Watch the Skies

September Equinox 2021 is Coming!

In meteorology, the fall season begins on Sept. 1, however, the September (or fall) equinox gives us the green light to welcome the astronomical fall season in the Northern Hemisphere (and astronomical spring season in the Southern Hemisphere). This happens Sept. 22, 2021, at 19:21 UTC, which is 2:21 p.m. CDT for us in North America.

An illustration of the March (spring) and September (fall or autumn) equinoxes. During the equinoxes, both hemispheres receive equal amounts of daylight. Credit: NASA/JPL-Caltech

Along with marking the beginning of astronomical fall, the Sun will be exactly above Earth’s equator, moving from north to south, making day and night nearly equal in length – about 12 hours – throughout the world.

At the North Pole, over the upcoming days, the Sun will sink below the horizon for a kind of twilight from now until sometime in October when it will be completely dark, according to NASA solar scientist Mitzi Adams. Spring twilight at the North Pole 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 equinoxes – the Sun shines almost equally on the Northern and Southern hemispheres.

Equinox Solstice Info Graphic — Click to view larger. Credit: NASA/Space Place

In the Northern hemisphere, the September equinox marks the start of a period bringing us later sunrises and earlier sunsets. We will also feel cooler days with chillier winds, and dry, falling leaves.

The people of ancient cultures used the sky as a clock and calendar. They knew that the Sun’s path across the sky, length of daylight, and location of sunrise and sunset all shifted in a regular way throughout the year. Additionally, earlier civilizations built the first observatories, like Stonehenge in Wiltshire, England, and the Intihuatana stone in Machu Picchu, Peru, to follow the Sun’s annual progress.

Today, we celebrate the equinox as an astronomical event caused by Earth’s tilt on its axis and its motion in orbit around the Sun.

Enjoy the new season – whichever side of the globe you’re on!

by Lance D. Davis

August 2021 Brings Rare Seasonal ‘Blue Moon’

This month we’ll get to see a Full Moon on Aug. 22, 2021, known by some early Native American tribes of the northeastern United States, as the Sturgeon Moon. The name was given to the Moon because the large sturgeon fish of the Great Lakes, and other major lakes, were more easily caught at this time of year. But that’s not all! We also get to see a Blue Moon!

We’ve all heard the phrase “once in a Blue Moon,” which usually refers to something that rarely happens. Blue Moons do sometimes happen in Earth’s night sky, giving rise to this phrase. But what is a Blue Moon?

One way to make a Blue Moon is by using a blue filter. Credit: NASA

Well, we have two kinds of Blue Moons – monthly and seasonal.

A monthly Blue Moon is the second Full Moon in a calendar month with two Full Moons. Then, there’s a seasonal Blue Moon – the third Full Moon of an astronomical season that has four Full Moons.

In astronomy, a season is the period of time between a solstice and equinox, or vice versa. Each season – winter, spring, summer or fall – lasts three months and usually has three Full Moons, occurring about 30 days apart. Because June’s Full Moon came just a few days after the June (Summer) solstice, we will see four Full Moons in the current summer season, which ends at the September equinox on Sept. 22.

The third Full Moon – our seasonal Blue Moon – will happen on Aug. 22. All Full Moons are opposite the Sun, as viewed from Earth, rising fully illuminated at local time around sunset and setting around sunrise.

Perhaps you’re wondering if the Moon ever actually takes on a blue color. Well, Blue Moons that are blue in color are extremely rare and have nothing to do with the calendar or the Moon’s phases; they don’t have to be Full Moons either. When a blue-colored Moon happens, the blue color is the result of water droplets in the air, certain types of clouds, or particles thrown into the atmosphere by natural catastrophes, such as volcanic ash and smoke. Also, blue-colored Moons in photos are made using special blue filters for cameras or in post-processing software.

