2017, February 12: The Winter Sky

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The Winter Stars gleam brightly from the southern sky this evening.  Orion, with its bright stars, Betelgeuse and Rigel, slowly march westward.  Within the constellation is the Orion Nebula that appears as a fuzzy cloud through a small telescope or binoculars.  Aldebaran appears in front of the Hyades star cluster, that appears in a check mark shape or a letter “V” if you include the bright star.  The Pleiades star cluster is to the upper right of the Aldebaran.  You can count six or seven stars.  Through binoculars you may see a few dozen.

The clear winter sky tonight provides for excellent sky watching.

2017: Venus as a Morning Star

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Venus last appeared in the morning sky in 2015 and 2016, when it appeared with Mars and Jupiter.

Introduction

Brilliant Venus zips into the morning sky during April  2017 and dominates the morning sky until year’s end.   During this morning appearance, Venus makes close appearances with the star Regulus and the planets Jupiter and Mars.

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This chart shows the rising time of bright planets, the moon, and stars near the planets’ orbital plane (ecliptic) compared to sunrise as calculated from U.S. Naval Observatory data for Chicago, Illinois in the Central Time Zone.  Additionally, the times when Jupiter sets and Saturn sets are charted compared to sunrise.  On April 7, Jupiter is at opposition and it sets in the west at sunrise.  The time differences are also displayed for Civil Twilight, Nautical Twilight and Astronomical Twilight.  At Astronomical Twilight, the sky is as dark as it gets naturally.

The rising time of Venus is represented by the green line on the chart.  It enters the chart in mid-March, reaching its maximum rising time difference during the summer, and leaves the sky in early 2018.  Notice that during the summer months of this appearance of Venus, the brilliant planet rises well before the beginning of twilight.  It stands low in the eastern sky as the sky brightens.

As Venus appears earlier in the morning sky, Jupiter shines brightly in the western sky, until about May 20 when Jupiter sets as Venus rises. (Notice on the chart, Jupiter sets line crosses the Venus rises at May 20.)  After this date Jupiter sets before Venus rises.  Similarly, Saturn, while not as bright as Jupiter or Venus, reaches opposition on June 15, setting in the west as Venus rises in the eastern sky.  Venus appears in the eastern morning sky and Saturn appears in the western sky until about July 25 when Saturn sets as Venus rises.  After this date Saturn sets before Venus rises.

Later in the year, Venus appears near Regulus.  This occurs near the date when the rising lines of Regulus and Venus intersect.  The same occurs for Mars, Spica, and Jupiter.  As Venus moves back into bright sunlight later in the year, it appears near Mercury, Antares and Saturn, although they appear together during bright twilight and out of view for most observers.

Venus has a close conjunction with Mars on October 5, followed by a very close (Epoch) conjunction with Jupiter on November 13.

The moon passes Venus each month, as our nearest celestial neighbor moves through its celestial path.  Two dates (May 22 and July 20) are especially noteworthy when Venus and the moon appear about 3.5 degrees apart.

Inferior Conjunction

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Venus moves between Earth and Sun on March 25, 2017; this is known as inferior conjunction.  Since Venus has a shorter orbital path and faster speed, it quickly moves into the morning sky.  The red line on the chart shows the division between morning and evening.  The line pointing from the earth to the sun indicates noon.  So at inferior conjunction, Venus rises with the sun, appears in the south at noon, and sets in the west at sunset.

Venus does not appear in the sky at midnight at mid-northern latitudes.  That occurs when a planet is opposite the sun in the sky as seen from Earth.  On the chart notice that the midnight line does not point toward Venus.

As Venus reaches this inferior conjunction, it passes above the sun.  Because it is north, above the sun, it rises earlier than the sun.  On conjunction morning it rises about 40 minutes before the sun.  On the rising chart above, it first appears on the chart on March 14, 11 days before it reaches conjunction!

Venus was last at inferior conjunction on August 25, 2015, 589 days between inferior conjunctions.

Greatest Brightness

The planet rapidly moves into the morning sky, rising earlier each morning.  It is very close to our planet and sparkles in the morning sky.  The brightness is from the proximity of the planet to Earth, its highly reflective clouds and the phase of the planet.  (Yes, Venus shows phases when viewed through a telescope.)  At this time Venus is about 170 times the moon’s distance, relatively close compared to other planets.

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From April 15 through May 13, Venus appears brightest in our skies, with the mid-point on May 1, 2017.  This is shown with the GB (greatest brightness) designation on the rising chart above.

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Update:  This image is from the beginning of the period of peak brightness.  Venus rises during twilight during maximum brightness during this appearance.

