Light - Blog Posts

How Do Space Telescopes Break Down Light?

Space telescopes like Hubble and our upcoming James Webb Space Telescope use light not only to create images, but can also break light down into individual colors (or wavelengths). Studying light this way can give us a lot of detail about the object that emitted that light.  For example, studying the components of the light from exoplanets can tell us about its atmosphere’s color, chemical makeup, and temperature. How does this work?

Remember the primary colors you learned about in elementary school?

Those colors are known as the pigment or subtractive colors. Every other color is some combination of the primary colors: red, yellow, and blue.

Light also has its own primary colors, and they work in a similar way. These colors are known as additive or light colors.          

TVs make use of light’s colors to create the pictures we see. Each pixel of a TV screen contains some amount of red, green and blue light. The amount of each light determines the overall color of the pixel. So, each color on the TV comes from a combination of the primary colors of light: red, green and blue.

Space telescope images of celestial objects are also a combination of the colors of light.

Every pixel that is collected can be broken down into its base colors. To learn even more, astronomers break the red, green and blue light down into even smaller sections called wavelengths.

This breakdown is called a spectrum.

With the right technology, every pixel of light can also be measured as a spectrum.

Images show us the big picture, while a spectrum reveals finer details.  Astronomers use spectra to learn things like what molecules are in planet atmospheres and distant galaxies.

An Integral Field Unit, or IFU, is a special tool on the James Webb Space Telescope that captures images and spectra at the same time.

The IFU creates a unique spectrum for each pixel of the image the telescope is capturing, providing scientists with an enormous amount of valuable, detailed data. So, with an IFU we can get an image, many spectra and a better understanding of our universe.

Watch the full video where this method of learning about planetary atmospheres is explained:

The James Webb Space Telescope is our upcoming infrared space observatory, which will launch in 2021. It will spy the first galaxies that formed in the universe and shed light on how galaxies evolve, how stars and planetary systems are born and tell us about potentially habitable planets around other stars.

To learn more about NASA’s James Webb Space Telescope, visit the website, or follow the mission on Facebook, Twitter and Instagram.

Text and graphics credit: Space Telescope Science Institute

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5 of Your Fermi Gamma-ray Space Telescope Questions Answered

The Fermi Gamma-ray Space Telescope is a satellite in low-Earth orbit that detects gamma rays from exotic objects like black holes, neutron stars and fast-moving jets of hot gas. For 11 years Fermi has seen some of the highest-energy bursts of light in the universe and is helping scientists understand where gamma rays come from.

Confused? Don’t be! We get a ton of questions about Fermi and figured we'd take a moment to answer a few of them here.

1. Who was this Fermi guy?

The Fermi telescope was named after Enrico Fermi in recognition of his work on how the tiny particles in space become accelerated by cosmic objects, which is crucial to understanding many of the objects that his namesake satellite studies.

Enrico Fermi was an Italian physicist and Nobel Prize winner (in 1938) who immigrated to the United States to be a professor of physics at Columbia University, later moving to the University of Chicago.

Original image courtesy Argonne National Laboratory

Over the course of his career, Fermi was involved in many scientific endeavors, including the Manhattan Project, quantum theory and nuclear and particle physics. He even engineered the first-ever atomic reactor in an abandoned squash court (squash is the older, English kind of racquetball) at the University of Chicago.

There are a number of other things named after Fermi, too: Fermilab, the Enrico Fermi Nuclear Generating Station, the Enrico Fermi Institute and more. (He’s kind of a big deal in the physics world.)

Fermi even had something to say about aliens! One day at lunch with his buddies, he wondered if extraterrestrial life existed outside our solar system, and if it did, why haven't we seen it yet? His short conversation with friends sparked decades of research into this idea and has become known as the Fermi Paradox — given the vastness of the universe, there is a high probability that alien civilizations exist out there, so they should have visited us by now.  

2. So, does the Fermi telescope look for extraterrestrial life?

No. Although both are named after Enrico Fermi, the Fermi telescope and the Fermi Paradox have nothing to do with one another.

Fermi does not look for aliens, extraterrestrial life or anything of the sort! If aliens were to come our way, Fermi would be no help in identifying them, and they might just slip right under Fermi’s nose. Unless, of course, those alien spacecraft were powered by processes that left behind traces of gamma rays.

Fermi detects gamma rays, the highest-energy form of light, which are often produced by events so far away the light can take billions of years to reach Earth. The satellite sees pulsars, active galaxies powered by supermassive black holes and the remnants of exploding stars. These are not your everyday stars, but the heavyweights of the universe. 

3. Does the telescope shoot gamma rays?

No. Fermi DETECTS gamma rays using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM).

The LAT sees about one-fifth of the sky at a time and records gamma rays that are millions of times more energetic than visible light. The GBM detects lower-energy emissions, which has helped it identify more than 2,000 gamma-ray bursts – energetic explosions in galaxies extremely far away.

The highest-energy gamma ray from a gamma-ray burst was detected by Fermi’s LAT, and traveled 3.8 billion light-years to reach us from the constellation Leo.

4. Will gamma rays turn me into a superhero?

Nope. In movies and comic books, the hero has a tragic backstory and a brush with death, only to rise out of some radioactive accident stronger and more powerful than before. In reality, that much radiation would be lethal.

In fact, as a form of radiation, gamma rays are dangerous for living cells. If you were hit with a huge amount of gamma radiation, it could be deadly — it certainly wouldn’t be the beginning of your superhero career.

5. That sounds bad…does that mean if a gamma-ray burst hit Earth, it would wipe out the planet and destroy us all?

Thankfully, our lovely planet has an amazing protector from gamma radiation: an atmosphere. That is why the Fermi telescope is in orbit; it’s easier to detect gamma rays in space!

Gamma-ray bursts are so far away that they pose no threat to Earth. Fermi sees gamma-ray bursts because the flash of gamma rays they release briefly outshines their entire home galaxies, and can sometimes outshine everything in the gamma-ray sky.

