Which one of the following statements about syzygy and related eclipse conditions in the Sun–Earth–Moon system is NOT correct?

Introduction / Context:
Syzygy is an important concept in astronomy and celestial mechanics, referring to special alignments of celestial bodies. In the context of the Earth–Moon–Sun system, syzygy is closely associated with New Moon, Full Moon, and eclipse conditions. This question provides four statements about syzygy and asks which one is not correct, so you must evaluate each statement carefully based on what you know about lunar phases and eclipses.

Given Data / Assumptions:

• Syzygy refers to an approximate straight line alignment of three celestial bodies, often the Sun, Earth and Moon.
• Conjunction refers to a New Moon syzygy, with the Moon near the Sun as seen from Earth.
• Opposition refers to a Full Moon syzygy, with the Moon opposite the Sun in the sky.
• Perihelion is the point in Earth orbit when it is closest to the Sun and occurs once per year.

Concept / Approach:
In the Sun–Earth–Moon system, syzygy occurs when the three bodies are nearly in a straight line. At New Moon, the Moon is between Earth and Sun; at Full Moon, Earth is between Sun and Moon. Eclipses are special cases of syzygy where the alignment passes close to the orbital nodes. Solar eclipses occur at New Moon when the Moon’s shadow falls on the Earth, and lunar eclipses occur at Full Moon when the Earth’s shadow falls on the Moon. Statements A, B, and C are consistent with these definitions: syzygy is the nearly straight line alignment; syzygy at conjunction can lead to a solar eclipse; syzygy at opposition can lead to a lunar eclipse if the alignment is favourable. Statement D incorrectly restricts syzygy conjunction to Earth perihelion only. In reality, New Moon syzygies occur approximately once every lunar month, independent of Earth perihelion. Perihelion is not a requirement for syzygy or eclipses. Therefore, statement D is not correct.

Step-by-Step Solution:

Verification / Alternative check:
Lunar phase calendars show that New Moon (conjunction) and Full Moon (opposition) occur roughly every 29.5 days. Eclipses occur only when these phases coincide with the Moon being near one of its nodes. Astronomical data shows that Earth perihelion occurs once per year in early January and does not control the monthly pattern of syzygies. Textbooks describing eclipses and syzygy do not tie conjugation syzygy exclusively to perihelion. These facts confirm that statements A, B, and C conform to standard definitions and that statement D incorrectly restricts syzygy conjunction to perihelion.

Why Other Options Are Wrong (i.e., actually correct statements):

The alignment of the Sun, Earth and Moon in a nearly straight line of about 180 degrees is called syzygy is a correct definition of syzygy in the context of the Earth–Moon–Sun system.

Syzygy conjunction (New Moon in line with the Sun) can cause a solar eclipse when the alignment is near a node is correct because solar eclipses occur at New Moon syzygy when geometric conditions are satisfied.

Syzygy opposition (Full Moon opposite the Sun) can cause a lunar eclipse when the alignment passes near a node is correct because lunar eclipses occur at Full Moon syzygy when the Earth lies between the Sun and Moon.

Common Pitfalls:
Students may be unfamiliar with the term syzygy and may focus on eclipse details, or they may find the mention of perihelion in statement D attractive because it sounds technical. Another pitfall is forgetting that New Moons and Full Moons occur monthly, not just once a year. To avoid confusion, remember that syzygy refers to alignments during New Moon and Full Moon, which happen regularly, while perihelion is a separate orbital event that does not control syzygy. Therefore, statement D is the incorrect one.

Final Answer:
The statement that is NOT correct is “Syzygy conjunction occurs only at the time of Earth perihelion around the Sun and not at other times.”