To the reader:
The Skywatcher's Diary for June 2002 has been prepared by
David Batch. Credit to the author and to
Abrams Planetarium,
Department of Physics and Astronomy at
Michigan State University, and mention of
our
Sky Calendar, would be
appreciated.
A sample issue of the Sky Calendar is available over the Internet. It
can be viewed via the World-Wide Web at
http://www.pa.msu.edu/abrams/SkyCalendar/Index.html
If you would like a printed sample of the June issue, please send a long,
self-addressed stamped envelope to:
June Sky Calendar
Abrams Planetarium
Michigan State University
East Lansing, MI 48824
Each month, the Department of Physics and Astronomy at Michigan State
University makes the Skywatcher's Diary available over the Internet. It can
be accessed at
http://www.pa.msu.edu/abrams/SkyWatchersDiary/Diary.html
Current and back-issues of the Skywatcher's Diary are available in our
archives
at
http://www.pa.msu.edu/abrams/SkyWatchersDiary/Archives.html
ftp://www.pa.msu.edu/pub/swd/
Skywatcher's Diary: June 2002
The planetary highlight of June occurs early in the month. The two brightest
planets, Venus and Jupiter, dance together over the next several evenings.
Tonight, an hour after sunset, the two stand side-by-side, 15 degrees (1 1/2 fists)
above the west-northwest horizon. Venus, 7 times brighter than its giant
companion, is on the right. It is also the faster moving of the pair. Watch Venus
swing above and to the left of Jupiter over the next several nights.
Are you able to detect the motion of Venus relative to Jupiter since last night? The
two planets are half a degree (1 moon diameter) closer together and Venus is
noticeably higher.
The Moon reaches Last Quarter tonight at 8:05 p.m. EDT. Don't expect to see it at
the exact moment, though, since that phase is generally visible in the midnight-to-
noon segment of the day. Enjoy Luna in the morning, before or after sunrise.
The two dazzlers, Venus and Jupiter, are closest tonight - 1.7 degrees (3 moon
diameters) separation. This is the brightest planet pairing of the year. The
proximity of the two bodies in our sky is, of course, an optical illusion of sorts.
Venus is a foreground object, much nearer to us than Jupiter. The light from
Venus takes only 11 minutes to arrive at our eyes, whereas we see Jupiter the
way it appeared 50 minutes earlier. Continue watching over the next several
nights.
With Venus and Jupiter commanding the attention, it's easy to overlook Mars. The
Red Planet still inhabits the evening sky, but just barely. An hour after sundown
the planet sits 5 degrees above the west-northwestern horizon and 12 degrees (a
fist width) to the lower right of Jupiter. To make matters more difficult, Mars is only
2nd magnitude, near its minimum brightness. If you have a clear night (no haze)
and an obstruction-free view to the west, Mars may still be visible to the unaided
eye. Use binoculars to initially locate the faint planet.
Venus climbs farther away from Jupiter each night, although it appears nearly
stationary relative to the horizon. The apparent motion of Venus seems to offset
the downward slide of the background stars. The stars' drift will be apparent if you
watch the Gemini Twins. The bright star Pollux is 6 degrees (half a fist) above and
slightly to the right of Venus. Castor is 5 degrees to the right of his twin. Each
night at the same time, the Twins appear slightly lower than the previous night
(and closer to Venus). The Earth's orbital motion produces the stars' apparent
descent.
The Earth's motion causes Jupiter, along with the background starfield, to slide
lower in the west each night. By month's end Jupiter approaches Mars, which
also descends, but at a slower rate. Its orbital motion is greater than the giant
planet's, so Mars does a better job of staving off the effect produced by our
planet's orbital swing. Knowing all of this solar system mechanics is not
necessary, of course, to enjoy the sight of the ongoing celestial pageant.
Pluto, the ice ball planet, reaches opposition today, signifying that the Earth now
lies between it and the sun. More useful for observing this remote cosmic speck
is the knowledge that Pluto currently stays up all night. Pluto is always a
challenge to find. It is more than one thousand times fainter than what the
unaided eye can detect, so you need a detailed finder chart showing exactly
where to look and at least an 8-inch telescope, although the bigger the better.
