Tonight

Mercury and Regulus form a close pair on July 28

July 28 evening: Mercury and Regulus pair up

Shortly after sunset on July 28, 2023, Mercury and Regulus are very close – and very low – in the west. At their closest, they’ll only be 0.1 degrees apart; that’s 1/5 the diameter of a full moon. Wow! Once the sun slips over the horizon, the clock is ticking to find this duo before they set.

Mercury will be shining at 0 magnitude while Regulus will have a magnitude of +1.3. Depending on your eye sight and sky conditions, they may easily pop into view for you. Binoculars may help spot them in the bright evening twilight.

Additionally, on July 27, you can see Mercury approaching Regulus and then on July 29, you’ll notice Mercury has climbed past Leo’s brightest star.

Mercury and Regulus: Two charts showing Northern and Southern Hemisphere views of Venus, Regulus and Mercury.
On the evening of July 28, 2023, right after sunset, look for bright Mercury pairing up with Regulus in the evening twilight. The bright planet Venus is nearby and might help you find them. However, from the Northern Hemisphere, Venus will set about 30 minutes before Mercury and Regulus set. Mercury and Regulus will be easier to spot from the Southern Hemisphere due to their distance above the horizon. Chart via John Jardine Goss/ EarthSky.

To see a precise view from your location, try Stellarium Online.

The binocular view

Dark circle with 2 white dots for Regulus and Mercury.
Here’s a view of Mercury and Regulus in binoculars. Since they’ll be low on the horizon and in early evening twilight, you may need binoculars to find the close pair. Chart via John Jardine Goss/ EarthSky.

Mercury and Regulus

Mercury is one of the brightest planets. However, it can remain elusive since it’s never far from the sun and is often challenging to spot low on the horizon.

And Regulus is fainter, but still one of the brightest stars. It’s the brightest star in Leo the Lion.

Mercury is heading to greatest elongation

And then, for the next few weeks, keep an eye on the western sky after sunset, as Mercury will reach greatest elongation – or be farthest from the sun – on August 10, 2023. And then later in August, Mercury will be gone, too close to the sunset to see (really, passing between the sun and Earth). Mercury will emerge again in the morning sky around mid-September.

Meanwhile, Regulus – whose name means Little King – will be descending more each day in the western evening sky. Regulus and Leo will give way to a new batch of familiar seasonal constellations gracing the July and August evening skies.

Bottom line: Mercury and Regulus will be very close to each other on July 28. In fact, they’ll be 1/5 the diameter of the moon from each other. Wow! So don’t miss this lovely pair.

For more great observing events in the coming weeks, visit EarthSky’s night sky guide

For more videos of great night sky events, visit EarthSky’s YouTube page.

Posted 
July 28, 2023
 in 
Tonight

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