Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all
Catch Saturn at its biggest and brightest, and view its rings while you still can.
Right now, in Earth’s skies, Saturn appears at its biggest and brightest.
A view of tonight’s midnight sky from 45 N latitude, which shows the relative positions of bright Saturn and even brighter Jupiter in the southern part of the sky. They rise in the southeast just as the Sun sets, then migrate towards the west over the course of the night. They are joined by a variety of meteor showers, including the Delta Aquariids. (E. SIEGEL / STELLARIUM)
Just look to the southeastern skies (from the northern hemisphere), slightly east of bright Jupiter.
Every year, there’s one moment where Earth passes directly between the Sun and Saturn, occurring recently in the 2nd half of July. As captured by amateur astronomer Christian Gloor in 2019, this shows a view very close to what skywatchers will see through a telescope tonight, although the rings are slightly more edge-on this year than last year. (CHRISTIAN GLOOR / FLICKR)
With Earth between the Sun and Saturn, it’s poised for spectacular viewing.
The seven extraterrestrial planets of the solar system: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune. Photographed in 2019 with a Maksutov telescope from Mannheim and Stockach in Germany. The angular sizes and colors shown are accurate, but the brightnesses are not: Venus is some 63,000 times brighter than Neptune, or 12 astronomical magnitudes; the same difference as between the full Moon and a typical bright star like Vega or Capella. Saturn’s rings are incredibly prominent, and the only ringed system visible through a typical telescope. (GETTY IMAGES)
But the true star of Saturn is its main rings, now tilted for excellent views.
A computer simulated view of what Saturn looks like from Earth during opposition in every year from 2001 through 2029. Note the 15 year repeating pattern of where the rings are maximally tilted or edge-on to the Earth. Right now, in 2020, the rings are becoming closer to edge-on, which they will achieve in 2024. (TOM RUEN / PUBLIC DOMAIN)
Every 15 years, the rings cycle from edge-on to maximum tilt and back again.
Details of Saturn’s main, icy rings are visible in this sweeping view from Cassini of the planet’s glorious ring system. The total span, from the innermost A ring to the outer F ring shown here, covers approximately 40,800 miles (65,700 km) and was photographed on November 26, 2008. The outermost rings, including the ring created by Enceladus and the Phoebe ring beyond that, are not shown. (NASA/JPL/SPACE SCIENCE INSTITUTE)
Although they reach over 70,000 kilometers in extent, they’re only 30 kilometers thick.
This 1990s-era image from NASA’s Hubble Space Telescope shows Saturn in an unusual configuration: with its rings edge-on to us from our perspective. This occurs roughly every 15 years on a repeating basis, with the rings tilted at an angle the rest of the time. Saturn’s giant moon Titan can be seen at left (with its shadow falling on the planet), while smaller moons appear to the right. (ERICH KARKOSCHKA (UNIVERSITY OF ARIZONA LUNAR & PLANETARY LAB) AND NASA/ESA)
As a result, they briefly seemed to disappear in 1994, 2009, and will again in 2024.
From the vicinity of Saturn itself, NASA’s Cassini mission was able to capture the shadows cast by various ice crystals from within the rings, showing the incredible relief of the thin rings and their shadows against the main rings themselves. Saturn’s rings might extend for tens of thousands of kilometers in the radial dimension, but are only 30 km thick. (NASA/JPL/SPACE SCIENCE INSTITUTE)
NASA’s Cassini mission previously captured long shadows cast by nearly edge-on sunlight.
This 2018 image from NASA’s Hubble Space Telescope shows Saturn at opposition, with four of its moons visible and its rings shining brightly at nearly their maximum tilt with respect to our perspective. The banded structure of Saturn itself can also be seen, as can many of the gaps/divisions in the main ring system. (NASA, ESA, A. SIMON (GSFC) AND THE OPAL TEAM, AND J. DEPASQUALE (STSCI))
With no current Saturn orbiters, NASA’s Hubble provides our best views from afar.
Taken by the Cassini spacecraft with the Sun hidden behind Saturn, this backlit view of our Solar System’s great ringed world contains a bonus: a few pixels that reveal the Earth-Moon system. This is one of the most distant photographs of Earth ever taken, but it still reveals our world as larger than a single pixel. The rings themselves appear glorious, and are composed of 99.9% water ice. (NASA / JPL / SPACE SCIENCE INSTITUTE / CASSINI, BOXES BY E. SIEGEL)
The rings are 99.9% water ice, and are comparable in total mass to Saturn’s 7th largest moon: Mimas.
Saturn’s 7th largest moon, Mimas, appears to hover above the colorful rings. This image was taken by the Cassini spacecraft and, despite their enormous size differences, show two entities of comparable mass. Mimas is approximately twice the mass of the entirety of the ring system, despite the much larger apparent extent of the rings. (UNIVERSAL IMAGES GROUP VIA GETTY IMAGES)
Saturn’s rings are quickly evaporating; they’ll be gone in merely 300 million years.
This image of Saturn’s rings, with the planet itself behind them, was taken by Cassini at a distance of 725,000 km from the planet. Due to the fact that the ring system is “raining” down material onto Saturn, we can conclude that the rings will be entirely gone, based on the current rate of mass loss, in another 300 million years. (NASA/JPL-CALTECH/SPACE SCIENCE INSTITUTE)
The evidence possibly points to their origin arising from a recently destroyed moon.
Within Saturn’s rings, many small moons and moonlets, such as Daphnis, can be found. These objects are likely created by accreting particles, then destroyed by collisions and tidal forces. their uniform composition and decaying nature suggests that they were created relatively recently, with one longstanding theory contending that a larger, destroyed moon gave them their origin as little as tens but as many as hundreds of millions of years ago. (NASA / JPL-CALTECH / SPACE SCIENCE INSTITUTE)
Back when trilobites dominated the Earth, Saturn may not have had any rings at all.
The entirety of Saturn’s main rings, from the inner D ring to the outer F ring, may be much newer than the rest of the Solar System. It’s plausible that a few hundred million years ago, before the rise of the dinosaurs, these rings may not have existed at all. In another 300 million years ago, they likely will have disappeared entirely. (NASA/JPL)
Until another Saturn-bound mission launches, telescopes like Hubble will provide our sharpest views.
While the age of Saturn’s rings remains controversial, annual portraits from Hubble, such as this 2019 image, continue to shed insights on this fascinating giant planet. The changing north pole, in particular, can be seen by comparing the 2018, 2019, and 2020 images illustrated in this article. (NASA, ESA, A. SIMON (GSFC), M.H. WONG (UNIVERSITY OF CALIFORNIA, BERKELEY), AND THE OPAL TEAM)
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
MIT Scientist Jason Soderblom describes how the NASA mission will study the geology and composition of the surface of Jupiter’s water-rich moon and assess its astrobiological potential.
