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By NASA
On Jan. 7, 1610, Italian astronomer Galileo Galilei peered through his newly improved 20-power homemade telescope at the planet Jupiter. He noticed three other points of light near the planet, at first believing them to be distant stars. Observing them over several nights, he noted that they appeared to move in the wrong direction with regard to the background stars and they remained in Jupiter’s proximity but changed their positions relative to one another. Four days later, he observed a fourth point of light near the planet with the same unusual behavior. By Jan. 15, Galileo correctly concluded that he had discovered four moons orbiting around Jupiter, providing strong evidence for the Copernican theory that most celestial objects did not revolve around the Earth.
Two of Galileo’s telescopes.National Geographic. Painting by Giuseppe Bertini (1858) of Galileo demonstrating his telescope to the Doge of Venice.gabrielevanin.it Page from Galileo’s notebook about his observations of Jupiter’s satellites.University of Michigan Special Collections Library. In March 1610, Galileo published his discoveries of Jupiter’s satellites and other celestial observations in a book titled Siderius Nuncius (The Starry Messenger). As their discoverer, Galileo had naming rights to Jupiter’s satellites. He proposed to name them after his patrons the Medicis and astronomers called them the Medicean Stars through much of the seventeenth century, although in his own notes Galileo referred to them by the Roman numerals I, II, III, and IV, in order of their distance from Jupiter. Astronomers still refer to the four moons as the Galilean satellites in honor of their discoverer.
In 1614, the German astronomer Johannes Kepler suggested naming the satellites after mythological figures associated with Jupiter, namely Io, Europa, Ganymede, and Callisto, but his idea didn’t catch on for more than 200 years. Scientists didn’t discover any more satellites around Jupiter until 1892 when American astronomer E.E. Barnard found Jupiter’s fifth moon Amalthea, much smaller than the Galilean moons and orbiting closer to the planet than Io. It was the last satellite in the solar system found by visual observation – all subsequent discoveries occurred via photography or digital imaging. As of today, astronomers have identified 95 moons orbiting Jupiter.
Image of Jupiter and three of its four Galilean satellites through an amateur telescope, similar to what Galileo might have seen. Hubble Space Telescope image of Jupiter and three of its four Galilean satellites during a rare triple transit. Although each of the Galilean satellites has unique features, such as the volcanoes of Io, the heavily cratered surface of Callisto, and the magnetic field of Ganymede, scientists have focused more attention on Europa due to the tantalizing possibility that it might be hospitable to life. In the 1970s, NASA’s Pioneer 10 and 11 and Voyager 1 and 2 spacecraft took ever increasingly detailed images of the large satellites including Europa during their flybys of Jupiter. The photographs revealed Europa to have the smoothest surface of any object in the solar system, indicating a relatively young crust, and also one of the brightest of any satellite indicating a highly reflective surface. These features led scientists to hypothesize that Europa is covered by an icy crust floating on a subsurface salty ocean. They further postulated that tidal heating caused by Jupiter’s gravity reforms the surface ice layer in cycles of melting and freezing.
Image of Europa taken by Pioneer 10 during its flyby of Jupiter in 1973. Image of Europa taken by Voyager 1 during its 1979 flyby of Jupiter. Image of Europa taken by Voyager 2 during its 1979 flyby of Jupiter. More detailed observations from NASA’s Galileo spacecraft that orbited Jupiter between 1995 and 2003 and completed 11 close encounters with Europa revealed that long linear features on its surface may indicate tidal or tectonic activity. Reddish-brown material along the fissures and in splotches elsewhere on the surface may contain salts and sulfur compounds transported from below the crust and modified by radiation. Observations from the Hubble Space Telescope and re-analysis of images from Galileo revealed possible plumes emanating from beneath Europa’s crust, lending credence to that hypothesis. While the exact composition of this material is not known, it likely holds clues to whether Europa may be hospitable to life.
