This weekend presents an extraordinary chance to catch a glimpse of the smallest planet in our solar system, Mercury, with your naked eye. On Friday, September 22, this elusive planet, also known as the ‘Swift Planet’ due to its rapid 88-day orbit around the sun, will reach its highest point in the sky for the year while transitioning to its half-lit phase. Located incredibly close to the sun, Mercury is often obscured by the sun’s glare, making it virtually invisible in the daytime sky for most of the year. However, this weekend, the celestial body will make a rare appearance during twilight hours, close to sunrise or sunset on Earth.
This exceptional viewing opportunity coincides with Mercury’s ‘greatest elongation,’ a point in its orbit when it seems farthest from the sun, as observed from Earth. On September 22, Mercury will experience its greatest elongation west, making it visible above the eastern horizon just before sunrise. Moreover, the planet will display a ‘dichotomy,’ appearing half-lit, akin to the moon at its first or last quarter phase. According to experts, Mercury will be at its brightest and easiest to spot in the morning sky from September 16 to September 30, peaking about 30 minutes before sunrise from September 22.
A Rare Chance to Spot Mercury, the ‘Swift Planet’
Mercury at Its Prime Visibility
This weekend, stargazers are in for a treat as Mercury, the smallest planet in our solar system, will reach its highest point in the sky all year on Friday, Sept. 22. Known as the ‘Swift Planet’ due to its rapid 88-day orbit around the sun, Mercury is usually lost in the sun’s glare due to its close orbit. Despite being technically present in the daytime sky nearly all year, it is often impossible to see. However, this week, the planet will be visible during twilight close to sunrise or sunset on Earth.
Understanding Mercury’s ‘Greatest Elongation’
The upcoming visibility of Mercury is attributed to its ‘greatest elongation’, which refers to a point in its orbit when the planet appears farthest from the sun, as observed from Earth. This phenomenon occurs both in the east, when it’s visible above the western horizon just after sunset, and in the west, marking its visibility above the eastern horizon just before sunrise. On Sept. 22, Mercury’s greatest elongation west will occur, and the planet will also appear half-lit — a phase known as its ‘dichotomy’, similar to the moon at its first or last quarter phase.
Best Time to Spot Mercury
As per In-The-Sky.org, Mercury will be well placed for viewing before sunrise throughout the week, soaring as high as 17 degrees above the eastern sky. The planet is expected to be brighter and easier to see in the days following its highest point in the sky, when it will display a gibbous phase – appearing more than half-lit. According to Space.com, from Sept. 16 to Sept. 30, Mercury will be at its brightest and easiest to spot in the morning sky. For optimal viewing, it is suggested to look for it about 30 minutes before sunrise from Sept 22 through early next week, with a clear, unobstructed horizon. A pair of stargazing binoculars could also come in handy to spot Mercury, which usually has a yellow tinge.
Locating Mercury in the Sky
For those keen to witness this spectacle, use TimeAndDate.com’s Night Sky Map & Planets Visible Tonight page to find the exact time of Mercury’s rise for your location. Venus, shining brightly above, and the bright star Regulus in the constellation Leo situated between the two planets, will serve as helpful markers.
Following this spectacle, the next greatest elongation east of Mercury will occur on Dec. 4, 2023, when it will be visible in the evening after sunset.
This rare visibility of Mercury provides an excellent opportunity for astronomy enthusiasts and casual observers alike to view the smallest planet in our solar system. The event underscores the fascinating dynamics of celestial bodies and their orbits. Whether you’re a seasoned stargazer or a curious novice, don’t miss this chance to witness Mercury’s ‘greatest elongation’.