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By NASA
4 min read
May’s Night Sky Notes: How Do We Find Exoplanets?
Astronomers have been trying to discover evidence that worlds exist around stars other than our Sun since the 19th century. By the mid-1990s, technology finally caught up with the desire for discovery and led to the first discovery of a planet orbiting another sun-like star, Pegasi 51b. Why did it take so long to discover these distant worlds, and what techniques do astronomers use to find them?
The Transit Method
A planet passing in front of its parent star creates a drop in the star’s apparent brightness, called a transit. Exoplanet Watch participants can look for transits in data from ground-based telescopes, helping scientists refine measurements of the length of a planet’s orbit around its star. Credit: NASA’s Ames Research Center One of the most famous exoplanet detection methods is the transit method, used by Kepler and other observatories. When a planet crosses in front of its host star, the light from the star dips slightly in brightness. Scientists can confirm a planet orbits its host star by repeatedly detecting these incredibly tiny dips in brightness using sensitive instruments. If you can imagine trying to detect the dip in light from a massive searchlight when an ant crosses in front of it, at a distance of tens of miles away, you can begin to see how difficult it can be to spot a planet from light-years away! Another drawback to the transit method is that the distant solar system must be at a favorable angle to our point of view here on Earth – if the distant system’s angle is just slightly askew, there will be no transits. Even in our solar system, a transit is very rare. For example, there were two transits of Venus visible across our Sun from Earth in this century. But the next time Venus transits the Sun as seen from Earth will be in the year 2117 – more than a century from the 2012 transit, even though Venus will have completed nearly 150 orbits around the Sun by then!
The Wobble Method
As a planet orbits a star, the star wobbles. This causes a change in the appearance of the star’s spectrum called Doppler shift. Because the change in wavelength is directly related to relative speed, astronomers can use Doppler shift to calculate exactly how fast an object is moving toward or away from us. Astronomers can also track the Doppler shift of a star over time to estimate the mass of the planet orbiting it. NASA, ESA, CSA, Leah Hustak (STScI) Spotting the Doppler shift of a star’s spectra was used to find Pegasi 51b, the first planet detected around a Sun-like star. This technique is called the radial velocity or “wobble” method. Astronomers split up the visible light emitted by a star into a rainbow. These spectra, and gaps between the normally smooth bands of light, help determine the elements that make up the star. However, if there is a planet orbiting the star, it causes the star to wobble ever so slightly back and forth. This will, in turn, cause the lines within the spectra to shift ever so slightly towards the blue and red ends of the spectrum as the star wobbles slightly away and towards us. This is caused by the blue and red shifts of the star’s light. By carefully measuring the amount of shift in the star’s spectra, astronomers can determine the size of the object pulling on the host star and if the companion is indeed a planet. By tracking the variation in this periodic shift of the spectra, they can also determine the time it takes the planet to orbit its parent star.
Direct Imaging
Finally, exoplanets can be revealed by directly imaging them, such as this image of four planets found orbiting the star HR 8799! Space telescopes use instruments called coronagraphs to block the bright light from the host star and capture the dim light from planets. The Hubble Space Telescope has captured images of giant planets orbiting a few nearby systems, and the James Webb Space Telescope has only improved on these observations by uncovering more details, such as the colors and spectra of exoplanet atmospheres, temperatures, detecting potential exomoons, and even scanning atmospheres for potential biosignatures!
NASA’s James Webb Space Telescope has provided the clearest look in the infrared yet at the iconic multi-planet system HR 8799. The closest planet to the star, HR 8799 e, orbits 1.5 billion miles from its star, which in our solar system would be located between the orbit of Saturn and Neptune. The furthest, HR 8799 b, orbits around 6.3 billion miles from the star, more than twice Neptune’s orbital distance. Colors are applied to filters from Webb’s NIRCam (Near-Infrared Camera), revealing their intrinsic differences. A star symbol marks the location of the host star HR 8799, whose light has been blocked by the coronagraph. In this image, the color blue is assigned to 4.1 micron light, green to 4.3 micron light, and red to the 4.6 micron light. NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI) You can find more information and activities on NASA’s Exoplanets page, such as the Eyes on Exoplanets browser-based program, The Exoplaneteers, and some of the latest exoplanet news. Lastly, you can find more resources in our News & Resources section, including a clever demo on how astronomers use the wobble method to detect planets!
The future of exoplanet discovery is only just beginning, promising rich rewards in humanity’s understanding of our place in the Universe, where we are from, and if there is life elsewhere in our cosmos.
Originally posted by Dave Prosper: July 2015
Last Updated by Kat Troche: April 2025
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By NASA
Did you know some of the brightest sources of light in the sky come from the regions around 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 NASA’s Fermi Gamma-ray Space Telescope. Fermi has found thousands of these kinds of galaxies since it launched in 2008, and there are many more out there!
