Get Ready Stargazers: The Geminids Are Coming!

The second week of December heralds the beginning of the strongest meteor shower of the year – the Geminids. It’s a good time to bundle up, go outside and watch one of Mother Nature’s best sky shows!

The Geminids are active every December, when Earth passes through a massive trail of dusty debris shed by a weird, rocky object named 3200 Phaethon. The dust and grit burn up when they run into Earth’s atmosphere in a flurry of “shooting stars.”

Phaethon’s nature is debated. It’s either a near-Earth asteroid or an extinct comet, sometimes called a rock comet. There is another object – an Apollo asteroid named 2005 UD – that is in a dynamically similar orbit to Phaethon, prompting speculation that the two were once part of a larger body that split apart or collided with another asteroid.

Most shower meteors are shed by comets when their orbits take them into the inner Solar System, but the Geminids may be the debris from this long-ago breakup or collision event. When you consider that the Geminid meteor stream has more mass than any other meteor shower, including the Perseids, whatever happened back then must have been pretty spectacular.

So what do potential Geminid watchers need to do this year?

It’s pretty simple, actually. The nearly First Quarter Moon sets around 10:30 p.m. local time, so wait until then to go out – the light from the Moon washes out the fainter meteors, which are more numerous. Find the darkest place you can, and give your eyes about 30 minutes to adapt to the dark. Avoid looking at your cell phone, as it will mess up your night vision. Lie flat on your back and look straight up, taking in as much sky as possible. You will soon start to see Geminid meteors. As the night progresses, the Geminid rate will increase, hitting a theoretical maximum of about 100 per hour around 2 a.m.

Bear in mind, this rate is for a perfect observer under perfect skies with Gemini straight overhead. The actual number for folks out in the dark countryside will be slightly more than 1 per minute. Folks in suburbs will see fewer, 30 to 40 per hour depending on the lighting conditions. And those downtown in major cities will see practically nothing – even though the Geminids are rich in beautiful green fireballs, the lights of New York, San Francisco, or Atlanta will blot even them out. Dark clear skies are the most important ingredient in observing meteor showers.

Comet Wirtanen has a light blue hue in this image taken by NASA astronomer Bill Cooke using an iTelescope widefield 90 mm refractor and color CCD camera Nov. 29 at Siding Spring Observatory in Australia.

And while you’re scanning the sky for Geminids, you might notice a small, faint “ghostly” green patch in the constellation of Taurus – that’s Comet 46P/Wirtanen, which will be making its closest approach to Earth (7 million miles) for the next 20 years. We are actually going to have a comet visible to the unaided eye this holiday season!

Graphic showing the locations of the Geminid radiant and Comet 46P/Wirtanen for 35 degrees north latitude at 10:30 p.m. on the night of the Geminid peak (December 13).

Comets are notoriously unpredictable beasts, but if Wirtanen continues to follow its current brightening trend, it may reach a peak magnitude of around +3 (about as bright as a star in the handle of the Little Dipper) a couple of days past the Geminid peak, on December 16. Binoculars or a small telescope are good for taking a peak at Wirtanen, so bring them along for your night of Geminid watching. A green comet to complement the green fireballs!

International Observe the Moon Night

Did you know there is a night set aside each year to observe Earth’s closest celestial neighbor, the Moon? International Observe the Moon Night has been held annually since 2010 and is a worldwide celebration of the Moon and lunar science. Each year, the celebration is held in September or October when the Moon is in the first quarter because it is visible in the afternoon and early evening hours when most events are held.International Observe the Moon Night 2018 graphic

If you live in or near Huntsville, Alabama, you can join our local celebration Saturday, Oct. 20, from 5:30-8:30 p.m. CDT at the U.S. Space & Rocket Center’s Davidson Center. The event is hosted by NASA’s Marshall Space Flight Center’s Planetary Missions Program. Members of the public are encouraged to attend and it is free. The event will include lunar and solar system exploration exhibits and a variety of hands-on activities for children and adults. Don’t live in Huntsville? No worries! There are events held worldwide and you can find a list of them here.

Full moon.As you are gearing up for your own International Observe the Moon Night celebration, check out these fun facts about the Moon.

