Astronomy, Sky Watching

2020, August 15-16: Helical Rising of Sirius

The first appearance of Sirius low in the east-southeast during mid-August 2020.
2020, August 15-16: The helical rising of Sirius is the star’s first appearance in the morning sky before sunrise.

The annual first appearance of Sirius in the morning sky is a spectacular sight.  During 2020, this occurs in mid-August.

by Jeffrey L. Hunt

The spectacular appearance of a bright star in the morning before sunrise is an impressive sight. While very low in the sky, the star twinkles against the brightening hues of morning twilight.

The first morning appearance of a star in the eastern sky before sunrise is known as the “heliacal rising” of the star.

The first morning appearance of Sirius attracts attention. The brightest star in the sky, it can be found near the horizon before we see other bright stars.

In the lore of earlier generations, the heliacal rising of Sirius was thought to cause “dog days.” It’s coincidental that the “Dog Star” first appears in the morning sky during the hot days of the year.

Observing the first morning appearance of a bright star is a challenging feat. This requires a perfectly clear sky to the horizon and a vantage point to see the natural horizon, free from trees, buildings, houses, and other obstructions.

A Sky and Telescope magazine article described the circumstances of the date of the heliacal rising of Sirius. The author described that when the sun is about 8° below the horizon and Sirius is 3° in altitude in the east-southeast sky, the star should be first visible. For this writer’s latitude (41.7°), no single date meets the criteria. The best pair of days is August 15, 2020, and the following morning. On the former morning, Sirius is slightly lower than 3° and on the morning of the latter it is slightly higher than the visible limit.

The chart above shows the sky 42 minutes before sunrise on August 16, 2020. Bright Venus and the crescent moon are high in the east.

Betelgeuse, Procyon, and Sirius – while they are part of their own constellations – make a large equilateral triangle, known as the Winter Triangle. The trio is prominent in the evening sky during the colder months in the Northern Hemisphere.

Procyon is sometimes translated as “before the dog.” It rises about 25 minutes before Sirius, so it rises before the Dog Star.

For beginners, start looking in the morning sky about August 12. Locate Betelgeuse and Procyon. A binocular may help you initially find the stars. Venus is nearly above Procyon, although the planet is much higher in the sky. On the diagram, Procyon is only 8° in altitude; that’s about one-tenth of the way up in the sky from the horizon to overhead (zenith). Betelgeuse is higher, about one-third of the way up in the sky, at about the same altitude as brilliant Venus. Once you see the two stars, you can visualize the scale of this large celestial triangle.

After you recognize Procyon and Betelgeuse, look each clear morning to continue to find the visible pair. Then scale the other two sides of the Winter Triangle, Betelgeuse – Sirius and Procyon – Sirius, and attempt to look for the nighttime’s brightest star very low in the east-southeast sky.

For observers north or south of this writer’s location, shift the helical rising date one or two days earlier for the southern United States and similar latitudes. Add one to two days for locations farther north.

When do you first see Sirius? Respond in the comments section of this article.

Read the Venus as a Morning Star, 2020-2021 article.

Astronomy, Sky Watching

2020, May 24: Brilliant Evening Star Venus, Mercury, and Moon
Venus, Moon, and Mercury, May 24, 020
2020, May 24: The moon, Mercury, and Venus appear in the sky this evening, (Photo by Tim S.)

By Jeffrey L. Hunt

As Venus moves toward its inferior conjunction on June 3 and into the morning sky, Mercury is emerging into the evening sky. This evening the speedy planet is 5.5° to the upper left of Venus. The crescent moon, 2,3 days past the New phase and 5% illuminated, is nearly 12° to the upper left of Venus. The star Elnath – the Northern Horn of Taurus – is 4.6° above Venus and 3.5° to the upper right of Mercury.

Here’s more about Mercury in the evening sky.

Read this article for more about Venus as an Evening Star.

Looking ahead, here’s the Venus as a Morning Star, 2020-2021, article.

Astronomy, Sky Watching

2020, May 24: Morning Planets, Jupiter, Saturn and Mars.

Jupiter, Saturn, and Mars, May 24, 2020
2020, May 24: Jupiter and Saturn are 4.7° apart as they shine from the southern skies. Mars is 40° to the east of Jupiter. It appears in the southeast.

Jupiter, Saturn, and Mars shine in the sky before sunrise today.

by Jeffrey L. Hunt

This morning the three morning planets – Jupiter, Saturn, and Mars – appear in the sky from southeast to south. Bright Jupiter is about one-quarter of the way up in the south. This giant planet is 4.7° to the right of dimmer Saturn.

