neptune and triton

Chasing the Shadow of Neptune’s Moon Triton

Our Flying Observatory

Our flying observatory, called SOFIA, carries a 100-inch telescope inside a Boeing 747SP aircraft. Scientists onboard study the life cycle of stars, planets (including the atmosphere of Mars and Jupiter), nearby planetary systems, galaxies, black holes and complex molecules in space.

AND on Oct. 5, SOFIA is going on a special flight to chase the shadow of Neptune’s moon Triton as it crosses Earth’s surface!

In case you’re wondering, SOFIA stands for: Stratospheric Observatory for Infrared Astronomy.


Triton is 1,680 miles (2,700 km) across, making it the largest of the 13 moons orbiting Neptune. Unlike most large moons in our solar system, Triton orbits in the opposite direction of Neptune, called a retrograde orbit. This backward orbit leads scientists to believe that Triton formed in an area past Neptune, called the Kuiper Belt, and was pulled into its orbit around Neptune by gravity. 

The Voyager 2 spacecraft flew past Neptune and Triton in 1989 and found that Triton’s atmosphere is made up of mostly nitrogen…but it has not been studied in nearly 16 years!

Occultations are Eclipse-Like Events

An occultation occurs when an object, like a planet or a moon, passes in front of a star and completely blocks the light from that star. As the object blocks the star’s light, it casts a faint shadow on Earth’s surface

But unlike an eclipse, these shadows are not usually visible to the naked eye because the star and object are much smaller and not nearly as bright as our sun. Telescopes with special instruments can actually see these shadows and study the star’s light as it passes near and around the object – if they can be in the right place on Earth to catch the shadow.

Chasing Shadows

Scientists have been making advanced observations of Triton and a background star. They’ve calculated exactly where Triton’s faint shadow will fall on Earth! Our SOFIA team has designed a flight path that will put SOFIA (the telescope and aircraft) exactly in the center of the shadow at the precise moment that Triton and the star will align. 

This is no easy feat because the shadow is moving at more than 53,000 mph while SOFIA flies at Mach 0.85 (652 mph), so we only have about two minutes to catch the shadow!! But our SOFIA team has previously harnessed the aircraft’s mobility to study Pluto from inside the center of its occultation shadow, and is ready to do it again to study Triton!

What We Learn From Inside the Shadow

From inside the shadow, our team on SOFIA will study the star’s light as it passes around and through Triton’s atmosphere. This allows us to learn more about Triton’s atmosphere, including its temperature, pressure, density and composition! 

Our team will use this information to examine if Triton’s atmosphere has changed since our Voyager 2 spacecraft flew past it in 1989. That’s a lot of information from a bit of light inside a shadow! Similar observations of Uranus in 1977, from our previous flying observatory, led to the discovery of rings around that planet!

International Ground-Based Support

Ground-based telescopes across the United States and Europe – from Scotland to the Canary Islands – will also be studying Triton’s occultation. Even though most of these telescopes will not be in the center of the shadow, the simultaneous observations, from different locations on Earth, will give us information about how Triton’s atmosphere varies across its latitudes. 

This data from across the Earth and from onboard SOFIA will help researchers understand how Triton’s atmosphere is distorted at different locations by its high winds and its strong tides!

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Which Planet to Destroy?

I have no real explanation as to how this situation would come up, but I had a thought: An inter-galactic  being (Galactus or the likes) comes to earth to devour the planet Earth, but a few humans go to try to reason with it.

Human 1: Please, spare our world, there are countless lives that call this place home, would you destroy it just for one quick meal?

Alien: Listen, this may sound rough to you, but this is my life every day. I gotta eat too, you know. Circle of life.

Human 2: But why this world? There are so many others that don’t have life on them.

Alien: Because your planet is right here and I’m hungry. Do you know how long it’s been since I last ate a planet? Too long.

Human: Please, this is our home. Our families are here, our children, our friends. We would do anything if you would spare this world.

Alien: *Sigh* Fine. I’ll spare your world, on one condition. I still need to eat. Find me a planet I can devour or I will consume your Earth.

The two humans look at each other and lower their voices as they discuss their options.

Human 1: What planet should we tell him to go eat?

Human 2: I think it’s gonna have to be one in our solar system, there’s no way he’s going to agree to go too far if he’s really as hungry as he says he is. But which one?

Human 1: Well definitely not Jupiter, it’s gravity keeps Earth safe from a lot of asteroids.

Human 2: Mars?

Human 1: Mars?! Are you kidding me? We can’t give up Mars, the Curiosity Rover’s there, and also, I want to visit Mars someday.

Human 2: That’s your reasoning, really?

Alien: My patience runs short. Make your decision.

Human 1 (to H2): Okay, look, shut up, we can’t give him Mars. End of story. Or Jupiter. Venus?

Human 2: I don’t know, Venus is really close to Earth, it might negatively affect us if our sister planet just disappeared from the sky. What about a farther planet, like Pluto?

Human 1: Yeah, but Pluto’s technically not a planet anymore.

Human 2: Do you really think this guy’s going to turn down our offer just on a technicality?

Human 1: Maybe.

Human 2: We don’t have time for this. Fine, what’s the next farthest away planet? Neptune? Do you have any objections with that?!

Human 1: Ummm, well, I don’t know, I think some people say one of Neptune’s moons might be habitable. They think it might have water if the moon kept some internal hea-

Human 2: I am not going to die today because you’re an idiot who can’t prioritize. This guy is going to eat a planet today, and so help me, it’s not going to be Earth with its definitely habitable characteristics, doYouUnderstandMe?!

Human 1: …*nods*

Human 2: Good. *turning up to yell back to the alien* We’ve made a decision, if you will listen, oh great being. We ask that you spare Earth, the third planet from our star, and instead eat another, Neptune, the eighth planet in our solar system. It is much larger, which should  satisfy your great hunger much better than our small home worl-

Human 1: Oh wait, did you know that Neptune actually has rings, they’re small and hard to see, but they-

Human 2: I swear, if this guy doesn’t kill us all, I will kill you