July 2020 is probably the best month for astronomy enthusiasts. It started with a penumbral lunar eclipse on July 5. Now there are three eye-catching celestial events ahead: the opposition of Jupiter, the opposition of Saturn, and a double meteor shower. Let’s talk about the opposition of Jupiter.
1. What Is An Opposition?
In celestial mechanics, a planetary opposition occurs when the Earth lies between the Sun and the planet with Earth being on the same side of the planet as shown below.
Thus on July 14, the Sun, the Earth, and Jupiter will lie along a straight line with Earth at the center. This optimal positioning occurs when Jupiter is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.
At around the same time that Jupiter passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest. However, Jupiter’s orbit lies far out in the solar system, at 5.2 AU from the Sun, and hence the angular size of Jupiter doesn’t vary over the course of conjunction and opposition.
2. How Close Will Be Jupiter?
At the opposition, Jupiter will be at a distance of about 619.34 million Km (4.14 AU) from the Earth. This is about 9 million Km closer than the average distance from Earth. Even at its closest approach to the Earth, however, it is not possible to distinguish it as more than a star-like point of light with the naked eye. A telescope can help you spot the four Galilean moons of Jupiter: Ganymede, Io, Europ, and Callisto.
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3. How To Watch Jupiter at Opposition?
Opposition marks the middle of the best time of year to see a planet. Since Jupiter will be opposite to the Sun, it will rise soon after sunset, reach its highest point in the sky around midnight, and will be out of sight at sunrise. The image below shows the position of Jupiter at 10:00 pm. Jupiter will shine bright at magnitude -2.75 and it will be the brightest object in the night sky after the Moon. The brighter Venus will rise a couple of hours before the Sun. Can you spot Saturn nearby? The ringed planet will make its closest approach a week later, on July 21.
In July, all the planets will be visible in the night sky. It’s a rare event, the planet parade. Read this article to learn how to spot the planets. Also, these space apps will help you locate the celestial objects quickly.