Global view of Europa from the Galileo spacecraft. More detailed views of varied terrain on Europa from Galileo. Cutaway illustration of Europa’s icy crust, subsurface ocean and possible vents that transport material to the surface. Future robotic explorers of Europa may answer some of the outstanding questions about this unique satellite of Jupiter. NASA’s Europa Clipper set off in October 2024 on a 5.5-year journey to Jupiter. After its arrival in 2030, the spacecraft will enter orbit around the giant planet and conduct 49 flybys of Europa during its four-year mission. Managed by the Jet Propulsion Laboratory in Pasadena, California, and the Applied Physics Laboratory at Johns Hopkins University in Baltimore, Maryland, Europa Clipper will carry nine instruments including imaging systems and a radar to better understand the structure of the icy crust. Data from Europa Clipper will complement information returned by the European Space Agency’s JUICE (Jupiter Icy Moon Explorer) spacecraft. Launched in April 2023, JUICE will first enter orbit around Jupiter in 2031 and then enter orbit around Ganymede in 2034. The spacecraft also plans to conduct studies of Europa complementary with Europa Clipper’s. The two spacecraft should greatly increase our understanding of Europa and perhaps uncover new mysteries.
Illustration of the Europa Clipper spacecraft investigating Europa. Illustration of the JUICE spacecraft exploring Europa.European Space Agency. View the full article
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By NASA
NASA/Joel Kowsky NASA photographer Joel Kowsky captured this image of the Monday, April 8, 2024, total solar eclipse from the Indianapolis Motor Speedway in Indianapolis, Indiana. The total solar eclipse swept across a narrow portion of the North American continent from Mexico’s Pacific coast to the Atlantic coast of Newfoundland, Canada. A partial solar eclipse was visible across the entire North American continent along with parts of Central America and Europe.
The NASA Headquarters photo team chose this image as one of the best from 2024. See more of the top 100 from last year on Flickr.
Image Credit: NASA/Joel Kowsky
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By NASA
5 Min Read NASA’s Parker Solar Probe Makes History With Closest Pass to Sun
An artist’s concept showing Parker Solar Probe. Credits:
NASA/APL Operations teams have confirmed NASA’s mission to “touch” the Sun survived its record-breaking closest approach to the solar surface on Dec. 24, 2024.
Breaking its previous record by flying just 3.8 million miles above the surface of the Sun, NASA’s Parker Solar Probe hurtled through the solar atmosphere at a blazing 430,000 miles per hour — faster than any human-made object has ever moved. A beacon tone received late on Dec. 26 confirmed the spacecraft had made it through the encounter safely and is operating normally.
This pass, the first of more to come at this distance, allows the spacecraft to conduct unrivaled scientific measurements with the potential to change our understanding of the Sun.
Flying this close to the Sun is a historic moment in humanity’s first mission to a star.
Nicky fox
NASA Associate Administrator, Science Mission Directorate
“Flying this close to the Sun is a historic moment in humanity’s first mission to a star,” said Nicky Fox, who leads the Science Mission Directorate at NASA Headquarters in Washington. “By studying the Sun up close, we can better understand its impacts throughout our solar system, including on the technology we use daily on Earth and in space, as well as learn about the workings of stars across the universe to aid in our search for habitable worlds beyond our home planet.”
NASA’s Parker Solar Probe survived its record-breaking closest approach to the solar surface on Dec. 24, 2024. Breaking its previous record by flying just 3.8 million miles above the surface of the Sun, the spacecraft hurtled through the solar atmosphere at a blazing 430,000 miles per hour — faster than any human-made object has ever moved.
Credits: NASA This video can be freely shared and downloaded at https://svs.gsfc.nasa.gov/14741.
Parker Solar Probe has spent the last six years setting up for this moment. Launched in 2018, the spacecraft used seven flybys of Venus to gravitationally direct it ever closer to the Sun. With its last Venus flyby on Nov. 6, 2024, the spacecraft reached its optimal orbit. This oval-shaped orbit brings the spacecraft an ideal distance from the Sun every three months — close enough to study our Sun’s mysterious processes but not too close to become overwhelmed by the Sun’s heat and damaging radiation. The spacecraft will remain in this orbit for the remainder of its primary mission.
“Parker Solar Probe is braving one of the most extreme environments in space and exceeding all expectations,” said Nour Rawafi, the project scientist for Parker Solar Probe at the Johns Hopkins Applied Physics Laboratory (APL), which designed, built, and operates the spacecraft from its campus in Laurel, Maryland. “This mission is ushering a new golden era of space exploration, bringing us closer than ever to unlocking the Sun’s deepest and most enduring mysteries.”
