title: Rogers Centre

text: Construction of the "Ontario Stadium Project" was spearheaded by lead contractor EllisDon. Several factors complicated the construction: The lands housed a functioning water pumping station that needed to be relocated, the soil was contaminated from a century of industrial use, railway buildings needed to be torn down or moved, and the site was rich with archaeological finds. One of the most complex issues was moving the John Street pumping station across the street to the south of the stadium. Foundations to the stadium were being poured even as the facility (in the infield area) continued to function, as construction on its new location had yet to be completed.


title: Rogers Centre

text: Because the stadium was the first of its kind in the world, the architects and engineers kept the design simple (by using a sturdy dome shape) and used proven technologies to move the roof. It was important the design would work and be reliable as to avoid the various problems that plagued Montreal's Olympic Stadium. The 31-storey-high roof consists of four panels: one (on the north end) is fixed in place and the other three are moved by electrically driven 'train' engines, that run on high-strength railway rails. The roof, which takes 20 minutes to open, was made out of steel trusses covered by corrugated steel cladding, which in turn is covered by a single-ply PVC membrane.


title: Rogers Centre

text: Because of its location south of the major railway corridor, new pedestrian connections had to be built; the infrastructure was part of the reason for the high cost of the stadium. The SkyWalk is an approximately enclosed walkway that leads from the base of the CN Tower and via a bridge connects to Union Station (and is part of the Path network). The John Street cable-stayed bridge was built to provide north–south passage over the rail tracks, linking Front Street with the stadium.


title: Rogers Centre

text: Construction at the site, which at one time was south of the shoreline, unearthed over 1,500 artifacts. These included a 200-year-old French cannon used as ballast for a ship, cannonballs, pottery and a telescope. The stadium was completed two months late, having been planned to open for the first regular season game of the 1989 Toronto Blue Jays season; the team played the first two months of their home schedule at Exhibition Stadium that year.


title: Rogers Centre

text: The official name prior to and during construction was the 'Ontario Stadium Project' but was widely referred to in local media as simply 'the Dome' or 'Toronto Domed' stadium. As completion neared the name "SkyDome" was chosen as part of a province-wide "name the stadium" contest in 1987. Sponsored by the "Toronto Sun", ballots were offered for people to submit their suggested name, with lifetime seats behind home plate to all events at the stadium (including concerts) as the prize. Over 150,000 entries were received with 12,897 different names. The selection committee narrowed it down to four choices: "Towerdome", "Harbourdome", "SkyDome", and simply "the Dome". The judges' final selection was SkyDome. Premier David Peterson drew the prize-winning entry of Kellie Watson from a lottery barrel containing the over-2,000 entries that proposed "SkyDome". At the press conference announcing the name, Chuck Magwood, president of the Stadium Corporation of Ontario (Stadco), the crown corporation created to run SkyDome, commented: "The sky is a huge part of the whole roof process. The name has a sense of the infinite and that's what this is all about." Kellie Watson received lifetime seating of choice at SkyDome, which is still honoured after the stadium was renamed to Rogers Centre, under new ownership.


title: Rogers Centre

text: The stadium officially opened on June 3, 1989, and hosted an official grand opening show: "The Opening of SkyDome: A Celebration", broadcast on CBC television the following evening hosted by Brian Williams. With a crowd of over 50,000 in attendance, the event included appearances by Alan Thicke, Oscar Peterson, Andrea Martin of "SCTV", impressionist André-Philippe Gagnon and rock band Glass Tiger. The roof was ceremonially "opened" by Ontario Premier David Peterson with a laser pen. The roof's opening exposed the crowd to a downpour of rain. Despite audible chants of "close the roof", Magwood insisted the roof remain fully open.


title: Rogers Centre

text: The stadium became a thorn in the side of David Peterson's Ontario Liberal government for repeated cost overruns. After the Liberals were defeated by the NDP in the 1990 Ontario election, a review by the new Bob Rae government in October 1990 revealed Stadco's debt meant the Dome would have to be booked 600 days a year to turn a profit, almost twice as many days as there are days in a calendar year. The stadium income was only $17 million in its first year of operations, while debt service was $40 million. It was determined the abrupt late inclusion by Stadco of a hotel and health club added an additional $112 million to the cost of the building.


title: Rogers Centre

text: As the province slipped into a recession, Rae appointed University of Toronto professor Bruce Kidd and Canadian Auto Workers President Bob White to the Stadco board to help deal with the stadium's growing debt, but the original $165 million debt had increased to $400 million by 1993. Stadco became a political liability, and in March 1994, the Ontario government paid off all outstanding Stadco debts from the government treasury and sold the stadium for $151 million to a private consortium that included Labatt Breweries, the Blue Jays' owner.


title: Rogers Centre

text: In November 1998, the stadium, which Labatt then owned as 49 percent of total, filed for bankruptcy protection, triggered after disastrous Skybox renewal numbers. Most of the 161 Skybox tenants had signed on for 10-year leases; a marked decrease in interest in the stadium's teams and the construction of the Air Canada Centre, which hosted the Toronto Maple Leafs and Toronto Raptors, resulted in few renewals for Skybox leases. That same month, the Blue Jays re-signed for an additional ten years in the facility.


title: Rogers Centre

text: In April 1999, Sportsco International LP bought the stadium out of bankruptcy protection for $80 million.


title: Rogers Centre

text: In November 2004, Rogers Communications, parent company of the Blue Jays, acquired SkyDome, excluding the attached SkyDome hotel, which had been sold to Renaissance for a reported $31 million in 1999, from Sportsco for about $25 million – roughly four percent of the cost of construction.


title: Rogers Centre

text: On February 2, 2005, Ted Rogers, President and CEO of Rogers Communications, announced a three-year corporate contract to change the name of SkyDome to Rogers Centre. The name change remains controversial and is unpopular with many fans, most of whom continue to refer to it as SkyDome in opposition to increased commercialism from the purchase of naming rights. One example is a 25,000-name petition started by TTC bus driver Randy Rajmoolie. A baseball diamond in Toronto's Trinity Bellwoods Park is named SkyDome after the stadium's former and popular name.


title: Rogers Centre

text: After the purchase Rogers refurbished the stadium by, among other things, replacing the Jumbotron with a Daktronics video display, and erecting other new monitors, including several built into the outfield wall. They also installed a new FieldTurf artificial playing surface.


title: Rogers Centre

text: In May 2005, the Toronto Argonauts agreed to three five-year leases at Rogers Centre, which could have seen the Argonauts play out of Rogers Centre up to and including 2019. The team had the option to leave at the end of each of the three lease agreements. Proposed plans to lock Rogers Centre into its baseball configuration permanently in order to install a natural grass surface forced the Argonauts to relocate to BMO Field before the 2016 season. However, it is now unclear whether the planned surface replacement and configuration change will take place, if at all, despite the Argonauts' departure.


title: Rogers Centre

text: In November 2005, Rogers Centre received a complete makeover to "open" the 100 Level concourse to the playing field and convert 43 luxury boxes to "party suites". This required some seats to be removed, which decreased overall capacity.


title: Rogers Centre

text: In April 2006, Rogers Centre became one of the first buildings of its size to adopt a completely smoke-free policy in Canada, anticipating an act of provincial legislature that required all Ontario public places to go smoke-free by June 1, 2006.


title: Rogers Centre

text: Alcohol was not available to patrons of Rogers Centre on April 7, 2009, as the Alcohol and Gaming Commission of Ontario imposed the first of a three-day alcohol suspension at the stadium for "infractions (that) took place at certain past events", according to the press release.


title: Rogers Centre

text: Rogers Communications and Brookfield Asset Management have reportedly discussed replacing Rogers Centre with a smaller, baseball-specific stadium plus residential towers, office buildings, retail stores and public space. The new venue would be constructed on the southern end of the current stadium and adjacent parking lots, while the mixed-use development would be built on the northern portion of the site. An alternate site has also been considered for a new baseball park, at Quayside in Toronto's east end next to Lake Ontario. In July 2022, the Blue Jays announced that they had opted to undertake a major two-phased renovation of the stadium to extend its lifespan, but still intended to pursue a new stadium or rebuild of the Rogers Centre within 10 to 12 years.


title: Rogers Centre

text: The venue was the first major team sports stadium in North America with a functional, fully retractable roof (Montreal's Olympic Stadium also had a retractable roof, but due to operational issues, it was replaced with a permanent roof). The roof is composed of four panels and covers an area of . The two middle panels slide laterally to stack over the north semi-circular panel, and then the south semi-circular panel rotates around the stadium and nests inside the stack. It takes 20 minutes for the roof to open or close. It is not possible to move the roof in cold weather because the mechanism that closes the roof could fail in cooler weather.


title: Rogers Centre

text: The original AstroTurf installation was replaced with FieldTurf from 2005 to 2010. The FieldTurf took about 40 hours to remove for events such as concerts or trade shows, as it used 1,400 trays that needed to be stacked and transported off the field. Prior to the 2010 baseball season, to reduce the amount of time required to convert the playing field, a new, roll-based version of AstroTurf was installed. Similar to FieldTurf, the installation uses a sand- and rubber-based infill within the synthetic fibres. Rogers Centre is one of five venues in Major League Baseball that use artificial turf (the others are Tropicana Field in St. Petersburg, Florida, LoanDepot Park in Miami, Globe Life Field in Arlington, Texas, and Chase Field in Phoenix, Arizona) and was the last venue to use "sliding pits" before switching to a full dirt infield for the 2016 baseball season. Before the Argonauts moved out, the pitcher's mound could be lowered or raised hydraulically when converting from baseball to football (or vice versa).


title: Rogers Centre

text: The use of natural grass was long thought to be unfeasible since the stadium was designed as a closed structure with a roof that opens, and as such, the interior was not intended or built to deal with weather, including low temperatures and drainage. As of the 2020 season, they are one of two teams to have never played a home game on grass at their main stadium (the Tampa Bay Rays played some home games in 2007 and 2008 at Champion Stadium in Walt Disney World in Bay Lake, Florida, and during the 2020 and much of the 2021 seasons, due to the COVID-19 pandemic, the Toronto Blue Jays were playing most of their home games at their AAA affiliate's home stadium of Sahlen Field in Buffalo, New York with the Blue Jays also playing home games in TD Ballpark in Dunedin, Florida, during the first two months of the 2021 season).


