Mars Conjunction with Regulus: Viewing Guide for June 2025

From June 11 to June 22, 2025, the planet Mars will pass north of the bright star Regulus in the constellation Leo, offering a remarkable celestial event for stargazers. This conjunction is set to occur during the darkening evening twilight, with optimal viewing times identified between June 15 and June 18, when both celestial bodies will be positioned approximately 15 degrees above the western horizon. Mars will shine at a magnitude of +1.4, compared to Regulus’s magnitude of +1.3, making the two objects nearly equal in brightness and visually striking in the night sky.

According to Pete Lawrence, a prominent astronomer and presenter on BBC's The Sky at Night, the best opportunities to observe the conjunction will be between 23:00 BST (22:00 UT) from June 15 to June 18. As the days progress, the separation between Mars and Regulus will decrease, reaching a minimum of 45 arcminutes on June 17, before widening again on June 18.

Regulus, often referred to as the 'heart of the lion', is the brightest star in the Leo constellation and is positioned close to the ecliptic—the apparent path of the Sun across the sky. This alignment is a product of perspective, as Mars orbits the Sun while Regulus is a distant star, located far beyond our Solar System. Astronomers have long observed conjunctions, which occur when celestial bodies appear close together from our vantage point on Earth.

The phenomenon of conjunctions is rooted in the formation of the Solar System, where all planets emerged from a common disc of dust surrounding the nascent Sun. This shared origin leads to a visible alignment along the ecliptic, allowing for conjunctions like that of Mars and Regulus.

The event is not only significant for amateur astronomers but also provides a captivating demonstration of celestial mechanics. Observers are encouraged to utilize binoculars for an enhanced viewing experience, ensuring that they wait until the Sun is fully set to avoid potential eye damage from direct observation of the solar glare. For those wishing to document this event, sharing photographs is encouraged, with submissions to be sent to the BBC Sky at Night Magazine.

As the month progresses, the waxing crescent Moon will also participate in this celestial display, moving between Mars and Regulus on June 29, adding further interest to the night sky.

In conclusion, the conjunction of Mars and Regulus from June 11 to June 22, 2025, presents a unique opportunity for observers to appreciate the beauty of our universe. With proper planning and observation techniques, stargazers can witness this remarkable alignment and engage with the wonders of astronomy.