Why Do X-Ray Mirrors Look So Unusual?
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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Magnetospheres: How Do They Work?
The sun, Earth, and many other planets are surrounded by giant magnetic bubbles.
Space may seem empty, but it’s actually a dynamic place, dominated by invisible forces, including those created by magnetic fields. Magnetospheres – the areas around planets and stars dominated by their magnetic fields – are found throughout our solar system. They deflect high-energy, charged particles called cosmic rays that are mostly spewed out by the sun, but can also come from interstellar space. Along with atmospheres, they help protect the planets’ surfaces from this harmful radiation.
It’s possible that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, so finding magnetospheres around other planets is a big step toward determining if they could support life.
But not all magnetospheres are created equal – even in our own backyard, not all planets in our solar system have a magnetic field, and the ones we have observed are all surprisingly different.
Earth’s magnetosphere is created by the constantly moving molten metal inside Earth. This invisible “force field” around our planet has an ice cream cone-like shape, with a rounded front and a long, trailing tail that faces away from the sun. The magnetosphere is shaped that way because of the constant pressure from the solar wind and magnetic fields on the sun-facing side.
Earth’s magnetosphere deflects most charged particles away from our planet – but some do become trapped in the magnetic field and create auroras when they rain down into the atmosphere.
We have several missions that study Earth’s magnetosphere – including the Magnetospheric Multiscale mission, Van Allen Probes, and Time History of Events and Macroscale Interactions during Substorms (also known as THEMIS) – along with a host of other satellites that study other aspects of the sun-Earth connection.
Mercury, with a substantial iron-rich core, has a magnetic field that is only about 1% as strong as Earth’s. It is thought that the planet’s magnetosphere is stifled by the intense solar wind, limiting its strength, although even without this effect, it still would not be as strong as Earth’s. The MESSENGER satellite orbited Mercury from 2011 to 2015, helping us understand our tiny terrestrial neighbor.
After the sun, Jupiter has by far the biggest magnetosphere in our solar system – it stretches about 12 million miles from east to west, almost 15 times the width of the sun. (Earth’s, on the other hand, could easily fit inside the sun.) Jupiter does not have a molten metal core like Earth; instead, its magnetic field is created by a core of compressed liquid metallic hydrogen.
One of Jupiter’s moons, Io, has intense volcanic activity that spews particles into Jupiter’s magnetosphere. These particles create intense radiation belts and the large auroras around Jupiter’s poles.
Ganymede, Jupiter’s largest moon, also has its own magnetic field and magnetosphere – making it the only moon with one. Its weak field, nestled in Jupiter’s enormous shell, scarcely ruffles the planet’s magnetic field.
Our Juno mission orbits inside the Jovian magnetosphere sending back observations so we can better understand this region. Previous observations have been received from Pioneers 10 and 11, Voyagers 1 and 2, Ulysses, Galileo and Cassini in their flybys and orbits around Jupiter.
Saturn’s moon Enceladus transforms the shape of its magnetosphere. Active geysers on the moon’s south pole eject oxygen and water molecules into the space around the planet. These particles, much like Io’s volcanic emissions at Jupiter, generate the auroras around the planet’s poles. Our Cassini mission studies Saturn’s magnetic field and auroras, as well as its moon Enceladus.
Uranus’ magnetosphere wasn't discovered until 1986 when data from Voyager 2’s flyby revealed weak, variable radio emissions. Uranus’ magnetic field and rotation axis are out of alignment by 59 degrees, unlike Earth’s, whose magnetic field and rotation axis differ by only 11 degrees. On top of that, the magnetic field axis does not go through the center of the planet, so the strength of the magnetic field varies dramatically across the surface. This misalignment also means that Uranus’ magnetotail – the part of the magnetosphere that trails away from the sun – is twisted into a long corkscrew.
Neptune’s magnetosphere is also tilted from its rotation axis, but only by 47. Just like on Uranus, Neptune’s magnetic field strength varies across the planet. This also means that auroras can be seen away from the planet’s poles – not just at high latitudes, like on Earth, Jupiter and Saturn.