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Watch a cosmic gamma-ray fireworks show in this animation using just a year of data from the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope. Each object’s magenta circle grows as it brightens and shrinks as it dims. The yellow circle represents the Sun following its apparent annual path across the sky. The animation shows a subset of the LAT gamma-ray records available for more than 1,500 objects in a continually updated repository. Over 90% of these sources are a type of galaxy called a blazar, powered by the activity of a supermassive black hole. NASA’s Marshall Space Flight Center/Daniel Kocevski 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, and these black holes are hundreds of thousands to billions of times the mass of our Sun. In active galactic nuclei (also called “AGN” for short, or just “active galaxies”) the central region is stuffed with gas and dust that’s constantly falling toward 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.
This composite view of the active galaxy Markarian 573 combines X-ray data (blue) from NASA’s 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 the Hubble Space Telescope. Markarian 573 is an active galaxy that has two cones of emission streaming away from the supermassive black hole at its center. X-ray: NASA/CXC/SAO/A.Paggi et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA The disk’s heat gets emitted as light, but not just wavelengths of it that we can see with our eyes. We detect 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.
In the heart of an active galaxy, matter falling toward a supermassive black hole creates jets of particles traveling near the speed of light as shown in this artist’s concept. NASA/Goddard Space Flight Center Conceptual Image Lab 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.
This artist’s concept shows two views of the active galaxy TXS 0128+554, located around 500 million light-years away. Left: The galaxy’s central jets appear as they would if we viewed them both at the same angle. The black hole, embedded in a disk of dust and gas, launches a pair of particle jets traveling at nearly the speed of light. Scientists think gamma rays (magenta) detected by NASA’s Fermi Gamma-ray Space Telescope originate from the base of these jets. As the jets collide with material surrounding the galaxy, they form identical lobes seen at radio wavelengths (orange). The jets experienced two distinct bouts of activity, which created the gap between the lobes and the black hole. Right: The galaxy appears in its actual orientation, with its jets tipped out of our line of sight by about 50 degrees. NASA’s Goddard Space Flight Center 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.
Blazar 3C 279’s historic gamma-ray flare in 2015 can be seen in this image from the Large Area Telescope on NASA’s Fermi satellite. During the flare, the blazar outshone the Vela pulsar, usually the brightest object in the gamma-ray sky. NASA/DOE/Fermi LAT Collaboration Fermi has been searching the sky for gamma ray sources since 2008. More than half 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.
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Last Updated Apr 30, 2025 Related Terms
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By NASA
Nick Kopp is a Dragon flight lead in the Transportation Integration Office at Johnson Space Center in Houston. He is currently leading NASA’s efforts to prepare, launch, and return the agency’s 32nd SpaceX commercial resupply services mission. He works directly with SpaceX and collaborates with NASA’s many internal, external, and international partners to ensure the success of this and other cargo missions to the International Space Station.
Read on to learn about his career with NASA and more!
Nick Kopp’s official portrait.NASA/Bill Stafford The time and effort spent building, maintaining, and conducting science on the International Space Station is spent by people in our community and communities around the world to further humanity's collective understanding of the universe around us.
Nick Kopp
Transportation Integration Office Flight Lead
Where are you from?
I am from Cleveland, Ohio.
Tell us about your role at NASA.
I work directly with SpaceX to ensure the Dragon cargo spacecraft meets NASA’s requirements to visit the space station. I also collaborate with NASA’s various partners who are safely flying science investigations and other cargo to and from the space station. For the upcoming flight, I’ve worked extensively with SpaceX to prepare to return the Dragon cargo spacecraft off the coast of California.
How would you describe your job to family or friends who may not be familiar with NASA?
I’m responsible for getting stuff to and from the International Space Station safely.
How long have you been working for NASA?
I have been working for NASA for about 15 years at both Marshall Space Flight Center in Alabama and Johnson Space Center in Texas.
What advice would you give to young individuals aspiring to work in the space industry or at NASA?
It takes so many different people with all kinds of different skills working together to make missions happen. I would suggest looking at NASA’s websites to find the skill or task that makes you want to learn more and then focusing your energy into that skill. Surround yourself with people with similar goals. Connect with people in the industry and ask them questions. You are in control of your destiny!
Nick Kopp in front of the International Space Station Payload Operations Center at the agency’s Marshall Space Flight Center in Huntsville, Alabama. What was your path to NASA?
I’ve wanted to work at NASA since I was a kid and my grandfather showed me the Moon through his home-built telescope. I studied aerospace engineering at the University of Illinois, where I joined Students for the Exploration and Development of Space and attended a conference at NASA’s Goddard Space Flight Center in Maryland. I met some folks from the Payload Operations Integration Center and learned of the awesome space station science operations at Marshall. I was lucky enough to be chosen for a contractor job working directly with astronauts on the space station to conduct science experiments!
