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National Geographic
7 days ago
- Science
- National Geographic
The best window to see Pluto all year is closing
Pluto's thin, blue haze glows in this image from NASA's New Horizons spacecraft. Though the dwarf planet is just a faint speck through a telescope, opposition this month offers skywatchers their best chance to spot it from Earth. Composite Photograph by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute A once-a-year alignment makes the dwarf planet easier to spot—if you know where to look. Think you can spot Pluto? On July 25, the famously elusive dwarf planet reaches opposition—its best and brightest moment of the year. That makes now the ideal time to try to catch a glimpse of it from your own backyard. But be warned: Even at its brightest, Pluto is still a barely-there speck, even through a telescope. But for those willing to search, it's a cosmic scavenger hunt—and a rare chance to see a world nearly four billion miles away. What is opposition—and why is it the best time to see Pluto? In astronomy, opposition is when a celestial body lies directly opposite the sun from Earth's point of view, placing our planet squarely in the middle. That alignment means the object rises as the sun sets and stays visible all night, making it the best time to observe it. (See National Geographic's first map of Pluto.) What makes opposition so useful for stargazing is a phenomenon known as the opposition effect. 'Things tend to get brighter when they're lit at a smaller phase angle, which is the angle between the sun's rays and the target and the observer. That shrinks to close to zero at opposition,' says Will Grundy, a planetary scientist at Lowell Observatory in Flagstaff, Arizona, where Pluto was discovered. You can see this principle in action on Earth. When the sun is low in the sky, objects create long shadows. But when the sun is directly overhead, those shadows get much smaller, and sometimes they even disappear entirely. At opposition, Pluto's terrain has the fewest shadows, making the dwarf planet appear brighter to us. Pluto and its moon Charon perform a cosmic dance in this 2015 color movie from NASA's New Horizons mission. Animation by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute Pluto nearly fills the frame in this image from NASA's New Horizons spacecraft, taken just before its closest approach in 2015. Photograph by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute Because Pluto is so dim, you need a telescope to see it. 'A backyard telescope could do it under the right conditions,' says Grundy. Or you could visit a local observatory and use one of their publicly accessible telescopes. Lowell Observatory, for instance, has a suite of instruments on-site that the public can use six nights per week. But even with a telescope, the sky must be extremely dark to see Pluto. Light pollution, whether from artificial lights or the moon, will easily wash out the dwarf planet. (Did Pluto ever actually stop being a planet? Experts debate.) To find Pluto in dark enough skies, consult a star chart to determine its approximate location. 'It'll just look like one of many faint stars,' says Grundy. But Pluto moves slowly. 'It moves at about three arcseconds per hour, so you won't see it move unless you're willing to wait multiple hours,' says Grundy. You don't have to catch Pluto on July 25 exactly. Because it's so distant—about 3.7 billion miles from the sun—it remains near peak brightness for several days before and after opposition. 'It's a challenge, so it's kind of cool to be able to see Pluto,' says Grundy. These photographic plates helped astronomer Clyde Tombaugh discover Pluto in 1930. By comparing nearly identical images of the night sky with a device called a blink comparator, he found a tiny object (marked by arrows) outside the orbit of Neptune, which was named Pluto. Photograph by Detlev Van Ravenswaay, Science Photo Library Pluto's origin story begins with two other planets. After Uranus was discovered in 1781, astronomers realized that an undiscovered planet might be perturbing Uranus' orbit. 'Sure enough, Neptune was discovered basically bang-on where astronomers predicted it should be,' says Grady. But Percival Lowell, the founder of Lowell Observatory, believed there to be another planet affecting Uranus' orbit: a mysterious 'Planet X.' After a decade of searching, Lowell died in 1916 without finding it. (Discover seven other night sky events to see in July.) Eventually, the search resumed at Lowell Observatory, culminating in Clyde Tombaugh's discovery of Pluto in 1930. As it turns out, Pluto wasn't the gravitational culprit Lowell had imagined. It was far too small to tug on Uranus's orbit in any meaningful way. But it was still a monumental discovery: the solar system's ninth planet—at least until its reclassification as a dwarf planet in 2006. To find Pluto, Tombaugh diligently photographed the night sky, then used a machine to compare two photographic plates, looking for any tiny pinpricks that moved. That's essentially the same method Grundy suggests stargazers use in July to ensure they're looking at Pluto. Following its discovery, Pluto remained just a faint dot until the 1990s, when the Hubble Space Telescope provided some grainy images showing light and dark spots. But it wasn't until 2015 that we got a close-up look at Pluto, thanks to a flyby by NASA's New Horizons spacecraft. The images showed a dynamic, geologically active planet with icy mountains, nitrogen glaciers, and even hints of a subsurface ocean. 'It could be inhabitable if there's liquid water and lots of organic materials and rocks for minerals,' says Grundy, who serves as a co-investigator on the New Horizons mission. That revelation has major implications for astrobiology. 'Pluto moved the goalpost of where inhabitable planetary settings are—much, much farther away from the sun than we ever thought possible,' says Grundy. 'And the same thing will be true around other stars, too. Basically, the inhabitable zone just expanded hugely.'