Does Every Planet Have a Magnetosphere?
Neither Venus nor Mars have global magnetic fields, although the interaction of the solar wind with their atmospheres does produce what scientists call an “induced magnetosphere.” Around these planets, the atmosphere deflects the solar wind particles, causing the solar wind’s magnetic field to wrap around the planet in a shape similar to Earth’s magnetosphere.
What About Beyond Our Solar System?
Outside of our solar system, auroras, which indicate the presence of a magnetosphere, have been spotted on brown dwarfs – objects that are bigger than planets but smaller than stars.
There’s also evidence to suggest that some giant exoplanets have magnetospheres. As scientists now believe that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, finding magnetospheres around exoplanets is a big step in finding habitable worlds.
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Say hello to spiral galaxy NGC 1097 👋
About 45 million light-years away, in another corner of the cosmos, lies spiral galaxy NGC 1097. Though this Hubble Space Telescope image zooms in toward the core, the galaxy’s vast spiral arms span over 100,000 light-years as they silently sweep through space. At the heart of this galaxy lurks a black hole that is about 100 million times as massive as the Sun.
The supermassive black hole is voraciously eating up surrounding matter, which forms a doughnut-shaped ring around it. Matter that's pulled into the black hole releases powerful radiation, making the star-filled center of the galaxy even brighter. Hubble’s observations have led to the discovery that while the material that is drawn toward NGC 1097’s black hole may be doomed to die, new stars are bursting into life in the ring around it.
This sparkling spiral galaxy is especially interesting to both professional scientists and amateur astronomers. It is a popular target for supernova hunters ever since the galaxy experienced three supernovas in relatively rapid succession — just over a decade, between 1992 and 2003. Scientists are intrigued by the galaxy’s satellites — smaller “dwarf” galaxies that orbit NGC 1097 like moons. Studying this set of galaxies could reveal new information about how galaxies interact with each other and co-evolve.
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Seeing El Niño…From Space
First, What is El Niño?
This irregularly occurring weather phenomenon is created through an abnormality in wind and ocean circulation. When it originates in the equatorial Pacific Ocean. El Niño has wide-reaching effects. In a global context, it affects rainfall, ocean productivity, atmospheric gases and winds across continents. At a local level, it influences water supplies, fishing industries and food sources.
What About This Year’s El Niño
This winter, weather patterns may be fairly different than what is typical — all because of unusually warm ocean water in the east equatorial Pacific, aka El Niño. California is expected to get more rain while Australia is expected to get less. Since this El Niño began last summer, the Pacific Ocean has already experienced an increase in tropical storms and a decrease in phytoplankton.
How Do We See El Niño?
Here are some of El Niño’s key impacts and how we study them from space:
Rainfall:
El Niño often spurs a change in rainfall patterns that can lead to major flooding, landslides and droughts across the globe.
How We Study It: Our Global Precipitation Measurement mission (GPM), tracks precipitation worldwide and creates global precipitation maps updated every half-hour using data from a host of satellites. Scientists can then use the data to study changes in rain and snow patterns. This gives us a better understanding of Earth’s climate and weather systems.
Hurricanes:
El Niño also influences the formation of tropical storms. El Niño events are associated with fewer hurricanes in the Atlantic, but more hurricanes and typhoons in the Pacific.
How We Study It: We have a suite of instruments in space that can study various aspects of storms, such as rainfall activity, cloud heights, surface wind speed and ocean heat.
Ocean Ecology:
While El Niño affects land, it also impacts the marine food web, which can be seen in the color of the ocean. The hue of the water is influenced by the presence of tiny plants, sediments and colored dissolved organic material. During El Niño conditions, upwelling is suppressed and the deep, nutrient-rich waters aren’t able to reach the surface, causing less phytoplankton productivity. With less food, the fish population declines, severely affecting fishing industries.
How We Study It: Our satellites measure the color of the ocean to derive surface chlorophyll, a pigment in phytoplankton, and observe lower total chlorophyll amounts during El Niño events in the equatorial Pacific Ocean.
