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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 European Space Agency
This new snapshot from the European Space Agency’s Mars Express deftly captures the two distinct faces of Mars: ridged and rugged versus smooth and unmarked.
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
A Martian dust devil can be seen consuming its smaller friend in this short video made of images taken at the rim of Jezero Crater by NASA’s Perseverance Mars rover on Jan. 25, 2025. NASA/JPL-Caltech/SSI The six-wheeled explorer recently captured several Red Planet mini-twisters spinning on the rim of Jezero Crater.
A Martian dust devil can be seen consuming a smaller one in this short video made of images taken by a navigation camera aboard NASA’s Perseverance Mars rover. These swirling, sometimes towering columns of air and dust are common on Mars. The smaller dust devil’s demise was captured during an imaging experiment conducted by Perseverance’s science team to better understand the forces at play in the Martian atmosphere.
When the rover snapped these images from about 0.6 miles (1 kilometer) away, the larger dust devil was approximately 210 feet (65 meters) wide, while the smaller, trailing dust devil was roughly 16 feet (5 meters) wide. Two other dust devils can also be seen in the background at left and center. Perseverance recorded the scene Jan. 25 as it explored the western rim of Mars’ Jezero Crater at a location called “Witch Hazel Hill.”
“Convective vortices — aka dust devils — can be rather fiendish,” said Mark Lemmon, a Perseverance scientist at the Space Science Institute in Boulder, Colorado. “These mini-twisters wander the surface of Mars, picking up dust as they go and lowering the visibility in their immediate area. If two dust devils happen upon each other, they can either obliterate one another or merge, with the stronger one consuming the weaker.”
While exploring the rim of Jezero Crater on Mars, NASA’s Perseverance rover captured new images of multiple dust devils in January 2025. These captivating phenomena have been documented for decades by the agency’s Red Planet robotic explorers. NASA/JPL-Caltech/LANL/CNES/CNRS/INTA-CSIC/Space Science Institute/ISAE-Supaero/University of Arizona Science of Whirlwinds
Dust devils are formed by rising and rotating columns of warm air. Air near the planet’s surface becomes heated by contact with the warmer ground and rises through the denser, cooler air above. As other air moves along the surface to take the place of the rising warmer air, it begins to rotate. When the incoming air rises into the column, it picks up speed like a spinning ice skater bringing their arms closer to their body. The air rushing in also picks up dust, and a dust devil is born.
“Dust devils play a significant role in Martian weather patterns,” said Katie Stack Morgan, project scientist for the Perseverance rover at NASA’s Jet Propulsion Laboratory in Southern California. “Dust devil study is important because these phenomena indicate atmospheric conditions, such as prevailing wind directions and speed, and are responsible for about half the dust in the Martian atmosphere.”
NASA’s Viking 1 orbiter captured this Martian dust devil casting a shadow on Aug. 1, 1978. During the 15-second interval between the two images, the dust devil moved toward the northeast (toward the upper right) at a rate of about 59 feet (18 meters) per second. NASA/JPL-Caltech/MSSS Since landing in 2021, Perseverance has imaged whirlwinds on many occasions, including one on Sept. 27, 2021, where a swarm of dust devils danced across the floor of Jezero Crater and the rover used its SuperCam microphone to record the first sounds of a Martian dust devil.
NASA’s Viking orbiters, in the 1970s, were the first spacecraft to photograph Martian dust devils. Two decades later, the agency’s Pathfinder mission was the first to image one from the surface and even detected a dust devil passing over the lander. Twin rovers Spirit and Opportunity managed to capture their fair share of dusty whirlwinds. Curiosity, which is exploring a location called Mount Sharp in Gale Crater on the opposite side of the Red Planet as Perseverance, sees them as well.
Capturing a dust devil image or video with a spacecraft takes some luck. Scientists can’t predict when they’ll appear, so Perseverance routinely monitors in all directions for them. When scientists see them occur more frequently at a specific time of day or approach from a certain direction, they use that information to focus their monitoring to try to catch additional whirlwinds.
“If you feel bad for the little devil in our latest video, it may give you some solace to know the larger perpetrator most likely met its own end a few minutes later,” said Lemmon. “Dust devils on Mars only last about 10 minutes.”
More About Perseverance
A key objective of Perseverance’s mission on Mars is astrobiology, including caching samples that may contain signs of ancient microbial life. The rover is characterizing the planet’s geology and past climate, to help pave the way for human exploration of the Red Planet and as the first mission to collect and cache Martian rock and regolith.
NASA’s Mars Sample Return Program, in cooperation with ESA (European Space Agency), is designed to send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.
