Are you ready for November’s sky watching highlights? Cool autumn evenings are a great time to look for the Pleiades star cluster. You’ll also have a couple of great opportunities to observe the Moon with Jupiter and Saturn. Plus, check out the phenomenon known as Earthshine. Learn about all that and more from NASA’s Jet Propulsion Laboratory’s video below!
by Lauren Lambert
There’s an extra special treat coming Earth’s way – a Blue Moon on the night of Oct. 31 for Halloween.
What is a Blue Moon?
According to modern folklore, it is a phenomenon where a Full Moon appears twice in one calendar month. Typically, each month has only one, as Full Moons occur about 29 days apart.
Our first Full Moon of the month – known as a Harvest Moon – occurred on Oct. 1. This is a name given to the Full Moon happening closest to the autumnal equinox – the first day of fall. The Blue Moon coming up is respectively known as the Hunter’s Moon. Rising in the early evening, the Hunter’s Moon was given its name because it provided plenty of moonlight for hunters to gather meat for the long winter ahead.
While the informal phrase “once in a Blue Moon” refers to something that rarely happens, the same definition rings true for the skies this Halloween. These moons are of significance because they only come every two or three years. In fact, the last Blue Moon occurred on March 31, 2018.
Contrary to its name, a Blue Moon has nothing to do with the Moon having a blue hue. However, very rarely there are actual blue-tinted Moons due to particles thrown into the atmosphere by natural catastrophes. In 1883, an Indonesian volcano called Krakatoa had an eruption so large that it was compared by scientists to a 100-megaton nuclear bomb. Lots of ash from the Krakatoa explosion rose into the atmosphere. Many of these ash particles were about 1 micron in size, which could scatter red light and act as a blue filter. This resulted in the Moon appearing blue.
Blue-colored Moons appeared for years following the 1883 eruption. Many other volcanos and even wildfires throughout history have been known to affect the color of the moon. As a rule of thumb, in order to create a bluish Moon, dust or ash particles must be larger than ~0.6 microns, which is the wavelength of red light. Having said that, what we call a Blue Moon appears pale grey and white – just like the Moon on any other night. Having a second Full Moon in one given month does not change its color.
October’s Blue Moon, however, will be the first Blue Moon to appear on Halloween since 1944. This moon occurred one month following the introduction of the Aggregat 4, or the V-2 rocket. This rocket was the first vehicle capable of reaching the edge of space. In years following, the Apollo Saturn V became its direct descendant.
As we approach October 2020’s Blue Moon, the Artemis Generation prepares to explore the Moon’s surface from a lunar base. NASA’s Artemis program is named after the twin sister to Apollo, the Sun god in Greek mythology, and she is known as the goddess of the Moon. There hasn’t been this much momentum to return to the Moon’s surface since the Apollo missions.
The next Halloween Blue Moon will occur in 2039. By then, the Artemis Generation will hopefully look at Mars from that same lunar base – perhaps passing the torch to an Ares Generation bound for the Red Planet.
Happy equinox, Earthlings! Sept. 22 marks the fall equinox, when day and night are nearly equal.
“However, that day/night length depends on where you are on Earth,” said NASA solar scientist Mitzi Adams. “For example, at the North and South Poles, the length of the day and night is six months!”
At the North Pole, the Sun will sink below the horizon for a kind of twilight from now until sometime in October when it will be completely dark, explained Adams. Spring twilight begins a few weeks before the vernal, or spring, equinox in March, when the Sun rises above the horizon again.
This only happens twice in Earth’s year-long trip around the Sun. The rest of the year, the Sun shines unevenly over the Northern and Southern Hemispheres. That’s because Earth’s axis is tilted with respect to the Sun-Earth plane. But on these special days – the spring and fall equinox – the Sun shines equally on both north and south.
Here in the Northern Hemisphere, it’s the first day of astronomical fall. From now until the beginning of spring, nighttime hours will last longer than daylight as the Sun travels a shorter arc across the sky each day. The Sun has its shortest path of the year at the time of the winter solstice — the shortest day and longest night of the year — when sunrise and sunset are as far south as they can go (at any one location). It’s just the opposite in the Southern Hemisphere, where September 22 kicks off astronomical spring.
The equinox—meaning “equal night” in Latin—occurs at 8:31 a.m. CDT.
This month spot the Moon together with Mars and Venus, along with the flickering star Fomalhaut, which had itself a planet…until it didn’t! Check out the video below produced by NASA’s Jet Propulsion Laboratory to learn more.
The month of August brings a bunch of opportunities to see the Moon posing with the planets. Plus, here come the meteors! Learn more via the video below produced by NASA’s Jet Propulsion Laboratory.
For Comet Vocabulary, please read to the end of the post.
For most, early July is when most people living in the United States look to the skies to watch dazzling firework shows. However, this month there is a different kind of show happening in the sky.
Comet Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) was only discovered a few months ago on March 27 by NASA’s NEOWISE telescope and has quickly become a popular solar system visitor. Its popularity is warranted, however, as it is the brightest comet since Comet Hale-Bopp that passed by Earth 23 years ago in 1997.
Comet nuclei are cosmic snowballs of frozen gases, rock and dust that orbit the sun. They can range in size from a few miles to tens of miles wide, and the nucleus of NEOWISE measures about 3 miles across. When these comets approach the sun, their frozen bodies start to sublimate, and they spew dust and gasses in a tail that can span millions of miles.
Comet NEOWISE made its harrowing close approach to the sun, known as its perihelion, on July 3, and it is now zooming past the Earth on its way back out of the solar system. NEOWISE will make its closest approach (64 million miles) to Earth on July 22, but the best viewing window is happening right now until July 19.