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Venus continues to rise earlier each morning. On the morning of May 22, the crescent moon appears about 3.5 degrees from Venus.

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Update May 22:  Venus and the moon appear together.

Greatest Elongation

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Venus reaches its greatest angular separation (46 degrees) from the sun on June 3.  This is shown by the GE symbol (greatest elongation) on the rising chart above.  It rises about 2 hours before sun near the beginning of twilight.

Venus Dazzles Morning Sky

 Venus continues rising earlier as summer begins.

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On July 14, Venus moves past Aldebaran.  The closest approach is about 4 degrees.

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The Binocular View

More striking is the star cluster near Venus and Aldebaran: Hyades.  The Hyades cluster is about 2.5 times farther away than ruddy Aldebaran.  Through binoculars, Venus, Aldebaran and the jewel-like stars of the cluster sparkle against the black velvet of the  predawn sky. Several dozen stars can be seen.

To the unaided eye, the Hyades resemble a check mark or a letter “V” if Aldebaran is included.

Clusters, like the Hyades, are used to refine distance measuring techniques as well descriptions of the lives of stars.  These clusters are thought to form at approximately the same time.  Stars that burn their nuclear fuels faster convert into other stellar forms sooner, such as red giants and red super giants.  From these stellar models, the estimate of the sun’s total lifespan is about 10 billion years.

Over time these clusters break apart; the gravitational forces between the stars are not strong enough to keep the cluster together.  The stars go their own way in their orbital path around the galaxy.

Our sun was likely formed in such a cluster and is now a lone star since it has gone into its own orbit around the Milky Way galaxy.

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On the morning of July 20, the crescent moon again appears with Venus.  The pair is separated by about 3.5 degrees.

In early August Venus rises about 3 hours before sunrise and begins to rise later each morning as displayed on the rising chart.  For the rest of the year, it loses about 30 minutes each month.

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In late summer and early Autumn look for Venus and Sirius at the same time.  Both are about the same height (altitude) above the eastern horizon.  Venus stands in the east-northeast and Sirius appears in the southeast.  Only the sun and moon shine brighter than Venus and Sirius is the brightest star in the night sky. See this link to view the last time Venus and Sirius appeared together in the morning sky.

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Venus continues its rapid eastward movement as compared to the stars and descent toward the sun’s glow, passing about a half degree from Regulus on September 20.  This pair rises about 2 hours before sunrise.

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Over a month later, Venus passes Spica.  The gap is nearly 4 degrees.

Mars Conjunction

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The first planetary conjunction of this appearance is with Mars.  On the morning of October 5, Venus passes 0.2 degrees from the Red Planet.  The planets are close on a few mornings before and after the conjunction.

Venus-Jupiter Epoch Conjunction

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Another Epoch (close) Conjunction of Venus and Jupiter occurs before sunrise on November 13.  The distance is about .2 degrees.  This conjunction is visible during twilight as the pair rises about 70 minutes before the sun.

The next conjunction between the pair is November 24, 2019 with the next epoch conjunction on April 30, 2022.

Superior Conjunction

Venus continues its rapid descent into bright sunlight.  Conjunctions occur with Mercury, Antares and Saturn, but they occur in bright twilight, out of the view of most observers.

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On January 9, 2018 passes behind the sun at its superior conjunction and reappears in the evening sky.

Lunar Conjunctions

The moon appears with Venus on the following dates:

April 23: 8 degrees

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May 22: 3.5 degrees (See description in text)

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June 20: 7 degrees

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July 20: 3.5 degrees (See description in text)
August 19: 4.5 degrees
September 17: 6 degrees
October 18: 5.5 degrees

Other Images

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Venus on April 2, 2017

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Venus:  May 8, 2017 (Even visible from the brightest city lights)

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Venus:  July 21, 2017

Venus provides a dazzling view of planetary, stellar and conjunctions during its morning appearance in 2017.

2017: The Mars-Venus Encounter

This appearance of Venus and Mars has concluded.

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Update:  Here are the planets when they were closest on February 3.

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A Recent Venus-Mars Conjunction

On an interval that varies from several days to nearly 23 months, Venus and Mars can appear very close together in the sky.  These conjunctions can be very close (Epoch) or with very wide separations.  During the conjunction displayed in the above image (November 3, 2015), the planets appeared about 0.7 degree (42 minutes) apart.  On October 5, 2017, they appear over 3 times closer with a separation of .22 degree (13.2 minutes).  (In the sky we measure the separation of objects by a geometric angle as seen from Earth.  The full moon’s diameter is about 0.5 degree. Your little finger at arm’s length covers a full moon.  Try it during the next time the moon is full. In the above image Venus and Jupiter are separated by about 7 degrees.  Your fist at arm’s length covers about 10 degrees in the sky.)

