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Why Do X-Ray Mirrors Look So Unusual?

Does the object in this image look like a mirror? Maybe not, but that’s exactly what it is! To be more precise, it’s a set of mirrors that will be used on an X-ray telescope. But why does it look nothing like the mirrors you’re familiar with? To answer that, let’s first take a step back. Let’s talk telescopes.

How does a telescope work?

The basic function of a telescope is to gather and focus light to amplify the light’s source. Astronomers have used telescopes for centuries, and there are a few different designs. Today, most telescopes use curved mirrors that magnify and focus light from distant objects onto your eye, a camera, or some other instrument. The mirrors can be made from a variety of materials, including glass or metal.

Space telescopes like the James Webb and Hubble Space Telescopes use large mirrors to focus light from some of the most distant objects in the sky. However, the mirrors must be tailored for the type and range of light the telescope is going to capture—and X-rays are especially hard to catch.

X-rays versus mirrors

X-rays tend to zip through most things. This is because X-rays have much smaller wavelengths than most other types of light. In fact, X-rays can be smaller than a single atom of almost every element. When an X-ray encounters some surfaces, it can pass right between the atoms!

Doctors use this property of X-rays to take pictures of what’s inside you. They use a beam of X-rays that mostly passes through skin and muscle but is largely blocked by denser materials, like bone. The shadow of what was blocked shows up on the film.

This tendency to pass through things includes most mirrors. If you shoot a beam of X-rays into a standard telescope, most of the light would go right through or be absorbed. The X-rays wouldn’t be focused by the mirror, and we wouldn’t be able to study them.

X-rays can bounce off a specially designed mirror, one turned on its side so that the incoming X-rays arrive almost parallel to the surface and glance off it. At this shallow angle, the space between atoms in the mirror's surface shrinks so much that X-rays can't sneak through. The light bounces off the mirror like a stone skipping on water. This type of mirror is called a grazing incidence mirror.

A metallic onion

Telescope mirrors curve so that all of the incoming light comes to the same place. Mirrors for most telescopes are based on the same 3D shape — a paraboloid. You might remember the parabola from your math classes as the cup-shaped curve. A paraboloid is a 3D version of that, spinning it around the axis, a little like the nose cone of a rocket. This turns out to be a great shape for focusing light at a point.

Mirrors for visible and infrared light and dishes for radio light use the “cup” portion of that paraboloid. For X-ray astronomy, we cut it a little differently to use the wall. Same shape, different piece. The mirrors for visible, infrared, ultraviolet, and radio telescopes look like a gently-curving cup. The X-ray mirror looks like a cylinder with very slightly angled walls.

The image below shows how different the mirrors look. On the left is one of the Chandra X-ray Observatory’s cylindrical mirrors. On the right you can see the gently curved round primary mirror for the Stratospheric Observatory for Infrared Astronomy telescope.

If we use just one grazing incidence mirror in an X-ray telescope, there would be a big hole, as shown above (left). We’d miss a lot of X-rays! Instead, our mirror makers fill in that cylinder with layers and layers of mirrors, like an onion. Then we can collect more of the X-rays that enter the telescope, giving us more light to study.

Nested mirrors like this have been used in many X-ray telescopes. Above is a close-up of the mirrors for an upcoming observatory called the X-ray Imaging and Spectroscopy Mission (XRISM, pronounced “crism”), which is a Japan Aerospace Exploration Agency (JAXA)-led international collaboration between JAXA, NASA, and the European Space Agency (ESA).

The XRISM mirror assembly uses thin, gold-coated mirrors to make them super reflective to X-rays. Each of the two assemblies has 1,624 of these layers packed in them. And each layer is so smooth that the roughest spots rise no more than one millionth of a millimeter.

Why go to all this trouble to collect this elusive light? X-rays are a great way to study the hottest and most energetic areas of the universe! For example, at the centers of certain galaxies, there are black holes that heat up gas, producing all kinds of light. The X-rays can show us light emitted by material just before it falls in.

Stay tuned to NASA Universe on Twitter and Facebook to keep up with the latest on XRISM and other X-ray observatories.

