2016, September 2: Venus, Jupiter, Moon, Mars & Saturn

DSC03676

Brilliant Venus gleams during twilight this evening as seen from the Chicago area with a waxing crescent moon and Jupiter appearing lower in twilight.  (To see Jupiter click the image to see it larger.  The planet appears at the tip of the  arrow.)  The moon is 5 degrees to the lower right of Venus with Jupiter another half degree farther to the  right.  Notice the separation of Jupiter tonight compared it its position during the Epoch (close) Conjunction last Saturday.

Here’s a preview of the Moon and Venus tomorrow evening.

Our images and charts collections are available here –> http://goo.gl/Sfp1ur

See our article about Venus’ evening appearance.

See our  article outlining the planets in the evening sky in 2016.

DSC03679

Meanwhile, Mars, Saturn and the star Antares appear in the south as the sky darkens.  The trio is in the sky during the evening, setting in the west as they appear to move that direction during evening hours.  Mars is advancing farther east compared to the starry background.  Tonight it is 6 degrees from Saturn and 5 degrees from Antares.

2016-2017: Jupiter’s Year With Spica, A Triple Conjunction

DSC02879

Figure 1: Jupiter’s Morning Appearance in Late 2015 with Venus and Mars

In late September 2016, Jupiter begins a 396-day appearance that includes a triple conjunction with the star Spica.  A triple conjunction occurs when a planet appears to passes  a star or another planet three times during a single appearance.  There are multiple definitions of a conjunction:  The simplest is the closest separation between a planet and another celestial object.  Two others are based on coordinate systems:  the solar system plane (ecliptic) and the plane of the earth’s equator (equatorial).  Coordinate systems have specific names longitude and latitude.  In these systems conjunctions occur when the star’s longitude is the same the planet’s changing longitude as it revolves around the sun.  One could say that an airplane flying across the country is in conjunction with a city when its longitude matches the city’s longitude.  For our purposes a star’s celestial coordinates are constant while the planet’d coordinates change as it revolves around the sun.

eq_ecl

The celestial equator and ecliptic

Since the ecliptic is angled with the celestial equator by 23.5 degrees, a planet’s ecliptic longitude and equatorial longitude are not the same.  For this article, the triple conjunction occurs in the equatorial coordinate system.

Jupiter begins its morning appearance on September 26, 2016, nearly a month after its Epoch Conjunction with Venus.  On this date, Jupiter is  behind the sun in solar conjunction.

Jupiter completes one solar orbit about every 11 earth years.  Because Jupiter slowly lumbers through its orbital path, it does not travel far during the earth’s annual path around the sun.

jup_conj_160926

Figure 2:  Jupiter at conjunction

The chart above shows the positions of Earth and Jupiter with the sun in between (conjunction).  The sun’s bright glare blocks us from viewing Jupiter.

jup_am_16

Figure 3:  Jupiter rising in the morning sky

Jupiter then begins its appearance in the morning sky, initially rising during twilight.  By mid-October, it rises about an hour before sunrise.  The chart above shows the rising times of Jupiter, the star Spica, Mercury, and the moon (circles) compared to sunrise. (As the moon heads towards its new phase, it rises later each morning.) The astronomical twilight line represents the time when the sky is as dark as it every gets naturally.  As the sky brightens, the ground can be discerned from the sky:  Nautical twilight.  So named because at sea the horizon clearly separates the water and the sky.  At Civil Twilight, the sky is bright, most details of terrestrial features can be identified.  Street lights normally off on during the time between Civil Twilight and sunrise (or turn on during evening Civil Twilight).

Jupiter rises early each day, appearing higher in the eastern sky as sunrise approaches.  On October 11, the Mercury and Jupiter line cross, indicating that they rise at the same time.

 jup_merc_161011

Figure 4:  Jupiter and Mercury, October 11, 2016

On this date, Mercury passes less than one degree from Jupiter.  This chart shows them about 30 minutes before sunrise.  Binoculars may be needed to locate Mercury in the brightening twilight before sunrise.  Locate a clear eastern horizon as the pair is just 5 degrees above the horizon. (See this article for more details of Mercury’s morning appearance.)

jup_lune_161028

Figure 5:  The moon and Jupiter’s closest approach to Gamma Virginis

By late October, Jupiter rises at the beginning of astronomical twilight and by year’s end it rises over 5 hours before sunrise.  Notice that on October 28, Jupiter and the moon rise at nearly the same time.  Jupiter’s closest approach to the star Gamma Virginis is on this morning, but the planet passes this star two mornings later in the equatorial system.

jup_retro-17

Figure 6:  Jupiter’s retrograde & Spica Conjunctions

Jupiter’s westward march with the stars is from the earth’s orbit around the sun.  The Giant Planet appears to move against the starry background as well; this is from the planet’s orbital progression and the faster earth’s orbit around the sun.  On the diagram (Figure 6) above, Jupiter is shown beginning October 28, 2016 when is rises over 2 hours before the sun with each yellow dot representing a day.  The planet moves noticeably eastward in the general direction of the bright star Spica.