  • The Moon is Earth’s satellite and orbits the Earth at a distance of about 384,000 km or 239,000 miles.
  • The Moon makes a complete orbit around the Earth in 27 Earth days. The Moon keeps the same side or face, towards the Earth during its orbit.
  • More than 100 spacecraft have been launched to explore the Moon. It is the only celestial body beyond Earth visited by human beings.
  • Astronauts brought back a total of 842 pounds of lunar rocks and soil to Earth.
  • The 50th anniversary of the Apollo 11 landing on the Moon will be next summer on July 20, 1969. Neil Armstrong was the first human to set foot on the Moon, followed by Buzz Aldrin.

Astronaut Edwin E. Aldrin Jr., lunar module pilot of the first lunar landing mission, poses for a photograph beside the deployed United States flag during an Apollo 11 extravehicular activity (EVA) on the lunar surface. Can’t get to an event this weekend? You can still go outside no matter where you live and look at our incredible neighbor. For a list of Moon phases and other cool Moon facts, check out the NASA Science Earth’s Moon page.

Perseids Meteor Shower Peaks This Weekend

A live broadcast of the meteor shower from a camera in Huntsville, AL (if our weather cooperates!) will be available on NASA TV and the NASA Meteor Watch Facebook starting around 9 p.m. Eastern time (8 p.m. CT) and continuing until the early hours of August 13.

The Perseid meteor shower is here! Perseid meteors, caused by debris left behind by the Comet Swift-Tuttle, began streaking across the skies in late July and will peak on August 12.

The Perseid meteor shower is often considered to be one of the best meteor showers of the year due to its high rates and pleasant late-summer temperatures. This year’s shower peak, however, has the added bonus of dark skies courtesy of an early-setting crescent Moon. Combine these ideal observing conditions and high rates (an average of 60 meteors per hour at the peak) with the fact that the best nights for viewing – August 11 to 12 and August 12 to 13 – occur on a weekend and you have a recipe for successfully viewing some celestial fireworks!

A Perseid meteor over Daytona Beach, FL.
A Perseid meteor over Daytona Beach, FL. Perseids are known for being bright and fast, traveling 132,000 mph. Image Credit: NASA/MEO.

When Should I Look?

Make plans to stay up late or wake up early the nights of August 11 to 12 and August 12 to 13. The Perseids are best seen between about 2 a.m. your local time and dawn.

If those hours seem daunting, not to worry! You can go out after dark, around 9 p.m. local time, and see Perseids. Just know that you won’t see nearly as many as you would had you gone out during the early morning hours.

How can you see the Perseids if the weather doesn’t cooperate where you are? A live broadcast of the meteor shower from a camera in Huntsville, AL (if our weather cooperates!) will be available on the NASA Meteor Watch Facebook starting around 8 p.m. CT and continuing until the early hours of August 13. Meteor videos recorded by the NASA All Sky Fireball Network are also available each morning; to identify Perseids in these videos, look for events labeled “PER.”

Why Are They Called Perseids?

All meteors associated with one particular shower have similar orbits, and they all appear to come from the same place in the sky, called the radiant. Meteor showers take their name from the location of the radiant. The Perseid radiant is in the constellation Perseus. Similarly, the Geminid meteor shower, observed each December, is named for a radiant in the constellation Gemini.

Most of the meteors seen in this composite are Perseids.
Most of the meteors seen in this composite are Perseids. Notice how they all appear to be streaking from the same direction? The Perseids appear to radiate from a point in the constellation Perseus. Image Credit: NASA/MEO.

How to Observe Perseids

If it’s not cloudy, pick an observing spot away from bright lights, lay on your back, and look up! You don’t need any special equipment to view the Perseids – just your eyes.  (Note that telescopes or binoculars are not recommended.) Meteors can generally be seen all over the sky so don’t worry about looking in any particular direction.

While observing this month, not all of the meteors you’ll see belong to the Perseid meteor shower. Some are sporadic background meteors. And some are from other weaker showers also active right now, including the Alpha Capricornids, the Southern Delta Aquariids, and the Kappa Cygnids. How can you tell if you’ve seen a Perseid? If you see a meteor try to trace it backwards. If you end up in the constellation Perseus, there’s a good chance you’ve seen a Perseid. If finding constellations isn’t your forte, then note that Perseids are some of the fastest meteors you’ll see!

Pro tip: Remember to let your eyes become adjusted to the dark (it takes about 30 minutes) – you’ll see more meteors that way. Try to stay off of your phone too, as looking at devices with bright screens will negatively affect your night vision and hence reduce the number of meteors you see!

Happy viewing!

Go Outside and See Mars!

