Category: Jeffsfavs

Summer’s Celestial Scorpion

The Celestial Scorpion glides across the southern sky during summer.

by Jeffrey L. Hunt

Scorpius crawls across the southern sky during July from the mid-northern latitudes.  Look low in the southern sky for rosy Antares, the Scorpion’s heart.  The body, tail and stinger resemble a fishhook or letter “J” as they curve toward the horizon and back up into the sky.

Antares is classified as a supergiant star.  It is very larger than our sun, but it is not as hot as our central star’s 10,000°F surface temperature. 

Unlike the artist’s conception of color and temperature, bluer stars are hotter than redder stars.  Our sun is yellow-white and considered an average star in size and temperature.

The classic pincers of the celestial arachnid are marked by Zubenelgenubi (the southern claw) and Zubeneschamali (the northern claw).  They are part of Libra in today’s division of constellations.

When looking toward this region of the sky, we are generally looking in the direction of the galaxy’s center.  Star clouds, gas clouds, and dusty regions are visible here.  Scan across the southern sky and higher in the sky.  Many fascinating features are here.

On the chart above, the spot labelled M4 is a star cluster to the right (west) of Antares. Through a binocular or small telescope, the cluster looks like a small cotton ball.  In a dark location, the cluster is visible to the unaided eye.

 The catalog of celestial objects was first assembled by Charles Messier, an 18th century French astronomer who cataloged star clusters and gas clouds as he searched for comets.  Today, many amateur astronomers seek out the over 100 objects in Messier’s list. The Astronomical League awards star gazers an award for observing the entire register of interesting celestial objects.

Two additional “M objects, “ M6 and M7, are visible.  This star cluster pair is unlike the globular cluster of M4. They resemble tiny jewels scattered across the dark velvet of the sky.

This region of the sky is best viewed when the moon is in a crescent phase or absent from the sky.

On the next clear, moonless evening, take a look southward for the Celestial Scorpion and is wonders.

2020, July 23: 5 Planets, Last Call

Mercury, Venus, July 23, 2020
2020, July 23: Venus and Mercury shine from the eastern sky during bright morning twilight. Mercury is nearly 24° to the lower left of Venus.

Five planets – Mercury, Venus, Mars, Jupiter, and Saturn – are visible together before the morning planet parade begins to break up.

by Jeffrey L. Hunt

Five planets arch across the clear sky this morning.  For the next few mornings during twilight and before Jupiter sets, view five planets that span the sky from the east-northeast skyline to the southwest horizon.

Jupiter and Saturn, July 23, 2020
2020, July 23: Jupiter is 7.2° to the lower right of Saturn. Jupiter is 1.0° to the upper left of 50 Sagittarii (50 Sgr, m = 5.6), while Saturn is 4.5° to the lower right of Sigma Capricorni (σ Cap, m = 5.2).

Bright Jupiter and Saturn are in the southwest among the stars of eastern Sagittarius.  They are retrograding – moving west – compared to the starry background.  This is an illusion as our planet moves away from this giant planet pair.  They continue to retrograde until September.  This morning the Jupiter – Saturn gap is 7.2°.  The planets continue to separate until their retrograde motion ends.

During the fall months, Jupiter inches up and catches the Ringed Wonder on December 21, 2020 for a Great Conjunction.  This is the closest conjunction of the two planets since 1623.

Jupiter and Saturn are visible in the southeast as the sky darkens each evening.  Use a binocular to watch them continue to move westward compared to the stars identified in the photo above.  The stars, with their astronomical names Sigma Capricorni (σ Cap on the photo), 56 Sagittarii (56 Sgr), 50 Sagittarii (50 Sgr) and Pi Sagittarii (π Sgr), make the background to watch the planets.  During the next month, the planet pair is lower in the southwestern sky during early morning hours and higher in the eastern sky during evening hours.

In the photo above three of Jupiter’s four largest satellites are visible.  They can be seen with a binocular, depending on their positions when they are viewed.

Mars in Cetus, July 23, 2020
2020, July 23: Mars, in the southeastern sky, moves eastward among the stars of Cetus. It is 3.1° to the upper left of 20 Ceti (20 Cet, m = 4.8). It is moving eastward toward the region of Pisces where its retrograde motion begins.

