July

July is the 7th month in both the Julian and Gregorian calendar. It has 31 days, and is one of the hotter months of the year in the northern hemisphere. We are going to discuss a little about the naming of the month.

In the Roman calendar, there used to be only 10 months, and July was the fifth month. It was original named Quintilis, which is Latin for fifth. When the Roman calendar changed to a 12-month calendar, it retained the name Quintilis. We will see more of this later on when we talk about the final four months of the year.

In 45 BCE, when the Julian calendar was introduced, then Roman dictator Julius Caesar had the calendar created to follow more along the lines of the actual orbit of the Sun. When he was assassinated the following year, they renamed Quintilis Julius after Caesar, and it was anglicized to July.

June

June is the sixth month in the Julian and Gregorian calendars. It is believed to be named after Juno, the wife of Jupiter or from the Latin iuniores meaning younger ones.


June is important astronomically as it contains the summer solstice for the Northern Hemisphere and the winter solstice for the Southern Hemisphere.


Important June events:
John Couch Adams, co-discoverer of Neptune, was born on June 5, 1819.
Johannes Muller, inventor of astronomical tables, was born on June 6, 1436.
Pope Gregory XIII was born on June 7, 1502.
Giovanni Cassini was born on June 8, 1625.
Johann G Galle, co-discoverer of Neptune, was born on June 9, 1812.

January

January. New Year (well, at least those of you following the Gregorian calendar). New Beginning. New blog post.

Sporadically, throughout the year, I am going to be discussing a little bit about the calendar because the calendar actually is based on astronomical phenomena. For example, the term for one-twelfth of a year is called month, which comes from the name Moon, derived for Proto-Germanic maenon. The division of the year into months comes from the lunar cycle, which is approximately 30 days.

I just want to begin this sporadic series by discussing where the name of January comes from. It is actually derived from the Roman god Ianus (no J's in Latin) who was the god of doorways and passages. He is also known as the two-headed god as he can see forward and also backwards, at the same time. Ianus is a god who can look in the past, yet still see peer ahead to the future. Good name for the month that begins a year.

Blue Moon

Tonight, July 31st, a rare occurrence will happen. You can say that it is something that happens once in a blue moon, because it is a blue moon.


What do we mean by a blue moon? There are actually two definitions of what a blue moon is.

1. A blue moon is the third full moon in a season where four full moons occur. Most times, there are only three full moons in one season, but on the rare occasion when a full moon is at the beginning of the season, the season may have four.
2. A blue moon may also mean the second full moon in a calendar month. The full moon of tonight is this type of blue moon.

Why do blue moons occur and why are they rare? If you go back to when we discussed the lunar cycle and the synodic period of the moon, we know that the time from one full moon to the successive full moon is approximately 29.5 days. Calendar months last anywhere from 28 days to 31 days. Therefore, if a full moon is on the first of a month, that month will have a blue moon (second definition). The seasons are, on average, a little over 90 days. As stated above, if the full moon occurs on the solstice or equinox (or a day after), it is possible to have four full moons in the season.


If you miss the blue moon tonight, don't worry. There will be another blue moon on May 21, 2016. This will be the third blue moon in the northern spring (southern fall) of 2016.