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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
The European Space Agency (ESA) has selected Airbus to design and build the landing platform for the ExoMars Rosalind Franklin rover. In 2028, ESA will launch this ambitious exploration mission to search for past and present signs of life on Mars.
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By NASA
Earth (ESD) Earth Explore Explore Earth Science Climate Change Air Quality Science in Action Multimedia Image Collections Videos Data For Researchers About Us 8 Min Read NASA Researchers Study Coastal Wetlands, Champions of Carbon Capture
Florida’s coastal wetlands are a complex patchwork of ecosystem — consisting of sawgrass marshland, hardwood hammocks, freshwater swamps, and mangrove forests. Credits:
NASA/ Nathan Marder Across the street from the Flamingo Visitor’s Center at the foot of Florida’s Everglades National Park, there was once a thriving mangrove population — part of the largest stand of mangroves in the Western Hemisphere. Now, the skeletal remains of the trees form one of the Everglades’ largest ghost forests.
When Hurricane Irma made landfall in September 2017 as a category 4 storm, violent winds battered the shore and a storm surge swept across the coast, decimating large swaths of mangrove forest. Seven years later, most of the mangroves here haven’t seen any new growth. “At this point, I doubt they’ll recover,” said David Lagomasino, a professor of coastal studies at East Carolina University.
Lagomasino was in the Everglades conducting fieldwork as part of NASA’s BlueFlux Campaign, a three-year project that aims to study how sub-tropical wetlands influence atmospheric levels of carbon dioxide (CO2) and methane. Both gases absorb solar radiation and have a warming effect on Earth’s atmosphere.
A mangrove “ghost forest” near Florida’s southernmost coast houses the remains of a once-thriving mangrove stand. NASA/Nathan Marder The campaign is led by Ben Poulter, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who studies the way human activity and climate change affect the carbon cycle. As wetland vegetation responds to increasing temperatures, rising sea levels, and severe weather, Poulter’s team is trying to determine how much carbon dioxide wetland vegetation removes from the atmosphere and how much methane it produces. Ultimately this research will help scientists develop models to estimate and monitor greenhouse gas concentrations in coastal areas around the globe.
Although coastal wetlands account for less than 2% of the planet’s land-surface area, they remove a significant amount of carbon dioxide from the atmosphere. Florida’s coastal wetlands alone remove an estimated 31.8 million metric tons each year. A commercial aircraft would have to circle the globe more than 26,000 times to produce the same amount of carbon dioxide. Coastal wetlands also store carbon in marine sediments, keeping it underground — and out of the atmosphere — for thousands of years. This carbon storage capacity of oceans and wetlands is so robust that it has its own name: blue carbon.
“We’re worried about losing that stored carbon,” Poulter said. “But blue carbon also offers tremendous opportunities for climate mitigation if conservation and restoration are properly supported by science.”
The one-meter core samples collected by Lagomasino will be used to identify historic rates of blue carbon development in mangrove forests and to evaluate how rates of carbon storage respond to specific environmental pressures, like sea level rise or the increasing frequency of tropical cyclones.
Early findings from space-based flux data confirm that, in addition to acting as a sink of carbon dioxide, tropical wetlands are a significant source of methane — a greenhouse gas that traps heat roughly 80 times more efficiently than carbon dioxide. In fact, researchers estimate that Florida’s entire wetland expanse produces enough methane to offset the benefits of wetland carbon removal by about 5%.
Everglades peat contains history of captured carbon
During his most recent fieldwork deployment, Lagomasino used a small skiff to taxi from one research site to the next; many parts of the Everglades are virtually unreachable on foot. At each site, he opened a broad, black case and removed a metallic peat auger, which resembles a giant letter opener. The instrument is designed to extract core samples from soft soils. Everglades peat — which is composed almost entirely of the carbon-rich, partially decomposed roots, stems, and leaves of mangroves — offers a perfect study subject.
Lagomasino plunged the auger into the soil, using his body weight to push the instrument into the ground. Once the sample was secured, he freed the tool from the Earth, presenting a half-cylinder of soil. Each sample was sealed and shipped back to the lab — where they are sliced horizontally into flat discs and analyzed for their age and carbon content.
