The last time the moon blocked out the sun, in 2017, the skies above Las Vegas were covered in clouds and rain poured down across the Valley. It was a rare celestial event obscured by rare weather for a desert city.

A team of UNLV Engineering students and faculty is hoping that the weather for two upcoming solar eclipses won’t put a damper on their views — and more importantly, their research — into the upper reaches of the Earth’s atmosphere. 

As part of NASA’s Nationwide Eclipse Ballooning Project, UNLV students, in partnership with the University of Nevada, Reno, will launch a scientific balloon — carrying a 12-pound payload and livestreaming cameras — 100,000 feet into the stratosphere to capture engineering data during the extraordinary cosmic events.

The first launch will take place on Oct. 14, when portions of North America will experience an annular solar eclipse, a warm-up to the slightly more awe-inspiring total solar eclipse on April 8, 2024. The annular eclipse happens when the moon passes between the sun and Earth while it is at its farthest point from Earth. The amazing event will be visible in Las Vegas and will pass directly through northern and Eastern Nevada, including Winnemucca, Nevada, where the UNLV team will be located at go time. 

For the total solar eclipse, the team, with additional experiments in tow, will have to travel to Texas to be in the path of totality. Or, as UNLV cosmology expert and computer scientist Paul La Plante says, “the right place, at the right time.”

The project gives UNLV students the chance to do some “cool engineering stuff,” according to project lead and engineering professor Matt Pusko, but it’s primarily an opportunity to engage a captive audience of Americans who will be looking up into the skies — with NASA-approved solar eclipse glasses — in back-to-back cosmic events.

“It’s an overall educational experience for everyone in the nation,” he said. Pusko is also visiting local classrooms in the leadup to both events.

Since it's a good time for everyone to learn a little about the solar system and how we’re quite lucky, as Earth inhabitants, to experience solar eclipses, we’re turning to La Plante for everything we need to know about solar eclipses.

What happens during an eclipse?

Broadly speaking, an eclipse happens when three celestial objects are in alignment. The two types we’re most familiar with are lunar eclipses (when the Earth passes between the sun and the moon), and solar eclipses (when the moon passes between the sun and the Earth). 

The fact we have solar eclipses is kind of a cosmic accident: The sun and moon have similar apparent sizes in the sky (mathematically speaking, they subtend a comparable solid angle) because the sun is about 400 times larger than the moon but also about 400 times farther away. Nothing in our solar system formation dictates this has to be the case, so we’re very lucky to have solar eclipses as we know them!

What can we learn from eclipses?

In general, solar eclipses are scientifically interesting because the moon blocks out most of the light from the sun. What this means is that we can use our telescopes to see things that the sun usually makes it difficult to observe directly. For example, over 100 years ago scientists used observations of stars that happened to be close in the sky to the sun during a solar eclipse to experimentally confirm Einstein’s theory of General Relativity.

These days, we can use the moon blocking light from the sun to study the corona, a very hot “halo” of plasma (superheated gas) surrounding the sun that is still mysterious in some ways. For example, the corona is much hotter than the surface of the sun, and we’re not exactly sure why.

What are the differences between an annular solar eclipse and a total solar eclipse? Does one event top the other?

The “annular” solar eclipse that we’ll have this year is different from the “total” solar eclipse that we usually think of. For an annular eclipse, the moon is actually a little bit further away from Earth than usual. Because the moon orbits the Earth in a slightly elliptical orbit rather than a perfect circle, its distance from Earth varies over the course of this orbit. 

When a solar eclipse happens while the moon is further away, the moon isn’t quite as large in the sky as the sun, so not all of the light is blocked out. As a result, we still see a small “ring” or annulus of light from the sun around the moon. For a total solar eclipse, the moon blocks out almost all of the light from the sun, which makes for a much more breathtaking show. The total solar eclipse also results in better science, for the same reason that the moon blocks out more of the light of the sun. The annular solar eclipse is still cool though!

Do you need eye protection for annular and total eclipses? 

Yes, you absolutely need eye protection for both types of eclipses. The annular solar eclipse will block out a maximum of about 90% of the sun’s light, while total solar eclipses block out more than 99% of the sun’s light. 

Even for a total solar eclipse though, you should use eye protection, as that less-than-1% brightness is still enough to cause eye damage after just a few minutes. You can use solar eclipse glasses or pinhole cameras to safely observe the sun during either kind of eclipse — or even when there isn’t an eclipse!

How does the rarity of being able to observe an eclipse add to the allure of the event?

Eclipses don’t happen very often, so it definitely makes them fun! Due to the relative tilt between the Earth-moon orbit and the Earth-sun orbit, eclipses only happen a few times a year (instead of every month if they were perfectly aligned).

Compounding this, the path of the moon's shadow on Earth is only a few hundred miles wide, and the whole event only lasts a few minutes at a given spot on the Earth, so you have to be lucky to be in the right place at the right time. That’s why we only have a solar eclipse that passes over the continental U.S. typically once every few years. I’m personally really looking forward to this one!