2016, August 27: A Venus-Jupiter Epoch Conjunction

The June 30, 2015, Venus-Jupiter Conjunction.  The 2016 conjunction is closer.

An Epoch Conjunction

Just 424 days after the last Epoch Conjunction, Venus and Jupiter pass again in the western, evening sky on August 27, 2016, shortly after sunset.  The image above shows the two planets during were about one-third of a degree in separation during the 2015 conjunction.  The 2016 conjunction is three times closer.  This article outlines the circumstances of conjunctions between Venus and Jupiter, the events of this conjunction, and concludes with a list of future Venus-Jupiter conjunctions.

See this article for more as Venus as an Evening Star during 2016-2017.

Conjunctions of the bright planets occur when they appear to move past each other in the sky.  Sometimes they seem to nearly meet, although they are millions of miles apart.  A Venus-Jupiter conjunction occurs between 34 days and 449 days, depending on the relative positions of the three planets (this includes Earth).  Venus revolves around the sun once in about 225 days.  Because our planet is moving, Venus catches up to and passes by Earth every 584 days.  Jupiter is a slower moving participant in this celestial waltz as it revolves around the sun once in nearly 12 years.

Venus-Jupiter conjunctions occur somewhat frequently; the close ones of are great visual interest, because to the unaided eye, the planets appear to merge together.  While not a “once-in-a-lifetime”event, these close conjunctions are infrequent enough to attract the attention of even the casual sky watchers.  Robert C. Victor, former staff astronomer at Abrams Planetarium, calls these close conjunctions “epoch conjunctions.”

Venus is always visible near the sun as it is closer to the sun than Earth.  From our planet it never appears more than about 45 degrees from the sun.  When it is east of the sun, it appears in the western sky just after sunset.  When it is west of the sun, it appears in the eastern sky, just before sunrise.

Jupiter’s movement in the sky largely follows the earth’s revolution around the sun and mostly reflects the annual westward advancement of the starry background.  Jupiter first makes a morning appearance in the eastern sky, just past conjunction when Jupiter is on the far side of its orbit behind the sun.  Each week it appears higher in the sky and farther west at the same time each morning.  Several months later, it appears in the western sky just before sunrise from this slow westward celestial migration.  At this time it is at opposition with Earth between the sun and Jupiter; they are on opposite sides of our sky.  At this time, Jupiter rises a sunset, appears in the south at midnight and sets at sunrise — appearing in between at other times during the night.  Jupiter continues to rise earlier each week, eventually appearing in the south at sunset.  As Jupiter heads for conjunction (behind the sun) it appears in the western sky at sunset, eventually setting with the sun.  This entire cycle takes 399 days.

Because Venus’ orbit is inside Earth’s orbit, Venus never appears more than 45 degrees from the sun, the Venus-Jupiter conjunction appears within region of the sky when Jupiter is near conjunction.  Additionally, if the Venus-Jupiter conjunction occurs too close to the sun, the planets are hidden in the sun’s brilliant glare.  In recent times, 75% of the conjunctions occur when Venus and Jupiter are very close to the sun.

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During the June 2016 conjunction, Venus is emerging from behind the sun (superior conjunction).  Venus is only 22 degrees from the sun, setting 56 minutes after the sun, and before Nautical Twilight.  Jupiter is nearing its solar conjunction which is caused more by the earth’s revolution than Jupiter’s orbital movement.  The two planets are about 450 million miles apart, although they appear about 7′ (7 minutes= 0.10 degrees, much less than a full moon diameter) apart.

The Conjunction

Here are the events leading up to the conjunction.

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On August 1, Venus is low in the western sky.  Find a clear horizon to see it.  Bright Jupiter is 26 degrees to the upper right of Venus.  Mercury is  about 8 degrees to the upper right of Venus.

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While not a good appearance, the evening of August 4, 2016, presents another opportunity to view all five naked eye planets simultaneously.  Locate a clear horizon looking west.  Venus stands about 3 degrees above the western horizon.  While it is bright in the twilight, binoculars may be needed to first locate it.  A thin crescent moon appears 10 degrees to the upper left of Venus, with Mercury  2 degrees to the upper right of the Moon.  Jupiter is higher to the upper left of the moon (14 degrees).  Saturn and Mars in the southern sky, near the star Antares.

