Tag Archives: astronomy

January 2012 Sky Watching

Taurus the Bull is visible high in southern skies during January

January opens with a sky full of stars and planets in the evening sky.  Taurus the Bull appears high in the southern skies during January’s evening hours.  Two bright star clusters, known as the Hyades and the Pleiades, help construct the constellation.  The “V” shaped cluster forms the bull’s head and face, although the bright reddish star Aldebaran that forms the bull’s eye is not part of the cluster.  Aldebaran is one of the largest stars in our part of the galaxy.  If placed in our solar system, it would extend beyond the orbit of Mars.  The Pleiades ride on the bull’s back.  The Taurus region of the sky is best explored with the low power of binoculars.  The stars in the clusters are so widely spread that they are best viewed with at low power.

Moon Phases

First Quarter:          January 1 & January 31
Full Moon:                January 9
Last Quarter:           January 16
New Moon                January 23

Our planet, Earth, reaches perihelion — its closest point to the sun — on January 4 at 6 p.m. CST.  At this time we are 91,401,967 miles from the sun. 
Along with the bright stars, Venus and Jupiter shine brightly in the clear January skies. 
Venus can be seen low in the western sky throughout the month.  As the planet slowly catches up to our planet, Earth, in its orbit, it rises higher in the sky and gets brighter each evening.  The moon is nearby on January 25 and 26.  Only two other objects are regularly brighter than Venus:  the sun and the moon.  It can be easily mistaken for the bright lights on an airplane.
The moon passes Jupiter early in January 2012.The moon makes a return pass by Jupiter later in the month.
The moon passes Jupiter a second time in late January 2012.
Jupiter shines brightly, although not at bright as Venus, from the southern skies during the early evening.  Venus shines about 4 times brighter than Jupiter.  The moon passes Jupiter twice this month as the charts above show, first early in the month (January 2) and then again on January 29 and 30.
Morning Sky

Mercury opens 2012 low in the southeastern sky before dawn.  The planet is difficult to locate without a good horizon and binoculars.  Antares and Sabik are nearby.  Mercury disappears into the bright sun’s glare during the second week of the month and is invisible until it appears in the evening sky in late February.

Mars rises in the eastern sky around midnight this month, appearing near Denebola — Leo’s tail.  On January 13, its identification is easier when the moon is nearby.

A few days later, the moon is near Saturn.  At 5:30 a.m. on January 16, the moon appears near the planet and Spica.

On the morning of January 19, the moon makes a nice configuration with Antares and the stars of Scorpius around 5:30 a.m.

The chart above shows the positions of the visible planets at mid January 2012.  Mercury is headed for superior conjunction (behind the sun) and Mars for opposition (Earth is between Mars and the sun.)  Saturn and Jupiter are nearly on opposite sides of the their planetary orbits from each other.

Skywatching, December 2011

Image Credit

The Sun reaches its southern-most point in its yearly travels at 11:30 p.m. CST on December 21, signalling the beginning of winter in the northern hemisphere and the beginning of summer for southern latitudes.  This is the Winter (December) Solstice.

The Moon  is in total lunar eclipse on December 10, but the best parts of the eclipse are not visible from the Chicago area.  The eclipse begins at 5:33 a.m. CST, when the moon enters Earth’s penumbra.  The lunar darkening is largely unnoticed by most observers.  At 6:45 a.m. CST, the moon enters the darker shadow where the partial eclipse begins.  The moon is very low in the western sky, setting only 25 minutes later.  The sky is brightening as the moon sets with sunrise.  Farther west in the U.S. more of the eclipse is visible, although the full eclipse is visible from the Pacific, Australia and Asia.

A lunar eclipse occurs when the moon crosses into the earth’s shadow.  The moon’s orbit is tilted slightly compared to the earth’s orbit.  The moon does not cross into the shadow each month.  The next total lunar eclipse visible from the Chicago region is April 15, 2014.  Parts of a partial lunar eclispse are visible  June 4, 2012.

Moon Phases

First Quarter — 12/2
Full Moon — 12/10
Last Quarter — 12/18
New Moon — 12/24


Mercury moves rapidly past Earth (inferior conjunction) on December 4 and into the morning sky.  During the last half of the month it makes an appearance low in the eastern sky somewhat near the star Antares.  The chart above shows Mercury, the moon, and Antares at 6:30 a.m. on December 22.  Find a place with a clear view of the horizon to see the widely spaced trio.  Binoculars will help locate Mercury and Antares.

Venus is the bright “star” in the southwest, just after sunset.  Its brilliance can be easily confused for an airplane.  Late in the month, the moon appears near Venus as displayed on the chart above.