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At its brightest, Mars shines as the third brightest starlike object in the sky, following Venus and Jupiter.  This occurs when Mars is at opposition, when it is closest to Earth and opposite the sun in the sky.  At opposition, Mars rises in the east at sunset, appears in the south at midnight and sets in the west at sunrise.  Conjunctions of Mars (and the planets beyond Earth) with Venus occur when Venus is within 47 degrees of the sun.  This angle is the greatest angular separation that Venus has from the sun from our home planet view.  Yet, if Venus and Mars appear too close to the sun, they are lost in the sun’s brightness and not visible from Earth.  Because Mars is far from our planet during a Venus conjunction, it is not near its maximum brightness, so Venus always appears very bright in the sky and a conjunction with Mars occurs when the Red Planet is dimmer. A Venus-Mars conjunction does not occur when Mars is near its brightest (at opposition)  Notice Mars’ brightness in the image at the beginning of this article from the 2015 conjunction.

Notice that Venus does not appear at opposition; so it is not visible at midnight.

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At the time of this writing, Venus has recently entered the evening sky and passed its Epoch Conjunction with Jupiter.  On September 15,2016, Venus appears low in the sky in the west.  Saturn and the star Antares are farther south.  Mars is beyond them, about 62 degrees from Venus.

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From a view outside the solar system, this 62-degree angle is represented in the chart above.  In all these charts, Earth is at the geometric vertex of the angle.

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As the dates advance toward the New Year, Venus moves closer to Mars.  The chart above shows the setting times of planets, the moon, and selected stars compared to sunset during part of 2017, until Mars disappears into the sun’s glare.  On January 1, 2017, notice on the chart that The moon sets close to the time of the setting of Venus (14 minutes difference).  This indicates that they appear close to each other in the sky.  Mars follows Venus by about an hour.

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This chart represents what we see in the sky during the early evening on New Years Day.  Venus and the Moon are 4 degrees apart with Mars about 12 degrees to the upper left of Venus.

During January 2017, Venus and Mars appear to move closer together as the setting lines of the two planets begin to converge.

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On February 3, 2017, the planets close to 5.5 degrees, with Mars setting 19 minutes after Venus.  The chart above shows their close angular proximity, but they are nearly 126 million miles apart in space, over 300 times the distance between the earth and the moon.

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In the sky, brilliant Venus dominates the southwestern sky with dimmer Mars 5.5 degrees to its upper left.

After this near meeting, Venus rapidly moves back toward the sun, as indicated by the rapidly decreasing time it sets after the sun as indicated by the setting graph earlier in this article.  The planets appear farther apart on the sky as the time difference in their settings increases.

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On March 1, the planets are 13 degrees apart with the moon 5 degrees to the lower left of Mars.

By March 15, Venus sets at the beginning of twilight and 4 days later it sets in bright twilight.  This is a rapid plunge into the sun’s glare.

On March 25, Venus passes between the earth and sun (inferior conjunction) and rapidly moves into the morning sky.  Mars slowly sets earlier each night until it disappears into the sun’s glare toward its solar conjunction on July 27.

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In late April, Mars moves through Taurus, which has two prominent star clusters:  Pleiades and Hyades.  The Pleiades star cluster is a compact cluster of many blue stars.  Commonly named the “Seven Sisters,” the cluster is a spectacular sight through binoculars.  Mars passes closest to the cluster (3.5 degrees) on April 21.    With binoculars the cluster and the planet are be visible at the same time.

The bright star Aldebaran appears in line with the Hyades cluster; its loosely collected stars resemble a check mark.  The Hyades cluster is another spectacular view through binoculars.

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On April 28, the moon joins the view in the western sky when it is 4 degrees to the upper left of Aldebaran.  Mars continues its planetary motion among  these stars.

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On April 29, Mars and Aldebaran set at the same time, but they are nearly 7.5 degrees apart.  By this date, Venus is shining brightly in the morning sky rising about 90 minutes before sunrise.

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On May 6, Mars passes 6.5 degrees to the upper right of Aldebaran.  A few days later, Mars begins setting during evening twilight, each night setting deeper into the glow after sunset;  It moves behind the sun on July 27.