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On August 6, the separation between Venus and Jupiter decreases to 21.5 degrees with the moon 10 degrees to the upper left of Jupiter.

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On August 15, Mercury is rapidly disappearing from the sky.  Tonight Venus and Jupiter are 12 degrees apart.

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By August 20, the Venus-Jupiter distance is 7.5 degrees.

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On August 24, the pair is 3 degrees apart.

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Two evenings later and the evening before the conjunction, the Venus-Jupiter distance is 54′ apart.

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August 27, 2016 is conjunction evening when the two planets are 7 arc minutes apart!

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In a telescope at about 80 power, Jupiter and its four largest moons are visible along with Venus.  The view through your telescope may be inverted or backwards left to right, depending on the optical design.  The four largest moons are in a plane that is along the cloud bands of the planet.

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On the evening following the conjunction, the planets are 1 degree apart. with Jupiter to the lower right of Venus.

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On August 30, the planets have separated to 3 degrees.

The planes continue to separate and Jupiter disappears into the sun’s glare heading for solar conjunction (September 26, 2016).

Upcoming Venus-Jupiter Conjunctions

The table below shows the next 7 close Venus-Jupiter conjunctions.  The November 2017 conjunction and the February 2025 event rival this conjunction in separation.   Following the conjunctions mentioned on this list, a close conjunction (28′) occurs on August 23, 2038 followed by a closer conjunction occurs on November 2, 2039 (13′).  Other more widely spaced Venus-Jupiter conjunctions (30′ to 2 degrees) occur in the interim.

Conjunction Dates Separation Location Visibility
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November 13, 2017 20’ Morning(east) During this conjunction the planets rise in the east-southeast about 75 minutes  before sunrise.  In separation, it rivals the June 2015 conjunction, but it appears low in the sky.
November 24, 2019 1 degree, 28 minutes Evening(west) The planets in this widely spaced conjunction are nearly 3 full moon diameters apart.  They are visible low in the southwestern sky during twilight and early evening, setting about 1 hour, 35 minutes after sunset.
January 22, 2019 2 degrees, 24 minutes Morning (east) The planets in this widely spaced conjunction are far apart visually, but easily seen as they rise about 3 hours before sunrise and appear in low in the southeastern sky as morning twilight begins.
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 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.

2016, May 9: Transit of Mercury

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Never view the sun directly.  Project the sun on a flat surface using a mirror.

On May 9, 2016, just after Mercury makes its best appearance of the year, it passes nearly directly between the earth and sun.  From our planet, Mercury passes across the face of the sun — a transit.  Mercury’s rapid orbit around the sun carries it between Earth and our central star every 116 days.  Normally, as Mercury passes between these celestial wonders, it is not in a direct line with them; it appears to pass above or below the sun.

Mercury crosses in front of the sun 13-14 times a century and currently this can occur during the months of May and November, when the tilted orbit of this speedy planet crosses the earth-sun plane.  Following this event, the next transit of Mercury is November 11, 2019.

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This chart shows the path of Mercury in front of the sun on May 9. (Click the image to see it larger.)

As seen from Chicago, the sun rises at 5:37 a.m. CDT.  The transit begins at 6:13 a.m. CDT when the edge of Mercury touches the edge of sun.  The sun is low in the sky, only 6 degrees when this occurs.  By 6:16 a.m. CDT, Mercury’s disk is completely in front of the sun.  Mercury slowly inches across the sun during the morning.  The entire event takes 7 hours, 28 minutes.  By 9:58 a.m. CDT, Mercury reaches the Greatest Transit Point, the point when it is closest to the sun’s center.  By 1:38 p.m. CDT, Mercury’s final appearance in front of the sun occurs and the speedy planet begins moving from the sun’s face.  By 1:41 p.m. CDT, Mercury leaves the sun’s face and the event is over.

It is important to never look directly at the sun.  Group viewing of the event can occur with a solar projector.  Cut a dime sized hole in a sheet of paper.  Cover a mirror with the paper.  Reflect the sun’s image on a flat surface.  Mercury appears as a small dot in front of the sun.  If sunspots are present, they will appear as well.