Mars is a reddish “star” that rises around 10:30 p.m. during this month.  It is near the stars of Leo (Denebola and Regulus).  On December 16 and 17, the moon is nearby and is identified on the chart above in the southern skies at 5 a.m.

As the sky darkens each evening with Venus in the west, bright Jupiter is in the eastern sky.  Jupiter rises during the daytime and is high in the southeast by 8 p.m.  The chart above shows Jupiter and the moon for December 5 and 6.  Jupiter appears to move westward as  our planet rotates, setting in the western sky around 3 a.m.

Saturn rises during the predawn hours and is visible low in the southeast around 5 a.m.  It is near the star Spica.  The constellation Corvus is nearby.  One December 19 and 20, the moon helps with the identification of Saturn and Spica.

Viewing the morning sky, three planets (Mercury, Saturn, and Mars) line up across the sky in late December.  At 6:40 a.m., Mercury is low in the east, Saturn is in the south, and Mars is higher in the southwest.  The chart above shows the three planets at this time.

Viewing the solar system from above, the trio described above are on the same side of the sun as Earth, appearing in the morning sky.  Venus and Jupiter are in the other side appearing in the evening sky.

As the daylight continues to shrink, the bright winter sky appears earlier and stays longer, giving observers an opportunity for some skywatching.

November Sky Watching

The immense Andromeda galaxy, also known as Messier 31 or simply M31, is captured in full in this new image from NASA’s Wide-field Infrared Survey Explorer, or WISE. The mosaic covers an area equivalent to more than 100 full moons, or five degrees across the sky. WISE used all four of its infrared detectors to capture this picture (3.4- and 4.6-micron light is colored blue; 12-micron light is green; and 22-micron light is red). Blue highlights mature stars, while yellow and red show dust heated by newborn, massive stars.  More details.

NASA Photo

November evening skies are a transition between the bright stars that dominate summer and winter skies.  Our summer view of the Milky Way is shifted towards the west and the winter section appears in the eastern sky later in the night.  This permits views of celestial wonders beyond the bounds of our home galaxy.  The magnificent Andromeda Galaxy,also known as M31, is nearly overhead throughout the month.  Binoculars will reveal a fuzzy patch of light.  The photo above shows a satellite view of the galaxy revealing stars of varying ages.

Moon Phases

First Quarter November 2
Full November 10
Last Quarter November 18
New November 25

As for the planets visible this month from the Chicago area and across the globe at northern mid-latitudes,  Mercury and Venus are low in the southwest during evening twilight.  The accompanying video shows their positions each evening for the month.  The video repeats twice.  To locate this pair, find a location with a clear horizon.  With binoculars locate them in the southwest sky.  Mercury moves very quickly.  It is visible near Venus for most of the month then disappears into the sun’s glare.

 At month’s end Venus appears near a crescent moon on November 26.

Daylight Saving Time ends 2 a.m. Central Time for the time zone on November 6.  During the month we lose another hour of daylight as the sun appears farther to the south.

A solar eclipse occurs on November 25, but it is visible from the southern hemisphere (South Africa, Antarctica, Tasmania, and New Zealand).

Mars is a morning planet that is visible high in the southeast before sunrise.

Early in the month, Mars appears to pass Regulus.  Watch Mars’ rapid eastward motion compared to Regulus by looking each clear morning.  They appear closest on the morning of November 10.

 About a week later, the moon appears near Mars and Regulus.  In the diagrams above, notice how far Mars has moved past Regulus, since their closest appearance.

Jupiter appears in the east at sunset.  It is brighter than all celestial objects in its vicinity, except when the moon appears nearby on the evenings of November 8 and 9.  The planet is in the south around midnight and in the west during morning twilight.

Saturn rises in the east before sunrise, appearing near Spica.  The moon is nearby on November 22.

The planets’ positions in their orbits are shown for mid-November 2011.

Share your observations in the comments section.

Moon and Planets, October 2011

Look for the Big Dipper low in the northwest sky during early evenings in early autumn

As the weather changes into the cooler evenings of autumn, the stars slowly transition toward the bright winter stars.  One familiar group, known as the Big Dipper in North America, lies low in the northwestern sky during the early evening hours of October.  More, formally known as the Great Bear (Ursa Major), the stars can be found in the northern sky throughout the year.  In autumn they start the evening low in the northern sky; they are likely blocked by the trees or the neighbor’s house.

An interesting pair of stars, Mizar and Alcor, is at the bend of the dipper’s handle.  Mizar is the brighter star with dimmer Alcor nearby.  If you cannot see the close pair, use binocular.  While not physically connected in a binary star system, their close proximity makes them appear together.  Mizar is about 100 light years away with Alcor perhaps another light year away from its brighter neighbor.

