Category: Astronomy

2020, August 4: Jupiter, Saturn Bright Evening Stars

 

Jupiter and Saturn, August 4, 2020
2020, August 4: About 70 minutes after sunset, Jupiter is 0.8° to the lower right of 50 Sagittarii (50 Sgr) and 3.6° to the lower left of Pi Sagittarii (π Sgr). Meanwhile, Saturn is 2.8° to the lower left of 56 Sagittarii (56 Sgr).

Look for bright Jupiter and Saturn in the southeast during the hours following sunset.

by Jeffrey L. Hunt

Jupiter and Saturn are low in the southeastern sky during the hours following sunset. They appear as overly bright stars.  Jupiter is to the upper right of dimmer Saturn. This evening they are 7.8° apart.  The pair continues to retrograde in eastern Sagittarius as the gap between them grows. 

Retrograde is an illusion that appears when Earth overtakes, passes, and moves away from planets that revolve around the sun farther from our central star than our home planet.  Normally, planets appear to move eastward when compared to the starry background.  While they rise in the east and set in the west during a 24-hour period from Earth’s rotation, these planets seem to move eastward compared to the stars. This occurs because of the mutual revolution of Earth and the planets around the sun.

Earth passed Jupiter on July 13 and Saturn a week later.  This giant planet duo retrogrades until next month.  When they resume their eastward motion, Jupiter overtakes and passes Saturn on December 21, 2020 in what is known as a Great Conjunction.

Jupiter revolves around the sun in 11.8 years and Saturn in 29.5 years.  Jupiter overtakes and passes Saturn in our sky every 19.6 years.  While the great conjunction is not rare, it occurs at intervals of once every generation.  This year’s conjunction is the closest passing of the two planets since 1623.

Each night at the same hour Jupiter and Saturn are farther westward in the sky.  The December conjunction occurs in the southwest sky.

If you’re up early enough tomorrow morning, catch Jupiter and Saturn before they set at 4 a.m.  At that hour bright Mars is in the southeast and brilliant Venus is in the east.

Here is a daily summary about the planets during August.

2020, August 11-12: Peak Perseid Meteors

Meteor Shower
During a meteor shower, shooting stars seem to originate from one spot in the sky. (NASA Photo)

The Perseid Meteor shower peaks on the night of August 11-12, but it is dimmed by a thick waning crescent moon. Even with the moon’s presence, bright meteors are visible.

by Jeffrey L. Hunt

The Perseid Meteor Shower is long-considered the best shower of the year observed from the northern hemisphere.  Other showers may have higher rates, but warm weather and the high elevation of the shower’s radiant before sunrise, as seen from mid-northern latitudes, promises good views.

Perseus is low in the northeast as the sky darkens after sunset.  It is between the bright star Capella and the “W” of Cassiopeia. As the night progresses the constellation and the radiant rise higher into the sky. As morning twilight begins, about two hours before sunrise, Perseus is about two-thirds of the way up in the sky above the northeast horizon.

The shower is from the dust and debris that was liberated by the sun’s energy from Comet Swift-Tuttle (officially known as 109P/Comet Swift-Tuttle). These dabs revolve around the sun, like the planets, but they are scattered along the highly-elongated comet orbit.  Each August, our planet passes through the tiny fragments as they revolve around the sun. High in the sky, the particles vaporize and leave a flash of light in the sky – a shooting star, a meteor.  Like driving through a snowstorm, the meteors emerge from a single point in the sky and the are visible anywhere in the sky.

Unlike random (sporadic) meteors, the Perseids can be traced back to their spot of their origin (radiant).  When you see a possible Perseid, literally follow the trail in the opposite direction.  If it points to Perseus, then it’s likely from the shower.  Sporadic meteors originate from anywhere in the sky.

Official rates of the shower range to 100 meteors per hour when the radiant is highest in the sky.  It is not possible for a single observer to see one meteor or so every minute. A single human’s eyes do not have a large enough field of vision to see the entire sky, and humans have a brightness perception limit.  So, the projected rate is 100 meteors per hour across the entire sky at all brightness levels, even those beyond human perception.  To watch the entire sky, five observers are needed, one to look above each cardinal direction and a fifth to look overhead.

