This column first ran in The Tablet in July 2016
On July 4, 2016, the Juno spacecraft went into orbit around Jupiter, beginning its mission to probe the interior of our solar system’s largest planet..., and undoubtedly it will be years before we really know what we’ve found there. [The latest results can be found here.]
Even though my own research has little to do with Jupiter, I have a personal stake in this spacecraft. Back ten years ago when NASA was deciding what their next big mission would be they solicited proposals from the community, and Juno was one of five possible missions reviewed by a panel of experts. I was one of those experts [as described in an earlier Across the Universe posting, here].
The Juno proposal addressed a fundamental question about gas giant planets like Jupiter and Saturn. (Hundreds of such gas giants have been discovered orbiting other stars, as well.) Are they lumps of gas that didn’t quite grow big enough to become stars themselves while they were forming within a larger star-forming gas cloud? Or did they start as solid planets that grew big enough to trap lots of gas from such a cloud? Whichever theory turns out to be right will shape how we understand the origins of stars and planets.
Jupiter is the perfect test case. By measuring its gravity field in great detail and learning the chemical composition of its deep interior from its microwave radiation, we think we can resolve one way or the other whether Jupiter has a rocky core or if it is a gas ball like the Sun. Of course, nature being what it is, the truth will probably be more complicated than either of our theories!
Our review panel was quite impressed with the Juno proposal… and worried that NASA wouldn’t select it because the science, while important to the experts, would be hard to explain to the average layperson. So at the last minute, the mission added a camera to send back ordinary images of Jupiter. That will help bridge the gap between the abstract data underlying our theoretical constructs, and the real, recognizable planet Jupiter.
I have another connection with the Juno mission beyond my role in helping choose it. About half of principal scientists who’ll be studying its data are personal friends of mine. They include an old professor who sat on my PhD committee; someone who was in graduate school with me; even a classmate from my high school days. One of them is a close associate of the Vatican Observatory who’s become a convert to Catholicism. Another member of the team, back when she was a graduate student, shared the apartment of a woman I was dating in my pre-Jesuit life.
Jupiter may be a gas giant planet but the community studying it is a small world. There are fewer than a thousand active planetary astronomers in the world; we all went to the same schools, we all attend the same meetings. Another example of small worlds: a dwarf planet orbiting beyond Neptune has been discovered just this month ; the announcement was made by Michele Bannister, who was a student at our 2007 Vatican Summer School. [For more about this, see her fascinating article here.]
Also falling in July, two days after Juno’s arrival at Jupiter, is the feast of the child saint St. Maria Goretti. She lived near our observatory headquarters in Albano, Italy, before her tragic death in 1902. I’ve heard her great-niece speaking at the local cathedral.
Scientists and saints aren’t mere theoretical constructs. You probably know someone who has met one. For that matter, you can see Jupiter for yourself this month: a bright star setting in the evening sky.
[The Juno mission is a popular subject of posts here at The Catholic Astronomer; do a search and you'll find at least two dozen of them!]