June 30
The Falling Eagle
Sun Position
The Sun is in Cancer, declination near +23.0°. Northern days have been shortening for nine days now; the sky is entering its deep summer phase with Vega, Deneb, and Altair all well placed.
Sky Highlight
On June 30, 1908, the Tunguska event occurred over Siberia, the largest impact event in recorded history, when a small asteroid or comet fragment exploded in the atmosphere above the Podkamennaya Tunguska River. The explosion flattened forest across an area roughly the size of a major metropolitan region and is a reference point for planetary defense discussions today.
Deep Sky Object
M57 (Ring Nebula), a planetary nebula about 2,300 light-years away. M57 in Lyra is the textbook example of a planetary nebula (a glowing shell of gas expelled by a star that exhausted its hydrogen) and it sits conveniently close to Vega, making it easy to locate in the summer sky. Excellent from northern latitudes through the summer; visible from southern mid-latitudes, though lower in the sky.
Featured Star
Vega (α Lyr) is the brightest star in the Summer Triangle and one of the most studied stars in the sky, a main-sequence A-type star (A0Va) only 25 light-years away, used for over a century as the photometric zero-point for stellar magnitude scales. Its rapid rotation, about 236 km/s at the equator, flattens it into an oblate disk shape barely detectable in precision measurements.
Around This Date
- June 30, 1908The Tunguska event occurred over central Siberia, when a small extraterrestrial body exploded in the atmosphere and released energy equivalent to a large nuclear weapon, flattening roughly 2,000 square kilometers of Siberian forest.
- June 30, 1971The crew of Soyuz 11 (Georgi Dobrovolski, Vladislav Volkov, and Viktor Patsayev) died when their capsule depressurized during reentry after a 23-day mission aboard Salyut 1, the only fatalities to occur in space above the Kármán line.
June ends with Vega overhead and a Siberian forest still regrowing from 1908, the sky is not always remote.