Two other factors play a role: On the peak morning, the moon’s phase is 43% illuminated, bright enough to cast shadows on the ground. The moon is brighter on the days leading up to August 12. This reduces the number by 30% or more.  City lights reduces the number by 50%. So, in the city, about 35 meteors per hour might be visible.  Divide that number by the five observers need to monitor the sky.  A single observer, in town might see 6-7 meteors per hour, perhaps double that in a dark location. This is worth the look, but patience is needed to see several Perseid meteors.

In these days of social distancing, a quintet of observers separated in a backyard, provides interesting meteor observing, but likely before you know it somebody will be snoring!

2020, August 4: Four Morning Planets, Bright Moon

Venus, Mars, Saturn, and Jupiter shine from the morning sky.  The morning planet parade breaks apart.

by Jeffrey L. Hunt

About two hours before sunrise, brilliant Venus gleams from the eastern sky.  It is near the Southern Horn of Taurus the Bull, known as Zeta Tauri (ζ Tau on the photo). 

For over a month, Venus has been moving eastward in Taurus.  Tomorrow, Venus moves into the club region of Orion.  Bellatrix, a shoulder of Orion, is visible in the photo above.

Mars in Pisces, August 4, 2020
2020, August 4: Shining from the dim stars of Pisces, Mars is is 0.3° to the upper left of 89 Piscium (89 Psc on the photo) and 3.7° to the lower right of Zeta Piscium (ζ Psc).

About an hour earlier, with a bright moon in the sky and only four hours past its official Full phase, Mars shines from the dim starfield of Pisces. It continues to march eastward along the solar system’s plane.  Use a binocular to track Mars through the starfield, especially with the bright moon in the sky for the next several mornings.

Next month, the Red Planet starts to retrograde.  Mars appears to move westward compared to the stars.  On October 13, 2020, Earth passes between the planet and the sun.  Mars and the sun are in opposite directions from Earth.  This is known as opposition.  The planet rises in the east at sunset and sets in the west at sunrise.  Around opposition, Mars is closest to Earth and appears at its brightest.  This occurs a week before opposition.

This morning Mars is 0.3° to the upper left of 89 Piscium (89 Psc on the photo) and 3.7° to the lower right of Zeta Piscium (ζ Psc).

Jupiter and Saturn, August 4, 2020
2020, August 4: Appearing low in the southwest, Jupiter and Saturn are disappearing from the early morning sky. This morning, Saturn is 7.8° to the upper left of Jupiter.

Jupiter and Saturn are appearing very low in the sky at this hour.  Better views occur when the planets are in the evening sky.  Ninety minutes after sunset, they are shining from low in the southeastern sky,

Both planets are retrograding in eastern Sagittarius.  They reverse their courses next month.  As the year closes, Jupiter passes Saturn on December 21, 2020, in a Great Conjunction.

Here is a daily summary about the planets during August.

 

2020, August 15: Moon, Venus Pair, Artistic Sight in Morning Sky

(In the image above, 2020, July 17: The crescent moon, Brilliant Venus, and Aldebaran shine from the eastern during early morning twilight.)

Venus and the moon make a spectacular scene before sunrise on August 15.  Artists and photographers can create inspiring interpretations of the view.

by Jeffrey L. Hunt

Venus sparkles in the eastern sky before sunrise during the summer and autumn months.  During the moon’s monthly journey, it moves past this brilliant planet.  During August, the moon makes a close pass with Venus, creating the inspiring scene.  From North America, the thin lunar crescent, that is about 15% illuminated, is 3.6° to the upper left of the brilliant planet.

Venus and Moon, August 15, 2020
August 15: The crescent moon is 3.5° to the upper left of Venus.

At mid-northern latitudes on August 15, Venus rises over three hours before sunrise.  By an hour later, the Venus – Moon pair is over 15° in altitude in the eastern sky.  Early risers may have to find a spot away from trees, houses, and other obstructions to see Venus and the moon in the eastern sky.

As the morning progresses and the sky brightens, Venus and the moon rise higher in the sky.

Crescent Moon, Venus, Aldebaran, July 17, 2020
2020, July 17: The crescent moon, Venus, and Aldebaran in the eastern sky before sunrise.

Each stage of morning twilight presents spectacular views of the celestial pair shining in the eastern sky and varying opportunities to capture the view with a camera.

The pair can be photographed with cameras that have time exposure settings.  Exposures can range from fractions of a second through a few seconds.  By varying the exposure times, a suitable image can be captured.