East Carolina University professor of coastal studies David Lagomasino (right) and his doctoral student Daystar Babanawo explore the Everglades by boat. The plant life here consists almost entirely of mangroves, which can withstand the saltwater tides that characterize coastal wetlands. Scientific studies of Florida’s coastal ecosystems have historically been limited by the relative inaccessibility of the region. NASA/Nathan Marder Everglades peat forms quickly. In Florida’s mangrove forests, around 2 to 10 millimeters of soil are added to the forest floor each year, building up over time like sand filling an hourglass. Much like an ice core, sediment cores offer a window into Earth’s past. The deeper the core, the further into the past one can see. By looking closely at the contents of the soil, researchers can uncover information about the climate conditions from the time the soil formed.
In some parts of the Everglades, soil deposits can reach depths of up to 3 meters (10 feet), where one meter might represent close to 100 years of peat accumulation, Lagomasino said. Deep in the Amazon rainforest, by comparison, a similarly sized, one-meter deposit could take more than 1,000 years to develop. This is important in the context of restoration efforts: in coastal wetlands, peat losses can be restored up to 10 times faster than they might be in other forest types.
Lagomasino holds a sample of peat soil collected from the forest floor. The source of the soil’s elevated carbon content — evident from its coarse, fibrous texture — is primarily the thread-like root hairs routinely recycled by the surrounding mangroves. The presence of water slows the decomposition of this organic material, which is why wetlands can lock carbon away and prevent it from escaping into the atmosphere for thousands of years. NASA/Nathan Marder “There are also significant differences in fluxes between healthy mangroves and degraded ones,” said Lola Fatoyinbo, a research scientist in the Biospheric Sciences Laboratory at NASA’s Goddard Space Flight Center. In areas where mangrove forests are suffering, for example, after a major hurricane, “you end up with more greenhouse gases in the atmosphere,” she said. As wetland ecology responds to intensifying natural and human pressures, the data product will help researchers precisely monitor the impact of ecological changes on global carbon dioxide and methane levels.
Wetland methane: A naturally occurring but potent greenhouse gas
Methane is naturally produced by microbes that live in wetland soils. But as wetland conditions change, the growth rate of methane-producing microbes can spike, releasing the gas into the atmosphere at prodigious rates.
Since methane is a significantly more potent greenhouse gas than carbon dioxide, possessing a warming potential 84 times greater over a 25-year period, methane emissions undermine some of the beneficial services that blue carbon ecosystems provide as natural sinks for atmospheric carbon dioxide.
While Lagomasino studied the soil to understand long-term storage of greenhouse gases, Lola Fatoyinbo, a research scientist in NASA’s Biospheric Sciences Lab, and Peter Raymond, an ecologist at Yale University’s School of the Environment, measured the rate at which these gases are exchanged between wetland vegetation and the atmosphere. This metric is known as gaseous flux.
Lagomasino holds a sample of peat soil collected from the forest floor. The presence of water slows the decomposition of this organic material, which is why wetlands can lock carbon away and prevent it from escaping into the atmosphere for thousands of years. NASA/Nathan Marder NASA/Nathan Marder The scientists measure flux using chambers designed to adhere neatly to points where significant rates of gas exchange occur. They secure box-like chambers to above-ground roots and branches while domed chambers measure gas escaping from the forest floor. The concentration of gases trapped in each chamber is measured over time.
In general, as the health of wetland ecology declines, less carbon dioxide is removed, and more methane is released. But the exact nature of the relationship between wetland health and gaseous flux is not well understood. What does flux look like in ghost forests, for example? And how do more subtle changes in variables like canopy coverage or species distribution influence levels of carbon dioxide sequestration or methane production?
“We’re especially interested in the methane part,” Fatoyinbo said. “It’s the least understood, and there’s a lot more of it than we previously thought.”
Based on data collected during BlueFlux fieldwork, “we’re finding that coastal wetlands remove massive amounts of carbon dioxide and produce substantial amounts of methane,” Poulter said. “But overall, these ecosystems appear to provide a net climate benefit, removing more greenhouse gases than they produce.” That could change as Florida’s wetlands respond to continued climate disturbances.
