What is a solar eclipse? How it happens and how to watch it safely
By the WhyCosmos team · Last updated:
A solar eclipse happens when the Moon passes directly between the Sun and Earth and blocks some or all of the Sun's light for a short time. It can occur only at new moon. Depending on the alignment, people see a total, partial or annular eclipse. In Hindi a solar eclipse is called surya grahan.
A solar eclipse is one of the few moments when the ordinary geometry of orbits becomes something a child can watch happen. It is also the one sky event that can genuinely damage a child's eyes if handled wrongly, so this page puts the safety rules in plain language alongside the science, and lists the next solar eclipses visible from India.
How to explain it to your child
Explain it to an 8-year-old
Shine a torch at a wall and move a ball in front of it: the ball's shadow lands on the wall. In a solar eclipse, the Sun is the torch, the Moon is the ball and Earth is the wall. For a few minutes the Moon's shadow falls on part of Earth, and people standing in that shadow see the Sun disappear behind the Moon.
Explain it to a 13-year-old
A solar eclipse occurs at new moon when the Moon crosses the line between the Sun and Earth closely enough for its shadow to reach Earth's surface. Inside the narrow dark core of the shadow, the umbra, the Sun is completely covered: a total eclipse. In the wider outer shadow, the penumbra, it is only partly covered. When the Moon is near the farthest point of its orbit, it looks slightly too small to cover the Sun and leaves a bright ring: an annular eclipse.
Key facts
| What causes it | The Moon passes between the Sun and Earth |
|---|---|
| Can happen only at | New moon |
| Main types | Total, partial and annular |
| Longest possible totality | About 7.5 minutes at any one place |
| Why the small Moon can cover the Sun | The Sun is about 400 times wider than the Moon but also about 400 times farther away |
| Safe to look at directly? | No. Use certified ISO 12312-2 eclipse glasses or a pinhole projector |
| Hindi name | Surya grahan |
| Next one visible from India | A partial solar eclipse on 2 August 2027 |
What are the types of solar eclipse?
| Type | What happens | What you see |
|---|---|---|
| Total | The Moon covers the Sun's bright disc completely, for people inside a narrow track called the path of totality | Daylight fades to deep twilight, bright stars and planets appear, and the Sun's pearly outer atmosphere, the corona, comes into view |
| Annular | The Moon is near its farthest from Earth and looks slightly smaller than the Sun | A bright "ring of fire" around the dark Moon; the sky never gets truly dark |
| Partial | The Moon covers only part of the Sun | A dark "bite" out of the Sun; this is what most people outside the central path see |
The Moon can hide the far larger Sun because of a remarkable coincidence of numbers: the Sun is about 400 times wider than the Moon and also about 400 times farther away, so the two look almost exactly the same size in our sky.
Why don't solar eclipses happen every month?
The Moon's orbit is tilted by about 5 degrees compared with Earth's orbit around the Sun. At most new moons the Moon passes a little above or below the Sun from our point of view, and its shadow misses Earth completely. An eclipse happens only when new moon falls close to one of the two points where the Moon's orbit crosses Earth's, which happens during two windows each year called eclipse seasons.
Somewhere on Earth sees between two and five solar eclipses every year, but the Moon's shadow covers only a small area each time, so any single town may wait centuries for a total eclipse of its own.
How do you watch a solar eclipse safely?
- Never look at the Sun directly, even when most of it is covered. The thin crescent that remains is bright enough to burn the retina, and the damage is painless at the time.
- Ordinary sunglasses, X-ray film, smoked glass and photo negatives are not safe. Use eclipse glasses that meet the ISO 12312-2 standard, bought from a reputable source, and check them for scratches before use.
- Never point a camera, binoculars or a telescope at the Sun without a proper solar filter fitted over the front. They concentrate sunlight and can cause instant eye injury, even if the viewer is wearing eclipse glasses.
- The safest method for children is projection. Make a small hole in a piece of card and let sunlight pass through it onto a second card or the ground: you will see a tiny image of the eclipsed Sun. Gaps between leaves under a tree do the same thing naturally.
- Only during totality, when the Sun's bright disc is completely hidden, is it safe to look with the naked eye, and the protection must go back on the moment the first bright edge reappears. An annular eclipse never reaches this stage, so eyes stay protected throughout.
Children should always watch under the supervision of an adult who knows these rules.
When is the next solar eclipse visible from India?
India's most memorable recent solar eclipses were the total eclipse of 22 July 2009, whose path of totality crossed the country from Gujarat to Arunachal Pradesh, and the annular "ring of fire" eclipses of 26 December 2019 in the south and 21 June 2020 in the north. These are the next ones visible from India:
| Date | What India sees | Note |
|---|---|---|
| 2 August 2027 | Partial | Late afternoon; total along a path through North Africa and the Middle East |
| 22 July 2028 | Small partial | Only from parts of southern India, just after sunrise; total in Australia and New Zealand |
| 1 June 2030 | Partial | Annular elsewhere |
| 21 May 2031 | Annular | The annular path crosses India |
| 3 November 2032 | Partial | |
| 20 March 2034 | Total | The next total solar eclipse whose path of totality crosses India |
Dates are from timeanddate.com's eclipse tables for India. How much of each eclipse you see depends on your city, so check local timings closer to the date.
Why do eclipses matter to scientists?
A total eclipse is the only time the Sun's faint outer atmosphere, the corona, can be seen clearly from the ground, and eclipses have made scientific history. During the total eclipse of 18 August 1868, observed from Guntur in present-day Andhra Pradesh, the French astronomer Jules Janssen recorded a bright yellow line in the spectrum of the Sun's prominences that was later traced to a new element, helium.
Today India's Aditya-L1 carries a coronagraph that blocks the Sun's bright disc with a disc of its own, creating an artificial eclipse so that scientists can study the corona every day. Solar and lunar eclipses are part of lesson 4 of Astronomy 101, the WhyCosmos live course for ages 8 to 16.
Questions parents and kids ask
It is when the Moon moves exactly between the Sun and Earth and blocks the Sun's light for a short time, so a part of Earth falls into the Moon's shadow.
Yes. Looking at the partly covered Sun without certified protection can burn the retina, often without any pain at the time, and the damage can be permanent. Use ISO 12312-2 eclipse glasses or a pinhole projector, never ordinary sunglasses.
The whole event, from the Moon's first bite to its last, usually lasts two to three hours. Totality at any one place lasts at most about 7.5 minutes, and often only two or three.
No. The Moon's dark central shadow covers only a narrow path, usually less than about 250 kilometres wide. People outside it see a partial eclipse, and people on the night side of Earth see nothing at all.
In a solar eclipse the Moon blocks the Sun; it happens at new moon, in the daytime. In a lunar eclipse Earth's shadow falls on the Moon; it happens at full moon, at night. A lunar eclipse is safe to watch with the naked eye, a solar eclipse is not.
A partial solar eclipse on 2 August 2027 will be visible from India in the late afternoon. The next annular eclipse whose path crosses India is on 21 May 2031, and the next total solar eclipse whose path crosses India is on 20 March 2034.
Your child asks questions like this every week.WhyCosmos runs live online astronomy classes for ages 8–16, taught by real astrophysicists — where questions like these are the curriculum.
Related terms in this glossary
Sources and further reading
NASA: Types of eclipses · NASA: Eclipse safety · timeanddate.com: Next eclipses in India