Font size:
Print
Super Blue Moon
Context:
Recently, the full moon day (Purnima) coincided with the sighting of a ‘super blue moon’.
More on news:
- This rare astronomical event occurs when the full moon is both a “blue moon” and a “super moon,” creating a “Super Blue Moon,” a unique combination of three astronomical phenomena.
- NASA explains that in many traditional lunar calendars, full moons typically occur around the middle of each month.
What is a super moon?
- The moon’s orbit around the Earth is not perfectly circular but elliptical, meaning it’s elongated or stretched out.
- It takes the moon 27.3 days to complete one orbit around the Earth. However, it takes 29.5 days between new moons because, as the moon orbits the Earth, both the Earth and the moon are also moving around the sun.
- This additional movement requires extra time for the sun to illuminate the moon in the same way it does at the beginning of each revolution around the Earth.
- The new moon, the opposite of the full moon, is the darkest phase when the illuminated side of the moon faces away from the Earth and is invisible.
- The closest point to Earth in the moon’s elliptical orbit is called perigee, while the farthest point is known as apogee.
- A super moon occurs when the moon is near or at its perigee and is also a full moon.
- Although a super moon can also occur with a new moon, it is not visible.
- A full moon happens when the moon is directly opposite the sun, as viewed from Earth, with its entire dayside illuminated.
- The full moon appears as a bright circle in the sky, rising around sunset and setting around sunrise.
- The moon appears “full” not only on Purnima but also on the nights before and after the full moon.
What is a blue moon?
- While the phrase “once in a blue moon” suggests something rare or unusual, a blue moon is not as uncommon as it might seem.
- The most widely understood definition, and the one endorsed by NASA, describes a blue moon as occurring when two full moons appear within a single month.
- Since the cycle from one new moon to the next lasts 29.5 days, occasionally, a full moon will appear at the beginning of a month, allowing enough time for a second full moon to occur before the month ends.
- This typically happens when the first full moon appears on the 1st or 2nd of the month, leading to a second full moon on the 30th or 31st. According to NASA, this phenomenon occurs every two to three years.
- Another accepted definition of a blue moon is based on the astronomical seasons, which are periods between a solstice and an equinox.
- For example, the current astronomical summer began with the summer solstice on June 21 and will end with the autumn equinox on September 22.
- The Maine Farmers’ Almanac in 1937 defined a blue moon as the third full moon in a season that has four full moons.
Does the Super Blue Moon actually appear blue?
- No, the term “blue moon” has nothing to do with the moon’s colour.
- Sometimes, smoke or dust in the air can scatter red wavelengths of light, making the moon appear bluer than usual in certain locations.
Will the super moon be bigger in size?
- According to NASA, a full moon at perigee (a super moon) appears about 14% larger and 30% brighter than a full moon at apogee (known as a “micro moon”).
- Approximately 25 percent of all full moons are super moons, while only 3 percent are blue moons.
- The interval between super blue moons is irregular, ranging up to 20 years, but on average, it occurs every 10 years.
- The difference in size is unlikely to be noticeable to most people. However, the moon may appear somewhat brighter, though your ability to perceive this difference will depend on factors such as the “Moon illusion” and the level of cloud cover or pollution at your location.
