To the reader:
The Skywatcher's Diary for June 2005 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
Skywatchers Diary: June 2005
- Early risers enjoy the Moons company for the next four mornings. The waning
crescent drifts lower and farther northward (left) of its position from each previous
morning until dissolving into the suns glow by the 6th. Tomorrow morning, an
hour before sunrise, Luna perches 15 degrees (1 1/2 fists) above the eastern
horizon. On the 5th (Sunday) at the same time it sits only 1 degree up in the east-
northeast, next to the Pleiades (use binoculars).
- Observers with access to a telescope may wish to tune in to Jupiter late tonight
and early tomorrow morning. The shadows of two of Jupiters large moons will
appear projected onto the disk of the giant planet. First, Europas shadow shows
up shortly after 10:42 p.m. EDT. At 11:34 p.m. Ios shadow joins the other. Both
appear as small black circles against the bright tawny clouds of Jupiter. At 1:22
a.m. Europas shadow leaves the disk, followed 22 minutes later by Ios.
- Mercury reaches superior conjunction with the sun this morning. The planet
passes on the far side of its orbit, crossing slightly above the suns disk this time
around. Mercury is transforming from morning object to an evening one. It
remains out of sight until next week when observers eager to catch the elusive
planet may first pick it up about 10 degrees to the lower right of Venus. As the
month progresses Mercury climbs higher and becomes easier to spot, as it
heads toward a rendezvous with Venus.
- Mars stands alone as the morning planet. Sibling Jupiter sets about 3 hours
ahead of sunrise, and from then until dawn its only Mars. The Red Planet is now
zeroth magnitude, increasing by three-tenths magnitude during June. Mars is still
too distant from Earth to present much of an image in a telescope. For now we
must be satisfied knowing the separation between us and Mars is decreasing
every day.
- Over the last four months Jupiter has appeared to slide slowly westward relative
to the starry backdrop. Astronomers call this "retrograde motion." Careful
observers have watched Jupiter pass the 3rd-magnitude star Gamma in Virgo. As
of today, Jupiters retrograde has ended and the planet now travels eastward, in
"direct" motion. Over the next month, follow the planet trekking past the star again,
in the opposite direction.
- The Moon becomes New at 5:55 p.m. EDT. At that moment, Luna stands 4
degrees north (upper right) of the sun, completely invisible. No solar eclipse
happens anywhere on Earth. The eclipse "seasons," those times when the sun-
Moon alignment is precise enough to allow eclipses, occur in April and October
this year.
- Shortly after sunset, the breathtaking ultra thin Moon makes a brief appearance.
Thirty to 45 minutes after sundown, locate bright Venus about 7 degrees above
the west-northwest horizon. Scan the area 7 degrees to the planets right, and
slightly lower, for a delicate arc of light. The Moon sets a little more than an hour
after sunset, so timing is important. Binoculars may be helpful.
- Tonight the Moon poses 6 degrees (half a fist) above Venus. Add a little twilight
coloration and you have a picture-postcard scene. Saturn perches 14 degrees (1
1/2 fists) to the upper left of Luna. Early observers may have a chance at Mercury.
That planet sits 11 degrees to the lower right of Venus. Twenty minutes after
sunset Mercury is 2 degrees above the spot where the sun disappeared. You will
need binoculars.
- Tonight the crescent Moon nestles between the Gemini Twins and Saturn. The
Ringed Planet lies 5 degrees (9 moon diameters) to the lower left of Luna. Pollux,
the brighter twin, rests 2 degrees to the Moons upper right, and brother Castor
sits 5 degrees to the right of Pollux. Tomorrow night the Moon climbs 11 degrees
to the upper left of Saturn, and lands a few degrees from the Beehive star cluster.
- Now is a good time to try your hand at detecting meteors by radio. Were in the
midst of the strongest daytime radio showers of the year. When a particle creating
a meteor burns up in Earths atmosphere, it leaves behind an ion trail that can
reflect distant FM radio station signals. Tune an FM radio with outside antenna
(car radio works well) to a frequency unused by any local station. The telltale
characteristic of a meteor signal is a quick rise in volume lasting a second or two,
followed by a slower fade.
- Mercury becomes less difficult to pick out of twilight as it climbs toward Venus.
Venus is also drifting toward Saturn. Begin watching all three planets as a group.
The trio now spans 24 degrees (2 1/2 fists) but will squeeze to 1.5 degrees by
June 25. The nightly shift of each planet relative to the others will be intriguing to
observe, particularly during the third week of the month.
- Tonight the Moon hovers near Regulus, heart of Leo. Although still two nights
away from First Quarter, the Moon is bright enough to camouflage Regulus for the
casual observer. Look for the star 3 degrees (6 moon diameters) below and
slightly left of Luna. At this phase the Moon makes a great target for binoculars
and telescope. The craters are particularly evident.
- A well-constructed and properly adjusted sundial will match standard clock time
today. Usually a correction, known as the Equation of Time, must be applied to
sundial time. But four times a year the Equation of Time is zero. The suns
motion, the primary timekeeper for much of human history, is just too variable for
modern needs.
- The Moon reaches First Quarter at 9:22 p.m. EDT. Pluto is now opposite the sun,
so its a good time to look for that distant planet. Youll need a moderate size
telescope, since the planet is only magnitude 13.8. Counter to intuition, the
earliest sunrise of the year occurs today -- seven days before the solstice -- for
those located near 40 degrees north latitude. Similarly, latest sunset occurs after
the solstice, on June 27.
- Luna sidles up to Jupiter tonight. Two degrees (4 moon diameters) separate the
bodies. Can you detect the 3rd-magnitude star Gamma in Virgo, about 3 moon
diameters to the upper left of Jupiter? Tomorrow night the Moon slides 11
degrees to the other side of Jupiter. It then sits 4 degrees to the upper right of 1st-
magnitude Spica, the Alpha star in Virgo.
