Easterly comet

April is the month when Comet C/2025 R3 PANSTARRS comes whiling down from the north and through the plane of Earth’s orbit, which is why we show this space view for it in the April pages of  Astronomical Calendar 2026.

This is a comet of the long-period type, dropping from the far outer solar system and likely to be “fresh,” not having lost the volatile materials that make comets conspicuous. The brightness of its central part should reach magnitude 8, the total magnitude could reach as bright as 4. It has to be remembered that, for comets, predictions about their magnitude and tail size are notoriously unreliable.

The general chart for comets on pages 128-129 shows C/2025 R3C/2025 R3 racing southeastward from Pisces to the feet of Orion.

Here are the main events in its passage through the inner solar system. “AU” means the astronomical unit, the Sun-Earth distance of  about 150 million kilometers or 93 million miles.

Mar 12     came within 1 AU of the Sun
Apr  8     comes within 1 AU of Earth
Apr 19     perihelion, 0.50 AU from the Sun
Apr 24     brightest (perhaps)
Apr 24     descending node through the ecliptic
Apr 26     nearest to Earth, 0.48 AU
May  1     crosses the celestial equator southward
May 16     back out past 1 AU from Earth
May 28     back out past 1 AU from the Sun

It aims to descend through the ecliptic plane ahead of us, which means it appears to the west of the Sun, that is, in the morning sky.

Here is the pre-dawn view over the eastern horizon on the day when the comet becomes within 1 AU of us, the same distance as the Sun (which is about twice as far below the horizon, in our picture, as the comet is above).

See the end note about enlarging illustrations. Arrows through the moving bodies show their movement (against the starry background) from 2 days earlier to 2 days later.

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