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Quadruple Saturn Moon Transit Snapped By Hubble
On February 24, 2009, the Hubble Space Telescope took a photo of four moons of Saturn passing in front of their parent planet. In this view, the giant orange moon Titan casts a large shadow onto Saturn's north polar hood. Below Titan, near the ring plane and to the left is the moon Mimas, casting a much smaller shadow onto Saturn's equatorial cloud tops. Farther to the left, and off Saturn's disk, are the bright moon Dione and the fainter moon Enceladus.
These rare moon transits only happen when the tilt of Saturn's ring plane is nearly "edge on" as seen from the Earth. Saturn's rings will be perfectly edge on to our line of sight on August 10, 2009, and September 4, 2009. Unfortunately, Saturn will be too close to the sun to be seen by viewers on Earth at that time. This "ring plane crossing" occurs every 14-15 years. In 1995-96 Hubble witnessed the ring plane crossing event, as well as many moon transits, and even helped discover several new moons of Saturn.
The banded structure in Saturn's atmosphere is similar to Jupiter's.
Early 2009 was a favorable time for viewers with small telescopes to watch moon and shadow transits crossing the face of Saturn. Titan, Saturn's largest moon, crossed Saturn on four separate occasions: January 24, February 9, February 24, and March 12, although not all events were visible from all locations on Earth.
These pictures were taken with Hubble's Wide Field Planetary Camera 2 on February 24, 2009, when Saturn was at a distance of roughly 775 million miles (1.25 billion kilometers) from Earth. Hubble can see details as small as 190 miles (300 km) across on Saturn. The dark band running across the face of the planet slightly above the rings is the shadow of the rings cast on the planet.
About the Object
- DistanceDistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.The semi-major axis of Saturn's orbit about the sun is 9.5 astronomical units (A.U.) or roughly 1.4 billion km.
- DimensionsDimensionsThe physical size of the object or the apparent angle it subtends on the sky.The planet (without rings) has a diameter of roughly 75,000 miles (120,000 km) at the equator.
About the Data
- Data DescriptionData DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.The Hubble images and videos were created from HST data from proposal 11956: K. Noll, Z. Levay, M. Mutchler, L. Frattare, C. Christian, F. Hamilton, and H. Bond (The Hubble Heritage Team/STScI/AURA). B. Januszewski (STScI), M.H. Wong (UC Berkeley/STScI), and C. Go (Phillipines) also helped with image conception, proposal preparation/processing and data analysis. - InstrumentInstrumentThe science instrument used to produce the data.HST>WFPC2
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.February 24, 2009 12:12 UT
- FiltersFiltersThe camera filters that were used in the science observations.F439W (B), F555W (V), and F675W (R)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.Saturn
- Object DescriptionObject DescriptionThe type of astronomical object.Planet with Satellites
- Release DateMarch 17, 2009
- Science ReleaseQuadruple Saturn Moon Transit Snapped by Hubble
- Credit
The image is a composite of separate exposures made by the WFPC2 instrument on the Hubble Space Telescope. Three filters were used to sample broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Blue: F439W (B) Green: F555W (V) Red: F675W (R)
Related Images & Videos
HST Image of Saturn Moon Transits
This sequence of images captures the parade of several of Saturn's moons transiting the face of the gas giant planet. This is a rare event because the rings are tilted edge on to Earth every 15 years. The top frame captures the giant moon Titan and its shadow near Saturn's...
Closeup of Quadruple Saturn Moon Transit
This close-up view of Saturn's disk captures the transit of several moons across the face of the gas giant planet. The giant orange moon Titan – larger than the planet Mercury – can be seen at upper right. The white icy moons that are much closer to Saturn, hence much closer to...
Saturn's Rings Viewed from Earth
As Saturn travels around its orbit, Hubble sees a different view of the tilted rings from a position near Earth. The rings nearly disappear twice during Saturn's approximately 30-year orbit, because we see them edge on and they are extremely thin relative to their diameter.
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