35.8 million miles is definitely not what most of us would consider “close.” But in planetary terms, close is definitely relative! On July 31, Mars will be 35.8 million miles from Earth, which is the closest it has been to Earth in 15 years. What does this mean for sky watchers? It means the Red Planet will appear super bright, and with its orange-red color, will be hard to miss in the nighttime sky. From July 27-30, the point in Mars’ orbit will come closest to Earth, and will be closest to Earth before sunrise Eastern Time on July 31.

What defines a “close approach?” The minimum distance from the Earth to Mars is about 33.9 million miles and does not happen very often. Because Earth and Mars have elliptical orbits and are slightly tilted to each other, all close approaches are not equal. When Mars slowly approaches what astronomers call opposition, it and the Sun are on opposite sides of the Earth. Earth and Mars align in opposition about every two years (fun fact: this is why most NASA missions to the Red Planet are at least two years apart – to take advantage of the closer distance). Opposition to Mars is at its closest to the Sun every 15 to 17 years, when excellent views of the Red Planet from Earth can occur. This is what is happening on the early morning hours of July 31.

Mars is the fourth planet from the sun.
Mars is the fourth planet from the sun.
Image credit: NASA

Is 35.8 million miles the closest Mars has ever been to Earth? Nope. In 2003, Mars was 34.6 million miles from Earth and the closest it had been in nearly 60,000 years. This type of proximity won’t occur again until 2287. But, there will be another close approach in October 2020 when the distance between the Red Planet and Earth will be 38.6 million miles.

Now that we’ve gotten all of that out of the way, what does this mean for you, the novice astronomer or general sky-watcher? It means that if you have clear skies where you live, go outside on the overnight hours of July 30 or early morning hours of July 31 and look up. The planet will be brighter than usual and will have an orange or red haze. You can also look through a telescope. If weather is bad where you are, NASA will be streaming live from the Griffith Observatory.

Good luck and happy viewing!

Total Lunar Eclipse

By Mitzi Adams, NASA Marshall solar scientist

Last August, citizens and visitors to the United States of America had a rare opportunity to see a total solar eclipse, because the path of totality ranged from Oregon to South Carolina, essentially bisecting the country. But alas, the total lunar eclipse happening on Friday, July 27, will totally miss the United States. Being able to observe the Moon totally immersed in Earth’s shadow depends mostly on whether it is dark at the time the eclipse happens, so about half the Earth would be in the right place to see the eclipse, weather permitting of course. This time, residents of Europe, Africa, Asia, Australia, and parts of South America will be so lucky. In contrast, totality for a solar eclipse is very narrow and only a very small portion of Earth is in the shadow of the Moon. For the August 2017 eclipse, only those within an approximately 100 km (63 miles) wide path saw the Sun totally eclipsed.

So what happens when there is a lunar eclipse? Unlike the solar variety, Earth blocks the Sun for a lunar eclipse. For the lunar eclipse to happen, the Moon’s phase must be “full”, which means that the orbiting Moon is opposite the Sun, with Earth in between. When the Sun sets in the west, the Moon rises in the east — and this event happens once a “moonth” (or month). But a lunar eclipse does not happen every month. Why is that?

The Moon is seen here during the January 2018 lunar eclipse, setting in the western horizon, not yet in totality.
The Moon is seen here during the January 2018 lunar eclipse, setting in the western horizon, not yet in totality.
Image credit: NASA/Alphonse Sterling

Well, now we get into more tricky territory. Let’s try a thought experiment. Draw a line between the centers of the Sun, Earth, and Moon. This line is part of a plane that describes how Earth orbits the Sun, called the plane of the ecliptic. The Moon orbits Earth, only its orbit is tilted with respect to the plane of the ecliptic, sometimes the Moon is above the plane, sometimes it is below the plane. Only when the Moon’s orbit lines up with the ecliptic plane do we have a chance for an eclipse. If the phase of the Moon is “full” when this happens, we have a lunar eclipse. If the phase of the Moon is “new,” we have a solar eclipse. Sometimes the orbital planes do not line up exactly, in those cases, we would have partial eclipses.

Fred Espenak, click here for more info on Lunar Eclipse Geometry.

