3 min read<\/p>\n
NASA\u2019s Hubble Watches \u2018Spoke Season\u2019 on Saturn<\/h1>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n![\"Colorful](\"https:\/\/smd-cms.nasa.gov\/wp-content\/uploads\/2023\/12\/hubble-saturn-oct2023-stsci-01hgxc6bfxwq6kfgxbptrn6mcq.png?w=1755\")
<\/figure>\nThis NASA Hubble Space Telescope photo of Saturn reveals the planet\u2019s cloud bands and a phenomenon called ring spokes.<\/div>\nNASA, ESA, STScI, Amy Simon (NASA-GSFC)<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\nThis photo of Saturn was taken by NASA\u2019s Hubble Space Telescope<\/a> on October 22, 2023, when the ringed planet was approximately 850 million miles from Earth. Hubble\u2019s ultra-sharp vision reveals a phenomenon called ring spokes.<\/p>\nSaturn\u2019s spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern.<\/p>\n
In 1981, NASA\u2019s Voyager 2<\/a> first photographed the ring spokes. NASA\u2019s Cassini<\/a> orbiter also saw the spokes during its 13-year-long mission that ended in 2017.<\/p>\nHubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble\u2019s Outer Planets Atmospheres Legacy (OPAL<\/a>) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets.<\/p>\nHubble\u2019s crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring show that both the number and contrast of the spokes vary with Saturn\u2019s seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years.<\/p>\n
\u201cWe are heading towards Saturn equinox, when we\u2019d expect maximum spoke activity, with higher frequency and darker spokes appearing over the next few years,\u201d said the OPAL program lead scientist, Amy Simon of NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland.<\/p>\n
This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth\u2019s diameter!<\/p>\n
\u201cThe leading theory is that spokes are tied to Saturn\u2019s powerful magnetic field, with some sort of solar interaction with the magnetic field that gives you the spokes,\u201d said Simon. When it\u2019s near the equinox on Saturn<\/a>, the planet and its rings are less tilted away from the Sun. In this configuration, the solar wind may more strongly batter Saturn\u2019s immense magnetic field, enhancing spoke formation.<\/p>\nPlanetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery.<\/p>\n
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<\/figure>This photo of Saturn was taken by NASA\u2019s Hubble Space Telescope<\/a> on October 22, 2023, when the ringed planet was approximately 850 million miles from Earth. Hubble\u2019s ultra-sharp vision reveals a phenomenon called ring spokes.<\/p>\n Saturn\u2019s spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern.<\/p>\n In 1981, NASA\u2019s Voyager 2<\/a> first photographed the ring spokes. NASA\u2019s Cassini<\/a> orbiter also saw the spokes during its 13-year-long mission that ended in 2017.<\/p>\n Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble\u2019s Outer Planets Atmospheres Legacy (OPAL<\/a>) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets.<\/p>\n Hubble\u2019s crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring show that both the number and contrast of the spokes vary with Saturn\u2019s seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years.<\/p>\n \u201cWe are heading towards Saturn equinox, when we\u2019d expect maximum spoke activity, with higher frequency and darker spokes appearing over the next few years,\u201d said the OPAL program lead scientist, Amy Simon of NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland.<\/p>\n This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth\u2019s diameter!<\/p>\n \u201cThe leading theory is that spokes are tied to Saturn\u2019s powerful magnetic field, with some sort of solar interaction with the magnetic field that gives you the spokes,\u201d said Simon. When it\u2019s near the equinox on Saturn<\/a>, the planet and its rings are less tilted away from the Sun. In this configuration, the solar wind may more strongly batter Saturn\u2019s immense magnetic field, enhancing spoke formation.<\/p>\n Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery.<\/p>\n
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