Moon Phases

First Quarter   3
Full 11
Last Quarter 19



The positions of the visible planets on October 15, 2011

 This chart shows the positions for the visible planets as seen from north of the solar system.  Notice that Earth is between Jupiter and the sun.  Venus, Mercury, and Saturn appear near the sun.  Earth is slowly moving up to catch Mars.

Look in the west for Venus, Mercury and the moon just after sunset on October 28.

Always difficult to locate, Mercury appears near Venus in late October.  As the sky darkens on October 28, look for the moon and the reddish star Antares.  Look farther to the right of the moon for bright Venus and below it for Mercury.  You’ll need a good horizon.  Binoculars will help locate Mercury.

Venus is slowly emerging from behind the sun.  Early in October, Venus sets about 50 minutes after the sun.  Venus sets later than the sun throughout the month, ending the month setting about 90 minutes behind the sun.  The chart from last month’s night sky description shows the difference of times between sunset and Venus set.
The moon, Mars, and Regulus appear in the morning sky late in the month.

Mars is a morning star rising after 1 a.m. throughout the month.  Early in the month, it appears near the Beehive Cluster.  (See the separate article about this event.)  The moon serves as a good guide to Mars on October 21 and 22 as displayed in the chart above.  The star Regulus serves as a marker of the sun’s annual path and the plane of the solar system.  Look for Mars each morning and note how its orbital motion is carrying it closer to Regulus.  Of course, the two are not close;  Regulus is much farther away than Mars.  Mars will appear to pass Regulus next month.

Jupiter and the moon appear near each other at mid-month.
 Jupiter is the “bright star” in the eastern sky during the early evening hours.  Jupiter is at opposition and closest to Earth on October 29.  At this time the sun and Jupiter are on opposite sides of our planet.  Jupiter will rise in the east at sunset, be south around midnight and set in the west around sunrise.  It’ll be in the sky all night.  On October 12 and 13, the moon makes a nice grouping with Jupiter and the star Hamal.
Saturn appears near Spica at month’s end in the east before sunrise.
 Saturn is not visible for most of the month.  It is at conjunction on October 13.  At this time, the sun is directly between Saturn and our planet, so that Saturn is in the sky during the daytime.  Look at the planet orbit diagram above to see Saturn’s location compared to our planet.  By the end of the month, Saturn rises into the eastern sky, just before sunrise.  On Halloween, Saturn appears near Spica.  As for most observations that occur during twilight, use binoculars to see the pair.
Please share your observations in the comments section or ask any questions that can be answered in future articles.

Mars Passes the Beehive Star Cluster

The Beehive star cluster frequently hosts visits from passing planets.

Image Credit

 On the mornings of September 30 through October 2, Mars appears to move past the Beehive star cluster in Cancer.   The fainter constellation occupies the region between the Gemini twins (Castor and Pollux) and Leo, with its bright star Regulus.  At 4:30 a.m. on these mornings look east.  Regulus is near the eastern horizon with the Gemini twins high in the sky.  Mars appears between in a part of the sky with few bright stars.  Mars is distinctly reddish.  Because of its distance from Earth, Mars looks like a brighter star.  It will be the brightest object between Leo and Gemini.
To get a sense of the stars in that part of the sky, the moon passes through this region the week before Mars passes the star cluster.  See the September 2011 summary.
Away from city lights, a smudge of light appears near Mars.  This is the star cluster.
Catalogued as M44 and NGC 2632, the Beehive star cluster can be seen as individual stars through binoculars.  The optics will also reveal Mars’ color.  The cluster is about 500 light years away and it has at least 300 stars.
In Robert Burnham’s Celestial Handbook he writes that the star cluster was used in ancient times as a weather indicator.  Aratus and Pliny have both stated that the invisibility of the [star cluster] in an otherwise clear sky was considered to forecast the approach of a violent storm (p 345).
This chart shows the positions of Mars compared to the Beehive star clusters on the mornings of September 30 – October 2, 2011.
The star cluster is part of Cancer, forming the starry backdrop for the motion of the objects in the solar system.  Since it’s difficult to perceive distances, the planets appear to move through or among the stars, but the stars and planets are very far apart.  About every year or so a bright planet appears near the cluster.  A year from now, Venus appears near the cluster, followed by a return visit in 2013.  Mercury visits August 2013, followed by a return visit by Mars in early September.
The chart above shows Mars and the star cluster as they would be seen through binoculars on September 30 – October 2, 2011.  On October 1, Mars appears hidden among the stars of the cluster, a spectacular sight.

