2018: The Evening Sky

This article summaries the planetary activity in the evening sky during 2018.  The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):

• Chart and Image Collection
• 2018:  The Morning Sky
• 2018:  The Evening Sky
• 2018:  Mercury in the Morning Sky
• 2018:  Mercury in the Evening Sky
• 2018:  Five Planets Visible at Once
• 2018:  Venus the Evening Star
• 2017-2019: Mars Observing Year with a Perihelic Opposition, July 27, 2018
• 2018:  Mars Perihelic Opposition
• 2017-2018:  Jupiter’s Year in the Claws of the Scorpion, A Triple Conjunction
• 2018:  Three Planets at Opposition in 79 days
• 2018:  Saturn with the Teapot

The chart shows the setting of planets, stars, and the moon (circles) compared to sunset.  This occurs in the western sky.  The three phases of twilight are graphed as well.

Conjunctions are displayed with squares.  Yellow triangles and the letters “GE” show the greatest elongation of Mercury or Venus.  A yellow diamond with the letters “GB” indicate the interval of Venus’ greatest brightness.

The rising of Mars, Jupiter, and Saturn are displayed.  This occurs in the east.  The opposition dates of those planets are also indicated.

It is important to emphasize that the chart shows setting times.  When the setting lines of two objects cross, it indicates that they set at the same time.  Because we have chosen planets and stars along the ecliptic, the virtual path along which the sun, moon and planets appear to move along, they can appear at conjunction or near each other.   This can occur within a few days of the date of coincident setting.  For the purposes of the chart, the conjunction is indicated on the setting time curve of the brighter planet.  When considering planets setting at the same time, consider this:  Sirius, the brightest star in the night sky, sets at about the same time as Aldebaran in Taurus.  The stars, though, are 46 degrees apart in the sky.  Sirius sets in the southwest and Aldebaran sets in the west-northwest.

The charts below summarize some of the evening events during the year.  This includes oppositions of Jupiter, Saturn, and Mars.  Just before the opposition of Mars, the five naked eye planets can be seen at once.  Observers at more southerly latitudes see this event easier.

Jupiter and Venus do not have a conjunction.  At the end of September the planets are closest at 14 degrees.

On March 18, Mercury passes about 4° from Venus with the moon nearby.

March 18: Mercury reaches its greatest elongation. This is Mercury’s best evening appearance during the year.

The moon can be seen in front of the stars of Taurus during 2018. On April 18 look at Taurus with binoculars to see the crescent moon in front of the Hyades.

Jupiter reaches opposition on May 8, 2018, near Libra’s bright star, Zubenelgenubi . This chart shows the three planets hours before the precise opposition time. Jupiter is in the southwest and Mars is in the southeast. The three bright planets are scattered across the southern sky. Saturn is 50 degrees to the left of Jupiter and Mars is 18 degrees farther to the left (east).

In early July, Venus passes the next signpost of the ecliptic, Regulus. This vivid blue star is less than one degree from Venus on July 9.

Saturn reaches opposition on June 27, coincidentally the night of the June full moon. Saturn starts retrograding on April 17 and concludes September 6. Jupiter is in the southwest; Mars is in the southeast.

Look for the five planets two to three days before and after the charted date (July 21). Find a clear horizon to see Mercury; binoculars may be needed to initially identify it. Twilight is longer, so look for the planets around chart time and before Mercury disappears below the horizon. The moon appears near Jupiter. Saturn is low the south-southeast, above the stars of the Teapot

Mars reaches its opposition on July 27, just 79 days after Jupiter reached opposition. It is now 15 times brighter than Saturn and nearly twice as bright as Jupiter. Jupiter is still retrograding near Zubenelgenubi. Saturn continues to retrograde away from the lid star of the Teapot . Mars retrogrades until August 27.

After its opposition, Jupiter appears farther west each night. During late summer Jupiter sets 80 minutes after sunset and it appears that Venus and Jupiter are headed toward a conjunction. After the Spica conjunction, Venus rapidly dives toward the sun’s glare as it moves toward its inferior conjunction with the sun. The closest Jupiter gets is 14 degrees on September 28, setting about 70 minutes after Venus

The third conjunction with Zubenelgenubi occurs on August 16 when Jupiter passes about 0.5 degree above the star. Jupiter passes the star three times during its apparition