The longer the exposure, the more the moon’s nighttime side appears in the photo.  This gentle illumination known as “Earthshine,” is from sunlight reflected from Earth’s clouds, continents, and oceans.  It softly illuminates the night portion of the moon.

The waning crescent moon, July 14, 2020.
2020, July 14: The moon is in the eastern sky. It is 23.4 days past its New phase and 37% illuminated. It is a thick waning crescent phase.

At some lunar phases the sunlight reflected from the moon illuminates Earth’s terrestrial features.  This is bright enough to create shadows on the ground.

The moon and Venus may be visible after sunrise and well into the morning.

Coincidentally, the Venus – Moon grouping occurs at the same time that Sirius is making its first appearance in the morning sky before sunrise.  About 45 minutes before sunrise, Sirius is above the horizon in the east-southeast.

On September 14, the moon passes Venus again, but the moon is farther away and the pair is lower in the sky.

The August 15 grouping of Venus and the crescent moon is the best grouping during Venus’ current appearance in the morning sky, because the two are visible together for over 3 hours before sunrise.

For more about the sky in August, click here.

(Photos and charts by the author.)

 

2020, July 28: Jupiter and Saturn Lead July’s Morning Planet Parade

Jupiter and Saturn, July 28, 2020
2020, July 28: Jupiter is 0.6° to the left of 50 Sagittarii (50 Sgr), while Saturn is 3.3° to the upper left of 56 Sagittarii (56 Sgr).

Jupiter and Saturn lead Mars and Venus during late July’s morning planet parade.

by Jeffrey L. Hunt

Four planets – Jupiter, Saturn, Mars, and Venus – are strung along an arc in the morning sky.  They appear along the solar system’s plane that astronomers call the ecliptic. During the pre-sunrise hours of late July, the imaginary line stretches from the southwest skyline to the east-northeast horizon.

Bright Jupiter and Saturn are low in the southwest in front of the stars of eastern Sagittarius.  They are moving westward – retrograding – compared to the starry background.  While they rise in the east before sunset and appear low in the southeast during evening hours from Earth’s rotation, they are moving westward compared to the distant stars.  This westward movement compared to the stars is an illusion when Earth overtakes, passes, and moves away from them.

Jupiter and Saturn are 7.5° apart.  In another month, they are about another degree apart. 

In September, Jupiter and Saturn begin moving eastward again.  Jupiter inches toward Saturn and passes it in a Great Conjunction, December 21, 2020.  This is the closest conjunction of the two planets since 1623.  A Jupiter – Saturn conjunction occurs every 19.6 years.

Through a binocular check their positions each clear morning compared to the stars.  Jupiter is 0.6° to the left of 50 Sagittarii (50 Sgr), while Saturn is 3.3° to the upper left of 56 Sagittarii (56 Sgr).  Watch Jupiter pass 50 Sgr and Saturn approach 56 Sgr.

Mars in Pisces, July 28, 2020
2020, July 28: Mars is 5.1° to the upper left of 20 Ceti (20 Cet) and 5.0° below Epsilon Piscium (ε Psc).

Farther east, Mars is that “bright star” in the southeast.  It is among the dim stars of Pisces.  On the photo above, it is moving into the starfield where it retrogrades and passes opposition (October 13, 2020).  This morning the Red Planet is 5.1° to the upper left of 20 Ceti (20 Cet) and 5.0° below Epsilon Piscium (ε Psc).  As with Jupiter and Saturn, watch Mars move eastward in the starfield through a binocular.

Venus in Taurus, July 28, 2020
2020, July 28: Venus, in the constellation Taurus, is 4.3° to the upper right of Zeta Tauri (ζ Tau), the Southern Horn of the Bull.

The brilliant Morning Star Venus is in the eastern sky.  It is moving eastward among the stars of Taurus.  This morning it is 4.3° to the upper right of Zeta Tauri (ζ Tau), the Southern Horn of the Bull.  The bright star Aldebaran, the Bull’s Eye, and two star clusters (Hyades and Pleiades) appear above the bright planet.

Here are two daily summaries about the planets during July and August.

2020, July 26: A Morning Planetary Quartet

Jupiter and Saturn. July 26, 2020
2020, July 26: Bright Jupiter and Saturn are in the southwest during morning hours, they are 7.3° apart. Jupiter is 0.7° to the left of 50 Sagittarii (50 Sgr). Saturn is 3.4° to the upper left of 56 Sagittarii (56 Sgr). Jupiter’s moon Ganymede is visible.

