Tag: moon

2019, October 1-6: Waxing Moon Passes Evening Planets, Jupiter and Saturn

The moon passes the evening planets, Jupiter and Saturn, during early October 2019. (The moon’s size is exaggerated on the diagram.)

The moon returns to the evening sky and passes Jupiter and Saturn early in October 2019.  The following summarizes the evenings, one hour after sunset.  (Check your local sources for the time of sunset for your location.)

  • October 1: One hour after sunset the crescent moon (3.2 days after the New phase, 15% illuminated), 11° up in the west-southwest, is east of a line that connects Zubenelgenubi  and Zubeneschamali (β Lib, m = 2.6), 6.5° to the lower left of Zubeneschamali.  Bright Jupiter is 19° up in the southwest.  Meanwhile, Saturn is about 25° to the upper left of Jupiter.  Saturn is nearly 26° up in the south.
  • October 2: The crescent moon (4.2d, 23%) is about 16° up in the southwest, one hour after sunset. Through a binocular observe the crescent moon. The binocular reveals the gentle glow of Earthshine in the lunar night. At the same time, the lunar crescent is nearly 12° to the lower right of Jupiter.
  • October 3: One hour after sunset, the moon (5.2d, 33%) is 1.9° to the upper left of Jupiter.
  • October 4: One hour after sunset, the moon (6.2d, 43%) is nearly midway between Jupiter and Saturn; the planets are over 25° apart, although the moon is closer to Saturn. The moon – Saturn gap, 10.7°; moon – Jupiter, 14.6°. All three are along the same diagonal line.
  • October 5: Today, the moon reaches its First Quarter phase at 11:47 a.m. CDT Three of the bright planets continue to hide in the sun’s glare. Mars, about a month after its solar conjunction, is 11° west of the sun, rising about one hour before sunrise. The visibility of Mercury and Venus suffers from a poorly inclined ecliptic – plane of the solar system – this time of year. Venus, 14° east of the sun, sets 36 minutes after the sun; Mercury, 21° east of the sun, sets about 5 minutes after Venus. The two bright outer planets, Jupiter and Saturn are in the southern sky after sunset. Saturn, 25° up in the south, is 2.1° to the upper right of the slightly gibbous moon (7.2d, 53%). The planet is west of south cardinal point. Bright Jupiter, 25° to the lower right of Saturn, is nearly 18° up in the south-southwest.
  • October 6: One hour after sunset, the moon (8.2d, 63%), 25° up in the south – east of the meridian, is over 14° to the upper left of Saturn.

Happy observing!


2019, September 24: The Moon and Beehive Cluster

September 24: As the sky begins to brighten in the morning, about 90 minutes before sunrise, look east for the waning cresent moon.  It is 25.0 days old (past the New phase) and 25% illuminated.  Castor and Pollux, the Gemini Twins, are above the moon and Procyon is to the moon’s right.  Regulus is far below the moon.

With a binocular look below the moon for a small smattering of stars.  They look like diamonds on the velvet of the darker sky.  This is the Beehive Cluster.  The cluster is about 500 light years away and it contains about 350 stars, a few dozen of which can been seen with a binocular.

If you have sharp eyesight, look for the cluster without a binocular. To the unaided eye, the cluster resembles a cotton ball.

The cluster is also known as the Praesepe (Manger).  More formally it is known by its catalog numbers M44 or NGC 2632.

Tomorrow morning, September 25, the moon is below the cluster and still above Regulus.  Take a look!

(As an aside, look at the moon through the binocular.  On the night portion, notice that it is slightly illuminated.  This is from sunlight reflecting from the nearly full Earth, as seen from the moon, gently illuminating the night portion of the moon — Earthshine.)

2019, August 12-13: Perseid Meteor Shower Peak Dimmed by Bright Moon

Meteor Shower (NASA Photo)

Annual meteor showers occur when our planet passes through the dusty debris that are spread broadly along a comet’s celestial path.  Each year during mid-August, Earth passes through the track of Comet Swift-Tuttle.  Tiny bits of dusty rock smash into our planet’s atmosphere and are vaporized in a quick streak of light — a meteor or shooting star.  During this time, the meteors can be seen anywhere in the sky, but they seem to emerge from the region of the constellation Perseus in the northeastern sky during the early evening.  As Earth rotates during the night, the point of emergence (radiant) moves higher in the sky.  The best viewing occurs after midnight when the radiant is highest in the sky before morning twilight begins,

It is important to note that the rates that are published in the popular press include dim meteors and those that dazzle our eyes and temporarily leave a streaked glow in the atmosphere.  It is impossible for any one observer to see all the projected meteor counts.  Today many live in cities or larger metropolitan where the glow of bright streetlights wash out the dimmer nighttime stars and dimmer meteors during this shower.

