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The rings of Saturn are some of the most well-known and captivating spectacles in the night sky, which are so large they can easily be observed with amateur telescopes or even a pair of high-powered binoculars. However, from time to time, Saturn’s rings “disappear” from view, a phenomenon known ring-plane crossing, with the rings being observed as a flat line running straight through the massive gas giant. Ring-plane crossing occurs approximately every 15 years and is slated to happen next in March 2025, with the rings slowly getting “larger” in the months afterwards before “disappearing” again in November 2025. But what causes ring-plane crossing?

Saturn’s ring-plane crossing is due to the viewing angles from Earth changing as both planets are tilted during their respective orbits around our Sun and orbit at different speeds and times, as the Earth orbits the Sun in one year, Saturn takes approximately 29.4 years to complete one orbit. As a result, our view of Saturn changes over time, and the “size” of the rings appear to get larger and smaller, and periodically disappear entirely from view for a short time. As noted, ring-plane crossing happens approximately every 15 years, with the most recent occurrence being observed directly from Earth happening in 2009. However, both the 2009 and 2025 events are not observable from Earth since Saturn will be too close to the Sun.

NASA’s Hubble Space Telescope captured some fantastic images of Saturn’s rings edge-on in 1995, which provided astronomers the opportunity to observe some of Saturn’s larger moons and try to discover new moons, as well. The reason why ring-plane crossing allows astronomers to find new moons is due to the decreased glare of the bright rings that normally obscure smaller objects orbiting Saturn from being seen. In fact, between 1655 and 1980, ring-plane crossing is responsible for astronomers discovering 13 new moons of Saturn, with additional moons of Saturn being discovered by NASA’s Voyager 1 spacecraft in 1980. Two of Saturn’s most well-known moons, Enceladus and Mimas (aka the Death Star), were discovered by William Herschel during the ring-plane crossing of 1789-1790, and Hyperion was discovered during the ring-plane crossing of 1848-1849.

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Image of ring-plane crossing at Saturn taken by NASA’s Hubble Space Telescope in May 1995, with a similar ring-plane crossing event scheduled to occur in March 2025. (Credit: Reta Beebe (New Mexico State University), D. Gilmore, L. Bergeron (STScI), NASA/ESA, Amanda S. Bosh (Lowell Observatory), Andrew S. Rivkin (Univ. of Arizona/LPL), the HST High Speed Photometer Instrument Team (R.C. Bless, PI), and NASA/ESA)

Ring-crossing was accidentally discovered by Galileo Galilei in 1612, who is also responsible for first discovering Saturn’s rings only two years earlier. When he observed the rings had apparently disappeared, he wrote in his notes, “I do not know what to say in a case so surprising, so unlooked for and so novel”.

As noted, ring-plane crossing occurs due to the combination of the tilts of Earth and Saturn and their respective orbits, which also influences the north-south direction of the rings during the crossing. For example, the ring-plane crossing event occurring in March 2025 will see Saturn’s rings proceed from south to north, but this contrasts with the ring-plane crossing event that will occur several decades from now in August 2068. For this event, the rings will proceed from north to south.

While ring-plane crossing causes Saturn’s rings to give the illusion they are “disappearing”, this illusion won’t be around forever. This is because the icy grains that comprise Saturn’s rings are slowly being lost to the planet with a 2019 study used ground-based observations to estimate the rings will be gone for good in approximately 292 million years. Most recently, a 2023 study used data from NASA’s Cassini mission to provide a larger range of the remaining lifespan of Saturn’s rings at between 15 to 400 million years.

What new discoveries will astronomers make using Saturn’s ring-plane crossing in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

The post Saturn’s Rings will Disappear in 2025. Don’t Worry, They’ll Return Soon Enough appeared first on Universe Today.

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5 Reasons You Must Backpack Idaho’s Sawtooth Mountains

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By Michael Lanza

Chances are that, by now, you’ve heard of Idaho’s Sawtooths—having typed that name into a search box may be the reason you’ve landed on this story. Maybe you’ve been intrigued at what you’ve heard or images you’ve seen from Idaho’s best-known mountain range. Perhaps you’ve even been there and the experience has only amplified your curiosity to see more of this range.

As someone who’s had the good fortune of having backpacked all over the country and in many other countries over the past three-plus decades, including the 10 years I spent as a field editor for Backpacker magazine and even longer running this blog, I rank the Sawtooths among the 10 best backpacking trips in America.

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Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.
” data-image-caption=”Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg?fit=200%2C300&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg?fit=683%2C1024&ssl=1″ src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho-683×1024.jpg?resize=683%2C1024&ssl=1″ alt=”Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.” class=”wp-image-45355″ style=”width:572px;height:auto” srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 683w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 200w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 800w” sizes=”(max-width: 683px) 100vw, 683px” data-recalc-dims=”1″ />Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.

I’ve wandered around the Sawtooths at least a couple dozen times over more than two decades, including numerous backpacking trips, dayhikes, peak scrambles, rock climbing, and backcountry skiing. While there remain peaks on my list to climb, a few trails to hike, and many lakes to leap into (or just sit beside), the Sawtooths have become my backyard mountains. I feel at home there.

This story presents the five reasons I think every backpacker should take a multi-day hike through the Sawtooths—spotlighting the characteristics of a trip there that make this place unique. I believe this argument may persuade you to go (if, somehow, the photos don’t do it).

See my e-book “The Best Backpacking Trip in Idaho’s Sawtooth Mountains” to learn all you need to know to plan and pull off a five-day, 36-mile Sawtooths hike through the core of the Sawtooths, and my Custom Trip Planning page to learn how I can help you plan every detail of a multi-day hike there.