Close to the Sun, the spacecraft relies on a carbon foam shield to protect it from the extreme heat in the upper solar atmosphere called the corona, which can exceed 1 million degrees Fahrenheit. The shield was designed to reach temperatures of 2,600 degrees Fahrenheit — hot enough to melt steel — while keeping the instruments behind it shaded at a comfortable room temperature. In the hot but low-density corona, the spacecraft’s shield is expected to warm to 1,800 degrees Fahrenheit.
The spacecraft’s record close distance of 3.8 million miles may sound far, but on cosmic scales it’s incredibly close. If the solar system was scaled down with the distance between the Sun and Earth the length of a football field, Parker Solar Probe would be just four yards from the end zone — close enough to pass within the tenuous outer atmosphere of the Sun known as the corona. NASA/APL “It’s monumental to be able to get a spacecraft this close to the Sun,” said John Wirzburger, the Parker Solar Probe mission systems engineer at APL. “This is a challenge the space science community has wanted to tackle since 1958 and had spent decades advancing the technology to make it possible.”
By flying through the solar corona, Parker Solar Probe can take measurements that help scientists better understand how the region gets so hot, trace the origin of the solar wind (a constant flow of material escaping the Sun), and discover how energetic particles are accelerated to half the speed of light.
“The data is so important for the science community because it gives us another vantage point,” said Kelly Korreck, a program scientist at NASA Headquarters and heliophysicist who worked on one of the mission’s instruments. “By getting firsthand accounts of what’s happening in the solar atmosphere, Parker Solar Probe has revolutionized our understanding of the Sun.”
Previous passes have already aided scientists’ understanding of the Sun. When the spacecraft first passed into the solar atmosphere in 2021, it found the outer boundary of the corona is wrinkled with spikes and valleys, contrary to what was expected. Parker Solar Probe also pinpointed the origin of important zig-zag-shaped structures in the solar wind, called switchbacks, at the visible surface of the Sun — the photosphere.
Since that initial pass into the Sun, the spacecraft has been spending more time in the corona, where most of the critical physical processes occur.
This conceptual image shows Parker Solar Probe about to enter the solar corona. NASA/Johns Hopkins APL/Ben Smith “We now understand the solar wind and its acceleration away from the Sun,” said Adam Szabo, the Parker Solar Probe mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This close approach will give us more data to understand how it’s accelerated closer in.”
Parker Solar Probe has also made discoveries across the inner solar system. Observations showed how giant solar explosions called coronal mass ejections vacuum up dust as they sweep across the solar system, and other observations revealed unexpected findings about solar energetic particles. Flybys of Venus have documented the planet’s natural radio emissions from its atmosphere, as well as the first complete image of its orbital dust ring.
So far, the spacecraft has only transmitted that it’s safe, but soon it will be in a location that will allow it to downlink the data it collected on this latest solar pass.
The data that will come down from the spacecraft will be fresh information about a place that we, as humanity, have never been.
Joe Westlake
Heliophysics Division Director, NASA Headquarters
“The data that will come down from the spacecraft will be fresh information about a place that we, as humanity, have never been,” said Joe Westlake, the director of the Heliophysics Division at NASA Headquarters. “It’s an amazing accomplishment.”
The spacecraft’s next planned close solar passes come on March 22, 2025, and June 19, 2025.
By Mara Johnson-Groh
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact: Sarah Frazier
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Goddard Space Flight Center Heliophysics Heliophysics Division Parker Solar Probe (PSP) Science & Research Science Mission Directorate Solar Flares Solar Wind Space Weather The Sun The Sun & Solar Physics Explore More
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By NASA
5 Min Read NASA’s Ames Research Center Celebrates 85 Years of Innovation
The NACA Ames laboratory in 1944 Credits: NASA Ames Research Center in California’s Silicon Valley pre-dates a lot of things. The center existed before NASA – the very space and aeronautics agency it’s a critical part of today. And of all the marvelous advancements in science and technology that have fundamentally changed our lives over the last 85 years since its founding, one aspect has remained steadfast; an enduring commitment to what’s known by some on-center simply as, “an atmosphere of freedom.”