If a habitable planet were too close to one of these explosions, it is possible that the jet emerging from the explosion could wipe out all life on that planet. However, the probability is extremely low that a gamma-ray burst would happen close enough to Earth to cause harm. These events tend to occur in very distant galaxies, so we’re well out of reach.

We hope that this has helped to clear up a few misconceptions about the Fermi Gamma-ray Space Telescope. It’s a fantastic satellite, studying the craziest extragalactic events and looking for clues to unravel the mysteries of our universe!

Now that you know the basics, you probably want to learn more! Follow the Fermi Gamma-ray Space Telescope on Twitter (@NASAFermi) or Facebook (@nasafermi), and check out more awesome stuff on our Fermi webpage.

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

A Day in Our Lives With X-Ray Tech

On July 23, 1999, NASA’s Chandra X-ray Observatory, the most powerful X-ray telescope ever built, was launched into space. Since then, Chandra has made numerous amazing discoveries, giving us a view of the universe that is largely hidden from view through telescopes that observe in other types of light.

The technology behind X-ray astronomy has evolved at a rapid pace, producing and contributing to many spinoff applications you encounter in day-to-day life. It has helped make advancements in such wide-ranging fields as security monitoring, medicine and bio-medical research, materials processing, semi-conductor and microchip manufacturing and environmental monitoring.

7:00 am: Your hand has been bothering you ever since you caught that ball at the family reunion last weekend. Your doctor decides it would be a good idea for an X-ray to rule out any broken bones. X-rays are sent through your hand and their shadow is captured on a detector behind it. You’re relieved to hear nothing is broken, though your doctor follows up with an MRI to make sure the tendons and ligaments are OK.

Two major developments influenced by X-ray astronomy include the use of sensitive detectors to provide low dose but high-resolution images, and the linkage with digitizing and image processing systems. Because many diagnostic procedures, such as mammographies and osteoporosis scans, require multiple exposures, it is important that each dosage be as low as possible. Accurate diagnoses also depend on the ability to view the patient from many different angles. Image processing systems linked to detectors capable of recording single X-ray photons, like those developed for X-ray astronomy purposes, provide doctors with the required data manipulation and enhancement capabilities. Smaller hand-held imaging systems can be used in clinics and under field conditions to diagnose sports injuries, to conduct outpatient surgery and in the care of premature and newborn babies.

8:00 am: A technician places your hand in a large cylindrical machine that whirs and groans as the MRI is taken. Unlike X-rays that can look at bones and dense structures, MRIs use magnets and short bursts of radio waves to see everything from organs to muscles.

MRI systems are incredibly important for diagnosing a whole host of potential medical problems and conditions. X-ray technology has helped MRIs. For example, one of the instruments developed for use on Chandra was an X-ray spectrometer that would precisely measure the energy signatures over a key range of X-rays. In order to make these observations, this X-ray spectrometer had to be cooled to extremely low temperatures. Researchers at our Goddard Space Flight Center in Greenbelt, Maryland developed an innovative magnet that could achieve these very cold temperatures using a fraction of the helium that other similar magnets needed, thus extending the lifetime of the instrument’s use in space. These advancements have helped make MRIs safer and require less maintenance.

11:00 am:  There’s a pharmacy nearby so you head over to pick up allergy medicine on the way home from your doctor’s appointment.

X-ray diffraction is the technique where X-ray light changes its direction by amounts that depend on the X-ray energy, much like a prism separates light into its component colors. Scientists using Chandra take advantage of diffraction to reveal important information about distant cosmic sources using the observatory’s two gratings instruments, the High Energy Transmission Grating Spectrometer (HETGS) and the Low Energy Transmission Grating Spectrometer (LETGS).

X-ray diffraction is also used in biomedical and pharmaceutical fields to investigate complex molecular structures, including basic research with viruses, proteins, vaccines and drugs, as well as for cancer, AIDS and immunology studies. How does this work? In most applications, the subject molecule is crystallized and then irradiated. The resulting diffraction pattern establishes the composition of the material. X-rays are perfect for this work because of their ability to resolve small objects. Advances in detector sensitivity and focused beam optics have allowed for the development of systems where exposure times have been shortened from hours to seconds. Shorter exposures coupled with lower-intensity radiation have allowed researchers to prepare smaller crystals, avoid damage to samples and speed up their data runs.

12:00 pm: Don’t forget lunch. There’s not much time after your errands so you grab a bag of pretzels. Food safety procedures for packaged goods include the use of X-ray scans to make sure there is quality control while on the production line.

Advanced X-ray detectors with image displays inspect the quality of goods being produced or packaged on a production line. With these systems, the goods do not have to be brought to a special screening area and the production line does not have to be disrupted. The systems range from portable, hand-held models to large automated systems. They are used on such products as aircraft and rocket parts and structures, canned and packaged foods, electronics, semiconductors and microchips, thermal insulations and automobile tires.

2:00 pm: At work, you are busy multi-tasking across a number of projects, running webinar and presentation software, as well as applications for your calendar, spreadsheets, word processing, image editing and email (and perhaps some social media on the side). It’s helpful that your computer can so easily handle running many applications at once.

X-ray beam lithography can produce extremely fine lines and has applications for developing computer chips and other semiconductor related devices. Several companies are researching the use of focused X-ray synchrotron beams as the energy source for this process, since these powerful beams produce good pattern definition with relatively short exposure times. The grazing incidence optics — that is, the need to skip X-rays off a smooth mirror surface like a stone across a pond and then focus them elsewhere — developed for Chandra were the highest precision X-ray optics in the world and directly influenced this work.

7:00 pm: Dream vacation with your family. Finally!  You are on your way to the Bahamas to swim with the dolphins. In the line for airport security, carry-on bags in hand, you are hoping you’ve remembered sunscreen. Shoes off! All items placed in the tray. Thanks to X-ray technology, your bags will be inspected quickly and you WILL catch your plane…

The first X-ray baggage inspection system for airports used detectors nearly identical to those flown in the Apollo program to measure fluorescent X-rays from the Moon. Its design took advantage of the sensitivity of the detectors that enabled the size, power requirements and radiation exposure of the system to be reduced to limits practical for public use, while still providing adequate resolution to effectively screen baggage.  The company that developed the technology later developed a system that can simultaneously image, on two separate screens, materials of high atomic weight (e.g. metal hand guns) and materials of low atomic weight (e.g. plastic explosives) that pass through other systems undetected. Variations of these machines are used to screen visitors to public buildings around the world.