Mars is farther east, over halfway up in the southeast among the stars of the constellation Cetus.  Mars is well passed 20 Ceti (20 Cet on the photo) and heading toward a starfield in Pisces that includes Zeta Piscium (ζ Psc on the photo), 89 Piscium (89 Psc), Mu Piscium (μ Psc), Nu Piscium (ν Psc), and Omicron Piscium (ο Psc).

Mars begins its retrograde motion during early September near the stars on the left side of the starfield in the photo.  Use a binocular to watch the Red Planet move toward them during the next few weeks.  The planet rises at about 11:30 p.m. local time and its easier to see in the east an hour later.

Venus and Taurus, July 23, 2020
2020, July 23: Brilliant Venus, among the stars of Taurus, is 7.3° to the lower left of Aldebaran. The Hyades star cluster and Pleiades star cluster appear nearby.

Meanwhile in the eastern sky, brilliant Venus is in Taurus, 7.3° to the lower left of Aldebaran, the constellation’s brightest star.  The planet continues moving eastward and away from Aldebaran.

Together, Aldebaran and the Hyades star cluster make a “V” shape, sideways when it is in the eastern sky, to identify the head of the Bull.  The Pleiades star cluster, higher in the sky, is riding on the Bull’s back.

Elusive Mercury comes into view as Jupiter is low in the southwest.  It is to the lower left of Venus in the brighter glow of morning twilight.

In a few mornings, Jupiter sets before Mercury comes into full view, leaving four planets.  Look early enough in the morning to see Jupiter, Saturn, Mars, and Venus.  A view later during brighter morning twilight provides a view of Saturn, Mars, Venus, and Mercury.

Here’s more about the planets during July.

 

2020, July 20: One Morning, Five Planets

Mercury and Venus, July 20, 2020
2020, July 20: Venus and Mercury shines from the eastern sky. Mercury is over 23° to the lower left of the brilliant planet.

The five bright planets – Mercury, Venus, Mars, Saturn, and Jupiter – are strung across the plane of the solar system from the east-northeast horizon to the southwest skyline.  Simultaneously, five planets are visible.

Update:  The planets on July 23, click here.

by Jeffrey L. Hunt

This morning the five bright planets appear as beads on a necklace that is stretched across the morning sky.

Mercury, July 20, 2020
2020, July 20: Without the moon this morning, Mercury shines from low in the east-northeast during morning twilight. It is over 23° to the lower left of brilliant Venus.

Without the moon, Mercury shines low in the east-northeast, to the lower left of brilliant Venus.  Mercury is in the sky for several more mornings until it disappears back into the sun’s glare.  In two mornings it reaches its greatest separation (elongation) from the sun.  It never strays far from the sun’s glare, making it a challenge to view.

Venus in Taurus, July 20, 2020.
2020, July 20: In the east, brilliant Venus shines from among the stars of Taurus, 5.1° to the lower left of the star Aldebaran. The Hyades star cluster and Pleiades star cluster are nearby.

Brilliant Venus is to the upper right of Mercury.  Before later twilight brightened the sky, Venus is visible 5.1° to the lower left of Aldebaran.  This star along with the Hyades star cluster form the face of Taurus the Bull.  The Pleiades star cluster is above the scene.

Mars in Cetus, July 20, 2020
2020, July 20: Mars shines from the stars of Cetus in the southeastern sky during early morning twilight. It is 2.7° to the upper left of 20 Ceti (20 Cet).

Meanwhile, Mars is the lone bright “star” in the southeast among the dim stars of Cetus.  This morning it is 2.7° to the upper left of 20 Ceti (20 Cet on the photo). A binocular is needed to see the starfield.

Mars is marching eastward.  It begins the illusion of retrograde motion in early September as Earth approaches and passes the planet.  Earth is between the sun and Mars on October 13, 2020.  On this date, the sun and planet are in opposite directions from Earth.  Near opposition the outer planets are closest to Earth and brightest in the sky.

Jupiter and Saturn in the southwest, July 20, 2020
2020, July 20: Saturn and brighter Jupiter appear in the southwest among the stars of Sagittarius. Jupiter is 4.0° to the lower right 56 Sagittarii (56 Sgr), while Saturn is 4.3° to the lower right of Sigma Capricorni (σ Cap).