title: Rogers Centre

text: However, the Blue Jays have long explored the possibility of converting the Rogers Centre to a natural grass surface, and plans were examined in order to install a grass field by 2018 to allow enough time for research and growing of the sod. Installing grass would require digging up the floor, adding a drainage system, and installing of dirt. The stadium would need to be permanently locked into its baseball configuration; the lower stands, which roll into position for football, would be permanently fixed in position for baseball. The plan became more definite when Rogers renewed the Argonauts' lease through 2017, but ruled out any further extensions; in May 2015, it was announced the Argos would move to BMO Field for the 2016 season. The Blue Jays subsequently confirmed the Argonauts' early departure would not accelerate their own plans to install grass in 2018, though it did allow for a dirt infield to be installed for the 2016 season. However, it does not appear likely the field will be converted to natural grass, as no further announcements for replacing the surface have been made since, and the field continues to retain its artificial surface.


title: Rogers Centre

text: There are a total of 5,700 club seats and 161 luxury suites at the Rogers Centre. The complex had a Hard Rock Café restaurant until December 2009 when the restaurant closed after its lease expired. The Toronto Marriott City Centre Hotel is also within Rogers Centre with 70 rooms, and a restaurant and bar called the Sportsnet Grill overlooks the field. The Blue Jays in partnership with theScore Bet announced plans in April 2022 to create a new premium branded flagship sports bar and restaurant that would be open 365 days a year at the Rogers Centre.


title: Rogers Centre

text: The Rogers Centre video board is high and across. The panel is made up of modular LED units that can be replaced unit by unit, and can be repaired immediately should it be damaged during an event. Originally, this screen was a Sony Jumbotron, which was the largest in North America at the time of the stadium's opening, but it has since been replaced a few times. There are also two ribbon boards made up of LED that run along the East and West sides of the stadium interior. Each board is long by high. In addition, there are two video boards that make up parts of the left and right outfield walls while the stadium is in baseball configuration. These are wide by nearly high.


title: Rogers Centre

text: The main video board was upgraded again for the 2022 season, this time by using more modern technology and adding four "wings", two on each side of the central part of the main video board with the lower wings on each side being wider, making the main video board no longer rectangular. This was to accommodate the windows of the hotel behind the main video board.


title: Rogers Centre

text: The video board and the stadium played host to several serial television events, including the series finales for "Cheers" and "", along with live coverage of the funeral of Princess Diana in 1997.


title: Rogers Centre

text: The Blue Jays have won two World Series championships at Rogers Centre, hosting Games 3, 4, and 5 of the 1992 World Series and Games 1, 2, and 6 of the 1993 World Series at the stadium, then known as SkyDome, with Game 3 of the 1992 series the first World Series game ever played in Canada. The stadium also hosted the 1991 Major League Baseball All-Star Game. The 1991 American League Championship Series was the first Major League Baseball playoff series played entirely indoors with the first two games at the Metrodome in Minneapolis and the final three at SkyDome.


title: Rogers Centre

text: Besides baseball, Rogers Centre was the original home of the National Basketball Association's Toronto Raptors, who played at the venue from November 1995 to February 1999, while the Air Canada Centre (later renamed Scotiabank Arena) was being planned and built. It proved to be somewhat problematic as a basketball venue, even considering it was only a temporary facility. For instance, many seats that were theoretically in line with the court were so far away fans needed binoculars to see the action. Other seats were so badly obstructed that fans sitting there could only watch the game on the replay boards. For most games, Rogers Centre seated 22,900 people. However, the Raptors sometimes opened the 500 Level, which is the stadium's uppermost level, when popular opponents came to town, such as the Chicago Bulls when Michael Jordan was a member of the team, expanding capacity to 29,000 and held over 36,000 attendees at one point.


title: Rogers Centre

text: Rogers Centre hosted Canadian football from opening in 1989 to 2015, as the Argonauts moved to BMO Field in 2016. In November 2007, it hosted the 95th Grey Cup, its first since 1992 and third all-time. It was the 56th Grey Cup hosted by the city of Toronto since the championship's inception in 1909.


title: Rogers Centre

text: From 1989 to 2003, SkyDome hosted the Vanier Cup championship of Canadian Interuniversity Sport (later renamed U Sports in 2016) football.


title: Rogers Centre

text: In 1994, then-part owner of SkyDome Labatt considered purchasing a National Football League and a Major League Soccer team to play at the stadium.


title: Rogers Centre

text: The International Bowl, a NCAA college football game between two American schools – one from the Big East Conference and one from the Mid-American Conference – has been played at Rogers Centre four times. The Big East school has won all four bowl games. On January 6, 2007, the University of Cincinnati Bearcats defeated the Western Michigan University Broncos, 27–24. The Scarlet Knights of Rutgers University won the second bowl game in the series on January 5, 2008, by beating the Cardinals of Ball State University, 52–30. The Bulls of the University at Buffalo, a school within a ninety-minute drive of Rogers Centre, lost the third International Bowl to the University of Connecticut Huskies, 38–20. On January 2, 2010, the University of South Florida Bulls beat the Huskies of Northern Illinois University, 27–3.


title: Rogers Centre

text: Rogers Centre was also the venue for the 43rd Vanier Cup on Friday, November 23, 2007, just two days before Grey Cup Sunday. It was the 16th Vanier Cup hosted at the venue, returning after a three-year absence in which it was hosted by Hamilton, Ontario (2004 and 2005) and Saskatoon, Saskatchewan (2006). It was the 40th Vanier Cup hosted by Toronto since that championship's inception in 1965.


title: Rogers Centre

text: The National Football League's Buffalo Bills announced its intentions to play five "home" games (and three pre-season games) in Rogers Centre in October 2007, so beginning the Bills Toronto Series; the first of these regular-season games took place on December 7 of the 2008 NFL season versus the Miami Dolphins. It marked the first time an NFL team has established a "home" stadium outside the United States for regular-season games. The Bills played a preseason game against the Pittsburgh Steelers at Rogers Centre on August 14, 2008; the Toronto Series was played every year through the 2013 season.


title: Rogers Centre

text: From the mid-2000s, soccer matches have been regularly held in SkyDome/Rogers Centre; they had been rarely played at the venue when its AstroTurf surface had been in place.


title: Rogers Centre

text: On June 8, 2005, an international soccer friendly between Serbia and Montenegro and Italy took place, ending in a 1–1 draw.


title: Rogers Centre

text: On May 25, 2010, the stadium hosted a friendly soccer match between Italy's ACF Fiorentina and Juventus F.C. with Fiorentina winning 1–0.


title: Rogers Centre

text: On July 16, 2010, the stadium hosted a friendly soccer match between England's Manchester United F.C. and Scotland's Celtic F.C. Manchester United F.C. defeated Celtic F.C. with a score of 3–1. The match was played on a temporary grass surface harvested from Burford, Ontario and transported via 18 tractor-trailers.


title: Rogers Centre

text: On July 21, 2012, the stadium hosted the friendly between Toronto FC and Liverpool F.C., a match that finished in a 1–1 draw.


title: Rogers Centre

text: On November 19, 2013, Rogers Centre hosted a friendly soccer match between Brazil and Chile, a match that finished in a 2–1 victory for the Brazilian side.


title: Rogers Centre

text: Having originated in 1980 at Exhibition Stadium, the Toronto Supercross moved to the Rogers Centre upon its opening in 1989. The event was held annually through 1996 before going on hiatus. It was revived as a part of the FIM World Supercross GP series in 2004 and joined the AMA Supercross Championship after the two series fully merged in 2008. The event ran until 2014 and returned for 2016 and 2017.


title: Rogers Centre

text: On January 16, 1993, the stadium hosted the Skydome Grand Prix featuring the USAC National Midget Car Series. The night of racing featured NASCAR stars John Andretti, Kenny Irwin Jr., Tony Stewart and Indianapolis 500 winner Tom Sneva racing on a 1/6 mile oval track and was broadcast across Canada on TSN.


title: Rogers Centre

text: Rogers Centre has also hosted exhibition cricket, gaelic football, hurling, Australian rules football and tennis.


title: Rogers Centre

text: On May 31, 1997, the venue hosted a post-Olympic track and field event that pitted Olympic track champions Donovan Bailey and Michael Johnson, in a 150 m race billed as a competition for the title of the "World's Fastest Man". Bailey won the race, completing it in a time of 15 seconds and winning the $1.5 million prize. Johnson pulled up lame at the 110 m mark claiming a quadriceps injury.


title: Rogers Centre

text: Rogers Centre is the site of several major high school and collegiate sporting competitions, such as the Prentice Cup for baseball. Since 2008, the Rogers Centre is the host of the Greater Toronto high schools' Metro Bowl.


title: Rogers Centre

text: On April 30, 2011, UFC 129 was hosted at Rogers Centre, in the first major mixed martial arts event to ever be held in Ontario after the province lifted a ban on prizefighting. Due to overwhelming demand for tickets (with the initial slate of 42,000 selling in around half an hour), the UFC and Rogers Centre reconfigured the event for 55,000 tickets. The event broke a UFC attendance record set at UFC 124 in Montreal, and also set records for the largest single-day gate revenue in both UFC (surpassing UFC 66 by at least double) and Rogers Centre history.


title: Rogers Centre

text: WWE has hosted WrestleMania at Rogers Centre twice. WrestleMania VI was held on April 1, 1990, with the main event being a title vs title match which saw the WWF Intercontinental Champion The Ultimate Warrior defeat the WWF World Heavyweight Champion Hulk Hogan, set the SkyDome attendance record of 67,678. The attendance record was broken when 68,237 attended Wrestlemania X8 on March 17, 2002, the main event seeing Triple H win the WWF Undisputed Championship against Canadian Chris Jericho.


title: Rogers Centre

text: In February 1999, the stadium hosted a taping for the February 13, 1999, episode of "Raw" (a special Saturday-night airing of "Raw" due to USA Network's coverage of the Westminster Kennel Club Dog Show), featuring Stone Cold Steve Austin being defeated by Mr. McMahon in a gauntlet match against The Corporation. It had the largest crowd in "Raw" history, with a reported attendance of 41,432.


title: Rogers Centre

text: The stadium has several concert configurations, including smaller "Theatre" (capacity 5,000 to 7,000) and "Concert Hall" (formerly "SkyTent"; capacity 10,000 to 25,000). Due to the stadium's design and building materials, the acoustics are poor, and the loudness/quality can vary greatly around the stadium. Its popularity with artists and fans has diminished over the years, and the Scotiabank Arena now hosts most major concerts. The SkyTent, a group of acoustical curtain sails hoisted on rigging above the floor, helps reduce sound distortion and improve sound quality by dampening reverberations around the stadium.