Check out Chandra’s 20th anniversary page to see how they are celebrating.

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A Wrinkle in Space-Time: The Eclipse That “Proved” Einstein Right

One hundred years ago a total solar eclipse turned an obscure scientist into a household name. You might have heard of him — his name is Albert Einstein. But how did a solar eclipse propel him to fame?

First, it would be good to know a couple things about general relativity. (Wait, don’t go! We’ll keep this to the basics!)

A decade before he finished general relativity, Einstein published his special theory of relativity, which demonstrates how space and time are interwoven as a single structure he dubbed “space-time.” General relativity extended the foundation of special relativity to include gravity. Einstein realized that gravitational fields can be understood as bends and curves in space-time that affect the motions of objects including stars, planets — and even light.

For everyday situations the centuries-old description of gravity by Isaac Newton does just fine. However, general relativity must be accounted for when we study places with strong gravity, like black holes or neutron stars, or when we need very precise measurements, like pinpointing a position on Earth to within a few feet. That makes it hard to test!

A prediction of general relativity is that light passing by an object feels a slight "tug", causing the light's path to bend slightly. The more mass the object has, the more the light will be deflected. This sets up one of the tests that Einstein suggested — measuring how starlight bends around the Sun, the strongest source of gravity in our neighborhood. Starlight that passes near the edge of the Sun on its way to Earth is deflected, altering by a small amount where those stars appear to be. How much? By about the width of a dime if you saw it at a mile and a quarter away! But how can you observe faint stars near the brilliant Sun? During a total solar eclipse!

That’s where the May 29, 1919, total solar eclipse comes in. Two teams were dispatched to locations in the path of totality — the places on Earth where the Moon will appear to completely cover the face of the Sun during an eclipse. One team went to South America and another to Africa.

On eclipse day, the sky vexed both teams, with rain in Africa and clouds in South America. The teams had only mere minutes of totality during which to take their photographs, or they would lose the opportunity until the next total solar eclipse in 1921! However, the weather cleared at both sites long enough for the teams to take images of the stars during totality.

The teams took two sets of photographs of the same patch of sky – one set during the eclipse and another set a few months before or after, when the Sun was out of the way. By comparing these two sets of photographs, researchers could see if the apparent star positions changed as predicted by Einstein. This is shown with the effect exaggerated in the image above.

A few months after the eclipse, when the teams sorted out their measurements, the results demonstrated that general relativity correctly predicted the positions of the stars. Newspapers across the globe announced that the controversial theory was proven (even though that’s not quite how science works). It was this success that propelled Einstein into the public eye.

The solar eclipse wasn’t the first test of general relativity. For more than two centuries, astronomers had known that Mercury’s orbit was a little off. Its perihelion — the point during its orbit when it is closest to the Sun — was changing faster than Newton’s laws predicted. General relativity easily explains it, though, because Mercury is so close to the Sun that its orbit is affected by the Sun’s dent in space-time, causing the discrepancy.  

In fact, we still test general relativity today under different conditions and in different situations to see whether or not it holds up. So far, it has passed every test we’ve thrown at it.

Curious to know where we need general relativity to understand objects in space? Tune into our Tumblr tomorrow to find out!

You can also read more about how our understanding of the universe has changed during the past 100 years, from Einstein's formulation of gravity through the discovery of dark energy in our Cosmic Times newspaper series.

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

8 Common Questions About Our James Webb Space Telescope

You might have heard the basics about our James Webb Space Telescope, or Webb, and still have lots more questions! Here are more advanced questions we are frequently asked. (If you want to know the basics, read this Tumblr first!)

Webb is our upcoming infrared space observatory, which will launch in 2021. It will spy the first luminous objects that formed in the universe and shed light on how galaxies evolve, how stars and planetary systems are born, and how life could form on other planets.

1. Why is the mirror segmented? 

The James Webb Space Telescope has a 6.5-meter (21.3-foot) diameter mirror, made from 18 individual segments. Webb needs to have an unfolding mirror because the mirror is so large that it otherwise cannot fit in the launch shroud of currently available rockets.

The mirror has to be large in order to see the faint light from the first star-forming regions and to see very small details at infrared wavelengths. 

Designing, building, and operating a mirror that unfolds is one of the major technological developments of Webb. Unfolding mirrors will be necessary for future missions requiring even larger mirrors, and will find application in other scientific, civil, and military space missions.

2. Why are the mirrors hexagonal?

In short, the hexagonal shape allows a segmented mirror to be constructed with very small gaps, so the segments combine to form a roughly circular shape and need only three variations in prescription. If we had circular segments, there would be gaps between them.

Finally, we want a roughly circular overall mirror shape because that focuses the light into the most symmetric and compact region on the detectors. 

An oval mirror, for example, would give images that are elongated in one direction. A square mirror would send a lot of the light out of the central region.

3. Is there a danger from micrometeoroids?

A micrometeoroid is a particle smaller than a grain of sand. Most never reach Earth's surface because they are vaporized by the intense heat generated by the friction of passing through the atmosphere. In space, no blanket of atmosphere protects a spacecraft or a spacewalker.

Webb will be a million miles away from the Earth orbiting what we call the second Lagrange point (L2). Unlike in low Earth orbit, there is not much space debris out there that could damage the exposed mirror. 

But we do expect Webb to get impacted by these very tiny micrometeoroids for the duration of the mission, and Webb is designed to accommodate for them.

All of Webb's systems are designed to survive micrometeoroid impacts.

4. Why does the sunshield have five layers?

Webb has a giant, tennis-court sized sunshield, made of five, very thin layers of an insulating film called Kapton.  

Why five? One big, thick sunshield would conduct the heat from the bottom to the top more than would a shield with five layers separated by vacuum. With five layers to the sunshield, each successive one is cooler than the one below. 

