On the night of December 30-31, 2024, an astronomical phenomenon known as the Black Moon will take place. In fact, it’s just a phase of the new moon that will be observed for the second time in a calendar month. It sounds confusing, so let’s break it down together!
The last new moon of the year
On the night of January 30-31, the last day of 2024, the Earth will see a new moon for the second time in December. More precisely, it will not be observed, because, according to the definition of this phase, it will be completely turned to us with its dark side at that moment, and it will be impossible to see it.
It is worth remembering that this will still be the same side that we usually see. It’s just that this time the Sun won’t be shining on it at all. This moment will not last long, and we will see the new moon on New Year’s Eve.
What is the Black Moon
Formally, each new moon can be called “black,” but in reality, this term has a much narrower definition. It is important to say that it is not astronomical. It came from the American Farmers’ Almanac many decades ago. This publication specialized in advice to farmers and therefore paid a lot of attention to the phases of the Moon, as people believed that they affected crops, although this was not the case. You can read more about this in our new issue.
According to the Farmers’ Almanac, a Black Moon is the third new moon in a season in which such a phase is observed four times. It should be noted that this definition uses astronomical seasons rather than calendar seasons.
They are counted between the solstices and equinoxes: winter lasts from the winter to the spring solstice (in March), spring from the spring to the summer solstice (in June), summer from the summer to the autumn solstice (in September), and winter from the autumn to the winter solstice (in December).
The duration of astronomical seasons varies slightly throughout the year. The phases of the Moon change with a period of 29 days. This means that in most astronomical seasons there are only three new moons. However, sometimes the dates coincide so there are four of them because they are not tied to specific calendar dates. Then the third of them is considered the Black Moon.
Current definition
People still use the definition given above. However, it is then clarified that this refers to the seasonal Black Moon. It occurs every 33 months, and the astronomical event on December 31 will not be one, because it is the first new moon of astronomical winter. The next seasonal Black Moon is expected on August 23, 2025.
The new moon in December 2024 will be Black according to a more modern definition. According to it, a dark phase that occurs for the second time in one calendar month should be considered Black. On December 1, our satellite was already in this phase, so now it should be called that way.
It’s important to note that, as with the seasons, this definition is artificial and has no significance for astronomers. It’s just that the calendar and the rotation of this celestial body around the Earth interact in this way. During these events, our satellite does not have any special impact on the planet’s surface.
In addition, there is another definition of the Black Moon. However, it does not refer to our luminary, but to one of the 12 calendar periods, if no full moon is observed during it. Since only February has a shorter duration than the period of our satellite’s phase change, it is the only month that can be a Black Moon according to this definition, but it happens once every many years.
Ghost Moon
Although our satellite itself will not be visible during the dark phase, it will be possible to observe one interesting phenomenon associated with it. If the sky is clear on the first night of the new year, i.e. from January 1 to January 2, you will be able to see the ghost of the Moon.
By this time, our satellite should have turned into a very thin sickle, but the rest of its surface will also be visible as a ghost. This is the so-called da Vinci glow or the ashen light of the Moon. It is observed before and after each new moon, but this time the time for observations will be very good.
There is nothing mysterious about the da Vinci glow. It is simply the light of the Sun reflecting off the Earth and illuminating our satellite. At one time, it was thanks to it that it was determined that the surface of the Moon is relatively hard. But we may be interested in it as a decoration of the New Year’s sky.
