July 2005 Skies

July is the first full month of Summer.  Throughout July the length of the day shortens; also each day’s sunrise occurs later in the morning, while sunset is earlier in the evening.

Early July continues the very close conjunction of the evening planets Venus and Mercury. Don’t fail to notice these planets as they remain near each other and bright in early July.

Mars continues to brighten as it moves higher in the night sky and rises earlier each night.

Summer’s spectacular stars and constellations are visible all night in July. The Summer Milky Way also presents a grand sight in binoculars and small telescopes: It rises higher in the Eastern sky with several accessible star clouds and gaseous nebulas.

The Evening Sky
The Sun:
The SUN begins July in the Zodiac constellation of GEMINI the Twins, where it remains until July 20th, when it moves into CANCER, the Crab.

Sunset on July 1st will at 7:36p.m.  Sunset on July 31st occurs at 7:23p.m.

The Moon:
The MOON begins July as a waning crescent in the constellation of ARIES the Ram.  July’s NEW MOON occurs the morning of July 6th in Gemini.  A 1st QUARTER MOON is seen on July 14th in VIRGO.  Astronomically, July’s FULL MOON occurs on July 21st.  However, we will see an almost Full Moon rise just after sunset on the evening of July 20th and ride low in the sky in SAGITTARIUS.  The 3rd QUARTER Moon is on July 27th in Aries, when moonrise is at about 11:45p.m.

July’s Moon will pass near four naked-eye planets:
MERCURY & VENUS: Low in the Northwest the evening of July 8th in Cancer.
JUPITER: Not very close to the Moon on the 12th and 13th in VIRGO.
MARS: The morning of the 27th in PISCES.

The 2 day old Crescent Moon stands directly above Venus after sunset on July 8th.  Venus appears as a VERY bright “star” low in the Northwest, and Mercury will be about 3 Moon diameters below Venus and to the left (South).

Moon & Prominent Stars:
Crescent Moon near Regulus in LEO on the 9th.
1st Quarter Moon between Jupiter and Spica in VIRGO on the 13th.
Waxing Gibbous Moon eclipses (occults) Antares in Scorpio July 17th between 8 - 9p.m.

Evening Planets. Mercury (early in the month), Venus & Jupiter.
Mercury and Venus form a bright pair low in the Northwest after sunset during early July.
Mercury remains far enough from the Sun to be visible through about the 20th, when it sets about an hour after the Sun.  Early in the month look for Mercury simply by finding extra-bright Venus after sunset in the Northwest.  Mercury will be the bright “star” near Venus.

If you observe these planets on several evenings, you will soon be able to predict Mercury’s movement from night to night as it loops past Venus, then down and away from the brighter planet as it heads back toward the Sun. By month-end, Mercury will again be lost in the Sun’s glare.

Through a telescope, Mercury displays a range of phases like the Moon. It begins July in a nearly-Full phase, shrinking throughout the month, and ending July as a thin crescent.

Note that Mercury is almost never easier to observe: It is said that the famous astronomer Copernicus never personally saw Mercury!  Although low in the Northwest sky, Mercury orbits so close to the Sun that this month it is actually comparatively very high in the sky.  For a few days in July the planet sets in a dark sky, an unusual event.

Venus continues to move farther away from the Sun, first passing Mercury.  Between July 21st and 23rd it overtakes and passes the 1st magnitude star Regulus in Leo.  While continuing to move farther away from the Sun, Venus also moves South, making a shallower angle to the horizon.  This means Venus will not move higher in the sky during July or become any easier to observe.  Over the next few months, Venus will catch up with Earth and head back closer to the Sun.

Like the Moon and Mercury, Venus also displays phases.  In July though, it remains nearly-Full.  Through a telescope, Venus grows a bit larger.  Later, when it approaches the Earth, Venus transforms into a much larger, but apparently thinner crescent.

SATURN starts the month very low in the Northwest after sunset. It only sets earlier each day, and soon will be too close to the Sun to be observed.  On July 23rd Saturn passes behind the Sun, only to reappear late in August in our morning sky.