In 1883, an Indonesian volcano called Krakatoa produced an eruption so large that scientists compared it to a 100-megaton nuclear bomb. Ash from the Krakatoa explosion rose as high into the atmosphere as 80 kilometers (50 miles). Many of these ash particles can be about 1 micron in size, which could scatter red light and act as a blue filter, resulting in the Moon appearing blue.

Blue-colored Moons appeared for years following the 1883 eruption. Many other volcanoes throughout history, and even wildfires, have been known to affect the color of the Moon. As a rule of thumb, to create a bluish Moon, dust or ash particles must be larger than about 0.6 micron, which scatters the red light and allows the blue light to pass through freely. Having said all of that, what we call a Blue Moon typically appears pale grey, white or a yellowish color – just like the Moon on any other night.

Generally, Blue Moons occur every 2 to 3 years. Our last Blue Moon was on Oct. 31, 2020 – the night of Halloween. Mars was red and very large, since it was closer to Earth, and it was seen in the sky near the Blue Moon. Coincidently, this year’s Blue Moon will appear near planets again, but this time Jupiter and Saturn! We won’t see another Blue Moon until August 2023.

Learn more about Earth’s Moon here.

by Lance D. Davis

How many Perseids will I see in 2021?

By Bill Cooke, NASA Meteoroid Environments Office

Many Perseid-related news stories and social media posts state that the maximum rate is about 100 meteors per hour, which is a lot. So, folks get excited and go out on the peak night, braving mosquitos and other nightly hazards. But they are often disappointed; we routinely hear, “I went out and only saw a few meteors. Not even 20, much less 100!” And they would be right. The problem is that the 100 per hour is a theoretical number used by meteor scientists and does not convey what people are actually going to see.

In the 1980’s, meteor researchers were searching for a way to compare the meteor shower rates observed by various individuals and groups across the globe. People were reporting the rates, but the differences in sky conditions, radiant altitude and observer eyesight made getting a comprehensive view of shower activity difficult.

So, the meteor researchers put their heads together and came up with the concept of a ZHR, or Zenithal Hourly Rate. The ZHR is what you get after you correct the observed rates for the sky conditions, the altitude of the radiant above the horizon and observer biases. In other words, it is basically what a perfect observer would see under perfect skies with the meteor shower radiant straight overhead – which never happens!

The often-quoted ZHRs overestimate the meteor rates people actually see – sometimes by a lot. Fortunately, we can take the ZHR and invert things to get the hourly rates for certain locations and circumstances – it’s only math, after all. We have done this for select locations in the United States, producing the following maps.

These maps show the hourly rates that can be expected on the night of the Perseid shower’s peak, provided there are no clouds in the sky. (It’s hard to account for partial cloud cover.)

These rates assume you are out in the country, where lots of stars and the Milky Way are visible and no clouds, of course:

So, instead of 100 Perseids per hour, people in the U.S. can reasonably expect to see around 40-ish Perseids in the hour just before dawn on the peak nights. That’s about one every couple of minutes – not bad. However, we are assuming you are out in the country, well away from cities and suburbs.

What rates can you expect if you want to do your Perseid watching from the neighborhood? We also computed that:

The brighter skies of the suburbs greatly cut down the rates. We have gone from a Perseid every couple of minutes to one every 6-7 minutes – a factor of three reduction. This explains the great disappointment expressed by many casual Perseid watchers; they go outside, expecting to see at least a meteor a minute and end up with 10 or less in an hour. The brightness of your sky is everything in meteor observing – you have to get away from the lights!

But what about those in cities? The rates are close to zero:

Ugh! City dwellers might see a Perseid or two in an hour. Not very inspiring. Perhaps the only good news is that, if someone in a city sees a Perseid, it has to be really, really bright and spectacular.

Want to see Perseids? Then head out into the dark – it’s worth it!

Check out our previous blog post, The Perseids are on the Rise, for more information on the Perseids and tips on how to observe them.

The Perseids are on the Rise!

