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Skywatch January 2007
(newest at top)
Skywatch line for Wednesday, January 31 and Thursday, February 1, 2007:
by Ray Bogucki
All five bright planets are currently visible during one night, but not at
one time. The first, and most obvious to appear in the early evening sky, is
our brightest neighbor, Venus. It can be found shortly after sunset low in
the west-southwest, blazing with a magnitude of minus 4 in the twilit sky.
Venus shines so brightly because its outermost cloud layer is very dense and
reflects 76% of the sunlight that falls on it. Its disc appears 11
arc-seconds in diameter in a telescope.
About 7 degrees (or 3 finger widths at arm's length) below Venus is our
innermost planet Mercury. Although it is reasonably bright, at minus one
magnitude, the surrounding sky is still so brightly lit at 30 minutes after
sunset, that binoculars will be a big help in finding it. For the next two
weeks, Mercury will set a little later each evening so this will be the best 2
weeks to observe this elusive planet during its current apparition.
To find the third planet, turn around, after observing Venus, and face east
to locate the ringed giant Saturn, rising into the eastern sky just a few
degrees above the bright star Regulus in Leo, the Lion. On Thursday night it
will shine about 10 degrees below the rising full Moon, halfway between the
Moon and Regulus. The Moon will pass very close to Saturn Friday afternoon
before it rises at our location on the globe. In fact, observers in eastern
Scandinavia will see the edge of the Moon actually occult, or cover, Saturn
for a brief period. When the Moon appears here on Friday night it will be
just below Saturn -- an elegant pairing.
The next planet to appear is Jupiter, rising in the east about 3:30 a.m.
Always fascinating to observe in a telescope, this gas giant shines
brilliantly at almost minus 2 magnitude, close to the bright reddish star
Antares in the constellation Scorpius. The orbital motions of the four
Galilean moons around Jupiter bring them into constantly changing
configurations with changes easily detected within an hour. Especially
interesting are shadow transits which occur when one of the moons casts a tiny
black shadow which can be followed in a telescope as it sweeps across the
surface of the giant planet.
Finally, our nearest outer neighbor, Mars, rises at 5:30 a.m., just at the
beginning of morning twilight. Mars is currently well beyond the Sun near the
farthest reaches of its orbit and appears quite small and faint. The Earth
moves faster in its orbit than Mars does, and we will spend this entire year
overtaking the Red planet. Our combined orbital motions will cause Mars to
rise one or two minutes earlier each day. However, sunrise will occur earlier
each day by the same amount so that, for the next three months, Mars will
continue to rise about one and a half hours before the Sun. We will finally
overtake and pass Mars in mid-December when it will appear quite large and
bright.
This is the Skywatch Line for Monday and Tuesday, January 29 and
30.
by Joe Slomka
The Sun sets at about 5:05 PM; night falls at 6:41. Dawn breaks at 5:35
AM and ends with sunrise at 7:12.
As the Sun sets, the thirteen-day Moon shines brightly between the
constellations Gemini and Auriga. The Moon is mostly illuminated and washes out
most of the stars in its vicinity.
Venus blazes low in the southwest. It becomes more obvious as the sky darkens,
but also becomes lower. It is best seen in binoculars. Mercury is about five
degrees below Venus and is more difficult to spot amid ground clutter.
Saturn rises about Six PM and is well placed for observation by Ten. Saturn’s
brilliance easily aids identification. The bright star Regulus is dimmer than
Saturn and lies to the lower left of the Ringed Planet.
Dawn finds Saturn low in the West and Jupiter about as low in the East. Jupiter
rises at first light and begins a yearlong apparition. Mars appears midway
between Jupiter and the eastern horizon shortly before sunrise. It, too, begins
a yearlong appearance in our sky.
If one looks up at 7:00 PM on a moonless night, the Hyades star cluster is high
and forms the horns of Taurus, the Bull. The "V" shaped constellation
points to a large pentagon, the constellation AURIGA. If the "V" is
extended, the upper horn joins the bottom star of Auriga. The lower horn
stops at a star just below. Train a telescope at that lower star, and look
just above it. The hazy patch is the Crab Nebula. On July 4, 1054, a
star exploded, shone brightly in daytime, and disappeared after about a year.
