Tag: Mercury

2019, August: Mercury and Heliacal Rising of Sirius

The heliacal rising is the first appearance of a bright star in the morning sky before sunrise.

During August, as Mercury makes a morning appearance, brilliant Sirius, the sky’s brightest star, makes its first morning (heliacal) rising just before sunrise.  For the latitude on the diagram, about 41.7 degrees, this is August 14, 2019.  For locations farther south, this occurs days earlier and later for latitudes farther north.

August 29:  Now appearing in the darker morning sky, Sirius is visible with Betelgeuse and Procyon.

Sirius, the Dog Star, is sometimes called the Nile Star as its heliacal rising historically coincided with the flooding of the Nile River.  The Dog Days of Summer (in the northern hemisphere) occur, coincidentally, during August when Sirius and Procyon, the Little Dog Star, appear in the eastern sky before sunrise.

Update:  August 9, Mercury is low in the northeast.  First located with a binocular then observed without its assistance.

Mercury is at greatest elongation on August 9.  Because Mercury is closer to the sun than Earth, we see Mercury appear in either the morning or evening sky around the time the sun rises or sets.  It appears in the sky earlier each morning or stays there later each night.  It reaches its greatest separation from the sun and then seems to reverse its direction, moving back into sunlight, only to repeat the process a few months later at the other horizon and sky setting.

As Mercury moves back toward the sun in August, it is lower in the sky each morning at about the same time.  Sirius appears higher in the sky each morning at the same time.  And Mercury gets brighter as it appears nearer to the sun.  As Sirius appears higher, it seems to brighten because it gets above the thicker atmosphere that tends to diminish the brightness of celestial objects.  They are not quite the same brightness, but appear at the same altitude around August 19.

To locate the planet and the star, find a clear horizon in the east-northeast and east-southeast.  Start looking for Mercury and Sirius about 30 minutes before sunrise.  A binocular may help in viewing them.  Mercury is low in the east-northeast, about 10 degrees up.  Sirius is very low, in the east-southeast about 3 degrees up when first visible.  Sirius may twinkle wildly this low in the sky.  To be sure you have Sirius, don’t confuse it with Procyon in the east and a little higher.  Orion is higher in the sky and its three belt stars make an imaginary pointer that take us to the area to find Sirius.  Reddish Betelgeuse is higher in the sky,  Sirius, Procyon, and Betelgeuse make nearly an equilateral triangle known as the Winter Triangle.

Sirius’ heliacal rising occurs every year about this time.  This year the event is a little more interesting because a bright planet is in the sky.

2019, June 5-30: Mercury and Mars in the Evening Sky

The chart above shows the evening positions of Mercury and Mars from June 5, 2019, to June 30, 2019. The moon is part of the scene on June 5 and June 6.

About 45 minutes after sunset, Mercury and Mars are visible in the west-northwest  beneath Pollux and Castor, the Gemini Twins.  Early in the month, the  stars are about one-third of the way up in the sky.

Mercury is beginning an evening appearance.  Early in the month, it is brighter, but closer to the horizon.

Twilight lasts longer this time of year, so it’s not visible in the latter sky glow as the sky darkens further.  So, the upcoming conjunction with Mars is better viewed with a binocular.  Both planets’ movements are easier viewed across several nights.

On June 5, the waxing crescent moon, the waxing crescent moon that is 2.7 days past the New phase and only 9% illuminated is 6.3° to the upper left of Mars, which sets at the end of evening twilight.  At this time the Red Planet is about 13° up in the west-northwest, a little over halfway between Castor and Pollux and the horizon.

Each evening until the conjunction, Mercury is closer to Mars.

On June 18, Mercury passes close to Mars, less than the moon’s apparent diameter.  The chart above shows them 45 minutes after sunset when they appear in the west-northwest.  Use a binocular to locate them.  Can you see them without a binocular?

As the month progresses, the planets appear lower and in a brighter sky. Continue to use a binocular to track the planets.