The heat radiates out from between the layers, and the vacuum between the layers is a very good insulator. From studies done early in the mission development five layers were found to provide sufficient cooling. More layers would provide additional cooling, but would also mean more mass and complexity. We settled on five because it gives us enough cooling with some “margin” or a safety factor, and six or more wouldn’t return any additional benefits.

Fun fact: You could nearly boil water on the hot side of the sunshield, and it is frigid enough on the cold side to freeze nitrogen!

5. What kind of telescope is Webb?

Webb is a reflecting telescope that uses three curved mirrors. Technically, it’s called a three-mirror anastigmat.

6. What happens after launch? How long until there will be data?

We’ll give a short overview here, but check out our full FAQ for a more in-depth look.

In the first hour: About 30 minutes after liftoff, Webb will separate from the Ariane 5 launch vehicle. Shortly after this, we will talk with Webb from the ground to make sure everything is okay after its trip to space.

In the first day: After 24 hours, Webb will be nearly halfway to the Moon! About 2.5 days after launch, it will pass the Moon’s orbit, nearly a quarter of the way to Lagrange Point 1 (L2).

In the first week: We begin the major deployment of Webb. This includes unfolding the sunshield and tensioning the individual membranes, deploying the secondary mirror, and deploying the primary mirror.

In the first month: Deployment of the secondary mirror and the primary mirror occur. As the telescope cools in the shade of the sunshield, we turn on the warm electronics and initialize the flight software. As the telescope cools to near its operating temperature, parts of it are warmed with electronic heaters. This prevents condensation as residual water trapped within some of the materials making up the observatory escapes into space.

In the second month: We will turn on and operate Webb’s Fine Guidance Sensor, NIRCam, and NIRSpec instruments. 

The first NIRCam image, which will be an out-of-focus image of a single bright star, will be used to identify each mirror segment with its image of a star in the camera. We will also focus the secondary mirror.

In the third month: We will align the primary mirror segments so that they can work together as a single optical surface. We will also turn on and operate Webb’s mid-infrared instrument (MIRI), a camera and spectrograph that views a wide spectrum of infrared light. By this time, Webb will complete its journey to its L2 orbit position.

In the fourth through the sixth month: We will complete the optimization of the telescope. We will test and calibrate all of the science instruments.

After six months: The first scientific images will be released, and Webb will begin its science mission and start to conduct routine science operations.

7. Why not assemble it in orbit?

Various scenarios were studied, and assembling in orbit was determined to be unfeasible.

We examined the possibility of in-orbit assembly for Webb. The International Space Station does not have the capability to assemble precision optical structures. Additionally, space debris that resides around the space station could have damaged or contaminated Webb’s optics. Webb’s deployment happens far above low Earth orbit and the debris that is found there.

Finally, if the space station were used as a stopping point for the observatory, we would have needed a second rocket to launch it to its final destination at L2. The observatory would have to be designed with much more mass to withstand this “second launch,” leaving less mass for the mirrors and science instruments.

8. Who is James Webb?

This telescope is named after James E. Webb (1906–1992), our second administrator. Webb is best known for leading Apollo, a series of lunar exploration programs that landed the first humans on the Moon. 

However, he also initiated a vigorous space science program that was responsible for more than 75 launches during his tenure, including America's first interplanetary explorers.

Looking for some more in-depth FAQs? You can find them HERE.

Learn more about the James Webb Space Telescope HERE, or follow the mission on Facebook, Twitter and Instagram.

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

10 Frequently Asked Questions About the James Webb Space Telescope

Got basic questions about the James Webb Space Telescope and what amazing things we’ll learn from it? We’ve got your answers right here! 

The James Webb Space Telescope, or Webb, is our upcoming infrared space observatory, which will launch in 2021. It will spy the first luminous objects that formed in the universe and shed light on how galaxies evolve, how stars and planetary systems are born, and how life could form on other planets.

1. What is the James Webb Space Telescope?

Our James Webb Space Telescope is a giant space telescope that observes infrared light. Rather than a replacement for the Hubble Space Telescope, it’s a scientific successor that will complement and extend its discoveries.

Being able to see longer wavelengths of light than Hubble and having greatly improved sensitivity will let Webb look further back in time to see the first galaxies that formed in the early universe, and to peer inside dust clouds where stars and planetary systems are forming today.

2. What are the most exciting things we will learn?

We have yet to observe the era of our universe’s history when galaxies began to form. 

We have a lot to learn about how galaxies got supermassive black holes in their centers, and we don't really know whether the black holes caused the galaxies to form or vice versa.

We can't see inside dust clouds with high resolution, where stars and planets are being born nearby, but Webb will be able to do just that. 

We don't know how many planetary systems might be hospitable to life, but Webb could tell whether some Earth-like planets have enough water to have oceans.

We don't know much about dark matter or dark energy, but we expect to learn more about where the dark matter is now, and we hope to learn the history of the acceleration of the universe that we attribute to dark energy. 

And then, there are the surprises we can't imagine!

3. Why is Webb an infrared telescope?

By viewing the universe at infrared wavelengths with such sensitivity, Webb will show us things never before seen by any other telescope. For example, it is only at infrared wavelengths that we can see the first stars and galaxies forming after the Big Bang. 

And it is with infrared light that we can see stars and planetary systems forming inside clouds of dust that are opaque to visible light, such as in the above visible and infrared light comparison image of the Carina Nebula.

4. Will Webb take amazing pictures like Hubble? Can Webb see visible light?

YES, Webb will take amazing pictures! We are going to be looking at things we've never seen before and looking at things we have seen before in completely new ways.

The beauty and quality of an astronomical image depends on two things: the sharpness and the number of pixels in the camera. On both of these counts, Webb is very similar to, and in many ways better than, Hubble. 

Additionally Webb can see orange and red visible light. Webb images will be different, but just as beautiful as Hubble's. Above, there is another comparison of infrared and visible light Hubble images, this time of the Monkey Head Nebula.

5. What will Webb's first targets be?

The first targets for Webb will be determined through a process similar to that used for the Hubble Space Telescope and will involve our experts, the European Space Agency (ESA), the Canadian Space Agency (CSA), and scientific community participants.