2016: April 25: Mars, Saturn and Moon

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On the evening/morning of April 24/25, the moon appears near Mars and Saturn in front of the stars of Scorpius with its bright star Antares.  Mars is nearing opposition (May 22) and it is the brightest “star” in this part of the sky.  At this opposition, it is about 45 million miles from Earth.  Mars appears about 4 degrees below the moon.  Ringed Saturn is dimmer and is approaching its opposition (June 3).  It appears nearly 6 degrees to the left of the moon.

The star Antares is distinctly reddish in appearance.  Views through binoculars accent its color.  The star’s name is sometimes translated as the “Rival of Mars,” but at this time, Mars is over 6 times brighter than its stellar nemesis.  The star is one of the largest known to astronomers, yet its immense size is reduced to a point of light by its distance of about 600 light years.

The chart above shows the grouping at 5 a.m. CDT as seen from the Chicago area.  The moon rises just after 10 p.m. CDT on April 24.  So for those observers who are up late, the grouping appears low in the southeast around midnight.  As the night progresses, they appear farther west and by 5 a.m. (April 25), the group is in the south-southwest.

New Ceres Images Show Bright Craters

From NASA

Craters with bright material on dwarf planet Ceres shine in new images from NASA’s Dawn mission.

In its lowest-altitude mapping orbit, at a distance of 240 miles (385 kilometers) from Ceres, Dawn has provided scientists with spectacular views of the dwarf planet.

Haulani Crater, with a diameter of 21 miles (34 kilometers), shows evidence of landslides from its crater rim. Smooth material and a central ridge stand out on its floor. An enhanced false-color view allows scientists to gain insight into materials and how they relate to surface morphology. This image shows rays of bluish ejected material. The color blue in such views has been associated with young features on Ceres.

For the complete article, click this link.

2016, April 17: Jupiter and Moon

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That bright star near the moon this evening is Jupiter. The accompanying chart shows the pair high in the southeastern sky tonight at 9 p.m. CDT. Jupiter and the moon are 2.5 degrees apart. The star Regulus is nearby.

Jupiter and the moon appear together throughout the evening and night as our planet rotates, and they appear to move westward.  In the Chicago area, the moon sets in the west at about 4:30 a.m. CDT.

While Jupiter and the moon appear close together, Jupiter is nearly 1800 farther away than the moon, yet Regulus is over 3.5 million times more distant than Jupiter.

Did you see Mercury this evening?  For the next several evenings, look low in the west-northwest about an hour after sunset.  Here’s our view from last night.

2016, April 16: Mercury in Western Sky

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Mercury is making its best appearance of the of year during the next several evenings.  Tonight it appears to the lower right of the Aldebaran and the Pleiades. It is two evenings before its greatest separation from the sun, setting nearly 2 hours after sunset. This image was made this evening at 8:30 p.m. CDT as seen from the Chicago area.

For more about this appearance, click here.

2016: Mercury’s Best Appearance This Year

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Elusive Planet Mercury makes an appearance in the western evening sky during early spring 2016, its best evening appearance of the year.  On the evening of April 18 it sets nearly two hours after the sun.  The chart above shows Mercury about 1 hour after sunset as seen from the Chicago area.  On this evening Mercury appears about 11 degrees to the lower right of the Pleiades and nearly 22 degrees to the lower right of the star Aldebaran.  The brighter stars of Orion (Betelgeuse and Rigel) are included for scale.

On the above chart Mercury is about 10 degrees above the west-northwest horizon. Neighbors’ trees or house, likely, could block it.  Find a clear view of the horizon  Aldebaran and Mercury are about the same brightness.

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This chart shows the setting time of Mercury compared to sunset and the end of the three phases of twilight.  At its greatest separation from the sun (greatest elongation east, GEE on the chart) on April 18, Mercury sets after the end of astronomical twilight.  (The chart is graphed from U.S. Naval Observatory data.)

As the planet approaches its greatest elongation, it brightens as it approaches our planet, moving toward its inferior conjunction, between Earth and the sun.  The best times to see the planet are around the greatest separation and when it sets before the end of nautical twilight near the end of April.

Mercury is best seen in the western evening sky on spring evenings and in the eastern evening sky during autumn mornings.  The angle that we see our solar system is best at those times.  This link shows a chart for the setting of stars and planets in the evening western sky and this link shows the rising of planets in the eastern morning sky during 2016. The best morning appearance this year occurs during late September.

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