Both planets are retrograding. They appear to move westward compared to the starry back ground. During the next several weeks, watch them separate. Later this year, Jupiter passes Saturn in a Great Conjunction.

Meanwhile, Mars is in the southeast. It continues to move way from Jupiter and Saturn. This morning it is over 40° from Jupiter.

Next month, Venus joins this planetary trio.

For more details about the morning planets, read more here.

For our daily semi-technical description of May’s planet events, click here.

Astronomy, Sky Watching

2020, May 23: Venus and Mercury
Venus, Mercury and Elnath, May 23, 2020
2020, May 23: Brilliant Venus appears with Mercury and Elnath in the evening sky.

by Jeffrey L. Hunt

Expecting to see the moon with Venus, storm clouds prevented the view. When the sky cleared, the moon had set. Venus sparkled low in the west-northwest. In the image above, Venus, Mercury, and Elnath are grouped into a pretty triangle. Mercury is 3.5° to the upper left of Venus and 3.1° to the lower left of Elnath The Venus- Elnath gap is 4.2°.

Venus is rapidly leaving the evening sky. In a few evenings it no longer appears there. After mid-June, it appears low in the east-northeast before sunrise.

Mercury is entering the evening sky for a brief appearance.

Here’s more about Mercury in the evening sky.

Read this article for more about Venus as an Evening Star.

Looking ahead, here’s the Venus as a Morning Star, 2020-2021, article.

Astronomy, Sky Watching

2020, May 22: Venus and Mercury in the Evening Sky
Venus, Mercury, and the star Elnath in the evening sky, May 22, 2020
2020, May 22: Venus, Mercury, and Elnath make a compact triangle. Venus is 1.6° to the lower right of Mercury; Venus is 3.8° below Elnath; and the Mercury – Elnath gap is 3.4°.

Mercury Joins Venus in the Evening Sky

by Jeffrey L. Hunt

This evening Mercury appears 1.6° to the upper left of brilliant Evening Star Venus. Mercury continues to move beyond Venus. Venus is leaving the evening sky as it moves between our planet Earth and the sun on June 3.

Mercury is beginning its short evening journey before it heads to the morning sky in July where it joins four bright morning planets for an infrequent opportunity to see the five naked-eye planets simultaneously.

The star Elnath – the Northern Horn of Taurus – 3.8° above Venus.

The moon enters the scene tomorrow evening.

Here’s more about Mercury in the evening sky.

Read this article for more about Venus as an Evening Star.

Looking ahead, here’s the Venus as a Morning Star, 2020-2021, article

Astronomy, Sky Watching

2020, July: Venus Moves Through Taurus
Venus in Taurus, July 2020
2020, July: Venus in the Hyades. Venus passes Aldebaran July 12.

As a brilliant Morning Star, Venus passes through the Hyades during July 2020. Use a binocular to track the planet thorugh the starfield.

by Jeffrey L. Hunt

Read this article, for more about Venus as a Morning Star

Click here for our semi-technical summary of Venus as a Morning Star.

During July and early August, Venus moves through Taurus – from the Hyades to Zeta Tauri, the Bull’s Southern horn. As Venus moves through the star cluster, note the planet’s position each morning compared to the starfield. The Hyades star cluster, with Aldebaran, appears to make a letter “V” in the sky. While in the eastern sky the letter is on one side.  Aldebaran is at the top of one side of the “V.”  Epsilon Tauri marks the top of the other side.

While in the period of greatest brightness, Venus maintains nearly consistent apparent brightness to our unaided eyes, for most of the interval, diminishing slightly during early August.

In the notes that follow, the position of the planet is noted compared to the background stars. Use the chart above to look for Venus each clear morning. A binocular is helpful.  Unless noted, each observation is for one hour before sunrise.

The month begins with Venus above the V shape. About an hour before sunrise, brilliant Venus is low in the east-northeast.  It is to the upper right of Delta 1 Tauri. (See the chart above.) Use a binocular to see the starfield with Venus.  During the early days of the month, Venus moves closer to Delta 1.  Venus passes the star on July 4.

On July 6, Venus is inside the “V.” 

Beginning July 7, Venus is near Delta 2 Tauri.  Note that Venus is along a line that includes Aldebaran, Delta1 and Delta 2.

On July 10 and July 11, notice that Venus passes between Aldebaran and Epsilon Tauri. 

Venus passes to the upper left of Aldebaran on July 12.

On July 14, Jupiter is at opposition.  Our planet Earth is between the Giant Planet and the sun.  Jupiter and the sun are in opposite parts of the sky.  Jupiter rises in the southeast at sunset, appears to move across the sky during the night, and sets in the southeast at sunrise. While Venus is in the east-northeast, Jupiter, along with Saturn, is in the southwest.