Sky Watching — September 2011

Look high in south for the Summer Triangle during evenings in September

The bright stars of the Summer Triangle shine from high in the southern skies during the evenings in September.  Three bright stars — Vega, Deneb, and Altair —  that are actually part of the their own constellations, mark the “corners” of the triangle.  Deneb is one of the brightest stars in the sky.  Shining with the brightness of 170,000 suns, this star is 2,500 light years away.  The combination of actual brightness and distance makes it the 19th brightest star seen in the sky at night.  Compared to its neighbor, Vega appears as the 5th brightest star, although it is only 60 times brighter than our sun and 25 light years distant.  The third star, Altair, ranks as the 12 brightest star with an actual brightness of about 11 suns with a distance of 17 light years.  The brightness that a star appears in our sky is related to the star’s actual brightness and distance.

Deneb is part of the constellation Cygnus, the swan.  It represents its tail.  The head of the swan is marked by Albireo.  Look at this star through a small telescope.  It will reveal a wonderful double star, one golden, one blue.

Albireo, as seen through a small telescope, is two stars. One is gold, the other blue.

Image Credit

Moon Phases September 2011
New 27
First Quarter 4
Full 12
Last Quarter 20
The moon appears near Delta Scorpii in early September.

On September 3, the moon appears near the bright star Delta Scorpii as seen from mid-latitudes.  The moon can been seen covering the star from the southeastern US.  This link provides more details.  For others, the moon appears very close to the star with the bright star Antares nearby.

The Autumnal Equinox occurs at 4:05 a.m. CDT on September 23.  At this time, the sun is directly above the earth’s equator.  On this date at noon the sun will go directly overhead for people living at the equator.  For residents of mid-latitudes, the sun will about halfway up in the south at noon, rising at the east direction point and setting at the west cardinal direction.  The equinox also brings equal daylight and darkness at 12 hours each.  From this date until the Vernal Equinox in March, the length of nighttime is longer than daylight hours.

Mercury and Regulus can been seen in the morning sky during early September.

Mercury is usually difficult to see as it rapidly shuttles from morning sky to evening sky.  During early September, Mercury makes a brief appearance in the morning sky.  The chart above shows Mercury and Regulus, the bright star in Leo, at 6 a.m. on September 9.  Locate an observing spot with a clear horizon.  Looking with binoculars locate Mercury and Regulus in a close pairing.

This chart shows the evening appearance of Venus for 2011-2012. The chart shows the difference between the time the sun sets and Venus sets.

Venus begins its evening appearance late in the month.  Venus passed behind the sun in mid-August.  Venus and Earth are like two cars on a race track; Earth is in an outside lane and Venus an inside lane.  Along with a shorter course, Venus moves faster than Earth.  In September, Venus is nearly on the other side of the track and the infield spectators (the sun) are blocking our view of the planet.  It will move faster and catch up to our planet and move between us in the sun (inferior conjunction) in June 2012.

As the chart above indicates, the sunset time between Venus and sun will be between about 30 minutes and 45 minutes throughout September.  Sharp observers may note it very close to the horizon in the west after sunset.  Binoculars will be helpful.  As Venus begins to catch up to Earth, it will appear longer and longer  in the western evening sky, outshining all other objects in the night sky besides the moon.  It can be easily mistaken for lights on an airplane.

As Venus closes in on Earth, it will grow brighter until April 30.  The greatest separation (marked greatest elongation on the diagram) between Venus and the sun is March 27, 2012, with Venus setting nearly 7 hours after the sun.  It’ll be a spectacular sight in the spring night sky, when the tilt of the solar system provides marvelous views of the inner solar system.  Venus will make interesting viewing as it passes bright stars and other planets during its evening appearance.  We will note them here in future postings.

Mars and the moon, September 2011

Mars is visible in the eastern, predawn sky.  Late in the month, the moon appears near Mars.  The chart above shows Mars with the moon and bright distant stars (Pollux, Castor, and Procyon) on September 22 and 23.  During September, Mars shines nearly equal to the bright stars in its background.  While distinctly reddish-orange, the moon helps identify it late in the month.

Look for Jupiter and the moon in mid-September.

Jupiter shines brightly from the eastern sky during late evenings as it rises  in the east around 10 p.m. early in the month.  It is in the sky until sunrise and it dominates the southern sky just before sunrise.  Late in the month, it rises in the east around 9 p.m.  The chart above shows the moon and Jupiter on September 15 and September 16.  The bright star Hamal is nearby.

Saturn disappears into the sun’s bright sunlight as it moves behind the sun in October.

