Jupiter closest to Earth this Friday night, January 9

If you’ve been mean­ing to look through a telescope, this week offers a great reason to do it. On January 9, Ju­piter reaches “perigee,” which is its closest point to Earth during this orbit. On January 10, Jupiter will be at “opposition,” which is when it sits directly opposite the Sun in our sky. Together, these events make Jupiter brighter, larger, and easier to observe than at almost any other time of the year.

Diagram of positions of Earth and Jupiter relative to the Sun. Credit: SVO.

When a planet is at opposition, it rises as the Sun sets and stays visible all night. This also places Earth di­rectly between the Sun and the planet, mini­mizing distance and maximizing bright­ness. Jupiter’s dis­tance from Earth can vary dramatically: at perigee, it can be about 390 million miles away, while at its farthest point, apogee, it can be roughly 580 million miles away. That’s a difference of nearly 200 million miles, which noticeably affects how large Jupiter appears through a telescope.

Earth also plays a role. In early January, our planet reaches “perihelion,” its clos­est point to the Sun, at about 91.4 million miles. Six months lat­er, at “aphelion,” Earth is about 94.5 million miles from the Sun, a change of roughly three percent. While this difference doesn’t affect our seasons, it does mean Earth is slightly closer to Ju­piter when opposition happens near perihe­lion The effect is sub­tle, but combined with Jupiter’s perigee, it gives observers a small boost in apparent size and brightness.

The result? A prime opportunity to see Jupiter’s cloud bands, its four largest moons, and possibly even the Great Red Spot.

Stellar Vista Ob­servatory (SVO) has two free public events coming up. First, a star party at Jackson Flat Reservoir at 7 p.m., on Friday, January 9. Telescopes will be pro­vided, and volunteers will help visitors ex­plore Jupiter, Saturn, the Orion Nebula and other winter night sky highlights. Dress warm and bring your curiosity; the solar system will be putting on a show!

SVO will also be at the Fredonia Library on Wednesday, Janu­ary 14, at 7 p.m., where we will be doing hands-on demonstrations with light and learning how to collect science data! We will also do some stargazing after­ward. Hope to see you there!