title: Rogers Centre

text: Soon after its opening, the stadium became a popular venue for large-scale rock concerts and is the largest indoor concert venue in Toronto. Artists have included Bruce Springsteen, U2 with two concerts in 2009, as well as their concert in 2011, all part of their 360° Tour. Bon Jovi performed two sellout shows on July 20 and 21, 2010, at Rogers Centre as part of The Circle Tour. Bruce Springsteen performed on August 24, 2012, during his Wrecking Ball World Tour in front of 39,000 attendees.


title: Rogers Centre

text: The Rolling Stones played two sold-out concerts at the stadium: on December 4, 1989, during the Steel Wheels Tour and on September 26, 2005, during their highest-grossing tour A Bigger Bang Tour. Rogers Centre has been a venue for large electronic dance music events. During 2013, the stadium hosted two electronic dance music events, including two sold-our shows on Swedish House Mafia's One Last Tour, and Sensation.


title: Rogers Centre

text: One of the more notable concerts, as shown in the documentary "", was Madonna's 1990 Blond Ambition World Tour show. The touring show had become extremely controversial, due to the risqué visuals and performances. When the concert arrived in Toronto, police were alerted the show might violate local obscenity laws. The police were on site for the concert and threatened charges without changes. The show went on as planned, however, without any legal action taken. Later, she performed two concerts at the stadium again during The Girlie Show World Tour in 1993.


title: Rogers Centre

text: Guns N' Roses performed at Rogers Centre on July 16, 2016, during their Not in This Lifetime... Tour in front of 48,016 attendees with Billy Talent. Metallica also played a sold-out show at the stadium as part of their WorldWired Tour on July 16, 2017, with special guests Avenged Sevenfold and Volbeat. Shawn Mendes headlined his first stadium show to a sold-out crowd on September 6, 2019, at Rogers Centre during his .


title: Rogers Centre

text: It is home to several annual auto shows, with the Canadian International AutoShow in February and Importfest in October.


title: Rogers Centre

text: The Opening Ceremonies of the XVI International AIDS Conference were held at Rogers Centre on August 13, 2006.


title: Rogers Centre

text: It has also hosted many public speakers, including appearances by the Dalai Lama, Christian evangelist Billy Graham, Nelson Mandela, and for a book reading with J. K. Rowling and Margaret Atwood.


title: Rogers Centre

text: In addition to being a venue that hosts sports, concerts and other events, the Rogers Centre also houses the head offices of a number of businesses. The Toronto Blue Jays have its office headquarters in the building and until 2008, the Toronto Argonauts did as well. It is also the home of the head offices of Ticketmaster Canada and Zuffa Canada, the former also having the main Ticketmaster outlet (ticket centre) for eastern Canada, at the south end of the building beside Gate 9.


title: Rogers Centre

text: In addition, the building contains the Toronto Renaissance Hotel, a Premier Fitness/Health Club, a Rogers Plus store, (formerly) a Hard Rock Cafe (now John Street Terrace), and (formerly) Windows Restaurant (now WestJet Flight Deck). Starting in 2006, the Hard Rock Cafe only opened when there was a performance in the building, and closed altogether in 2009. On non-event days, there are daily tours of the Rogers Centre.


title: Rogers Centre

text: The stadium is the setting of the climax in the 2022 Pixar animated film "Turning Red", in which the fictional boy band 4*Town performs a large-scale concert during which the stadium is partially destroyed. As the Toronto-set film's time period is set in 2002, the stadium is referred to by its original SkyDome name.


title: Kevin Nealon

text: Kevin Nealon (; born November 18, 1953) is an American comedian and actor. He was a cast member on "Saturday Night Live" from 1986 to 1995, acted in several of the Happy Madison films, played Doug Wilson on the Showtime series "Weeds", and provided the voice of the title character, Glenn Martin, on "Glenn Martin, DDS".


title: Kevin Nealon

text: Nealon was born on November 18, 1953, in St. Louis, Missouri, one of five children of Kathleen M. (née Kimball; 1928–2020) and Emmett F. Nealon (1925–2018), an aircraft company executive. A few months after he was born, the family moved to Bridgeport, Connecticut; when he was six, they moved to Germany for four years. He is of Irish descent and was raised Catholic. He graduated from St. Joseph High School in Trumbull, Connecticut, in 1971 and earned a bachelor's degree in marketing from Sacred Heart University. He then took night courses at Fairfield University, where he played quarterback on the football team.


title: Kevin Nealon

text: Nealon played guitar in bands during high school and gravitated to comedy in college. In 1977, he moved to San Diego and then to Los Angeles, where he learned his craft at the Improv while tending bar there for a living. He had been doing stand-up for six years when he made his network television debut on "The Tonight Show Starring Johnny Carson" in 1984. He later became a regular there and on "Late Night with David Letterman".


title: Kevin Nealon

text: In 1986, "Saturday Night Live" recruited his friend Dana Carvey, and Carvey, in turn, recommended Nealon. Both joined the cast that year, and Nealon became a full-time performer in the 1987–1988 season, and remained for nine seasons. Nealon's "SNL" characters include Mr. Subliminal (which also became known as the "Subliminal Editorial" when Nealon was promoted to "Weekend Update" anchorman), Frank Gannon, P.I.P.I. (for Politically Incorrect Private Investigator), Bob Waltman (a male Barbara Walters), and Franz (of Hans and Franz) along with Carvey. He also anchored "Weekend Update" from 1991 to 1994. He stayed on "SNL" for one more season and left in 1995, after a then-record nine seasons. (His record was later surpassed by Tim Meadows, Darrell Hammond, and Kenan Thompson.)


title: Kevin Nealon

text: In 1991, he had his first major film role, as boyfriend Tony Boer in "All I Want for Christmas". Other films in which he has since appeared include "Happy Gilmore", "The Wedding Singer", "Anger Management", "Little Nicky", "Just Go with It", "Daddy Day Care", "Good Boy!", and "Aliens in the Attic" (2009). He has a part in many of Adam Sandler's Happy Madison films, including "Grandma's Boy" (2006), "You Don't Mess with the Zohan" (2008), and "Father of the Year" (2018), and made a cameo appearance in the 2008 film "Get Smart".


title: Kevin Nealon

text: In the mid-1990s, Nealon played himself in three episodes of "The Larry Sanders Show". The most popular episode was titled "The New Writer" when he starts hanging around the office so much that Hank (played by actor Jeffrey Tambor) is worried Nealon is trying to steal his job. Garry Shandling and Nealon had a close relationship. In 1994, Nealon hosted the 13-part series "Amazing America" on the Discovery Channel.


title: Kevin Nealon

text: Nealon had a recurring television role on the 2002–06 CBS comedy "Still Standing" playing Ted Halverson, the Millers' competitive and religious neighbor. He also appeared as a patient in a mental institution on the first season of "Monk". Nealon played Dr. Mark Crest in "Deja Vu", an episode of "The Outer Limits" television show. It first aired on 9 July 1999, during the fifth season. From 2005 to 2012, Nealon had an ongoing supporting role as Doug Wilson on the show "Weeds" on Showtime. In 2009–2011 he voiced the title character in Nick at Nite's animated series "Glenn Martin, DDS".


title: Kevin Nealon

text: In 2002, he hosted "The Conspiracy Zone" on The New TNN for 26 episodes plus an unaired pilot. In 2004, he hosted the first season of "Poker Royale" on the Game Show Network. Nealon also hosted several years of "World's Funniest Commercials" specials on TBS in the 2000s.


title: Kevin Nealon

text: In 2008, he published a book chronicling his experiences during his wife's pregnancy, "Yes, You're Pregnant, But What About Me?".


title: Kevin Nealon

text: Starting in 2015, Nealon portrayed Captain Telstar in commercials for Charter Spectrum. From 2016 to 2020, he was a regular on the TV sitcom "Man with a Plan", and since 2017 he has also hosted a YouTube show called "Hiking with Kevin".


title: Kevin Nealon

text: Nealon was dating Jan Hooks when they were both hired by "Saturday Night Live". In 1989 he married Linda Dupree, a model and stuntwoman; they divorced in 2002. During this time, Nealon, who has been a vegan since 1989, became active in the animal rights movement; he has supported PETA, the Amanda Foundation, Farm Sanctuary, the Washington Wildlife Alliance, The Ark Trust's Genesis Awards, and also Meat Out.


title: Kevin Nealon

text: On September 3, 2005, he married Susan Yeagley in Bellagio, Lombardy, Italy. They have a son, Gable, born in 2007. They reside in Pacific Palisades, Los Angeles.


title: Kevin Nealon

text: On February 22, 2006, Nealon contributed an opinion article to "The New York Times" about having his phone tapped and his police records searched by Hollywood private investigator Anthony Pellicano, who was later convicted of crimes including racketeering and illegal wiretapping. It was also revealed in a separate court case later the same month that investigators working for the Ringling Bros. and Barnum & Bailey Circus may also have targeted Nealon for wiretapping in connection with his work for PETA. Nealon holds dual Irish and American citizenship.


title: Kevin Nealon

text: Nealon is a fixture on the European melodic rock scene both as a fan, and as a benefactor; in 2019 he used his fame to organize a benefit for close friend and ailing rocker Tony Mills. All proceeds from the festival went towards Mills' medical expenses.


title: Kevin Nealon

text: On May 15, 2022, Nealon was awarded a Doctorate of Humane Letters, Honoris Causa, by his alma mater, Sacred Heart University. Nealon also served as the convocation speaker for the graduating class of 2022.


title: Takbir

text: The Takbir (, , "magnification [of God]") is the name for the Arabic phrase "" (, ), meaning "God is the greatest".


title: Takbir

text: It is a common Arabic expression, used in various contexts by Muslims and Arabs around the world: in formal Salah (prayer), in the Adhan (Islamic call to prayer), in Hajj, as an informal expression of faith, in times of distress or joy, or to express resolute determination or defiance. The phrase is also used by Arab Christians.


title: Takbir

text: The Arabic word () means "great" from the Semitic root '. The Arabic word () is the elative form ("greatest") of the adjective "kabīr". When used in the it is usually translated as "greatest", but some authors translate it as "greater". The term ' itself is the stem II verbal noun of the triliteral root ', meaning "great", from which "akbar" "greater" is derived. The form ' is the nominative of "Allah", meaning 'God'.


