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.
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

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.
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

Earth Day: NASA Celebration, Lyrids to Peak

Earth Day – also known as the birth of the modern environmental movement – is Thursday, April 22, 2021. It began in 1970, giving a voice to an emerging public consciousness about the state of our planet. The celebration is widely recognized as the largest secular observance in the world, with more than a billion people participating annually in support of preserving the health and beauty of our planet.

In observance of Earth Day, NASA will host a virtual event April 21-24 to show how we are #ConnectedByEarth with a week of online events, stories, and resources. The event platform will feature live presentations by NASA scientists, as well as interactive chats with Earth science experts. Visitors can explore the connections between Earth’s atmosphere, water cycle, forests, fields, cities, ice caps, and climate through videos and interactive science content, a kid-friendly fun zone, a scavenger hunt, hundreds of downloadable resources, and more. Some content also will be available in Spanish.

Earth Day
This Earth Day, NASA highlights science and technology that is helping us all live more sustainably on our home planet and adapt to natural and human-caused changes. Credits: NASA

On Earth Day at 11 a.m. EDT, NASA will host a special live conversation with Grammy-nominated singer-songwriter Shawn Mendes and five people living and working in space: NASA astronauts Mike Hopkins, Victor Glover, Dr. Shannon Walker, and Mark Vande Hei; and Japan Aerospace Exploration Agency (JAXA) astronaut Soichi Noguchi. The event will air live on NASA Television, the NASA app, and the agency’s website. Learn more about NASA’s Earth Day plans and free online registration.

After several months of a meteor drought in 2021, we also have the annual Lyrid meteor shower coming up on Earth Day. The Lyrids will peak in the predawn hours of Earth Day (April 22). If you miss the peak, the wee hours of the following morning (April 23) offer another chance to see this shower, though the number of meteors will be down about 30% from the night of the 21st/22nd.

Lyrid and not-Lyrid meteors over New Mexico
Composite image of Lyrid and not-Lyrid meteors over New Mexico from April, 2012. Credits: NASA/ MSFC/ Danielle Moser

Observers in the Northern Hemisphere will see the most Lyrids, with the best time to watch between midnight and dawn. Although you’ll see a fairly bright Moon in the evening sky, it will set before the shower peaks near dawn. Peak rates for the Lyrids are around 10-20 meteors per hour. The meteors will appear to radiate from the constellation Lyra, but they can appear anywhere in the sky, which is why it is important to lie on your back and take in as much sky as possible.

The Lyrids is among the oldest of known meteor showers, with records going back for 2,700 years or more. It is produced by dust particles left behind by Comet C/1861 G1 Thatcher, which was discovered in 1861. The shower runs annually from April 16-25.

For more on meteor showers, visit the NASA Meteor Watch Facebook page.

Happy Earth Day and meteor watching!

by Lance D. Davis

Jupiter-Saturn Great Conjunction: Watch Best View Since Middle Ages!

by Lance D. Davis


Stargazers get ready for a nice treat as we are about to witness a super-rare planetary alignment not seen for almost 800 years!

Our solar system’s two biggest worlds – the mighty Jupiter followed by the glorious ringed Saturn – will appear in the sky next to each other at their closest since 1623 and closest visible from Earth since the Middle Ages in 1226. This will happen on Dec. 21, 2020, during an event called a “great conjunction.”

Astronomers use the word conjunction to describe close approaches of planets and other objects on our sky’s dome. They use great conjunction specifically for Jupiter and Saturn because of the planets’ top-ranking sizes.

view of the 2020 great conjunction through the naked eye just after sunset
A graphic made from a simulation program, showing a view of the 2020 great conjunction through the naked eye just after sunset at approximately 5:15 p.m. (EST) on Dec. 21.
Credit: NASA

Great conjunctions between Jupiter and Saturn happen every 20 years, making the planets appear to be close to one another. This closeness occurs because Jupiter orbits the Sun every 12 years, while Saturn’s orbit takes 30 years, causing Jupiter to catch up to Saturn every couple of decades as viewed from Earth.

The last conjuction between these planets took place on May 28, 2000. This year’s conjunction occurs on Dec. 21, which coincidentally is also the date of the winter solstice in the Northern Hemisphere. The 2020 conjunction is unique because of how close Jupiter and Saturn will appear. In most conjunctions, Jupiter and Saturn pass within a degree of each other. This year, they will pass 10 times closer to each other – the closest in nearly 400 years.

view of the 2020 great conjunction through a telescope
A graphic made from a simulation program, showing the view of the 2020 great conjunction
through a telescope at approximately 5:15 p.m. (EST) on Dec. 21. Credit: NASA

Currently, you can watch Jupiter and Saturn get closer in Earth’s sky each evening until their grand finale on Dec. 21. Just look for them shortly after sunset, shining brightly and low in the southwestern sky. Also, tune in to NASA Science Live or NASA Facebook on Dec. 17 at 3:00 p.m. EST (2:00 p.m. CST) and learn how to see Jupiter and Saturn’s great conjunction.