jup_spica_161028

Figure 7:  October 28, Jupiter and the star Spica are separated by 14 degrees

This chart shows Jupiter and Spica on October 28, 2016, date on that Jupiter is shown on the previous chart (Figure 6).  Jupiter appears low in the predawn eastern sky before sunrise with a waning crescent moon.  Spica is 14 degrees below Jupiter near the horizon.  (This is the same morning that Jupiter passes Gamma Virginis.  See Figure 5.)

jup_spica_161115

Figure 8:  Jupiter and Spica:  November 15, 2016

By mid-November, Jupiter rises over 3 hours before the sun.  The star Spica appears about 10 degrees below Jupiter.  From the the sunrise chart (Figure 3) above, notice that the time between rising times for Jupiter and Spica narrows throughout 2016.  Jupiter appears to move farther east compared to that starry background.

jup_spica_161231

Figure 9:  December 31, Jupiter and Spica are 4 degrees apart.

By year’s end, Jupiter appears to move eastward until it is about 4 degrees above Spica. Jupiter is slowing in its apparent eastward movement (See Figure 6), although it does not slow in its orbital motion.

jup_90w-170111

Figure 10:  January 11, 2017, Jupiter appears 90 degrees from the sun

As the weeks pass, Jupiter rises earlier each morning from the Earth’s revolution around the sun.  On January 11, Jupiter appears 90 degrees west of the sun, meaning that it rises around midnight and by sunrise it is in the south.

jup_spica_170120

Figure 11:  January 20, the first conjunction of Jupiter and Spica

Jupiter passes Spica the first time on January 20, 2017 when they are about 3.5 degrees apart.  Jupiter appears to slow its eastward movement, but its orbital speed stays the same.

jup_spica_170209

Figure 12:  February 9, 2017, Jupiter appears to be stationary.

Compared to the background of stars, Jupiter appears to stop its eastward motion on February 9, 2017 (See Figure 6), and appears to begin to move backward (west) compare to the stars.

jup_spica_170223

Figure 13:  February 23,  Jupiter’s second conjunction with Spica.

As Jupiter retrogrades, it passes Spica again on February 23, by a margin of nearly 4 degrees.

jup_opp_170407

Figure 14:  April 7, 2017:  Jupiter is at opposition

This apparent westward motion is continues until June 8, 2017.  On April 7, Earth moves between the sun and Jupiter (See Figure 6).  This is known as opposition; that is, Jupiter and the sun are on opposite sides of our planet and appear on opposite sides of the sky.  When the sun sets in the west, Jupiter rises in the east.  As Earth rotates, Jupiter appears south at midnight and by sunrise Jupiter is in the western sky as sunrise approaches in the eastern sky.

jup_spica_170407

Figure 15:  April 7, 2017, Jupiter at opposition with Spica nearby

As shown in this diagram, Jupiter and Spica appear in the early evening sky on opposition night.

jup_spica_170628

Figure 16:  June 28, 2017, Jupiter stops retrograding

Jupiter continues to retrograde and appearing farther west each evening as compared to Spica (See Figure 6).  On June 28, 2017, Jupiter stops retrograding and again appears to move to the eastward against the sidereal background.  The eastward progress is small at first glance, then Jupiter’s eastward motion is easily observed.

jup_pm_17

Figure 17:  The western evening sky at.  This chart shows the stars, planets, and the moon setting times compared to sunset from June 15, 2017 to November 2, 2017.

Jupiter sets earlier each evening as shown in this chart which shows the objects setting times relative to sunset.  Notice the proximity of the Jupiter setting line and the Spica setting line.  Before early August 2017, Jupiter sets before Spica.  After that date it sets after Spica.  Other diagrams in this article show their relative positions in the sky,  The moon setting time is indicated by the circles.

jup_90e-170705

Earth’s faster speed carries it past Jupiter and by July 5, 2017, Jupiter appears 90 degrees east of the sun, visible in the southern sky at sunset.  This is nearly a month after Jupiter appears to resume its eastward motion compared to the stars and the stellar signpost Spica.

jup_spica_170905

As Jupiter and Spica disappear into the sun’s glare as Jupiter heads for another solar conjunction (October 27, 2017), this solar system giant, appears to pass Spica again (3.3 degrees) for the third conjunction of this apparition — a triple conjunction.

jup_spica_170912

Jupiter’s track leaves the retrograde diagram (Figure 6), on September 12, 2017 after 337 days of chronicling the planet’s apparent movement in the sky.

jup_conj_171027

The earth’s orbital speed carries Jupiter behind the sun to solar conjunction only for Jupiter to reappear in the morning sky in 2017.  Jupiter is headed for a December 21, 2020 conjunction with Saturn when the pair appear 0.1 degree apart.  Meanwhile the next Venus-Jupiter conjunction is November 13, 2017 — another Epoch (close) conjunction of those planets during bright morning twilight.