title: Takbir

text: This phrase is recited by Muslims in many different situations. For example, when they are very happy, to express approval, to prevent a Muslim from becoming prideful by reminding them that Allah is their source of success, as a battle cry, or during times of extreme stress. The phrase is not found in the Quran, which does not describe God as "akbar", but uses the name "al-Kabīr" "The Great" or "Kabīr" "Great", commonly translated as "Most Great" (13:9, 31:30, 22:62, 34:23, 40:12, 4:34).


title: Takbir

text: The phrase is said during each stage of both salah (obligatory prayers, performed five times a day), and nafl (supererogatory prayers, performed at will). The call to prayer by the "muezzin" to those outside the mosque ("adhan") and the call to those inside to line up for the commencement of prayer ("iqama") also contain the phrase.


title: Takbir

text: The phrase is used after the birth of a child as a means of praising God. It is also part Islamic funeral and burial customs.


title: Takbir

text: During the festival of Eid al-Adha and the days preceding it, Muslims recite the Takbīr. This is particularly the case on the Day of Arafah.


title: Takbir

text: The process of pronouncing the name of Allah while performing Dhabihah one must say "Bismillah Allahu Akbar".


title: Takbir

text: The expression "Allah Akbar" can be used in a variety of situations, from celebrations to times of grief.


title: Takbir

text: In a historical account by someone who was present both at the birth of Abd Allah ibn al-Zubayr and at his funeral, the author observes that "Allahu Akbar" was said on both occasions.


title: Takbir

text: Just before Garuda Indonesia Flight 152 crashed into the jungle near Medan, Indonesia, the pilot screamed "Aaaaaaah! "Allāhu akbar"" into his radio. According to a radio communication transcript, the pilot's conversation with the air controller had been in English, but his last words as the plane crashed were the takbir.


title: Takbir

text: The takbir can be used to express joy or surprise. It is also used as applause in religious contexts, such as after a Quran recital, as other forms of applause are considered less appropriate.


title: Takbir

text: When Reshma Begum was discovered alive 17 days after the 2013 Savar building collapse in Bangladesh which killed 1129 people, crowds jubilantly cried ""Allāhu akbar"" to express their joy and gratitude that she had survived.


title: Takbir

text: As a multi-purpose phrase, it is sometimes used by Arab football commentators as an expression of amazement, or even as a football chant.


title: Takbir

text: Historically, the takbir has been used as a cry of victory. Ibn Ishaq's Life of Mohammed narrates at least two incidents in which it was so used.


title: Takbir

text: "When the apostle raided a people he waited until the morning. If he heard a call to prayer he held back; if he did not hear it he attacked. We came to Khaybar by night, and the apostle passed the night there; and when morning came he did not hear the call to prayer, so he rode and we rode with him, and I rode behind Abu Talha with my foot touching the apostle's foot. We met the workers of Khaybar coming out in the morning with their spades and baskets. When they saw the apostle and the army they cried, 'Muhammad with his force,' and turned tail and fled. The apostle said, 'Allah akbar! Khaybar is destroyed. When we arrive in a people's square it is a bad morning for those who have been warned.'" (page 511) "So he got off his horse and came at him and 'Ali advanced with his shield. 'Amr aimed a blow which cut deeply into the shield so that the sword stuck in it and struck his head. But 'Ali gave him a blow on the vein at the base of the neck and he fell to the ground. The dust rose and the apostle heard the cry, 'Allah Akbar' and knew that 'Ali had killed him." (page 456)


title: Takbir

text: During the Iranian Revolution of 1979, it was shouted from rooftops in Iran during the evenings as a form of protest. This practice returned in the 2009 Iranian presidential election protests, which protested the election results.


title: Takbir

text: The phrase has sometimes been used as a battle cry by Muslim extremists. This usage has been denounced by other Muslims.


title: Takbir

text: Professor Khaled A. Beydoun writes that the association of the phrase "Allah Akbar" with terrorism has been exacerbated by mass media and television pundits. He points out that fictional films and shows also utilize it as a cinematic trope further cementing the association.


title: Takbir

text: The phrase is also used by Arabic-speaking Christians, "God" being translated "Allah" in Arabic. The phrase is used in liturgical contexts among Palestinian Orthodox Christians, and its use has been defended by Theodosios, the Palestinian Orthodox Archbishop of Sebastia.


title: Takbir

text: The Afghan constitution that came into force on January 4, 2004, required that "Allāhu akbar" be inscribed on the Flag of the Islamic Republic of Afghanistan. Afghanistan came under Taliban control following the 2021 offensive, and the Islamic Republic collapsed.


title: Takbir

text: The phrase "Allāhu akbar" is written on the flag of Iran, as called for by Article 18 of the Constitution of the Islamic Republic of Iran. The phrase appears 22 times on the flag, written on the borders of the central white stripe.


title: Takbir

text: During the Gulf War in January 1991, Saddam Hussein held a meeting with top military commanders, where it was decided to add the words "Allāhu akbar" (described as the Islamic battle cry) to Iraq's flag to boost his secular regime's religious credentials, casting himself as the leader of an Islamic army. Hussein described the flag as "the banner of jihad and monotheism".


title: Takbir

text: In 2004, the US-picked Iraqi Governing Council approved a new flag for Iraq that abandoned symbols of Hussein's regime, such as the words "Allāhu akbar". In January 2008, however, Iraq's parliament passed a law to change the flag by leaving in the phrase, but changing the calligraphy of the words "Allāhu akbar", which had been a copy of Hussein's handwriting, to a Kufic script. The Iraqi flag under Hussein had each of the two words of the phrase written in one of the spaces between the stars on the central band; the 2008 flag, while leaving the phrase in, removes the stars.


title: Gaussian elimination

text: In mathematics, Gaussian elimination, also known as row reduction, is an algorithm for solving systems of linear equations. It consists of a sequence of operations performed on the corresponding matrix of coefficients. This method can also be used to compute the rank of a matrix, the determinant of a square matrix, and the inverse of an invertible matrix. The method is named after Carl Friedrich Gauss (1777–1855) although some special cases of the method—albeit presented without proof—were known to Chinese mathematicians as early as circa 179 AD.


title: Gaussian elimination

text: To perform row reduction on a matrix, one uses a sequence of elementary row operations to modify the matrix until the lower left-hand corner of the matrix is filled with zeros, as much as possible. There are three types of elementary row operations:


title: Gaussian elimination

text: Using these operations, a matrix can always be transformed into an upper triangular matrix, and in fact one that is in row echelon form. Once all of the leading coefficients (the leftmost nonzero entry in each row) are 1, and every column containing a leading coefficient has zeros elsewhere, the matrix is said to be in reduced row echelon form. This final form is unique; in other words, it is independent of the sequence of row operations used. For example, in the following sequence of row operations (where two elementary operations on different rows are done at the first and third steps), the third and fourth matrices are the ones in row echelon form, and the final matrix is the unique reduced row echelon form.


title: Gaussian elimination

text: Using row operations to convert a matrix into reduced row echelon form is sometimes called Gauss–Jordan elimination. In this case, the term "Gaussian elimination" refers to the process until it has reached its upper triangular, or (unreduced) row echelon form. For computational reasons, when solving systems of linear equations, it is sometimes preferable to stop row operations before the matrix is completely reduced.


title: Gaussian elimination

text: The process of row reduction makes use of elementary row operations, and can be divided into two parts. The first part (sometimes called forward elimination) reduces a given system to "row echelon form", from which one can tell whether there are no solutions, a unique solution, or infinitely many solutions. The second part (sometimes called back substitution) continues to use row operations until the solution is found; in other words, it puts the matrix into "reduced" row echelon form.


title: Gaussian elimination

text: Another point of view, which turns out to be very useful to analyze the algorithm, is that row reduction produces a matrix decomposition of the original matrix. The elementary row operations may be viewed as the multiplication on the left of the original matrix by elementary matrices. Alternatively, a sequence of elementary operations that reduces a single row may be viewed as multiplication by a Frobenius matrix. Then the first part of the algorithm computes an LU decomposition, while the second part writes the original matrix as the product of a uniquely determined invertible matrix and a uniquely determined reduced row echelon matrix.


title: Gaussian elimination

text: If the matrix is associated to a system of linear equations, then these operations do not change the solution set. Therefore, if one's goal is to solve a system of linear equations, then using these row operations could make the problem easier.


title: Gaussian elimination

text: For each row in a matrix, if the row does not consist of only zeros, then the leftmost nonzero entry is called the "leading coefficient" (or "pivot") of that row. So if two leading coefficients are in the same column, then a row operation of type 3 could be used to make one of those coefficients zero. Then by using the row swapping operation, one can always order the rows so that for every non-zero row, the leading coefficient is to the right of the leading coefficient of the row above. If this is the case, then matrix is said to be in row echelon form. So the lower left part of the matrix contains only zeros, and all of the zero rows are below the non-zero rows. The word "echelon" is used here because one can roughly think of the rows being ranked by their size, with the largest being at the top and the smallest being at the bottom.


title: Gaussian elimination

text: For example, the following matrix is in row echelon form, and its leading coefficients are shown in red:


title: Gaussian elimination

text: It is in echelon form because the zero row is at the bottom, and the leading coefficient of the second row (in the third column), is to the right of the leading coefficient of the first row (in the second column).


title: Gaussian elimination

text: A matrix is said to be in reduced row echelon form if furthermore all of the leading coefficients are equal to 1 (which can be achieved by using the elementary row operation of type 2), and in every column containing a leading coefficient, all of the other entries in that column are zero (which can be achieved by using elementary row operations of type 3).


title: Gaussian elimination

text: Suppose the goal is to find and describe the set of solutions to the following system of linear equations:


title: Gaussian elimination

text: The table below is the row reduction process applied simultaneously to the system of equations and its associated augmented matrix. In practice, one does not usually deal with the systems in terms of equations, but instead makes use of the augmented matrix, which is more suitable for computer manipulations. The row reduction procedure may be summarized as follows: eliminate from all equations below , and then eliminate from all equations below . This will put the system into triangular form. Then, using back-substitution, each unknown can be solved for.


title: Gaussian elimination

text: The second column describes which row operations have just been performed. So for the first step, the is eliminated from by adding to . Next, is eliminated from by adding to . These row operations are labelled in the table as


title: Gaussian elimination

text: Once is also eliminated from the third row, the result is a system of linear equations in triangular form, and so the first part of the algorithm is complete. From a computational point of view, it is faster to solve the variables in reverse order, a process known as back-substitution. One sees the solution is , , and . So there is a unique solution to the original system of equations.