Upcoming Venus-Mars Conjunctions

  • October 5, 2017 — 13.2 minutes separation
  • August 24, 2019 — 18.6 minutes
  • July 3, 2021 — 29.4 minutes

 

Our images and charts collections are available here –> http://goo.gl/Sfp1ur

See our article about Venus’ evening appearance.

See our  article outlining the planets in the evening sky in 2016.

Jupiter Tonight, April 7, 2013

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Bright Jupiter gleams from the western sky at 8:25 p.m. CDT this evening as seen from the Chicago area in this 15-second exposure. (Click the image to see it larger.)  This Giant Planet shines in front of the stars of Taurus with its brightest star Aldebaran.  Two bright star clusters, Pleiades and Hyades, shine nearby.  They are best viewed through binoculars.  Zeta Tauri and Elnath mark the horns of the bull.  Betelgeuse (Orion) and Capella (Auriga) also appear in the view.

For more about the April sky, see our monthly skywatching description.

Jupiter Tonight, April 1, 2013

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Jupiter shines brightly from the western sky this evening as seen from the Chicago area at 8:15 p.m. CDT in this 15-second time exposure. (Click the image to see it larger.) It appears near Aldebaran, the brightest star in Taurus, along with the widely spread Hyades star cluster. Zeta Tauri and Elnath represent the bull’s head.  Capella (Auriga) and Betelgeuse also appear in the image.

For more about the April sky, see our monthly skywatching description.

Sky Watching March 2013

Image Credit

March is a time of transition from the long, cold nights of winter to the longer days of spring.  We adapt to this change by moving our clocks on hour ahead of the sun on the morning of March 10 in most of the United States.  While there’s still not much daylight to save or shift to evening hours, daylight increases by nearly 85 minutes during the month.

On March 20, astronomical spring begins in the northern hemisphere.  At 6:02 a.m. CDT, the sun’s rays are most direct on the equator, marking the vernal equinox.

Moon Phases

Moon Phase Date
Last Quarter March 4
New Moon March 11
First Quarter March 19
Full Moon March 27

Comet PanSTARRS

Comet PanSTARRS emerges from behind the sun in March.  While this posting is being composed in late February 2013, the comet’s brightness seems dimmer than once predicted.  The following video explains the difficulty in predicting comet brightness and more about the comet:

pans_luneOn the evening following New Moon, the crescent moon appears near the comet as shown in the chart above.  Look for the crescent moon low in the western sky.  Binoculars may be required to see the comet.

Evening Sky

Jupiter is high in the southwest at sunset, setting in the west at 1 a.m. CST early in the month.  By month’s end it sets at 12:30 a.m. CDT.

jup_luneJust a few nights after the moon appears with Comet PanSTARRS, it appears near Jupiter.  The chart above shows the moon and Jupiter in front of the stars of Taurus.   The bright star Aldebaran is nearby along with the bull’s bright star clusters:  Pleiades and Hyades.


sat_luneThe above chart shows Saturn and Spica with the Moon on March 1 and March 2 at 5 a.m. CST in the southern sky.

sat_lune_2Later in the month, the moon moves past Spica and Saturn again.  The chart shows them in the southwest at 5 a.m. CDT.  By month’s end, Saturn rises at 9:30 p.m. CDT.

Venus and Mars are not visible this month.   Venus reaches superior conjunction on March 28 and is set to move into the western evening sky in April to become a bright Evening Star.  (See our posting for Venus as an Evening Star, 2013-2014.)

Slide1This chart shows the positions of Earth, Sun, and Venus when Venus is at superior conjunction on March 28.  It is on the far side of the sun and lost in the sun’s brilliance.

Mars moves deeper into bright evening twilight and approaches conjunction on April 18 then moving into the morning sky visible in the eastern sky before sunrise starting in late June.

sol_sysThis chart shows the planets visible from Earth in their relative positions in the solar system on March 15, 2013.  (Click the image to see it larger.  On the this date, Mercury, Venus, and Mars appear in the sun’s bright glare.  Jupiter and Saturn are seen easily seen as they are away from the sun’s bright glare.

With the changing of the seasons and the bright winter stars fading in the western sky, March offers more daylight and the possibilities of a bright comet.

Jupiter Tonight, February 20, 2013

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Bright Jupiter shines from high in the southern skies during the early evening of February 2013 as seen in this 30-second exposure image as seen from the Chicago area. ( Click the image to see it larger.)  This giant planet shines from in front of the stars of Taurus and its bright star Aldebaran.  Two bright star cluster, Pleiades and Hyades, are part of the constellation and shine nearby.

The waxing gibbous Moon is just outside the frame at the upper left.

For more about skywatching this month, see our February posting.