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Meet Our Superhero Space Telescopes!

While the first exoplanets—planets beyond our solar system—were discovered using ground-based telescopes, the view was blurry at best. Clouds, moisture, and jittering air molecules all got in the way, limiting what we could learn about these distant worlds.

A superhero team of space telescopes has been working tirelessly to discover exoplanets and unveil their secrets. Now, a new superhero has joined the team—the James Webb Space Telescope. What will it find? Credit: NASA/JPL-Caltech

To capture finer details—detecting atmospheres on small, rocky planets like Earth, for instance, to seek potential signs of habitability—astronomers knew they needed what we might call “superhero” space telescopes, each with its own special power to explore our universe. Over the past few decades, a team of now-legendary space telescopes answered the call: Hubble, Chandra, Spitzer, Kepler, and TESS.

Much like scientists, space telescopes don't work alone. Hubble observes in visible light—with some special features (superpowers?)—Chandra has X-ray vision, and TESS discovers planets by looking for tiny dips in the brightness of stars.

Kepler and Spitzer are now retired, but we're still making discoveries in the space telescopes' data. Legends! All were used to tell us more about exoplanets. Spitzer saw beyond visible light into the infrared and was able to make exoplanet weather maps! Kepler discovered more than 3,000 exoplanets.

Three space telescopes studied one fascinating planet and told us different things. Hubble found that the atmosphere of HD 189733 b is a deep blue. Spitzer estimated its temperature at 1,700 degrees Fahrenheit (935 degrees Celsius). Chandra, measuring the planet’s transit using X-rays from its star, showed that the gas giant’s atmosphere is distended by evaporation.

Adding the James Webb Space Telescope to the superhero team will make our science stronger. Its infrared views in increased ranges will make the previously unseen visible.

Soon, Webb will usher in a new era in understanding exoplanets. What will Webb discover when it studies HD 189733 b? We can’t wait to find out! Super, indeed.

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Travel to Exotic Destinations in our Galaxy!

The planets beyond our solar system – exoplanets – are so far away, often trillions of miles, that we don’t have the technology to truly see them. Even the best photos show the planets as little more than bright dots. We’ve confirmed more than 5,000 exoplanets, but we think there are billions. Space telescopes like Hubble aren’t able to take photos of these far-off worlds, but by studying them in different wavelengths of light (colors), we’ve learned enough about conditions on these planets that we can illustrate them.

We know, thanks to the now-retired Spitzer Space Telescope, that there is a thick atmosphere on a planet called 55 Cancri e about 40 light-years away. And Hubble found silicate vapor in the atmosphere of this rocky world. We also know it’s scorching-close to its Sun-like star, so … lava. Lots and lots of lava. This planet is just one of the many that the James Webb Space Telescope will soon study, telling us even more about the lava world!

You can take a guided tour of this planet (and others) and see 360-degree simulations at our new Exoplanet Travel Bureau.

Travel to the most exotic destinations in our galaxy, including:

Kepler-16b, a planet with two suns.

Then there’s PSO J318.5-22, a world with no sun that wanders the galaxy alone. The nightlife would never end on a planet without a star.

TRAPPIST-1e, which will also be studied by the Webb Space Telescope, is one of seven Earth-sized planets orbiting a star about 40 light-years from Earth. It’s close enough that, if you were standing on this exoplanet, you could see our Sun as a star in the Leo constellation! You can also see it on the poster below: look for a yellow star to the right of the top person’s eye.

We haven’t found life beyond Earth (yet) but we’re looking. Meanwhile, we can imagine the possibility of red grass and other plants on Kepler-186f, a planet orbiting a red dwarf star.

We can also imagine what it might be like to skydive on a super-Earth about seven times more massive than our home planet. You would fall about 35% faster on a super-Earth like HD 40307g, making for a thrilling ride!

Any traveler is going to want to pick up souvenirs, and we have you covered. You can find free downloads of all the posters here and others! What are you waiting for? Come explore with us!

