September Equinox Marks the Start of Fall 2022

Complemented by cooler temperatures and falling leaves, the September equinox marks the beginning of the fall season for the Northern Hemisphere. This year’s autumnal equinox (for the Northern Hemisphere) or spring equinox (for the Southern Hemisphere) occurs on Sept. 22 at 8:04 p.m. CDT.

An illustration of the March (spring) and September (fall or autumn) equinoxes.
An illustration of the March (spring) and September (fall or autumn) equinoxes. During the equinoxes, both hemispheres receive nearly equal amounts of daylight. (Image not to scale) Credits: NASA/GSFC/Genna Duberstein

During an equinox the Sun shines directly over the equator resulting in nearly equal amounts of day and night throughout the world – except for the North and South Pole where the Sun approximately straddles the horizon for the entire day, according to Alphonse Sterling, an astrophysicist at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Following the autumnal equinox, the Sun gradually continues to rise later and set earlier in the Northern Hemisphere – making the days shorter and the nightfall longer. The opposite is true in the Southern Hemisphere where the days begin to last longer.

Seasons are caused by Earth’s tilted axis which always points in the same direction. As Earth orbits around the Sun, the angle of sunlight that the Northern and Southern Hemispheres receive is different. “On the June solstice (summer) in the Northern Hemisphere, sunlight is more direct, so it warms the ground more efficiently,” said Mitzi Adams an Assistant Manager in the Heliophysics and Planetary Science Branch at Marshall. “In the Southern Hemisphere, sunlight is less direct (winter), which means that the ground is not heated as easily.”

A visual aid to better understand how the Earth's tilted axis causes the different seasons throughout the year in the Northern and Southern Hemispheres.
A visual aid to better understand how the Earth’s tilted axis causes the different seasons throughout the year in the Northern and Southern Hemispheres. Credit: NASA/Space Place

Astronomical seasons are defined by the Earth’s journey around the Sun, while meteorological seasons are guided by annual temperature cycles. Meteorologists group the seasons into time periods that line up with the weather and monthly calendar:  December through February is winter, March through May is spring, June through August is summer, and September through November is fall. Astronomical seasons are marked by the equinoxes and solstices that each happen twice a year. Solstices are when the Sun appears to reach the lowest or highest point in the sky all year; they mark the beginning of summer or winter. Solstices are commonly referred to as the longest (summer solstice) or shortest (winter solstice) day of the year.

The September equinox is a time that welcomes Earthlings to a new season. To those in the Northern Hemisphere, enjoy the beginning of milder weather and say hello to early sunsets and late sunrises.

by Lane Figueroa

Jupiter to Reach Opposition, Closest Approach to Earth in 59 Years!

Stargazers can expect excellent views of Jupiter the entire night of Monday, Sept. 26 when the giant planet reaches opposition. From the viewpoint of Earth’s surface, opposition happens when an astronomical object rises in the east as the Sun sets in the west, placing the object and the Sun on opposite sides of Earth.

Jupiter’s opposition occurs every 13 months, making the planet appear larger and brighter than any other time of the year. But that’s not all. Jupiter will also make its closest approach to Earth since 1963 – almost six decades ago! This happens because Earth and Jupiter do not orbit the Sun in perfect circles – meaning the planets will pass each other at different distances throughout the year. Jupiter’s closest approach to Earth rarely coincides with opposition, which means this year’s views will be extraordinary. At its closest approach, Jupiter will be approximately 367 million miles in distance from Earth, about the same distance it was in 1963. The massive planet is approximately 600 million miles away from Earth at its farthest point.

Photo of Jupiter with Red Spot
This photo of Jupiter, taken from the Hubble Space Telescope on June 27, 2019, features the Great Red Spot, a storm the size of Earth that has been raging for hundreds of years. Credits: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)

“With good binoculars, the banding (at least the central band) and three or four of the Galilean satellites (moons) should be visible,” said Adam Kobelski, a research astrophysicist at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “It’s important to remember that Galileo observed these moons with 17th century optics. One of the key needs will be a stable mount for whatever system you use.”

Kobelski recommends a larger telescope to see Jupiter’s Great Red Spot and bands in more detail; a 4 inch-or-larger telescope and some filters in the green to blue range would enhance the visibility of these features.

According to Kobelski, an ideal viewing location will be at a high elevation in a dark and dry area.

“The views should be great for a few days before and after Sept. 26,” Kobelski said. “So, take advantage of good weather on either side of this date to take in the sight. Outside of the Moon, it should be one of the (if not the) brightest objects in the night sky.”

