Cassini: The end of an era

Or alternatively: How a gamma-ray astronomer ended up being invited to watch a space probe crash into a planet

I often think that high energy astrophysics (the gamma ray kind, not the kind of astronomy done after overindulging in coffee) suffers from being trapped within the confines of the ivory tower more than other areas of astronomy. The main reason for this, as I see it - or rather as I don't see it - is because we humans have been blessed to have evolved without the ability to see gamma rays and x-rays. And there's a lot more romance at looking up at a starry night sky with your own eyeballs than hacking away at data with some heinously complicated deconvolution algorithm anyway.

 

There's also the scale problem. There are numbers the human brain can deal with, and then there's numbers that are just so unfathomably ridiculously large or small that a warning light comes on and the information you're trying to convey bypasses the brain entirely. I mean, what sounds more impressive: 1.2 billion or 10^43 (a one followed by 44 zeros)? 0.000001 or 10^-27 (a 1 preceeded by 26 zeros after the decimal point)?

 

The problem with gamma ray astronomy is it is the science of the unseeable, resulting from unfathomably tiny things doing things after unfathomably long times at unfathomable distances away from Earth. To make this understandable, a lot of time goes in to translating ridiculous numbers into something that humans can relate to. For example, to match the rate of production of antimatter positrons in the Galaxy, you'd need one solar mass of bananas to produce positrons every second through the decay of radioactive potassium, which results in some fairly weird mental images but at least it's vaguely understandable

Bananas are sadly not the source of most Galactic antimatter,  as proven by a paper published earlier this year by my research group .

Bananas are sadly not the source of most Galactic antimatter, as proven by a paper published earlier this year by my research group.

Something wonderful about writing about the exploration of the solar system is that it's so intuitive. Nothing seems to capture people's imagination (mine included) than the existence of worlds beyond our own, and there's something incredibly tangible about the first voyages of discovery we make into our cosmological back yard. And much of this is thanks to the incredible work of the scientists behind the Voyager missions, and over the past 20 or so years, the Cassini mission to Saturn.

 

The reason Saturn usually tops the lists of peoples favorite planets is mostly thanks to the beautiful imagery Cassini has brought us over the past 20 years as it has studied the giant gas planet and its many unique moons. Many of the images of the planet, obtained by the Cassini probe 1.3 billion kilometers away in orbit around Saturn, released by NASA are almost indistinguishable from artists impressions.

An image of Saturn and its rings, obtained by the Cassini space probe. NASA/JPL

An image of Saturn and its rings, obtained by the Cassini space probe. NASA/JPL

This week, Cassini will end it's 20 year mission, crashing into the atmosphere of Saturn at 10:15pm Australian Eastern Standard Time. The probe has been slowly deorbiting over the past few months, diving between the planet's rings. The rationale behind disposing of the spacecraft by crashing it into the gas giant planet is simple: to protect the delicate environments of Saturn's moons - which could possibly harbour life -  from any human made debris.

 

I've been very fortunate to be chosen to be amongst scientists and journalists who will report live on the final hours of the Cassini mission from the Deep Space Communications Complex at Tidbinbilla, just outside of Canberra. It's exciting to be able to talk about science without resorting to ridiculous banana analogies, and to talk about something that inspired me to pursue a career in astronomy. Stay tuned for more Saturn related blogs this week, and don't forget to follow the final days of the Cassini mission via the #GrandFinale hashtag on Twitter.