- Spica, the brightest star near the Moon tonight, is more complex than the
unaided-eye reveals. Spica consists of two hot stars -- one has a surface
temperature of 40,000 and the other 33,000 degrees Fahrenheit. The stars extend
8 times and 4 times the solar diameter, respectively. They orbit about each other
every four days at a separation only one-tenth the distance between Earth and
sun.
- Spicas luminosity is slightly variable. Because the two components of Spica are
so close, the mutual gravitational pull distorts the bodies, tugging them slightly
"out of round." As the stars orbit, they present somewhat different shapes to our
line of sight, which, in turn, causes the total amount of light that reaches our eyes
to vary.
- Mars, now in the southeastern sky before dawn, is in line with the east (left) side
of the Great Square of Pegasus, 15 to 30 degrees (1 1/2 to 3 fists) to the planets
upper left. Because Mars currently clips along at about half a degree a day, soon
you will be able to detect that the planet is no longer aligned with those two stars.
By observing every morning, see how many days it takes for you to perceive a
misalignment.
- If you havent noticed the evening planets Venus, Saturn, and Mercury in a while,
catch them at your first opportunity. They span merely 10 degrees (a fist width),
sitting low in the west-northwest during dusk. Mercury, the lowest of the three,
sets about 1 1/2 hours after sunset, so dont wait too late to observe. The planets
pull closer all week long, and appear only 1.5 degrees apart this Saturday, the
25th. You wont want to miss the impressive choreography of this planetary trio.
- Today Mars crosses the skys equivalent of the equator, moving northward. When
the sun crosses the celestial equator we call it an "equinox." Theres no
corresponding event of note for planetary crossings. In the current situation, the
primary significance is that Mars climbs higher within the zodiac. It, therefore, can
be expected to inscribe a loftier arc across the sky on its daily journey from the
eastern to western horizon.
- The sun reaches its highest point for the year at midday today, for the northern
hemisphere. Known as the Summer Solstice (in the north), the sun swings
directly over the tropic of Cancer at latitude 23 1/2 degrees. The exact moment of
the solstice is 2:46 a.m. EDT. At that moment the sun enters the astrological sign
of Cancer but sits among the stars of the constellation Taurus. Within 7 hours it
crosses the boundary into Gemini.
- The Moon turns Full at 14 minutes past midnight this morning. The Full Moon of
June has been known as the Rose Moon, Strawberry Moon, and Honey Moon,
among other designations. Extra credit question: If the sun is now in the
constellation Gemini, what constellation should the Moon be in? Answer: By
definition the Full Moon is opposite the sun, so it should sit within Sagittarius,
halfway around the zodiac from Gemini.
- The grouping of Venus, Saturn, and Mercury low in the west-northwest after
sunset is not to be missed. Venus, clearly the brightest of the three, occupies the
middle position, with Mercury 1.2 degrees to its lower right and Saturn about twice
that distance to Venus upper left. Can you determine which is brighter between
Mercury and Saturn? Look 45 minutes to an hour after sunset.
- The three planets now congregate within a 2.5-degree area. Thats small enough
to fit easily within most binoculars fields of view. The orbital motions of Venus
and Mercury are carrying them past Saturn, so watch as the Ringed Planet drops
away over the next week. The Gemini stars, Pollux and Castor, sit 5 to 10 degrees
to the upper right of the planets. Dont miss this fine exhibition of planetary
motion.
- The planetary threesome forms its most compact arrangement this evening. The
planets fit within 1.5 degrees. The relative positions of the planets are now
changing significantly. You may need a play by play to keep track. Saturn has
dropped 1.3 degrees to the lower left of Venus. Mercury inches closer to Venus,
tonight sitting half a degree to the latters lower right.
- Mercury and Venus have slid overtop Saturn. The Ringed Planet sits 1.6 degrees
below them tonight. The separation between the tight knit duo more than halved
in 24 hours. Venus and Mercury now are only 0.2 degrees apart. But wait. The
show gets even better tomorrow night. Can you still locate the stars Pollux and
Castor, 8 degrees to Venus right?
- Venus and Mercury appear so close tonight that their apparent separation
depends on whether you view them from the East Coast or the West Coast. From
New York the two are 7 arcminutes apart (6 arcminutes is one-tenth degree). On
the sunny coast of California the separation is 9 arcminutes, and in Hawaii its 10
arcminutes. You are witnessing the closest two-planet grouping (astronomers
call it an appulse) of the year.
- The Last Quarter Moon occurs at 2:23 p.m. EDT. Tomorrow early dawn Luna
appears 4 degrees (8 moon diameters) to the left of Mars. Tonight the planet
dance continues. Mercury has moved 0.4 degrees to the left of Venus. Saturn
appears to slip to the lower right as the other two planets climb above it. The
Venus-Saturn separation reaches 3.5 degrees tonight.
- Mercury continues to pull to the left, away from Venus. The planets are 0.6
degrees apart tonight and 0.8 degrees tomorrow night. Mercury stays close to
Venus for so long because of a lucky coincidence. The speedy planet reaches the
turnaround in its orbit as it pulls in near alignment with Venus, as seen from
Earth. While changing orbital direction, so to speak, Mercury appears to linger in
the vicinity of Venus.
- Catch a last look at Saturn in the evening sky in the next few days. Venus and
Mercury continue their celestial ballet until mid July. If you would like a copy of the
July Abrams Planetarium Sky Calendar that depicts the Venus-Mercury gathering
and other celestial events, send a self-addressed stamped business envelope to
Sample Sky Calendar, Abrams Planetarium, Michigan State University, East
Lansing, MI 48824
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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