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Throwback Thursday: Answers to Apollo Moon Landing Questions

The first six missions to the Moon helped us answer questions about our nearest celestial neighbor, but a curious public wanted to know more about how we did it. With the help of the NASA History Office, we’ve identified some of the most frequently asked questions surrounding the first time humans walked on the surface of another world. Read on and click here to check out our post from last week and the week before. 

Why do some shadows on the Moon appear to go in different directions?

For Apollo astronauts, the Sun wasn’t the sole source of light. The high reflectivity of the lunar surface or “albedo” means that the Moon's many craters, hills and rocks bounce sunlight to wash out the stars multiple shadows on objects. The highly uneven terrain means that shadows can have slightly different lengths, as well. For example, two astronauts standing several feet away from each other can have different shadow lengths because one may be on a slope.

While the Lunar Module itself was also reflective, Apollo astronauts had yet another bright source of light: Earth! To a moonwalker, a half-full Earth would be about 20 times brighter than a full Moon as seen from our home planet. This also explains why stars are not visible in pictures. Think about it: if you wanted to photograph all the stars that can be seen from Earth, would you want to do it during a full Moon? 

Why are there no blast craters under the Lunar Modules? 

The Moon has endured billions of years of bombardment from micrometeorites and large meteorites, compacting the dust into extremely dense rock. A thin layer of fine and powdery moondust covers the ground, but the dense rock beneath this layer makes it hard to penetrate the surface. That, paired with an engine thrusting in a vacuum means that the exhaust would expand rapidly outward instead of straight down like it would on Earth. The large engine nozzle. Still, many pictures clearly show dust markings radiating from the landing site. 

Can Humans Really Survive Passing Through the Van Allen Radiation Belts?

The short answer is yes, but with protection. The Van Allen radiation belts, named after their discoverer James van Allen, are regions high above Earth’s surface that trap highly charged particles that radiate off the Sun. This energetic region contains harmful radiation that would be lethal to anybody who encountered them unprotected. Thankfully, the 12 astronauts that passed through the belts did so relatively quickly in the comfort of their shielded spacecraft that had been tested to withstand high doses of radiation. Although all six crews had to pass through the Van Allen belts, the dosimeters indicated that they received a dosage no higher than that of a chest X-ray or a single CAT scan. 

Why are we going back to the Moon?

Exploring the Moon is only the first part in our mission to expand humanity’s presence on Mars and beyond. The Moon is the ideal stepping stone for testing technology that will enable us to expand humanity’s presence on Mars and beyond. Click here to learn more about the Artemis program that will take humans to the lunar surface within five years -- this time, to stay. Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

Astronomers used three of NASA's Great Observatories to capture this multiwavelength image showing galaxy cluster IDCS J1426.5+3508. It includes X-rays recorded by the Chandra X-ray Observatory in blue, visible light observed by the Hubble Space Telescope in green, and infrared light from the Spitzer Space Telescope in red. This rare galaxy cluster has important implications for understanding how these megastructures formed and evolved early in the universe.

How Astronomers Time Travel

Let’s add another item to your travel bucket list: the early universe! You don’t need the type of time machine you see in sci-fi movies, and you don’t have to worry about getting trapped in the past. You don’t even need to leave the comfort of your home! All you need is a powerful space-based telescope.

But let’s start small and work our way up to the farthest reaches of space. We’ll explain how it all works along the way.

This animation illustrates how fast light travels between Earth and the Moon. The farther light has to travel, the more noticeable its speed limit becomes.

The speed of light is superfast, but it isn’t infinite. It travels at about 186,000 miles (300 million meters) per second. That means that it takes time for the light from any object to reach our eyes. The farther it is, the more time it takes.

You can see nearby things basically in real time because the light travel time isn’t long enough to make a difference. Even if an object is 100 miles (161 kilometers) away, it takes just 0.0005 seconds for light to travel that far. But on astronomical scales, the effects become noticeable.

This infographic shows how long it takes light to travel to different planets in our solar system.

Within our solar system, light’s speed limit means it can take a while to communicate back and forth between spacecraft and ground stations on Earth. We see the Moon, Sun, and planets as they were slightly in the past, but it's not usually far enough back to be scientifically interesting.

As we peer farther out into our galaxy, we use light-years to talk about distances. Smaller units like miles or kilometers would be too overwhelming and we’d lose a sense of their meaning. One light-year – the distance light travels in a year – is nearly 6 trillion miles (9.5 trillion kilometers). And that’s just a tiny baby step into the cosmos.

