Category: Sky Watching

Astronomy, Sky Watching

2020, February: Evening Star Venus, Mercury, and Moon
Venus Shines in Southwestern sky
2020, January 19: Venus is visible in the southwest about 40 minutes after sunset. The planet is now setting over 3 hours after sunset.

Brilliant Venus sparkles in the western sky after sunset.  It is so bright that Earth’s neighbor is often mistaken for a passing airplane.  Find Venus throughout February during the early evening hours.

The speedy planet Mercury pops into the evening sky after sunset for its best appearance of 2020.  As Mercury appears higher in the sky, it dims.  Find a clear horizon in the west-southwest and begin looking at about 45 minutes after sunset. It appears as a bright star.  Try to catch it early in its appearance and look for it each evening as it appears higher in the sky, but it is dimmer nearly every evening.  First attempt to look for it with a binocular; then look without optical help.

By mid-month, you’ll need a binocular to find it in the sky, as it much dimmer.

Venus appears high above Mercury.

Venus and Moon February 2020

The moon joins Venus late in the month.  On February 25, find a clear western horizon about 1 hour after sunset.  Each evening the moon is higher in the sky than the previous evening.

The best evening is on February 27, when the moon and Venus seem to appear in a scene of an artist.  Both are nearly at the same altitude above the horizon.  The moon is about 7° to the left of Venus.

You can capture “earthshine” on the night portion of the moon with a tripod-mounted camera.  Exposures ranging from 1 to 10 seconds reveal that the night is gently illuminated by sunlight reflected from Earth.

Here are more details about the moon’s appearance:

  • February 24: The moon returns to the evening sky. Thirty minutes after sunset, the moon (1.4 days past New, 2% illuminated) is nearly 6° up in the west-southwest. It is over 30° below brilliant Venus (m = −4.3).
  • February 25: In the evening sky, one hour after sunset, the moon (2.4d, 5%), over 10° in altitude in the west-southwest, is nearly 20° below Venus.
  • February 26: The moon is at apogee at 5:34 a.m. CST, 252,449 miles away. One hour after sunset, the moon (3.4d, 10%) is over 20° in altitude in the west-southwest. The lunar crescent is about 10° below brilliant Venus.
  • February 27:  In the evening, Venus and the moon (4.4d, 16%) are in a classic artist’s scene. Brilliant Venus is 6.7° to the right of the lunar crescent. Photograph the pair with a tripod-mounted camera. Vary exposures from 1-10 seconds to capture earthshine on the night portion of the moon.
  • February 28:  One hour after sunset, the waxing crescent moon (5.4d, 24%) is over 40° in altitude above the west-southwest horizon. It is nearly 15° to the upper left of brilliant Venus.
  • February 29: Happy Leap Day! In the evening, about one hour after sunset, the thick crescent moon (6.4d, 33%) is over 50° up in the southwest. Brilliant Venus is over 30° up in the west-southwest.

Happy Observing!

Astronomy, Sky Watching

2020, January 21: Mars, Moon, and Antares

Mars, Moon and Anatres January 21, 2020

During a cold, clear morning in the Chicago area, the planet Mars is about 5 degrees to the upper left of the star Antares, the Red Planet’s rival.  The star is about the same color and brightness as Mars when the planet passes by about every 2 years.

This morning the old moon (overexposed in the image above) appears to the lower left of the Mars-Antares pair.  Notice that the night portion of the moon is gently illuminated by the sunlight reflected from our planet.

See more about where to locate Mars.

Astronomy, Sky Watching

2020, Early February: Daylight and Darkness Equal

sunset over ocean

During early February, the sunrise point and the sunset point move rapidly northward. The sun’s daily arc across the sky is higher and longer.  Simultaneously, nighttime shortens.  Daylight and nighttime are balanced at the equinox. The start of Spring occurs on March 19, 2020, when their lengths are equal.

Recently, though I have been considering another equal-time event.  That is, the length of daylight and the length of darkness – the time after the end of evening twilight and the beginning of the next morning’s twilight.

Twilight occurs when the atmosphere is illuminated by the sun when our central star is below the horizon.  Immediately after sunset, the sky is bright, especially in the western sky.  It continues to darken until the sky’s illumination ends. This takes about 90 minutes, longer during the summer months as seen from the mid-latitudes. This reverses in the morning until sunrise.

So a 24-hour cycle has three phases, daylight, twilight, and darkness. Traditionally, twilight and darkness together make night. 

At the mid-latitudes, the length of daylight and darkness are equal at about 10.5 hours.  At my latitude, this occurs on February 11, 2020, with 10 hours, 26 minutes of daylight and the same length for darkness.

Astronomy, Sky Watching

2020, April 3: Spectacular View of Venus and Pleiades

Venus and Pleiades

 

Venus in Taurus: A Spectacular Pleiades Conjunction

For more about Venus as an Evening Star, visit this page.

In late March, Venus moves into Taurus, heading for a conjunction with the Pleiades. During April, Venus moves between the Pleiades and Hyades, and toward Elnath, the Bull’s northern horn.

Brilliant Venus is easy to spot and easily mistaken for a bright light on an airplane.  The Pleaides cluster is in the shape of a tiny dipper.  Its stars are not bright, but easily seen. Many times they initially draw your attention from the edge of your vision.

Step outside and look into the western sky about an hour after sunset. (Check your local sources for sunset in your location.)  As the sky darkens further, the Pleiades are easier to locate.