UPI
12-07-2025
- Science
- UPI
Pluto photos from NASA's New Horizons still captivating scientists decade later
NASA's New Horizon spacecraft captured this image of Pluto on July 14, 2015, showing the planet's diversity of geological and compositional features. File Photo courtesy of NASA | License Photo For decades, Pluto remained one of the most mysterious objects in our solar system, until July 14, 2015, when NASA's New Horizons spacecraft became the first mission to visit it up close, capturing breathtaking images of the distant world. It took over nine years for New Horizons to reach Pluto after blasting off atop an Atlas 5 rocket on Jan. 19, 2006. After traveling billions of miles through the solar system, New Horizons sent home stunning images of Pluto and its moons, making headlines around the world. It took more than 15 months for the spacecraft to send all of the 6.25 gigabytes of photos and data home for scientists to study. "Such a lengthy period was necessary because the spacecraft was roughly 4.5 light-hours from Earth and it could only transmit 1-2 kilobits per second," NASA said. Here are some of the best images of Pluto and its moon Charon: A composite of enhanced color images of Pluto (lower right) and Charon (upper left), taken by NASA's New Horizons spacecraft as it passed through the Pluto system on July 14, 2015. Photo courtesy of NASA This image of haze layers above Pluto limb was taken by NASA New Horizons spacecraft. About 20 haze layers are seen. Photo courtesy of NASA Pluto nearly fills the frame in this image from NASA's New Horizons spacecraft. The image was taken on July 13, 2015, when the spacecraft was 476,000 miles (768,000 kilometers) from the surface. Photo by NASA, Johns Hopkins University Applied Physics Laboratory and Southwest Research Institute NASA New Horizons scientists believe that the informally named feature Wright Mons, located south of Sputnik Planum on Pluto, and another, Piccard Mons, could have been formed by the cryovolcanic eruption of ices from beneath Pluto's surface. Photo courtesy of NASA and JPL A detailed global mosaic color map of Pluto is based on a series of three color filter images obtained by the Ralph/Multispectral Visual Imaging Camera aboard New Horizons during the NASA spacecraft's close flyby of Pluto in July 2015. Photo by NASA and JPL The International Astronomical Union (IAU), the internationally recognized authority for naming celestial bodies and their surface features, approved names of 14 surface features on Pluto in August 2017. Image from NASA, Johns Hopkins University Applied Physics Laboratory and Southwest Research Institute An enhanced color mosaic of Pluto taken approximately 15 minutes before New Horizons' closest approach to Pluto. Image by NASA, Johns Hopkins University Applied Physics Laboratory and Southwest Research Institute This image was made just 15 minutes after New Horizons' closest approach to Pluto on July 14, 2015, as the spacecraft looked back at Pluto toward the sun. Photo courtesy fo NASA and JPL The Pluto flyby changed what astronomers thought they knew about that tiny world. Instead of being just a cold rock, Pluto turned out to have ice mountains as tall as the Rockies, strange heart-shaped plains and even signs of possible underground oceans. The mission also gave us our first close-up look at Pluto's largest moon, Charon, which has deep canyons and a huge dark spot at the pole. It was like discovering a whole new world hiding at the edge of our solar system.