Appearances with the Moon

Morning dates, visible before sunrise, when Moon appears near Jupiter.  Bookmark this page to see photographs of the groupings, weather permitting.

  • October 28, 2016
  • November 24 & 25, 2016
  • December 22, 2016
  • January 19, 2017
  • February 15, 2017  (Look late in the evening as well)
  • March 14 & 15, 2017 (Late pm as well.)

Evening dates

  • April 10, 2017
  • May 7, 2017
  • June 3, 2017
  • June 30 & July 1, 2017
  • July 28 & 29, 2017
  • August 24 & 25, 2017
  • September 21, 2017

Our images and charts collections are available here –> http://goo.gl/Sfp1ur

2016: Mercury’s Autumn Morning Appearance

merc_lune_160929

The speedy planet Mercury makes a  predawn appearance  in the eastern morning sky during late September. Likely  the best date to view Mercury is on September 29, 2016 when the moon appears below it as the chart shows above.  The chart above shows the pair at about 50 minutes before sunrise as seen from the Chicago area.  Find a clear eastern horizon.  At this time Mercury appears about 8 degrees above the eastern horizon, immediately above a thin crescent moon.

merc_am_16

 The cycle begins when Mercury passes between the earth and sun (inferior conjunction) on September 13.  It rapidly rises into the morning sky.  The chart above shows the rising time of Mercury, the moon, Jupiter and Spica compared to sunrise.  Mercury rarely appears in a dark sky.  It reaches its greatest separation from the sun (greatest elongation), shown as GEW on the chart, and then descends back into bright twilight until it passes on the far side of the sun at superior conjunction on October 27.

On September 29, the moon rises at about the same time as Mercury and its view in the sky is depicted at the top of this article.

jup_merc_161011

On October 11, Jupiter and Mercury rise at the same time, at the beginning of Nautical twilight, the time when the horizon can be distinguished.  This chart shows that they less than one degree apart.  This chart is calculated for 30 minutes before sunrise when the sky is moderately bright.  Use binoculars to locate the planets.

merc_gew_160928

Mercury is a difficult planet to locate.  At this greatest elongation, it is only 18 degrees west of the sun, yet the angle the plane of the solar system makes with our horizon makes Mercury easily spotted in bright twilight.  As the inner most planet, Mercury is always near the sun.  The chart above shows Mercury at greatest elongation along with the its imaginary orbit.

The September morning sky provides a view of Mercury and the reappearance of Jupiter after its Epoch Conjunction with Venus.

Our images and charts collections are available here –> http://goo.gl/Sfp1ur

2016: August 27, Venus and Jupiter

DSC03635

Venus and Jupiter in close conjunction this evening as seen from the Chicago area.  Click the image to see the separation between the planetary pair.

Click here for more information about the Venus-Jupiter Epoch Conjunction.

Our images and charts collections are available here –> http://goo.gl/Sfp1ur

2016: August 22, Venus, Jupiter, Mars & Saturn

DSC03623

Just 5 days before the Epoch Conjunction of 2016, Venus and Jupiter shine from the western sky this evening as seen from the Chicago area on an unseasonably cool and clear evening.  Tonight pair is 5 degrees apart.   (See this article for more details.)

DSC03624

Meanwhile Mars, Antares, and Saturn appear near each other in the southwest.  Mars is 2 degrees  from Antares and 4.5 degrees from Saturn.  Watch Mars pass Antares and Saturn this week.

2016: August 16, Venus and Jupiter

DSC03574

Just 11 days before the Great Venus-Jupiter Epoch Conjunction of 2016, Venus and Jupiter shine from the western sky this evening as seen from the Chicago area. (See this article for more details.) Tonight the pair is 11 degrees apart and closing rapidly.  Venus is very low in the western sky at about 40 minutes after sunset with Jupiter to its upper left.

2016: August 15, Venus and Jupiter

ven_jup_160815

As Venus emerges from the sun’s brilliant glare, it is 12 days before the Venus-Jupiter Epoch Conjunction of 2016 with the two appear to pass fractions of a degree apart.  (See this article for more details.)  Tonight Jupiter and Venus are 12 degrees apart.  Mercury is nearly in between them.  It is rapidly disappearing into the sun’s glare.  Mercury appears in the morning sky, making its morning appearance of the year in late September and early October.

The chart above shows the planets at 8:30 p.m. CDT as seen from the Chicago area.  For your local circumstances, look west about 40 minutes after sunset.  Venus is very low in the western sky.  Binoculars may be need to first locate it.  It is easily spotted without optical aid once it is located.  Jupiter is the bright star to the upper left of  Venus.  Locate Mercury with binoculars.