The Crab Nebula is all that is left, a cloud of gas and debris, expanding at 600
miles per second, with a diameter of 6 light years and 6300 light years distant.
Recent studies revealed that the remnant star is a pulsar, a very dense star
that does not emit light, but radiation in regular bursts, hence the name.
This radiation lights up the neighboring gas in infrared light. This is
the most conspicuous supernova remnant.
Clear Skies
Joe Slomka
This is Dudley Observatory's Skywatch Line for Friday, January 26, through
Sunday, January 28.
by Alan French
The Moon was at first quarter Thursday, so a bright waxing gibbous Moon will
dominate much of the night sky over the weekend. The Moon's path is taking
it very high in our skies right now. On Friday night, the Moon will be due
south and highest at 6:36 PM when it will be 69 degrees above the horizon.
At 7:33 PM on Saturday night, you'll find the Moon 73 degrees above the
southern horizon, and it will be highest at 75 degrees above the southern
horizon at 8:31 on Sunday evening. Also, note that sunrise is marching
eastward across the Moon, and each night more of the Moon's visible face
will be in bright sunlight as it moves toward Full. The Full Moon occurs
just after midnight on Thursday, February 1.
Brilliant Venus continues to dominate the southwestern sky just after
sunset. The Sun sets just after 5:00, and Venus should be a lovely sight
about 13 degrees above the southwestern horizon by 5:30. Against the darker
evening sky at 6:00 PM, Venus will be even more impressive, and will still
be 9 degrees above the horizon. During the coming months Venus will
continue to move higher into our evening sky. By mid-February our sister
planet will be nicely visible even after the last glow of evening twilight
has vanished. It will continue to be well placed from our latitude through
mid-June.
At 6:30 PM, as Venus is preparing to set, Saturn is rising in the
east-northeast. Both will only be three degrees above the horizon, so you
will need a good view to the southwest and northeast to catch them both.
Saturn rises earlier each night and is moving higher into the evening sky.
By the end of June, Venus and Saturn will be very close together in the
early evening sky.
If you have an excellent view of the southwestern horizon, and a night where
the horizon is free of clouds and haze, this weekend would be a good time to
look for elusive Mercury. Being the innermost planet, orbiting close to the
Sun, Mercury never emerges high into the evening or morning sky. You'll
want to look for Mercury at 5:45 PM, when it is still a bit over three
degrees above the horizon, and the skies are reasonably dark. Binoculars
would greatly improve your chances of finding Mercury. Start with Venus,
and then scan or look to the lower right. Mercury should appear as a star
about 8 degrees to the lower right of Venus. With binoculars, looking at
the horizon below Venus, and then moving your view slightly to the right
should turn up Mercury. If you don't find it, try again on the next clear
night.
Skywatch line for Wednesday, January 24 and Thursday, January 25, 2007
by Ray Bogucki
About 9 p.m. this week, the bright constellation Orion the Hunter is at its
highest point in the southern sky. Last Thursday's Skywatch line discussed
the two brightest stars in Orion: the hot, young blue-white giant star Rigel,
marking Orion's left foot, and Betelgeuse, the much cooler, older, red
supergiant star in the Hunter's left shoulder.
If we turn our careful attention to the three much fainter stars that form
the sword dangling from Orion's three bright belt stars, our unaided eye tells
us that the center star in the sword is not a point of light, but a fuzzy
patch of light. Even a small telescope will reveal that this is the Great
Orion Nebula, the brightest and most spectacular nebula visible from our
location, about 40 degrees north latitude. In a telescope, the nebula looks
like a puff of smoke being swirled around by some unseen interstellar winds.
The nebula has an apparent diameter of about twice the size of the full Moon.
