At northerly latitudes in the Northern Hemisphere, the Summer Triangle may be your ticket to locating Mercury by the horizon.
On late winter mornings, the shallow angle of the ecliptic (pathway of planets) keeps Mercury buried in the glow of morning twilight. It is now late winter for the Northern Hemisphere.
Meanwhile, it’s now late summer for the Southern Hemisphere, so the steep tilt of the ecliptic brings Mercury into the morning sky before dawn’s first light!
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Mercury, the innermost planet of the solar system, never strays far from the sun in Earth’s sky. For that reason, this world is often lost or obscured by the sun’s glare. But on February 24, 2015, Mercury reaches its greatest angular distance west of the sun (26.75o), so this world can now be seen in the eastern sky before sunrise. Astronomers call this a greatest elongation of Mercury.
No matter where you live worldwide, an unobstructed horizon in the direction of sunrise will work to your advantage for your Mercury quest. In addition, binoculars will come in handy – especially for Northern Hemisphere observers.
How soon Mercury rises before the sun very much depends on where you reside on the globe. From temperate latitudes in the Northern Hemisphere, Mercury climbs above the horizon about an hour before sunrise. From temperate regions in the Southern Hemisphere, Mercury enters the sky better than two hours before the sun. The Southern Hemisphere has the great big advantage for watching this particular morning apparition of Mercury.
Every year, Mercury has six to seven greatest elongations. If it’s a greatest western elongation, Mercury appears in the morning sky. If it’s a greatest eastern elongation, Mercury appears in the evening sky. We give Mercury’s greatest elongations for the year 2015:
Jan 14: 18o 54’ east of the sun
Feb 24: 26o 45’ west of the sun
May 7: 21o 11’ east of the sun
Jun 24: 22o 29’ west of the sun
Sep 4: 27o 08’ east of the sun
Oct 16: 18o 07’ west of the sun
Dec 29: 19o 43’ east of the sun
Because Mercury’s orbit around the sun is so eccentric (oblong or egg-shaped), a greatest elongation of Mercury varies from about 18 to 27o from the sun in the course of one year. You may be surprised to know that the October 16 greatest western elongation (18o 07’ west of the sun) presents a better morning apparition for the Northern Hemisphere than greatest western elongation on February 24 (26o 45’ west of the sun).
In either the Northern or Southern Hemisphere, greatest morning elongations are most favorable when they occur in late summer or early autumn. And in either the Northern or Southern Hemisphere, greatest evening elongations are most favorable when they happen in late winter or early spring.
The converse is also true: in either hemisphere, greatest morning elongations are least favorable in late winter and early spring, and greatest evening elongations are least favorable in late summer and early autumn.
Since it’s now late summer for the Southern Hemisphere, southern climes get to enjoy a ringside seat to this morning apparition of Mercury; and since it’s now late winter in the Northern Hemisphere, northerly latitudes must be content with a seat in the bleachers.
Bottom line: Late February 2015 is a great time to look for Mercury before dawn! The planet’s greatest western elongation falls on February 24, 2015.
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At northerly latitudes in the Northern Hemisphere, the Summer Triangle may be your ticket to locating Mercury by the horizon.
On late winter mornings, the shallow angle of the ecliptic (pathway of planets) keeps Mercury buried in the glow of morning twilight. It is now late winter for the Northern Hemisphere.
Meanwhile, it’s now late summer for the Southern Hemisphere, so the steep tilt of the ecliptic brings Mercury into the morning sky before dawn’s first light!
Want to see planets? Sign up for EarthSky News – a free daily newsletter – today!
Mercury, the innermost planet of the solar system, never strays far from the sun in Earth’s sky. For that reason, this world is often lost or obscured by the sun’s glare. But on February 24, 2015, Mercury reaches its greatest angular distance west of the sun (26.75o), so this world can now be seen in the eastern sky before sunrise. Astronomers call this a greatest elongation of Mercury.
No matter where you live worldwide, an unobstructed horizon in the direction of sunrise will work to your advantage for your Mercury quest. In addition, binoculars will come in handy – especially for Northern Hemisphere observers.
How soon Mercury rises before the sun very much depends on where you reside on the globe. From temperate latitudes in the Northern Hemisphere, Mercury climbs above the horizon about an hour before sunrise. From temperate regions in the Southern Hemisphere, Mercury enters the sky better than two hours before the sun. The Southern Hemisphere has the great big advantage for watching this particular morning apparition of Mercury.
Every year, Mercury has six to seven greatest elongations. If it’s a greatest western elongation, Mercury appears in the morning sky. If it’s a greatest eastern elongation, Mercury appears in the evening sky. We give Mercury’s greatest elongations for the year 2015:
Jan 14: 18o 54’ east of the sun
Feb 24: 26o 45’ west of the sun
May 7: 21o 11’ east of the sun
Jun 24: 22o 29’ west of the sun
Sep 4: 27o 08’ east of the sun
Oct 16: 18o 07’ west of the sun
Dec 29: 19o 43’ east of the sun
Because Mercury’s orbit around the sun is so eccentric (oblong or egg-shaped), a greatest elongation of Mercury varies from about 18 to 27o from the sun in the course of one year. You may be surprised to know that the October 16 greatest western elongation (18o 07’ west of the sun) presents a better morning apparition for the Northern Hemisphere than greatest western elongation on February 24 (26o 45’ west of the sun).
In either the Northern or Southern Hemisphere, greatest morning elongations are most favorable when they occur in late summer or early autumn. And in either the Northern or Southern Hemisphere, greatest evening elongations are most favorable when they happen in late winter or early spring.
The converse is also true: in either hemisphere, greatest morning elongations are least favorable in late winter and early spring, and greatest evening elongations are least favorable in late summer and early autumn.
Since it’s now late summer for the Southern Hemisphere, southern climes get to enjoy a ringside seat to this morning apparition of Mercury; and since it’s now late winter in the Northern Hemisphere, northerly latitudes must be content with a seat in the bleachers.
Bottom line: Late February 2015 is a great time to look for Mercury before dawn! The planet’s greatest western elongation falls on February 24, 2015.
EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store
Donate: Your support means the world to us
from EarthSky http://ift.tt/1CP1Lnm
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