2018: The Morning Sky - When the Curves Line Up

Advertisements

Update: April 2, 2018, Mars and Saturn

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

The chart above shows the rising times of the planets, stars near the plane of the solar system, and the moon (circles) compared to the time of sunrise. The chart is drawn for Chicago, Illinois in the U.S.A. Central Time Zone from data from the U.S. Naval Observatory. The three phases of twilight are displayed as well. The chart generally displays activity in the eastern sky, except for the setting lines for Jupiter, Saturn and Mars. These three planets set in the western sky; their setting times are compared to sunrise. Each is at opposition during 2018: Jupiter, May 8; Saturn, June 27; and Mars, July 27. When at opposition, Earth is between the sun and one of those planets.

The three naked eye outer planets — Mars, Jupiter, and Saturn — are displayed when they are setting in the west during the morning.

It is important to emphasize that the chart shows rising times. When the rising lines of two objects cross, it indicates that they rise 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 rising time curve of the brighter planet. To consider when two planets rise at the same time, think about this: Betelgeuse, the reddish-orange star at Orion’s shoulder, rises at about the same time as Castor in Gemini. The stars, though, are 33 degrees apart in the sky. Betelgeuse rises in the east and Castor rises in the northeast.

The white squares on the chart indicate conjunctions between planets or stars and planets. For Mercury, the yellow triangles with the letters “GE” indicate the planet’s greatest separation from the sun as we see it; this is known as greatest elongation. For Venus, the yellow diamond with the letters “GB” indicate when the planet is at its brightest.

Four planets are visible in the morning sky early in the year. Mercury makes one of its two best appearances in January. The second occurs at the end of the year. Mars moves past Jupiter and Saturn early in the year. Mercury makes two more morning appearances during twilight: April and August. Venus jumps back into the morning sky late in the year. Jupiter also re-enters the sky later in the year.

Here are some highlights from planetary events in the morning sky (Click the images to see the details):

A few days after the Jupiter-Mars conjunction, the moon moves through the region and makes one of its closest passes near Jupiter during this appearance as viewed from the Western Hemisphere. The waning crescent moon is about 4 degrees from Jupiter

Figure 6: The Mercury-Saturn conjunction of January 13, 2018.

A total lunar eclipse is visible across Asia, Australia, and the Pacific Basin. Western North America sees most of the total phase of the eclipse.

In early April, Mars moves past Saturn. The separation is just over 1 degree. Mars is growing in brightness and heading toward its own opposition in July, yet it is only slightly brighter than Saturn at this conjunction.

On April 7, the moon passes 1.5 degrees from Saturn, making one of the closest passings of the year. The moon is about 1.5 degrees from Saturn.

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).

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.

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.