Ozone:
El Niño also influences ozone — a compound that plays an important role in the Earth system and human health. When El Niño occurs, there is a substantial change in the major east-west tropical circulation, causing a significant redistribution of atmospheric gases like ozone.
How We Study It: Our Aura satellite is used to measure ozone concentrations in the upper layer of the atmosphere. With more than a decade of Aura data, researchers are able to separate the response of ozone concentrations to an El Niño from its response to change sin human activity, such as manmade fires.
Fires:
El Niño conditions shift patters of rainfall and fire across the tropics. During El Niño years, the number and intensity of fires increases, especially under drought conditions in regions accustomed to wet weather. These fires not only damage lands, but also emit greenhouse gases that trap heat in the atmosphere and contribute to global warming.
How We Study It: Our MODIS instruments on Aqua and Terra satellites provide a global picture of fire activity. MODIS was specifically designed to observe fires, allowing scientists to discern flaming from smoldering burns.
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What's the most beautiful natural scene uou've ever seen personally, as in Aurora Borealis, volcanic eruption, or something that made you seem like the Earth should be treasured?
Far from Westeros, a Three-Eyed Raven Helps NASA Find Its Way
Perched on the outside of the International Space Station is Raven—a technology-filled module that helps NASA develop a relative navigation capability, which is essentially autopilot for spacecraft. Raven has been testing technologies to enable autonomous rendezvous in space, which means the ability to approach things in space without human involvement, even from the ground.
Developed by the Satellite Servicing Projects Division (SSPD), our three-eyed Raven has visible, infrared, and Lidar sensors and uses those “eyes” to image and track visiting spacecraft as they come and go from the space station. Although Raven is all-seeing, it only sees all in black and white. Color images do not offer an advantage in the case of Raven and Restore-L, which also utilize infrared and Lidar sensors.
The data from Raven’s sensors is sent to its processor, which autonomously sends commands that swivel Raven on its gimbal, or pointing system. When Raven turns using this system, it is able to track a vehicle. While these maneuvers take place, NASA operators evaluate the movements and make adjustments to perfect the relative navigation system technologies.
A few days ago, Raven completed its 21st observation of a spacecraft when it captured images of Northrop Grumman’s Cygnus vehicle delivering science investigations and supplies as part of its 11th commercial resupply services mission, including another SSPD payload called the Robotic External Leak Locator.
And just last month, Raven celebrated its two-year anniversary in space, marking the occasion with an observation of SpaceX’s Crew Dragon during the Demo-1 mission.
What is this—a spacecraft for ants??
While this shot of Dragon isn’t terribly impressive because of where the spacecraft docked on station, Raven has captured some truly great images when given the right viewing conditions.
From SpaceX Dragon resupply mission observations…
…to Cygnus supply vehicles.
Raven has observed six unique types of spacecraft.
It has also conducted a few observations not involving spacecraft, including the time it captured Hurricane Irma…
…or the time it captured station’s Dextre arm removing the Robotic Refueling Mission 3 payload, another mission developed by SSPD, from the Dragon spacecraft that delivered it to the orbiting laboratory.
Thus far, Raven has had a great, productive life aboard the station, but its work isn’t done yet! Whether it’s for Restore-L, which will robotically refuel a satellite, or getting humans to the Moon or Mars, the technologies Raven is demonstrating for a relative navigation system will support future NASA missions for decades to come.
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We See Seashores Shifting with Satellites
If you’re like us, as soon as the summer Sun is out, you start feeling – well, just beachy, sand you very much.
Lots of our favorite beaches are inside protected marine areas, which are regulated by governments to keep their ecosystems or cultural heritage intact. If you beachcomb at Cape Cod, swim in the Florida Keys or learn about Hawaiian culture at Papahānaumokuākea Marine National Monument, congrats! You’ve visited a protected marine area.
But time and tide haven’t been kind to some protected beaches.
Beaches are constantly changing, and science teams are using our 30-year record of Earth images from the NASA/USGS Landsat program to study what’s happening.