title: Gaussian elimination

text: Instead of stopping once the matrix is in echelon form, one could continue until the matrix is in "reduced" row echelon form, as it is done in the table. The process of row reducing until the matrix is reduced is sometimes referred to as Gauss–Jordan elimination, to distinguish it from stopping after reaching echelon form.


title: Gaussian elimination

text: The method of Gaussian elimination appears – albeit without proof – in the Chinese mathematical text Chapter Eight: "Rectangular Arrays" of "The Nine Chapters on the Mathematical Art". Its use is illustrated in eighteen problems, with two to five equations. The first reference to the book by this title is dated to 179 AD, but parts of it were written as early as approximately 150 BC. It was commented on by Liu Hui in the 3rd century.


title: Gaussian elimination

text: The method in Europe stems from the notes of Isaac Newton. In 1670, he wrote that all the algebra books known to him lacked a lesson for solving simultaneous equations, which Newton then supplied. Cambridge University eventually published the notes as "Arithmetica Universalis" in 1707 long after Newton had left academic life. The notes were widely imitated, which made (what is now called) Gaussian elimination a standard lesson in algebra textbooks by the end of the 18th century. Carl Friedrich Gauss in 1810 devised a notation for symmetric elimination that was adopted in the 19th century by professional hand computers to solve the normal equations of least-squares problems. The algorithm that is taught in high school was named for Gauss only in the 1950s as a result of confusion over the history of the subject.


title: Gaussian elimination

text: Some authors use the term "Gaussian elimination" to refer only to the procedure until the matrix is in echelon form, and use the term Gauss–Jordan elimination to refer to the procedure which ends in reduced echelon form. The name is used because it is a variation of Gaussian elimination as described by Wilhelm Jordan in 1888. However, the method also appears in an article by Clasen published in the same year. Jordan and Clasen probably discovered Gauss–Jordan elimination independently.


title: Gaussian elimination

text: Historically, the first application of the row reduction method is for solving systems of linear equations. Here are some other important applications of the algorithm.


title: Gaussian elimination

text: To explain how Gaussian elimination allows the computation of the determinant of a square matrix, we have to recall how the elementary row operations change the determinant:


title: Gaussian elimination

text: If Gaussian elimination applied to a square matrix produces a row echelon matrix , let be the product of the scalars by which the determinant has been multiplied, using the above rules. Then the determinant of is the quotient by of the product of the elements of the diagonal of :


title: Gaussian elimination

text: Computationally, for an matrix, this method needs only arithmetic operations, while using Leibniz formula for determinants requires operations (number of summands in the formula), and


title: Gaussian elimination

text: recursive Laplace expansion requires operations (number of sub-determinants to compute, if none is computed twice). Even on the fastest computers, these two methods are impractical or almost impracticable for above 20.formula_6


title: Gaussian elimination

text: A variant of Gaussian elimination called Gauss–Jordan elimination can be used for finding the inverse of a matrix, if it exists. If is an square matrix, then one can use row reduction to compute its inverse matrix, if it exists. First, the identity matrix is augmented to the right of , forming an block matrix . Now through application of elementary row operations, find the reduced echelon form of this matrix. The matrix is invertible if and only if the left block can be reduced to the identity matrix ; in this case the right block of the final matrix is . If the algorithm is unable to reduce the left block to , then is not invertible.


title: Gaussian elimination

text: To find the inverse of this matrix, one takes the following matrix augmented by the identity and row-reduces it as a 3 × 6 matrix:


title: Gaussian elimination

text: By performing row operations, one can check that the reduced row echelon form of this augmented matrix is


title: Gaussian elimination

text: One can think of each row operation as the left product by an elementary matrix. Denoting by the product of these elementary matrices, we showed, on the left, that , and therefore, . On the right, we kept a record of , which we know is the inverse desired. This procedure for finding the inverse works for square matrices of any size.


title: Gaussian elimination

text: The Gaussian elimination algorithm can be applied to any matrix . In this way, for example, some 6 × 9 matrices can be transformed to a matrix that has a row echelon form like


title: Gaussian elimination

text: where the stars are arbitrary entries, and are nonzero entries. This echelon matrix contains a wealth of information about : the rank of is 5, since there are 5 nonzero rows in ; the vector space spanned by the columns of has a basis consisting of its columns 1, 3, 4, 7 and 9 (the columns with in ), and the stars show how the other columns of can be written as linear combinations of the basis columns. This is a consequence of the distributivity of the dot product in the expression of a linear map as a matrix.


title: Gaussian elimination

text: The number of arithmetic operations required to perform row reduction is one way of measuring the algorithm's computational efficiency. For example, to solve a system of equations for unknowns by performing row operations on the matrix until it is in echelon form, and then solving for each unknown in reverse order, requires divisions, multiplications, and subtractions, for a total of approximately operations. Thus it has arithmetic complexity of ; see Big O notation.


title: Gaussian elimination

text: This arithmetic complexity is a good measure of the time needed for the whole computation when the time for each arithmetic operation is approximately constant. This is the case when the coefficients are represented by floating-point numbers or when they belong to a finite field. If the coefficients are integers or rational numbers exactly represented, the intermediate entries can grow exponentially large, so the bit complexity is exponential.


title: Gaussian elimination

text: However, there is a variant of Gaussian elimination, called the Bareiss algorithm, that avoids this exponential growth of the intermediate entries and, with the same arithmetic complexity of , has a bit complexity of .


title: Gaussian elimination

text: This algorithm can be used on a computer for systems with thousands of equations and unknowns. However, the cost becomes prohibitive for systems with millions of equations. These large systems are generally solved using iterative methods. Specific methods exist for systems whose coefficients follow a regular pattern (see system of linear equations).


title: Gaussian elimination

text: To put an matrix into reduced echelon form by row operations, one needs arithmetic operations, which is approximately 50% more computation steps.


title: Gaussian elimination

text: One possible problem is numerical instability, caused by the possibility of dividing by very small numbers. If, for example, the leading coefficient of one of the rows is very close to zero, then to row-reduce the matrix, one would need to divide by that number. This means that any error existed for the number that was close to zero would be amplified. Gaussian elimination is numerically stable for diagonally dominant or positive-definite matrices. For general matrices, Gaussian elimination is usually considered to be stable, when using partial pivoting, even though there are examples of stable matrices for which it is unstable.


title: Gaussian elimination

text: Buchberger's algorithm is a generalization of Gaussian elimination to systems of polynomial equations. This generalization depends heavily on the notion of a monomial order. The choice of an ordering on the variables is already implicit in Gaussian elimination, manifesting as the choice to work from left to right when selecting pivot positions.


title: Gaussian elimination

text: Computing the rank of a tensor of order greater than 2 is NP-hard. Therefore, if , there cannot be a polynomial time analog of Gaussian elimination for higher-order tensors (matrices are array representations of order-2 tensors).


title: Gaussian elimination

text: As explained above, Gaussian elimination transforms a given matrix into a matrix in row-echelon form.


title: Gaussian elimination

text: In the following pseudocode, codice_1 denotes the entry of the matrix in row and column with the indices starting from 1. The transformation is performed "in place", meaning that the original matrix is lost for being eventually replaced by its row-echelon form.


title: Gaussian elimination

text: This algorithm differs slightly from the one discussed earlier, by choosing a pivot with largest absolute value. Such a "partial pivoting" may be required if, at the pivot place, the entry of the matrix is zero. In any case, choosing the largest possible absolute value of the pivot improves the numerical stability of the algorithm, when floating point is used for representing numbers.


title: Gaussian elimination

text: Upon completion of this procedure the matrix will be in row echelon form and the corresponding system may be solved by back substitution.


title: Rings of Saturn

text: The rings of Saturn are the most extensive ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometers to meters, that orbit around Saturn. The ring particles are made almost entirely of water ice, with a trace component of rocky material. There is still no consensus as to their mechanism of formation. Although theoretical models indicated that the rings were likely to have formed early in the Solar System's history, newer data from "Cassini" suggested they formed relatively late.


title: Rings of Saturn

text: Although reflection from the rings increases Saturn's brightness, they are not visible from Earth with unaided vision. In 1610, the year after Galileo Galilei turned a telescope to the sky, he became the first person to observe Saturn's rings, though he could not see them well enough to discern their true nature. In 1655, Christiaan Huygens was the first person to describe them as a disk surrounding Saturn. The concept that Saturn's rings are made up of a series of tiny ringlets can be traced to Pierre-Simon Laplace, although true gaps are few – it is more correct to think of the rings as an annular disk with concentric local maxima and minima in density and brightness. On the scale of the clumps within the rings there is much empty space.


title: Rings of Saturn

text: The rings have numerous gaps where particle density drops sharply: two opened by known moons embedded within them, and many others at locations of known destabilizing orbital resonances with the moons of Saturn. Other gaps remain unexplained. Stabilizing resonances, on the other hand, are responsible for the longevity of several rings, such as the Titan Ringlet and the G Ring.


title: Rings of Saturn

text: Well beyond the main rings is the Phoebe ring, which is presumed to originate from Phoebe and thus to share its retrograde orbital motion. It is aligned with the plane of Saturn's orbit. Saturn has an axial tilt of 27 degrees, so this ring is tilted at an angle of 27 degrees to the more visible rings orbiting above Saturn's equator.


title: Rings of Saturn

text: Galileo Galilei was the first to observe the rings of Saturn in 1610 using his telescope, but was unable to identify them as such. He wrote to the Duke of Tuscany that "The planet Saturn is not alone, but is composed of three, which almost touch one another and never move nor change with respect to one another. They are arranged in a line parallel to the zodiac, and the middle one (Saturn itself) is about three times the size of the lateral ones." He also described the rings as Saturn's "ears". In 1612 the Earth passed through the plane of the rings and they became invisible. Mystified, Galileo remarked "I do not know what to say in a case so surprising, so unlooked for and so novel." He mused, "Has Saturn swallowed his children?" — referring to the myth of the Titan Saturn devouring his offspring to forestall the prophecy of them overthrowing him. He was further confused when the rings again became visible in 1613.


title: Rings of Saturn

text: Early astronomers used anagrams as a form of commitment scheme to lay claim to new discoveries before their results were ready for publication. Galileo used the anagram """" for "Altissimum planetam tergeminum observavi" ("I have observed the most distant planet to have a triple form") for discovering the rings of Saturn.