 

Venus and the moon, July 17, 2020
2020, July 17: The moon appears 3.2° from Venus. The brilliant planet is 3.2° from Aldebaran.

The moon joins the scene on July 17.  In the crescent phase, the moon is 26.1 days past its New phase and is only 12% illuminated.  The lunar crescent and Aldebaran are about the same distance from Venus.  The moon is the left of Venus while Aldebaran is to the upper right.  This is a photographer’s opportunity to capture a classic artist’s scene of the moon and Venus in the sky.

This date also marks the last morning of Venus’ interval of greatest brightness.  The planet continues to sparkle in the morning sky, but just not as bright as the past several mornings.

Start looking for the five naked eye planets with the crescent moon. The optimal view is on the morning of July 19.

See the moon and 5 planets, July 19, 2020
2020, July 19: Forty-five minutes before sunrise, see the five naked eye planets with the crescent moon.

This is the optimal morning to see five planets and the lunar crescent.  Forty-five minutes before sunrise, Mercury is low in the east-northeast. The moon is to the speedy planet’s left.  Brilliant Venus is near Aldebaran in the east.  Reddish Mars is in the south-southeast.  Jupiter and Saturn are low in the southwest.  For those wanting more details see the daily note that follows:

  • July 19: Forty-five minutes before sunrise, see the five naked eye planets with the crescent moon. Brilliant Venus is 21° up in the east, 4.5° to the lower left of Aldebaran. The moon (28.1d, 2%) is about 5° up in the east-northeast, 5.0° to the left of Mercury (m = 0.8). The Venus – moon gap is 27°. Mars is over 47° in altitude in the south-southeast. Jupiter – five days past its opposition – and Saturn, one day before its opposition, are in the southwest. Jupiter is about 4° in altitude and Saturn is 7.0° to Jupiter’s upper left. The gap between the moon and Jupiter is over 170° of ecliptic longitude. Dimmer Uranus, Neptune, and Pluto are scattered along the ecliptic between Venus and Jupiter. During the next few mornings five planets are visible – along with Uranus, Neptune and Pluto with optical assistance – but without the moon. Additionally, Jupiter is quickly leaving the sky. On successive mornings, look 3-4 minutes earlier each day. You may catch all of them in the sky until about July 25. Find clear horizons to view Mercury, Saturn, and Jupiter.

On July 20, Venus gleams in the eastern morning sky.  Start looking for Betelgeuse low in the eastern sky, to the left of the east mark. Venus is high above the star. Orion’s other shoulder, Bellatrix is higher in the east. During the next week, begin looking for Rigel, low in the sky, about 15° to the right of the east cardinal point. To view these stars, find a clear horizon. Saturn is at opposition, nearly 14° up in the southwest at this time interval. It is 7.0° to the upper left of bright Jupiter. This evening, Saturn rises at sunset, crosses the meridian around local midnight, and sets at sunrise tomorrow morning.

Venus passes Zeti Tauri
Venus moves in and passes Zeta Tauri.

Late in the month Venus begins to approach the Zeta Tauri, the Southern Horn of Taurus  The closest approach occurs on August 2.

Next, Venus moves into Gemini

 

Astronomy, Sky Watching

2020, June 3: Venus at Inferior Conjunction

 

Transit of Venus, 2012
2012, June 5: Venus passes between Earth and the sun. It was observed to make a rare solar transit. The dark circle in front of the sun is the planet Venus.  This occurred at the inferior conjunction of Venus.

by Jeffrey L. Hunt

At inferior conjunction, faster moving Venus moves between Earth and the sun. It rapidly moves into the morning sky. Because Venus’ orbit is tilted slightly compared to the sun, it does not pass directly in front of the sun. At this inferior conjunction, Venus is about 0.5° above the sun. In 2012, Venus passed precisely between the earth and sun as is seen in the image above. The dark circle is the planet Venus.

Venus at inferior conjunction, June 3, 2020
2020, June 3: Venus passes between Earth and Sun – inferior conjunction – and begins to move into the morning sky when it rises before sunrise.

At this inferior conjunction on June 3, 2020, Venus is 26.8 million miles away; that’s about 111 times farther away than the moon. At this time, Venus is 67 million miles from the sun, about at its average solar distance. When we see the sun in the south, our clocks read noon. The opposite direction is midnight. We do not see the sun in the sky at midnight, and Venus does not appear in that direction.

The line then divides the morning sky from the evening sky. Venus is moving toward the morning section of the diagram as it revolves around the sun faster than Earth. It passes our planet and moves away.

See more about Venus as a Morning Star in 2020-2021.