The first engineering target will come before the first science target and will be used to align the mirror segments and focus the telescope. That will probably be a relatively bright star or possibly a star field.

6. How does Webb compare with Hubble?

Webb is designed to look deeper into space to see the earliest stars and galaxies that formed in the universe and to look deep into nearby dust clouds to study the formation of stars and planets.

In order to do this, Webb has a much larger primary mirror than Hubble (2.5 times larger in diameter, or about 6 times larger in area), giving it more light-gathering power. It also will have infrared instruments with longer wavelength coverage and greatly improved sensitivity than Hubble. 

Finally, Webb will operate much farther from Earth, maintaining its extremely cold operating temperature, stable pointing and higher observing efficiency than with the Earth-orbiting Hubble.

7. What will Webb tell us about planets outside our solar system? Will it take photos of these planets?

Webb will be able to tell us the composition of the atmospheres of planets outside our solar system, aka exoplanets. It will observe planetary atmospheres through the transit technique. A transit is when a planet moves across the disc of its parent star. 

Webb will also carry coronographs to enable photography of exoplanets (planets outside our solar system) near bright stars (if they are big and bright and far from the star), but they will be only "dots," not grand panoramas. Coronographs block the bright light of stars, which could hide nearby objects like exoplanets.

Consider how far away exoplanets are from us, and how small they are by comparison to this distance! We didn’t even know what Pluto really looked like until we were able to send an observatory to fly right near it in 2015, and Pluto is in our own solar system!

8. Will we image objects in our own solar system?

Yes! Webb will be able to observe the planets at or beyond the orbit of Mars, satellites, comets, asteroids and objects in the distant, icy Kuiper Belt.

Many important molecules, ices and minerals have strong characteristic signatures at the wavelengths Webb can observe. 

Webb will also monitor the weather of planets and their moons. 

Because the telescope and instruments have to be kept cold, Webb’s protective sunshield will block the inner solar system from view. This means that the Sun, Earth, Moon, Mercury, and Venus, and of course Sun-grazing comets and many known near-Earth objects cannot be observed.

9. How far back will Webb see? 

Webb will be able to see what the universe looked like around a quarter of a billion years (possibly back to 100 million years) after the Big Bang, when the first stars and galaxies started to form.

10. When will Webb launch and how long is the mission?

Webb will launch in 2021 from French Guiana on a European Space Agency Ariane 5 rocket. 

Webb’s mission lifetime after launch is designed to be at least 5-1/2 years, and could last longer than 10 years. The lifetime is limited by the amount of fuel used for maintaining the orbit, and by the possibility that Webb’s components will degrade over time in the harsh environment of space.

Looking for some more in-depth FAQs? You can find them HERE.

Learn more about the James Webb Space Telescope HERE, or follow the mission on Facebook, Twitter and Instagram.

IMAGE CREDITS Carina Nebula: ESO/T. Preibisch Monkey Head Nebula: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and J. Hester

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Pick Your Favorite Findings From Fermi’s First Decade

The Fermi Gamma-ray Space Telescope has been observing some of the most extreme objects and events in the universe — from supermassive black holes to merging neutron stars and thunderstorms — for 10 years. Fermi studies the cosmos using gamma rays, the highest-energy form of light, and has discovered thousands of new phenomena for scientists.

Here are a few of our favorite Fermi discoveries, pick your favorite in the first round of our “Fermi Science Playoff.” 

Colliding Neutron Stars

In 2017, Fermi detected a gamma ray burst at nearly the same moment ground observatories detected gravitational waves from two merging neutron stars. This was the first time light and ripples in space-time were detected from the same source.

The Sun and Moon in Gamma Rays

In 2016, Fermi showed the Moon is brighter in gamma rays than the Sun. Because the Moon doesn’t have a magnetic field, the surface is constantly pelted from all directions by cosmic rays. These produce gamma rays when they run into other particles, causing a full-Moon gamma-ray glow.

Record Rare from a Blazar

The supermassive black hole at the center of the galaxy 3C 279 weighs a billion times the mass of our Sun. In June 2015, this blazar became the brightest gamma-ray source in the sky due to a record-setting flare.

The First Gamma-Ray Pulsar in Another Galaxy

In 2015, for the first time, Fermi discovered a gamma-ray pulsar, a kind of rapidly spinning superdense star, in a galaxy outside our own. The object, located on the outskirts of the Tarantula Nebula, also set the record for the most luminous gamma-ray pulsar we’ve seen so far.

A Gamma-Ray Cycle in Another Galaxy

Many galaxies, including our own, have black holes at their centers. In active galaxies, dust and gas fall into and “feed” the black hole, releasing light and heat. In 2015 for the first time, scientists using Fermi data found hints that a galaxy called PG 1553+113 has a years-long gamma-ray emission cycle. They’re not sure what causes this cycle, but one exciting possibility is that the galaxy has a second supermassive black hole that causes periodic changes in what the first is eating.

Gamma Rays from Novae

A nova is a fairly common, short-lived kind of explosion on the surface of a white dwarf, a type of compact star not much larger than Earth. In 2014, Fermi observed several novae and found that they almost always produce gamma-rays, giving scientists a new type of source to explore further with the telescope.

A Record-Setting Cosmic Blast

Gamma-ray bursts are the most luminous explosions in the universe. In 2013, Fermi spotted the brightest burst it’s seen so far in the constellation Leo. In the first three seconds alone, the burst, called GRB 130427A, was brighter than any other burst seen before it. This record has yet to be shattered.

Cosmic Rays from Supernova Leftovers

Cosmic rays are particles that travel across the cosmos at nearly the speed of light. They are hard to track back to their source because they veer off course every time they encounter a magnetic field. In 2013, Fermi showed that these particles reach their incredible speed in the shockwaves of supernova remains — a theory proposed in 1949 by the satellite’s namesake, the Italian-American physicist Enrico Fermi.

Discovery of a Transformer Pulsar

In 2013, the pulsar in a binary star system called AY Sextanis switched from radio emissions to high-energy gamma rays. Scientists think the change reflects erratic interaction between the two stars in the binary.

