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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.
Saturn is in the southwestern sky during
mid-evening.
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!
The June 2009 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
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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.
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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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