What's Up - July 2021

What's Up for July? The "Evening Star" beckons, and in search of the Milky Way...

Sunsets in July come with an added bonus: a brilliant gem low in the western sky, calling to us to come and explore its many mysteries. This is the planet Venus. It's our cosmic nextdoor neighbor – that is, the planet with the closest orbit to the orbit of Earth.

It's also often thought of as Earth's sister planet, given that it's also a rocky world of the same size, though Venus developed into a hellishly hot world, where Earth became the cool, blue planet we know and love.

Venus is sometimes referred to as "the Morning Star," or "the Evening Star," depending on whether it's visible around sunrise or sunset. This month, it's the latter, and you'll find Venus low in the west together with a faint planet Mars beginning about half an hour after sunset. In fact, you can watch each evening as Venus and Mars get closer, culminating with a close conjunction on July 12th, when they'll be only a finger's width apart. Look for them together with a slim, crescent Moon that's only 10% illuminated.

In June, NASA announced that two new space missions would be heading to Venus beginning later in the decade. VERITAS and DAVINCI+ will investigate the planet's surface and atmosphere, returning incredible images, maps, and other data, likely rewriting our understanding of how Earth's sister planet became so inhospitable, along with how it might still be active today. They'll be joined by the European spacecraft EnVision, for what's sure to be an exciting new chapter in solar system exploration.

July is one of the best times of year to enjoy the magical sight that is the Milky Way. This is our view of our spiral galaxy, seen edge on, from within. Now, some part of the Milky Way is visible in the night sky any time of year, but the galaxy's bright, complex core is only observable during certain months. Earlier in the season, you have to wait until the wee hours of the morning for the core to rise in the sky. But in June and July, the core has already risen by the time it's fully dark, and can be seen fairly well til around 2am when it starts to set.

Now, the Milky Way is faint, and to see it, you'll need to find your way out to fairly dark skies, but as long as you're below about 55 degrees north latitude, you should be able to observe the Milky Way core under dark skies. (Southern Hemisphere observers have it even better, as the core appears much higher overhead there.)

One super important tip is to avoid the full moon and the days close to it, since a bright Moon overwhelms the faint glow of the Milky Way. The three or four nights around the new moon are best, but the week before and after is also okay – you just have to note when the Moon will be rising or setting. There are a variety of great apps and websites to help you find dark skies and figure out when and where to look. So here's hoping you get out there and experience one of the most fantastic sights the sky has to offer.

Here are the phases of the Moon for July. You can catch up on all of NASA's missions to explore the solar system and beyond at nasa.gov. I'm Preston Dyches from NASA's Jet Propulsion Laboratory, and that's What's Up for this month.