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Venus at greatest western (morning) elongation on March 22

Venus at greatest western (morning) elongation on March 22 Read more

Tonight for March 21, 2014

Because the ecliptic - pathway of the planets - hits the horizon at a shallow angle on March mornings in the Northern Hemisphere, Mercury sits buried in the glare of morning twilight.

Because the ecliptic – pathway of the planets – hits the horizon at a shallow angle on March mornings in the Northern Hemisphere, Mercury sits buried in the glare of morning twilight.

The ecliptic intersects the horizon at a steep angle in the Southern Hemisphere, so Mercury will be easier to see from that part of the world.

The ecliptic intersects the horizon at a steep angle in the Southern Hemisphere, so Mercury will be easier to see from that part of the world.

If you're up before dawn, look for the moon, the star Antares and the planet Saturn on Saturday, March 22.

If you’re up before dawn, look for the moon, the star Antares and the planet Saturn on Saturday, March 22.

Venus, the second planet outward from the sun, lies inside of Earth’s orbit. That means this world can never be opposite the sun in Earth’s sky – like the moon at full phase. Nor can this world get as far as 90o from the sun, like the moon at first quarter phase (evening sky) or last quarter phase (morning sky). At most, Venus can swing somewhat more than 45o east of the sun (evening sky) or 45o west of the sun (morning sky).

On March 22, 2014, Venus reaches its greatest western elongation from the sun (46.6o). This places Venus in the predawn and dawn sky before sunrise. It’s well worth getting up early to see this magnificent world, as it’s the third-brightest celestial body to light up the heavens, after the sun and moon. The orbit of Venus comes closer to Earth’s orbit than the orbit of any other planet does.

A greatest western elongation of an inferior planet (a planet whose orbit lies inside Earth’s orbit: Mercury and Venus) is most favorable when it closely coincides with the autumn equinox. A greatest western elongation is least favorable when it happens at or near the spring equinox. Since the recent March 20 equinox ushers in the Southern Hemisphere’s autumn equinox, this is a very favorable greatest morning elongation of Venus for southerly latitudes. It’s not nearly as favorable at northerly latitudes because the March equinox is the Northern Hemisphere’s spring equinox.

By the way, Mercury – the innermost planet – exhibits its greatest western (morning) elongation (27.6o) about one week before Venus reaches its greatest elongation. For the same reason, March 2014 presents a stunning morning apparition of Mercury in the Southern Hemisphere but a poor one for the Northern Hemisphere.

So the rising times of Venus and Mercury vary greatly, depending upon your latitude. At mid-northern latitudes – such as those in the US and Europe – Venus rises roughly two hours before the sun, and Mercury rises less than one hour before sunrise. At mid-southern latitudes – such as those in southern Australia and New Zealand – Venus rises close to four hours before the sun and Mercury rises about two hours before. At the equator (0o latitude), Venus rises about three hours before sunrise and Mercury comes up about one and one-half hours before the sun.

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky Planisphere today.

Not too late. Order your 2014 EarthSky Lunar Calendar today!

Given a clear sky, you should be able to catch Venus in the eastern sky before sunrise from virtually anywhere worldwide, as Venus reaches its greatest elongation from the rising sun on March 22, 2014.