title: Rings of Saturn

text: In 1657 Christopher Wren became Professor of Astronomy at Gresham College, London. He had been making observations of the planet Saturn from around 1652 with the aim of explaining its appearance. His hypothesis was written up in "De corpore saturni," in which he came close to suggesting the planet had a ring. However, Wren was unsure whether the ring was independent of the planet, or physically attached to it. Before Wren's theory was published Christiaan Huygens presented his theory of the rings of Saturn. Immediately Wren recognised this as a better hypothesis than his own and "De corpore saturni" was never published. Robert Hooke was another early observer of the rings of Saturn, and noted the casting of shadows on the rings.


title: Rings of Saturn

text: Huygens began grinding lenses with his brother Constantijn in 1655 and was able to observe Saturn with greater detail using a 43× power refracting telescope that he designed himself. He was the first to suggest that Saturn was surrounded by a ring detached from the planet, and famously published the anagram: """". Three years later, he revealed it to mean "Annuto cingitur, tenui, plano, nusquam coherente, ad eclipticam inclinato" ("[Saturn] is surrounded by a thin, flat, ring, nowhere touching, inclined to the ecliptic"). He published his ring theory in "Systema Saturnium" (1659) which also included his discovery of Saturn's moon, Titan, as well as the first clear outline of the dimensions of the Solar System.


title: Rings of Saturn

text: In 1675, Giovanni Domenico Cassini determined that Saturn's ring was composed of multiple smaller rings with gaps between them; the largest of these gaps was later named the Cassini Division. This division is a 4,800-km-wide region between the A ring and B Ring.


title: Rings of Saturn

text: In 1787, Pierre-Simon Laplace proved that a uniform solid ring would be unstable and suggested that the rings were composed of a large number of solid ringlets.


title: Rings of Saturn

text: In 1859, James Clerk Maxwell demonstrated that a nonuniform solid ring, solid ringlets or a continuous fluid ring would also not be stable, indicating that the ring must be composed of numerous small particles, all independently orbiting Saturn. Later, Sofia Kovalevskaya also found that Saturn's rings cannot be liquid ring-shaped bodies. Spectroscopic studies of the rings which were carried out independently in 1895 by James Keeler of the Allegheny Observatory and by Aristarkh Belopolsky of the Pulkovo Observatory showed that Maxwell's analysis was correct.


title: Rings of Saturn

text: Four robotic spacecraft have observed Saturn's rings from the vicinity of the planet. "Pioneer 11"s closest approach to Saturn occurred in September 1979 at a distance of 20,900 km. "Pioneer 11" was responsible for the discovery of the F ring. "Voyager 1"s closest approach occurred in November 1980 at a distance of 64,200 km. A failed photopolarimeter prevented "Voyager 1" from observing Saturn's rings at the planned resolution; nevertheless, images from the spacecraft provided unprecedented detail of the ring system and revealed the existence of the G ring. "Voyager 2"s closest approach occurred in August 1981 at a distance of 41,000 km. "Voyager 2"s working photopolarimeter allowed it to observe the ring system at higher resolution than "Voyager 1", and to thereby discover many previously unseen ringlets. "Cassini" spacecraft entered into orbit around Saturn in July 2004. "Cassini" images of the rings are the most detailed to-date, and are responsible for the discovery of yet more ringlets.


title: Rings of Saturn

text: The rings are named alphabetically in the order they were discovered (A and B in 1675 by Giovanni Domenico Cassini, C in 1850 by William Cranch Bond and his son George Phillips Bond, D in 1933 by Nikolai P. Barabachov and B. Semejkin, E in 1967 by Walter A. Feibelman, F in 1979 by "Pioneer 11", and G in 1980 by "Voyager 1"). The main rings are, working outward from the planet, C, B and A, with the Cassini Division, the largest gap, separating Rings B and A. Several fainter rings were discovered more recently. The D Ring is exceedingly faint and closest to the planet. The narrow F Ring is just outside the A Ring. Beyond that are two far fainter rings named G and E. The rings show a tremendous amount of structure on all scales, some related to perturbations by Saturn's moons, but much unexplained.


title: Rings of Saturn

text: Saturn's axial tilt is 26.7°, meaning that widely varying views of the rings, of which the visible ones occupy its equatorial plane, are obtained from Earth at different times. Earth makes passes through the ring plane every 13 to 15 years, about every half Saturn year, and there are about equal chances of either a single or three crossings occurring in each such occasion. The most recent ring plane crossings were on 22 May 1995, 10 August 1995, 11 February 1996 and 4 September 2009; upcoming events will occur on 23 March 2025, 15 October 2038, 1 April 2039 and 9 July 2039. Favorable ring plane crossing viewing opportunities (with Saturn not close to the Sun) only come during triple crossings.


title: Rings of Saturn

text: Saturn's equinoxes, when the Sun passes through the ring plane, are not evenly spaced; on each orbit the Sun is south of the ring plane for 13.7 Earth years, then north of the plane for 15.7 years. Dates for its northern hemisphere autumnal equinoxes include 19 November 1995 and 6 May 2025, with northern vernal equinoxes on 11 August 2009 and 23 January 2039. During the period around an equinox the illumination of most of the rings is greatly reduced, making possible unique observations highlighting features that depart from the ring plane.


title: Rings of Saturn

text: The dense main rings extend from to away from Saturn's equator, whose radius is (see Major subdivisions). With an estimated local thickness of as little as 10 m and as much as 1 km, they are composed of 99.9% pure water ice with a smattering of impurities that may include tholins or silicates. The main rings are primarily composed of particles smaller than 10 m.


title: Rings of Saturn

text: "Cassini" directly measured the mass of the ring system via their gravitational effect during its final set of orbits that passed between the rings and the cloud tops, yielding a value of 1.54 (± 0.49) × 10 kg, or 0.41 ± 0.13 Mimas masses. This is as massive as about half the mass of the Earth's entire Antarctic ice shelf, spread across a surface area 80 times larger than that of Earth. The estimate is close to the value of 0.40 Mimas masses derived from "Cassini" observations of density waves in the A, B and C rings. It is a small fraction of the total mass of Saturn (about 0.25 ppb). Earlier "Voyager" observations of density waves in the A and B rings and an optical depth profile had yielded a mass of about 0.75 Mimas masses, with later observations and computer modeling suggesting that was an underestimate.


title: Rings of Saturn

text: Although the largest gaps in the rings, such as the Cassini Division and Encke Gap, can be seen from Earth, the Voyager spacecraft discovered that the rings have an intricate structure of thousands of thin gaps and ringlets. This structure is thought to arise, in several different ways, from the gravitational pull of Saturn's many moons. Some gaps are cleared out by the passage of tiny moonlets such as Pan, many more of which may yet be discovered, and some ringlets seem to be maintained by the gravitational effects of small shepherd satellites (similar to Prometheus and Pandora's maintenance of the F ring). Other gaps arise from resonances between the orbital period of particles in the gap and that of a more massive moon further out; Mimas maintains the Cassini Division in this manner. Still more structure in the rings consists of spiral waves raised by the inner moons' periodic gravitational perturbations at less disruptive resonances.


title: Rings of Saturn

text: Data from the "Cassini" space probe indicate that the rings of Saturn possess their own atmosphere, independent of that of the planet itself. The atmosphere is composed of molecular oxygen gas (O) produced when ultraviolet light from the Sun interacts with water ice in the rings. Chemical reactions between water molecule fragments and further ultraviolet stimulation create and eject, among other things, O. According to models of this atmosphere, H is also present. The O and H atmospheres are so sparse that if the entire atmosphere were somehow condensed onto the rings, it would be about one atom thick. The rings also have a similarly sparse OH (hydroxide) atmosphere. Like the O, this atmosphere is produced by the disintegration of water molecules, though in this case the disintegration is done by energetic ions that bombard water molecules ejected by Saturn's moon Enceladus. This atmosphere, despite being extremely sparse, was detected from Earth by the Hubble Space Telescope.


title: Rings of Saturn

text: Saturn shows complex patterns in its brightness. Most of the variability is due to the changing aspect of the rings, and this goes through two cycles every orbit. However, superimposed on this is variability due to the eccentricity of the planet's orbit that causes the planet to display brighter oppositions in the northern hemisphere than it does in the southern.


title: Rings of Saturn

text: In 1980, "Voyager 1" made a fly-by of Saturn that showed the F ring to be composed of three narrow rings that appeared to be braided in a complex structure; it is now known that the outer two rings consist of knobs, kinks and lumps that give the illusion of braiding, with the less bright third ring lying inside them.


title: Rings of Saturn

text: New images of the rings taken around the 11 August 2009 equinox of Saturn by NASA's "Cassini" spacecraft have shown that the rings extend significantly out of the nominal ring plane in a few places. This displacement reaches as much as at the border of the Keeler Gap, due to the out-of-plane orbit of Daphnis, the moon that creates the gap.


title: Rings of Saturn

text: Estimates of the age of Saturn's rings vary widely, depending on the approach used. They have been considered to possibly be very old, dating to the formation of Saturn itself. However, data from "Cassini" suggest they are much younger, having most likely formed within the last 100 million years, and may thus be between 10 million and 100 million years old. This recent origin scenario is based on a new, low mass estimate, modeling of the rings' dynamical evolution, and measurements of the flux of interplanetary dust, which feed into an estimate of the rate of ring darkening over time. Since the rings are continually losing material, they would have been more massive in the past than at present. The mass estimate alone is not very diagnostic, since high mass rings that formed early in the Solar System's history would have evolved by now to a mass close to that measured. Based on current depletion rates, they may disappear in 300 million years.


title: Rings of Saturn

text: There are two main theories regarding the origin of Saturn's inner rings. A theory originally proposed by Édouard Roche in the 19th century, is that the rings were once a moon of Saturn (named Veritas, after a Roman goddess who hid in a well). According to the theory the moon's orbit decayed until it was close enough to be ripped apart by tidal forces (see Roche limit). Numerical simulations carried out in 2022 support this theory; the authors of that study proposed the name "Chrysalis" for the destroyed moon. A variation on this theory is that this moon disintegrated after being struck by a large comet or asteroid. The second theory is that the rings were never part of a moon, but are instead left over from the original nebular material from which Saturn formed.


title: Rings of Saturn

text: A more traditional version of the disrupted-moon theory is that the rings are composed of debris from a moon 400 to 600 km in diameter, slightly larger than Mimas. The last time there were collisions large enough to be likely to disrupt a moon that large was during the Late Heavy Bombardment some four billion years ago.


