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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

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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[NASA]

What’s Up for March 2017?

What’s Up for March? The moon hides red star Aldebaran and crescents dazzle after dusk.

On March 4 the first quarter moon passes between Earth and the star Aldebaran, temporarily blocking our view of the star. This is called an occultation. 

The occultation begins and concludes at different times, depending on where you are when you view it.

The event should be easy to see from most of the U.S., Mexico, most of Central America, the Western Caribbean and Bermuda. 

Observers along a narrow path from Vancouver, British Columbia, to Hartford, Connecticut, will see the moon “graze” the star. The star will disappear and reappear repeatedly as hills and valleys on the moon alternately obscure and reveal it.

As seen from Earth, both Mercury and Venus have phases like our moon. That’s because they circle the sun inside Earth’s orbit. 

Planets that orbit between Earth and the sun are known as inner or inferior planets.

Inferior planets can never be at “opposition,” which is when the planet and the sun are on opposite sides of Earth.

But inferior planets can be at “conjunction,” which is when a planet, the sun and Earth are all in a straight line. 

Conjunction can happen once when the planet is on the opposite side of the sun from Earth and again when it’s on the same side of the sun as Earth. 

When a planet is on the opposite side of the sun from Earth, we say it is at “superior conjunction.” As the planet moves out from behind the sun and gets closer to Earth, we see less and less of the lit side. We see phases, similar to our moon’s phases. 

Mercury is at superior conjunction on March 6. 

A few weeks later, the planet emerges from behind the sun and we can once again observe it. By the end of March we’ll see a last-quarter Mercury.

 On April 20 Mercury reaches “inferior conjunction.”

Brilliant Venus is also racing toward its own inferior conjunction on March 25. Watch its crescent get thinner and thinner as the planet’s size appears larger and larger, because it is getting closer to Earth.

Finally, look for Jupiter to rise in the East. It will be visible all month long from late evening until dawn.

You can catch up on solar system missions and all of our missions at www.nasa.gov

Watch the full “What’s Up for March 2017″ video here: 

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