Is there someone in the space, aerospace, or science industry that has motivated or inspired you to work for the space program? Or someone you discovered while working for NASA who inspires you?
After working with him from the ground when he was aboard the space station, I was lucky enough to spend many overnight shifts getting to know NASA astronaut and Flight Director TJ Creamer. TJ’s path to NASA and his servant leadership have left an ongoing legacy for people at the agency. His general attitude, extreme competence, friendly demeanor, and genuine care for people around him continue to inspire me every day to become a great leader.
What is your favorite NASA memory?
My favorite NASA memory is being selected as a payload operations director on the International Space Station Payload Operations and Integration Center flight control team. I looked up to those in this position for 10 years and did everything I could to gather the skills and knowledge I needed to take on the role. I became responsible for the minute-to-minute operations of astronauts conducting science investigations on the space station. I vividly remember the joy I felt learning of the news of my assignment, taking my first shift, my first conversation with an astronaut in space, and the bittersweet decision to leave and continue my career goals at NASA in a different role.
Nick Kopp, right, behind a console in the International Space Station Payload Operations Integration Center at the agency’s Marshall Space Flight Center. What do you love sharing about station? What’s important to get across to general audiences to help them understand the benefits to life on Earth?
Although it takes place off the planet, research on the space station is conducted for people on Earth. The time and effort spent building, maintaining, and conducting science on the International Space Station is spent by people in our community and communities around the world to further humanity’s collective understanding of the universe around us. When we understand more about science, we can be more successful. So many people around the planet have had life-changing benefits from experiments that can only be done by people conducting research in microgravity, above the atmosphere, where you can view most of Earth.
If you could have dinner with any astronaut, past or present, who would it be?
I would have dinner with anyone from the Apollo 13 crew. I’d love to learn how they felt that NASA’s culture drove the outcome of that mission.
Do you have a favorite space-related memory or moment that stands out to you?
While working a night shift at the operations center in Huntsville, Alabama, we were monitoring payloads returning to Earth on a Dragon cargo spacecraft. We took a quick break outside the control center to watch as the spacecraft re-entered Earth’s atmosphere above us on its way to splash down off the coast of Florida. It was a clear night. As the spacecraft flew overhead, we saw the ablative heat shield create a shimmering trail of fire and sparkles that stretched across the whole night sky. It looked as though Tinker Bell just flew over us!
What are some of the key projects you’ve worked on during your time at NASA? What have been your favorite?
Some of my favorite projects I’ve worked on include:
Serving as the International Space Station Program’s representative as flight lead for NASA’s SpaceX Crew-8 mission Troubleshooting unexpected results when conducting science on the space station Writing instructions for astronauts filming a virtual reality documentary on the space station Assessing design changes on the Space Launch System rocket’s core stage Managing and training a team of flight controllers Helping NASA move Dragon spacecraft returns from Florida to California Nick Kopp enjoys sailing on his days off. What are your hobbies/things you enjoy outside of work?
I love playing board games with my wife, sailing, flying, traveling around the world, and learning about leadership and project management theory.
Day launch or night launch?
The Crew-8 night launch, specifically, where the Falcon 9 booster landed just above me!
Favorite space movie?
Spaceballs
NASA “worm” or “meatball” logo?
Meatball
Every day, we’re conducting exciting research aboard our orbiting laboratory that will help us explore further into space and bring benefits back to people on Earth. You can keep up with the latest news, videos, and pictures about space station science on the Station Research & Technology news page. It’s a curated hub of space station research digital media from Johnson and other centers and space agencies.
Sign up for our weekly email newsletter to get the updates delivered directly to you.
Follow updates on social media at @ISS_Research on Twitter, and on the space station accounts on Facebook and Instagram.
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
How can I see the northern lights?
To see the northern lights, you need to be in the right place at the right time.
Auroras are the result of charged particles and magnetism from the Sun called space weather dancing with the Earth’s magnetic field. And they happen far above the clouds. So you need clear skies, good space weather at your latitude and the higher, more polar you can be, the better. You need a lot of patience and some luck is always helpful.
A smartphone can also really help confirm whether you saw a little bit of kind of dim aurora, because cameras are more sensitive than our eyes.
The best months to see aurorae, statistically, are March and September. The best times to be looking are around midnight, but sometimes when the Sun is super active, it can happen any time from sunset to sunrise.
You can also increase your chances by learning more about space weather data and a great place to do that is at the NOAA Space Weather Prediction Center.
You can also check out my project, Aurorasaurus.org, where we have free alerts that are based on your location and we offer information about how to interpret the data. And you can also report and tell us if you were able to see aurora or not and that helps others.
One last tip is finding a safe, dark sky viewing location with a great view of the northern horizon that’s near you.
[END VIDEO TRANSCRIPT]
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Last Updated Mar 26, 2025 Related Terms
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