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11/10/2020 – Ephemeris – Mercury will reach it greatest separation from the Sun in the morning today

November 10, 2020 Comments off

This is Bob Moler with Ephemeris for Tuesday, November 10th. Today the Sun will be up for 9 hours and 45 minutes, setting at 5:19, and it will rise tomorrow at 7:35. The Moon, 2 days past last quarter, will rise at 2:42 tomorrow morning.

Mercury will reach its greatest western elongation from the Sun near noon today (17:00 UT). That means it was visible this morning before sunrise in the east. And will be visible again tomorrow morning. The next Mercury greatest elongation will be January 24th, next year. It will be a greatest eastern elongation, which will be visible in the western sky in the evening after sunset. So western elongations are seen in the east and eastern elongations are seen in the west. The “from the Sun” is usually omitted in astronomical lists of events, but implied. Sounds a bit confusing, but it makes weird sense. Mercury’s morning appearance will last about a week before it get too low to easily spot, below and left of Venus.

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

Addendum

Mercury, Venus, Moon tomorrow morning at 6:30 am

Mercury, Venus, Moon tomorrow morning November 11, 2020 at 6:30 am. The orange line is the ecliptic, the plane of the Earth’s orbit. It is the path of the Sun in the sky, The Moon and planets also stick close to that line. The Moon is a crescent, though that can’t be seen at this scale. Over the next week Venus and Mercury will slide downward along the ecliptic in relation to the stars, as will the Moon at greater speed. Created using Stellarium.

11/09/2020 – Ephemeris – Tiny Mercury makes an appearance in the morning sky

November 9, 2020 Comments off

This is Ephemeris for Monday, November 9th. Today the Sun will be up for 9 hours and 48 minutes, setting at 5:20, and it will rise tomorrow at 7:33. The Moon, 1 day past last quarter, will rise at 1:26 tomorrow morning.

The tiny planet Mercury is now visible in the morning twilight. It will reach its greatest separation from the Sun in the morning sky. Astronomers call it “greatest western elongation”. It’s west of the Sun, but we’ll see it in the eastern sky as it rises at 5:49 am in the east-southeast. That’s an hour and 44 minutes before the Sun. By 6:15 or 6:30 am, it should be high enough to spot. That is if it’s clear, an iffy prospect this time of year. It will start to move back to the Sun and actually brighten retaining its best visibility for the next 7 days or so. Mercury has a very elliptical orbit of the Sun. During our two good seasons to view the planet, spring evenings and autumn mornings Mercury is closest to the Sun. Mercury is best seen in the southern hemisphere when its autumn morning appearances and spring evening appearances are seen when Mercury is farthest from the Sun.

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

Addendum

Mercury and Venus in the morning at 6:30 am

Mercury and Venus in the morning at 6:30 am. Created using Stellarium.

 

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

February 26, 2019 Comments off

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

Northern hemisphere elongation of Mercury in the spring.

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.