Autumn arrived by the astronomers' calendar this morning, September 23, at 3:05 a.m. Bulgarian time. That's when the Sun crossed the celestial equator at the point of the autumnal equinox, in the constellation Virgo. From here on, it moves along the ecliptic into the southern celestial hemisphere. This was explained to BTA by Pencho Markishki, a physicist at the Institute of Astronomy with the National Astronomical Observatory at the Bulgarian Academy of Sciences and at the Department of Astronomy of the Faculty of Physics at Sofia University "St. Kliment Ohridski."
Right now, the days are shortening at their fastest rate of the year — each one about 2 minutes and 50 seconds shorter than the last, the physicist says.
Markishki is also the author of the "Amateur Astronomer's Guide," published by the Department of Astronomy at Sofia University, and according to him, amateur astronomers will have good conditions this autumn to observe most of the bright planets. Mercury and Venus are currently in the constellation Virgo. Mercury sets shortly after the Sun and is hard to spot. Venus sets later — around 8:10 p.m. for Sofia — and can be glimpsed briefly in the evening twilight, low on the southwestern horizon.
Saturn has already moved into the constellation Cetus, right near its border with Pisces. These evenings it rises around 7:50 p.m. for Sofia and remains visible for the rest of the night. Mars can be seen in Gemini, near Cancer, rising around 1:45 a.m. and staying visible until dawn. Jupiter is near the border between Cancer and Leo and rises around 3:35 a.m. for the capital. Uranus is in Taurus, and Neptune in Pisces, but both planets can only be seen with a telescope.
On September 26, at 7:49 p.m., comes September's full moon. Because of its proximity to the equinox, it is traditionally known as the Harvest Moon, Markishki adds.