From solar to lunar: A guide to eclipses and astronomical terms

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TNS

Chandigarh, Updated At : 08:32 PM Sep 09, 2025 IST

A composite image of the phases of a lunar eclipse

Eclipses & related astronomical terms

1. Solar eclipse

• Definition: Occurs when the Moon comes between the Earth and the Sun, casting its shadow on Earth.

• Frequency: 2-5 solar eclipses/year (but total eclipses at any location are rare).

• Types:

Total solar eclipse – Moon completely covers Sun → day turns dark for a short period (only visible in path of totality).

Partial solar eclipse – Only part of the Sun is obscured by Moon.

Annular solar eclipse – Moon is far from Earth, so it appears smaller → Sun looks like a “Ring of Fire” around Moon.

Hybrid eclipse – Rare type, appears total at some places and annular at others.

2. Lunar eclipse

• Definition: Occurs when the Earth comes between Sun and Moon, casting its shadow on the Moon.

• Types:

Total lunar eclipse – Moon fully enters Earth’s umbra (shadow).

Partial lunar eclipse – Only a part of Moon enters umbra.

Penumbral lunar eclipse – Moon passes only through Earth’s penumbra → faint shadow.

• Why Red Moon? – During total lunar eclipse, Earth’s atmosphere scatters shorter blue wavelengths but bends longer red/orange light → Moon appears blood red (“Blood Moon”).

• Frequency: 2-4 lunar eclipses/year.

• Can only occur on Full Moon day.

• Unlike solar eclipse, visible from half of Earth at once.

3. Shadow terminology

• Umbra – Dark central shadow (total eclipse zone).

• Penumbra – Lighter, outer shadow (partial eclipse zone).

• Antumbra – Region where Moon is in front of Sun but appears smaller → creates annular eclipse.

4. Important terms

Ring of Fire

• Phenomenon during Annular Solar Eclipse when Sun appears as a ring around Moon.

• Should not be confused with Pacific Ring of Fire (volcanic belt).

Blood Moon

• Reddish Moon seen during total lunar eclipse due to Rayleigh scattering and atmospheric refraction of sunlight.

Blue Moon

• Term for the second full moon in a calendar month (rare event, every 2-3 years).

• Phrase “once in a blue moon” originates here.

Wolf Moon

• Traditional name for the first full moon of January (used in folklore, almanacs).

Other traditional moon names (value addition):

• Supermoon – When a full moon coincides with perigee (Moon’s closest point to Earth).

• Micromoon – Full moon at apogee (farthest from Earth).

• Harvest Moon – Full moon closest to autumn equinox (September).

• Hunter’s Moon – Full moon after harvest moon (October).

• Strawberry Moon – June’s full moon.

5. Eclipse safety & scientific significance

• Solar eclipses: Must use protective glasses; naked-eye viewing can damage retina.

• Used for studying solar corona.

• Historically used for validating scientific theories (Einstein’s relativity).

Quick comparison table (for revision)

Feature	Solar eclipse	Lunar eclipse
Occurs on	New Moon	Full Moon
Position	Moon between Earth & Sun	Earth between Sun & Moon
Visibility	Only small part of Earth	Entire night side of Earth
Frequency	2-5 times/year	2-4 times/year
Safety	Harmful to view directly	Safe to view with naked eye
Phenomena	Annular, Total, Partial	Total, Partial, Penumbral

Total Lunar Eclipse of September 7-8, 2025 – Overview

What happened?

On the night of September 7-8, 2025, observers across India, Asia, Africa, Europe and Australia were treated to a rare and spectacular total lunar eclipse, commonly referred to as a “Blood Moon” due to its deep red appearance.

Duration & significance

• Totality lasted approximately 82 minutes (1 hour 22 minutes), making it one of the longest total lunar eclipses in the past decade.

• The entire eclipse event spanned over five hours, including penumbral and partial phases.

Timing in India (IST)

• Penumbral eclipse began: Rs 8.58 pm

• Partial eclipse began: Rs 9.57 pm

• Totality began: Rs 11.01 pm

• Maximum eclipse: Rs 11.41 pm

• Totality ended: Rs 12.22 am (September 8)

• Partial ended: Rs 1.26 am

• Penumbral ended: Rs 2.25 am

The “Blood Moon” phenomenon

The Moon turned a striking reddish or coppery hue—a classic “Blood Moon.” This is caused by Earth’s atmosphere filtering and refracting sunlight, which scatters shorter blue wavelengths and allows longer red wavelengths to reach the Moon.

From solar to lunar: A guide to eclipses and astronomical terms

Ravneet Kaur

TNS

Eclipses & related astronomical terms

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