Four bright morning planets – Venus, Mars, Saturn, and Jupiter – span the sky.

by Jeffrey L. Hunt

Four bright planets – Venus, Mars, Saturn, and Jupiter – span the morning sky from the east-northeast horizon to the southwest skyline.

During the predawn hours, bright Jupiter and Saturn are in the southwest.  They appear among the stars of eastern Sagittarius. These giant planets are 7.3° apart.  Look at Jupiter with a binocular.  It’s possible to see some of its four bright Galilean moons, first observed in Galileo’s telescope during the 17th century.  This morning Ganymede is visible in the photo above.

Jupiter passes Saturn in a Great Conjunction on December 21, 2020.

Look for Jupiter and Saturn in the southeast about an hour after sunset, as they clear the local trees, houses, and buildings.  During the night, they appear to move westward.

Mars is Cetus, July 26, 2020.
2020, July 26: Mars, high in the southeast, is 4.3° to the upper left of 20 Ceti (20 Cet) and 5.3° to the lower right of Epsilon Piscium (ε Psc).

During the morning hours, Mars is high in the southeast, among the stars of Cetus.  Tomorrow it moves into Pisces.  The stars identified on the accompanying photo show the dim star field where the Red Planet passes opposition, October 13, 2020.

Venus in east, July 26, 2020.
2020, July 26: In Taurus, brilliant Venus is morning eastward toward Zeta Tauri (ζ Tau). This morning Venus is 5.8° to the upper right of the star.

Brilliant Venus is in the eastern sky.  It is in front of the stars of Taurus the Bull.  Watch it move toward and pass Zeta Tauri (ζ Tau), the Southern Horn of the Bull, on the photo, during the next several mornings.  This morning Venus is 5.8° to the upper right of the star.

Notice that Aldebaran and the Hyades star cluster make a sideways “V” that represents the head of the Bull.  The Pleiades star cluster is higher in the sky, and is said to be riding on the Bull’s back.

Here are more about the planets during July and August.

2020, July 25: Morning Star Venus Moves Eastward in Taurus

Venus in Taurus, July 25, 2020.
2020, July 25: Venus in Taurus. The planet continues to move eastward among the stars. It is moving toward ζ Tau. This morning it is 6.5° to the upper right of ζ Tau and 8.6° to the lower left of Aldebaran.

Brilliant Venus shines brightly this morning among the stars of Taurus the Bull.

by Jeffrey L. Hunt

Brilliant Venus shines from the eastern sky this morning in front of the stars of Taurus the Bull. It appears 8.6° to the lower left of Aldebaran and 6.5° to the upper right of Zeta Tauri (ζ Tau on the photo above), the Southern Horn of Taurus.  Venus continues to move eastward during the remainder of July as it nears ζ Tau.

Rosy Aldebaran and the Hyades star cluster form a sideways “V” to represent the head of the Bull to the upper right of Venus  The single bright star represents the creature’s eye. Aldebaran is about 125 times brighter than the sun and 40 times our central star’s diameter. 

The Hyades is a well-studied “galactic” star cluster; that is, the cluster is part of the plane of the Milky Way galaxy, like the sun and solar system, but unlike the globular clusters that revolve around a galactic halo. The Hyades has over 125 members that are heading in space toward a spot near the star Betelgeuse.

The famous Pleiades star cluster (known to school children as the “Seven Sisters”) is above Aldebaran and the Hyades. To the unaided eye, six or seven stars are visible.  Through a binocular, more than a dozen stars can be seen.  In the photo above, nearly two dozen stars are visible.  Detailed studies count over 200 stars in this cluster.

Astronomers think that stars are formed in clumps, somewhat like bunches of grapes.  The mutual gravitational pull of the stars though is too weak to keep the clusters together.  Over time, stars escape, decreasing the mutual gravitation attraction.

 

The Pleiades cluster is thought to be younger than the Hyades.  The Pleiades cluster’s bright blue stars have short astronomical lives.  The cluster is thought to be about 100 million years old while the Hyades could be six times older.

On these warm clear mornings of summer explore Taurus and its star clusters with a binocular.  Each morning, notice the location of Venus within the constellation.