For an example chart, see
http://skyandtelescope.com/observing/objects/planets/article_412_1.asp
Look for the thin crescent Moon this morning ahead of sunrise. It's the last easy
sighting of the Moon before it turns New. Tomorrow morning the Moon can still be
glimpsed but requires more effort. Look, then, 30 minutes before sunrise and just
3 degrees (not much more than the width of your index finger) above the east-
northeastern horizon. A transparent sky, uncluttered horizon, and binoculars will
assure success.
Saturn disappeared from the evening sky nearly a month ago. Today it is in
conjunction with the sun, which means it lies invisibly beyond that body. In the
coming weeks, the orbiting Earth causes the Ringed Planet to emerge from
behind the sun and drift to the right (west), reappearing in the morning sky, rising
ahead of the sun, by month's end. Saturn returns to the evening sky in late fall.
New Moon occurs at 7:46 p.m. EDT. Today the Moon passes directly in front of the
sun as seen from areas of the Earth. Because Luna currently appears smaller
than the sun, the eclipse will nowhere be complete, or total. Instead a bright ring
of sunlight (annulus) shows at maximum eclipse for observers on a line
extending from Indonesia to Mexico. The U.S., except for the east coast, will
witness various stages of a partial solar eclipse. Caution: this eclipse requires
eye protection or special techniques to view safely. Safety information and specific
timings for various cities can be found at
http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2002.html.
(For all of Michigan but the western end of the U.P. the eclipse is in progress at
sunset. For central and southern L.P. the eclipse begins about 8:30 p.m. EDT and
approximately 25% of the sun's diameter will be covered at maximum.)
A young Moon, only 26 hours old, awaits early skywatchers this evening. Look for
the beautifully fragile crescent 30 minutes after sunset in the west-northwest. It
then sits 4 degrees (8 moon diameters) above the horizon. Jupiter is 15 degrees
(1 1/2 fists) to its upper left, and Venus is another 8 degrees to the upper left of
Jupiter. Faint Mars will be easy to miss, between the Moon and Jupiter, 6 degrees
from Luna and 9 degrees below Jove. Use binoculars. Overnight, invisible to us,
the Moon occults (passes in front of) the Red Planet.
The crescent Moon parks beside Jupiter tonight. Soon after sunset look for Luna
3 degrees (six moon diameters) to the right of the giant planet. Tomorrow night
the Moon hops up to Venus, sitting 2 degrees above this dazzling planet. These
two evenings provide an opportunity to spot Venus and possibly Jupiter in daylight
(before sunset) by using the Moon as a guide.
Look for "earthshine," the dusky glow on the dark portion of the Moon. Can you
detect patterns of light and dark within the earthshine? Try it with binoculars.
While you have binoculars trained in that direction, look for the 4th-magnitude star,
Delta, in Gemini, 1 degree below Jupiter.
The Equation of Time is zero today. Practically speaking, this fact has little value
unless sundials interest you. The Equation of Time provides a measure of the
difference between the apparent sun, the one we see in the sky, and the mean
sun, a fictitious entity that our timekeeping was built upon before the advent of
atomic clocks. The bottom line: today a properly constructed and adjusted sundial
will agree with clock time.
The earliest sunrise of the year occurs today (exact for latitude 40 degrees North
but true within a minute for everywhere in the continental U.S.). Contrary to
intuition, the earliest sunrise, longest day, and latest sunset do not coincide. The
longest day occurs on the solstice and the latest sunset happens on June 28. A
similar range of dates marks the earliest sunset, shortest day, and latest sunrise
in December. The cause has a lengthy explanation, but it is related to the Earth's
orbit being elliptical rather than circular.
The Moon is among the stars of Leo, the Lion, over the next 3 evenings. Tonight it
sits 4 degrees (8 moon diameters) to the upper right of Regulus, the heart of the
beast and brightest star in the constellation. Tomorrow night the crescent lies
under the mighty cat's belly. By Monday the First Quarter Moon perches 10
degrees (a fist) to the lower left of Denebola, a 2nd-magnitude star that marks the
animal's tail. Technically, that night Luna has moved across the boundary into
Virgo.