So, for observers in metropolitan areas should half the projected rates (60 meteors per hour).  So we’re down to 30 meteors per hour for most observers in metropolitan areas.  To see the entire sky, the observer needs an all sky camera to catch all the meteors or four friends who look above the cardinal directions while the single observer looks overhead.  So, a lone observer can see 5-6 meteors per hour in a metropolitan area or 10-12 per hour in a dark location. So be patient, especially this year with a bright moon in the sky during the morning.

This year, a gibbous moon adds bright light, so the observable rate is reduced further to perhaps 2-3 in town, 4-6 away from lights.

Here are notes for the mornings of August 11-13 that include some planet observations.  Times are in Central Daylight Time for observers near Chicago Illinois.

  • August 11: The Perseid meteor shower is near its peak. The moon sets a few minutes after 2 a.m. CDT and morning twilight begins about 2 hours later.
  • August 12: Jupiter is now setting before 1 a.m. CDT. For the Perseids, moonset occurs near 3 a.m. CDT and morning twilight begins an hour later. Bright Mercury is 10° up in the east-northeast, 30 minutes before sunrise.
  • August 13: For the peak morning of the Perseids, the moon sets about 15 minutes before morning twilight begins. About 30 minutes before sunrise, Mercury, a little brighter than yesterday morning, is nearly 10° up in the east-northeast.

2019, August 8 – 12: Moon and Evening Planets Jupiter and Saturn

As the moon reenters the evening sky it passes Jupiter and Saturn.  The chart above shows the southern sky about 9 p.m. CDT in the Chicago area, about 1 hour after sunset. (The moon’s size is exaggerated on the chart.)  Here are highlights:

  • August 8:  In the evening, one hour after sunset, the moon (8.0 days past the New phase, 64% illuminated), over 28° up in the south-southwest, is 1.9° to the upper right of Graffias, the second brightest star in Scorpius. At the same time the moon is over 10° to the upper right of Antares. the brightest star in the Scorpion, and nearly 12° to the right of Jupiter.
  • August 9:One hour after sunset, the moon (9.0d, 74%) – 27° up in the south – is 2° to the upper left of Jupiter.  At the same time the moon is nearly 9° to the upper left of Antares.
  • August 10: One hour after sunset, the moon (10.0d, 82%), 25° up in the south, is nearly midway between Jupiter and Saturn. The gaps: Moon – Jupiter, 14°; Moon – Saturn, 16°.  Jupiter is nearly 26° up in the south.  Saturn is nearly 22° up in the south-southeast.
  • August 11: One hour after sunset, the moon (11.0d, 89%) is 22° up in the south-southeast, 3.9° to the right of Saturn.
  • August 12: One hour after sunset, the waxing gibbous moon (12.0d, 95%), 18° up in the southeast, is nearly 9° to the lower left of Saturn.

2019, November 28: A Close Venus – Moon Conjunction

As Venus enters the evening sky and appears with Jupiter and Saturn, the moon passes Venus on the evening of November 28.  The moon appears 1.9° to the upper left of the Venus.

The chart above shows the scene about 45 minutes after sunset, looking southwest.  Locate an observing location free from obstructions, such as trees, houses, and buildings.  Venus is only 7° up in the southwest.

Use a binocular to note the thin crescent and that the night portion is gently illuminated by sunlight reflecting from Earth.  The moon is only 6% illuminated and 2.3 days past its New phase.

Venus is the brightest “star” in that part of the sky.  Jupiter is slightly dimmer and to the lower right of Venus.  Saturn is to the upper left of Venus.

Venus and the moon appear in the viewfinder of a camera with a 300 mm focal length lens.  A longer exposure reveals Earthshine on the moon.

2019, November 24: A Venus-Jupiter Conjunction

2016, August 27: A Venus-Jupiter conjunction.

Southern hemisphere readers, a chart for the conjunction appears at the bottom of this article.

As Venus emerges from the sun’s glare from its superior conjunction, Jupiter is heading toward its solar conjunction in late November 2019.  Venus passes Jupiter in a second conjunction between the two planets during this appearance of Jupiter that started late in 2018.

Venus is brighter in our sky because it is closer to Earth, so it appears larger in the sky than Jupiter.  Clouds cover this nearby planet and they reflect over 75% of the sunlight that hits them.  Farther Jupiter reflects about 50% of the sunlight that reaches its clouds.  The result is that Venus is about 3 times brighter than Jupiter, the two brightest “stars” in the southwest.

