Nighttime skywatchers from East Asia to North America might be treated to the rare spectacle of a “Beaver blood moon” on Tuesday, weather permitting, because the Earth, moon and sun align to provide a complete lunar eclipse for the last time until 2025.
Listed below are some key facts in regards to the upcoming celestial display, unfolding in an exceedingly unusual concurrence with Election Day in the US, and about lunar eclipses usually.
WHAT’S HAPPENING
A complete lunar eclipse occurs when the Earth casts its shadow completely over a full moon, blocking reflection of all direct sunlight from the lunar orb and dimming the colour of the moon to a reddish hue, hence the term “blood moon.”
This is just possible when the orbits of the Earth, moon and sun align in order that the moon is directly behind Earth relative to the sun. Otherwise, the moon passes above or below Earth’s shadow because its orbit around Earth is often tilted relative to Earth’s orbit in regards to the sun.
WHY RED
The reddish appearance of the lunar surface – the moon doesn’t entirely disappear from view – is brought on by rays of sunlight across the periphery of the eclipse shadow, or umbra, being filtered and refracted because it passes through Earth’s atmosphere, bathing the moon not directly in a dim copper glow.
The degree of redness is determined by atmospheric conditions that fluctuate with levels of air pollution, dust storms, wildfire smoke and even volcanic ash.
HOW RARE
Total lunar eclipses occur, on average, about once every 12 months and a half, in line with NASA. However the interval varies. Tuesday’s event will mark the second blood moon this 12 months, following one in mid-May. The subsequent one just isn’t expected until March 14, 2025.
WHERE IT’S VISIBLE
Tuesday’s eclipse might be visible across eastern Asia, Australia, the Pacific and North America. Skywatchers in Asia and Australia will see it with their evening moonrise, while the spectacle will play out for observers in North America within the early morning hours before the moon sets. It’s going to be visible to the naked eye wherever skies are clear in those regions.
HOW LONG IT LASTS
The complete eclipse will unfold over a period of nearly six hours because the moon step by step edges into the Earth’s paler, outer shadow, its “penumbra,” then enters the Earth’s darker, inner shadow, or “umbra,” before reaching totality and eventually emerging from the opposite side.
On the West Coast of the US, the entire display will run from 12:01 a.m. PST until just before 6 a.m., with the overall eclipse phase lasting about 90 minutes, peaking at 3 a.m.
WHY BEAVER MOON
Tuesday’s event will coincide with the “Beaver moon,” a moniker for November’s full moon adopted by the Old Farmer’s Almanac supposedly from Algonquian languages once spoken by Native Americans within the Latest England territory. When combined with the phenomena of a complete lunar eclipse, it’s widely known as a “Beaver blood moon” in the US.
Sources: NASA; Space.com; Sky & Telescope magazine; Griffith Observatory; Old Farmer’s Almanac