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Throwback Thursday: Frequently Asked Questions about Apollo

In celebration of the 50th anniversary of Apollo 11, we’ll be sharing answers to some frequently asked questions about the first time humans voyaged to the Moon. Answers have been compiled from archivists in the NASA History Office.

How many people worked on the Apollo program?

At the height of Apollo in 1965, about 409,900 people worked on some aspect of the program, but that number doesn’t capture it all.

It doesn’t represent the people who worked on mission concepts or spacecraft design, such as the engineers who did the wind tunnel testing of the Apollo Command Module and then moved on to other projects. The number also doesn’t represent the NASA astronauts, mission controllers, remote communications personnel, etc. who would have transferred to the Apollo program only after the end of Gemini program (1966-1967). There were still others who worked on the program only part-time or served on temporary committees. In the image above are three technicians studying an Apollo 14 Moon rock in the Lunar Receiving Laboratory at Johnson Space Center. From left to right, they are Linda Tyler, Nancy Trent and Sandra Richards.

How many people have walked on the Moon so far?

This artwork portrait done by spaceflight historian Ed Hengeveld depicts the 12 people who have walked on the Moon so far. In all, 24 people have flown to the Moon and three of them, John Young, Jim Lovell and Gene Cernan, have made the journey twice.  

But these numbers will increase.

Are the U.S. flags that were planted on the Moon still standing?

Every successful Apollo lunar landing mission left a flag on the Moon but we don’t know yet whether all are still standing. Some flags were set up very close to the Lunar Module and were in the blast radius of its ascent engine, so it’s possible that some of them could have been knocked down. Neil Armstrong and Buzz Aldrin both reported that the flag had been knocked down following their ascent. 

Our Lunar Reconnaissance Orbiter took photographs of all the Apollo lunar landing sites. In the case of the Apollo 17 site, you can see the shadow of the upright flag.

But why does it look like it’s waving?

The flags appear to “wave” or “flap” but actually they’re swinging. Swinging motions on Earth are dampened due to gravity and air resistance, but on the Moon any swinging motion can continue for much longer. Once the flags settled (and were clear of the ascent stage exhaust), they remained still.  And how is the flag hanging? Before launching, workers on the ground had attached a horizontal rod to the top of each flag for support, allowing it to be visible in pictures and television broadcasts to the American public. Armstrong and Aldrin did not fully extend the rod once they were on the Moon, giving the flag a ripple effect. The other astronauts liked the ripple effect so much that they also did not completely extend the rod. 

Why don’t we see stars in any of the pictures?

Have you ever taken a photo of the night sky with your phone or camera? You likely won’t see any stars because chances are your camera’s settings are set to short exposure time only lets it quickly take in the light off the bright objects closest to you. It’s the same reason you generally don’t see stars in spacewalk pictures from the International Space Station. There’s no use for longer exposure times to get an image like this one of Bruce McCandless in 1984 as seen Space Shuttle Challenger (STS-41B).

The Hasselblad cameras that Apollo astronauts flew with were almost always set to short exposure times. And why didn’t the astronauts photograph the stars? Well, they were busy exploring the Moon!

When are we going back to the Moon?

The first giant leap was only the beginning. Work is under way to send the first woman and the next man to the Moon in five years. As we prepare to launch the next era of exploration, the new Artemis program is the first step in humanity’s presence on the the Moon and beyond.

Keep checking back for more answers to Apollo FAQs.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com. 

Hadas Cohen

Hot New Planetary System Just Dropped.

We hope you like your planetary systems extra spicy. 🔥

A new system of seven sizzling planets has been discovered using data from our retired Kepler space telescope.

Named Kepler-385, it’s part of a new catalog of planet candidates and multi-planet systems discovered using Kepler.

The discovery helps illustrate that multi-planetary systems have more circular orbits around the host star than systems with only one or two planets.

Our Kepler mission is responsible for the discovery of the most known exoplanets to date. The space telescope’s observations ended in 2018, but its data continues to paint a more detailed picture of our galaxy today.

Here are a few more things to know about Kepler-385:

All seven planets are between the size of Earth and Neptune.

Its star is 10% larger and 5% hotter than our Sun.

This system is one of over 700 that Kepler’s data has revealed.

The planets’ orbits have been represented in sound.

Now that you’ve heard a little about this planetary system, get acquainted with more exoplanets and why we want to explore them.

Make sure to follow us on Tumblr for your regular dose of space!

Black Holes Dine on Stellar Treats!

See that tiny blob of light, circled in red? Doesn’t look like much, does it? But that blob represents a feast big enough to feed a black hole around 30 million times the mass of our Sun! Scientists call these kinds of stellar meals tidal disruption events, and they’re some of the most dramatic happenings in the cosmos.

Sometimes, an unlucky star strays too close to a black hole. The black hole’s gravity pulls on the star, causing it to stretch in one direction and squeeze in another. Then the star pulls apart into a stream of gas. This is a tidal disruption event. (If you’re worried about this happening to our Sun – don’t. The nearest black hole we know about is over 1,000 light-years away. And black holes aren’t wild space vacuums. They don’t go zipping around sucking up random stars and planets. So we’re pretty safe from tidal disruption events!)

The trailing part of the stream gets flung out of the system. The rest of the gas loops back around the black hole, forming a disk. The material circling in the disk slowly drifts inward toward the black hole’s event horizon, the point at which nothing – not even light – can escape. The black hole consumes the gas and dust in its disk over many years.

Sometimes the black hole only munches on a passing star – we call this a partial tidal disruption event. The star loses some of its gas, but its own gravity pulls it back into shape before it passes the black hole again. Eventually, the black hole will have nibbled away enough material that the star can’t reform and gets destroyed.

We study tidal disruptions, both the full feasts and the partial snacks, using many kinds of telescopes. Usually, these events are spotted by ground-based telescopes like the Zwicky Transient Facility and the All-Sky Automated Survey for Supernovae network.

They alert other ground- and space-based telescopes – like our Neil Gehrels Swift Observatory (illustrated above) and the European Space Agency’s XMM-Newton – to follow up and collect more data using different wavelengths, from visible light to X-rays. Even our planet-hunting Transiting Exoplanet Survey Satellite has observed a few of these destructive wonders!

We’re also studying disruptions using multimessenger astronomy, where scientists use the information carried by light, particles, and space-time ripples to learn more about cosmic objects and occurrences.

But tidal disruptions are super rare. They only happen once every 10,000 to 100,000 years in a galaxy the size of our own Milky Way. Astronomers have only observed a few dozen events so far. By comparison, supernovae – the explosive deaths of stars – happen every 100 years or so in a galaxy like ours.

That’s why scientists make their own tidal disruptions using supercomputers, like the ones shown in the video here. Supercomputers allow researchers to build realistic models of stars. They can also include all of the physical effects they’d experience whipping ‘round a black hole, even those from Einstein’s theory of general relativity. They can alter features like how close the stars get and how massive the black holes are to see how it affects what happens to the stars. These simulations will help astronomers build better pictures of the events they observe in the night sky.

Keep up with what’s happening in the universe and how we study it by following NASA Universe on Twitter and Facebook.

Make sure to follow us on Tumblr for your regular dose of space!

秋山莉奈