What is the phase of Mercury today?
Today, on September 16, 2024, Mercury is in its waxing gibbous phase and is 86% illuminated.
Understanding the phases of Mercury
If you look through a telescope from the earth, you will see that Mercury exhibits a full range of phases, like our moon.
Mercury exhibits a full range of phases because it passes between the sun and the earth as it orbits the sun.
Like the moon, Mercury also exhibits a total of eight phases. In order, these phases are: new Mercury, waxing crescent, first quarter, waxing gibbous, full Mercury, waning gibbous, third quarter, and waning crescent.
However, there is one major difference between the phases of the moon and the phases of Mercury.
As the moon orbits around the earth, we see almost the same disk size of the moon throughout its phases. However, we don’t see the same disk size of Mercury throughout its phases from the earth as it orbits around the sun.
Mercury takes about 88 days to orbit the sun with respect to the background stars, called the sidereal period of Mercury. However, Mercury takes about 116 days to orbit the sun with respect to the earth, as the earth is also moving in its orbit, called the synodic period of Mercury. So Mercury takes about 116 days to complete a phase cycle, i.e., to go from its one “new” phase to the next “new” phase.
Waxing gibbous: September 6 to September 30
The waxing gibbous phase of Mercury started on September 6, 2024, and will end on September 30, 2024.
Mercury is in its waxing gibbous phase when it continues to recede from Earth after its first quarter phase. During this time, the illuminated area of Mercury continues to increase, and its disk size continues to decrease until it becomes a full Mercury.
The illuminated area of Mercury increases from 50% to 100%, and its phase angle, i.e., the angle between the sun, Mercury, and the earth, decreases from 90° to 0° during its waxing gibbous phase.
Mercury is visible in the eastern sky preceding sunrise as it rises before sunrise and sets before sunset during its waxing gibbous phase. However, as the days of Mercury increase in the waxing gibbous phase, it becomes harder to observe.
Full Mercury: September 30
The full phase of Mercury will fall on September 30, 2024.
Mercury is in its full phase when it is located on the opposite side of the sun with respect to the earth in its orbit, called the superior conjunction of Mercury. During this time, Mercury is almost invisible, brightest, and smallest in size.
Mercury is almost invisible because it disappears in the sun’s glare behind the sun on our sky’s dome, brightest because the side of Mercury that faces our Earth is fully illuminated, and smallest because it is farthest from our Earth.
The illuminated area of Mercury becomes 100%, and its phase angle, i.e., the angle between the sun, Mercury, and the earth, becomes 0° during its full phase.
Mercury rises and sets with the sun during its full phase.
Waning gibbous: September 30 to November 21
The waning gibbous phase of Mercury will start on September 30, 2024, and end on November 21, 2024.
Mercury is in its waning gibbous phase when it approaches the earth after the superior conjunction position. During this time, the illuminated area of Mercury decreases and its disk size increases until it becomes a third quarter Mercury.
The illuminated area of Mercury decreases from 100% to 50%, and its phase angle, i.e., the angle between the sun, Mercury, and the earth, increases from 0° to 90° during its waning gibbous phase.
Mercury is visible in the western sky following sunset as it rises after sunrise and sets after sunset during its waning gibbous phase. However, as the days of Mercury increase in the waning gibbous phase, it becomes easier to observe.
Third quarter (half Mercury): November 21
The third quarter phase of Mercury will fall on November 21, 2024.
Mercury is in its third quarter phase when it is three-quarters away from the inferior conjunction position in its orbit.
The illuminated area of Mercury becomes 50% and its phase angle i.e. the angle between the sun, Mercury, and the earth becomes 90° during its third quarter phase.
Mercury is visible in the western sky following sunset as it rises after sunrise and sets after sunset during its third quarter phase. Mercury is easiest to observe in the evening sky around the time of its third quarter phase.
Waning crescent: November 21 to December 6
The waning crescent phase of Mercury will start on November 21, 2024, and end on December 6, 2024.
Mercury is in its waning crescent phase when it continues to approach the earth after its third quarter phase. During this time, the illuminated area of Mercury continues to decrease, and its disk size continues to increase until it becomes a new Mercury.
The illuminated area of Mercury decreases from 50% to 0% and its phase angle i.e. the angle between the sun, Mercury, and the earth increases from 90° to 180° during its waning crescent phase.
Mercury is visible in the western sky following sunset as it rises after sunrise and sets after sunset during its waning crescent phase. However, as the days of Mercury increase in the waning crescent phase, it becomes harder to observe.
New Mercury: December 6
The new phase of Mercury will fall on December 6, 2024.
Mercury is in its new phase when it passes between the sun and the earth in its orbit, called the inferior conjunction of Mercury. During this time, Mercury is almost invisible, dimmest, and largest in size.
Mercury is almost invisible because it disappears in the sun’s glare in front of the sun on our sky’s dome, dimmest because the side of Mercury that faces our Earth is in complete darkness, and largest because it is closest to our Earth.
The illuminated area of Mercury becomes 0% and its phase angle i.e. the angle between the sun, Mercury, and the earth becomes 180° during its new phase.
Mercury rises and sets with the sun during its new phase.
Waxing crescent: December 6 to December 20
The waxing crescent phase of Mercury will start on December 6, 2024, and end on December 20, 2024.
Mercury is in its waxing crescent phase when it recedes from Earth after the inferior conjunction position. During this time, the illuminated area of Mercury increases and its disk size decreases until it becomes a first quarter Mercury.
The illuminated area of Mercury increases from 0% to 50% and its phase angle i.e. the angle between the sun, Mercury, and the earth decreases from 180° to 90° during its waxing crescent phase.
Mercury is visible in the eastern sky preceding sunrise as it rises before sunrise and sets before sunset during its waxing crescent phase. However, as the days of Mercury increase in the waxing crescent phase, it becomes easier to observe.
First quarter (half Mercury): December 20
The first quarter phase of Mercury will fall on December 20, 2024.
Mercury is in its first quarter phase when it is one quarter away from the inferior conjunction position in its orbit.
The illuminated area of Mercury becomes 50%, and its phase angle, i.e., the angle between the sun, Mercury, and the earth, becomes 90° during its first quarter phase.
Mercury is visible in the eastern sky preceding sunrise as it rises before sunrise and sets before sunset during its first quarter phase. Mercury is easiest to observe in the morning sky around the time of its first quarter phase.
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