Because the nebula is well over 1,000 light-years away, its real diameter must
be about 30 light years, or more than three times the distance from Earth to
the brightest star, Sirius, one of our near stellar neighbors. The soft
greenish glow of this gargantuan nebula is caused by hot, bright newly born
stars hidden in the giant cloud of gas and dust. These young stars shine with
an intense brightness which is reflected from the dust and gas. In addition,
the intense ultraviolet radiation excites the hydrogen gas atoms which then
glow with a bright fluorescence, much as the neon atoms in a neon sign glow.
The formation of a star is a fascinating process. A small knot of slightly
denser gas and dust will gravitationally attract more neighboring gas and dust
to itself. As the center of this knot grows, it attracts more material from
farther and farther away. The massive infalling of material constitutes a
great compression so the core of the growing nodule continually becomes denser
and hotter. When the temperature reaches ten million degrees, the hydrogen
atoms begin to undergo nuclear fusion, producing helium and immense amounts of
energy, the same process that occurs in the detonation of a hydrogen bomb.
The energetic radiation streaming out from the center of the large globe of
gas and dust eventually balances the gravitational infalling of matter so that
outward and inward pressures balance, and the new star becomes stable. After
many years of moving outward through the nodule, the outpouring energy reaches
the surface of the new star and bursts out as light and other forms of energy
into the universe. A star is born! The birth announcement, arriving as a new
point of light in our sky, takes more than a thousand years to get to Earth
from the Orion Nebula.
This is the Skywatch Line for Monday and Tuesday, January 22 and
23.
by Joe Slomka
The Sun sets at about 4:53, with twilight ending about 6:35 PM. Dawn breaks at
6:40 AM, ending with sunrise at 7:18.
As the Sun sets the four-day-old Moon blazes quite high in the southwest. It is
almost a quarter illuminated. Its position marks the location of the southern
fish in the constellation Pisces. Venus is the next brightest object, roughly
halfway between the horizon and the Moon. If your western horizon is relatively
unobstructed, you may spot bright Mercury about halfway between Venus and the
horizon. As January continues, Venus and Mercury become higher and easier to
observe. Also, note that Mercury and Venus are about ten degrees apart now, but
become closer during the next two months.
Saturn rises about twilight’s end, and remains up most of the night. Note that
Saturn rises just as Venus is setting. When can you observe them both: Saturn in
the East, Venus in the West?
Jupiter rises at about 4 AM. Shortly before sunrise, both Jupiter and Saturn can
also be distinguished at opposite ends of the sky: Jupiter in the southeast,
Saturn in West.
With Venus so prominently high and bright, let us examine her in greater detail.
Venus is the second planet from the Sun. It is almost an Earth twin, about the
same size and mass. Early telescopic observers noted its complete cloud cover.
They speculated that Venus was a lush, tropical planet. As science obtained
better instruments, rude shocks came. Venus did not rotate in 24 hours like
Earth; its day lasts 243 earth-days. Russian and US probes landed on Venus.
Pictures showed a rock filled wasteland. In addition, those same landers
recorded a toxic atmosphere with true acid rain. Temperatures approached the
melting point of lead. Venus turned out to be the furthest thing from a
paradise. Most planetary observers now think that Venus is a case of
uncontrolled global warming. The one good benefit of this hellish environment is
the highly reflective cloud cover. When Venus makes a close approach to Earth,
its illumination can cause people to confuse it with aircraft landing lights.
Clear Skies
Joe Slomka
This is Dudley Observatory's Skywatch Line for Friday, January 19, through
Sunday, January 21.
by Alan French
The Moon was new at 11:01 PM on Thursday, so a lovely crescent Moon will be
moving back into the early evening sky this weekend. It will be very
difficult to spot on Friday night, but will be higher in the sky and easy to
spot on the following nights.
To spot a very young Moon on Friday night, you'll need a superb view of the
southwestern horizon free of clouds and haze, and you'll want to look at
5:05 PM. You may also need a pair of binoculars. First, look for Venus
thirteen degrees above the south southwestern horizon. Once you've found
Venus, use your binoculars to scan along the horizon just right of Venus.
If the skies are clear, you should pick up a very slender crescent Moon
about four degrees to the right of Venus. Also look for Mercury – a
starlight point of light just to the right of the Moon.