During the great conjunction, the giant planets will appear just a tenth of a degree apart – that’s about the thickness of a dime held at arm’s length! This means the two planets and their moons will be visible in the same field of view through a small telescope. Truly, this is a once-in-a-lifetime event!

Some astronomers suggest the pair will look like an elongated star and others say the two planets will form a double planet. To know for sure, we’ll just have to look and see. Either way, take advantage of this opportunity because Jupiter and Saturn won’t appear this close in the sky until 2080!

Additional Information & Resources:

Learn how to photograph the Jupiter-Saturn conjunction.
Read about mission visits to Jupiter and Saturn.
Find an astronomy club or event near you!

Total Solar Eclipse to Cast Shadow on South America

by Lauren Lambert

What is a Solar Eclipse?

A solar eclipse is a natural phenomenon that occurs when the Moon passes between the Sun and Earth. This event happens when the Moon completely blocks the Sun and the Moon’s shadow falls onto a portion of the Earth’s surface.

There are three types of solar eclipses: total, partial and annular. During a total solar eclipse, observers can witness daytime twilight because the disk of the Moon blocks 100% of the Sun. During a partial solar eclipse, the Moon is not entirely covering the Sun and you will likely not notice any difference in light intensity. You may only notice a subtle difference if the partial eclipse is close to total and you go outside at maximum eclipse.  Lastly, an annular eclipse can be observed when the Moon is at apogee, or the farthest from Earth within its elliptical orbit. This causes a ring of light, or annulus, to be visible around the Moon, which is sometimes referred to as the “ring of fire.”

total solar eclipse image
During the total solar eclipse, the Sun’s visible-light corona (meaning crown), only visible at maximum eclipse from within the path of totality, is seen here as a crown of white light extending from around the edge of the eclipsing Moon. The red loops of material also seen around the edge, are called prominences, in which magnetic fields enclose hot solar material. Credit: NASA/Armstrong’s Gulfstream III.

Total eclipses are of particular interest to solar scientists, because with the Moon blocking the bright light of the Sun, you can see the Sun’s atmosphere from the ground.  Solar scientists at Marshall Space Flight Center, and around NASA, make use of telescopes called coronagraphs that block the Sun so they can see the dim atmosphere, the corona, around it. But — given how perfectly the Moon lines up with the Sun — you can see the atmosphere closer to the surface of the Sun than we even can with our telescopes in space.

The shadow of the Moon on a planet during an eclipse can be described using three terms: umbra, antumbra and penumbra. The umbra is the shadow that is cast when the Moon completely covers the Sun and is where the path of totality falls. If the Moon is further away from the Earth, it is unable to block the Sun entirely. The Sun appears as a ring of light around the Moon. In this case, the shadow is known as the antumbra, or path of annularity, and occurs during an annular eclipse. Similarly, a partial solar eclipse can be observed when only a portion of the Moon blocks the Sun and creates a shadow referred to as the penumbra. The penumbra also occurs surrounding the umbra during a total eclipse, effectively covering those regions on the planet that only have a view of a partial eclipse.

Crescents of light from solar eclipse
Crescents of light are projected onto the ground during the partial phases of a solar eclipse due to light from the Sun passing through gaps between the leaves of trees, a pinhole effect. This is a safe and indirect way to view a solar eclipse. Credit: NASA/Johnson Space Center

Solar eclipses happen at least twice per calendar year, with total solar eclipses occurring about once every year and a half. But the possibility of seeing them is rare if you’re not in the right place at the right time. Additionally, since Earth is made up of mostly water, the path of totality, or the area receiving total blockage of the Sun, may not necessarily fall on land.

The year of 2020 sees two solar eclipses. The first occurred on June 21 and was an annular solar eclipse, visible from the continents of Africa and Asia. The second will be a total solar eclipse, occurring on Dec. 14, visible from South America. The path of totality crosses over Chile and Argentina, but some of their areas outside of the path of totality will experience a partial solar eclipse. The total eclipse will also be visible in Antarctica, South Africa, as well as the Pacific, Atlantic, and Indian Oceans. Observers will be able to witness the total solar eclipse for about 2 minutes.

If you are not within the path of totality, watching the total solar eclipse from a virtual location is an option as well. You can view it on NASA TV and the agency’s website, beginning at 10:30 a.m. EST on Dec. 14.  Be sure to check it out, as the next total solar eclipse won’t be happening until Dec. 4, 2021.