Saturn and Jupiter are farther west in eastern Sagittarius.  The planets are retrograding – moving westward compared to the background stars. With a binocular check the planets’ positions compared to the starry background.  This morning Saturn is 4.3° to the lower right of Sigma Capricorni (σ Cap), while Jupiter is 4.0° to the lower right 56 Sagittarii (56 Sgr).

Jupiter was at opposition last week and Saturn is at opposition today.  Jupiter and Saturn appear to reverse their directions in September.  Then Jupiter inches toward Saturn and passes it on December 21, 2020 for a Great Conjunction.

Continue to look for the five planets for the next several days.

Here’s more about the planets during July.

 

2020, July 17: Spectacular Crescent Moon in Morning Planet Parade

The crescent moon, Venus, Aldebaran and the Pleiades, July 17, 2020.
2020, July 17: The crescent moon is in a group with Venus and Aldebaran as the Pleiades appear above the scene during early morning twilight.

This morning’s crescent moon joins Venus in the eastern sky.  Four planets arch across the morning sky.

by Jeffrey L. Hunt

Venus, the crescent moon, and Aldebaran, July 17, 2020.
2020, July 17: The crescent moon is 3.2° to the left of Venus and the brilliant planet is the same distance to the lower left of Aldebaran.

A thin crescent moon joins brilliant Venus this morning in the eastern sky.  The star Aldebaran, in Taurus the Bull, appears nearby.  The moon is 3.2° from Venus, and the sparkling planet is the same distance from Aldebaran.

Mars in Cetus, July 17, 2020.
2020, July 17: Mars, in the southeast, is 2.9° to the upper right of 20 Ceti (20 Cet).

Higher in the southeast, bright Mars shines from the dim stars of Cetus.  It continues to march eastward compared to the starry background.  This morning it is 2.9° to the upper right of 20 Ceti (20 Cet on the photo).

Earth passes between Mars and the sun on October 13.  This is known as opposition.

Jupiter and Saturn in eastern Sagittarius, july 17, 2020.
2020, July 17: Jupiter is 3.7° to the lower right of 56 Sagittarii (56 Sgr) and 1.6° to the upper left of 50 Sagittarii (50 Sgr). Saturn is 4.1° to the lower right of Sigma Capricorni (σ Cap).

Jupiter and Saturn are in the southwestern sky in front of the stars of eastern Sagittarius.  They are moving westward compared to the stars.  This illusion of backwards motion occurs when Earth passes worlds beyond our planet.

Jupiter is a few days past its opposition. Earth passes between the sun and Saturn on July 20.  Both planets continue to retrograde until September.  When they again resume their eastward motion compared to the stars, Jupiter approaches and passes Saturn in a Great Conjunction on December 21, 2020.

This morning, Jupiter is 3.7° to the lower right of 56 Sagittarii (56 Sgr) and 1.6° to the upper left of 50 Sagittarii (50 Sgr).  Saturn is 4.1° to the lower right of Sigma Capricorni (σ Cap).

Here’s more about the planets during July.

 

2020, June 30: The Classic Scorpion Catches the Moon

The moon and the pincers of the scorpion, June 30, 2020.
2020: June 30: The gibbous moon appears 2.7° above Zubenelgenubi in the early evening sky

by Jeffrey L. Hunt

As the moon moves toward its Full phase, the Classic Scorpion catches the lunar orb in its pincers. This evening the moon is 80% illuminated, as it is 9.8 days past the New phase.

One hour after sunset, the moon is caught in the classic pincers of Scorpius.  It is just above (2.7°) the southern claw – Zugenelgenubi. The name reflects that these stars – now part of Libra – were included with Scorpius.  The northern claw – Zubeneschamali – is above the moon.  Because of the moon’s brightness, it might be necessary to block the moon’s light with your hand to see the pincers or look for the stars with a binocular.

The head and body of the scorpion curves down to the left from the moon’s location.  The heart is red-orange Antares.  At this hour, the tail curls below the horizon and back up to the stinger.

2020-2021: Brilliant Planet Venus as a Morning Star

Venus, moon, Sirius, August 14, 2020
2020, August 14, 2020: One day before their close grouping, the crescent moon is 13° to the upper right of Morning Star Venus. Sirius is making its first morning appearance in the east-southeast.

