Orion

This month, look out for the winter constellations of Canis Major, Canis Minor, Orion (pictured), Gemini, Taurus and Auriga. Courtesy

Prominent in the February evening sky you’ll find the brilliant winter constellations of Canis Major, Canis Minor, Orion, Gemini, Taurus and Auriga. Many people think the cold, crisp air we have this time of year is what makes the stars appear so bright, but in reality the winter skies appear brighter because there are simply more bright stars than during the other seasons.

Looking up, you’ll find dazzling Sirius, the brightest star visible from Wyoming near the southwestern horizon. Towards the west, you’ll find the large but dim constellation of Pegasus. Above the eastern horizon the spring constellations are starting to appear. Leo is near the horizon with the small and dim Cancer found about halfway between the Sickle (backward question mark) of Leo and the bright twin stars of Gemini. If you point binoculars at Cancer, you’ll find a lovely star cluster known as the Beehive (M44).

The first two weeks of February are a good time to look for the Zodiacal Lights in the evening skies. From a dark site watch for a cone-shaped glow of light reaching up from the western horizon into Taurus. This glowing light is the reflection from meteoritic dust that fills our solar system. It is best viewed in dark evening skies near the spring equinox appearing as a faint to bright glow over the western horizon.

One of the cool things about studying the stars is knowing what is out there. How fun to know where to look towards our galactic center, or to know where to see the remains of a supernova explosion or maybe see a galaxy with your naked eye that is more than two million light years away.

This month is a great time to find a stellar nursery that is easily visible to the naked eye. The vast space between stars is filled with gas and dust. Areas of space that contain very dense regions of gas (mostly hydrogen) and dust can start to condense from gravity and begin to form stars. If the condensing gas is dense enough and its core temperatures reach about 10 million degrees celsius, then hydrogen atoms begin fusion forming heavier atoms of helium. Once fusion begins in the core, a star has been born. To see a fabulous stellar nursery this month you will first need to find the constellation Orion.

Orion, the Hunter, is the most obvious constellation in the sky and is visible from any location on Earth. It contains two first magnitude stars and four second magnitude stars. At least part of Orion can be seen from anywhere on Earth because its three central belt stars lie near the celestial equator. Orion is large and impressive and is probably the best known constellation. The best time to view Orion in February is at about 8 p.m. looking to the south.

The two brightest stars of Orion are Betelgeuse and Rigel. Betelgeuse marks the left shoulder of the giant. It is a red supergiant star about 800 times the diameter of our Sun. Betelgeuse is a star in the last stages of life and drew some attention a year ago when it became more dim than normal for several months. Some speculated the giant star was preparing to supernova; but later Hubble images revealed the giant star has blew off some material that was blocking our view as it expanded away from the star.

Rigel marks the right foot of the Orion. Rigel is a blue-white supergiant star with about 50,000 times the luminosity of our Sun. Rigel is a massive supergiant star that will exhaust all its fuel quickly during its life span of only about 500 million years. Stars like our Sun live for about 10 billion years.

The constellation Orion contains five supergiant stars, the most found in any constellation.

The Belt of Orion is easily picked out as three bright stars equally spaced out in a row between Betelgeuse and Rigel. Mintaka, Alnilam and Alnitak make up the Belt Stars of Orion.

If you look below the Belt Stars you’ll see three dimmer stars that contain one of the grandest sights in the night sky, the glowing gas of a stellar nursery. The middle of the three stars appears fuzzy to the naked eye, but through binoculars or a telescope it reveals itself as Messier 42 (M42), the Great Orion Nebula; a region of gas and dust where thousands of stars are forming. It has a visible magnitude of four. In telescopes the Orion Nebula covers roughly one degree of sky or twice the width of a full moon. The Orion Nebula is part of the much larger Orion Molecular cloud that shows up in long exposure photographs of the entire constellation.

The Orion Nebula is a stellar nursery where thousands of stars are being born. This type of nebula is referred to as a bright nebula, HII Nebula (ionized hydrogen) or an emission nebula. To the naked eye ionized hydrogen nebula appear greenish but photographs of the Orion Nebula or any emission nebula will show colors of pink, blue and violet.

An observing trick many amateur astronomers use is averted vision: if you are looking for detail in something in a telescope, try looking away from the center of the object by moving your eye toward your nose or to the edge of the object. More detail can appear the longer you look around and to the side of the object. It’s best to start with low power eyepieces then work up to higher magnifications.

The Orion Nebula is about 1,500 light years away and is the nearest known massive star forming region. The Orion Nebula contains enough gas and dust to form over 10,000 stars the size of our sun. The Orion Nebula is over 30 light years across, which means it take 30 years for light to travel from one side of the nebula to the other. This is so huge, it would take 20,000 of our solar system lined up side by side to cover the entire nebula.

Embedded in the Great Orion Nebula are four young stars that are actually bright enough to be visible through all the nebulosity surrounding the stellar nursery. These four bright stars are known as the Trapezium because they form a baseball diamond shape and they are only about a million years old – basically babies in the lifetime of a star. These four stars are part of an expanding star cluster containing hundreds of faint stars. These young, hot stars emit intense radiation that excites the surrounding nebula causing it to glow. Telescopes can pick out 11 member stars making up the cluster of stars including the four Trapezium stars. The most energetic star in the Trapezium in known as Theta -1C and is about 40 times the mass of our Sun. Theta-1C is visible as a fifth magnitude star and is one of the most luminous stars known.

This is a monthly article provided by the Cheyenne Astronomical Society (CAS). Marcy Curran has been the editor of the Cheyenne Astronomical Society’s newsletter since 1986 and taught astronomy at LCCC from 1992-2013. For further information about the CAS, visit our website at killerrabbit.co. Our monthly meetings are free and open to the public and are held the third Friday of each month.

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