Yahoo
11-07-2025
- Science
- Yahoo
Pluto photos from NASA's New Horizons still captivating scientists decade after historic flyby
For decades, Pluto remained one of the most mysterious objects in our solar system, until July 14, 2015, when NASA's New Horizons spacecraft became the first mission to visit it up close, capturing breathtaking images of the distant world. It took over nine years for New Horizons to reach Pluto after blasting off atop an Atlas 5 rocket on Jan. 19, 2006. After traveling billions of miles through the solar system, New Horizons sent home stunning images of Pluto and its moons, making headlines around the world. It took more than 15 months for the spacecraft to send all of the 6.25 gigabytes of photos and data home for scientists to study. "Such a lengthy period was necessary because the spacecraft was roughly 4.5 light-hours from Earth and it could only transmit 1-2 kilobits per second," NASA said. Here are some of the best images of Pluto and its moon Charon: The Pluto flyby changed what astronomers thought they knew about that tiny world. Instead of being just a cold rock, Pluto turned out to have ice mountains as tall as the Rockies, strange heart-shaped plains and even signs of possible underground oceans. The mission also gave us our first close-up look at Pluto's largest moon, Charon, which has deep canyons and a huge dark spot at the pole. It was like discovering a whole new world hiding at the edge of our solar system.
National Geographic
27-06-2025
- Science
- National Geographic
Moons
With volcanoes, frozen oceans, and methane seas, moons are often much more than balls of rock circling a body other than the sun. In fact, the only definitive thing that separates many moons from planets like the Earth and Mars is what they revolve around. Planets circle the sun; moons circle the things that circle the sun—planets, dwarf planets, and other so-called small solar system bodies. Otherwise, moons are diverse and fascinating worlds unto their own. Earth's Moon and Europa One of four planet-size moons in orbit around the planet Jupiter, Europa has an almost glassy surface of ice that scientists say may cover an ocean that is 31 miles (50 kilometers) deep. Tidal forces between Jupiter and Europa are believed to generate enough heat to keep the ocean liquid. Observations with the Hubble Space Telescope also indicate Europa has a tenuous atmosphere of oxygen. The combination of water, a heat source, and an atmosphere raises the possibility that Europa harbors life. The best known moon is the one in orbit around planet Earth. It is Earth's only natural satellite and the only extraterrestrial body that humans have visited. Gravity on the moon is one-sixth of Earth's gravity, allowing astronauts to take giant leaps on its surface. The moon lacks an atmosphere, but spacecraft have found water ice at both poles, deposited from impacting comets. According to a leading theory, a Mars-size body smacked Earth about 4.5 billion years ago and the debris from the collision accumulated to form its moon. But unlike Earth's moon, many moons formed from the same material that glommed together and gave rise to the body they orbit. Other moons are asteroids captured into orbit by a larger body's gravity. Only the dwarf planet Pluto's moon Charon is thought to have formed from a collision like the one that gave rise to Earth's moon. No matter how they form, the moons are many. Only Mercury and Venus are moonless. Earth has one, Mars two. Neptune has 13 and Uranus 27. The gas giant Jupiter has 63 known moons. Saturn has at least 60—and 42 of those have been discovered since 1997. The dwarf planet Pluto has three moons. Eris, another dwarf planet, has one moon. Dozens more moons orbit small solar system bodies.
The Hindu
21-06-2025
- Science
- The Hindu
Is it a moon? Is it a dwarf planet? Well, it's Charon, and it could well be both!