The Sun’s closest neighboring star, Proxima Centauri, is 4.2 light-years away. That means we see it as it was about four years ago. Betelgeuse, a more distant (and more volatile) stellar neighbor, is around 700 light-years away. Because of light’s lag time, astronomers don’t know for sure whether this supergiant star is still there! It may have already blasted itself apart in a supernova explosion – but it probably has another 10,000 years or more to go.

What looks much like craggy mountains on a moonlit evening is actually the edge of a nearby, young, star-forming region NGC 3324 in the Carina Nebula. Captured in infrared light by the Near-Infrared Camera (NIRCam) on NASA’s James Webb Space Telescope, this image reveals previously obscured areas of star birth.

The Carina Nebula clocks in at 7,500 light-years away, which means the light we receive from it today began its journey about 3,000 years before the pyramids of Giza in Egypt were built! Many new stars there have undoubtedly been born by now, but their light may not reach Earth for thousands of years.

An artist’s concept of our Milky Way galaxy, with rough locations for the Sun and Carina nebula marked.

If we zoom way out, you can see that 7,500 light-years away is still pretty much within our neighborhood. Let’s look further back in time…

This stunning image by the NASA/ESA Hubble Space Telescope features the spiral galaxy NGC 5643. Looking this good isn’t easy; 30 different exposures, for a total of nine hours of observation time, together with Hubble’s high resolution and clarity, were needed to produce an image of such exquisite detail and beauty.

Peering outside our Milky Way galaxy transports us much further into the past. The Andromeda galaxy, our nearest large galactic neighbor, is about 2.5 million light-years away. And that’s still pretty close, as far as the universe goes. The image above shows the spiral galaxy NGC 5643, which is about 60 million light-years away! That means we see it as it was about 60 million years ago.

As telescopes look deeper into the universe, they capture snapshots in time from different cosmic eras. Astronomers can stitch those snapshots together to unravel things like galaxy evolution. The closest ones are more mature; we see them nearly as they truly are in the present day because their light doesn’t have to travel as far to reach us. We can’t rewind those galaxies (or our own), but we can get clues about how they likely developed. Looking at galaxies that are farther and farther away means seeing these star cities in ever earlier stages of development.

The farthest galaxies we can see are both old and young. They’re billions of years old now, and the light we receive from them is ancient since it took so long to traverse the cosmos. But since their light was emitted when the galaxies were young, it gives us a view of their infancy.

This animation is an artist’s concept of the big bang, with representations of the early universe and its expansion.

Comparing how fast objects at different distances are moving away opened up the biggest mystery in modern astronomy: cosmic acceleration. The universe was already expanding as a result of the big bang, but astronomers expected it to slow down over time. Instead, it’s speeding up!

The universe’s expansion makes it tricky to talk about the distances of the farthest objects. We often use lookback time, which is the amount of time it took for an object’s light to reach us. That’s simpler than using a literal distance, because an object that was 10 billion light-years away when it emitted the light we received from it would actually be more than 16 billion light-years away right now, due to the expansion of space. We can even see objects that are presently over 30 billion light-years from Earth, even though the universe is only about 14 billion years old.

This James Webb Space Telescope image shines with the light from galaxies that are more than 13.4 billion years old, dating back to less than 400 million years after the big bang.

Our James Webb Space Telescope has helped us time travel back more than 13.4 billion years, to when the universe was less than 400 million years old. When our Nancy Grace Roman Space Telescope launches in a few years, astronomers will pair its vast view of space with Webb’s zooming capabilities to study the early universe in better ways than ever before. And don’t worry – these telescopes will make plenty of pit stops along the way at other exciting cosmic destinations across space and time.

Learn more about the exciting science Roman will investigate on X and Facebook.

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Freaky fast and really awesome! NASA astronaut Jack Fischer posted this GIF to his social media Tuesday saying, “I was checking the view out the back window & decided to take a pic so you can see proof of our ludicrous speed! #SpaceIsAwesome”.

In case you didn’t know, the International Space Station travels 17,500 miles per hour as it orbits 250 miles above the Earth.

Currently, three humans are living and working there, conducting important science and research. The orbiting laboratory is home to more than 250 experiments, including some that are helping us determine the effects of microgravity on the human body. Research on the station will not only help us send humans deeper into space than ever before, including to Mars, but also benefits life here on Earth.

Follow NASA astronaut Jack Fischer on Instagram and Twitter. 