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Image credits: NASA/JPL-Caltech

See the Universe in a New Way with the Webb Space Telescope's First Images

Are you ready to see unprecedented, detailed views of the universe from the James Webb Space Telescope, the largest and most powerful space observatory ever made? Scroll down to see the first full-color images and data from Webb. Unfold the universe with us. ✨

Carina Nebula

This landscape of “mountains” and “valleys” speckled with glittering stars, called the Cosmic Cliffs, is the edge of the star-birthing Carina Nebula. Usually, the early phases of star formation are difficult to capture, but Webb can peer through cosmic dust—thanks to its extreme sensitivity, spatial resolution, and imaging capability. Protostellar jets clearly shoot out from some of these young stars in this new image.

Southern Ring Nebula

The Southern Ring Nebula is a planetary nebula: it’s an expanding cloud of gas and dust surrounding a dying star. In this new image, the nebula’s second, dimmer star is brought into full view, as well as the gas and dust it’s throwing out around it. (The brighter star is in its own stage of stellar evolution and will probably eject its own planetary nebula in the future.) These kinds of details will help us better understand how stars evolve and transform their environments. Finally, you might notice points of light in the background. Those aren’t stars—they’re distant galaxies.

Stephan’s Quintet

Stephan’s Quintet, a visual grouping of five galaxies near each other, was discovered in 1877 and is best known for being prominently featured in the holiday classic, “It’s a Wonderful Life.” This new image brings the galaxy group from the silver screen to your screen in an enormous mosaic that is Webb’s largest image to date. The mosaic covers about one-fifth of the Moon’s diameter; it contains over 150 million pixels and is constructed from almost 1,000 separate image files. Never-before-seen details are on display: sparkling clusters of millions of young stars, fresh star births, sweeping tails of gas, dust and stars, and huge shock waves paint a dramatic picture of galactic interactions.

WASP-96 b

WASP-96 b is a giant, mostly gas planet outside our solar system, discovered in 2014. Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) measured light from the WASP-96 system as the planet moved across the star. The light curve confirmed previous observations, but the transmission spectrum revealed new properties of the planet: an unambiguous signature of water, indications of haze, and evidence of clouds in the atmosphere. This discovery marks a giant leap forward in the quest to find potentially habitable planets beyond Earth.

Webb's First Deep Field

This image of galaxy cluster SMACS 0723, known as Webb’s First Deep Field, looks 4.6 billion years into the past. Looking at infrared wavelengths beyond Hubble’s deepest fields, Webb’s sharp near-infrared view reveals thousands of galaxies—including the faintest objects ever observed in the infrared—in the most detailed view of the early universe to date. We can now see tiny, faint structures we’ve never seen before, like star clusters and diffuse features and soon, we’ll begin to learn more about the galaxies’ masses, ages, histories, and compositions.

These images and data are just the beginning of what the observatory will find. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.

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Credits: NASA, ESA, CSA, and STScI

You Are Made of Stardust

Though the billions of people on Earth may come from different areas, we share a common heritage: we are all made of stardust! From the carbon in our DNA to the calcium in our bones, nearly all of the elements in our bodies were forged in the fiery hearts and death throes of stars.

The building blocks for humans, and even our planet, wouldn’t exist if it weren’t for stars. If we could rewind the universe back almost to the very beginning, we would just see a sea of hydrogen, helium, and a tiny bit of lithium.

The first generation of stars formed from this material. There’s so much heat and pressure in a star’s core that they can fuse atoms together, forming new elements. Our DNA is made up of carbon, hydrogen, oxygen, nitrogen, and phosphorus. All those elements (except hydrogen, which has existed since shortly after the big bang) are made by stars and released into the cosmos when the stars die.

Each star comes with a limited fuel supply. When a medium-mass star runs out of fuel, it will swell up and shrug off its outer layers. Only a small, hot core called a white dwarf is left behind. The star’s cast-off debris includes elements like carbon and nitrogen. It expands out into the cosmos, possibly destined to be recycled into later generations of stars and planets. New life may be born from the ashes of stars.

