03/24/2020 – Ephemeris – Venus reaches greatest eastern elongation from the Sun today

Ephemeris for Tuesday, March 24th. Today the Sun will be up for 12 hours and 23 minutes, setting at 8:01, and it will rise tomorrow at 7:35. The Moon is new today, and won’t be visible.

Today, around 6 p.m. the planet Venus will reach its greatest eastern elongation from the Sun. That means Venus will appear as far east of the Sun that it can get at an angle of 46.1 degrees. Venus, like Mercury orbits the Sun inside the Earth’s orbit, so is always seen close to the Sun. In telescopes Venus will look like a tiny first quarter Moon. That’s for the same reason. The Sun is illuminating half of the side we can see. Venus is moving directly toward us now, at a distance of 66.5 million miles (117 million km). As Venus approaches us, it will grow in size in telescopes, becoming larger in appearance than Jupiter the largest planet and a thinner and thinner crescent. It will leave the evening sky, passing between the Earth and the Sun, only 27 million miles (43 million km) away on June 3rd.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Venus at greatest eastern elongation seen tonight at 8:20 p.m. The red line its orbit if we could see it tonight. Venus will be moving to the right and down in the coming days. Created using Stellarium.

02/26/2019 – Ephemeris – Mercury at greatest eastern elongation from the Sun tonight

Ephemeris for Tuesday, February 26th. Today the Sun will be up for 11 hours even, setting at 6:26, and it will rise tomorrow at 7:24. The Moon, at last quarter today, will rise at 2:49 tomorrow morning.

This evening the planet Mercury is at its greatest distance from the Sun to the east by an angle of 18 degrees. It’s called greatest eastern elongation from the Sun. Mercury has a very elliptical orbit of the Sun, and right now it’s near its closest to the Sun called perihelion, of 28.6 million miles (46.1 million km). In late winter and spring the ecliptic, the path in the sky that the planets appear near, meets the horizon at a steep angle near sunset, which allows us to see planets near and east of the Sun more easily. The same is true for the planets west of the Sun in the morning in the fall. Southern hemisphere observers see Mercury best when its is at aphelion, farthest from the Sun, 66 percent farther away.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Looking at Mercury at greatest eastern elongation tonight February 26, 2019 from Northern Michigan displaying its orbit with a transparent horizon at sunset. Notice how lopsided the orbit appears, extending farther below the horizon (green line) than above. The yellow line is the ecliptic. Created using Stellarium and GIMP.

The next greatest elongation of Mercury is the western elongation on April 11, 2019. Here we are looking at it from the southern hemisphere, where it’s autumn displaying its orbit with a transparent horizon at sunrise. Notice how lopsided the orbit appears, extending farther above the horizon (green line) than below. The yellow line is the ecliptic. Created using Stellarium and GIMP.

Note the same is true for both northern and southern hemispheres:

Late winter and spring – planets near and east of the Sun are seen more easily after sunset.

Late summer and autumn – planets near and west of the Sun are seen more easily before sunrise.

03/28/2017 – Ephemeris – Mercury is visible in the evening sky now

Ephemeris for Tuesday, March 28th. The Sun will rise at 7:30. It’ll be up for 12 hours and 35 minutes, setting at 8:05. The Moon, 1 day past new, will set at 8:56 this evening.

Mercury is in the evening sky now for it’s spring appearance. Mercury is best seen when it’s near its farthest from the Sun on spring evenings and autumn mornings. Mercury will reach its greatest elongation east of the Sun this coming Saturday with a 19 degree angle of separation from the Sun. This tiny planet is brighter before eastern elongating than after it. I find that the optimal time to look for Mercury is about 45 minutes after sunset. That makes it about 8:50 p.m. At that time Mercury will be low in the west only 9 degrees above the horizon. That’s a bit less than the width of a fist held at arm’s length above the lake or sea horizon, or the base of distant trees that are on your level. Mercury will be visible for about a week or so.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Mercury near the western horizon at 8:50 p.m. or 45 minutes after sunset. Also shown is its orbit as it appears tonight. The Moon and Uranus are not actually visible in the twilight glare. Mars will be visible a bit later. The Moon will appear between Mercury and Mars tomorrow night. Created using Stellarium.

01/12/17 – Ephemeris – Venus is at greatest eastern elongation today

Ephemeris for Thursday, January 12th.  The Sun will rise at 8:17.  It’ll be up for 9 hours and 7 minutes, setting at 5:25.  The Moon, at full today, will rise at 6:04 this evening.

Today, around 8 a.m. the planet Venus will reach its greatest eastern elongation from the Sun. What that means in simple terms is that Venus will appear as far east of the Sun that it can get.  The angle between it and the Sun will be 47.1 degrees.  Venus, like Mercury orbits the Sun inside the Earth’s orbit, so is always seen close to the Sun.  In telescopes Venus will look like a tiny half illuminated orb, like a first quarter Moon.  That’s for the same reason.  The Sun is illuminating half of the side we can see.  Venus is  moving directly toward us now, at a distance of 63 million miles (102 million km).    As Venus approaches us, it will grow in size in telescopes, becoming larger in appearance than Jupiter the largest planet.  It will leave the evening sky, passing between the Earth and the Sun, only 26 million miles away on March 25th.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Venus at 5:30 p.m. January 12, 2017 also displaying its orbit. Created using Stellarium.