The July 27 eclipse is somewhat special because the length of totality will be the longest of this century at one hour, 43 minutes. Why? Several reasons. The Moon will be at apogee, or at the farthest distance from Earth (406,000 km or 252,000 mi) possible for our Moon. Objects in orbit around Earth move slower the farther away they are, which means it will take longer for the Moon to traverse the width of Earth’s shadow. In addition, the Moon will be almost exactly on that line that connects Sun, Earth, Moon, also increasing the length of time the Moon will spend in the umbral (darkest) part of Earth’s shadow. Finally, Earth reached its greatest distance from the Sun (aphelion) quite recently (July 6), meaning that Earth’s shadow on July 27 will be close to the largest it can be, adding even more distance (and time) to the Moon’s shadowy traverse.

This image is of the full Moon before the January 2018 lunar eclipse.
This image is of the full Moon before the January 2018 lunar eclipse.
Image credit: NASA Marshall/Alphonse Sterling

The partial phase of the eclipse will begin at 18:24 UT, with totality beginning at 19:30 UT (see the NASA time zone page for help with conversion to your local time and official U.S. time). Totality will be over at 21:13 UT and the partial phase ends at 22:19 UT. Viewing a lunar eclipse does not require a telescope or even special glasses; however, while waiting for totality to begin, which is marked by a reddish-brown color to the Moon, a telescope could be used to view two planets that are in the evening sky. Mars will be visible, and should be pretty bright since there is currently a dust storm covering the entire planet. So the telescope will not see any surface detail here, but the redness of the planet will contrast well with the reddish hue of a totally eclipsed Moon. Saturn will be visible to the west of Mars — and even binoculars will resolve the rings, but a telescope could provide more detail. For all observers, find the full Moon in the night sky, Mars will be close to and below (south of) the Moon, a bright reddish “star-like” object. For detailed information about this eclipse, click here.

Bright Fireball Spotted Over Michigan

A bright fireball lit up skies over Michigan at 8:08 p.m. EST on Jan. 16, an event that was witnessed and reported by hundreds of observers, many who captured video of the bright flash.

Based on the latest data, the extremely bright streak of light in the sky was caused by a six-foot-wide space rock — a small asteroid. It entered Earth’s atmosphere somewhere over southeast Michigan at an estimated 36,000 mph and exploded in the sky with the force of about 10 tons of TNT. The blast wave felt at ground level was equivalent to a 2.0 magnitude earthquake.

The fireball was so bright that it was seen through clouds by our meteor camera located at Oberlin college in Ohio, about 120 miles away.

Events this size aren’t much of a concern. For comparison, the blast caused by an asteroid estimated to be around 65 feet across entering over Chelyabinsk, Russia, was equivalent to an explosion of about 500,000 tons of TNT and shattered windows in six towns and cities in 2013. Meteorites produced by fireballs like this have been known to damage house roofs and cars, but there has never been an instance of someone being killed by a falling meteorite in recorded history.

The Earth intercepts around 100 tons of meteoritic material each day, the vast majority are tiny particles a millimeter in diameter or smaller. These particles produce meteors are that are too faint to be seen in the daylight and often go unnoticed at night. Events like the one over Michigan are caused by a much rarer, meter-sized object. About 10 of these are seen over North America per year, and they often produce meteorites.

There are more than 400 eyewitness reports of the Jan. 16 meteor, primarily coming from Michigan. Reports also came from people in nearby states and Ontario, Canada, according to the American Meteor Society. Based on these accounts, we know that the fireball started about 60 miles above Highway 23 north of Brighton and travelled a little north of west towards Howell, breaking apart at an altitude of 15 miles. Doppler weather radar picked up the fragments as they fell through the lower parts of the atmosphere, landing in the fields between the township of Hamburg and Lakeland. One of the unusual things about this meteor is that it followed a nearly straight-down trajectory, with the entry angle being just 21 degrees off vertical. Normally, meteors follow a much more shallow trajectory and have a longer ground track as a result.

Shows the trajectory of the meteor.
This image shows the trajectory of the meteor as determined by the eyewitness accounts posted on the American Meteor Society Website. It is likely that there are meteorites on the ground near this region. (American Meteor Society)

NASA’s Short-term Prediction Research and Transition Center reported that a space-based lightning detector called the Geostationary Lightning Mapper — “GLM” for short — observed the bright meteor from its location approximately 22,300 miles above Earth. The SPoRT team helps organizations like the National Weather Service use unique Earth observations to improve short-term forecasts.

