Skywatch Line for Monday and Tuesday, June 29th and 30th, 2020

This is the Skywatch Line for Monday and Tuesday, June 29th and 30th, written by Joe Slomka.

The Sun sets at 8:37 PM; night falls at 10:53. Dawn begins at 3:05 AM and ends with the Sun rising at 5:21.

The Moon, past First Quarter in Virgo, rises Monday afternoon and sets at 2 AM, Tuesday. Tuesday finds he Moon, in Libra, also rising in the afternoon and at setting at 2:31 AM, Wednesday. Tuesday night finds the Moon about 2° from the star Alpha Librae (also known as Zubenelgenubi).

Jupiter is the first planet to rise, in Sagittarius, at 9:30 PM; it shines with brilliant 2nd magnitude and appears about 47 arc-seconds in size. Observers with binoculars or telescopes can witness the moon Europa begin to cross Jupiter’s face at 11:42 PM on Tuesday. Those with large telescopes and dark skies can see Pluto less than a degree from Jupiter, which sets after sunrise.

Saturn, in Capricornus, rises shortly after Jupiter, shining with zero magnitude and 18 arc-seconds. One hour before sunrise on Tuesday, Saturn and Jupiter lie about 6° from each other.

Neptune, in Aquarius, rises about Midnight, glowing with 8th magnitude and appearing a tiny 2 arc-seconds. Mars follows about a half-hour later, shining with minus zero magnitude and now 11 arc-seconds in size. Mars now appears about 84% lit and 33° high in the pre-sunrise sky. Mars and Neptune are about 10° apart.

Uranus rises next at 2 AM in Aries. The blue-green planet is about 6th magnitude and 3 arc-seconds. Venus, in nearby Taurus, rises last at 3:34 AM, blazing with minus 4th magnitude, 43 arc-seconds, 18% illuminated, but only 4° high.

About 7:15 AM, on June 30, 1908, a bright object roared out of the sky and exploded over a Siberian forest. The resulting blast knocked people off their feet 70 kilometers away. Night skies were so bright the one could read a newspaper at midnight. Barometers around the world monitored the blast wave. Tuesday is the 112th anniversary of the Tunguska Event.

The region, near the Tunguska River, was so remote that it took years for word to arrive at Moscow. Twenty years later, scientist Leonid Kulik led an expedition. He found the forest devastated for miles, with trees felled in a radial pattern from a central area. Suspecting a meteor, the expedition dredged the swamp to no avail.

Thanks to microscopic traces, we now know that the object was an asteroid that entered the Earth’s atmosphere. It exploded several miles above the surface with a force between three and five times the Hiroshima Atomic Bomb. Recent research also revealed that the object was smaller than first thought. In 1947, a large asteroid broke apart and impacted the Kamchatka Peninsula, also in Russia. Pictures exist showing Soviet trucks pulling thousand kilo meteorites from the ground. Today, meteor collectors buy pieces of the Sikote-Alin meteorite, as it is now called. A third similar event happened on February 13th 2016. A similar bright object dazzled citizens of the Russian city of Chelyabinsk and exploded, damaging property and injuring many people.

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