Venus in a telescope showing it half illuminated at greatest eastern elongation. Created using Stellarium.

There’s an odd phase effect called the “Venus Dichotomy” where at the instant of greatest elongation that Venus’ phase is not exactly half illuminated.  Half phase may differ by several hours.  The actual time of greatest eastern elongation according to NASA’s SKYCAL Calendar at https://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html is January 12 at 7:59 a.m. EST or 12:59 UT.

Inner solar system showing the relationship of Venus and the Earth. At greatest elongation The angle between Venus-Sun line and Venus-Earth line is 90 degrees. which is why Venus shows as half illuminated. Created using the application NASA’s Eyes.

Note that the chart above also shows NASA’s inner solar system missions.  To download the app, created by the Jet Propulsion Laboratory (JPL), go to https://eyes.nasa.gov/.  Use it to follow the progress of NASA solar system missions.

12/28/2015 – Ephemeris – Mercury is at its greatest penetration into the evening tonight

Ephemeris for Monday, December 28th.  The Sun will rise at 8:19.  It’ll be up for 8 hours and 49 minutes, setting at 5:09.   The Moon, 3 days past full, will rise at 8:57 this evening.

Later this evening the tiny planet Mercury will appear at its greatest separation from the Sun.  This is a little early to be viewing Mercury in the evening.  Generally the best time to be able to view Mercury, when it’s east of the Sun, in the evening is from late winter into spring.  Mercury’s event is called its greatest eastern elongation from the Sun.  The sky may be dark enough in the west to start looking for Mercury 20 minutes after sunset.  That’s about 5:30 when Mercury will be 9 degrees above the true horizon and due southwest.  For the next half hour Mercury will drop to 5 degrees altitude, but the skies will be darker.  Mercury will set at 6:38, and you will lose it before that.  Mercury has always been a difficult planet to view from the Earth.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Mercury at greatest eastern elongation (19.7 degrees) from the Sun. 6 p.m. December 28, 2015. Created using Stellarium.

05/07/2015 – Ephemeris – Mercury is at greatest eastern elongation today

Ephemeris for Thursday, May 7th.  Today the Sun will be up for 14 hours and 30 minutes, setting at 8:54.   The Moon, half way from full to last quarter, will rise at 12:20 tomorrow morning.  Tomorrow the Sun will rise at 6:23.

The tiny planet Mercury has been in the news lately because the MESSENGER spacecraft plunged onto its surface a week ago, after having mapped and studied chemical composition of this planet for four years. Today, for Mercury watchers from the Earth, it reached its greatest angular separation from the sun in its orbit, of 21 degrees just before 1 a.m.   Mercury has always been a tough planet to study, low to the horizon in twilight.  It’s also a tough planet to get to with a spacecraft, being far down the Sun’s gravity well.  MESSENGER took 7 years to get there, bleeding off energy by passing Earth, Venus and Mercury itself to fall into orbit of this little world that was full of surprises.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Mercury’s orbit as seen from about 45 degrees north latitude Earth at the greatest eastern elongation at sunset on May 7, 2015. Created using Stellarium.

°

The other red line is the plane of the Earth’s orbit.  In the spring at sunset it is much closer to vertical than in autumn.  The angle of the ecliptic to the horizon at sunset on the vernal equinox is 90° – (your latitude) + 23.5°.  Here near 45° north latitude it’s 68.5°.  For the sunset at the autumnal equinox the formula is 90° – (your latitude) – 23.5° or 21.5°.  The ecliptic will really lay down making planets close to the direction of the Sun hard to spot.  In the morning sky the ecliptic will be steep at the autumnal equinox and lay down at the vernal equinox.  Thus the best time to spot Mercury, which never strays far from the sun is on late winter and spring evenings and late summer and autumn mornings.  Also note that Mercury’s 7 degree inclination to the ecliptic helps it now.

Also note that we are seeing Mercury’s orbit nearly edge on.  It will be edge-on in a couple of days.  It so happens that a year from now, the morning of May 9th, 2016, for us in the United States, Mercury  will transit, or cross in front of, the Sun.  Three years ago this June we witnessed the extremely rare transit of Venus.  The transit of Mercury isn’t as spectacular or rare, but it’s rare enough.

 

01/27/2014 – Ephemeris – Mercury’s back in the evening sky now

Ephemeris for Monday, January 27th.  The sun will rise at 8:06.  It’ll be up for 9 hours and 37 minutes, setting at 5:44.   The moon, half way from last quarter to new, will rise at 5:47 tomorrow morning.

Mercury is now making an appearance in the evening sky.  It will have its greatest elongation or angular separation from the sun on Friday of 18.4 degrees.  Mercury has a markedly elliptical orbit.  Unfortunately both the best times to view Mercury from the northern hemisphere of earth, late summer and autumn mornings and late winter and spring evenings, Mercury is near perihelion or closest point in its orbit to the sun.  The southern hemisphere, which has seasons opposite from ours, has the  same viewing opportunities in late summer and autumn mornings and late winter and spring evenings. Only for them Mercury is near aphelion or its farthest from the sun, so this planet can be seen just outside of twilight, where we don’t have that luxury.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Mercury and its orbit as seen from Earth at 6:15 p.m. on January 27, 2014. Created using Stellarium.

Mercury will move to the top of the orbital loop Friday about 5 a.m. and descend to the right.  The Mercury image will be posted Wednesday again.