Early Saturday evening the Moon and Venus will be a very pretty sight low
in the southwest sky. The pair will be just over two degrees apart, and the
best views will be around 5:45. Look for the glow of earthshine faintly
lighting the portion of the Moon not in direct sunlight. Binoculars will
provide a nice view, and should reveal a star just below the Moon and
another right next to Venus. The former is Delta and the latter Gamma
Capricornus.
Look again for the Moon and Venus in the evening sky around 5:30 PM on
Sunday night. The eastern motion of the Moon among the stars will have
moved it higher in the sky and away from Venus. As the Moon moves toward
full the line between the brightly lit and dark portions – known as the
terminator - is the sunrise line. This is where shadows are longest and
detail stands out in bold relief. Any optical aid, from binoculars to an
astronomical telescope, will nicely reveal craters and mountains along the
terminator . The coming week would be a great time to explore the lunar
landscape.
Skywatch line for Thursday, January 18, 2007
by Ray Bogucki
In last Thursday's Skywatch line we described the constellation, Orion the
Hunter, as a slightly irregular rectangle of four stars with a straight line
of three white stars representing the Hunter's belt across the center of the
rectangle. At about 10 p.m., Orion is at its highest point in the sky in the
south. At first glance, we notice that two of Orion's stars are noticeably
brighter than any of the others, Rigel, marking the left foot of the facing
hunter, and Betelgeuse, diagonally opposite Rigel, marking his right
shoulder. A second glance shows us that all of the bright stars in Orion are
blue-white, with the spectacular exception of Betelgeuse, which has a
distinctly orange tinge. One of the rewarding aspects of amateur
observational astronomy is that a considerable amount of information can be
gleaned about stars from a single glance with the unaided eye. For example,
we know that if a star appears bright in our sky, it is either, a) relatively
close to us in the galaxy, or b) extremely large in size or exceptionally
bright in luminosity or both. Blue-white Sirius, the brightest star in the
sky, lying a little below Orion, is only a little larger and more luminous
than our Sun, but, at only 9 light-years distant, it is one of our closest
stellar neighbors. On the other hand, Rigel, appearing only slightly less
brilliant than Sirius, is 100 times farther away but is a huge, young,
blue-white giant that is forty-thousand times more luminous than our Sun. If
we could bring Rigel in to the distance of Sirius, it would cast as much light
as the full Moon and brighten the night sky, so that all but the brightest
stars would be washed out.
The colors of the stars give us an approximation of the star's surface
temperature and relative age. The blue-white color of Rigel and Sirius tells
us that those stars are very young and very hot -- at least ten thousand
Kelvin degrees, while the orange color of Betelgeuse tells us that it is in
the old age of its life with a much cooler temperature, probably near three
thousand degrees. Cooler red stars are intrinsically much less luminous than
hot, blue-white stars, and show considerable variation in brightness. This
variation is caused by a periodic unstable swelling in size followed by a
collapsing back to a quiescent, smaller size. Betelgeuse is about 500
light-years distant, and for it to appear in our sky almost as bright as Rigel,
it must be staggeringly large in size. Our own Sun is a little less than one
million miles in diameter, but, in its small, quiescent state, Betelgeuse is
over 300 million miles across, large enough to fill up our Solar System out to
the orbit of Mars. In its swollen state it grows to about a billion miles
across, which would bring it out near the orbit of distant Jupiter. This
incredible story boils down to the fact that Betelgeuse is the single, largest
object that can be taken in by the human eye. More amazing facts on Orion
next week.
This is the Dudley Observatory Skywatch Line for Tuesday, January 16th,
2007, written by Steven Russo, Planetarium Manager of the Suits-Bueche
Planetarium at the Schenectady Museum.
Sunrise today was at 7:23 AM, and it set tonight at 4:46 PM. Sunrise
tomorrow is at 7:22 AM, and Sunset tomorrow is at 4:47 PM.
The Moon is currently in a waning crescent phase, with the New Moon on
Thursday the 18th. This means that currently, the Moon is visible in
the morning sky. It rose today just after 5:30 this morning, and it set at just
before 2:00 this afternoon. Tomorrow, the Moon will rise at 6:34 AM, and will
set at 2:56 PM.