NEOWISE can be seen with the naked eye, but for an even better viewing experience, binoculars or even a telescope is recommended. As for which to choose, binoculars are your current best option. “Definitely use binoculars for now – the tail of NEOWISE is at least 7 degrees long, which is much bigger than the field of view of most telescopes,” said Bill Cooke, lead of NASA’s Meteoroid Environment Office at Marshall Space Flight Center. “Binoculars will allow you to see the whole thing, whereas a telescope only shows a tiny part.”
To see NEOWISE, start looking in the northwestern sky about an hour after sunset. The comet will be below the stars that make up the bowl of the Big Dipper and shining nearly as brightly at a magnitude 3. If you are an early riser, you can still see NEOWISE about an hour before sunrise in the northeastern horizon until the end of the week.
You need a clear view of the horizon to see this comet. Beaches, fields, and areas with higher elevations are all great observation spots. In areas with more light pollution, binoculars may be necessary for viewing. This is definitely a once-in-a-lifetime event, as NEOWISE won’t be visiting again for 6,800 years!
Learn more about comets at NASA’s Solar System Exploration website.
For comet-related, kid-friendly activities, visit NASA Science Space Place.
Comet – Made up of ice, dust and gas which form a coma and sometimes a visible tail when it is orbiting close to the sun
Nucleus – The head of the comet, which is made up of ice and frozen gas that vaporizes to form the coma and the tail
Sublimate – The transition of a substance directly from the solid to the gas state, without passing through the liquid state
Perihelion – The point where an object orbiting the sun is closest to the sun
NASA’s Mars 2020 mission is planned to launch this summer, sending the Perseverance rover and the first-ever Mars helicopter to the Red Planet. So, if you’re a Mars exploration fan, this month is a great time to spot Mars yourself. Check out the video below produced by NASA Jet Propulsion Laboratory to learn more.
The sky will put on a show Nov. 11 when Mercury journeys across the Sun. The event, known as a transit, occurs when Mercury passes directly between Earth and the Sun. From our perspective on Earth, Mercury will look like a tiny black dot gliding across the Sun’s face. This only happens about 13 times a century, so it’s a rare event that skywatchers won’t want to miss! Mercury’s last transit was in 2016. The next won’t happen again until 2032!
“Viewing transits and eclipses provide opportunities to engage the public, to encourage one and all to experience the wonders of the universe and to appreciate how precisely science and mathematics can predict celestial events,” said Mitzi Adams, a solar scientist in the Heliophysics and Planetary Science Branch at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “Of course, safely viewing the Sun is one of my favorite things to do.”
This year’s transit will be widely visible from most of Earth, including the Americas, the Atlantic and Pacific Oceans, New Zealand, Europe, Africa, and western Asia. It starts at about 6:35 a.m. CST, but viewers in some areas, such as the West Coast, will have to wait until the Sun rises at their location to see the transit already in progress. Thankfully, this transit will last almost six hours, so there will be plenty of time to catch the show. At about 9:20 a.m. CST, Mercury’s center will be as close as it is going to get to the Sun’s.
Mercury’s tiny disk, jet black and perfectly round, covers a tiny fraction of the Sun’s blinding surface — only 1/283 of the Sun’s apparent diameter. So you’ll need the magnification of a telescope (minimum of 50x) with a solar filter to view the transit. Never look at the Sun directly or through a telescope without proper protection. It can lead to serious and permanent vision damage. Always use a safe Sun filter to protect your eyes!
Scientists have been using transits for hundreds of years to study the way planets and stars move in space. Edmund Halley used a transit of Venus in 1761 and 1769 to determine the absolute distance to the Sun. Another use of transits is the dimming of Sun or star light as a planet crosses in front of it. This technique is one way planets circling other stars can be found. Scientists can measure brightness dips from these other stars (or from the Sun) to calculate sizes of planets, how far away the planets are from their stars, and even get hints of what they’re made of.
The International Observe the Moon Night is happening Oct. 5!
In the wake of the beautiful Harvest Moon seen Sept. 14, Earth’s satellite now enters its waning phase, shrinking slice by slice into a visible semicircle as the rotating Earth spins around the Sun and its shadow is cast past us onto the Moon.
This period of waxing or waning is commonly known as a “gibbous” period, a term meaning “convex” or “rounded.” The term originated in the 15th century, though the Oxford English Dictionary suggests it was first applied to describe the Moon in 1690.
Gradually, over the coming month, the Moon will cycle toward its next full period – the Hunter’s Moon, also known as the Blood Moon or Sanguine Moon, due in mid-October. Various Native American tribes gave the Moon this name to reflect the falling leaves of autumn and the fattening of deer and other animals to prepare for the winter to come.
Speaking of coming events, the International Observe the Moon Night is happening Oct. 5! Learn more about NASA’s plans and how you can join in the fun here.
Take a moment this weekend to gaze at the beautiful Harvest Moon! The Moon will appear full Thursday night through Sunday morning. Early Saturday morning, Sept. 14, will mark the actual full Moon.
The Harvest Moon gets its name from agriculture. In the days before electric lights, farmers across the Northern Hemisphere depended on bright moonlight to extend the workday beyond sunset. It was the only way they could gather their ripening crops in time for market. The full Moon closest to the autumnal equinox became “the Harvest Moon,” and it was always a welcome sight.
The term became further entrenched in popular culture thanks to a 1903 pop tune called “Shine on Harvest Moon.”
A Harvest Moon inflated by the moon illusion — a common phenomenon with full moons seen close to the horizon, where familiar Earth objects such as trees or buildings lend the Moon a false sense of size — is simply beautiful to view, but even more so to the farmers gathering their crops in on those cool autumn evenings.