First day of spring, final supermoon of 2019 line up on Wednesday

The first day of spring is the last for supermoons in 2019.

Wednesday evening will bring the year's last supermoon, known as the 'full worm moon.”

Coincidentally, it's also the spring (vernal) equinox - one of only two days during the year when most people on earth will see near-exactly 12 hours of day and 12 hours of night. It marks the official beginning of spring, in scientific circles.

The equinox will arrive just before 5 p.m. Wednesday - 4:58 p.m., to be exact.

During a supermoon, the moon can appear bigger and brighter than normal, because the moon is in its closest proximity to earth, also called lunar perigee.

The 'full worm moon” is expected to peak around 8:43 p.m. Wednesday in the Cedar Rapids area.

If you're thinking this supermoon business sounds familiar, it's because we've experienced two supermoons already in 2019. So why is this one called the 'worm moon?”

According to the Old Farmer's Almanac, it's because this is the time of year when the soil starts to thaw and earthworms appear.

Each full moon of the year has a name like this - for example, February was the 'snow moon,” June is the 'strawberry moon” and September is the 'harvest moon.”

Wednesday's supermoon event will be the first time it has coincided so closely with the spring equinox since March 2000, according to EarthSky.org. It won't happen this closely again until March 2030.

According to National Geographic, Wednesday's supermoon will be 223,309 miles from Earth at 2:45 p.m. It won't reach its full phase until 8:43 p.m., appearing 14 percent larger and 12 percent brighter than usual.

Equinox explained

The astronomical start of spring, or the vernal or spring equinox, arrives Wednesday at 4:58 p.m., according to the National Weather Service. The meteorological start of spring, however, began March 1 and is based on 'annual temperature cycles and the Gregorian calendar,” according to AccuWeather.

The spring equinox is the one of just two times per year when 'the Earth's axis is tilted neither toward nor away from the sun, resulting in a ‘nearly' equal amount of daylight and darkness at all latitudes” - about 12 hours and 12 hours - according to the weather service. The other instance, of course, is the autumnal equinox, or the start of fall that will come Sept. 23. The spring equinox means that the days will continue to get longer as the sun rises higher in the sky, eventually bringing the summer solstice on June 21.

Largely because of the Earth's rotation. The planet makes its way around the sun 365.24 days, not exactly 365 days, which is why leap years exist and why the starts of the spring and autumnal equinoxes and summer and winters solstices have varied, according to the National Center for Environmental Information.