Top 5 Solar Eclipse Viewing Tips:

  1. Do not stare directly at the Sun. Wear safety approved, protective solar eclipse-viewing glasses to directly view the event or use some indirect means (see below). For more information here are some NASA Safety tips.
  2. To indirectly view the eclipse, create a pinhole camera or box projector. Learn how to build your own here.
  3. Stand under a tree and look at the ground. The trees act as pinhole projectors and will project hundreds of crescent shapes right at your feet.
  4. To capture an eclipse with binoculars, a telescope, or a camera, you must use a safety-approved, protective solar filter on your lens.
  5. Keeping with the theme of 2020 Observe the eclipse virtually! It will be streamed live here.

Sky Watching Highlights for December 2020

In the month of December, stargazers get ready for some excitement in the sky! Catch the year’s best meteor shower, the Geminids, in the middle of the month. Then, witness an extremely close pairing of Jupiter and Saturn that won’t be repeated for decades. And mark the shortest day of the year on the northern winter solstice. Check out the video below produced by NASA’s Jet Propulsion Laboratory to learn more!

‘Once in a Blue Moon’ Coming Soon

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.

One way to make a Blue Moon is by using a blue filter. That's what a photographer did back in 2004 when he photographed this Full Moon rising over Brighton, Massachusetts. Credit: Kostian Iftica
One way to make a Blue Moon is by using a blue filter. That’s what a photographer did back in 2004 when he photographed this Full Moon rising over Brighton, Massachusetts. Credit: Kostian Iftica

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.

It’s All About Mars in October

by Lance D. Davis

NASA is developing a path for an exciting journey to Mars – a rich destination for scientific discovery and human exploration as we expand our presence into the solar system. This month of October brings an amazing night-sky view of the Red Planet.

Mars is currently visible, reaching its highest point in the sky around midnight. Earth’s closest neighbor is also at its brightest and will remain that way well into November.

Two illustrations contrasting Mars’ position when it reaches opposition and conjunction. During opposition, like in October 2020, Earth passes near Mars – which is easily visible and bright. During conjunction, Mars and Earth are far from each other, so Mars appears small and faint.
Two illustrations contrasting Mars’ position when it reaches opposition and conjunction. During opposition, like in October 2020, Earth passes near Mars – which is easily visible and bright. During conjunction, Mars and Earth are far from each other, so Mars appears small and faint. Credit: NASA

Right now, Mars is the third brightest object in Earth’s night. The Moon and Venus are the two brightest objects, and usually Jupiter is third. But for this season, Mars is passing close enough to Earth to outshine Jupiter. This great visibility of Mars coincides with an event known as opposition, which happens every two years and two months.

Opposition occurs when the orbit of a planet, such as Mars, takes it near the Earth. Just like runners passing each other on a track, the faster, inner planets, such as Earth, can approach and overtake slower-moving outer planets like Mars. When the planets pass each other during this opposition, Mars’ proximity means it will appear larger and brighter in our sky. Because the Sun, Earth, and Mars are lined up during this passing, Mars will rise at sunset, having a high overhead at midnight. This is the closest the Red Planet will come to Earth for the next 15 years, or until September 2035.

At its furthest, Mars reaches about 250 million miles (400 million km) from Earth. During the October opposition, it will be as close as 40 million miles (60 million km) – nearly seven times closer. Although Mars will still look like a bright star to the unaided eye, it will grow dramatically in size when seen in a telescope. This year, Mars’ closest approach to Earth happens just a week before the opposition on Oct. 13, giving the Red Planet its biggest, apparent size of the 2020’s.

When it comes to observing Mars around opposition, telescopes will show more of the planet’s details, such as dark and light regions on Mars’ surface, and the prominent south polar ice cap, which will be tilted towards the Earth. Due to the turbulence of our atmosphere, these details can be hard to see, especially in smaller telescopes.

Many amateur astronomers use a color video camera attached to their telescope, running special software that selects the best frames to stack into a single image. This helps in negating the blurring caused by the air.

The most striking thing about Mars’ appearance – whether seen with the naked eye or through a telescope – is its red color. This color is caused by iron in the rocks on Mars’ surface – the same thing that causes the red color in sandstone formations in the southwestern US.

So, when you spot Mars, keep your eye on it and enjoy its fiery, red brightness!

 

Sky Watching Highlights for October 2020

There’s plenty to see in the sky for October! The Moon will be full not once, but twice this month. It’s also a great time for viewing Mars and trying to spot the galaxy of Andromeda. Learn more from the video below produced by NASA’s Jet Propulsion Laboratory.