Gamma-Ray Measurement of a Gravitational Lens

A gravitational lens is a kind of natural cosmic telescope that occurs when a massive object in space bends and amplifies light from another, more distant object. In 2012, Fermi used gamma rays to observe a spiral galaxy 4.03 billion light-years away bending light coming from a source 4.35 billion light-years away.

New Limits on Dark Matter

We can directly observe only 20 percent of the matter in the universe. The rest is invisible to telescopes and is called dark matter — and we’re not quite sure what it is. In 2012, Fermi helped place new limits on the properties of dark matter, essentially narrowing the field of possible particles that can describe what dark matter is.

‘Superflares’ in the Crab Nebula

The Crab Nebula supernova remnant is one of the most-studied targets in the sky — we’ve been looking at it for almost a thousand years! In 2011, Fermi saw it erupt in a flare five times more powerful than any previously seen from the object. Scientists calculate the electrons in this eruption are 100 times more energetic than what we can achieve with particle accelerators on Earth.

Thunderstorms Hurling Antimatter into Space

Terrestrial gamma-ray flashes are created by thunderstorms. In 2011, Fermi scientists announced the satellite had detected beams of antimatter above thunderstorms, which they think are a byproduct of gamma-ray flashes.

Giant Gamma-Ray Bubbles in the Milky Way

Using data from Fermi in 2010, scientists discovered a pair of “bubbles” emerging from above and below the Milky Way. These enormous bubbles are half the length of the Milky Way and were probably created by our galaxy’s supermassive black hole only a few million years ago.

Hint of Starquakes in a Magnetar

Neutron stars have magnetic fields trillions of times stronger than Earth’s. Magnetars are neutron stars with magnetic fields 1,000 times stronger still. In 2009, Fermi saw a storm of gamma-ray bursts from a magnetar called SGR J1550-5418, which scientists think were related to seismic waves rippling across its surface.

A Dark Pulsar

We observe many pulsars using radio waves, visible light or X-rays. In 2008, Fermi found the first gamma-ray only pulsar in a supernova remnant called CTA 1. We think that the “beam” of gamma rays we see from CTA 1 is much wider than the beam of other types of light from that pulsar. Those other beams never sweep across our vision — only the gamma-rays.

Have a favorite Fermi discovery or want to learn more? Cast your vote in the first of four rounds of the Fermi Science Playoff to help rank Fermi’s findings. Or follow along as we celebrate the mission all year.

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The Universe's Brightest Lights Have Some Dark Origins

Did you know some of the brightest sources of light in the sky come from black holes in the centers of galaxies? It sounds a little contradictory, but it's true! They may not look bright to our eyes, but satellites have spotted oodles of them across the universe. 

One of those satellites is our Fermi Gamma-ray Space Telescope. Fermi has found thousands of these kinds of galaxies in the 10 years it's been operating, and there are many more out there!

Black holes are regions of space that have so much gravity that nothing - not light, not particles, nada - can escape. Most galaxies have supermassive black holes at their centers - these are black holes that are hundreds of thousands to billions of times the mass of our sun - but active galactic nuclei (also called "AGN" for short, or just "active galaxies") are surrounded by gas and dust that's constantly falling into the black hole. As the gas and dust fall, they start to spin and form a disk. Because of the friction and other forces at work, the spinning disk starts to heat up.

The disk's heat gets emitted as light - but not just wavelengths of it that we can see with our eyes. We see light from AGN across the entire electromagnetic spectrum, from the more familiar radio and optical waves through to the more exotic X-rays and gamma rays, which we need special telescopes to spot.

About one in 10 AGN beam out jets of energetic particles, which are traveling almost as fast as light. Scientists are studying these jets to try to understand how black holes - which pull everything in with their huge amounts of gravity - somehow provide the energy needed to propel the particles in these jets.

Many of the ways we tell one type of AGN from another depend on how they're oriented from our point of view. With radio galaxies, for example, we see the jets from the side as they're beaming vast amounts of energy into space. Then there's blazars, which are a type of AGN that have a jet that is pointed almost directly at Earth, which makes the AGN particularly bright.  

Our Fermi Gamma-ray Space Telescope has been searching the sky for gamma ray sources for 10 years. More than half (57%) of the sources it has found have been blazars. Gamma rays are useful because they can tell us a lot about how particles accelerate and how they interact with their environment.

So why do we care about AGN? We know that some AGN formed early in the history of the universe. With their enormous power, they almost certainly affected how the universe changed over time. By discovering how AGN work, we can understand better how the universe came to be the way it is now.

Fermi's helped us learn a lot about the gamma-ray universe over the last 10 years. Learn more about Fermi and how we're celebrating its accomplishments all year.

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Infrared is Beautiful

Why was James Webb Space Telescope designed to observe infrared light? How can its images hope to compare to those taken by the (primarily) visible-light Hubble Space Telescope? The short answer is that Webb will absolutely capture beautiful images of the universe, even if it won’t see exactly what Hubble sees. (Spoiler: It will see a lot of things even better.)

The James Webb Space Telescope, or Webb, is our upcoming infrared space observatory, which will launch in 2019. It will spy the first luminous objects that formed in the universe and shed light on how galaxies evolve, how stars and planetary systems are born, and how life could form on other planets.

What is infrared light? 

This may surprise you, but your remote control uses light waves just beyond the visible spectrum of light—infrared light waves—to change channels on your TV.

Infrared light shows us how hot things are. It can also show us how cold things are. But it all has to do with heat. Since the primary source of infrared radiation is heat or thermal radiation, any object that has a temperature radiates in the infrared. Even objects that we think of as being very cold, such as an ice cube, emit infrared.

There are legitimate scientific reasons for Webb to be an infrared telescope. There are things we want to know more about, and we need an infrared telescope to learn about them. Things like: stars and planets being born inside clouds of dust and gas; the very first stars and galaxies, which are so far away the light they emit has been stretched into the infrared; and the chemical fingerprints of elements and molecules in the atmospheres of exoplanets, some of which are only seen in the infrared.

