Tag: Planets

2019, August: Mercury and Heliacal Rising of Sirius

The heliacal rising is the first appearance of a bright star in the morning sky before sunrise.

During August, as Mercury makes a morning appearance, brilliant Sirius, the sky’s brightest star, makes its first morning (heliacal) rising just before sunrise.  For the latitude on the diagram, about 41.7 degrees, this is August 14, 2019.  For locations farther south, this occurs days earlier and later for latitudes farther north.

August 29:  Now appearing in the darker morning sky, Sirius is visible with Betelgeuse and Procyon.

Sirius, the Dog Star, is sometimes called the Nile Star as its heliacal rising historically coincided with the flooding of the Nile River.  The Dog Days of Summer (in the northern hemisphere) occur, coincidentally, during August when Sirius and Procyon, the Little Dog Star, appear in the eastern sky before sunrise.

Update:  August 9, Mercury is low in the northeast.  First located with a binocular then observed without its assistance.

Mercury is at greatest elongation on August 9.  Because Mercury is closer to the sun than Earth, we see Mercury appear in either the morning or evening sky around the time the sun rises or sets.  It appears in the sky earlier each morning or stays there later each night.  It reaches its greatest separation from the sun and then seems to reverse its direction, moving back into sunlight, only to repeat the process a few months later at the other horizon and sky setting.

As Mercury moves back toward the sun in August, it is lower in the sky each morning at about the same time.  Sirius appears higher in the sky each morning at the same time.  And Mercury gets brighter as it appears nearer to the sun.  As Sirius appears higher, it seems to brighten because it gets above the thicker atmosphere that tends to diminish the brightness of celestial objects.  They are not quite the same brightness, but appear at the same altitude around August 19.

To locate the planet and the star, find a clear horizon in the east-northeast and east-southeast.  Start looking for Mercury and Sirius about 30 minutes before sunrise.  A binocular may help in viewing them.  Mercury is low in the east-northeast, about 10 degrees up.  Sirius is very low, in the east-southeast about 3 degrees up when first visible.  Sirius may twinkle wildly this low in the sky.  To be sure you have Sirius, don’t confuse it with Procyon in the east and a little higher.  Orion is higher in the sky and its three belt stars make an imaginary pointer that take us to the area to find Sirius.  Reddish Betelgeuse is higher in the sky,  Sirius, Procyon, and Betelgeuse make nearly an equilateral triangle known as the Winter Triangle.

Sirius’ heliacal rising occurs every year about this time.  This year the event is a little more interesting because a bright planet is in the sky.

Advertisements

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.

2019, July 9: Saturn at Opposition

On July 9, Saturn is at opposition, nearly a month after Jupiter was in the opposite direction in the sky from the sun.

Saturn is near opposition for several nights before and after reaching this point opposite the sun.  To locate the planet step outside after the sky darkens.  The chart above shows the sky about 90 minutes after sunset; check your sources for the time of sunset at your location. (For example, in Chicago, Illinois, the time for the above chart is 10 p.m. CDT.  Near Omaha, Nebraska, 90 minutes after sunset is 10:30 p.m. CDT.)

Jupiter is the bright “star” that is almost south, but less than one-third of the way up in the sky.  Golden-orange Antares is to the lower right of Jupiter.  Saturn is farther left of Jupiter in the southeast, lower in the sky than Jupiter.  Saturn is among the stars of Sagittarius, brighter than those surrounding stars, but not as bright as Jupiter.  For perspective, the moon is outside the chart.  The gibbous moon is in the southwest, above the bluish star Spica.  On July 15, the nearly full moon is to the right of Saturn.

Through a telescope, the planet’s rings are revealed.  If you’re careful, you might see its a few of its moons, depending on the diameter of the lens or the mirror and the magnification that is used.  The large gap in the rings, Cassini’s Division, might be seen as well.

Viewing Saturn through a telescope is one of life’s memorable experiences.  If you view this spectacular ringed wonder through a telescope, you will certainly remember.  A child will remember this experience.

Opposition occurs when Earth passes between a planet farther from the sun than Earth (Mars, Jupiter, Saturn, Uranus, and Neptune) and the sun.  The planet rises at sunset, appears in the south around midnight, and sets in the west.  When at opposition, the outer planets are closest to Earth, at their brightest points in the sky, and provide the best telescopic views.