A binocular highlights the view of the cluster and the nearby checkmark-shaped Hyades.  With the yellow-orange star Aldebaran, the Hyades cluster makes a V-shape, although the Aldebaran is not part of the cluster.

Through the binocular, you should be able to count a dozen stars in the Pleiades cluster.  A telescope’s view is too narrow to catch the full cluster.

The chart above shows the motion of Venus as it moves near the star cluster. Here’s what to look for:

  • March 30: Venus moves into Taurus, 3.6° to the lower right of Alcyone (Eta Tauri on the chart), the brightest star in the Pleiades cluster.
  • March 31: At the end of evening twilight (about 90 minutes after sunset), Venus, over 25° up in the west, is 2.7° to the lower right of Alcyone. Watch Venus close the gap to Alcyone during the next several evenings.
  • April 3: One hour after sunset, Venus, 30° up in the west, is 0.3° to the lower left of Alcyone. This is the best night.  While Venus and the cluster appear close together, Venus is relatively nearby in our solar system, while the cluster is nearly 400 light years away!
  • April 4: This evening and for the next few evenings Venus and Sirius are at nearly the same altitude in the west at about 9 p.m. CDT in Chicago, a few minutes after the end of evening twilight (about 105 minutes after sunset). While Venus and Sirius are too far apart for technical comparisons of their brightness difference, the brightest star and the brightest planet are the same altitude in the western sky. Sirius, Orion’s belt, Aldebaran, and Venus are nearly in a line across the western horizon. The Venus – Alcyone gap, 0.9°. Gaps as Venus moves eastward along the ecliptic and away from the Pleiades: April 5, 1.8°; April 6, 2.7°; April 7, 3.5°; April 8, 4.6°; April 9, 5.2°.

Continue to watch Venus move through Taurus during the next several days.

Astronomy, Sky Watching

2020, January: Venus Sparkles in Evening Sky

Venus begins the New Year among the dimmer stars of eastern Capricornus. Now setting about 3 hours after the sun, watch Venus move eastward into Aquarius and toward a Neptune conjunction.

See our article about Venus as an Evening Star, 2019-2020

As the New Year opens, brilliant Venus is 35° east of the sun, setting nearly 3 hours after sunset.  Use a binocular to track Venus against the dimmer starfield.

On January 6 About an hour after sunset, Venus, nearly 18° up in the southwest, is 0.8° to the upper right of Gamma Capricorni (γ Cap, m = 3.6).

A few nights later, January 8, at an hour after sunset, Venus, nearly 19° up in the southwest, is 0.9° to the upper right of Delta Capricorni (δ Cap, m =2.8).

On January 11 Venus moves into the dimmer starfield of Aquarius.

Now setting in a dark sky on  January 20, over three hours after sunset, Venus is 4.3° to the upper right of Tau Aquarii (τ Aqr, m = 4.0).

Venus Shines in Southwestern sky
2020, January 19: Venus is visible in the southwest about 40 minutes after sunset. The planet is now setting over 3 hours after sunset.

On January 23 about an hour after sunset, Venus, 23° up in the southwest, is 1° left of Lambda Aquarii (λ Aqr, m = 3.7) and 4.5° to the lower right of Neptune (m = 7.9).

On January 26, through a telescope observe that Venus is 75% illuminated, an evening gibbous phase that is 15” across.

Near month’s end, on January 27, Venus is 40° east of the sun. At the end of evening twilight (about 6:30 p.m.), Venus, 18° up in the west-southwest, is 0.2° to the upper left of Neptune, nearly 7° above the crescent moon (3.1 days past the New phase, 9% illuminated) and 0.2° to the lower right of Phi Aquarii (φ Aqr, m =4.2).

The moon continues its appearance with Venus.  On January 28, at the end of evening twilight Venus, about 18° up in the west-southwest, is 7° to the lower right of the moon (4.1d, 15%).

Astronomy, Feature, Sky Watching

2020: The Evening Sky

2020 Setting Sky in west

This chart shows the summary of the setting of the naked-eye planets, moon, and bright stars near the ecliptic, the plane of the solar system, for 2020. The chart shows the setting of these celestial bodies compared to sunset for time intervals up to five hours after the sun’s disappearance. The three phases of twilight are displayed as well. On this chart, activity occurs in the western sky, except for the rising curves (circles) of Jupiter, Saturn and Mars. When they rise in the east at sunset, they are at opposition.

As 2020 opens, Venus is the bright Evening Star, appearing in the southwest. Mercury makes its best evening appearance, setting at the end of evening twilight during early February. Mercury’s June elongation is larger, but it sets several minutes before the end of twilight, making it difficult to observe in the brighter sky. After Venus moves past the Pleiades and Aldebaran, it moves toward Elnath (β Tauri), and then plunges toward its inferior conjunction. Jupiter and Saturn pass opposition during July. After Venus disappears from the evening sky, the slow procession of bright stars – Pollux, Regulus, Spica, and Antares – disappears into evening twilight. Jupiter and Saturn appear on the setting chart in late October, just after Mars reaches opposition. The moon has two interesting appearances with the planetary duo on November 19, 2020 and just days before the Jupiter- Saturn Great Conjunction on December 21, 2020.

The chart is calculated from data by the U.S. Naval Observatory, for Chicago, Illinois.

Key to symbols: White square, conjunction; yellow triangle, greatest elongation (GE); yellow diamond, greatest brightness (GB).