This year’s Halloween is special. There are two celestial events that will take place on the last day of the month: Opposition of Uranus and a rare Halloween Blue Moon.
But this has nothing to do with its apparent color or the recent discovery of water on the lunar surface. The second Full Moon of a month is known as the Blue Moon.
Usually, months have only one full moon, but occasionally a second one sneaks in. Full moons are separated by 29 days, while most months are 30 or 31 days long; so it is possible to fit two full moons in a single month. This happens every two and a half years, on average. It’s a rare astronomical phenomenon.
As a matter of fact, every Full Moon on Halloween is a Blue Moon. However, a Full Moon on the night of Halloween is taking place after 65 years. The last time the Moon reached its full phase on October 31 was back in 1955. The next time when a Full Moon will coincide with Halloween is in 2039!
Since this full Moon occurs near when the Moon is farthest from the Earth (apogee), this is a Micro Moon (the opposite of a “Supermoon”).
- October 2020 Science Highlights
- The great conjunction of Jupiter and Saturn
- Jaw-dropping images of Comet NEOWISE
As NASA notes, this will be the Hunter’s Moon, the full moon after the Harvest Moon. According to the Farmer’s Almanac, with the leaves falling and the deer fattened, this was the time to hunt. Since the harvesters had reaped the fields, hunters could easily see the animals that have come out to glean (and the foxes that have come out to prey on them). The earliest use of the term “Hunter’s Moon” cited in the Oxford English Dictionary is from 1710.
October 31: Three Planets
On October 31, Uranus, the Earth, and the Sun will lie in a straight line with the Earth in the middle – an opposition. This is the best time to watch a planet as it lies opposite the Sun. On this occasion, Uranus will be about 61 million km closet but at mag +5.8, it won’t be visible to the naked eye.
But three planets are well up in the sky: Jupiter, Saturn, and Mars. To spot Jupiter and Saturn, look in the south-west direction after sunset. They are getting closer and closer. On December 21, i.e. on the day of Great Conjunction, the gas giants will be less than a degree apart. This rare proximity of Jupiter and Saturn takes place after 19.6 years on average. You can read more about it in this article.
Mars made its closest approach to the Earth on October 6. Because of its highly eccentric orbit, it was at opposition about a week later, on October 14. Mars is well up in the sky after sunset and by midnight it reaches its highest point in the sky. It is brighter than any other star or planet except Venus. Look for its bright red hue!