Look towards the west starting at around 5:15 PM, and you may see a very
bright star-like object. This will be the second planet from the Sun; Venus.
It is the brightest object in the Solar System, after the Sun and the Moon, and
can even be seen in daylight if you know where to Look.
The Planet Saturn, in the constellation of Leo the Lion, is in good view
in the east by 9:00 PM. At that time, the Winter constellations of Orion,
Taurus, and the Seven Sisters are high up in the east. Orion is easily
recognizable by the three stars in a straight line. Those stars make up the
famous “Belt of Orion”. This constellation is visible in the east starting at
around 6:00 PM. Taurus and the Seven Sisters are higher up in the sky at that
time.
Jupiter and Mars can be found in the eastern sky before Sunrise. Jupiter
is higher up in the sky, and is the brighter of the two planets and near the
reddish star known as Antares. Mars, is lower to the horizon. At that time, the
Big Dipper is just about directly overhead.
Public Programs at the Suits-Bueche Planetarium at the Schenectady
Museum, are Tuesdays through Fridays at 2:00 PM, and Saturdays and Sundays at 1,
2, and 3 P. M. The 1:00 program is “The Sky Above Mister Rogers Neighborhood”,
a program for young people. At 2 P. M. is “More Than Meets The Eye”, and at 3 P.
M. is a live narration of the Winter Sky.
This is Dudley Observatory's Skywatch Line for Friday, January 12, through
Sunday, January 14.
by Alan French
Comet McNaught, which made a brief but impressive appearance in the evening
sky just after sunset is now too close to the Sun to see, and will be a
southern hemisphere object when it begins its journey away from the Sun.
The weather promises to be cloudy this weekend, so we'll talk about some
cloudy night activities for the sky watcher.
There are many great web sites for casual sky watchers and amateur
astronomers. One excellent site is www.heavens-above.com, which allows you
to get satellite predictions for your location. Once you are at the
website, you can either register as a user, or stay an anonymous user and
simply "Select your location from our huge database." Then click on "U" in
the alphabet tool bar to get to United States of America. Click on that,
and then enter just the same of your town – no state. You will get a list
of all towns with that name. Select your town from the list, and you're set
to get predictions for satellite passes visible from your home. You'll also
see a "neighbors" link if you want to zero in on your location a bit better.
Perhaps you live in the Bellevue section of Schenectady, for instance.
The brightest satellite visible over our area is the ISS or International
Space Station. The Iridium flares are quite interesting, and very location
specific. The Iridiums are satellite communications satellites, and they
have a very reflective antenna. If the angle is just right, the antenna can
reflect sunlight down to you and the satellite will briefly appear brighter
than Venus. When you look at the predictions for your location, look for
those with magnitudes from –4 to –9. Those of –8 and –9 are extremely
impressive.
If you want to see some of the best photographs of the night sky in
existence, visit the web site of astrophotographer Robert Gendler at
www.robgendlerastropics.com Not only does Dr. Gendler have visual treats
for you, but his site also includes great essays on more than 100 of these
beautiful nebulae, star clusters, and galaxies. It is a wonderful place to
spend a cloudy night.
Skywatch line for Thursday, Jan. 11, 2007
by Ray Bogucki
We are now well into the long nights of winter observing. More than
fourteen hours pass between sunset and sunrise the next morning. Counting
only the hours of full darkness between the end of evening twilight and the
beginning morning twilight, we count more than eleven hours. Recall that in
June we have barely five hours of full darkness. Indeed, evening darkness
arrives so early that it catches Lyra, Deneb and Altair, the three bright
stars of the "Summer Triangle", still lingering in the west, preparing to
set. Altair, the southernmost star of the "Summer Triangle" is low on the
western horizon, and the night is long enough for Altair to pass beneath our
feet and reappear rising in the east, as morning twilight brightens the sky.