We’d appreciate reading what you are observing.  Please post any interesting observations in the comments section.

Sky Watching — August 2011

A Perseid Meteor

The player above is for the Abrams Planetarium Podcast for August 2011

August is Perseid Meteor Shower time.  Each year during the summer months (mid-July through late August), the earth crosses the track of Comet Swift-Tuttle.  The path is full of dusty debris that has been scattered along the comet’s orbit.  These fine particles are orbiting the sun and they hit our atmosphere.  The meteor events occur when the particles enter the atmosphere and they vaporize.  We see a quick flashes of light — meteors, shooting stars.   Perseid meteors can been seen anywhere in the sky, but they seem to emerge from the constellation Perseus and are named for that radiant point.  Perseids are best observed after midnight when the radiant constellation rises high in the northeastern sky.  On the peak morning, August 13 this year, about 60 meteors per hour are visible.  This year, the moon is full and in the sky when the shower peaks.  Only the brightest meteors are visible.  On August 11, the moon sets around 3:30 a.m. and at 4:30 a.m. on the next morning.  On these two mornings, a large number of Perseids can be seen before twilight begins.
In the photo above, the single Perseid meteor streaks across the field of view during a long time exposure as the stars appear as parallel arcs.

Moon Phases









Mercury and the Moon
Mercury can be seen with a waning cresecent moon on August 27, 2011.

Let’s start this month’s sky watching with an “extra for experts.”   Mercury is an elusive planet and usually very difficult to see.  It is best seen during either autumn mornings or spring evenings when the plane of the solar system makes a very favorable angle with the horizon.  Mercury is visible late in the month about 30-45 minutes before sunrise.  With binoculars and with a good view of the natural horizon, look for it low in the eastern sky.  A thin crescent moon is nearby about 30 minutes before sunrise on August 27.

Venus is not visible during August.  It is at superior conjunction on August 16; that is, it is behind the sun and lost in the bright sunlight of daytime.

The moon and Mars in the morning sky
Look for Mars in the predawn skies among the stars of Gemini. Late in August, the moon appears nearby.

Mars is a morning star in front of the stars of Gemini, starting to rise early enough to be seen in a dark sky in the east.  While visible throughout the month in the predawn eastern sky, it rises around 3:30 a.m. at mid-month, later earlier in the month.  On the morning of August 25, the moon is nearby as shown in the chart above.  Castor and Pollux, the Gemini Twins, are nearby throughout the month.

The moon appears near Jupiter on August 20, 2011.

Jupiter shines brightly in the predawn sky throughout the month.  It easily outshines the other stars in that region of the sky.  On the morning of August 20, the moon appears near Jupiter and Hamal, the brightest star in Aries.

Skywatching August 3, 2011
Look for the Moon and Saturn on August 3, 2011 after sunset.

Saturn shines from the western sky throughout August.  The moon passes near Saturn early in the month as shown in the diagram above.  The bright star Spica is nearby.

This chart shows the positions of the visible planets on August 15, 2011.

The chart above shows the planets on August 15, 2011.

The moon passes Antares on August 7, 2011 in the evening sky

In early August the moon passes in front of the stars of Scorpius during the early evening hours.  One bright star, Antares, makes a nice pairing with our lunar neighbor on the evening of August 7th.  The stars do not have vivid colors, although Antares shines in a ruddy color.  The star’s name is sometimes translated as the “Rival of Mars.”  Ares is the Greek version of the god of war (Mars).

Antares is quite unusual.  Its distance is measured at about 600 light years.  A star like our sun is not visible at that distance without the assistance of a telescope.  Antares is known as a red supergiant.  In the final stages of its life cycle, it shines at the brightness of 65,000 suns.  It is enormous with a volume that, if empty, would hold over 500 million stars the size of our sun.  Placed in our solar system, its volume would extend into the vicinity of Jupiter, some 480 million miles from the center of our solar system.

Video Credit

Antares lies to on the west side of the Milky Way, the greatest density of stars, that outlines the plane of the galaxy by the same name.  The Milky Way stretches high in the eastern sky and then  into the north.  As August evenings progress, the great mass of stars rises higher in the sky.  The faint Milky Way glow can be seen during times when the moon is dimmer, such as before First Quarter and after Last Quarter, and in the countryside that is free from the glow of bright streetlights.  The time-lapse video above shows the Milky Way rising.  In the movie look carefully for Antares as it rises and it is low in the sky to the west (right) of the Milky Way.  The movie is made in the spring when Antares and the Milky Way rise later in the night.

Take a look at the sky events and tell us what you are observing on the comments section of this posting.

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!