Saturn appears at opposition again on July 20, 2020, when it reaches that point just six days after Jupiter’s opposition.  Jupiter passes Saturn in December 2020 for a Great Conjunction that occurs about every 20 years.

2019, June 5-30: Mercury and Mars in the Evening Sky

The chart above shows the evening positions of Mercury and Mars from June 5, 2019, to June 30, 2019. The moon is part of the scene on June 5 and June 6.

About 45 minutes after sunset, Mercury and Mars are visible in the west-northwest  beneath Pollux and Castor, the Gemini Twins.  Early in the month, the  stars are about one-third of the way up in the sky.

Mercury is beginning an evening appearance.  Early in the month, it is brighter, but closer to the horizon.

Twilight lasts longer this time of year, so it’s not visible in the latter sky glow as the sky darkens further.  So, the upcoming conjunction with Mars is better viewed with a binocular.  Both planets’ movements are easier viewed across several nights.

On June 5, the waxing crescent moon, the waxing crescent moon that is 2.7 days past the New phase and only 9% illuminated is 6.3° to the upper left of Mars, which sets at the end of evening twilight.  At this time the Red Planet is about 13° up in the west-northwest, a little over halfway between Castor and Pollux and the horizon.

Each evening until the conjunction, Mercury is closer to Mars.

On June 18, Mercury passes close to Mars, less than the moon’s apparent diameter.  The chart above shows them 45 minutes after sunset when they appear in the west-northwest.  Use a binocular to locate them.  Can you see them without a binocular?

As the month progresses, the planets appear lower and in a brighter sky. Continue to use a binocular to track the planets.

By month’s end, a dimmer Mercury appears to the upper left of Mars.

2019, May 19-21: Moon Passes Jupiter

As Jupiter approaches opposition, the event when our planet Earth is between Jupiter and the sun.  Jupiter and the sun are in opposite sides of the sky.  Jupiter rises when the sun sets and Jupiter sets when the sun rises.  Jupiter is in the south at midnight, when the sun is in the south at noon.

A few weeks before opposition, Jupiter appears in the evening and the morning sky.  Here’s what’s to see depending on when you step outside to see it.

Evening

  • May 19: At 10:30 p.m. CDT, the moon, 15.2 days past its New phase and 98% illuminated, is nearly 7° to the upper right of Jupiter and almost 9° to the left of Antares in the southeastern sky.

  • May 20: At 11 p.m. CDT, the moon, 16.2 days old and 94% illuminated, is nearly 7° up in the southeast and 6.5° to the lower left of Jupiter.

Morning

By morning , the moon appears in the southwest.

  • May 20:  At the beginning of morning twilight (about 4 a.m. CDT), the moon, 15.4 days old and 98% illuminated, is 4.6° to the right of Jupiter.  The Giant planet is 24° up in the south-southwest.

  • May 21:  At the beginning of morning twilight, the moon, 16.5 days old and 93% illuminated, is 25° up in the south and 8.2° to the left of Jupiter.

 

2019, May 6-7: Aldebaran, Mars, and the Crescent Moon

(On the chart above, the moon’s size is exaggerated.  At this scale, the star Zeta would be covered in May 7.)

The chart shows the western sky at about 1 hour after sunset.  Start looking for the moon beginning about 30 minutes after sunset.  Check your sources — television, newspaper, or Internet — for the time of your local sunset.

On May 6, the crescent moon (2.1 days past the New phase, 5% illuminated), 11° up in the west-northwest, is 2.2° to the upper right of Aldebaran, the brightest star in Taurus.   The moon is nearly 14° below Mars.

An hour after sunset, locate Mars between Elnath and Zeta Tauri, 4.5° to the lower left of Elnath and 3.4° to the upper right of the Bull’s southern horn.

On the next evening, an hour after sunset, the moon (3.1 days old, 11% illuminated) is 0.3° to the lower left of Zeta Tauri. Mars is 3.3° to the upper right of the star.

Use a binocular to look that the moon these two evenings.  You’ll notice that the moon’s night portion is slightly illuminated.  This is known as Earthshine.  From the moon, Earth is nearly full, and would be very bright to an observer on the lunar surface; it is bright enough to cast shadows on the moon’s night portion.  Earthshine is from reflected sunlight from Earth’s clouds, land, and oceans.  This sunlight gently illuminates the night portion of the moon in the same manner our planet is illuminated when the moon is near its Full phase.  Click here for an example of the crescent moon with Earthshine.