The future of South Florida’s ecology
Florida’s wetlands are roughly 5,000 years old. But in just the past century, more than half of the state’s original wetland coverage has been lost as vegetation was cleared and water was drained to accommodate the growing population. The Everglades system now contains 65% less peat and 77% less stored carbon than it did prior to drainage. The future of the ecosystem — which is not only an important reservoir for atmospheric carbon, but a source of drinking water for more than 7 million Floridians and a home to flora and fauna found nowhere else on Earth — is uncertain.
Scientists who have dedicated their careers to understanding and restoring South Florida’s ecology are hopeful. “Nature and people can coexist,” said Meenakshi Chabba, an ecologist and resilience scientist at the Everglades Foundation in Florida’s Miami-Dade County. “But we need good science and good management to reach that goal.”
The next step for NASA’s BlueFlux campaign is the development of a satellite-based data product that can help regional stakeholders evaluate in real-time how Florida’s wetlands are responding to restoration efforts designed to protect one of the state’s most precious natural resources — and all those who depend on it.
By Nathan Marder
NASA’s Goddard Space Flight Center, Greenbelt, Maryland
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By NASA
3 Min Read March’s Night Sky Notes: Messier Madness
Showing a large portion of M66, this Hubble photo is a composite of images obtained at visible and infrared wavelengths. The images have been combined to represent the real colors of the galaxy. Credits:
NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: Davide De Martin and Robert Gendler by Kat Troche of the Astronomical Society of the Pacific
What Are Messier Objects?
During the 18th century, astronomer and comet hunter Charles Messier wanted to distinguish the ‘faint fuzzies’ he observed from any potential new comets. As a result, Messier cataloged 110 objects in the night sky, ranging from star clusters to galaxies to nebulae. These items are designated by the letter ‘M’ and a number. For example, the Orion Nebula is Messier 42 or M42, and the Pleiades are Messier 45 or M45. These are among the brightest ‘faint fuzzies’ we can see with modest backyard telescopes and some even with our eyes.
Stargazers can catalog these items on evenings closest to the new moon. Some even go as far as having “Messier Marathons,” setting up their telescopes and binoculars in the darkest skies available to them, from sundown to sunrise, to catch as many as possible. Here are some items to look for this season:
M44 in Cancer and M65 and 66 in Leo can be seen high in the evening sky 60 minutes after sunset. Stellarium Web Messier 44 in Cancer: The Beehive Cluster, also known as Praesepe, is an open star cluster in the heart of the Cancer constellation. Use Pollux in Gemini and Regulus in Leo as guide stars. A pair of binoculars is enough to view this and other open star clusters. If you have a telescope handy, pay a visit two of the three galaxies that form the Leo Triplet – M65 and M66. These items can be seen one hour after sunset in dark skies.
Locate M3 and M87 rising in the east after midnight. Stellarium Web Messier 3 Canes Venatici: M3 is a globular cluster of 500,000 stars. Through a telescope, this object looks like a fuzzy sparkly ball. You can resolve this cluster in an 8-inch telescope in moderate dark skies. You can find this star cluster by using the star Arcturus in the Boötes constellation as a guide.
Messier 87 in Virgo: Located just outside of Markarian’s Chain, M87 is an elliptical galaxy that can be spotted during the late evening hours. While it is not possible to view the supermassive black hole at the core of this galaxy, you can see M87 and several other Messier-labeled galaxies in the Virgo Cluster using a medium-sized telescope.
Locate M76 and M31 setting in the west, 60 minutes after sunset. Stellarium Web Plan Ahead
When gearing up for a long stargazing session, there are several things to remember, such as equipment, location, and provisions:
Do you have enough layers to be outdoors for several hours? You would be surprised how cold it can get when sitting or standing still behind a telescope! Are your batteries fully charged? If your telescope runs on power, be sure to charge everything before you leave home and pack any additional batteries for your cell phone. Most people use their mobile devices for astronomy apps, so their batteries may deplete faster. Cold weather can also impact battery life. Determine the apparent magnitude of what you are trying to see and the limiting magnitude of your night sky. You can learn more about apparent and limiting magnitudes with our Check Your Sky Quality with Orion article. When choosing a location to observe from, select an area you are familiar with and bring some friends! You can also connect with your local astronomy club to see if they are hosting any Messier Marathons. It’s always great to share the stars! You can see all 110 items and their locations with NASA’s Explore the Night Sky interactive map and the Hubble Messier Catalog, objects that have been imaged by the Hubble Space Telescope.
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