In a star-forming region of space called the 'Pillars of Creation,' this is what we see with visible light:

And this is what we see with infrared light:

Infrared light can pierce through obscuring dust and gas and unveil a more unfamiliar view.

Webb will see some visible light: red and orange. But the truth is that even though Webb sees mostly infrared light, it will still take beautiful images. The beauty and quality of an astronomical image depends on two things: the sharpness of the image and the number of pixels in the camera. On both of these counts, Webb is very similar to, and in many ways better than, Hubble. Webb will take much sharper images than Hubble at infrared wavelengths, and Hubble has comparable resolution at the visible wavelengths that Webb can see.

Webb’s infrared data can be translated by computer into something our eyes can appreciate – in fact, this is what we do with Hubble data. The gorgeous images we see from Hubble don’t pop out of the telescope looking fully formed. To maximize the resolution of the images, Hubble takes multiple exposures through different color filters on its cameras.

The separate exposures, which look black and white, are assembled into a true color picture via image processing. Full color is important to image analysis of celestial objects. It can be used to highlight the glow of various elements in a nebula, or different stellar populations in a galaxy. It can also highlight interesting features of the object that might be overlooked in a black and white exposure, and so the images not only look beautiful but also contain a lot of useful scientific information about the structure, temperatures, and chemical makeup of a celestial object.

This image shows the sequences in the production of a Hubble image of nebula Messier 17:

Here’s another compelling argument for having telescopes that view the universe outside the spectrum of visible light – not everything in the universe emits visible light. There are many phenomena which can only be seen at certain wavelengths of light, for example, in the X-ray part of the spectrum, or in the ultraviolet. When we combine images taken at different wavelengths of light, we can get a better understanding of an object, because each wavelength can show us a different feature or facet of it. 

Just like infrared data can be made into something meaningful to human eyes, so can each of the other wavelengths of light, even X-rays and gamma-rays.

Below is an image of the M82 galaxy created using X-ray data from the Chandra X-ray Observatory, infrared data from the Spitzer Space Telescope, and visible light data from Hubble. Also note how aesthetically pleasing the image is despite it not being just optical light:

Though Hubble sees primarily visible light, it can see some infrared. And despite not being optimized for it, and being much less powerful than Webb, it still produced this stunning image of the Horsehead Nebula.

It’s a big universe out there – more than our eyes can see. But with all the telescopes now at our disposal (as well as the new ones that will be coming online in the future), we are slowly building a more accurate picture. And it’s definitely a beautiful one. Just take a look...

…At this Spitzer infrared image of a shock wave in dust around the star Zeta Ophiuchi.

…this Spitzer image of the Helix Nebula, created using infrared data from the telescope and ultraviolet data from the Galaxy Evolution Explorer.

…this image of the “wing” of the Small Magellanic Cloud, created with infrared data from Spitzer and X-ray data from Chandra.

...the below image of the Milky Way’s galactic center, taken with our flying SOFIA telescope. It flies at more than 40,000 feet, putting it above 99% of the  water vapor in Earth's atmosphere-- critical for observing infrared because water vapor blocks infrared light from reaching the ground. This infrared view reveals the ring of gas and dust around a supermassive black hole that can't be seen with visible light. 

…and this Hubble image of the Mystic Mountains in the Carina Nebula.

Learn more about the James Webb Space Telescope HERE, or follow the mission on Facebook, Twitter and Instagram.

Image Credits Eagle Nebula: NASA, ESA/Hubble and the Hubble Heritage Team Hubble Image Processing - Messier 17: NASA/STScI Galaxy M82 Composite Image: NASA, CXC, JHU, D.Strickland, JPL-Caltech, C. Engelbracht (University of Arizona), ESA, and The Hubble Heritage Team (STScI/AURA) Horsehead Nebula: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) Zeta Ophiuchi: NASA/JPL-Caltech Helix Nebula: NASA/JPL-Caltech Wing of the Small Magellanic Cloud X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech Milky Way Circumnuclear Ring: NASA/DLR/USRA/DSI/FORCAST Team/ Lau et al. 2013 Mystic Mountains in the Carina Nebula: NASA/ESA/M. Livio & Hubble 20th Anniversary Team (STScI)

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Meet Fermi: Our Eyes on the Gamma-Ray Sky

Black holes, cosmic rays, neutron stars and even new kinds of physics — for 10 years, data from our Fermi Gamma-ray Space Telescope have helped unravel some of the biggest mysteries of the cosmos. And Fermi is far from finished!

On June 11, 2008, at Cape Canaveral in Florida, the countdown started for Fermi, which was called the Gamma-ray Large Area Space Telescope (GLAST) at the time. 

The telescope was renamed after launch to honor Enrico Fermi, an Italian-American pioneer in high-energy physics who also helped develop the first nuclear reactor. 

Fermi has had many other things named after him, like Fermi’s Paradox, the Fermi National Accelerator Laboratory, the Enrico Fermi Nuclear Generating Station, the Enrico Fermi Institute, and the synthetic element fermium.

Photo courtesy of Argonne National Laboratory

The Fermi telescope measures some of the highest energy bursts of light in the universe; watching the sky to help scientists answer all sorts of questions about some of the most powerful objects in the universe. 

Its main instrument is the Large Area Telescope (LAT), which can view 20% of the sky at a time and makes a new image of the whole gamma-ray sky every three hours. Fermi’s other instrument is the Gamma-ray Burst Monitor. It sees even more of the sky at lower energies and is designed to detect brief flashes of gamma-rays from the cosmos and Earth.

This sky map below is from 2013 and shows all of the high energy gamma rays observed by the LAT during Fermi’s first five years in space.  The bright glowing band along the map’s center is our own Milky Way galaxy!

So what are gamma rays? 

Well, they’re a form of light. But light with so much energy and with such short wavelengths that we can’t see them with the naked eye. Gamma rays require a ton of energy to produce — from things like subatomic particles (such as protons) smashing into each other. 

Here on Earth, you can get them in nuclear reactors and lightning strikes. Here’s a glimpse of the Seattle skyline if you could pop on a pair of gamma-ray goggles. That purple streak? That’s still the Milky Way, which is consistently the brightest source of gamma rays in our sky.