GLM is an instrument on NOAA’s GOES-16 spacecraft, one of the nation’s most advanced geostationary weather satellites. Geostationary satellites circle Earth at the same speed our planet is turning, which lets them stay in a fixed position in the sky. In fact, GOES is short for Geostationary Operational Environmental Satellite. GLM detected the bright light from the fireball and located its exact position within minutes. The timely data quickly backed-up eyewitness reports, seismic data, Doppler radar, and infrasound detections of this event.

Data from NOAA's GOES-16 space-based weather satellite
Data from NOAA’s GOES-16 space-based weather satellite detected a bright flash of light over southeast Michigan around the time a meteor entered Earth’s atmosphere. (NASA/SPoRT)

Much like the nation’s weather satellites help us make decisions that protect people and property on Earth, NASA’s Meteoroid Environment Office watches the skies to understand the meteoroid environment and the risks it poses to astronauts and spacecraft, which do not have the protection of Earth’s atmosphere. We also keep an eye out for bright meteors, so that we can help people understand that “bright light in the night sky.”

NASA Marshall Experts to Share Total Solar Eclipse In-person, on TV

On Monday, Aug. 21, for the first time in almost 100 years, all of North America will be treated to an eclipse of the sun. Those in the path of totality, running from Oregon to South Carolina, will experience one of nature’s most awe-inspiring events — a total solar eclipse.

Scientists, researchers and experts from NASA’s Marshall Space Flight Center in Huntsville, Alabama, will mobilize to experience the eclipse and share it with others. They will join participants from across the agency for a multi-hour broadcast, titled Eclipse Across America: Through the Eyes of NASA, to offer unprecedented live video of the celestial event, along with coverage of activities in parks, libraries, stadiums, festivals and museums across the nation, and on social media.

“It’s going to be a spectacular event,” said Marshall Chief Scientist James Spann. “We’ll be sharing our research and work with people and letting them know how to safely view the eclipse, not only at the events in the path of totality, but also worldwide online and on NASA Television. Excited doesn’t begin to describe how our team feels right now. It truly will be breath-taking, and we can’t wait.”

Marshall experts will be located at two of the broadcast’s 15 locations — Hopkinsville, Kentucky, and Austin Peay State University in Clarksville, Tennessee.

Read more here..

What Does a 97% Eclipse Mean Anyway?

Marshall’s Meteoroid Environment Office’s very own Dr. Bill Cooke, created this graphic showing the idealized view through a telescope with an H-alhpa filter at maximum eclipse for 4 locations: Birmingham, which will experience a 93% eclipse, Atlanta, which will have 97% of the Sun covered, the 97% eclipse in Huntsville, and the 99.6% eclipse in Chattanooga, which shows only the tiniest sliver of Sun down on the bottom.

The Greatest Meteor Show of All Time

By Bill Cooke

At NASA, we get very excited about many astronomical events — to name just a few, the return of Halley’s Comet back in 1985/86; the impact of the fragments of Comet Shoemaker-Levy 9 with Jupiter in 1992; the Leonid meteor storms of 1998, 1999, 2001 and 2002; and, of course, the upcoming total solar eclipse on Aug. 21 of this year.

Some of these events get blown a bit out of proportion. A classic example is that every time Mars comes to opposition (closest approach to Earth), the internet reverberates with the very false statement that Mars will appear as large as the Moon at that time. Nothing could be farther from the truth, as Mars, at its very closest to Earth, appears only 1/70th the apparent diameter of the Moon.

This year we have a new one — reports are circulating that this year’s Perseids will be the “brightest shower in recorded human history,” lighting up the night sky and even having some meteors visible during the day. We wish this were true… but no such thing is going to happen.

In this 30 second exposure, a meteor streaks across the sky during the annual Perseid meteor shower Thursday, Aug. 13, 2015, in Spruce Knob, West Virginia. Photo Credit: (NASA/Bill Ingalls)

For one thing, the Perseids never reach storm levels (thousands of meteors per hour). At best, they outburst from a normal rate between 80-100 meteors per hour to a few hundred per hour. The best Perseid performance of which we are aware occurred back in 1993, when the peak Perseid rate topped 300 meteors per hour. Last year also saw an outburst of just over 200 meteors per hour.

This year, we are expecting enhanced rates of about 150 per hour or so, but the increased number will be cancelled out by the bright Moon, the light of which will wash out the fainter Perseids. A meteor every couple of minutes is good, and certainly worth going outside to look, but it is hardly the “brightest shower in human history.” The Leonid meteor storms of the late 1990’s and early 2000’s were much more spectacular, and had rates 10 times greater than the best Perseid display.

