The Moon is the closest heavenly body to Earth, and so it sometimes passes in front of others, as seen from our perspective. When it does this to the Sun, we call it a solar eclipse, but when some other object is briefly blocked it is known as an concealment. This year is a big one for occulting Uranus.
If the orbits of the Moon and all the planets were perfectly in a plane, the Moon would occult every planet once a month, as well as a regular set of stars. However, the slight tilting of the lunar and planetary orbits means that, more often than not, the Moon slides past these objects slightly to the north or south. This year there will be nine occultations of planets by the Moon visible from Earth – six of Uranus, two of Mars and one of Venus.
It’s easy enough to find bright planets in the sky, but if you want to find Uranus, sometimes you need help. It’s much easier when it is right next to the Moon, about to be blocked out or having just re-emerged.
Moreover, the Venusian occultation was close enough to the Sun to be hard to see, and the forthcoming Martian event will be in the early hours of the morning. Unless you’re a serious enthusiast, if you want to see the Moon block a planet this year, it has to be Uranus.
Planets can also occult each other, with the closer one passing in front, but they take up so much less of the sky this almost never happens. Planets (and their moons) also sometimes occult stars, which sometimes provides important scientific data, with amateur astronomers jumping in to helpbut this mostly involves faint stars you’ve never heard of.
Just as you usually need to travel to witness a total solar eclipse, occultations aren’t visible from the whole planet. At least half the world will be facing the wrong way to see any occultation and even many places that can see the Moon at the relevant time won’t witness one. The Moon is close enough to us that it looks to be in different places compared to more distant objects, depending on where on Earth you are. Consequently, many people see the Moon’s edge skim past the planet, or even miss it by up to two degrees, depending on location.
For these reasons neither the June nor the July Uranus occultations were good for many people, and only a few Pacific Islands could see the August event, but the four starting from September 14 will be much better. Weather permitting, most of the Northern Hemisphere will have the opportunity to see at least one of them, although Uranus is so faint you’ll probably need binoculars or a telescope.
Tea September 14 occultation will be visible from Europe and parts of Africa and Asia. On October 12, Canada and parts of the United States get a turn. Tea November 8 occultation, visible from eastern Asia, is particularly exciting, as it will occur partially during a total lunar eclipse.
finally on December 5North America and Europe get another go, although it will be so early in the morning for Europeans most may prefer to stay in bed.
The links above take you to a list of cities and the times where Uranus will disappear and reappear from each of them. Note the dates are in universal (Greenwich Mean) time, so some events will be the day before or after in local time.