Please share your thoughts or experiences there in the comments section at the bottom of this story. I
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The Venerable Hubble Space Telescope Keeps Delivering

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The world was much different in 1990 when NASA astronauts removed the Hubble Space Telescope from Space Shuttle Discovery’s cargo bay and placed it into orbit. The Cold War was ending, there were only 5.3 billion humans, and the World Wide Web had just come online.

Now, the old Soviet Union is gone, replaced by a smaller but no less militaristic Russia. The human population has ballooned to 8.1 billion. The internet is a fixture in daily life. We also have a new, more powerful space telescope, the JWST.

But the Hubble keeps delivering, as this latest image shows.

The lenticular galaxy NGC 4753 is about 60 million light-years away. Lenticular galaxies are midway between elliptical and spiral galaxies. They have large-scale disks but only poorly defined spiral arms. NGC 4753 sees very little star formation because like other lenticulars, it’s used up most of its gas. The fact that they contain mostly older stars makes them similar to elliptical galaxies.

Among lenticulars, NGC 4753 is known for the dust lanes surrounding its nucleus. Astronomers think that spirals evolve into lenticulars in dense environments because they interact with other galaxies and with the intergalactic medium. However, NGC 4753 is in a low-density environment. Its environment and complex structure make it a target for astronomers to test their theories of galaxy formation and evolution.

This Hubble image is the sharpest ever taken of NGC 4753, revealing its intriguing complexity and highlighting the space telescope’s impressive resolving power.

Astronomers think that NGC 4753 is the result of a merger with a dwarf galaxy over one billion years ago. The dwarf galaxy was gas-rich, and NGC 4753's distinct dust rings probably accreted from the merger. NGC 4753's powerful gravity then shaped the gas into the complex shapes we see in this image. Image Credit: ESA/Hubble & NASA, L. Kelsey
Astronomers think that NGC 4753 is the result of a merger with a dwarf galaxy over one billion years ago. The dwarf galaxy was gas-rich, and NGC 4753’s distinct dust rings probably accreted from the merger. NGC 4753’s powerful gravity then shaped the gas into the complex shapes we see in this image. Image Credit: ESA/Hubble & NASA, L. Kelsey

NGC 4763’s unique structure results from a merger with a dwarf galaxy about 1.3 billion years ago. The video below from NOIRlab explains what happened.

NGC 4753 also hosts two known Type 1a supernovae, which are important because they help astronomers study the expansion of the Universe. They serve as standard candles, an important rung in the cosmic distance ladder.

Galaxies like NGC 4753 may not be rare, but the viewing angle plays a key role in identifying them. Our edge-on view of the galaxy makes its lenticular form clear. We could be seeing others like it from different angles that obscure its nature.

This is a model of NGC 4753, as seen from various viewing orientations. From left to right and top to bottom, the angle of the line of sight to the galaxy's equatorial plane ranges from 10° to 90° in steps of 10°. Although galaxies similar to NGC 4753 may not be rare, only certain viewing orientations allow for easy identification of a highly twisted disk. This infographic is a recreation of Figure 7 from a 1992 research paper.
This is a model of NGC
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Juno Reveals Secrets About Europa’s Icy Surface

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Europa has always held a fascination to me. I think it’s the concept of a world with a sub-surface ocean and the possibility of life that has inspired me and many others. In September 2022, NASAs Juno spacecraft made a flyby, coming within 355 kilometres of the surface. Since the encounter, scientists have been exploring the images and have identified regions where brine may have bubbled to the surface. Other images revealed possible, previously unidentified steep-walled depressions up to 50km wide, this could be caused by a free-floating ocean! 

Juno was launched to Jupiter on 5 August 2011. It took off from the Cape Canaveral site on board an Atlas V rocket and travelled around 3 billion kilometres. It arrived at Jupiter on 4 July 2016 and in September 2022 made its closest flyby of Europa. The frozen world is the second of the four Galilean satellites that were discovered by Galileo over 400 years ago. Visible in small telescopes, the true nature of the moon is only detectable by visiting craft like Juno. 

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Artist’s impression of NASA’s Galileo space probe in orbit of Jupiter. Credit: NASA

During its close fly-by, one of the onboard cameras known as Juno-Cam took the highest resolution images of the moon since Galileo took a flyby in 2000. The images supported the long held theory that the icy crusts at the north and south poles are not where they used to be. Another instrument on board, known as the Stellar Reference Unit (SRU), revealed possible activity resembling plumes where brine may have bubbled to the surface.

The ground track over Europa that was followed by Juno enabled imaging around the equatorial regions. The images revealed the usual, expected blocks of ice, walls, ridges and scarps but also found something else. Steep walled depressions that measured 20 to 50 kilometres across were also seen and they resembled large ovoid pits. 

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One of Juno’s enormous solar panels, unfurled on Earth. NASA/JPL. SWrI

The observations of the meanderings of the north/south polar ice and the varied surface features all point towards an outer icy shell that is free-floating upon the sub surface ocean. This can only happen if the outer shell is not connected to the rocky interior. When this happens, there are high levels of stress on the ice which then causes the fracture pattern witnessed. The images represent the first time such patterns have been seen in the southern hemisphere, the first evidence of true polar wandering.

The images from the SRU surprisingly provided the best quality images. It was originally designed to detect faint light from stars for navigation. Instead, the team used it to capture images when Europa was illuminated by the gentle glow of sunlight reflected from Jupiter. It was quite a novel approach and allowed complex features to become far more pronounced than before. Intricate networks of ridges criss-crossing the surface were identified along with dark stains from water plumes. One feature in particular stood out, nicknamed ‘the Platypus’, it was a 37 kilometre by 67 kilometre region shaped somewhat like a platypus.

Source : NASA’s Juno Provides High-Definition Views of Europa’s Icy Shell

The post Juno Reveals Secrets About Europa’s Icy Surface appeared first on Universe Today.

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