title: Rings of Saturn

text: A more recent variant of this type of theory by R. M. Canup is that the rings could represent part of the remains of the icy mantle of a much larger, Titan-sized, differentiated moon that was stripped of its outer layer as it spiraled into the planet during the formative period when Saturn was still surrounded by a gaseous nebula. This would explain the scarcity of rocky material within the rings. The rings would initially have been much more massive (≈1,000 times) and broader than at present; material in the outer portions of the rings would have coalesced into the moons of Saturn out to Tethys, also explaining the lack of rocky material in the composition of most of these moons. Subsequent collisional or cryovolcanic evolution of Enceladus might then have caused selective loss of ice from this moon, raising its density to its current value of 1.61 g/cm, compared to values of 1.15 for Mimas and 0.97 for Tethys.


title: Rings of Saturn

text: The idea of massive early rings was subsequently extended to explain the formation of Saturn's moons out to Rhea. If the initial massive rings contained chunks of rocky material (>100 km across) as well as ice, these silicate bodies would have accreted more ice and been expelled from the rings, due to gravitational interactions with the rings and tidal interaction with Saturn, into progressively wider orbits. Within the Roche limit, bodies of rocky material are dense enough to accrete additional material, whereas less-dense bodies of ice are not. Once outside the rings, the newly formed moons could have continued to evolve through random mergers. This process may explain the variation in silicate content of Saturn's moons out to Rhea, as well as the trend towards less silicate content closer to Saturn. Rhea would then be the oldest of the moons formed from the primordial rings, with moons closer to Saturn being progressively younger.


title: Rings of Saturn

text: The brightness and purity of the water ice in Saturn's rings have also been cited as evidence that the rings are much younger than Saturn, as the infall of meteoric dust would have led to a darkening of the rings. However, new research indicates that the B Ring may be massive enough to have diluted infalling material and thus avoided substantial darkening over the age of the Solar System. Ring material may be recycled as clumps form within the rings and are then disrupted by impacts. This would explain the apparent youth of some of the material within the rings. Evidence suggesting a recent origin of the C ring has been gathered by researchers analyzing data from the Cassini Titan Radar Mapper, which focused on analyzing the proportion of rocky silicates within this ring. If much of this material was contributed by a recently disrupted centaur or moon, the age of this ring could be on the order of 100 million years or less. On the other hand, if the material came primarily from micrometeoroid influx, the age would be closer to a billion years.


title: Rings of Saturn

text: The "Cassini" UVIS team, led by Larry Esposito, used stellar occultation to discover 13 objects, ranging from 27 m to 10 km across, within the F ring. They are translucent, suggesting they are temporary aggregates of ice boulders a few meters across. Esposito believes this to be the basic structure of the Saturnian rings, particles clumping together, then being blasted apart.


title: Rings of Saturn

text: Research based on rates of infall into Saturn favors a younger ring system age of hundreds of millions of years. Ring material is continually spiraling down into Saturn; the faster this infall, the shorter the lifetime of the ring system. One mechanism involves gravity pulling electrically charged water ice grains down from the rings along planetary magnetic field lines, a process termed 'ring rain'. This flow rate was inferred to be 432–2870 kg/s using ground-based Keck telescope observations; as a consequence of this process alone, the rings will be gone in ~ million years. While traversing the gap between the rings and planet in September 2017, the "Cassini" spacecraft detected an equatorial flow of charge-neutral material from the rings to the planet of 4,800–44,000 kg/s. Assuming this influx rate is stable, adding it to the continuous 'ring rain' process implies the rings may be gone in under 100 million years.


title: Rings of Saturn

text: The densest parts of the Saturnian ring system are the A and B Rings, which are separated by the Cassini Division (discovered in 1675 by Giovanni Domenico Cassini). Along with the C Ring, which was discovered in 1850 and is similar in character to the Cassini Division, these regions constitute the "main rings". The main rings are denser and contain larger particles than the tenuous "dusty rings". The latter include the D Ring, extending inward to Saturn's cloud tops, the G and E Rings and others beyond the main ring system. These diffuse rings are characterised as "dusty" because of the small size of their particles (often about a μm); their chemical composition is, like the main rings, almost entirely water ice. The narrow F Ring, just off the outer edge of the A Ring, is more difficult to categorize; parts of it are very dense, but it also contains a great deal of dust-size particles.


title: Rings of Saturn

text: The D Ring is the innermost ring, and is very faint. In 1980, "Voyager 1" detected within this ring three ringlets designated D73, D72 and D68, with D68 being the discrete ringlet nearest to Saturn. Some 25 years later, "Cassini" images showed that D72 had become significantly broader and more diffuse, and had moved planetward by 200 km.


title: Rings of Saturn

text: Present in the D Ring is a finescale structure with waves 30 km apart. First seen in the gap between the C Ring and D73, the structure was found during Saturn's 2009 equinox to extend a radial distance of 19,000 km from the D Ring to the inner edge of the B Ring. The waves are interpreted as a spiral pattern of vertical corrugations of 2 to 20 m amplitude; the fact that the period of the waves is decreasing over time (from 60 km in 1995 to 30 km by 2006) allows a deduction that the pattern may have originated in late 1983 with the impact of a cloud of debris (with a mass of ≈10 kg) from a disrupted comet that tilted the rings out of the equatorial plane. A similar spiral pattern in Jupiter's main ring has been attributed to a perturbation caused by impact of material from Comet Shoemaker-Levy 9 in 1994.


title: Rings of Saturn

text: The C Ring is a wide but faint ring located inward of the B Ring. It was discovered in 1850 by William and George Bond, though William R. Dawes and Johann Galle also saw it independently. William Lassell termed it the "Crepe Ring" because it seemed to be composed of darker material than the brighter A and B Rings.


title: Rings of Saturn

text: Its vertical thickness is estimated at 5 m, its mass at around 1.1 kg, and its optical depth varies from 0.05 to 0.12. That is, between 5 and 12 percent of light shining perpendicularly through the ring is blocked, so that when seen from above, the ring is close to transparent. The 30-km wavelength spiral corrugations first seen in the D Ring were observed during Saturn's equinox of 2009 to extend throughout the C Ring (see above).


title: Rings of Saturn

text: The Colombo Gap lies in the inner C Ring. Within the gap lies the bright but narrow Colombo Ringlet, centered at 77,883 km from Saturn's center, which is slightly elliptical rather than circular. This ringlet is also called the Titan Ringlet as it is governed by an orbital resonance with the moon Titan. At this location within the rings, the length of a ring particle's apsidal precession is equal to the length of Titan's orbital motion, so that the outer end of this eccentric ringlet always points towards Titan.


title: Rings of Saturn

text: The Maxwell Gap lies within the outer part of the C Ring. It also contains a dense non-circular ringlet, the Maxwell Ringlet. In many respects this ringlet is similar to the ε ring of Uranus. There are wave-like structures in the middle of both rings. While the wave in the ε ring is thought to be caused by Uranian moon Cordelia, no moon has been discovered in the Maxwell gap as of July 2008.


title: Rings of Saturn

text: The B Ring is the largest, brightest, and most massive of the rings. Its thickness is estimated as 5 to 15 m and its optical depth varies from 0.4 to greater than 5, meaning that >99% of the light passing through some parts of the B Ring is blocked. The B Ring contains a great deal of variation in its density and brightness, nearly all of it unexplained. These are concentric, appearing as narrow ringlets, though the B Ring does not contain any gaps. In places, the outer edge of the B Ring contains vertical structures deviating up to 2.5 km from the main ring plane.


title: Rings of Saturn

text: A 2016 study of spiral density waves using stellar occultations indicated that the B Ring's surface density is in the range of 40 to 140 g/cm, lower than previously believed, and that the ring's optical depth has little correlation with its mass density (a finding previously reported for the A and C rings). The total mass of the B Ring was estimated to be somewhere in the range of 7 to kg. This compares to a mass for Mimas of kg.


title: Rings of Saturn

text: Until 1980, the structure of the rings of Saturn was explained as being caused exclusively by the action of gravitational forces. Then images from the Voyager spacecraft showed radial features in the B Ring, known as "spokes", which could not be explained in this manner, as their persistence and rotation around the rings was not consistent with gravitational orbital mechanics. The spokes appear dark in backscattered light, and bright in forward-scattered light (see images in Gallery); the transition occurs at a phase angle near 60°. The leading theory regarding the spokes' composition is that they consist of microscopic dust particles suspended away from the main ring by electrostatic repulsion, as they rotate almost synchronously with the magnetosphere of Saturn. The precise mechanism generating the spokes is still unknown, although it has been suggested that the electrical disturbances might be caused by either lightning bolts in Saturn's atmosphere or micrometeoroid impacts on the rings.


title: Rings of Saturn

text: The spokes were not observed again until some twenty-five years later, this time by the "Cassini" space probe. The spokes were not visible when "Cassini" arrived at Saturn in early 2004. Some scientists speculated that the spokes would not be visible again until 2007, based on models attempting to describe their formation. Nevertheless, the "Cassini" imaging team kept looking for spokes in images of the rings, and they were next seen in images taken on 5 September 2005.


title: Rings of Saturn

text: The spokes appear to be a seasonal phenomenon, disappearing in the Saturnian midwinter and midsummer and reappearing as Saturn comes closer to equinox. Suggestions that the spokes may be a seasonal effect, varying with Saturn's 29.7-year orbit, were supported by their gradual reappearance in the later years of the Cassini mission.


title: Rings of Saturn

text: In 2009, during equinox, a moonlet embedded in the B ring was discovered from the shadow it cast. It is estimated to be in diameter. The moonlet was given the provisional designation S/2009 S 1.


title: Rings of Saturn

text: The Cassini Division is a region in width between Saturn's A Ring and B Ring. It was discovered in 1675 by Giovanni Cassini at the Paris Observatory using a refracting telescope that had a 2.5-inch objective lens with a 20-foot-long focal length and a 90x magnification. From Earth it appears as a thin black gap in the rings. However, "Voyager" discovered that the gap is itself populated by ring material bearing much similarity to the C Ring. The division may appear bright in views of the unlit side of the rings, since the relatively low density of material allows more light to be transmitted through the thickness of the rings (see second image in gallery).


title: Rings of Saturn

text: The inner edge of the Cassini Division is governed by a strong orbital resonance. Ring particles at this location orbit twice for every orbit of the moon Mimas. The resonance causes Mimas' pulls on these ring particles to accumulate, destabilizing their orbits and leading to a sharp cutoff in ring density. Many of the other gaps between ringlets within the Cassini Division, however, are unexplained.


