Observing the Sky in July 2011

 NASA Photo
This month:
There is a partial solar eclipse visible only from the ocean south-east of Africa. It is not visible from anywhere in North America.

Moon Phases

New 7/1 & 7/30
First Quarter 7/8
Full 7/15
Last 7/23

July has two new moons.  As infrequent as two full moons in a month, popularly known as a “blue moon,” the two-new-moon month has no official astronomical name.  The “blue moon” designation has no official astronomical name, but somewhat goes along with the “once in a blue moon” phrase.  Additionally, sometimes after volcanic eruptions, ash in the atmosphere gives the moon a bluish cast.  Since these eruptions are infrequent, the blue moon color effect related to these events is also very infrequent.  The second new moon in a month is sometimes called a “black moon” in some circles — though again this event has no official name.


Look for the Moon and elusive Mercury after sunset early in the month. This diagram and other B&W Diagrams from Sky Calendar. Used with permission.

 Early in the month, Mercury appears in the western sky during evening twilight.  This planet is difficult to see and it never appears in a dark sky.  As with the clustering of the planets in the morning sky in May, use binoculars to view the planet.  At around 9 p.m. in the Chicago area, locate a viewing spot with a good western horizon.  On Saturday, the moon appears to the lower left of Mercury appearing the West-NorthWest sky.   On Sunday, July 3, the moon appears at about the same altitude as Mercury but farther to the left.
Support the Sky Calendar:  Get a monthly calendar depicting daily astronomical events.  Subscribe to the Sky Calendar at any time for $11 per year at Sky Calendar, Abrams Planetarium, Michigan State University, East Lansing, Michigan 48824.
 As the moon approaches First Quarter, it appears near the star Spica and the planet Saturn.  Distinctly yellow, Saturn’s rings can be seen through a small telescope.  Close inspection will reveal shadows of the rings on the planet’s cloud tops and Saturn’s largest moon, Titan, in the same plane of the rings.   The chart above shows the waxing moon, Spica, and Saturn on July 7.
July 12, Happy Birthday Neptune!  The Royal Astronomical Society of Canada has declared this date as the anniversary of the discovery of Neptune based on Neptune’s orbit.  The planet was first observed on the night of September 23/24, 1846.  The planet takes nearly 165 earth-years to orbit the sun.  On July 12, the planet completes one solar orbit, and one Neptunian year since its first observation from Earth; that’s 6+ human generations!  So let’s go with RASC’s declaration!  Happy Discovery, Neptune! 
July 20, a special date1969 — Apollo 11 moon landing.  1976 — Viking 1 martian landing.

On July 24, the moon appears near Jupiter during early morning hours.

As the moon moves past its full phase and into its waxing phases, it passes Jupiter on  the mornings of July 23 and July 24.  Look for the moon near the Pleiades on the Morning of July 25.
 As the moon moves toward the new phase, it appears near Mars on the predawn hours of July 27.  A thin crescent moon appears to the upper right of a distinctly red-orange Mars.
Report here on what you are seeing in the sky in our comments section.  The section is there for questions so that we can include answers in future postings.
Happy Viewing!

Moon and Planets, May 2011

Moon Phases

NASA Photo

A clustering of planets in early morning twilight. From Abrams Planetarium Sky Calendar All similar diagrams (c) Abrams Planetarium,  2011. Used with Permission. Key for these diagrams: Me, Mercury; Ve, Venus; Ma, Mars; Ju, Jupiter. 

The charts above show the planets on May 1 and May 2 at around 5:20 a.m. CDT in Chicago.  On May 1, a thin crescent moon appears to the left of Venus.  With binoculars or telescope locate Mars and Jupiter beneath it.  The next morning, the moon is much lower, although the planets are visible again low in the eastern sky. This clustering of the planets is from a seemingly complex motion of the four planets and Earth.

Mercury is the fastest planet, revolving around the sun in 88 days, although it catches up to Earth and passes our planet every 115 days.  That’s three times every year.

Venus revolves through its solar orbit every 224 days, but it takes 584 days (1 year, 7 months) to catch our moving planet.

Mars revolves around the sun slower than Earth, taking 1 year, 292 days for one solar revolution.  Our planet catches Mars every 2 years, 51 days.

The fourth planet moves slowest.  At its distance from the sun, Jupiter takes nearly 12 years to revolve around the sun and our faster moving planet catches up to and passes Jupiter in one year, one month intervals.

On April 9 Mercury passed between the earth and the sun and emerged into the morning sky. It climbed higher into the morning sky.  On May 7, it reaches its greatest separation (elongation) from the sun as seen by Earth.

Venus has been in the morning sky for several months and it is slowly disappearing in the sun’s glare as to moves behind the sun on August 16.  As the days and weeks, pass Venus appears lower in the sky until it disappears in the sun’s brilliant glare.