Winter's answer to the "Summer Triangle" is the "Winter Hexagon" or "Winter
Oval", a much brighter and more spectacular grouping of stars. By 8 p.m.,
blue-white Sirius, in Canis Major, the brightest star anywhere in our sky, has
cleared the eastern horizon and is rising into the winter darkness. To the
left and a little above Sirius is bright Procyon, in Canis Minor. Moving
upward we encounter the two close, first-magnitude stars Castor and Pollux in
Gemini the Twins. Higher, and to the right, at the top of the oval, lies
brilliant yellow Capella in Auriga the Charioteer. Dropping down we encounter
Aldebaran, the orange eye of Taurus the Bull, followed by the blue-white giant
star Rigel in the foot of Orion the Hunter. Thence back to Sirius to complete
the oval. The "Winter Oval" includes and encloses the greatest concentration
of bright stars to be seen from Earth. The constellation Orion is especially
spectacular. Because it sits astride the celestial equator and is visible
from every inhabited spot on Earth, Orion is probably the best-known of all
constellations. It presents a reasonable figure of the hunter with both
shoulders and both feet marked by bright stars. His belt is clearly marked by
three bright stars in a straight line, and a long curve of medium stars marks
the shield held in his upraised left arm as protection against the attacking
Taurus the Bull. His upraised right arm holds a club and a line of faint
stars marks the sheath of a sword dangling down from his belt. To sit quietly
and absorb the brilliance of this collection of stars is the epitome of
stargazing. In next Thursday's Skywatch line, we will examine several of the
individual objects in Orion.
This is the Dudley Observatory Skywatch Line for Tuesday, January 9th,
2007, written by Steven Russo, Planetarium Manager of the Suits-Bueche
Planetarium at the Schenectady Museum.
Sunrise today was at 7:25 AM, and it set tonight at 4:38 PM. Sunrise
tomorrow is at 7:25 AM, and Sunset tomorrow is at 4:39 PM.
The Moon is currently in a waning gibbous phase, with the Last Quarter
Moon on Thursday the 11th. The Moon rises tonight at 11:06 PM, and
sets just before 11:00 A. M. tomorrow.
The very bright planet Venus can be found very low in the west after
Sunset. You will need a nice clear horizon, but look next time when skies are
clear. Venus is the third brightest object in the Solar System, after the Sun
and the Moon, and is bright enough to see during the day if you know exactly
where to look. It will appear as a very bright star-like object.
The Planet Saturn, in the constellation of Leo the Lion, is in good view
in the east by 9:00 PM. At that time, the Winter constellations of Orion,
Taurus, and the Seven Sisters are high up in the east. Orion is easily
recognizable by the three stars in a straight line. Those stars make up the
famous “belt of Orion”. This constellation is visible in the east starting at
around 6:00 PM. Taurus and the Seven Sisters are higher up in the sky at that
time.
Jupiter and Mars can be found in the eastern sky before Sunrise. Jupiter
is higher up in the sky, and near the reddish star known as Antares. Mars, is
lower to the horizon. By next week, the Moon will be near these two planets.
Public Programs at the Suits-Bueche Planetarium at the Schenectady
Museum, are Tuesdays through Fridays at 2:00 PM, and Saturdays and Sundays at 1,
2, and 3 P. M. The 1:00 program is “The Sky Above Mister Rogers Neighborhood”,
a program for young people. At 2 P. M. is “More Than Meets The Eye”, and at 3 P.
M. is a live narration of the Winter Sky.
This is the Skywatch Line for Monday, January 8.
by Joe Slomka
The Sun sets tonight at 4:38; night falls at 6:20 PM. Dawn breaks at 5:44
tomorrow morning, ending with sunrise at 7:26 AM.
As the Sun sets, Venus blazes close to the western horizon. This begins a good
apparition for the Capital District. Venus appears small, but nearly “Full.” As
the month wears on, Venus appears larger but thinner.
No other bright planets grace the sky until Saturn rises. By 10 PM, Saturn is
well up; midnight is ideal to see this star party favorite. Venus and Saturn
begin the year at opposite sides of the sky, but by June 30 they are found close
to each other. Saturn occupies Leo the entire year, hovering around the star
Regulus.
A twenty-day-old Moon floats between the East and Saturn.
