Fireball over Kitt Peak National Observatory in Arizona

Fireball over Kitt Peak National Observatory in Arizona

A fireball streaks across the morning sky above NSF Kitt Peak National Observatory (KPNO), a National Science Foundation-funded Program of  NOIRLab. The sky is filled with blue-green airglow while the Sun starts to brighten the night from the east. At the bottom center of this photo the constellation Orion rises above the KPNO 2.1-meter Telescope, one of the earliest telescopes on the KPNO site.

Fireballs are exceptionally bright meteors that, like all meteors, heat up when they enter Earth's atmosphere at high velocities and leave a trail of glowing material in the sky. Meteors are classified as fireballs when they shine brighter than the planets, which is an apparent magnitude of –4 or brighter. Located west of Tucson, Arizona in the Sonoran Desert, Kitt Peak benefits from exceptionally dark skies, allowing celestial phenomena like fireballs to stand out more vividly. Its high elevation minimizes atmospheric interference, while its remote distance from city lights ensures dark skies, making it a premier location for astronomical research.

Airglow occurs when atoms and molecules in the Earth's upper atmosphere, excited by sunlight, emit light to shed their excess energy. Or, it can happen when atoms and molecules that have been ionized by sunlight collide with and capture a free electron. In both cases, they eject a particle of light—called a photon—in order to relax again. The phenomenon is similar to auroras, but where auroras are driven by high-energy particles originating from the solar wind, airglow is energized by ordinary, day-to-day solar radiation. 

Unlike episodic and fleeting auroras, airglow shines constantly throughout Earth’s atmosphere, and the result is a tenuous bubble of light that closely encases our entire planet. (Auroras, on the other hand, are usually constrained to Earth’s poles.) Just a tenth as bright as all the stars in the night sky, airglow is far more subdued than auroras, too dim to observe easily except in orbit or on the ground with clear, dark skies and a sensitive camera.

Learn more about airglow: 
https://www.nasa.gov/solar-system/why-nasa-watches-airglow-the-colors-of-the-upper-atmospheric-wind/

Credit: KPNO/NOIRLab/NSF/AURA/J. Dai
Release Date: May 28, 2025

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