Massive stars are doomed to a more violent fate. For most of their lives, stars are balanced between the outward pressure created by nuclear fusion and the inward pull of gravity. When a massive star runs out of fuel and its nuclear processes die down, it completely throws the star out of balance. The result? An explosion!

Supernova explosions create such intense conditions that even more elements can form. The oxygen we breathe and essential minerals like magnesium and potassium are flung into space by these supernovas.

Supernovas can also occur another way in binary, or double-star, systems. When a white dwarf steals material from its companion, it can throw everything off balance too and lead to another kind of cataclysmic supernova. Our Nancy Grace Roman Space Telescope will study these stellar explosions to figure out what’s speeding up the universe’s expansion. 

This kind of explosion creates calcium – the mineral we need most in our bodies – and trace minerals that we only need a little of, like zinc and manganese. It also produces iron, which is found in our blood and also makes up the bulk of our planet’s mass!

A supernova will either leave behind a black hole or a neutron star – the superdense core of an exploded star. When two neutron stars collide, it showers the cosmos in elements like silver, gold, iodine, uranium, and plutonium.

Some elements only come from stars indirectly. Cosmic rays are nuclei (the central parts of atoms) that have been boosted to high speed by the most energetic events in the universe. When they collide with atoms, the impact can break them apart, forming simpler elements. That’s how we get boron and beryllium – from breaking star-made atoms into smaller ones.

Half a dozen other elements are created by radioactive decay. Some elements are radioactive, which means their nuclei are unstable. They naturally break down to form simpler elements by emitting radiation and particles. That’s how we get elements like radium. The rest are made by humans in labs by slamming atoms of lighter elements together at super high speeds to form heavier ones. We can fuse together elements made by stars to create exotic, short-lived elements like seaborgium and einsteinium.

From some of the most cataclysmic events in the cosmos comes all of the beauty we see here on Earth. Life, and even our planet, wouldn’t have formed without them! But we still have lots of questions about these stellar factories. 

In 2006, our Stardust spacecraft returned to Earth containing tiny particles of interstellar dust that originated in distant stars, light-years away – the first star dust to ever be collected from space and returned for study. You can help us identify and study the composition of these tiny, elusive particles through our Stardust@Home Citizen Science project.

Our upcoming Roman Space Telescope will help us learn more about how elements were created and distributed throughout galaxies, all while exploring many other cosmic questions. Learn more about the exciting science this mission will investigate on Twitter and Facebook.

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Take a good look: this is the black hole at the center of our galaxy.

In the inset image, gas in the glowing orange ring surrounds the black hole's event horizon, a boundary from which nothing can escape. The ring is created by light bending in the intense gravity around Sagittarius A*, which has a mass some four million times greater than our Sun. This groundbreaking image of Sagittarius A* was taken by the Event Horizon Telescope team with data from telescopes around the world. After the EHT's iconic image of M87*, released in 2019, this is only the second time a supermassive black hole has been directly observed with its shadow.

The wider look at the space around Sagittarius A* includes data contributed by several NASA missions. The orange specks and purple tendrils were captured in infrared light by the Hubble Space Telescope, and the blue clouds represent data from our orbiting Chandra X-ray Observatory.

Fall in to the whole story: https://www.nasa.gov/mission_pages/chandra/images/sagittarius-a-nasa-telescopes-support-event-horizon-telescope-in-studying-milky-ways.html

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CREDIT: X-ray: NASA/CXC/SAO; IR: NASA/HST/STScI. Inset: Radio (EHT Collaboration)

Our Weird and Wonderful Galaxy of Black Holes

Black holes are hard to find. Like, really hard to find. They are objects with such strong gravity that light can’t escape them, so we have to rely on clues from their surroundings to find them.

When a star weighing more than 20 times the Sun runs out of fuel, it collapses into a black hole. Scientists estimate that there are tens of millions of these black holes dotted around the Milky Way, but so far we’ve only identified a few dozen. Most of those are found with a star, each circling around the other. Another name for this kind of pair is a binary system.That’s because under the right circumstances material from the star can interact with the black hole, revealing its presence. 