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

Taking Solar Science to New Heights

We're on the verge of launching a new spacecraft to the Sun to take the first-ever images of the Sun's north and south poles!

Credit: ESA/ATG medialab

Solar Orbiter is a collaboration between the European Space Agency (ESA) and NASA. After it launches — as soon as Feb. 9 — it will use Earth's and Venus's gravity to swing itself out of the ecliptic plane — the swath of space, roughly aligned with the Sun’s equator, where all the planets orbit. From there, Solar Orbiter's bird’s eye view will give it the first-ever look at the Sun's poles.

Credit: ESA/ATG medialab

The Sun plays a central role in shaping space around us. Its massive magnetic field stretches far beyond Pluto, paving a superhighway for charged solar particles known as the solar wind. When bursts of solar wind hit Earth, they can spark space weather storms that interfere with our GPS and communications satellites — at their worst, they can even threaten astronauts.

To prepare for potential solar storms, scientists monitor the Sun’s magnetic field. But from our perspective near Earth and from other satellites roughly aligned with Earth's orbit, we can only see a sidelong view of the Sun's poles. It’s a bit like trying to study Mount Everest’s summit from the base of the mountain.

Solar Orbiter will study the Sun's magnetic field at the poles using a combination of in situ instruments — which study the environment right around the spacecraft — and cameras that look at the Sun, its atmosphere and outflowing material in different types of light. Scientists hope this new view will help us understand not only the Sun's day-to-day activity, but also its roughly 11-year activity cycles, thought to be tied to large-scales changes in the Sun's magnetic field.

Solar Orbiter will fly within the orbit of Mercury — closer to our star than any Sun-facing cameras have ever gone — so the spacecraft relies on cutting-edge technology to beat the heat.

Credit: ESA/ATG medialab

Solar Orbiter has a custom-designed titanium heat shield with a calcium phosphate coating that withstands temperatures more than 900 degrees Fahrenheit — 13 times the solar heating that spacecraft face in Earth orbit. Five of the cameras look at the Sun through peepholes in that heat shield; one observes the solar wind out the side.

Over the mission’s seven-year lifetime, Solar Orbiter will reach an inclination of 24 degrees above the Sun’s equator, increasing to 33 degrees with an additional three years of extended mission operations. At closest approach the spacecraft will pass within 26 million miles of the Sun.

Solar Orbiter will be our second major mission to the inner solar system in recent years, following on August 2018’s launch of Parker Solar Probe. Parker has completed four close solar passes and will fly within 4 million miles of the Sun at closest approach.

Solar Orbiter (green) and Parker Solar Probe (blue) will study the Sun in tandem. 

The two spacecraft will work together: As Parker samples solar particles up close, Solar Orbiter will capture imagery from farther away, contextualizing the observations. The two spacecraft will also occasionally align to measure the same magnetic field lines or streams of solar wind at different times.

Watch the launch

The booster of a United Launch Alliance Atlas V rocket that will launch the Solar Orbiter spacecraft is lifted into the vertical position at the Vertical Integration Facility near Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida on Jan. 6, 2020. Credit: NASA/Ben Smegelsky

Solar Orbiter is scheduled to launch on Feb. 9, 2020, during a two-hour window that opens at 11:03 p.m. EST. The spacecraft will launch on a United Launch Alliance Atlas V 411 rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida.

Launch coverage begins at 10:30 p.m. EST on Feb. 9 at nasa.gov/live. Stay up to date with mission at nasa.gov/solarorbiter!

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7 Things You Need to Know About Small Satellites

1. Small satellites is the umbrella term for describing any satellite that is the size of an economy-sized washing machine all the way down to a CubeSat, which you can hold in your hand.

2. CubeSats come in multiple sizes defined by the U, which stands for unit. Making it the Unit unit. 1U CubeSats are cubes 4 inches (10 cm) on a side, weighing as little as 4 pounds. A 3U CubeSat is three 1Us hooked together, resembling a flying loaf of bread. A 6U CubeSat is two 3Us joined at the hip, like a flying cereal box. These are the three most common configurations.

Photo courtesy of the University of Michigan 

3. CubeSats were developed by researchers at California Polytechnic State University and Stanford University who wanted a standardized format to make launching them into space easier and to be small enough for students to get involved in designing, building and launching a satellite.

4. Small satellites often hitch a ride to space with another mission. If there’s room on the rocket of a larger mission, they’re in. CubeSats in particular deploy from a p-pod – poly-picosatellite orbital deployer – tucked on the underside of the upper stage of the rocket near the engine bell.