Jupiter rises an hour before Dawn. Shortly before Sunrise, three brilliant stars
occupy the brightening sky. Saturn is low in the West; the Moon hovers low over
the southwestern horizon. Bright Jupiter is moderately high in the East, while
dimmer Mars is below and east of Jupiter. This group spans 120 degrees of sky.
Astronomy burst into the news last week, when a meteorite crashed through the
roof of a New Jersey house. The object was described as golf ball sized but
heavy. Initial examination ruled out aircraft or space debris. Preliminary study
by geologists and astronomers indicate it is an iron meteorite. Such events are
not unusual. In 1992, a meteorite totaled a Peekskill, NY, car; two houses in
Wethersfield, CT, suffered meteorite damage in the 1970s.
The meteorite was probably from the Quandrantid meteor shower, which was active
when the meteor fell. In 1835, it was the first meteor shower to be identified.
Most meteor showers are named for constellations. However, the Quadrantids are
named for a failed constellation. Quadrans Muralis was invented in 1795 by the
French astronomer La Lande. It was located between Draco and the handle of the
Big Dipper. The constellation never caught on and is not official. A normally
bright meteor shower, the Quadrantids were not observed much, this year, due to
the Full Moon that unfortunately coincided.
This is Dudley Observatory's Skywatch Line for Friday, January 5, through
Sunday, January 7.
by Alan French
The Sun now sets around 4:37 and rises at 7:27. We are past the winter
solstice, so the days are slowly getting longer.
The Moon was full last Wednesday, so a waning gibbous Moon will dominate
much of the night sky over the weekend. The fat gibbous Moon will be a
pretty sight as it rises in the east over the weekend. The Moon will rise
at 6:50 PM on Friday night, 7:58 on Saturday, and not until 9:03 PM on
Sunday night. The Moon will still be in the sky after sunrise, and the pale
Moon against the blue sky will be a pretty sight low in the west around 9:00
AM each morning.
On Saturday night, the Moon will be near Saturn and very close to the bright
star Regulus. In parts of the world – Antarctica and the southeast Indian
Ocean – the Moon's eastward motion will move it in front of or occult
Regulus. We'll have to settle for two close together in the sky.
Look for the Moon in the east at 9:00 PM on Saturday night. The bright star
almost five degrees above and to the right of the Moon is the planet Saturn.
For reference, remember that the Moon itself spans one-half a degree. Less
than two degrees below the Moon is Regulus, the brightest star in the
constellation Leo, the Lion. As the Moon and Regulus move higher in the sky
the eastward motion of the Moon among the stars will bring it closer to
Regulus. By 11:00 PM, they will be only one degree apart. They will only
get slightly closer as the Moon passes Regulus.
If you have binoculars or a small telescope take a look at the Moon. It is
a lovely sight with any optical aid. Note the craters and mountains along
the border between sunlight and darkness, where shadows are longest and
details stand out in bold relief. Toward the opposite side of the Moon, the
Sun is high in the Moon's sky, and it is the albedo or brightness features
that stand out best. Look for rays of lighter material extending outward
from some of the craters.
Skywatch line for Thursday, January 4, 2007
by Ray Bogucki
The recent celebration of New Year's Day might lead us to ponder the precise
astronomical meaning of the terms "year" and "day" on Earth and other Solar
System bodies.
The term "day" has two astronomical meanings. The "solar day" is a measure
of the time between the Sun's precise crossing of the southern meridian on two
successive days, or more intuitively, between the moment of sunrise on two
successive days. Because humans are diurnal creatures, we base our day on the
rising and setting of the Sun so that we are active during the sunlit hours,
and sleep at night. Thus, the solar day is our standard 24 hour day.