It’s time again for one of the biggest meteor showers of the year! The Perseids are already showing up in our night skies—and when they peak in mid-August, it’s likely to be one of our most impressive skywatching opportunities for a while.

Perseid Meteor image — In this 30 second exposure taken with a circular fish-eye lens, a meteor streaks across the sky during the annual Perseid meteor shower on Friday, Aug. 12, 2016 in Spruce Knob, West Virginia. Photo Credit: (NASA/Bill Ingalls)

Our meteor-tracking cameras spotted their first Perseid on July 26, but your best chance to see them will start the night of Aug. 11. With the crescent moon setting early, the skies will be dark for the peak viewing hours of midnight (local time) to dawn on Aug. 12.

This chart shows expected levels of Perseid activity for July and August 2021, relative to the peak on Aug. 11-13, ignoring the effects of the Sun, Moon, and clouds. All times are in UTC. Credits: (NASA/MEO/Bill Cooke)

If you’re in the Northern Hemisphere, and far away from light pollution, you might spot more than 40 Perseids an hour! (If you’re in a city, you may only see a few every hour; skywatchers in the Southern Hemisphere will also see fewer Perseids, with none visible below about 30 degrees south latitude.) The night of Aug. 12-13 will be another great opportunity to see the Perseids: with a full Moon (and lower meteor activity) during the Perseids’ peak in 2022 and a waning crescent high in the sky for 2023, this might be your best chance to do some summer skywatching for a few years.

Find somewhere comfortable, avoiding bright lights as much as possible (yes, including your phone), and give your eyes some time to adjust to the dark—up to half an hour if you can. The Perseids will appear as quick, small streaks of light: they get their name because they look like they’re coming from the direction of the constellation Perseus (near Aries and Taurus in the night sky), but Perseids in that area can be hard to spot from the perspective of Earth. So just look up and enjoy the show!

If you can’t see the Perseids where you live, join NASA to watch them on social media! Tune in overnight Aug. 11-12 (10 PM–5 AM CDT; 3–10 AM UTC) on Facebook, Twitter and YouTube to look for meteors with space fans from around the world. If skies are cloudy the night of Aug. 11, we’ll try again the same time on Aug. 12-13. Our livestream is hosted by the Meteoroid Environment Office at NASA’s Marshall Space Flight Center, which tracks meteors, fireballs, and other uncommon sights in the night sky to inform the public and help keep our astronauts and spacecraft safe.

Where do the Perseids *actually* come from?

The Perseids are fragments of the comet Swift-Tuttle, which orbits between the Sun and beyond the orbit of Pluto once every 133 years. Every year, the Earth passes near the path of the comet, and the debris left behind by Swift-Tuttle shows up as meteors in our sky. (Don’t worry, there’s no chance that we’ll run into the actual comet anytime soon.)

Where can I go to learn more?

We’ve got some great space-rock lessons for students, starting with the biggest question: what’s the difference between an asteroid and a meteor? Our NASA Space Place site also has a kid-friendly introduction to meteor showers in general. If you’re looking for something a little more hands-on, try this asteroid-building classroom activity—or, for an older audience, learn how to describe rocks like a NASA scientist.

And, if you want to know what else is in the night sky this month, check out the video below from Jet Propulsion Laboratory’s monthly “What’s Up” video series:

Happy skywatching!

by Brice Russ

See the Strawberry Moon – 2021’s Last Supermoon!

Our planet’s natural satellite – better known as the Moon – will appear opposite the Sun and fully illuminated on June 24, 2021, at 18:40 UTC, which is 1:40 p.m. CDT (UTC-5). This full Moon is quite special for two reasons: it’s a Strawberry Moon and the last supermoon of the year!

The Strawberry Moon marks the last full Moon of spring or the first full Moon of summer. Towards the end of June, the Moon usually sits in a lower position in the sky and shines through more of our atmosphere. Because of this, our Moon can sometimes give off a pinkish hue.

