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New moon
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Diagram showing the phases of the Moon as it orbits Earth, with labeled positions for new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. The Sun is on the right, and arrows illustrate sunlight direction, while angles indicate the Moon's position relative to Earth and Sun at each phase. Dancers in bright traditional costumes and floral headpieces perform outdoors during the Lantern Festival celebration, with onlookers and trees in the background.
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Diagram showing the phases of the Moon as it orbits Earth, with labeled positions for new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. The Sun is on the right, and arrows illustrate sunlight direction, while angles indicate the Moon's position relative to Earth and Sun at each phase.
Lunar phases Phases of the Moon as it orbits Earth, showing the angle formed by the position of the Moon with respect to the Sun at each phase.

New moon

lunar phase
Written by
Erik Gregersen
Erik Gregersen is a senior editor at Encyclopaedia Britannica, specializing in the physical sciences and technology. Before joining Britannica in 2007, he worked at the University of Chicago Press on the...
Erik Gregersen
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Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
Britannica Editors
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•History
Top Questions

What is a new moon?

How often does a new moon occur?

Why don’t solar eclipses occur at every new moon?

How do lunisolar calendars use the new moon?

What role does the new moon play in the Islamic calendar?

New moon, one of eight lunar phases, in which the Moon is between Earth and the Sun, and thus the side of the Moon that is in shadow faces Earth. The new moon is traditionally regarded as the first phase in the lunar cycle.

The cycle of lunar phases lasts close to a month, at 29.5 days, a period known as the synodic month. Thus, the new moon typically occurs once per calendar month, but when two new moons occur in a calendar month, the second is referred to as a “black moon.”

Solar eclipses happen at new moons, when the Moon blocks the light of the Sun as seen from Earth. A solar eclipse does not occur at every new moon because the Moon’s orbital plane is inclined to the ecliptic, the plane of the orbit of Earth around the Sun. The angle between the planes is about 5°; thus, the Moon can pass well above or below the Sun.

Dancers in bright traditional costumes and floral headpieces perform outdoors during the Lantern Festival celebration, with onlookers and trees in the background.
Lantern FestivalDancers perform during a ceremony in celebration of the Lantern Festival, which marks the end of Lunar New Year festivities in Yantai, in eastern China's Shandong province on February 26, 2021.

In cultures with lunisolar calendars, months are determined by the phase of the Moon, and the year is determined by the Sun. Festivals in such cultures are often determined by the new moon. The Lunar New Year is celebrated in China and other Asian countries and marks the first new moon of the calendar. In the Jewish calendar, months begin with the new moon, and Rosh Hashanah, which marks the beginning of the High Holy Days, happens with the new moon marking a new year. In the Islamic calendar, months also begin with the new moon, and thus that phase determines when Ramadan, the month of fasting, begins and ends.

Erik Gregersen