As the Moon rose over the Wasatch Mountains near Salt Lake City on Feb. 27, 2019, the planet Jupiter could be seen, along with three of its largest moons.
As the Moon rose over the Wasatch Mountains near Salt Lake City on Feb. 27, 2019, the planet Jupiter could be seen, along with three of its largest moons. Stargazers should have a similar view during Jupiter in Opposition on Monday, Sept. 26. Credits: NASA/Bill Dunford

Jupiter has 53 named moons, but scientists believe that 79 moons have been detected in total. The four largest moons, Io, Europa, Ganymede, and Callisto, are called the Galilean satellites. They are named after the man who first observed them in 1610, Galileo Galilei. In binoculars or a telescope, the Galilean satellites should appear as bright dots on either side of Jupiter during opposition.

NASA’s Juno spacecraft, which has been orbiting Jupiter for six years, is dedicated to exploring the planet and its moons. Juno began its journey in 2011 and reached Jupiter five years later. Since 2016, the spacecraft has provided incredible images and data about Jupiter’s lively atmosphere, interior structures, internal magnetic field, and magnetosphere.

Scientists believe studying Jupiter can lead to breakthrough discoveries about the formation of the solar system. Juno’s mission was recently extended until 2025 or until the end of the spacecraft’s life. Learn more about Juno.

The next major project for Jupiter exploration is the Europa Clipper. This spacecraft will explore Jupiter’s iconic moon, Europa, which is known for its icy shell and vast ocean that lies beneath its surface. NASA scientists aim to find whether Europa has conditions able to sustain life.  Europa Clipper’s targeted launch is currently scheduled for no earlier than October 2024.

Learn more about the giant planet. And if you want to know what else is happening in the sky for September, check out  Jet Propulsion Laboratory’s latest “What’s Up” video:

by Lane Figueroa

Fireball lights up the sky over Salt Lake City

A bright meteor flew through the skies over northern Utah on Saturday morning, later raining down meteorites over the Great Salt Lake.

Residents of the Salt Lake City area were startled by loud booms at 8:30 a.m. MDT on Saturday, Aug. 13, 2022. Eyewitnesses saw a fireball in the sky, 16 times brighter than the full Moon.

GOES 17 Geostationary Lightning Mapper detection of the Aug. 13, 2022, fireball over northern Utah.
GOES 17 Geostationary Lightning Mapper detection of the Aug. 13, 2022, fireball over northern Utah. Credits: NOAA

Approximately 22,000 miles out in space, NOAA’s Geostationary Lightning Mappers (GLM) onboard the Geostationary Operational Environmental Satellites (GOES) 17 and 18 detected the meteor, which was first seen 50 miles over West Valley City. However, it is difficult to pinpoint its exact trajectory.

“Daytime fireballs are very tough to analyze,” said Bill Cooke, lead of NASA’s Meteoroid Environments Office at Marshall Space Flight Center in Huntsville, Alabama. “There are few eyewitness sightings of the fireball and videos posted on social media are difficult to calibrate without stars in the background.”

The meteor was first seen 50 miles over West Valley City, Utah, moving to the northwest at 39,000 miles per hour. The object broke apart above the eastern shore of the Great Salt Lake.
The meteor was first seen 50 miles over West Valley City, Utah, moving to the northwest at 39,000 miles per hour. The object broke apart above the eastern shore of the Great Salt Lake. Credits: NASA

After traveling northwest at 39,000 miles per hour, the object – a piece of an asteroid about 2 feet across – broke apart above the eastern shore of the lake. “One meteorite has been recovered from the lake shore,” said Cooke. “There are probably more, but I would expect the vast majority fell into the water.”

NASA studies meteoroid environments in space to protect astronauts and satellites in space. NASA’s Meteoroid Environment Office prepares meteoroid forecasts for missions like Artemis I, the first integrated test of NASA’s deep space exploration systems: the Orion spacecraft, Space Launch System rocket, and the ground systems at Kennedy Space Center in Cape Canaveral, Florida. The Artemis I launch is currently targeted for Aug. 29.

For more information on NASA’s All Sky Fireball Network, visit:

https://fireballs.ndc.nasa.gov 

To follow and share meteor updates, visit:

https://www.facebook.com/NasaMeteorWatch

By Hannah Maginot

Saturn to Reach Opposition Aug. 14

Saturn will have one of its best viewing opportunities of the year in the period surrounding Sunday, Aug. 14. Or it would, if the nearly Full Moon doesn’t spoil our fun.

On that date, Saturn will reach opposition – the point where it lies directly opposite the Sun in our night sky – around midnight local time for most stargazers, with the constellation Capricornus behind it.

