With 67 moons, the most of any planet, you might think that three moons lining up in “front” of Jupiter would happen often, it doesn’t.
Jupiter’s four largest moons: Io, Europa, Ganymede and Callisto are also known as the Galilean satellites as they were discovered by Galileo himself. Not only are they the largest but they are the most famous as well and the Hubble telescope recently captured a transit by Europa, Callisto and Io.
The pictures and an unmanned visit?
Thankfully the moon transit is a predictable affair so Hubble was in the right place at the right time. It’s a bit of a shame that Ganymede didn’t join in on the fun.
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The two shots were taken on Jan 23 (43 minutes apart) by Hubble’s Wide Field Camera 3 in visible light. The Europa sighting comes just days after Obama put forth his budget proposal for NASA in 2016, that included monies for an unmanned trip to Jupiter’s Europa.
The Jupiter moon transit occurs once or twice in a decade meaning that this may be the last time those on Earth will get to see the lunar parade as observed by Hubble. The telescope has been in space for about 25 years and NASA is hoping that it will remain functional until 2020 or even beyond.
Hubble until 2020?
The last servicing of the Hubble was in 2009 by astronauts on the space shuttle. With the shuttle program shut down, that means that 2009 was literally the last time Hubble servicing. Numerous components of Hubble are functioning near perfectly while other systems are expected to shut down sooner than hoped.
But that is not to say that these deep space pictures will stop altogether. NASA expects to launch Hubble’s successor, the James Webb Space Telescope (JWST) in 2018. If Hubble could continue to function properly through 2020, it would give NASA and unprecedented “one-two” punch for while.
“We’re conducting what we’re calling the ‘2020 vision’ for Hubble, and that is to make sure that the observatory is ready to run for at least five or six years to get at least a year of overlap with James Webb, if not more,” said Kenneth Sembach of the Space Telescope Science Institute in January. “We’re lucky in that we have very proactive engineering that’s been going on over the last few years and continues to go on both at the [Space Telescope Science] Institute and at [NASA’s] Goddard [Space Flight Center] to make sure that we’re operating the observatory as safely and as effectively as we can. So, we’re going to get to 2020.”
“The Hubble Space Telescope mission office and the James Webb Space Telescope mission office are discussing ways that we can allow people that have excellent science ideas that require both facilities to take data of the same targets to get those data sets on both missions,” added Jason Kalirai (also) of the Space Telescope Science Institute.
Both scientists’ remarks were made during a news conference in January at the 225th meeting of the American Astronomical Society.