Caltech’s Astronomers Teach You What to Find in the Night Sky
Astronomy outreach on campus. Credit: Caltech
Editor’s note: Caltech will host a solar eclipse viewing party at the Cahill Center for Astronomy and Astrophysics and the adjacent space on April 8, 2024. Here in Pasadena, we will see it as a partial solar eclipse, where the shadow of the moon will cover part of the Sun over the course of 2 hours. At its peak at 11:13 AM, the Moon will cover almost 50% of the disk of the Sun.
by Shannon Stirone
On a dark-sky night, around 5,000 stars are visible to the naked eye, a tally that does not include the many galaxies, nebulae, and human-made objects that can be seen overhead. To understand what you are seeing when you look up in wonder means knowing not only how to find these objects but having an idea of what is there in the first place.
Scientists in Caltech’s Division of Physics, Mathematics and Astronomy have created a robust astronomy outreach program for both lovers of the night sky and those who have yet to discover the joy of stargazing. From science lectures to telescope viewings, these opportunities to connect with Institute astronomers prove that you do not need a degree to learn about the wonders of the universe.
Hunting in the Sky
Cameron Hummels, Caltech computational astrophysicist, runs the astronomy outreach program and manages, among other events, its Stargazing Lecture Series on Friday nights. These events are an ideal introduction to stargazing, Hummels says—no previous knowledge necessary. During these evenings, visitors can observe the cosmos through telescopes with guidance from expert scientists. The events take place on the athletic fields adjacent to the Cahill Center for Astronomy and Astrophysics. This past January, for instance, 500 visitors turned out for a chance to see a bright green comet called C/2022 E3 (ZTF) that was discovered by Caltech’s own Zwicky Transient Facility. Another 1,000 people came to view the solar eclipse in October 2023. Each month, the team gives guests the chance to glimpse some of the heavy hitters in the night sky.
An Astronomy on Tap event in Pasadena. Credit: Caltech
“We’ll look at the Orion Nebula or the Pleiades star cluster, the Andromeda Galaxy or the Hercules globular,” Hummels says. “And then, if there are planets up, we’ll observe those too.”
During any stargazing session, what is visible depends on the season, weather, and the brightness of the Moon. Because of its brightness, the Moon is the nemesis of any professional astronomer, though, as Hummels points out, it is simultaneously one of the most beautiful sights to behold through a telescope.
“I try to schedule our lecture nights to coincide with the first quarter Moon, because it’s always a spectacular telescope target,” he says. “You can look along its terminator line, the line separating sunlight from shadow, and see incredible detail in the craters illuminated from the side, sort of like landforms on Earth just prior to sunset. It is just amazing.”
“We just set up a few telescopes on the sidewalks and point them at whatever is interesting in the sky. When they do stop, there’s, I’d say, 95 percent joy. When you look through a telescope, and you see distant planets and distant galaxies, suddenly you remember, everything is so big, and we’re so small.””
Once you get beyond obvious celestial objects like the Moon, finding significant sights on your own can be a challenge, but the planets are a good place to start. Venus and Jupiter are two of the brightest objects in the night sky, often mistaken for very bright stars, Hummels notes.
Aside from their brightness, planets can be distinguished from stars by their lack of twinkling. The light from distant stars twinkles as it passes through our turbulent atmosphere, refracting and dancing as it reaches our eyes. But for nearby planets, this effect is minimized. The next time you see a bright, unwavering “star” in the sky, it may be a planet.
Beyond planets, look for the mighty Orion constellation in the winter sky to orient yourself. Orion’s famous belt is the easiest part to find: “You’ll see three bright stars packed into a short straight line,” Hummels says. “By following a line passing through those three stars to the ‘right’, it will intersect a red star, Aldebaran, the red eye of Taurus, the bull. Shortly past Aldebaran, this line will encounter a faint smudge on the sky known as the Pleiades Star Cluster or the ‘Seven Sisters.’”
Conversely, he explains, “by following the line of the three stars in Orion to the ‘left,’ you will see it points toward Sirius, the Dog Star, the brightest star in the sky. Directly ‘below’ the three stars in Orion’s belt is the Orion Nebula, a stellar nursery where stars are actively forming today. The Orion Nebula and the Pleiades Star Cluster are two of the most stunning deep sky objects to observe through a telescope.”
The Joy in the Stars
During the Dark Sky Festival in Death Valley National Park. Credit: Caltech
Hummels is passionate about astronomy education. He has co-organized a dozen dark sky festivals throughout California, including in Sequoia and Death Valley national parks, and he was the astronomer-in-residence at Grand Canyon National Park last autumn. In addition, he is the driving force behind the Caltech astronomy outreach events that occur around Los Angeles County, including on the sidewalks of Old Town Pasadena, where on select Saturday nights, volunteer astronomers from Caltech offer passersby the chance to peek through a telescope. He and the team also created a program called Science Train, in which they take public transportation around LA carrying solar telescopes and placards encouraging people to “Ask an Astrophysicist.”
There is magic in reaching folks who are not already tapped into the stars, Hummels says: “Providing people with their first opportunity to look through a telescope at the Moon or Saturn or some other astronomical object fills me with deep satisfaction.”
Those first moments at a telescope can be a powerful and moving experience, Hummels adds, noting that stargazing gives us one of the most precious feelings we humans can have: perspective. Experiences like these can catalyze whole careers in science.
Jessie Christiansen, an astrophysicist with the NASA Exoplanet Science Institute at Caltech, is also involved with the outreach program and says she especially loves the sidewalk astronomy in Old Town. “There are hundreds of people around, and they’re getting their ice cream, they’re going to the movies, and they’re waiting in line for bars,” she says. “And we just set up a few telescopes on the sidewalks and point them at whatever is interesting in the sky. When they do stop, there’s, I'd say, 95 percent joy. When you look through a telescope, and you see distant planets and distant galaxies, suddenly you remember, everything is so big, and we’re so small.”
Sidewalk science. Credit: Caltech
Even without a telescope, there are easy ways to experience some of the magic of the night sky. Hummels and Christiansen suggest downloading one of the stargazing apps that allow you to point your phone at a particular patch of sky and learn the story behind each bright dot: sometimes it is a star, sometimes it is Jupiter or Venus.
For those who like to pair a beer and fries with planets and stars, Caltech’s Astronomy on Tap events can provide a more casual opportunity to learn about the cosmos and the interesting research being done in astrophysics. Science presentations, pub trivia, live music, and telescopes, all while at enjoying a burger at an outdoor beer garden, makes these events truly unique.
It is perhaps no surprise that astronomers are willing to devote time outside of their normal working lives to spread the word about the wonders of space. The cosmos elicits grand feelings in all of us, whether you are viewing the Moon through a telescope for the first time, locating a globular cluster with a smartphone app, or just taking a second to notice what is around you once the sun has gone down. After all, the best place to start to understand the night sky is by simply looking up.