title: Rings of Saturn

text: The Huygens Gap is located at the inner edge of the Cassini Division. It contains the dense, eccentric Huygens Ringlet in the middle. This ringlet exhibits irregular azimuthal variations of geometrical width and optical depth, which may be caused by the nearby 2:1 resonance with Mimas and the influence of the eccentric outer edge of the B-ring. There is an additional narrow ringlet just outside the Huygens Ringlet.


title: Rings of Saturn

text: The A Ring is the outermost of the large, bright rings. Its inner boundary is the Cassini Division and its sharp outer boundary is close to the orbit of the small moon Atlas. The A Ring is interrupted at a location 22% of the ring width from its outer edge by the Encke Gap. A narrower gap 2% of the ring width from the outer edge is called the Keeler Gap.


title: Rings of Saturn

text: The thickness of the A Ring is estimated to be 10 to 30 m, its surface density from 35 to 40 g/cm and its total mass as 4 to kg (just under the mass of Hyperion). Its optical depth varies from 0.4 to 0.9.


title: Rings of Saturn

text: Similarly to the B Ring, the A Ring's outer edge is maintained by orbital resonances, albeit in this case a more complicated set. It is primarily acted on by the 7:6 resonance with Janus and Epimetheus, with other contributions from the 5:3 resonance with Mimas and various resonances with Prometheus and Pandora. Other orbital resonances also excite many spiral density waves in the A Ring (and, to a lesser extent, other rings as well), which account for most of its structure. These waves are described by the same physics that describes the spiral arms of galaxies. Spiral bending waves, also present in the A Ring and also described by the same theory, are vertical corrugations in the ring rather than compression waves.


title: Rings of Saturn

text: The Encke Gap is a 325-km-wide gap within the A ring, centered at a distance of 133,590 km from Saturn's center. It is caused by the presence of the small moon Pan, which orbits within it. Images from the "Cassini" probe have shown that there are at least three thin, knotted ringlets within the gap. Spiral density waves visible on both sides of it are induced by resonances with nearby moons exterior to the rings, while Pan induces an additional set of spiraling wakes (see image in gallery).


title: Rings of Saturn

text: Johann Encke himself did not observe this gap; it was named in honour of his ring observations. The gap itself was discovered by James Edward Keeler in 1888. The second major gap in the A ring, discovered by "Voyager", was named the Keeler Gap in his honor.


title: Rings of Saturn

text: The Encke Gap is a "gap" because it is entirely within the A Ring. There was some ambiguity between the terms "gap" and "division" until the IAU clarified the definitions in 2008; before that, the separation was sometimes called the "Encke Division".


title: Rings of Saturn

text: The Keeler Gap is a 42-km-wide gap in the A ring, approximately 250 km from the ring's outer edge. The small moon Daphnis, discovered 1 May 2005, orbits within it, keeping it clear. The moon's passage induces waves in the edges of the gap (this is also influenced by its slight orbital eccentricity). Because the orbit of Daphnis is slightly inclined to the ring plane, the waves have a component that is perpendicular to the ring plane, reaching a distance of 1500 m "above" the plane.


title: Rings of Saturn

text: The Keeler gap was discovered by "Voyager", and named in honor of the astronomer James Edward Keeler. Keeler had in turn discovered and named the Encke Gap in honor of Johann Encke.


title: Rings of Saturn

text: In 2006, four tiny "moonlets" were found in "Cassini" images of the A Ring. The moonlets themselves are only about a hundred metres in diameter, too small to be seen directly; what "Cassini" sees are the "propeller"-shaped disturbances the moonlets create, which are several km across. It is estimated that the A Ring contains thousands of such objects. In 2007, the discovery of eight more moonlets revealed that they are largely confined to a 3,000 km belt, about 130,000 km from Saturn's center, and by 2008 over 150 propeller moonlets had been detected. One that has been tracked for several years has been nicknamed "Bleriot".


title: Rings of Saturn

text: The separation between the A ring and the F Ring has been named the Roche Division in honor of the French physicist Édouard Roche. The Roche Division should not be confused with the Roche limit which is the distance at which a large object is so close to a planet (such as Saturn) that the planet's tidal forces will pull it apart. Lying at the outer edge of the main ring system, the Roche Division is in fact close to Saturn's Roche limit, which is why the rings have been unable to accrete into a moon.


title: Rings of Saturn

text: Like the Cassini Division, the Roche Division is not empty but contains a sheet of material. The character of this material is similar to the tenuous and dusty D, E, and G Rings. Two locations in the Roche Division have a higher concentration of dust than the rest of the region. These were discovered by the "Cassini" probe imaging team and were given temporary designations: R/2004 S 1, which lies along the orbit of the moon Atlas; and R/2004 S 2, centered at 138,900 km from Saturn's center, inward of the orbit of Prometheus.


title: Rings of Saturn

text: The F Ring is the outermost discrete ring of Saturn and perhaps the most active ring in the Solar System, with features changing on a timescale of hours. It is located 3,000 km beyond the outer edge of the A ring. The ring was discovered in 1979 by the Pioneer 11 imaging team. It is very thin, just a few hundred km in radial extent. While the traditional view has been that it is held together by two shepherd moons, Prometheus and Pandora, which orbit inside and outside it, recent studies indicate that only Prometheus contributes to the confinement. Numerical simulations suggest the ring was formed when Prometheus and Pandora collided with each other and were partially disrupted.


title: Rings of Saturn

text: More recent closeup images from the "Cassini" probe show that the F Ring consists of one core ring and a spiral strand around it. They also show that when Prometheus encounters the ring at its apoapsis, its gravitational attraction creates kinks and knots in the F Ring as the moon 'steals' material from it, leaving a dark channel in the inner part of the ring (see video link and additional F Ring images in gallery). Since Prometheus orbits Saturn more rapidly than the material in the F ring, each new channel is carved about 3.2 degrees in front of the previous one.


title: Rings of Saturn

text: In 2008, further dynamism was detected, suggesting that small unseen moons orbiting within the F Ring are continually passing through its narrow core because of perturbations from Prometheus. One of the small moons was tentatively identified as S/2004 S 6.


title: Rings of Saturn

text: A faint dust ring is present around the region occupied by the orbits of Janus and Epimetheus, as revealed by images taken in forward-scattered light by the "Cassini" spacecraft in 2006. The ring has a radial extent of about 5,000 km. Its source is particles blasted off the moons' surfaces by meteoroid impacts, which then form a diffuse ring around their orbital paths.


title: Rings of Saturn

text: The G Ring (see last image in gallery) is a very thin, faint ring about halfway between the F Ring and the beginning of the E Ring, with its inner edge about 15,000 km inside the orbit of Mimas. It contains a single distinctly brighter arc near its inner edge (similar to the arcs in the rings of Neptune) that extends about one-sixth of its circumference, centered on the half-km diameter moonlet Aegaeon, which is held in place by a 7:6 orbital resonance with Mimas. The arc is believed to be composed of icy particles up to a few m in diameter, with the rest of the G Ring consisting of dust released from within the arc. The radial width of the arc is about 250 km, compared to a width of 9,000 km for the G Ring as a whole. The arc is thought to contain matter equivalent to a small icy moonlet about a hundred m in diameter. Dust released from Aegaeon and other source bodies within the arc by micrometeoroid impacts drifts outward from the arc because of interaction with Saturn's magnetosphere (whose plasma corotates with Saturn's magnetic field, which rotates much more rapidly than the orbital motion of the G Ring). These tiny particles are steadily eroded away by further impacts and dispersed by plasma drag. Over the course of thousands of years the ring gradually loses mass, which is replenished by further impacts on Aegaeon.


title: Rings of Saturn

text: A faint ring arc, first detected in September 2006, covering a longitudinal extent of about 10 degrees is associated with the moon Methone. The material in the arc is believed to represent dust ejected from Methone by micrometeoroid impacts. The confinement of the dust within the arc is attributable to a 14:15 resonance with Mimas (similar to the mechanism of confinement of the arc within the G ring). Under the influence of the same resonance, Methone librates back and forth in its orbit with an amplitude of 5° of longitude.


title: Rings of Saturn

text: A faint ring arc, first detected in June 2007, covering a longitudinal extent of about 20 degrees is associated with the moon Anthe. The material in the arc is believed to represent dust knocked off Anthe by micrometeoroid impacts. The confinement of the dust within the arc is attributable to a 10:11 resonance with Mimas. Under the influence of the same resonance, Anthe drifts back and forth in its orbit over 14° of longitude.


title: Rings of Saturn

text: A faint dust ring shares Pallene's orbit, as revealed by images taken in forward-scattered light by the "Cassini" spacecraft in 2006. The ring has a radial extent of about 2,500 km. Its source is particles blasted off Pallene's surface by meteoroid impacts, which then form a diffuse ring around its orbital path.


title: Rings of Saturn

text: The E Ring is the second outermost ring and is extremely wide; it consists of many tiny (micron and sub-micron) particles of water ice with silicates, carbon dioxide and ammonia. The E Ring is distributed between the orbits of Mimas and Titan. Unlike the other rings, it is composed of microscopic particles rather than macroscopic ice chunks. In 2005, the source of the E Ring's material was determined to be cryovolcanic plumes emanating from the "tiger stripes" of the south polar region of the moon Enceladus. Unlike the main rings, the E Ring is more than 2,000 km thick and increases with its distance from Enceladus. Tendril-like structures observed within the E Ring can be related to the emissions of the most active south polar jets of Enceladus.


title: Rings of Saturn

text: Particles of the E Ring tend to accumulate on moons that orbit within it. The equator of the leading hemisphere of Tethys is tinted slightly blue due to infalling material. The trojan moons Telesto, Calypso, Helene and Polydeuces are particularly affected as their orbits move up and down the ring plane. This results in their surfaces being coated with bright material that smooths out features.


title: Rings of Saturn

text: In October 2009, the discovery of a tenuous disk of material just interior to the orbit of Phoebe was reported. The disk was aligned edge-on to Earth at the time of discovery. This disk can be loosely described as another ring. Although very large (as seen from Earth, the apparent size of two full moons), the ring is virtually invisible. It was discovered using NASA's infrared Spitzer Space Telescope, and was seen over the entire range of the observations, which extended from 128 to 207 times the radius of Saturn, with calculations indicating that it may extend outward up to 300 Saturn radii and inward to the orbit of Iapetus at 59 Saturn radii. The ring was subsequently studied using the WISE, "Herschel" and "Cassini" spacecraft; WISE observations show that it extends from at least between 50 and 100 to 270 Saturn radii (the inner edge is lost in the planet's glare). Data obtained with WISE indicate the ring particles are small; those with radii greater than 10 cm comprise 10% or less of the cross-sectional area.