Mars appears to be emerging from behind the sun as our planet’s faster motion carries us around the sun faster.  The combination of speeds makes Mars appear to move more slowly than we might think.  This Red Planet moves at about half the speed of our planet so Mars appears to slowly move across the sky as compared to the other planets.  Mars was directly behind the sun on February 4 and has slowly emerged from the sun’s glare since then.

While Jupiter revolves more slowly than Mars, our planet catches it sooner than it catches Mars.  Its annual progression across our night sky is very similar to the stars.  After conjunction, it appears in the morning sky, rising earlier each week.  After several weeks, it rises around midnight.  Then it rises around sunset as Earth passes between Jupiter and the sun.  From that point it rises sooner each day.  Before you know it, it appears in west just after sunset, shortly thereafter disappearing in the sun’s brilliant glare only to repeat the cycle. However, there is one small difference, Jupiter’s slight orbital motion carries it slightly eastward as compared to the stars during this sequence.  So that in nearly 12 years, Jupiter has moved eastward on full circle in front of the stars behind the plane of the solar system, commonly known as the zodiac. As Mercury and Venus disappear into the sun’s glare after this display, Jupiter will rise rapidly in the morning sky when weekly observations are made.  In comparison, Mars will not appear to move much as its orbital motion is only half our planet’s speed.   For example, compare Jupiter’s position near the horizon in the May 1 diagram above and then again in the May 22 diagram below.

The chart below shows the relative position of the five planets and the sun on May 15, 2011, as viewed from north of the solar system.  From Earth, all the planets appear nearly in a line.  They are not easily observed because the line is near the brilliant sun.

The planets’ relative positions, May 8-11, 2011.

As the month progresses,  Jupiter appears higher in the sky, Mercury and Venus appear lower, and Mars appears nearly in the same place.

The bright planet grouping, May 22, 2011


While all the planet clustering occurs in the morning sky,  the moon appears near Saturn on the evenings of May 12-14.

With the changing weather patterns and increased daylight, May 2011 brings an interesting clustering of planets in the bright predawn skies.  Use binoculars or a telescope; be patient; and watch the changing display of planets.


A note about the Abrams Planetarium Sky Calendar.  The publication is an excellent way to learn about the sky.  Written by expert sky watcher, Robert C. Victor, with an accompanying monthly sky map by D. David Batch, the Sky Calendar is written in calendar form that shows notable sky events that interested sky watchers can find.  Victor uses the moon to help locate bright stars and planets.  The calendar is published as a quarterly set, but subscriptions can start any time.  Send $11 to Sky Calendar, Abrams Planetarium, Michigan State University, East Lansing, Michigan 48824.

For purposes of full disclosure, this writer studied planetarium and astronomy education at Abrams Planetarium, and received a master’s degree in the subject from Michigan State University.   At the time, we graduate students were informally called “Abrams Interns.”  Graduates have served at planetariums and astronomy education organizations across the world.  Victor, Batch and other Abrams staff schooled us in how to connect with the public on observational astronomy.  If we former Interns were in another field, we would be praising our Abrams mentors in our resumes and our bios.  It was an honor to study with them and to see what they continue to do with constant commitment and devotion to their field of communicating astronomy to the public.

I received no compensation for this endorsement.  TheSky Calendar is a worthy publication that needs our support.  Subscribe today!

Moon and Planets, April 2011

Look southeast in mid-April for the Moon, Saturn and Spica

Podcast above is from Abrams Planetarium.

April 2011 brings more daylight hours.  On April 1st, the sun is in the sky for about 12 hours, 45 minutes in the northern part of the United States.  By April 30, the daylight hours increase to 14 hours.

Saturn is the only bright planet that shines throughout the night this month.  The yellowish ringed planet rises in the eastern sky around sunset, is in the southern sky at midnight, and sets in the western sky near sunrise.    On April 2, Saturn is at oppostion; that is, it is opposite the sun in the sky.  At this time, our planet is directly betwen the sun and Saturn.  Saturn takes nearly 30 years to revolve around the sun, but because of its slower speed, Earth catches up to and passes Saturn every 378 days (1 year, 13 days).  In 2012, Saturn’s opposition is April 15.

On April 16, the moon appears near Saturn and Spica.  Use the moon as a guide at mid-month to locate those objects.  Saturn is distinctly yellow and the star Spica is blue in color.  The chart above shows the moon, Saturn and Spica on April 16 at 9 p.m.

