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Astronomers Measure Mass of Largest Dwarf Planet
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By NASA
2 min read
NASA-Funded Study Examines Tidal Effects on Planet and Moon Interiors
NASA-supported scientists have developed a new method to compute how tides affect the interiors of planets and moons. Importantly, the new study looks at the effects of body tides on objects that don’t have a perfectly spherical interior structure, which is an assumption of most previous models.
The puzzling, fascinating surface of Jupiter’s icy moon Europa looms large in this newly-reprocessed color view, made from images taken by NASA’s Galileo spacecraft in the late 1990s. This is the color view of Europa from Galileo that shows the largest portion of the moon’s surface at the highest resolution. NASA/JPL-Caltech/SETI Institute Body tides refer to the deformations experienced by celestial bodies when they gravitationally interact with other objects. Think of how the powerful gravity of Jupiter tugs on its moon Europa. Because Europa’s orbit isn’t circular, the crushing squeeze of Jupiter’s gravity on the moon varies as it travels along its orbit. When Europa is at its closest to Jupiter, the planet’s gravity is felt the most. The energy of this deformation is what heats up Europa’s interior, allowing an ocean of liquid water to exist beneath the moon’s icy surface.
“The same is true for Saturn’s moon Enceladus.” says co-author Alexander Berne of CalTech in Pasadena and an affiliate at NASA’s Jet Propulsion Laboratory in Southern California. “Enceladus has an ice shell that is expected to be much more non-spherically symmetric than that of Europa.”
The body tides experienced by celestial bodies can affect how the worlds evolve over time and, in cases like Europa and Enceladus, their potential habitability for life as we know it. The new study provides a means to more accurately estimate how tidal forces affect planetary interiors.
In this movie Europa is seen in a cutaway view through two cycles of its 3.5 day orbit about the giant planet Jupiter. Like Earth, Europa is thought to have an iron core, a rocky mantle and a surface ocean of salty water. Unlike on Earth, however, this ocean is deep enough to cover the whole moon, and being far from the sun, the ocean surface is globally frozen over. Europa’s orbit is eccentric, which means as it travels around Jupiter, large tides, raised by Jupiter, rise and fall. Jupiter’s position relative to Europa is also seen to librate, or wobble, with the same period. This tidal kneading causes frictional heating within Europa, much in the same way a paper clip bent back and forth can get hot to the touch, as illustrated by the red glow in the interior of Europa’s rocky mantle and in the lower, warmer part of its ice shell. This tidal heating is what keeps Europa’s ocean liquid and could prove critical to the survival of simple organisms within the ocean, if they exist. The giant planet Jupiter is now shown to be rotating from west to east, though more slowly than its actual rate. NASA/JPL-Caltech The paper also discusses how the results of the study could help scientists interpret observations made by missions to a variety of different worlds, ranging from Mercury to the Moon to the outer planets of our solar system.
The study, “A Spectral Method to Compute the Tides of Laterally Heterogeneous Bodies,” was published in The Planetary Science Journal.
For more information on NASA’s Astrobiology Program, visit:
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Karen Fox / Molly Wasser
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By European Space Agency
Proba-3 is such an ambitious mission that it needs more than one single spacecraft to succeed. In order for Proba-3’s Coronagraph spacecraft observe the Sun’s faint surrounding atmosphere, the disk-bearing Occulter spacecraft must block out the fiery solar disk. This means Proba-3’s Occulter ends up facing the Sun continuously, making it a valuable platform for science in its own right.
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
A SWOT data visualization shows water on the northern side of Greenland’s Dickson Fjord at higher levels than on the southern side on Sept. 17, 2023. A huge rockslide into the fjord the previous day led to a tsunami lasting nine days that caused seismic rumbling around the world. NASA Earth Observatory Data from space shows water tilting up toward the north side of the Dickson Fjord as it sloshed from south to north and back every 90 seconds for nine days after a 2023 rockslide.
The international Surface Water and Ocean Topography (SWOT) satellite mission, a collaboration between NASA and France’s CNES (Centre National d’Études Spatiales), detected the unique contours of a tsunami that sloshed within the steep walls of a fjord in Greenland in September 2023. Triggered by a massive rockslide, the tsunami generated a seismic rumble that reverberated around the world for nine days. An international research team that included seismologists, geophysicists, and oceanographers recently reported on the event after a year of analyzing data.
The SWOT satellite collected water elevation measurements in Dickson Fjord on Sept. 17, 2023, the day after the initial rockslide and tsunami. The data was compared with measurements made under normal conditions a few weeks prior, on Aug. 6, 2023.
In the data visualization (above), colors toward the red end of the scale indicate higher water levels, and blue colors indicate lower-than-normal levels. The data suggests that water levels at some points along the north side of the fjord were as much as 4 feet (1.2 meters) higher than on the south.