Do you recall when Venus was below the bright pair of stars, Pollux and Castor,
the Gemini Twins? Look 10 degrees to the right of the planet and a few degrees
below to find the stars tonight. Venus passed the Twins on the 13th. The next
bright object on its path is Regulus. Venus slides a degree to the right of that star
on July 9 and 10. The planet is currently among the stars of the faint constellation
Cancer, the Crab. It slips into Leo on June 29.
The Moon passes First Quarter at 8:29 p.m. EDT. The Summer Triangle, that
signpost of the summer sky, is now complete, an hour after sunset. Vega, the
most luminous of the trio, sits almost half way up in the east-northeast. Look for
Deneb in the northeast a quarter way up. Altair is the trickiest to locate because it
perches only 14 degrees off the eastern horizon. If you have difficulty with this last
one, wait an hour and try again when it is higher. If you are not familiar with the
Summer Triangle, learn it soon. It is the key to summer stargazing.
For a star map to help locate these stars, send a self-addressed, stamped
envelope to Sky Calendar, Abrams Planetarium, Michigan State University, East
Lansing, MI 48824.
Fifteen degrees (fist and a half) separate the two brilliant planets, Venus and
Jupiter. An hour after sunset Jupiter rests 4 degrees above the west-northwest
horizon, with Venus to its upper left. The Gemini Twins are 13 degrees to Venus'
lower right and 7 degrees above and slightly to the right of Jupiter. Mars, only 2nd
magnitude, sits 6 degrees to Jupiter's lower right and only 1 degree off the
horizon. The Red Planet is challenge. Use binoculars and start 15 minutes earlier
if Mars is your mission.
Look for Spica, the brightest star in Virgo, 6 degrees (12 moon diameters) to the
lower right of the waxing gibbous Moon this evening. The star is considered the
standard example of 1st-magnitude, since its average value is 0.98. The star is a
multiple system, showing evidence of 4 stars. The brightest component is blue-
white, indicating its temperature is more than 30,000 degrees Fahrenheit, so
Spica is intrinsically much hotter and brighter than our sun. Its 260-light year
distance conceals the true luminosity. The sun at that same distance would
appear only 9th magnitude, far fainter than what we can see with unaided eye.
Examine the vicinity of Venus carefully with binoculars, once the sky becomes
dark, about 1 1/2 hours after sunset. The brilliant planet passes less than a
degree to the upper right of the Beehive, or Praesepe, star cluster. Astronomers
designate it an "open cluster," meaning the group is a relatively loose collection of
stars that resides in the plane of the Milky Way galaxy. The cluster contains
several dozen stars that are gravitationally linked to one another. The group is just
visible to the unaided eye from a dark location (and when Venus is not so close)
as a faint, fuzzy "star." Tomorrow night Venus is more than a degree to the
Beehive's upper left.
Happy Summer! The season of sunshine and vacations officially begins at 9:24
a.m. EDT. Today also marks the longest day of the year, about 15 hours for the
northern U.S. To celebrate, watch a sunrise or sunset with someone you care
about.
Today Mercury reaches its greatest western elongation from the sun. Even though
23 degrees separate the sun and the planet, the tilt of the sun-Mercury line
relative to our horizon makes Mercury difficult to see from the northern latitudes. If
you wish to try, look 45 minutes before sunrise very low in the east-northeast. Use
binoculars. Next week the planet is a magnitude brighter and slightly higher,
making success more likely.
Tonight the Moon points to another major star of the summer skies. Look 5
degrees below and slightly to the right to find ruddy Antares. Because the star
never attains much altitude as seen from northern latitudes, this heart of the
scorpion is easily overlooked. Currently, the magnificent red supergiant reaches
maximum height above the horizon near midnight. That time decreases by 2
hours per month, so next month the red beauty is best seen around 10 p.m.