Surprisingly, the name likely has more to do with the time of the year it occurs than its unusual pink shade. Some Native American tribes referred to this full moon as the Strawberry Moon because it signaled a time for gathering ripening strawberries and other fruits.

A supermoon occurs when a full Moon coincides with the Moon’s closet approach to Earth in its elliptical orbit, a point known as perigee. During every 27-day orbit around Earth, the Moon reaches both its perigee, about 226,000 miles from Earth, and its farthest point, or apogee, about 251,000 miles from Earth.

Although supermoon is not an official astronomical term, it’s typically used to describe a full Moon that comes within at least 90% of perigee. In this phase, the Moon appears larger and brighter than usual. A new Moon can also be a supermoon. However, we typically do not see a new Moon since it is between Earth and the Sun, and therefore not illuminated.

If you’re in the daylight at the time of the Super Strawberry Moon, look for a better view during its moonrise, which is about 20 minutes after sunset, local time.

The Super Strawberry Moon will be the last of four supermoons for 2021. Supermoons only happen three to four times a year, and always appear consecutively. The last three supermoons occurred on May 26, April 27, and March 28.

Skywatchers, please enjoy the sunset in the west, and if you look toward the east, you may notice the subtle pink hue of our Super Strawberry Moon!

by Lance D. Davis

June Solstice Brings Summer, Winter Seasons

The June solstice gives us the green light to welcome the summer season in the Northern Hemisphere and winter season in the Southern Hemisphere. This happens June 21, 2021, at 03:32 UTC, but for us in North America, that’s June 20 at 10:32 p.m. CDT (UTC-5).

In meteorology, summer begins on June 1. Yet, June 21 is perhaps the most widely recognized day when summer starts in the northern half of our planet and winter starts in the southern half. This astronomical beginning of the summer season and long-held, universal tradition of celebrating the solstice have allowed us to treasure this time of warmth and light.

Summer solstice explanation — During the solstices, Earth reaches a point where its tilt is at the greatest angle to the plane of its orbit, causing one hemisphere to receive more daylight than the other. Credits: NASA/Genna Duberstein

Along with marking the beginning of summer, this will also be the longest day of the year in the Northern Hemisphere. We will begin to see early dawns, long days, late sunsets, and short nights. On the solstice, our Sun will reach its highest point as it crosses the sky. Meanwhile, south of the equator, winter will begin!

The ancient cultures knew that the Sun’s path across the sky, length of daylight, and location of the sunrise and sunset all shifted in a regular way throughout the year. Additionally, people built monuments, like Stonehenge, to follow the Sun’s annual progress, to worship the Sun, and to predict its movements.

Earth's seasons — Click to view larger. Credit: NASA/Space Place

Today, we celebrate the solstice as an astronomical event caused by Earth’s tilt on its axis and its motion in orbit around the Sun.

Earth’s axis may be imagined as an imaginary pole going right through the center of our planet from “top” to “bottom.” Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth’s surface gets some of each.

Earth doesn’t orbit upright; its axis is always tilted 23.5˚ with respect to the Sun-Earth line, which is why we have seasons. During the June solstice compared to any other time of the year, the north pole is tipped more directly toward the Sun, and the south pole is tipped more directly away from the Sun. As a result, all locations north of the equator see days longer than 12 hours and all locations south see days shorter than 12 hours.

Enjoy the new season – whichever half of the globe you’re in!

by Lance D. Davis

May’s Full Moon Comes with Supermoon Eclipse

As we approach month’s end, there is not one, not two, but three celestial events happening with our Moon!

The Moon will be located on Earth’s opposite side from the Sun and fully illuminated May 26, 2021, at 6:13 a.m. CDT. This Full Moon was known by early Native American tribes as the Flower Moon because this was the time of year when spring flowers appeared in abundance.