The visualization above shows several of these binary systems found in our Milky Way and its neighboring galaxy. with their relative sizes and orbits to scale. The video even shows each system tilted the way we see it here from our vantage point on Earth. Of course, as our scientists gather more data about these black holes, our understanding of them may change.   

If the star and black hole orbit close enough, the black hole can pull material off of its stellar companion! As the material swirls toward the black hole, it forms a flat ring called an accretion disk. The disk gets very hot and can flare, causing bright bursts of light.

V404 Cygni, depicted above, is a binary system where a star slightly smaller than the Sun orbits a black hole 10 times its mass in just 6.5 days. The black hole distorts the shape of the star and pulls material from its surface. In 2015, V404 Cygni came out of a 25-year slumber, erupting in X-rays that were initially detected by our Swift satellite. In fact, V404 Cygni erupts every couple of decades, perhaps driven by a build-up of material in the outer parts of the accretion disk that eventually rush in. 

In other cases, the black hole’s companion is a giant star with a strong stellar wind. This is like our Sun’s solar wind, but even more powerful. As material rushes out from the companion star, some of it is captured by the black hole’s gravity, forming an accretion disk.

A famous example of a black hole powered by the wind of its companion is Cygnus X-1. In fact, it was the first object to be widely accepted as a black hole! Recent observations estimate that the black hole’s mass could be as much as 20 times that of our Sun. And its stellar companion is no slouch, either. It weighs in at about 40 times the Sun.

We know our galaxy is peppered with black holes of many sizes with an array of stellar partners, but we've only found a small fraction of them so far. Scientists will keep studying the skies to add to our black hole menagerie.

Curious to learn more about black holes? Follow NASA Universe on Twitter and Facebook to keep up with the latest from our scientists and telescopes.

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CAPSTONE: Testing a Path to the Moon

Before NASA's Artemis astronauts head to the Moon, a microwave oven-sized spacecraft will help lead the way. The Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment, or CAPSTONE, is a CubeSat mission set to launch in spring of 2022. For at least six months, the small spacecraft will fly a unique elongated path around the Moon. Its trajectory—known as a near rectilinear halo orbit—has never been flown before! Once tried and tested, the same orbit will be home to NASA’s future lunar space station Gateway. Here are five things to know:

1. The 55-pound (25 kg) spacecraft is equipped with solar arrays, a camera, and antennae for communication and navigation.

2. Powerful thrusters will help propel the CubeSat toward the Moon.

3. CAPSTONE will fly a unique elongated path around the Moon for at least six months.

4. At its closest approach, it will come within 2,100 miles (3,380 km) of the Moon's North Pole.

5. The same orbit will be home to Gateway— our future outpost for Artemis astronauts heading to the Moon and beyond.

CAPSTONE is commercially owned and operated by Advanced Space in Westminster, Colorado. NASA’s Small Spacecraft Technology program within the agency’s Space Technology Mission Directorate funds the demonstration mission. The program is based at NASA’s Ames Research Center in California’s Silicon Valley. The development of CAPSTONE’s navigation technology is supported by NASA’s Small Business Innovation Research and Small Business Technology Transfer program. The Artemis Campaign Development Division within NASA’s Exploration Systems Development Mission Directorate funds the launch and supports mission operations. The Launch Services Program at NASA’s Kennedy Space Center in Florida manages the launch.

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It's the International Day of Human Space Flight!

In this image, NASA astronaut Sunita Williams, Expedition 32 flight engineer, appears to touch the bright Sun during the mission's third spacewalk outside the International Space Station. Japan Aerospace Exploration Agency astronaut Aki Hoshide is visible in the reflection of Williams' helmet visor.

Today, April 12, is the International Day of Human Space Flight—marking Yuri Gagarin's first flight in 1961, and the first space shuttle launch in 1981.

As we honor global collaboration in exploration, we're moving forward to the Moon & Mars under the Artemis Accords.

Sign up to send your name around the Moon aboard Artemis I at go.nasa.gov/wearegoing.