Brilliant Morning Star Venus shines brightly in the morning sky during 2020 and early 2021.

by Jeffrey L. Hunt

Click here for our semi-technical article about the apparition of Venus during 2020-2021.

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Slideshow of Venus images

Articles:

Venus makes a grand entrance into the morning sky after its inferior conjunction on June 3, 2020, at 12:44 p.m. CDT. It races into the morning sky and a week after conjunction it rises at Civil Twilight, 32 minutes before sunrise. After mid-June, Venus gleams from low in the east-northeast sky during mid-twilight. By early July, Venus is at its greatest brightness, rises before the beginning of twilight, and appears higher in the sky as sunrise approaches.

During July, Venus moves through the Hyades, with an Aldebaran conjunction on July 12. Watch the planet move through the star cluster with a binocular, during several mornings leading up to the Venus – Aldebaran conjunction.

On July 19, the lunar crescent and five planets are simultaneously spread across the sky with Jupiter low in the western sky and Mercury low in the eastern sky. Venus, Mars, and Saturn are scattered between them.

During August, Venus leaves Taurus, passes through the club and arm area of Orion and into Gemini. On August 15, see the moon join Venus.

Other highlights of the Venus apparition include a grouping with the Beehive cluster in mid-September that includes the crescent moon on September 14; two mornings in October when Venus is about 0.5° from Regulus; a widely spaced Venus – Spica conjunction during mid-November; and an extremely close conjunction with Beta Scorpii in December. Mercury makes an appearance during November, but the gaps with Venus are very wide. At the end of the apparition, Venus passes Mercury, Saturn, and Jupiter. Although they are near the sun, attempt to view the Venus – Jupiter Epoch (close) Conjunction during the day.

Venus reaches its superior conjunction on March 26, 2021, then slowly moves into the evening sky.

Recent Articles

2020: December 21: The Great Conjunction of Jupiter and Saturn

Jupiter and Saturn, August 12, 2020
2020, August 12: Saturn is 8.1° to the lower left of the Giant Planet. In the starfield, Jupiter is 1.4° to the right of 50 Sagittarii (50 Sgr), while Saturn is 2.4° to the lower left of 56 Sagittarii (56 Sgr).

December 21, 2020: Jupiter passes Saturn in a close conjunction, a once-in-a-generation Great Conjunction. This Jupiter – Saturn conjunction is the closest Great Conjunction since 1623.

Read more about the August 2020 planets.

by Jeffrey L. Hunt

Once a generation, Jupiter catches and passes Saturn. This is known as a Great Conjunction.  Both planets move slowly around the sun because of their distance from our central star.  A Jupiter year is nearly 12 Earth-years long while Saturn revolves around the sun in nearly 30 years.  A Jupiter-Saturn conjunction is rare enough for observers to take notice of this unique pairing.

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See our detailed article about the Great Conjunction here(updated May 28, 2020)

Jupiter takes nearly 20 years to move past Saturn, travel around the sun, and catch Saturn again.  When Jupiter catches Saturn on December 21, 2020, they will be very close, only 0.1° apart!  This is the closest conjunction since the Great Conjunction of July 16, 1623!  The next Great Conjunction is October 31, 2040, when the two planets are 1.1° when they are low in the east-southeast before sunrise.

December 2020

Look low in the southwest, one hour after sunset.  Bright Jupiter is easy to locate.  Dimmer Saturn is nearby, to Jupiter’s upper left.

On December 16, the crescent moon enters the scene. One hour after sunset, the crescent moon (2.3 days past its New phase, 7% illuminated) joins the planets. It is over 6° up in the southwest, about 5° below Jupiter. The Jupiter – Saturn gap is 0.5°.  This is about the apparent diameter of the moon.

