When a Star Explodes 

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A supernova is the cataclysmic explosion of a dying star, unleashing immense energy and ejecting matter into space. It marks the death of a massive star or the destruction of a white dwarf.

When a supernova explodes, it can suddenly shine millions of times brighter than usual. In some cases, they become briefly visible to the naked eye from Earth, at times rivaling the brightness of the most luminous stars in the night sky — and exceptionally, even visible in broad daylight.

A notable historical example is SN 1054, a supernova observed in daylight for several weeks beginning in July 1054, notably recorded by Chinese astronomers. Its remnant, the Crab Nebula, remains one of the most studied celestial objects today.

Since the famous SN 1054, many supernovae have been discovered — initially by attentive visual observers, and increasingly through automated systems. Today, robotic telescopes like those in the ATLAS network regularly detect new events. The amateur astronomy community, of which we are part, also plays an important role by monitoring these objects to estimate their brightness and enrich collaborative databases.

It was in this context that supernova SN2025mvn was discovered on June 3, 2025, by ATLAS. We were able to photograph and measure its brightness on June 17, 2025.

Realizing that SN2025mvn was within reach of our equipment, we took the opportunity to collect a series of images. These were then analyzed using the Tycho Tracker application to extract photometric measurements, which we shared with the scientific community.

As a picture is worth a thousand words, we include below an illustration of the supernova as it appeared during our observation. The V-band magnitude measured that evening was 15.3. As for its long-term brightness evolution, it will only become clear once sufficient data have been accumulated in the coming months… but that is another story.

Cette présentation se concentre sur une observation récente rendue possible grâce à notre nouveau télescope, illustrant notre volonté de poursuivre et d’enrichir un travail de contribution amorcé depuis plusieurs années. D’autres résultats publiés précédemment seront rappelés ultérieurement pour replacer cette observation dans un contexte plus large.