In space, you find that kind of energy in places like black holes and neutron stars. The raindrop-looking animation below shows a big flare of gamma rays that Fermi spotted coming from something called a blazar, which is a kind of quasar, which is different from a pulsar... actually, let’s back this up a little bit.

One of the sources of gamma rays that Fermi spots are pulsars. Pulsars are a kind of neutron star, which is a kind of star that used to be a lot bigger, but collapsed into something that’s smaller and a lot denser. Pulsars send out beams of gamma rays. But the thing about pulsars is that they rotate. 

So Fermi only sees a beam of gamma rays from a pulsar when it’s pointed towards Earth. Kind of like how you only periodically see the beam from a lighthouse. These flashes of light are very regular. You could almost set your watch by them!

Quasars are supermassive black holes surrounded by disks of gas. As the gas falls into the black hole, it releases massive amount of energy, including — you guessed it — gamma rays. Blazars are quasars that send out beams of gamma rays and other forms of light — right in our direction. 

When Fermi sees them, it’s basically looking straight down this tunnel of light, almost all the way back to the black hole. This means we can learn about the kinds of conditions in that environment when the rays were emitted. Fermi has found about 5,500 individual sources of gamma rays, and the bulk of them have been blazars, which is pretty nifty.

But gamma rays also have many other sources. We’ve seen them coming from supernovas where stars die and from star factories where stars are born. They’re created in lightning storms here on Earth, and our own Sun can toss them out in solar flares. 

Gamma rays were in the news last year because of something Fermi spotted at almost the same time as the National Science Foundation (NSF)’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and European Gravitational Observatory’s Virgo on August 17, 2017. Fermi, LIGO, Virgo, and numerous other observatories spotted the merger of two neutron stars. It was the first time that gravitational waves and light were confirmed to come from the same source.

Fermi has been looking at the sky for almost 10 years now, and it’s helped scientists advance our understanding of the universe in many ways. And the longer it looks, the more we’ll learn. Discover more about how we’ll be celebrating Fermi’s achievements all year.

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Black Hole Sculpts an Hourglass Galaxy

When it comes to galaxies, our home, the Milky Way, is rather neat and orderly. Other galaxies can be much more chaotic. For example, the Markarian 573 galaxy has a black hole at its center which is spewing beams of light in opposite directions, giving its inner regions more of an hourglass shape. 

Our scientists have long been fascinated by this unusual structure, seen above in optical light from the Hubble Space Telescope. Now their search has taken them deeper than ever — all the way into the super-sized black hole at the center of one galaxy.

So, what do we think is going on? When the black hole gobbles up matter, it releases a form of high-energy light called radiation (particularly in the form of X-rays), causing abnormal patterns in the flow of gas. 

Let’s take a closer look.

Meet Markarian 573, the galaxy at the center of this image from the Sloan Digital Sky Survey, located about 240 million light-years away from Earth in the constellation Cetus. It’s the galaxy’s odd structure and the unusual motions of its components that inspire our scientists to study it.

As is the case with other so-called active galaxies, the ginormous black hole at the center of Markarian 573 likes to eat stuff. A thick ring of dust and gas accumulates around it, forming a doughnut. This ring only permits light to escape the black hole in two cone-shaped regions within the flat plane of the galaxy — and that’s what creates the hourglass, as shown in the illustration above.

Zooming out, we can see the two cones of emission (shown in gold in the animation above) spill into the galaxy's spiral arms (blue). As the galaxy rotates, gas clouds in the arms sweep through this radiation, which makes them light up so our scientists can track their movements from Earth.

What happens next depends on how close the gas is to the black hole. Gas that’s about 2,500 light-years from the black hole picks up speed and streams outward (shown as darker red and blue arrows). Gas that’s farther from the black hole also becomes ionized, but is not driven away and continues its motion around the galaxy as before.

Here is an actual snapshot of the inner region of Markarian 573, combining X-ray data (blue) from our Chandra X-ray Observatory and radio observations (purple) from the Karl G. Jansky Very Large Array in New Mexico with a visible light image (gold) from our Hubble Space Telescope. Given its strange appearance, we’re left to wonder: what other funky shapes might far-off galaxies take?

For more information about the bizarre structure of Markarian 573, visit http://svs.gsfc.nasa.gov/12657  

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What caused this outburst of this star named V838 Mon? For reasons unknown, this star’s outer surface suddenly greatly expanded with the result that it became the brightest star in the entire Milky Way Galaxy in January 2002. Then, just as suddenly, it faded. A stellar flash like this had never been seen before – supernovas and novas expel matter out into space.

Although the V838 Mon flash appears to expel material into space, what is seen in the above GIF from the Hubble Space Telescope is actually an outwardly moving light echo of the bright flash.

In a light echo, light from the flash is reflected by successively more distant rings in the complex array of ambient interstellar dust that already surrounded the star. V838 Mon lies about 20,000 light years away toward the constellation of the unicorn (Monoceros), while the light echo above spans about six light years in diameter.

Credit: NASA, ESA

To discover more, visit: https://www.nasa.gov/multimedia/imagegallery/image_feature_2472.html

Crab Nebula in technicolor! This new composite view combines data from five different telescopes, showing the celestial object in multiple kinds of light.

The video starts with a composite image of the Crab Nebula, a supernova remnant that was assembled by combining data from five telescopes spanning nearly the entire breadth of the electromagnetic spectrum: the Very Large Array, the Spitzer Space Telescope, the Hubble Space Telescope, the XMM-Newton Observatory, and the Chandra X-ray Observatory. 

It then dissolves to the red-colored radio-light view that shows how a neutron star’s fierce “wind” of charged particles from the central neutron star energized the nebula, causing it to emit the radio waves. 

The yellow-colored infrared image includes the glow of dust particles absorbing ultraviolet and visible light. 

The green-colored Hubble visible-light image offers a very sharp view of hot filamentary structures that permeate this nebula. 

The blue-colored ultraviolet image and the purple-colored X-ray image shows the effect of an energetic cloud of electrons driven by a rapidly rotating neutron star at the center of the nebula.

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