On July 25, an extraordinary celestial occurrence took place as an Earth-orbiting spacecraft witnessed both a lunar transit and an Earth eclipse on the same day. This remarkable phenomenon unfolded at different times, with both the moon and Earth passing between NASA's Solar Dynamics Observatory (SDO) and the sun.
The Solar Dynamics Observatory, launched in February 2010, is dedicated to studying the sun's activity. It meticulously monitors essential solar phenomena such as the solar wind—a stream of charged particles emanating from the sun—solar flares, and fluctuations in the sun's magnetic field. The data collected by SDO plays a crucial role in helping scientists forecast solar activity that can significantly impact Earth.
To maintain a constant watch over the sun, SDO operates in a geosynchronous orbit around Earth, completing one orbit every day. This unique orbital plane is angled relative to Earth's rotational axis, ensuring that Earth itself does not obstruct SDO's observations. However, there are moments when the moon obstructs SDO's view of the sun, leading to several partial eclipses each year.
The lunar transit on July 25 began around 2:45 UTC and marked SDO's fourth partial eclipse since April, as noted on SDO's blog. This particular transit was significant, being the deepest observed, as it covered up to 62% of the sun's disk and lasted approximately 50 minutes. Such events are critical for understanding the dynamics of solar observations and the interactions between celestial bodies.
Following the lunar transit, Earth also blocked SDO's view of the sun. Although SDO's orbit is specifically designed to minimize these interruptions, Earth occasionally passes between the spacecraft and the sun, resulting in brief eclipses. These events occur roughly twice a year and are part of what NASA refers to as eclipse seasons, which last about three weeks. Currently, SDO is experiencing its 31st eclipse season, which commenced on July 10 and will continue until August 7.
On July 25, around 6:30 UTC, approximately three hours after the moon's transit concluded, Earth completely obscured SDO's view of the sun. This total eclipse concluded shortly before 8:00 UTC, as documented on the Solar Dynamics Observatory blog. Notably, the images captured by SDO reveal distinct characteristics of each event; Earth's shadow presents a fuzzy edge due to atmospheric absorption of sunlight, while the moon, lacking an atmosphere, creates a sharp, defined circle on the sun's disk.
This is not the first instance where both Earth and the moon have eclipsed the sun from SDO's perspective on the same day. Similar events occurred in 2015 and 2016, resulting in a double eclipse phenomenon. Such occurrences are rare and highlight the unique positioning of celestial bodies.
For those on Earth wishing to experience solar eclipses, there are exciting events on the horizon. A partial solar eclipse will be visible from New Zealand and parts of Australia on September 21, while the next total solar eclipse is set to occur on August 12, 2026, with visibility in regions such as Greenland, Iceland, Russia, Spain, and Portugal. Mark your calendars for these astronomical events!