JUPITER, in VIRGO, remains very bright and high in the South after dark.  Earth, in its faster orbit around the Sun, continues to move away from Jupiter.  So, Jupiter lags behind Earth and sets earlier each evening: A few minutes after midnight on July 1st, but about 10:30p.m. – 3 hours after sunset – at month end.

What Else to See?
This month Summer’s distinctive constellations rise earlier each evening and are conveniently visible all night. The sky will be quite dark by 9:00p.m., so early July’s moonless evenings are excellent times to view the night sky.

Vega, in Lyra the lyre, is the brightest star of summer and appears fainter only than Venus, Jupiter and (later) Mars.  Look for Vega high in the Eastern sky after dark. Below Vega is Deneb in Cygnus the Swan (or Northern Cross).  To the right (South) of Deneb is Altair in Aquila the eagle.  Together, Vega, Deneb and Altair form the “Summer Triangle” of Summer’s bright stars.  Another distinctive July constellation is Scorpio the zodiac scorpion.  By 9:30p.m. Scorpio’s “tail” and “stinger” stars are above the horizon.  Observers with binoculars or a small telescope can view two dense star clusters a bit to the East (left) of the scorpion’s tail.

As the Moon slowly moves from West to East around the Earth each month, it occasionally occults (or eclipses) background stars.  A spectacular occultation occurs just after dark on the evening of July 17th:  The nearly Full Moon will occult the bright red star Antares in Scorpio’s heart. The show starts just at the end of twilight, so should be easy to observe even with the unaided eye. (About 90 minutes later the Moon also occults a fainter trailing star.)

The Moon also occults several other stars of 6th magnitude or brighter during July.  However, except for Antares, a small telescope will be needed to watch these events. See details here.

One excellent way to learn and view the Summer sky is by attending a “star party”.  These events feature knowledgeable astronomers pointing out prominent stars and constellations.  Also, typically, several telescopes are set up for public viewing of interesting objects.

Tony and Carol LaConte’s professional skygazing team presents FREE public skygazing events at several Valley mountain parks and other venues during summer months!  This team always brings along several telescopes for free and entertaining viewing.  The skygazing show is FREE, although Valley mountain parks charge a low admission fee per carload.  A schedule of these skygazing events is available here.

The East Valley Astronomy Club hosts a FREE public star party on Friday evening, July XX next to the Gilbert Public Library, starting at Yyp.m.  Click here for details.

The Morning Sky
Sunrise on July 1st is at 5:26a.m. and each morning afterward the Sun rises a bit later.  July 31st’s sunrise occurs at 5:44a.m.

The crescent MOON is seen in morning July skies through the 3rd and again after Full Moon on the 21st through the end of the month.  The Moon lies near MARS on the morning of July 29th, when both rise at about 12:30a.m.

Morning Planet: MARS.
Mars begins July in AQUARIUS, moves into PISCES on July 7th, moves into CETUS on July 20th, and moves back into Pisces on the 30th.  The Red Planet is now quite bright and easy to observe.  Its path among the stars carries it farther North in the sky and much higher above the horizon during July. By month end, Mars will be as bright as Vega and will continues to brighten throughout the summer.

Mars rises about 12:35a.m. on July 1st and more than an hour earlier (about 11:30p.m.) on the 31st.

As the Earth continues to gain on Mars as they orbit the Sun, Mars also gradually appears larger in size when viewed in a telescope.  It will be closest to the Earth (and largest and brightest) in late October.

What Else to See? The Summer Milky Way is very well seen after midnight, as it reaches high overhead.  Since it is also cooler in the wee hours, morning observers are most fortunate in July. Those with binoculars or a small telescope can pick out many star clusters, star clouds and gas clouds (nebulae) by sweeping along the arc of the Milky Way from Cassiopeia in the Northeast to Sagittarius in the Southwest.

The Moon will either occult or approach very close to several stars of 6th magnitude or brighter during July mornings.  Specific times for these events are given here.

Good Luck Observing!