In contrast, Venus and Mercury are never seen at midnight from the skies of Earth.  Both planets are between the earth and sun.  Because of this geometry, the two planets are seen near sun, either in the west after sunset or in the east before sunrise.  With Mercury being closer to the sun, it is rarely seen in a dark sky.  Unless the moon, bright planet or bright star is the vicinity, Mercury goes unnoticed.  In contrast, Venus is farther from the sun and can appear high in the east before sunrise or in the west after sunset.  Because of its brilliance, Venus has been called the “Morning Star” or “Evening Star.”  Generically, any bright planet can be given those names.

Mercury was visible in March in the evening sky.  By early April, its rapid revolution carries it between the sun and Earth (inferior conjunction) and into the morning sky.  During the past several weeks, brilliant Venus has moved farther from Earth, appearing low in the eastern predawn sky.  The manner in which we view the solar system during spring mornings places the planets low in the sky. 

Similarly, Jupiter was visible in the western sky at sunset during March.  From our view on Earth, Jupiter passes behind the sun (conjunction) early in April and moves into the morning sky.  Jupiter moves at about twice the speed of Saturn around the sun, yet Earth catches up and passes Jupiter every year and 34 days.  In contrast, Mars moves about half the speed of Earth and our planet catches it every 2 years, 50 days.

Look for a planetary grouping at the end of April, 2011.

In late April 2011, four planets are clustered near the horizon.  This occurs in bright twilight, so a binocular or telescope is necessary to locate these objects.  As shown in the diagram above on April 30 at 5:30 a.m., a crescent moon appears above bright Venus.  Dimmer Mercury appears to the lower left of Venus.  Both Mars and Jupiter appear just above the horizon.

As the calendar turns into May, Jupiter, Mars and Venus will make additional interesting planetary groups.  Be sure to check back in early May 2011 for that month’s update.

Moon and Planets, March 2011

Moon and Planets
Look in the west for Jupiter, Mercury and the moon in the evenings during early March.


The podcast player shown above for the month of March 2011 is from Abrams Planetarium.

March is a month of rapid change.  Weather shuffles from the depths of winter into the promises of May.  This year the Moon and planets provide interesting views during the early evening and early morning.

Early in the month, Jupiter, Mercury, and the moon appear in the western sky after sunset.  The moon will appear as a very thin crescent.  As the diagram above shows, the moon,  just 46 hours past its new phase, and Jupiter make an interesting display during twilight on March 6 with elusive Mercury much lower and near the horizon.  Houses, trees and other terrestrial features will block a view of Mercury.  Binoculars will help locate it from a spot with a clear horizon.  The accompanying chart shows the trio at 6:15 p.m.

Mercury is difficult to view, although twice each year in our planet’s celestial orbit, we can get an optimal view of the planet.  During spring evenings and autumn mornings, we have an excellent view of the solar system objects that are near the sun.  Because of Mercury’s solar proximity, it always sets before the sky completely darkens.  During spring and autumn the solar system is oriented so that Mercury sets later than average or rises sooner than its average time, making it best viewed if it is appropriately placed in its orbit.

Look for Jupiter and Mercury during mid-March.

 As the days of March step forward, watch Mercury climb higher in the sky each evening at 6:15 p.m.  (Remember that Daylight Saving Time begins March 13.  Beginning on that date the times will advance one hour.)  By March 15, Jupiter and Mercury appear near each other at 7:30 p.m. (See the diagram above.) Mercury will continue to climb higher for another week and then rapidly dim and disappear into the sun’s bright glare by month’s end. 

At the end of March look for Venus and a thin crescent moon just before sunrise.
By the end of March, the moon will appear in the morning sky.  On the last day of the month, a thin waning crescent moon, less than 3 days before it’s new phase, appears near Venus at 6 a.m. in the eastern sky.
March is a fascinating month of change in the weather, the promise of longer, warmer days, and bright configurations of the moon and planets.

February Morning Sky

Venus and Moon
Venus and Moon on February 28, 2011

Venus continues to dominate the early morning sky.  While fading in brightness as it races behind the sun and  into the evening sky later in the year, it is the brightest starlike object in the predawn sky.  Because of its brillance, it can be mistaken for an airplane.  During February it rises around 4 am and can be found low in the east-southeastern sky until the sky brightens toward sunrise.  Clever observers can locate Venus during daylight hours.

Further observations with a small telescope and moderate powers (35x-100x) will reveal that this planet displays phases, similar to the moon’s cycle of phases. 
In late February and early March, the a crescent moon joins Venus in the eastern sky to make an interesting grouping.  The accompanying diagram shows the celestial duo at 5:30 a.m. on February 28.  The next morning, the moon will appear lower and to the left of the moon.

Winter Solstice Lunar Eclipse

(NASA Photo)

A spectacular lunar eclipse is visible across the skies of North America, just hours before the winter solstice, on the night of December 20/21, 2010.