Overall, the sum total of sandy beaches has increased a bit over the last 30 years. But time and tide haven’t been as kind to our protected beaches – the team found that more than 1/3 of sandy beaches in protected marine areas have been eroding away.
Some of these areas were designated to protect vulnerable plant and animal species or connect delicate ecosystems. They are home to humpback whales and sea turtles, reefs and mangroves that protect the land from erosion and natural disasters, and species which are found in only one habitat in the world. Losing land area could upset the balance of these areas and endanger their future.
Next step: Looking for pearls of wisdom to save the beaches!
Right now, we aren’t sure which beaches are eroding due to natural processes, and which are due to humans – that’s the next step for science teams to investigate. Once we know the causes, we can start working on solutions to save the beaches.
Those 30 years of Landsat data will help scientists find answers to these questions much faster – instead of using airplanes or measuring the beaches by hand, they can use computer programs to rapidly investigate millions of satellite photos spanning many years of change.
By tracking beaches from space, scientists can help keep our summers sandy for years to come.
And that makes us as happy as clams.
Read the full story HERE.
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Don’t Say “Bye, Bye, Bye” To Your Vision: Solar Eclipse Safety Tips
On Oct. 14, 2023, many people across North, Central, and South America will have an opportunity to view a “ring of fire” eclipse – an annular solar eclipse – when the Moon passes between the Earth and Sun! During an annular eclipse, it is never safe to look directly at the Sun without specialized eye protection designed for solar viewing. To spread the word, *NSYNC's Lance Bass stopped by to share some tips on how to stay safe while viewing a solar eclipse.
Check out these detailed viewing maps to see if you will be able to see the entire or partial solar eclipse. If you are, make sure your solar viewing glasses have the ISO certification 12312-2. You can also check with local libraries or science museums to see if they have safe solar viewing glasses to hand out. You can also make a simple pinhole camera at home with some paper and aluminum foil: go.nasa.gov/pinholeprojector
Everyone online can watch the eclipse with NASA. Set a reminder to watch live: https://www.youtube.com/watch?v=LlY79zjud-Q
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From Earth to the Moon: How Are We Getting There?
More than 45 years since humans last set foot on the lunar surface, we’re going back to the Moon and getting ready for Mars. The Artemis program will send the first woman and next man to walk on the surface of the Moon by 2024, establish sustainable lunar exploration and pave the way for future missions deeper into the solar system.
Getting There
Our powerful new rocket, the Space Launch System (SLS), will send astronauts aboard the Orion spacecraft a quarter million miles from Earth to lunar orbit. The spacecraft is designed to support astronauts traveling hundreds of thousands of miles from home, where getting back to Earth takes days rather hours.
Lunar Outpost
Astronauts will dock Orion at our new lunar outpost that will orbit the Moon called the Gateway. This small spaceship will serve as a temporary home and office for astronauts in orbit between missions to the surface of the Moon. It will provide us and our partners access to the entire surface of the Moon, including places we’ve never been before like the lunar South Pole. Even before our first trip to Mars, astronauts will use the Gateway to train for life far away from Earth, and we will use it to practice moving a spaceship in different orbits in deep space.
Expeditions to the Moon
The crew will board a human landing system docked to the Gateway to take expeditions down to the surface of the Moon. We have proposed using a three-stage landing system, with a transfer vehicle to take crew to low-lunar orbit, a descent element to land safely on the surface, and an ascent element to take them back to the Gateway.
Return to Earth
Astronauts will ultimately return to Earth aboard the Orion spacecraft. Orion will enter the Earth’s atmosphere traveling at 25,000 miles per hour, will slow to 300 mph, then parachutes will deploy to slow the spacecraft to approximately 20 mph before splashing down in the Pacific Ocean.
Red Planet
We will establish sustainable lunar exploration within the next decade, and from there, we will prepare for our next giant leap – sending astronauts to Mars!
Discover more about our plans to go to the Moon and on to Mars: https://www.nasa.gov/moontomars
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What advice do you have for Hispanic boys and girls who see themselves in you and are inspired by your achievements?
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