“SWOT happened to fly over at a time when the water had piled up pretty high against the north wall of the fjord,” said Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California. “Seeing the shape of the wave — that’s something we could never do before SWOT.”
In a paper published recently in Science, researchers traced a seismic signal back to a tsunami that began when more than 880 million cubic feet of rock and ice (25 million cubic meters) fell into Dickson Fjord. Part of a network of channels on Greenland’s eastern coast, the fjord is about 1,772 feet (540 meters) deep and 1.7 miles (2.7 kilometers) wide, with walls taller than 6,000 feet (1,830 meters).
Far from the open ocean, in a confined space, the energy of the tsunami’s motion had limited opportunity to dissipate, so the wave moved back and forth about every 90 seconds for nine days. It caused tremors recorded on seismic instruments thousands of miles away.
From about 560 miles (900 kilometers) above, SWOT uses its sophisticated Ka-band Radar Interferometer (KaRIn) instrument to measure the height of nearly all water on Earth’s surface, including the ocean and freshwater lakes, reservoirs, and rivers.
“This observation also shows SWOT’s ability to monitor hazards, potentially helping in disaster preparedness and risk reduction,” said SWOT program scientist Nadya Vinogradova Shiffer at NASA Headquarters in Washington.
It can also see into fjords, as it turns out.
“The KaRIn radar’s resolution was fine enough to make observations between the relatively narrow walls of the fjord,” said Lee-Lueng Fu, the SWOT project scientist. “The footprint of the conventional altimeters used to measure ocean height is too large to resolve such a small body of water.”
More About SWOT
Launched in December 2022 from Vandenberg Space Force Base in California, SWOT is now in its operations phase, collecting data that will be used for research and other purposes.
The SWOT satellite was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. NASA’s Jet Propulsion Laboratory, managed for the agency by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA provided the KaRIn instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. CNES provided the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, the dual frequency Poseidon altimeter (developed by Thales Alenia Space), the KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground operations. CSA provided the KaRIn high-power transmitter assembly. NASA provided the launch vehicle and the agency’s Launch Services Program, based at Kennedy Space Center in Florida, managed the associated launch services.
To learn more about SWOT, visit:
https://swot.jpl.nasa.gov
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Jane J. Lee / Andrew Wang
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Last Updated Oct 31, 2024 Related Terms
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
This artist’s concept depicts a potential volcanic moon between the exoplanet WASP-49 b, left, and its parent star. New evidence indicating that a massive sodium cloud observed near WASP-49 b is produced by neither the planet nor the star has prompted researchers to ask if its origin could be an exomoon.NASA/JPL-Caltech The existence of a moon located outside our solar system has never been confirmed but a new NASA-led study may provide indirect evidence for one.
New research done at NASA’s Jet Propulsion Laboratory reveals potential signs of a rocky, volcanic moon orbiting an exoplanet 635 light-years from Earth. The biggest clue is a sodium cloud that the findings suggest is close to but slightly out of sync with the exoplanet, a Saturn-size gas giant named WASP-49 b, although additional research is needed to confirm the cloud’s behavior. Within our solar system, gas emissions from Jupiter’s volcanic moon Io create a similar phenomenon.
Although no exomoons (moons of planets outside our solar system) have been confirmed, multiple candidates have been identified. It’s likely these planetary companions have gone undetected because they are too small and dim for current telescopes to detect.
The sodium cloud around WASP-49 b was first detected in 2017, catching the attention of Apurva Oza, formerly a postdoctoral researcher at NASA’s Jet Propulsion Laboratory and now a staff scientist at Caltech, which manages JPL. Oza has spent years investigating how exomoons might be detected via their volcanic activity. For example, Io, the most volcanic body in our solar system, constantly spews sulfur dioxide, sodium, potassium, and other gases that can form vast clouds around Jupiter up to 1,000 times the giant planet’s radius. It’s possible that astronomers looking at another star system could detect a gas cloud like Io’s even if the moon itself were too small to see.
Exomoons — moons around planets outside our solar system — are most likely too small to observe directly with current technology. In this video, learn how scientists tracked the motion of a sodium cloud 635 light-years away and found that it could be created by volcanos on a potential exomoon. NASA/JPL-Caltech Both WASP-49 b and its star are composed mostly of hydrogen and helium, with trace amounts of sodium. Neither contains enough sodium to account for the cloud, which appears to be coming from a source that is producing roughly 220,000 pounds (100,000 kilograms) of sodium per second. Even if the star or planet could produce that much sodium, it’s unclear what mechanism could eject it into space.