Saturn will be visible for much of the night, rising above the southeastern horizon and lingering high in the southern sky. This will occur during Saturn’s perigee – its closest approach to Earth – making it even larger and brighter than usual.

An illustration of NASA's Cassini spacecraft in orbit around Saturn, where it documented the ringed planet in 2017.
An illustration of NASA’s Cassini spacecraft in orbit around Saturn, where it documented the ringed planet in 2017. (NASA/JPL-Caltech)

But as previously noted the last blog, the Moon will become full Aug. 11-12, and its bright wash of light will challenge spotters to clearly make out much around it in the night sky. Hopefully, Saturn’s position – west of the rising Moon – won’t cause it to be directly impacted.

The best thing about opposition this year is that Saturn will be visible all night long, said Caleb Fassett, a planetary scientist at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “That gives stargazers a good, long chance to find and observe it,” he said.

And despite the light-clutter from the Moon, all may not be lost. The rings of Saturn will face Earth at a 13-degree angle to our line of sight. And though Saturn is much farther from the Sun than our planet – an average 886 million miles out, compared to 94.4 million for Earth – a unique phenomenon may lend it even greater brightness during opposition.

The Seeliger effect, named for German astronomer Hugo von Seeliger, who died in 1924, identifies a dramatic brightening of a distant body or particle field when illuminated from directly behind the observer. With Earth passing between Saturn and the Sun, the sixth planet’s icy rings are likely to brighten perceptibly in the hours around opposition. 

Even so, it will still require a telescope to spot Saturn – which takes 29.4 Earth years to complete a single solar orbit – as anything more than a bright point of light.

Fassett recommends a 4-inch to 8-inch telescope to fully resolve the rings and provide a good look at the planet itself during opposition. With a decent telescope, it may even be possible to catch a glimpse of Titan and other Saturnian moons.

“It’s always pretty cool to see the distant planets, and Saturn is wild,” Fassett said. “Its rings and other unique characteristics make it a great subject of study for amateur astronomers and young space enthusiasts, and its moons are of great scientific interest.”

Among them is Titan, largest of Saturn’s moons, and the destination for NASA’s planned Dragonfly mission. Set to launch in 2027, Dragonfly will deliver an 8-bladed rotorcraft to the icy surface of Titan in the mid-2030s. There, it will examine the atmosphere and take samples of the surface, advancing our search for the building blocks of life and characterization of Titan’s habitability.

Learn more about Saturn here.

by Rick Smith

Perseids Meteor Shower on the Way

The Perseids are back! Well… sort of.

Usually bringing one of the most vivid annual meteor showers visible in Earth’s night sky, commonly delivering 50-100 “shooting stars” per hour at its height, the Perseids will peak Aug. 12 and 13. There’s just one problem: the full Moon.

A shower of Perseid meteors lights up the sky in 2009 in this NASA time-lapse image.
A shower of Perseid meteors lights up the sky in 2009 in this NASA time-lapse image. (NASA/JPL)

“Sadly, this year’s Perseids peak will see the worst possible circumstances for spotters,” said NASA astronomer Bill Cooke, who leads the Meteoroid Environment Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “Most of us in North America would normally see 50 or 60 meteors per hour,” he said, “but this year, during the normal peak, the full Moon will reduce that to 10-20 per hour at best.”

The Moon is so much brighter than anything else in the night sky, and it will wash out all, but the very brightest Perseids as they streak through our atmosphere and burn up far overhead.

As the full Moon subsides, the Perseids will begin to wane Aug. 21-22 and cease completely by Sept. 1. They’re the debris remnants of Comet Swift-Tuttle, a lumbering “snowball” composed of ice, rock, and dust, which orbits our Sun every 133 years. The comet itself was last visible to us in 1992 and won’t pass our way again until 2125.

How far back sightings of the Perseids actually go remains a matter of some contention, Cooke said. The comet itself wasn’t identified until 1862, but the meteor shower was seen over medieval Europe. The annual event came to be known as “the Tears of St. Lawrence,” named for the last of seven Roman church deacons martyred by the emperor Valerian in August of the year 258.

So, this is probably not the best year to make a special trip in order to see the Perseids, but, if you find yourself outside between midnight and dawn on Aug. 13, don’t forget to look up anyway.  Because you never know – you might just catch one of the bright Perseid meteors that defies the glare of the Moon. Also, the occasional early Perseid can streak across the sky as much as a week beforehand.

If you want to know what else is in the sky for August, check out the latest “What’s Up” video from Jet Propulsion Laboratory:

by Rick Smith