5. Small sats test technology at lower costs. Their small size and the relatively short amount of time it takes to design and build a small satellite means that if we want to test a new sensor component or a new way of making an observation from space, we can do so without being in the hole if it doesn’t work out. There’s no environment on Earth than can adequately recreate space, so sometimes the only way to know if new ideas work is to send them up and see.

6. Small sats force us to think of new ways to approach old problems. With a satellite the size of a loaf of bread, a cereal box, or a microwave oven, we don’t have a lot of room for the science instrument or power to run it. That means thinking outside the box. In addition to new and creative designs that include tape measures, customized camera lenses, and other off-the-shelf parts, we have to think of new ways of gathering all the data we need. One thing we’re trying out is flying small sat constellations – a bunch of the same kind of satellite flying in formation. Individually, each small sat sees a small slice of Earth below. Put them together and we start to see the big picture.

7. Small sats won’t replace big satellites. Size does matter when it comes to power, data storage, and how precise your satellite instrument is. Small satellites come with trade-offs that often mean coarser image resolution and shorter life-spans than their bigger sister satellites. However, small sat data can complement data collected by big satellites by covering more ground, by passing over more frequently, by flying in more dangerous orbits that big satellites avoid, and by continuing data records if there’s a malfunction or a wait between major satellite missions. Together they give us a more complete view of our changing planet.

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And we’re live!!!

NASA Astronaut Serena Auñoń Chancellor is here answering your questions during this Tumblr Answer Time. Tune in and join the fun!

Hello! I am an avid lover of the cosmos and all things too grand for our minds to grasp. I was wondering, honestly, how do you cope with the pressure of your jobs, or say the scale of what is on your shoulders? It's quite an impressive thing you do, and it just gets me curious as to how you deal with the expectations that come with this type of job? Like, when you go home at night and eat your dinner, go to bed, do you have to practice mindfulness? Thanks for answering these! Love you guys!!!

Boo! Did we get you? 🎃

This solar jack-o-lantern, captured by our Solar Dynamics Observatory (SDO) in October 2014, gets its ghoulish grin from active regions on the Sun, which emit more light and energy than the surrounding dark areas. Active regions are markers of an intense and complex set of magnetic fields hovering in the sun’s atmosphere.

The SDO has kept an unblinking eye on the Sun since 2010, recording phenomena like solar flares and coronal loops. It measures the Sun’s interior, atmosphere, magnetic field, and energy output, helping us understand our nearest star.

Grab the high-resolution version here.

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

Moon Mascot Needed!

Have you ever wanted to design something that could fly around the Moon? This is your opportunity. The Artemis II astronauts will use a zero gravity indicator during their mission to demonstrate when the Orion spacecraft has reached microgravity. This plushie needs to be soft, small, and importantly, remind us of home. The Moon Mascot contest challenges people of all ages from all over the world to submit a design to be made by NASA’s Thermal Blanket Lab and flown aboard Artemis II. To submit a design for the contest, visit: freelancer.com/moon-mascot

Astronaut Journal Entry - Unusual Attitude Recovery

Currently, six humans are living and working on the International Space Station, which orbits 250 miles above our planet at 17,500mph. Below you will find a real journal entry, written in space, by NASA astronaut Scott Tingle.

To read more entires from this series, visit our Space Blogs on Tumblr.

While flying fast-moving jets, we practice the art of recovering from unusual attitudes. We close our eyes, and let the instructor put the jet in an unexpected attitude. Sometimes straight up, sometimes straight down, sometimes upside down, and sometimes anything in-between. The goal is to open our eyes, analyze the situation and make rapid and smooth corrections to power and attitude to effect a speedy recovery to straight and level flight without departing controlled flight, or having to endure high G’s, or experiencing big losses of altitude. 

Sometimes, when I crawl into my crew quarters on the space station, it is very dark – just like closing our eyes in the jet. And then, as I sleep, my body floats around and changes position. When I awake in total darkness, I have to figure out what attitude I am in relative to my crew quarters and then right myself.  “Unusual Attitude Recovery” can be pretty funny. And sometimes, my heart can get pumping as I awake and realize I don’t know what my attitude is. I execute my procedures to figure out what my attitude is, and then correct it. At first, it used to take me a while to realize. But now, it is second nature – and it always brings a smile to my face.

Find more ‘Captain’s Log’ entries HERE.

Follow NASA astronaut Scott Tingle on Instagram and Twitter.

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