A lunar eclipse is visible when the moon, at the full phase, moves into the Earth’s shadow.  Occurring infrequently because the orbit is tilted slightly compared to the earth’s solar orbital path, the moon usually moves above or below the shadow when on the opposite side of Earth from the sun.

As the moon slowly plunges into the Earth’s shadow, it loses its reflected sunlight.  A total eclipse is not completely dark, but some red and orange sunlight is refracted into the shadow.  The moon then has a reddish orange glow.

Earth’s shadow has two zones:  The penumbra is the outer part of the shadow where the sunlight is not completely blocked.  The umbra is dark because it receives no direct sunlight.  During the nighttime we are inside the earth’s umbra.  No sunlight is visible.

Lunar eclipses are seen more often from any one location as they are visible from over half the earth, where the moon is above the horizon.  A lunar eclipse is not dangerous to view.  Binoculars or a telescope under low power, 15x to 40x present outstanding views of the eclipse.

Here are the events for the evening:

December 20, 2010  (The times that follow are accurate for any location in North American, except times for sunrise, sunset, moonrise, and moonset.  Observers in other time zones can adjust the eclipse times by adding or subtracting their time zone difference from Central Standard Time.)

  • 3:50 p.m. CST (Chicago) — The moon rises in the east-northeast sky.
  • 4:22 p.m. CST — Sunset.  Throughout the evening, the moon rises higher in the eastern sky.
  • 11:30 p.m. CST — The moon begins to move into the penumbra.  Not much darkening is noticed.

December 21, 2010

  • 12:32 a.m. CST — The moon moves into the darker central shadow, the umbra.  The partial phases of the eclipse begins.  As the eclipse progresses, more of the moon grows darker.  The moon appears high in the southern sky during this part of the eclipse.
  • 1:40 a.m. CST — The moon is completely immersed inside the umbral shadow and the best part of the eclipse begins.  For the next 73 minutes, the moon may be illuminated by a soft coppery color, like the image above.  Some sunlight streams through the earth’s atmosphere and is bent into the shadow by the air’s prismatic effects.  The brightness and depth of color will depend on the amount of dust suspended in the Earth’s atmosphere.  Volcanic ash suspended at high altitudes is one factor that can affect the colorful display.
  • 2:53 a.m. CST — The moon begins to exit the umbra and the total phase of the eclipse is finished. 
  • 4:01 a.m. CST — The moon is fully inside the penumbra continuing to exit into bright sunshine.
  • 5:04 a.m. CST — The eclipse is finished.
  • 7:14 a.m. CST — Sunrise
  • 7:31 a.m. CST — Moonset
  • 5:38 p.m. CST — Winter Solstice

The next lunar eclipse visible from North America occurs on June 4, 2012.  The start of the eclipse occurs June 4, 2012, although it completes after moonset.  The next total lunar eclipse visible from the Americas is on the night of April 14/15, 2014.

For more information about lunar eclipses and general sky watching, see the Waubonsie Valley High School Planetarium website.

Exciting Planetary Grouping

August 13, 2010 — Look west at 9 p.m. for the moon and a planetary grouping.

 A summer grouping of bright planets is visible in the western sky during the early evening hours of August 2010.  Venus, Mars and Saturn have sparkled in the evening sky all summer, although separated in the sky.   In early August, they begin to cluster in the western sky.  On the evening of August 13, the moon joins the trio to form a spectacular grouping as shown in the diagram above. 

Here’s what to look for: 

  • Look west at 9 p.m. CDT, in the Chicago area, or about 40 minutes after sunset for other areas.  Locate a place that has a largely unobstructed view of the western horizon.
  • The waxing crescent moon  can be seen south of west near the horizon.  Look carefully, you may notice the night portions of the moon are lit dimly.  This is known as Earthshine.  The same effect occurs on Earth at the time of the full moon.  Sunlight reflects from the moon and lights up the ground on Earth.
  • Brilliant Venus is to the right (north) of the moon.  It’s brightness makes it easy to find.  Only two other objects in the sky are brighter than Venus — Sun and Moon.  While these objects are close in the sky, Venus is about 75 million miles away.
  • Reddish Mars is dimmer than Venus and appears to the upper left of Venus.  On this evening, Mars is approximately 190 million miles from Earth.
  • Yellowish Saturn appears to the upper right of Mars and slightly dimmer.  Of the solar system objects in this grouping, Saturn is most distant at 930 million miles away.
  • The bluish star Spica appears high above the moon, shining from 260 light years away.

Mars and Saturn will again group together in mid-August 2012 in the western evening sky.  In December 2015, the three planets will again appear close together, although they will be widely spaced in the morning sky.  Jupiter will also appear with the wide grouping. 

These planetary groupings are not everyday occurrences, are worth noting, and interesting observing.  Keep looking up!