WEEKLY SKYWATCH

By Jarrett DuBois

Down to Earth Astronomy

 June 28 - July 4, 2009

Planets – Mercury is low in the east/northeastern sky before sunrise.

 Venus is in the eastern sky before sunrise.

 Mars is in the eastern sky before sunrise.

 Jupiter is in the southern sky before sunrise.

Moon – First Quarter Moon: 6/29.

Comets - None visible with the unaided eye.

Deep Space – The red giant star Antares, the alpha star of the constellation Scorpius, will be to the right of the moon on the evening of 7/3.

Meteor Showers – There is one minor meteor shower this week. The June Bootids peaks on 6/28-29.

Keep looking up. You never know what you'll observe and enjoy in the night sky!

June is the start of summer, which begins on June 21 at 12:46 a.m. CDT. The prime event this month is a line up of planets, moon and a beautiful deep space object in the pre-dawn sky.
The evening planet this month is Saturn. Saturn is in the southern sky during early evening and teams up with the moon on the evening of 6/27. Saturn will be above and to the right of the moon on that night.
The early morning planets this month are Mercury, Venus, Mars and Jupiter. Jupiter can be found in the southeastern sky before sunrise. Early morning observers will be treated to a beautiful pairing of the moon and Jupiter on 6/13. Jupiter will be below and slightly to the left of the moon on that morning. Mercury, Venus and Mars will be low in the eastern sky before sunrise. Venus and Mars team up with ............

............ the Milky Way curves around the eastern sky from the north to the south as darkness falls. The main pattern of stars to look for is the “Teapot”, better known as the constellation Sagittarius. Just off the spout of the teapot lies the center of our galaxy. Within this region are numerous star clouds, star clusters and nebula, the unique and beautiful accumulation of gas and dust that are stellar nurseries. Observers will also be able to view the dust lanes that slice through the Milky Way and block out the light of the stars that are behind them.
The featured area of the night sky this month is the constellation Sagittarius and the dense star clouds of the Milky Way galaxy located to its right. .

Stellar Explosions.

In astronomy, the terms Nova and Supernova both bring to mind exploding stars occurring anywhere in the universe. However, each term has a different meaning. While each one names a type of explosive event that takes place in stars, a nova is a star whose brightness increases tremendously and then slowly fades, while a star that becomes a supernova undergoes a massive explosion that either destroys or alters the star forever.

            Supernova explosions of a star are more spectacular and destructive than a nova. They occur maybe once every few hundred years in a galaxy. There are three recorded supernovas that we know of, the last one happening in 1604 AD. In 1054 AD, history recorded a supernova that was to become known as M1, the Crab Nebula, in the constellation Taurus. To telescope observers, the Crab Nebula appears as a wispy thin cloud, which is the leftover stellar material that once was part of the star.

            The causes of supernovas are not yet completely understood by astronomers. An average star such as our sun would not reach a point in its life that it would supernova. Stars that are much more massive than our sun sometimes explode in the late stages of their life cycles. These stars leave little behind except a shell of gas and dust that is expands outward from the core of the exploded star. One of the things that a supernova does when it explodes, sending gas and material out into interstellar space, is to contribute to the formation of new stars.

            Before modern astronomy, when a star appeared where none had been seen previously, it was called a new star or a nova. The Latin term for new is novus. The term nova back then was incorrect, for the star was not new. The star involved had always been there, but was just not visible to the naked eye. Astronomers have estimated that there may be a dozen novas occurring in our own Milky Way galaxy each year. Unfortunately, most of them are either too distant or too obscured by dust and interstellar material to be able to be viewed from Earth. Traditionally a nova flares up to one thousand times its normal brightness in a matter of hours or days, then fades, grows bright again, and then fades to near its original brightness. Many of these types of novas are considered variable stars. One of the reasons they act as they do is because the outer layer of the star builds up helium too quickly to be contained. The star then emits a small fraction of its mass explosively, which is the reason for the increase in brightness. Typically a star such this has a predictable timetable when it brightens, from a few days, to hundreds of days, and its light output is quite measurable.

            Novas and supernovas are interesting phenomena in the study of astronomy. While supernovas are quite rare, they are a part of the evolution of our universe. Novas, while not as dramatic and destructive as a supernova, are an important ingredient to the dynamic life cycle of a galaxy. They are a part of the beauty of the stars we observe in our nighttime sky, even if we do not recognize the star as being a nova.

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