 

2020, July 24: Jupiter, Saturn, Mars, Morning Planetary Motion

Jupiter and Saturn in Sagittarius, July 24, 2020
2020, July 24: Bright Jupiter and Saturn appear in the southwest in the hours before bright morning twilight brightens the sky. This morning Jupiter is 0.9° to the left of the star 50 Sagittarii (50 Sgr on the photo above) and 4.8° to the upper left of Pi Sagittarii (π Sgr). Saturn is 3.5° to the upper left of 56 Sgr and 4.6° to the lower right of σ Cap.

Three bright planets – Jupiter, Mars, and Saturn – shine from the southern skies during the overnight hours.

by Jeffrey L. Hunt

Jupiter and Saturn rise into the southeastern sky as the sky darkens each evening.  Mars rises before midnight, and it is higher in the sky after midnight.

By 3 a.m. Jupiter and Saturn are in the southwest and Mars is high in the southeast.

Bright Jupiter and Saturn are near each other, 7.3° apart.  In the photo above, Jupiter and Saturn are in eastern Sagittarius.  The stars of the distant constellation form the backdrop for the moving planets.

Normally, the planets move eastward compared to the starry background.  About each year, our faster moving planet approaches Jupiter and Saturn. These planets appear to stop moving eastward and begin to move westward compared to the stars.  This is known as retrograde motion.  Earth then passes between Jupiter and the sun, then Saturn and the sun.  This is known as opposition.  As Earth moves away the planets continue to appear to move backwards, then they start their forward motion again.

For now, Jupiter and Saturn are retrograding, and Jupiter is getting farther from Saturn.  By the end of August, Jupiter is about 1° farther away from Saturn than it is this morning.  One degree is about the apparent size of two full moons.

Jupiter’s retrograde ends September 12. Even as Jupiter resumes its eastward motion, Saturn continues to retrograde.  Saturn’s retrograde ends September 28.  Jupiter then closes in on Saturn for a Great Conjunction, December 21, 2020.

Use a binocular to watch the planets move against the stars. This morning Jupiter is 0.9° to the left of the star 50 Sagittarii (50 Sgr on the photo above) and 4.8° to the upper left of Pi Sagittarii (π Sgr).  Observe that Jupiter passes 50 Sgr and moves closer to π Sgr during the next month.

Meanwhile, Saturn’s retrograde puts it 3.5° to the upper left of 56 Sagittarii (56 Sgr) and 4.6° to the lower right of Sigma Capricorni (σ Cap).  The Ringed Wonder appears to move closer to 56 Sgr and farther from σ Cap during the next month.

Mars in Cetus, July 24, 2020
2020, July: Bright Mars in the southeast among the stars of Cetus near the Pisces-Cetus border. This morning Mars is 5.6° to the lower right of ε Psc, and 3.6° to the upper left of 20 Cet.

Farther east, Mars is marching eastward, over halfway up in the southeast at this hour.  The Red Planet is in front of the stars of Cetus.  In three mornings, it moves back into Pisces.

About every two years, Earth approaches and passes between the sun and Mars.  This year opposition occurs on October 13, 2020. Mars begins to retrograde on September 9, 2020.  The planet is moving eastward, but its eastward progress slows in about three weeks.

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).  Including Epsilon Piscium (ε Psc) and Delta Piscium (δ Psc), Mars’ motion during the next month is within the dim starfield displayed on the photo.

This morning Mars is 5.6° to the lower right of ε Psc, and 3.6° to the upper left of 20 Cet.  Each clear morning, observe Mars’ place among the stars with binocular.

Here’s more about the planets during July.

2020, July 24: Morning Star Venus, Mercury in Eastern Sky

 

Venus and Mercury, July 24, 2020
2020, July 24: Mercury and Venus shine from the eastern sky this morning about an hour before sunrise. Mercury is 24° to the lower left of brilliant Venus.

Before sunrise catch the two planets inside Earth’s orbit, Mercury and Venus, the eastern sky.

by Jeffrey L. Hunt

Brilliant Venus and Mercury shine this morning from the eastern sky about an hour before sunrise.  These two worlds are part of the morning planet parade that is now breaking up.  Mercury, in the east-northeast, and Jupiter, low in the southwest, are near the horizon.  Venus, Mars, and Saturn are scattered between the other two naked-eye planets.

Mercury, July 24, 2020
2020, July 24: Mercury is low in the east-northeast about one hour before sunrise.

This morning Venus and Mercury are 24° apart.  As the images above indicate, locate a clear horizon to find this elusive planet.

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.