The Mars 2020 Perseverance mission is part of NASA’s Mars Exploration Program (MEP) portfolio and the agency’s Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.
NASA’s Jet Propulsion Laboratory, which is managed for the agency by Caltech, built and manages operations of the Perseverance rover.
For more about Perseverance:
https://science.nasa.gov/mission/mars-2020-perseverance
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DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011
agle@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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Last Updated Apr 03, 2025 Related Terms
Perseverance (Rover) Curiosity (Rover) Jet Propulsion Laboratory Mars Mars 2020 Mars Exploration Rovers (MER) Mars Pathfinder Viking Explore More
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By European Space Agency
Video: 00:15:30 Meet Arnaud Prost—aerospace engineer, professional diver, and member of ESA’s Astronaut Reserve. From flying aircraft to getting a taste of spacewalk simulation, his passion for exploration knows no bounds.
In this miniseries, we take you on a journey through the ESA Astronaut Reserve, diving into the first part of their Astronaut Reserve Training (ART) at the European Astronaut Centre (EAC) near Cologne, Germany. Our “ARTists” are immersing themselves in everything from ESA and the International Space Station programme to the European space industry and institutions. They’re gaining hands-on experience in technical skills like spacecraft systems and robotics, alongside human behaviour, scientific lessons, scuba diving, and survival training.
ESA’s Astronaut Reserve Training programme is all about building Europe’s next generation of space explorers—preparing them for the opportunities of future missions in Earth orbit and beyond.
This interview was recorded in November 2024.
You can listen to this episode on all major podcast platforms.
Keep exploring with ESA Explores!
Learn more about Arnaud’s PANGAEA training here.
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
A NASA F/A-18 research aircraft flies above California near NASA’s Armstrong Flight Research Center in Edwards, California, testing a commercial precision landing technology for future space missions. The Psionic Space Navigation Doppler Lidar (PSNDL) system is installed in a pod located under the right wing of the aircraft.NASA Nestled in a pod under an F/A-18 Hornet aircraft wing, flying above California, and traveling up to the speed of sound, NASA put a commercial sensor technology to the test. The flight tests demonstrated the sensor accuracy and navigation precision in challenging conditions, helping prepare the technology to land robots and astronauts on the Moon and Mars.
The Psionic Space Navigation Doppler Lidar (PSNDL) system is rooted in NASA technology that Psionic, Inc. of Hampton, Virginia, licensed and further developed. They miniaturized the NASA technology, added further functionality, and incorporated component redundancies that make it more rugged for spaceflight. The PSNDL navigation system also includes cameras and an inertial measurement unit to make it a complete navigation system capable of accurately determining a vehicle’s position and velocity for precision landing and other spaceflight applications.
NASA engineers and technicians install the Psionic Space Navigation Doppler Lidar (PSNDL) system into a testing pod on a NASA F/A-18 research aircraft ahead of February 2025 flight tests at NASA’s Armstrong Flight Research Center in Edwards, California.NASA The aircraft departed from NASA’s Armstrong Flight Research Center in Edwards, California, and conducted a variety of flight paths over several days in February 2025. It flew a large figure-8 loop and conducted several highly dynamic maneuvers over Death Valley, California, to collect navigation data at various altitudes, velocities, and orientations relevant for lunar and Mars entry and descent. Refurbished for these tests, the NASA F/A-18 pod can support critical data collection for other technologies and users at a low cost.
Doppler Lidar sensors provide a highly accurate measurement of speed by measuring the frequency shift between laser light emitted from the sensor reflected from the ground. Lidar are extremely useful in sunlight-challenged areas that may have long shadows and stark contrasts, such as the lunar South Pole. Pairing PSNDL with cameras adds the ability to visually compare pictures with surface reconnaissance maps of rocky terrain and navigate to landing at interesting locations on Mars. All the data is fed into a computer to make quick, real-time decisions to enable precise touchdowns at safe locations.
Psionic Space Navigation Doppler Lidar (PSNDL) system installed in a testing pod on a NASA F/A-18 research aircraft ahead of February 2025 flight tests at NASA’s Armstrong Flight Research Center in Edwards, California.NASA Since licensing NDL in 2016, Psionic has received funding and development support from NASA’s Space Technology Mission Directorate through its Small Business Innovative Research program and Tipping Point initiative. The company has also tested PSNDL prototypes on suborbital vehicles via the Flight Opportunities program. In 2024, onboard a commercial lunar lander, NASA successfully demonstrated the predecessor NDL system developed by the agency’s Langley Research Center in Hampton, Virginia.
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Last Updated Mar 26, 2025 EditorLoura Hall Related Terms
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