So, if not this year’s Perseid shower, what was the greatest meteor show of all time? I think many meteor researchers would give that award to the 1833 Leonids, which had rates of tens of thousands, perhaps even 100,000, meteors per hour. During a good Perseid shower under ideal conditions, you can see about one meteor per minute. Now imagine yourself being back in 1833, on the night of Nov. 12. Looking outside, you would see something like 20 to 30 meteors PER SECOND. No wonder we read accounts like this one from South Carolina (Chambers, A Handbook of Descriptive and Practical Astronomy, Volume 1, 1889):

“Upwards of 100 lay prostrate on the ground…with their hands raised, imploring God to save the world and them. The scene was truly awful; for never did rain fall much thicker than the meteors fell towards the Earth; east, west, north and south, it was the same.”

Now, THAT’s a meteor shower. The 1833 storm had a profound effect on those that witnessed it; it also gave birth to modern meteor science. Those of us who study meteors dream of such a display happening sometime within our lifetimes.

But it won’t be caused by this year’s Perseids.

Cooke leads NASA’s Meteoroid Environment Office at the agency’s Marshall Space Flight Center.

 

Total Solar Eclipse: The Physics of Light

By Kevin Matyi

The motion of the moon is what causes eclipses, but the dramatic change in sunlight is what makes them so impressive to observers. But what exactly is happening when the moon passes in front of the sun?

The moon is blocking the sun’s light from reaching Earth, but there is more to the situation than just that. Their relative distance to Earth is one of the most important factors.

The sun is about 400 times farther from Earth than the moon and has a diameter about 400 times larger than the moon. As a result, both the sun and moon (near perigee) appear to be the same size in the sky, allowing the moon to perfectly block out the sun and cast a shadow on Earth during a total eclipse.

The shadow we see while in the path of totality is called the umbra, and the shadow of the surrounding partial eclipse is a penumbra. The shadow from an annular eclipse (when the moon appears smaller than the sun during an eclipse, and so a ring of light is visible around it) is called an anteumbra.

The physics of how each type of shadow is formed is difficult to explain but easy to visualize, so before I tell you about them, here is a picture (technically a ray diagram) of what happens during an eclipse:

Each of the three types of solar eclipse are caused by the moon blocking light from different parts of the sun.
Each of the three types of solar eclipse are caused by the moon blocking light from different parts of the sun.
Credit: Wikimedia Cmglee

For a total eclipse, the moon has to block out all of the sun’s light. To put the moon in the best position, imagine that a person on Earth is standing under the exact middle of the moon, the centerline of a total solar eclipse.

In this case, light coming from the middle of the sun is clearly going to be blocked by the moon, since it is directly in the way and visible light cannot penetrate rock. The most difficult light to block will be coming from the top and bottom of the sun.

To figure out whether the light will be blocked, a bit of drawing can help. If the light is coming from the exact bottom of the sun and you are wondering if a person can see the light while under the exact center of the moon, draw a line between where the light starts and the person’s eyes.

Does the moon get in the way of the line? If yes, then the person is experiencing a total solar eclipse. None of the sun’s light can get past the moon, so the sun is fully blocked.

If the answer is no, but the person is still standing under the center of the moon, then they are in an annular eclipse. The moon is in the perfect position to block all of the sun’s light, but it still fails to do so. In this case, it will appear to be a large black circle with a ring of sunlight called an annulus around it.

A partial eclipse is the most difficult to explain, since it has the most variability. All but a sliver of the sun may be blocked, or the moon can barely cover any of the sun. In general though, a partial solar eclipse happens when the moon is not quite directly between the observer and sun, but is still in the way of some sunlight.

You can use the same process for determining whether a person is experiencing a total solar eclipse to figure out if they are in the penumbral shadow of the moon. A slight complication is that the moon is off center, so it matters more where the origin point of the light is.

If the person is standing a little north of the moon’s center, then the line from origin to person should start from the sun’s southernmost point, the bottom, since the northern light is less likely to be blocked due to the moon being a bit more to the south from the person’s perspective.

If any of the sun’s light is blocked by the moon, then the person is experiencing a partial solar eclipse. The limit of this blockage, where only the slightest amount of sunlight is blocked, is the edge of the penumbra shadow.

If the moon is not blocking any light, then the moon may be close to the sun but there is no eclipse happening on that spot of Earth.