Jupiter - Saturn 2020 Great Conjunction

Each night thereafter, Jupiter closes more on Saturn, until conjunction evening when they are 0.1° apart.  This is close enough to see them in through at a telescope’s low power. Here is the detailed note for conjunction evening:

  • December 21: Jupiter – Saturn Great Conjunction! One hour after sunset, Jupiter is about 12° up in the southwest, 0.1° to the lower left of Saturn. They are 30° east of the sun. Both fit into the eyepieces of modest telescopic powers. Jupiter’s Galilean Satellites are nicely lined up along the equatorial plane of the planet. Ganymede, Io, and Calisto are east of Jupiter, and Europa is west of the planet. Titan is nicely placed to the northwest of Saturn. After the conjunction, Jupiter moves eastward along the ecliptic, separating from Saturn. Each evening the planetary pair appears lower in the sky.
Telescope view of Jupiter and Saturn, December 21, 2020
Jupiter and Saturn are close enough to appear together through a telescope’s low power eyepiece. Saturn’s rings and Jupiter’s four brightest and largest moons are visible as well.

Through a telescope with an eyepiece that is in the 50x-60x magnification range, Jupiter and Saturn are visible in the same field.  Saturn’s rings are easy to locate.  Jupiter’s four largest and brightest moons – Io, Europa, Callisto, and Ganymede – are evident as well.  On closer inspection, some of Jupiter’s cloud bands are visible.  Some telescopes invert the view compared to the diagram shown here.  Others flip the image left to right.  So the actual view through a telescope may look differently than what is shown here.

The half-full moon is higher in the south-southeast.  Mars is to the left of the moon, over halfway up in the sky in the southeast.  Four bright solar system objects are in the sky – moon, Jupiter, Mars, and Saturn.

Angular Sizes

Moon image by NASA

When viewing the sky, the actual sizes of objects are difficult to determine because there is no depth perception.  We measure objects by their apparent angular size.  Apparent is how large they seem to our eyes.  Angular size is measured in degrees, like the way a protractor measures angles.  The moon appears to be about 1/2° in diameter.  At the Great Conjunction, Jupiter and Saturn are 0.1° apart.  This seems to be close, but they are easily distinguished from each other.  The image above shows the angular size of the moon and 0.1° of angular size on the moon.  The large circular feature is the largest lunar feature, the Imbrium Basin, easily visible without a binocular or telescope.  So the planets are close together, but they do not appear as a “single star” at the conjunction.

Detailed Motion of Jupiter and Saturn

The image at the top of this article shows a close conjunction of Venus and Jupiter.  Notice the separation of the two planets.  At the 2020 Great Conjunction, Jupiter and Saturn are closer than this August 27, 2016 conjunction.

Jupiter and Saturn, their apparent motion in the sky 2020
2020: The apparent motions of Jupiter and Saturn compared to the background stars.

In 1961, the Jupiter – Saturn conjunction occurred in the morning sky, about 2° below 56 Sagittarii. (Note the star’s location on the accompanying chart, nearly 5° west of the Capricornus – Sagittarius border.) The 2020 conjunction occurs about 6° farther eastward, just east of the constellations’ border.

The chart above shows the motions of the planets against the background stars.  Two apparent motions occur to the Bright Outer Planets – Mars, Jupiter, and Saturn.  As Jupiter and Saturn emerge from their solar conjunctions, early in 2020, they appear higher in the sky when weekly observations are made.  They somewhat match the annual westward march of the stars.  This is caused by the earth’s revolution around the sun.  The stars are a calendar.  Over several human lifetimes, the same star is in the same position at the same time and same date each year.

The second motion is a combination of the planets’ slow orbit around the sun, especially for Jupiter and Saturn, since they don’t appear to move far during a year and Earth.  Jupiter and Saturn appear to move eastward (direct motion) compared to the starry background.  During the next year they are among a faint starfield in eastern Sagittarius and western Capricornus.  As our planet catches up and passes between them and the sun (opposition), they appear to move westward (retrograde motion) compared to the stars — retrograde motion.  After Earth passes them, Jupiter and Saturn seem to resume their direct motion compared to the background that moves farther west and rise earlier as the seasons progress.

Jupiter finally catches Saturn in late December for this Great Conjunction. On the chart, notice that Mars passes Jupiter and Saturn during late March 2020.

Read about the 1623 Jupiter – Saturn Great Conjunction here.

Monthly Summaries of What to Watch

(Bookmark this page to return for monthly updates of the planets’ locations.)

Recent Articles

Mars
The Red Planet from the Mars Global Surveyor shows the effects of a global dust storm (NASA)

2020, August 12: Mars, A Planetary Dance

Mars begins its planetary dance as it nears its closest approach to Earth and its opposition with the sun.