Understanding Summer Solstice Astronomy
A solstice is an event where a planet’s poles are extremely inclined towards or away from the star, it orbits around. On earth, solstices are defined by a solar declination or the latitude of the Earth where the sun stands directly overhead the moon. Solstices are phenomena that happen twice yearly, on earth where solar declination reaches the Tropic of Cancer and the Tropic of Capricorn in the north and south, respectively. The summer solstice happens two times during a year. Once, it happens when the path of the Sun is farthest north in the sky in the Northern Hemisphere (June 20 or 21). It happens the second time when the path of the Sun is farthest south in the sky in the Southern Hemisphere (December 21 or 22).
[Image will be Uploaded Soon]
During Summer Solstice in the sky, the Sun travels the longest distance and the daylight is maximum that day. When the solstice happens in the Northern Hemisphere, the North Pole is tilted for about 23.4 degrees towards the Sun. Due to this, the Sun’s rays are slightly shifted from the Equator towards the north by the same amount it is tilted. During that time, the vertical noon rays stand directly overhead the Tropic of Cancer.
When the second solstice happens six months later, the South Pole is inclined towards the Sun by about 23.4 degrees. This day, when the summer solstice happens over the Southern Hemisphere, the Sun’s vertical rays overhead move towards the southernmost position near the Tropic of Capricorn.
What is Summer Solstice Definition Astronomy?
There are few astronomical definitions and explanations of the season according to the planetary position. According to the season’s astronomical definition, the summer solstice marks the beginning of the summer season. It lasts till 22nd or 23rd September in the Northern Hemisphere, or 20th or 21st March in the Southern Hemisphere, until the autumnal equinox. In Scandinavia, Midsummer’s Eve is celebrated during the summer solstice which is evidence of the fact that this day is celebrated in a lot of cultures.
Many cultures around the world celebrate the longest day and shortest night of the year, which is the summer solstice. This day is traditionally celebrated throughout the world across cultures with festivals and bonfires.
When Earth reaches a point in its orbit around the North Pole where it is angled closest to the sun, Astronomers are able to calculate the exact moment of solstice. Six months from this time, the sun will reach the southernmost point and pass overhead the Tropic of Capricorn. During this time the people in the Northern Hemisphere are going to experience the shortest days of the year, in their winter solstice.
The sun’s angle in relation to the Earth’s equator moves gradually so close to the solstices that the shift is difficult to detect for about 10 days without any technical instruments. “Solar standstill” is the origin of the word ‘solstice’, due to the unique position of the Sun.
The Earth’s atmosphere bends some amount of light over the horizon depending on the present weather. This phenomenon can introduce some changes of more than one minute to sunrise and sunset times. The calculation of the minutes done here is an approximation. The slow shift of the sun’s angle to the Earth’s equator means that 20th June is about a second longer than 19th June at the mid-northern latitudes.
Solved Examples
Q1. When Does Summer Solstice Occur During the Year?
Answer: In the Northern Hemisphere, the summer solstice occurs on 20th or 21st June and in the Southern Hemisphere it occurs on 21st or 22nd December.
Q2. Why is the Summer Solstice Important?
Answer: Most of the daylight is received by the Northern Hemisphere than any other day during the summer solstice. Apart from that, it also marks the beginning of the summer season, according to the astronomical definition.
FAQs on Summer Solstice Astronomy
1. What is the summer solstice from an astronomical perspective?
From an astronomical perspective, the summer solstice is the precise moment when one of Earth's poles has its maximum tilt toward the Sun. This event marks the start of summer in that hemisphere. During the summer solstice in the Northern Hemisphere, the Sun reaches its highest and northernmost point in the sky, directly over the Tropic of Cancer. This results in the longest period of daylight and the shortest night of the year.
2. What is the scientific reason behind the occurrence of the summer solstice?
The scientific reason for the summer solstice is Earth's axial tilt, which is approximately 23.5 degrees. As Earth revolves around the Sun, this tilt means that different parts of the planet receive more direct sunlight at different times of the year. The summer solstice occurs when the hemisphere's tilt is most inclined towards the Sun, causing the sun's rays to hit that part of the Earth more directly and for a longer duration.
3. How does the summer solstice differ between the Northern and Southern Hemispheres?
The summer solstice occurs at opposite times of the year for the two hemispheres due to Earth's axial tilt.
- When the Northern Hemisphere is tilted towards the Sun, it experiences its summer solstice, typically around June 20-21.
- Simultaneously, the Southern Hemisphere is tilted away from the Sun, causing it to experience its winter solstice (shortest day of the year).
- Conversely, when the Southern Hemisphere experiences its summer solstice around December 21-22, the Northern Hemisphere experiences its winter solstice.
4. What are the main effects of the summer solstice on Earth?
The primary effect of the summer solstice is the change in the duration of daylight. In the hemisphere experiencing it, the summer solstice brings:
- The longest day and the shortest night of the year.
- The beginning of the astronomical summer season.
- The Sun appearing at its highest point in the sky at noon.
- More direct and intense solar radiation, which leads to warmer temperatures and the summer season.
5. Is the Earth closest to the Sun during the summer solstice?
No, this is a common misconception. The seasons are caused by Earth's axial tilt, not its distance from the Sun. In fact, the Earth is actually near its farthest point from the Sun (an event called aphelion) during the summer solstice in the Northern Hemisphere. The nearness to the sun (perihelion) occurs in early January, during the Northern Hemisphere's winter.
6. How is the summer solstice different from an equinox?
The key difference lies in the Earth's tilt relative to the Sun. During a solstice, one hemisphere is maximally tilted towards the Sun, leading to the longest or shortest day. In contrast, during an equinox (which occurs in spring and autumn), the Earth's tilt is neither towards nor away from the Sun. The Sun is directly over the equator, resulting in nearly equal lengths of day and night across the entire globe.
7. Why does the date of the summer solstice change slightly, sometimes falling on June 20, 21, or 22?
The date of the summer solstice varies slightly because of the mismatch between the Earth's orbit and our calendar system. The Gregorian calendar has 365 days in a standard year, but it takes the Earth approximately 365.24 days to orbit the Sun. To account for this extra fraction of a day, we add a leap day every four years. This adjustment causes the exact time of the solstice to shift back and forth by a day or two over a cycle.
