January 2011

Tony Martinez

Each month I will describe sights of interest in the night skies of South Carolina. These sights will be broken down into three sections; what you can see with the naked eye, with binoculars, and with a small telescope. The best time to view the night sky is at and around the times when the Moon is not visible, what is known as a New Moon; which will occur this month on January 4th. For January, your best viewing nights will be from January 1st through January 11th. The Star chart below is set for Florence, SC on January 15th at 9 pm.

A Star is Born:

The theory of the birth of a star is a simple concept to explain, but can be somewhat difficult to conceive. The formation of a star is described as follows:

After the Big Bang, the primary matter existing in the universe was, and still is, hydrogen. Over billions of years, as the universe quieted down somewhat, some of the hydrogen atoms formed clumps (clouds) of hydrogen gas. These hydrogen clouds formed due to gravitational attraction. We also know that the greater the mass, the stronger the gravitational pull. So as the hydrogen gas clouds grew larger, they attracted more and more hydrogen. Eventually, these gas clouds compressed down because of gravity; essentially, they collapsed into themselves. At some point during the cloud’s compression, the gravitational force and temperature of compression became so great that two hydrogen atoms fused into element helium; a process known as nuclear fusion. Einstein taught us that when atoms split or fuse together, a tremendous amount of energy is released. Splitting a uranium atom results in the force of an atomic bomb. Fusing two hydrogen atoms together results in the even greater force called a hydrogen bomb. So when the huge hydrogen cloud compression generated the fusion of hydrogen atoms, the equivalent of billions of hydrogen bombs went off, giving off tremendous heat and light, and a star was born!

Unlike, a typical bomb, the fusion in a star is somewhat controlled with the center of the star fusing hydrogen into helium, and the huge mass of cooler hydrogen in the outer part of the star supplying more hydrogen fuel for the fusion in the center. Our Sun is a medium size star, and it should take about ten billion years for all of the hydrogen to be depleted. Our star is now about half way through its life; five billion years old.

Keeping in mind the age of our star, this month let us search out some young stars in the night sky. There are two groups of young stars that are easy to locate this time of year. The first is the well-known Pleiades Cluster; also known as the Seven Sisters. You can easily spot it above and to the right of the prominent Orion constellation. Most of the stars you see at night are billions of years old, but the stars of the Pleiades are “only” about 100 million years old. These stars are like teenagers in the sky. Our Sun is 50 times older than the Seven Sisters! The image below is the Pleiades seen through seven power binoculars.

The Pleiades bring to mind other properties of young stars. Huge hydrogen clouds often result in the formation of not one but several star births in the same region of space, and are usually surrounded by gases left over from their birth. The younger the stars, the more likely these gases are present. As you stare at the Pleiades through binoculars or a telescope, it is difficult to see any of the leftover gases. However, as shown below, at 25 power, using time exposure and filtered astrophotography, the gaseous afterbirth is quite obvious.

This time of year in addition to viewing the Pleiades “teenagers,” you can also easily see a star nursery. This nursery is the apparent center star of the sword of the constellation Orion. Simple binoculars will show that there is not a star in the center of the sword, but a fuzzy object, called the Orion Nebula (M42); see arrow below.

Remember, the younger the stars, the more obvious the leftover gases. With the Pleiades, it is easy to see the young stars, but hard to see and gases. As you look through your binoculars at the Orion Nebula, you find it is easy to see the gases leftover from star birth, but hard to see the new born stars. So your challenge for this month is to see the young stars inside the Orion Nebula. These stars are less than a million years old, which means that our Sun is about 5000 times older than the stars in the Orion Nebula. Therefore these stars are true “babies,” and this nebula is therefore thought of as a star nursery. The names of these baby stars are the Trapezium. Although there are many stars in the nursery, this name is derived from the four brightest stars, which form somewhat of a trapezoid shape.

It is not really possible to see these stars with simple binoculars. At seven to ten power, you can see that the Orion Nebula has a bright center area. At about 15 power, you can see that there is at least one or two stars in the center, but I find that only with my 25 power binoculars can I resolve them into the four star Trapezium. However, with any simple telescope from 25 power on up, you should easily locate the “baby” Trapezium stars. The below image shows the Trapezium in the Orion Nebula as seen through a 25-40 power binoculars; and yes on a clear night, the Orion Nebula will look like an eagle with its wings out spread.

Keep warm and enjoy Orion’s babies.

Naked Eye Sights: The young Pleiades cluster. Orion’s sword.

Binocular Sights (7 to 10 power): The Pleiades. The Orion Nebula.

Telescope Sights (60-100mm): The Trapezium babies in the Orion Nebula.

See you next month!

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