On the other hand, if we measure the precise time interval between the
appearance of a bright star, say Sirius, at the same spot on two successive
nights, we find that the interval is 23 hours and about 56 minutes. This
interval, based on the locations of stars, is known as a sidereal day. In
other words, the fixed stars rise four minutes earlier each night. This
discrepancy occurs because in that one day interval, the Earth has traveled
almost one degree in its orbit around the Sun, moving the Sun slightly
westward against the background stars. Inasmuch as all stars rise four
minutes earlier each day, this calculates to a half-hour earlier each week and
two hours earlier each month. To confirm this behavior, step outside this
evening, say at 8 p.m., and note the location of the bright, sparkling
constellation Orion, well up in the southeast. Then, a month later, in early
February, return to the same spot at the same time and you will find Orion
high in the south, two hours west of where it was in January. Thus, in 12
months, the slow, steady westward motion of the stars has all of the
constellations visible from our area pass in stately review for our inspection
and observation, returning in one year to their starting point.
The "year" is defined as the interval of time required for the Earth to make
one complete orbit around the Sun. As early as the time of Julius Caesar, it
was known that this time interval was 365 days plus about 6 hours. That means
that in two orbits (or years) the Earth requires an extra 12 hours, and in
four years, an extra 24 hours, or one day. In 46 BC, following the advice of
the Alexandrian astronomer, Sisogenes, Caesar adopted a new calendar in which
every fourth year, known as a leap year, would have an extra day inserted at
the end of February. But, because the extra interval is not exactly six
hours, the date of the vernal equinox dropped back about one day in each
century. To correct this, Pope Gregory XIII modified the Julian calendar by
dropping 3 leap years in every 4 centuries. Further minor modifications have
given us a current calendar which is accurate to one day in 44,000 years. In
our electronic society, we will probably soon have a calendar accurate to one
second in a million years!
A Fine ISS Pass Tonight (Wednesday, January 3)
There is a nice ISS pass over our area tonight, and a chance we'll even have
clear skies. The times below are for Schenectady, but should be close
enough for anyone in the Capital District. You can get exact times by
visiting www.heavens-above.com and selecting your town from the huge
database.
This pass will go essentially overhead. The Sun will only be 8 degrees
below the horizon, so the sky will still be fairly bright, and only the
brightest stars will be visible. The ISS is brighter than most of the stars
in the evening sky, and should be very easy to spot as it moves up from the
northwestern horizon. If you miss it at first appearance, look high
overhead at 5:21 PM.
Clear skies, Alan
Wednesday, 03 Jan, magnitude -1.0
Appears at 5:18:43 PM above NW horizon
Highest at 5:21:33 PM when 81 degrees above NE horizon
Vanishes at 5:24:22 below ESE horizon
This is the Dudley Observatory Skywatch Line for Tuesday, January 2nd,
2007, written by Steven Russo, Planetarium Manager of the Suits-Bueche
Planetarium at the Schenectady Museum.
Sunrise today was at 7:26 AM, and it set tonight at 4:32 PM. Sunrise
tomorrow is at 7:26 AM, and Sunset tomorrow is at 4:33 PM. We are now past the
shortest days of the year, and the days will now lengthen by about a minute or
so each day. This increase in daylight will not be noticeable on a day by day
basis, but by the end of the month, we will have almost an hour more daylight
then we do now.
The Full Moon is tomorrow, so we have a Waxing Gibbous Moon tonight. It
rises at 3:22 PM, and will set tomorrow morning just before 8:00 AM.
The very bright planet Venus can be found very low in the west after
Sunset. You will need a nice clear horizon, but look next time when skies are
clear. Venus is the third brightest object in the Solar System, after the Sun
and the Moon, and is bright enough to see during the day if you know exactly
where to look.
The Planet Saturn, in the constellation of Leo the Lion, rises by 9:00 PM
in the northeast. The Moon will be near Saturn on Friday and Saturday nights.
The Winter constellations of Orion, Taurus, and the Seven Sisters are high up in
the east.
Mercury, Jupiter, and Mars are all together within a few degrees of each
other low in the East before Sunrise.
Public Programs at the Suits-Bueche Planetarium at the Schenectady
Museum, are Tuesdays through Fridays at 2:00 PM, and Saturdays and Sundays at 1,
2, and 3 P. M. The 1:00 program is “The Sky Above Mister Rogers Neighborhood”,
a program for young people. At 2 P. M. is “Tis the Season”, and at 3 P. M. is a
live narration of the Winter Sky.
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