Here’s how to see the event

The passing of these two planets is a slow moving show that occurs over several nights.  First, find a clear horizon in the southwest, free from trees, houses, buildings, and other possible obstructions.

In the charts that follow, several of them are displayed for a time interval after sunset.  Use local sources for the time of your sunset.  The U.S. Naval Observatory has an online calculator that displays a year of sunrises and sunsets.  Enter your state and city into Form A on the website. For readers outside the U.S., enter your longitude and latitude in Form B for your yearly table.  Click here.

Start looking for Venus and Jupiter about 30 minutes after sunset. A binocular may help with the initial identification of the two planets.  After that first observation go outside at about the same time each evening.

While low in the sky, Venus is the brightest object in the southwest.  If you live near a busy airport, the planet’s visual intensity rivals lights on airplanes.  Wait for a minute, you’ll see the airplane move through the region. Venus will seem to hang there.  Jupiter is not as bright, the second brightest starlike point of light to Venus’ upper left.  Each evening until November 24, Venus gets closer to Jupiter.

Begin looking in late October when the moon is near Venus.

2019, October 29: The crescent moon appears near Venus. Jupiter is to the upper left of Venus and the moon.

The moon makes its first appearance with Venus on October 29.   Thirty minutes after sunset, the moon appears to the upper left of Venus, only 4° up in the southwest with bright Jupiter to the upper left of the pair. The moon is 1.8 days old, past its New phase, and 4.4% illuminated.  The moon appears with Jupiter two evenings later (October 31).

2019, November 13: The Venus-Jupiter gap is 10°.

On November 13, thirty minutes after sunset, the Venus – Jupiter gap is over 10°. (Your fist, at arm’s length, is about 10 degrees from the knuckle of your thumb to the knuckle of your pinky finger.)  Venus is 6° up in the southwest.  Look for the planets each clear evening during the next several evenings.

2019, November 19: Look low in the southwest for Venus and Jupiter about 45 minutes after sunset.

In about a week, the gap closes between the planets. On November 19 their separation is about 5°.  About 45 minutes after sunset, Venus is 4° up in the southwest.

The Venus continues to close in on Jupiter. The separations until the conjunction:

  • Nov 20, 3.9°;
  • Nov 21, 2.8°;
  • Nov 22, 2.1°;
  • Nov 23, 1.5°, Venus is to the lower left of Jupiter.  The pair is nearly as close as they are tomorrow evening.
2019, November 24: Venus-Jupiter conjunction!

On  the evening of November 24, Venus and Jupiter appear closest! Forty-five minutes after sunset, Venus, nearly 7° up in the southwest, is 1.4° to the lower left of Jupiter.  The separation has the same distance as three times the moon’s apparent size in the sky.  Not the actual size, but the size the moon appears in the sky. The planets appear close together in the sky, but Venus and Jupiter are over 430 million miles apart, over 4 times the earth’s distance from the sun.

Now watch Venus appear to separate and move away from Jupiter.  The separations after conjunction:

  • Nov 25, 2°, Venus is to the left of Jupiter;
  • Nov 26, 2.8°;
  • Nov 27, 3.7°, Venus is to the upper left of Jupiter;
  • Nov 28, 4.7°

Next Venus moves toward a conjunction with Saturn on December 10.

In the Southern Hemisphere

For our southern hemisphere readers:  The chart above shows the Venus-Jupiter conjunction about 45 minutes after sunset as seen from the latitude of Sydney Australia, looking west-southwest.  Venus and Jupiter are 1.4 degrees apart with Saturn to the upper right. At this time Venus is about 20% of the way from the horizon to overhead.  As with northern hemisphere observers, use local sources for the time of sunset.

Venus-Jupiter Conjunctions, 2021-2024

Conjunctions of Venus and Jupiter are frequent, but approximately a year apart beginning with a difficult-to-see conjunction in 2021.  The following table provides explanation of the upcoming meetings.

Date Separation When Description
February 11, 2021 26’ Morning This pairing is very difficult to see in the eastern sky as the planets rise in bright twilight just 25 minutes before sunrise.
April 30, 2022 29’ Morning The planets rise in the eastern sky about 90 minutes before sunrise.  In separation, this rivals the gap of the June 2015 conjunction, although it is lower in the sky.
March 1, 2023 32’ Evening This conjunction rivals the June 2015 pairing, with the planets high in the west after sunset, setting 2 hours, 30 minutes after the sun.
May 23, 2024 15’ Morning This pairing is impossible for casual observers to see as it occurs when the planets are nearly behind the sun hidden in the solar glare.