Could the source be a volcanic exomoon? Oza and his colleagues set out to try to answer that question. The work immediately proved challenging because from such a great distance, the star, planet, and cloud often overlap and occupy the same tiny, faraway point in space. So the team had to watch the system over time.
A Cloud on the Move
As detailed in a new study published in the Astrophysical Journal Letters, they found several pieces of evidence that suggest the cloud is created by a separate body orbiting the planet, though additional research is needed to confirm the cloud’s behavior. For example, twice their observations indicated the cloud suddenly increased in size, as if being refueled, when it was not next to the planet.
New NASA-led research suggests a sodium cloud seen around the exoplanet WASP-49 b might be created by a volcanic moon, which is depicted in this artist’s concept. Jupiter’s fiery moon Io produces a similar cloud. NASA/JPL-Caltech They also observed the cloud moving faster than the planet in a way that would seem impossible unless it was being generated by another body moving independent of, and faster, than the planet.
“We think this is a really critical piece of evidence,” said Oza. “The cloud is moving in the opposite direction that physics tells us it should be going if it were part of the planet’s atmosphere.”
While these observations have intrigued the research team, they say they would need to observe the system for longer to be sure of the cloud’s orbit and structure.
A Chance of Volcanic Clouds
For part of their sleuthing, the researchers used the European Southern Observatory’s Very Large Telescope in Chile. Oza’s co-author Julia Seidel, a research fellow at the observatory, established that the cloud is located high above the planet’s atmosphere, much like the cloud of gas Io produces around Jupiter.
They also used a computer model to illustrate the exomoon scenario and compare it to the data. The exoplanet WASP-49 b orbits the star every 2.8 days with clocklike regularity, but the cloud appeared and disappeared behind the star or behind the planet at seemingly irregular intervals. Using their model, Oza and team showed that a moon with an eight-hour orbit around the planet could explain the cloud’s motion and activity, including the way it sometimes seemed to move in front of the planet and did not seem to be associated with a particular region of the planet.
“The evidence is very compelling that something other than the planet and star are producing this cloud,” said Rosaly Lopes, a planetary geologist at JPL who co-authored the study with Oza. “Detecting an exomoon would be quite extraordinary, and because of Io, we know that a volcanic exomoon is possible.”
A Violent End
On Earth, volcanoes are driven by heat in its core left over from the planet’s formation. Io’s volcanoes, on the other hand, are driven by Jupiter’s gravity, which squeezes the moon as it gets closer to the planet then reduces its “grip” as the moon moves away. This flexing heats the small moon’s interior, leading to a process called tidal volcanism.
If WASP-49 b has a moon similar in size to Earth’s, Oza and team estimate that the rapid loss of mass combined with the squeezing from the planet’s gravity will eventually cause it to disintegrate.
“If there really is a moon there, it will have a very destructive ending,” said Oza.
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Last Updated Oct 10, 2024 Related Terms
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By NASA
Artists Concept of the WASP-77 A b system. A planet swings in front of its star, dimming the starlight we see. Events like these, called transits, provide us with bounties of information about exoplanets–planets around stars other than the Sun. But predicting when these special events occur can be challenging…unless you have help from volunteers.
Luckily, a collaboration of multiple teams of amateur planet-chasers, led by researcher Federico R. Noguer from Arizona State University and researchers from NASA’s Jet Propulsion Laboratory (JPL) and Goddard Space Flight Center (GSFC), has taken up the challenge. This collaboration has published the most precise physical and orbital parameters to date for an important exoplanet called WASP-77 A b. These precise parameters help us predict future transit events and are crucial for planning spacecraft observations and accurate atmospheric modeling.
“As a retired dentist and now citizen scientist for Exoplanet Watch, research opportunities like this give me a way to learn and contribute to this amazingly exciting field of astrophysics,” said Anthony Norris, a citizen scientist working on the NASA-funded Exoplanet Watch project.
The study combined amateur astronomy/citizen science data from the Exoplanet Watch and ExoClock projects, as well as the Exoplanet Transit Database. It also incorporated data from NASA’s Spitzer Space Telescope, the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), and La Silla Observatory. Exoplanet Watch invites volunteers to participate in groundbreaking exoplanet research, using their own telescopes to observe exoplanets or by analyzing data others have gathered. You may have read another recent article about how the Exoplanet Watch team helped validate a new exoplanet candidate.
WASP-77 A b is a gas giant exoplanet that orbits a Sun-like star. It’s only about 20% larger than Jupiter. But that’s where the similarities to our solar system end. This blazing hot gas ball orbits right next to its star–more than 200 times closer to its star than our Jupiter!
Want a piece of the action? Join the Exoplanet Watch project and help contribute to cutting-edge exoplanet science! Anyone can participate–participation does not require citizenship in any particular country.
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Last Updated Sep 19, 2024 Related Terms
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