Compared to other Full Moons in 2021, the Flower Moon will have the nearest approach to Earth, making it appear as the closet and largest Full Moon of the year. This is what is commonly referred to as a “supermoon”. Yet, it’s not just bringing brightness and size. May’s supermoon is also bringing a “super power” to change its color, and the color is red!

A telescopic visualization of the 2021 total lunar eclipse.
Credits: NASA’s Scientifc Visualization Studio

Mars is most commonly known as the Red Planet. But have you ever witnessed our own planet’s Moon turn red? If you haven’t, you’ll get your chance with this year’s only total lunar eclipse also happening May 26! It’s been nearly two and a half years since the last one.

A total lunar eclipse occurs when the Moon passes completely through the Earth’s dark shadow, or umbra. During this type of eclipse, the Moon will gradually get darker, taking on a rusty or blood-red color. The color is so striking that lunar eclipses are sometimes called Blood Moons.

The total eclipse phase will be visible near moonset in the western United States and Canada, all of Mexico, most of Central America and Ecuador, western Peru, and southern Chile and Argentina. The eclipse can be seen in its entirety in eastern Australia, New Zealand, and the Pacific Islands, including Hawaii. Unlike a solar eclipse, you won’t need special glasses to view this lunar eclipse, just go outside and keep your head to the sky!

“Folks in Hawaii and the Aleutian Islands will get to see the entirety of this eclipse – it will be quite a show for them,” said Bill Cooke, Lead, NASA Meteoroid Environments Office.

The eclipse is set to begin May 26 at 1:46 a.m. PDT, with the Moon entering the darkest part of the Earth’s shadow at 2:45 a.m. Part of it will remain in the umbra until 5:53 a.m. To catch totality – the period when all of the Moon’s surface is blanketed by the Earth’s dark shadow – look up between 4:11 and 4:26 a.m.

We haven’t had a total lunar eclipse occur with a supermoon in almost six years, and the next total lunar eclipse won’t happen over North America until May 2022.

Enjoy this spectacle of the sky!

by Lance D. Davis

Flights are Complete! Mission Success!

After two days of experimenting in weightlessness, a team of researchers from NASA’s Marshall Space Flight Center have their feet firmly planted on the ground.

The team spent April 28 and 29 on parabolic flights with ZERO-G in Fort Lauderdale, Florida. The flight — which achieves various levels of microgravity by performing maneuvers known as parabolas — provided the team with an opportunity to study the formation of potentially destructive amyloid fibrils, or protein clusters, like those found in the brain tissue of patients battling neurodegenerative diseases. The experiment, called the ring-sheared drop, was developed by Marshall and Rensselaer Polytechnic Institute of Troy, New York.

Marshall materials science engineer, Ellen Rabenberg, has supported the project for nearly five years. After two flights on ZERO-G’s modified Boeing 727 — G Force One — in 2016 and 2020, she supported the payload from the ground this year. As ground support, she was responsible for preparing and installing the equipment for flight.

parabolic flight on Flight Aware's live map — Marshall’s ground support team tracked the parabolic flight on Flight Aware’s live map while G Force One performed 30 parabolas. (Flight Aware)

To track the flight in real time, Rabenberg followed the live updates on Flight Aware. Over the course of approximately two hours each day, she monitored the map as G Force One completed 30 parabolas.

Now, Rabenberg and her colleagues will analyze the data gathered in flight and determine next steps for their payload.

Parabolic Pre-flight Checklist

How do you prepare for weightlessness? A team of researchers at NASA’s Marshall Space Flight Center has been doing so in preparation of their April 28 and 29 parabolic flights with ZERO-G in Fort Lauderdale, Florida.

Marshall's parabolic flight crew — The Marshall team exits the G Force One after the first day of parabolic flights. (NASA)

So what is on their parabolic pre-flight checklist?