Years before breaking ground at the site that would one day become home to the world’s preeminent wind tunnels, supercomputers, simulators, and brightest minds solving some of the world’s toughest challenges, Joseph Sweetman Ames, the center’s namesake, described a sentiment that would guide decades of innovation and research:
My hope is that you have learned or are learning a love of freedom of thought and are convinced that life is worthwhile only in such an atmosphere
Joseph sweetman ames
Founding member of the N.A.C.A.
“My hope is that you have learned or are learning a love of freedom of thought and are convinced that life is worthwhile only in such an atmosphere,” he said in an address to the graduates of Johns Hopkins University in June 1935.
That spirit and the people it attracted and retained are a crucial part of how Ames, along with other N.A.C.A. research centers, ultimately made technological breakthroughs that enabled humanity’s first steps on the Moon, the safe return of spacecraft through Earth’s atmosphere, and many other discoveries that benefit our day-to-day lives.
Russell Robinson momentarily looks to the camera while supervising the first excavation at what would become Ames Research Center.NACA “In the context of my work, an atmosphere of freedom means the freedom to pursue high-risk, high-reward, innovative ideas that may take time to fully develop and — most importantly — the opportunity to put them into practice for the benefit of all,” said Edward Balaban, a researcher at Ames specializing in artificial intelligence, robotics, and advanced mission concepts.
Balaban’s career at Ames has involved a variety of projects at different stages of development – from early concept to flight-ready – including experimenting with different ways to create super-sized space telescopes in space and using artificial intelligence to help guide the path a rover might take to maximize off-world science results. Like many Ames researchers over the years, Balaban shared that his experience has involved deep collaborations across science and engineering disciplines with colleagues all over the center, as well as commercial and academic partners in Silicon Valley where Ames is nestled and beyond. This is a tradition that runs deep at Ames and has helped lead to entirely new fields of study and seeded many companies and spinoffs.
Before NASA, Before Silicon Valley: The 1939 Founding of Ames Aeronautical Laboratory “In the fields of aeronautics and space exploration the cost of entry can be quite high. For commercial enterprises and universities pursuing longer term ideas and putting them into practice often means partnering up with an organization such as NASA that has the scale and multi-disciplinary expertise to mature these ideas for real-world applications,” added Balaban.
“Certainly, the topics of inquiry, the academic freedom, and the benefit to the public good are what has kept me at Ames,” reflected Ross Beyer, a planetary scientist with the SETI Institute at Ames. “There’s not a lot of commercial incentive to study other planets, for example, but maybe there will be soon. In the meantime, only with government funding and agencies like NASA can we develop missions to explore the unknown in order to make important fundamental science discoveries and broadly share them.”
For Beyer, his boundary-breaking moment came when he searched – and found – software engineers at Ames capable and passionate about open-source software to generate accurate, high-resolution, texture-mapped, 3D terrain models from stereo image pairs. He and other teams of NASA scientists have since applied that software to study and better understand everything from changes in snow and ice characteristics on Earth, as well as features like craters, mountains, and caves on Mars or the Moon. This capability is part of the Artemis campaign, through which NASA will establish a long-term presence at the Moon for scientific exploration with commercial and international partners. The mission is to learn how to live and work away from home, promote the peaceful use of space, and prepare for future human exploration of Mars.
“As NASA and private companies send missions to the Moon, they need to plan landing sites and understand the local environment, and our software is freely available for anyone to use,” Beyer said. “Years ago, our management could easily have said ‘No, let’s keep this software to ourselves; it gives us a competitive advantage.’ They didn’t, and I believe that NASA writ large allows you to work on things and share those things and not hold them back.”
When looking forward to what the next 85 years might bring, researchers shared a belief that advancements in technology and opportunities to innovate are as expansive as space itself, but like all living things, they need a healthy atmosphere to thrive. Balaban offered, “This freedom to innovate is precious and cannot be taken for granted. It can easily fall victim if left unprotected. It is absolutely critical to retain it going forward, to ensure our nation’s continuing vitality and the strength of the other freedoms we enjoy.”
Ames Aeronautical Laboratory.NACAView the full article
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