The gegenschein rests on the tip of the dimmer pyramidal-shaped false zodiacal mild. Credit score: Stephen James O’Meara
In April 1961, Galaxy journal contained an article entitled “The Puzzle Known as Gegenschein,” by German-American science author Willy Ley. Referring to the thriller of who was the primary to establish the faint glow of the gegenschein, Ley wrote: “Historians of astronomy are in honest settlement that the primary discoverer of the Gegenschein was the Danish astronomer Theodor Brorsen [in 1854] … however Brorsen himself acknowledged that he was not the primary to see it.”
Brorsen credited French astronomer Esprit Pézenas as having seen it in 1730. However in 2021, Donald Olson, an astronomer at Texas State College, decided that what Pézenas took for the gegenschein (which he described as pink) was as a substitute a facet of an amazing auroral show that occurred Feb. 15, 1730.
Within the January 2024 subject of Journal of the British Astronomical Affiliation, Marinus A. van der Sluijs argues that U.S. Navy chaplain George Jones (1800–1870) seems to have noticed the gegenschein a few months previous to Brorsen. On the morning of Jan. 30, 1854, Jones noticed what he known as a diffuse “Zodiacal Gentle” barely east of Regulus (within the area of the antisolar level) at 2:00 a.m., which he adopted for one more three hours. About two weeks later, he mentioned it appeared like a “dim department of the Milky Way, that has strayed off from the final course.”
Sadly, in all this dialogue, the person who a long time earlier gave the gegenschein its title has been neglected, although I argue it is a mistake. I’ll clarify.
What’s the gegenschien?
Gegenschein is a German phrase that means “counterglow,” and refers to a faint oval glow. About 10° throughout at its largest, it might match comfortably contained in the bowl of the Huge Dipper. It seems at a place instantly reverse, or counter to, the Solar on the ecliptic — the pathway of the Solar, marked by the zodiacal constellations.
The gegenschein is part of the identical complicated of dimly shining options that features the zodiacal mild and the a lot fainter zodiacal band. The minuscule particles orbiting the Solar kind a dust disk on the ecliptic airplane, and light-weight reflecting off it creates all these phenomena. Whereas the dust cloud’s origin continues to be being debated, observations from NASA’s Juno spacecraft reveal that dust storms on Mars could be the supply of the dust disk, which lies between the orbits of Earth and Mars.
Of those phenomena, the zodiacal mild is probably the most intense. It’s a diffuse cone of sunshine (typically described as a pyramid) seen within the western sky within the night. It first seems across the finish of astronomical twilight and units about two hours later; the cone’s tip then reappears because it begins to rise about two hours earlier than dawn, and seems highest simply earlier than daybreak.
In his guide Cosmos (Vol. 1), German scientific explorer and naturalist Alexander von Humboldt recorded that on the evening of March 16, 1803, when the zodiacal mild was “most strongly luminous,” he noticed a pyramidal counterglow — gegenschein, in his native language — within the east. Though the title survived, students have typically discredited Humboldt’s observations, believing that what he described as an japanese zodiacal pyramid was really an atmospheric phenomenon known as the false zodiacal mild.
However would Humboldt actually have been fooled? The false zodiacal mild is visually a lot dimmer than the looks of the rising gegenschein. And, as E.R. Hope of Canada’s Defence Analysis Board defined within the Nov. 25, 1961, subject of Nature, the false zodiacal mild is an atmospheric impact that “opens out” from the gegenschein towards the horizon, creating this pyramid.
My observations of the false zodiacal mild made on Aug. 8, 2023, from the extraordinarily flat Makgadikgadi Pans in Botswana, confirmed these attributes. On that evening, I first noticed the gegenschein rising within the east on the finish of astronomical twilight. Solely after figuring out the placement of the gegenschein towards the celebrities did I discover the a lot dimmer skirt of the false zodiacal mild trailing down from the horizon. So sure, there was a pyramid of sunshine within the east — simply as Humboldt reported. The gegenschein shaped its tip and was additionally probably the most outstanding half. In different phrases, I’d not have observed the false pyramid had it not been for the presence of the gegenschein.
So, who found the gegenschein? I’ll exit on a limb and say that not solely did Alexander von Humboldt uncover and title the phenomenon in March 1803, however he was additionally the primary to find the false zodiacal mild as properly. And Brorsen was the primary to offer an in depth description. As all the time, ideas and observations are welcome at sjomeara31@gmail.com.