Charon's discovery The story of Charon's discovery takes us back to 1978 – a time when even astronomers were still thinking that Pluto was a planet. Little was known about Pluto and its system, but all that was about to change in the decades that followed. On the morning of June 22, American astronomer James Christy already had his head whirling around. If you were under the impression that he was zeroing in on the solution for an astronomical problem, you couldn't be further from the truth. Christy was sharpening his plans to move his house, getting ready for a week's leave from the U.S. Naval Observatory in Flagstaff, Arizona – his workplace. It was under these circumstances that Robert Harrington, his boss, handed him a set of six photographs of Pluto. Christy and Harrington were looking to refine Pluto's orbit around the sun – a journey that takes Pluto 248 Earth years. Pluto's average distance from the sun is 5.9 billion km. The technology available at that time meant that even the best photographs of it hardly revealed anything. What's more, these six images – acquired in pairs over three nights in the month between April 13 and May 12 – were labelled as 'defective.' Odd blobs The reason why these pictures were labelled thus owed to the fact that they revealed Pluto to be oddly elongated. Viewing them under a microscope, Christy noticed that the fuzzy blob that was to be Pluto stretched in a northern direction in two of those pairs, while the final pair showed a southward direction. The defects were attributed either to atmospheric distortion or improper optical alignment in the telescope used for observations. After ruling out an explosion on Pluto as an unlikely explanation – especially as it lasted a month – Christy searched for other plausible reasons. There was a chance that Pluto itself was irregular in shape. Or could there be an unseen moon, even though one of his former professors, celebrated Dutch-American astronomer Gerard Kuiper, had searched for exactly the same decades earlier without any success? When Christy went over to the archives to check through older plates from 1965 onwards, there it was... the same elongation. What's more, all these images had also been dismissed as defective on every occasion. Correct conclusions Christy and Harrington, however, realised that they were onto something. By reviewing all the images with the elongations, they were able to state that the bulge occurred with a predictable frequency. This frequency of the unseen moon's orbital period – 6.4 Earth days – matched with what astronomers believed to be Pluto's rotational period, suggesting a synchronously locked binary system. The duo ruled out other possible reasons for the bulge and concluded correctly that Pluto had another companion at a distance of 19,640 km. The discovery of 'S/1978 P1' was announced by them through the International Astronomical Union (IAU) on July 7 and their findings were published in the Astronomical Journal. What started out as reviewing six defective images, served as the seeds for a whole new discovery. As Christy himself once pointed out, 'Discovery is where the scientist touches nature in its least predictable aspect.' What's in a name? As the discoverer, Christy wanted to exercise his rights for naming Pluto's companion. And he had his mind set on naming it after his wife. The Naval Observatory he worked for had suggested the name Persephone, the wife of Hades. Hades, the god of the underworld in Greek mythology, was the equivalent of the Roman god Pluto after which it is named. As luck would have it, Christy came across a reference to Charon, a boatman who ferried the dead across a river in the underworld to Hades. Charon's close mythical association with Hades, or Pluto, made it a great option for the newly discovered astronomical object. It was the perfect option for Christy as his wife's name was Charlene. In addition to sharing the first four letters, 'Char' was the nickname that friends and family used to call his wife. Just like how protons and electrons have the 'on' suffix, Christy saw Charon as 'Char' with the suffix 'on' and submitted his name. Eclipses and occultations By the time this name was accepted by IAU in January 1986, Pluto and Charon had a series of mutual eclipses and occultations. Studying them enabled astronomers in general, and Harrington in particular, to confirm the existence of Charon as he observed the eclipses and occultations to occur as predicted. Observing Pluto and Charon in this manner also enabled astronomers to arrive at Charon's diameter to be about 1,200 km, while also arriving at better estimates of the size and mass of Pluto. From a small dot in a photograph, Charon had become much much more – almost a world in its own right. It definitely meant the world to Christy in more ways than one, as he was also able to gift his wife the moon! Charlene Christy probably summed it the best when she said 'A lot of husbands promise their wives the moon, but Jim actually delivered.' Charon fact sheet Most of what we know about Charon, or even Pluto for that matter, is thanks to NASA's New Horizons mission. Approved in 2001 as the first flyby of Pluto and its largest moon Charon, it was launched in January 2006. This was months before IAU's decision in August the same year to demote Pluto's designation from a planet to a dwarf planet. Despite the fact that Pluto was plutoed, the mission went on, providing us invaluable information. Before New Horizons' closest approach to Pluto on July 14, 2015, the spacecraft captured plenty of images of Charon. While the images revealed a striking reddish north (top) polar region, Charon's colour palette wasn't as diverse as Pluto's. The origins of this red colouration is a mystery for now and no other icy object in the solar system sports a similar feature. Charon is 1,214 km across and is at a distance of 19,640 km from Pluto. As Pluto's equatorial diameter is about 2,377 km, Charon is nearly half the size of Pluto. This makes it the largest known satellite relative to its parent body for most astronomers. It is this same size, however, that forces other astronomers to consider Pluto and Charon as a double dwarf planet system. Charon's orbit takes 6.4 Earth days to go around Pluto. Charon neither rises or sets, however, but instead hovers near the same region on Pluto's surface. The same surfaces of Charon and Pluto always face each other due to a phenomenon called mutual tidal locking.