An easily digestible breakfast
The flight team is served a doctor-recommended breakfast of bagels, fruit, and juice — all of which digest quickly and easily to provide fuel for their bodies as they experience periods of variable gravity.

Proper attire
Fort Lauderdale is a subtropical climate with warm and humid conditions in the spring. Participants wear light, comfortable clothing and closed toed shoes for movement in the hangar, on the ramp, and on the aircraft. Each flyer wears a ZERO-G flight suit, which enables ease of movement in air.

A COVID-19 test
All non-vaccinated participants are tested for COVID-19 daily to ensure safety of all parties.

Identification
Just like a typical commercial flight, each individual must complete a TSA check before boarding the aircraft. They must present a valid driver’s license, passport, or other TSA-approved identification.

Once all the pre-flight boxes are checked, the team will board a modified Boeing 727 — named G Force One — to execute their experiment in a weightless environment.

Marshall's flight team completes a TSA check before boarding G Force One. — Marshall’s flight team completes a TSA check before boarding G Force One. (NASA)

While in the air, the team will test an experiment known as the Ring-Sheared Drop. Developed by Marshall and Rensselaer Polytechnic Institute of Troy, New York, the experiment will study the formation of potentially destructive amyloid fibrils, or protein clusters, like those found in the brain tissue of patients battling neurodegenerative diseases — such as Alzheimer’s and Parkinson’s.

To track the flight path as it performs parabolas, check out Flight Aware.

For more updates on the flight, the team, and the experiment, continue to follow Watch the Skies blog in the coming week.

Ring-Sheared Drop Team Prepares for Zero-G Flight

A team of researchers from NASA’s Marshall Space Flight Center is preparing to take flight and evade gravity in pursuit of science.

Team members are traveling to Fort Lauderdale, Florida, to test an experiment known as the Ring-Sheared Drop. Developed by Marshall and Rensselaer Polytechnic Institute of Troy, New York, the experiment will study the formation of potentially destructive amyloid fibrils, or protein clusters, like those found in the brain tissue of patients battling neurodegenerative diseases — such as Alzheimer’s and Parkinson’s.

The Ring-Sheared Drop team boards G Force One in Fort Lauderdale, Florida with their equipment. (NASA)

In Earth-based experiments, researchers determined that amyloid fibrils may be created by shear flow, or the difference in flow velocity between adjacent layers of a liquid. In the case of ground experiments, that formation is affected by the presence of container walls and by convection, or the circular motion that occurs when warmer liquid rises while cooler liquid descends.

The goal now is to conduct experiments in microgravity — in a containerless reactor — where the liquid specimens form spherical drops, containing themselves via surface tension. Researchers will “pin” a droplet of liquid between two rings and cultivate amyloid fibrils for study.

The experiment was initially launched to the International Space Station in 2019. However, when the experiment failed, efforts began on Earth to improve the testing apparatus for future testing. Now, before the equipment is ready for another trip to the space station, the team will “practice” pinning liquid drops on a parabolic flight.

The research team installs their experimental hardware on G Force One in preparation for April 28, 29 parabolic flights. (NASA)

How exactly is weightlessness reached? A modified Boeing 727 — named G-Force One — achieves periods of variable gravity through a series of maneuvers called parabolas. The team will be able to interact with their hardware in zero gravity for 22 seconds at a time.

NASA’s Flight Opportunities program, within the Space Technology Mission Directorate, makes these experiment flights possible by facilitating rapid demonstration of promising technologies for space exploration, discovery, and results benefit life on Earth.

The program matures capabilities needed for NASA missions and commercial applications while strategically investing in the growth of the U.S. commercial spaceflight industry.

The Ring-Sheared Drop team is scheduled to fly with their hardware April 28 and 29 on a parabolic flight managed by Zero G of Fort Lauderdale, Florida.

Continue to follow NASA’s Watch the Skies blog in the coming weeks for the latest updates on the team, the parabolic flight, and the results of the Ring-Sheared Drop experiment.