This month is full of encounters between astronomical objects. Last week we had the Moon and Spica in Virgo in the evening, and Mars and Messier 35 in Gemini in the morning, and this week we have Venus and Regulus in Leo in the evening, and Mars and Jupiter in Gemini in the morning.
On the night of Sunday July 21, the planet Venus passes just north of the bright star Regulus in Leo in the western sky just after sunset. Credit: Starry Night software
Although Regulus is one of the brightest stars in the sky, Venus is far brighter, and will be by far the easier to see. Once you spot Venus, look below and to its left to spot Regulus. If you’re south of the equator, Regulus will be above and to the left of Venus.
Later that night, an hour before dawn, look in the northeastern sky to see Jupiter and Mars rise together. Jupiter will be the brighter of the two, with reddish Mars above and to its left. If you’re in the southern hemisphere, Mars will be below and to the left of Jupiter.
Later that night, an hour before sunrise, the planet Mars passes Jupiter. Credit: Starry Night software
If you have access to a telescope, these twin planets will make an interesting sight. Jupiter will be accompanied by its four bright moons, Io, Europa, Ganymede, and Callisto. What will be most noticeable is the tremendous difference in size between the two planets. Both are on the far side of the Sun, but still Mars is much closer than Jupiter. Even so, Jupiter will appear more than eight times larger in diameter than Mars.
The planets move relatively slowly as compared to the moon, so that, if you miss these events on Sunday night and Monday morning, try again the following night and morning, and these encounters will still be close enough to be fascinating.