hexagon or six-sided figure high in the south. At the bottom is Sirius, the night’s brightest star. As you go clockwise around the Hexagon, you come to Procyon (above and to the left of Sirius).

Then above Procyon are Gemini’s bright stars, Pollux and Castor. Near the top of the sky is golden star Capella. Then below and to the right of Capella is Aldebaran, marking the eye of Taurus, the Bull. Below Aldebaran and slightly to the left is Rigel, the brightest star of Orion.

Readers can get a free planetarium bookmark with 2010 program titles and a small map showing parking and buildings near Planetarium by calling (301) 687-7799 and stating their name and mailing address.

Bob Doyle invites any readers comments and questions. E-mail him at rdoyle@frostburg.edu . He is available as a speaker on his column topics.