Draco, the Dragon, is one of those constellations often recognized by name but
seldom identified in the sky, principally because it is faint - 3rd and 4th-magnitude
stars comprise the snaky body. Early evening this time of year the dragon is nicely
placed for viewing. Start with 2nd-magnitude Eltanin, or Gamma, the brightest of
the group. First locate Vega, the brightest star in the east, about halfway up.
Eltanin is 15 degrees (1 1/2 fists) to the upper left of Vega. The winding body
drops down to almost the height of the North Star, then curves back up and over
the cup of the Little Dipper, passing between it and the Big Dipper. A good star
map will illustrate the shape. See, for example
http://www.astro.wisc.edu/~dolan/constellations/java/Draco.html.
The Moon is Full at 5:42 p.m. EDT. An insignificant penumbral eclipse of the Moon
occurs for the Eastern Hemisphere, although probably not visible, even to
experienced observers. The Moon passes close to the 3rd-magnitude star
Lambda, in Sagittarius, tonight. That's the star that marks the top of the "teapot's
lid." Use binoculars during dusk and search above and very near Luna. Watch the
Moon's motion by the minute. For observers in the southeastern U.S. the Moon
occults (covers) the star.
The Moon rises tonight an hour after sunset and the following night about 2 hours
after sundown. We are entering the two-week period of dark, moonless evening
skies. The summer Milky Way is just launching its wondrous show. Look for the
faint river of light flowing from north to south and reaching halfway up in the east.
Scan its length with binoculars, pausing to carefully examine those hazy patches
that catch your eye.
Jupiter's evening show is finished. The planet sets about an hour after sunset. If
you want to bid goodbye, catch it 15 to 30 minutes earlier, low on the west-
northwest horizon. Use binoculars. You might like to hunt for Mars, only 2nd
magnitude and 3 degrees to the lower right of the giant planet. Without Jupiter to
point the way, you would have little hope of sighting the Red Planet this low. The
Gemini Twins are 6 degrees to the upper right of Jupiter.
Mercury is 0th magnitude now, but very low in the morning sky. Forty-five minutes
before sunrise it sits 4 degrees up in the east-northeast. The star Aldebaran is 6
degrees to the planet's right. Saturn is emerging from its trip behind the sun. For
the moment it trails Mercury 6 degrees to the lower left. By July 2 Saturn will catch
Mercury, passing 0.3 degrees to its upper left. Thereafter the Ringed Planet
continues upward, all the while becoming easier to view, while Mercury dips back
into twilight and disappears.
The waning gibbous Moon sits 5 degrees (10 moon diameters) to the lower left of
Uranus this morning before sunrise. This 6th-magnitude planet requires optical
aid and a finder chart to pick out, although technically it qualifies as a naked eye
object. In amateur telescopes, it resembles a faint blue dot, at best. The Moon is
16 degrees (1 1/2 fists) to the upper right of Fomalhaut, the most frequently
forgotten 1st-magnitude star. Tomorrow morning Fomalhaut is 17 degrees below
and slightly right of Luna.
At the first hint of light in the morning sky, the Summer Triangle hangs high in the
west. The Great Square of Pegasus, a familiar evening autumn constellation, can
be spotted high in the southeast. The familiar wintertime stars are starting their
morning reappearance. An hour before sunrise the bright star Capella sits 18
degrees (2 fists) up in the northeast. Next to emerge is Aldebaran, eye of Taurus,
only 3 degrees up in the east-northeast at that hour. Orion and Gemini rise
invisibly just after sunup.
Ophiuchus, the Serpent Charmer, lies halfway up in the southeast at the end of
evening twilight. This faint pattern is often called the "13th zodiac constellation"
because the sun stays longer within its boundaries than it spends in Scorpius.
The brightest star in the group is 2nd-magnitude Rasalhague (ras-al-hag'-wee),
head of the giant. Look for it 50 degrees up in the southeast. It nearly makes an
equilateral triangle with Vega and Altair, the western side of the Summer Triangle.
Use a star chart to trace the rest of the constellation, which flows toward Antares,
in the south-southeast.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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