By month’s end, a dimmer Mercury appears to the upper left of Mars.

2019, April 13-20: Venus and Mercury in Morning Sky

Venus and Mercury appear near each other on mid-April.  There is no conjunction as Mercury does not pass Venus.  Mercury moves faster and, typically, its motion causes the two to pass each other.  During this event, the two planets do not pass each other but they move within 5° of each other.  This event is know as a quasi-conjunction.

Mercury is in a very unfavorable apparition to observe. It appears very low in the east at Civil Twilight, about 30 minutes before sunrise, when the sun is 6° below the horizon. During this appearance this speedy planet does not rise before Nautical Twilight – which occurs about an hour before sunrise; so Mercury visible in a very bright sky, near the horizon. At its greatest elongation, it is only 4° in altitude.  Find a clear horizon and use a binocular.  First locate Venus then look through your binocular to locate this elusive planet.

The Venus-Mercury gaps:

April 13: 4.5°
April 14: 4.4°
April 15: 4.4°
April 16: 4.3°
April 17: 4.3°
April 18: 4.3°
April 19: 4.4°
April 20: 4.5°

On these mornings, it’s possible to see four planets in the morning sky — Mercury, Venus, Jupiter, Saturn — although a binocular may be needed to locate Saturn.  The Ringed Wonder is low in the southern sky,  less than one-third of the way up in the sky.  Jupiter is farther west, to the right of the south direction, at about the same height as Saturn above the horizon.

More about the morning planets:

2019: Winter Morning Planet Parade Album

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On a recent trip to a more southerly latitude, the morning planets presented themselves high in the sky.  This album shows them on the mornings of February 28, March 1, and March 2, 2019.  When travelling farther south, the southern stars and planets appear higher in the southern sky.

2019: February is Mercury’s Best Evening Appearance of the Year

2019: Mercury makes its best evening appearance of the year. It is found in the western sky about 30 minutes after sunset. Use a binocular to locate it , then look without optical assistance.
2019, March 1: Mercury shines in the west during bright twilight during its best evening appearance during the year.

Mercury has its best evening display during late February 2019.  The planet is almost always visible in bright twilight.  Here’s what you need:  A clear western horizon and a binocular.

The chart above begins on February 16; Mercury is only 6° up in the western sky. The chart shows the planet’s position 30 minutes after sunset.  Mercury appears as a bright star.  Find it first with the binocular and then try to locate it with optical assistance.

Each night the planet appears higher in the sky and dims rapidly.  By the end of February Mercury is only about half as bright as it appears on February 16 and over twice as high up in the sky.

On February 26, Mercury is at its greatest angular separation from the sun, known as its greatest elongation.  On this evening it is about 13° up in the sky.  Even past greatest elongation, Mercury appears higher in the sky as the month ends.  It is nearly 14° degrees up.

Mercury then heads back into the sun’s glare, appearing lower and rapidly dimming in brightness.  By early March, it is difficult to see with the unaided eye. On March 7, the waxing crescent moon passes over 8° to the left of the fading Mercury, but it will not be much help in locating the planet because of its proximity to Mercury.


2018: December 13: Morning Star Venus and Mercury

Bright Morning Star Venus and Mercury shine during twilight this morning in the southeastern sky.  The planet Venus is at its earliest rising time this morning for this appearance, rising shortly before 3:30 a.m. CST.  Mercury is displaying a very favorable morning appearance, although it nearly always appears during twilight.

More about Venus and Mercury

2018, December 9: Morning Star Venus and Mercury

Brilliant Venus shines in the southeast during twilight this morning. Mercury, low in the sky, joins this brighter inner planet. (Look for Mercury with binoculars to first locate it. Zoom in on the image to see the planet.) During the next several mornings, Mercury is brighter and higher in the sky. Jupiter joins the view later in the month.

For more about Venus, and Mercury and Jupiter’s morning dance, see the following articles: