Solar Eclipses

Overview

Throughout human history, eclipses – both solar and lunar – have captured the human imagination. Western astronomers have studied total solar eclipses for more than a century, and this has helped shape our knowledge of the Sun’s composition and processes, and it has also deepened our understanding of the Earth and the space environment in which our planet exists.

Eclipses occur when the Sun, Moon and Earth line up, and that alignment can be partial or full. Solar eclipses occur when, in combination with a lunar node (the intersection of the orbital planes of the Sun and Moon), the Moon passes between the Sun and the Earth during a new Moon phase; lunar eclipses occur when the Earth passes between the Sun and the Moon.

This stamp issue presents three types of solar eclipse: partial, total and annular. This issue is being released in the lead-up to a hybrid eclipse (a rare annular–total eclipse), which is due to arrive on 20 April 2023, viewable at 11.29am over a small part of the west coast of Western Australia, the Exmouth peninsula.

Technical specifications

Issue date: 11 April 2023
Issue withdrawal date: 31 October 2023
Denomination: $1.20 x 3
Stamp design: Gary Domoney, VISUA®
Product design: Gary Domoney, VISUA®
Paper: gummed: Tullis Russell 104gsm Red Phos.
Paper: self-adhesive: Domain S/A Securpost MC 90 P11P Non- Phos
Printer: EGO
Printer: self-adhesive: RA
Printing process: Offset lithography
Stamp size (mm): 26 x 37.5
Minisheet size (mm): 170 x 80
Perforations: 14.6 x 13.86
Sheet layout: Module of 50
FDI Postmark: Exmouth WA 6707
FDI withdrawal date: 10 May 2023

Stamps in this issue

$1.20 Annular Solar Eclipse

Second-most common is the annular eclipse, which takes place when the Moon is at its farthest point (apogee) from the Earth on its elliptical orbit of our planet. Because it is at this distant point, it appears smaller (by 14 per cent) than it is when it is at its closest proximity (perigee) to the Earth. This makes the Moon appear smaller than the Sun when it crosses its path, meaning it does not fully block the Sun. In a darkened daytime sky, the Moon will appear as a dark disk superimposed on the larger disk of the Sun, resulting in a ring of fire (annulus) as the Sun shines around the Moon’s circumference.

$1.20 Total Solar Eclipse

Total solar eclipses happen every 18 months or so, but often they will be visible only from remote locations, meaning they are seen by relatively few stargazers. This type of eclipse occurs when the Moon completely blocks the face of the Sun, and those in the centre of the Moon’s shadow when it hits the Earth will experience the phenomenon of “totality”. The sky will darken as the Moon passes in front of the Sun and only the Sun’s corona (outer atmosphere) will be visible around the black disk of the Moon. This white, hazy celestial zone comprises extremely hot particles ejected at high speed from the Sun’s surface.

$1.20 Partial Solar Eclipse

A partial eclipse is the most humble and common of solar eclipses. It occurs when the Moon does not align perfectly with the Sun, so covers only part the Sun. Depending on the “magnitude of eclipse” the sky may darken but day does not turn to night during the event. The magnitude of eclipse refers to the area of the Sun occluded by the Moon: sometimes it appears as if the Moon has bitten just a small piece from the Sun; at other times the occlusion is large, and the Sun appears as a bright, narrow crescent.