Starts With A Bang Podcast #47 – Ice Giants At The Solar System’s Edge
What do we really know, and what mysteries are left to solve, about the outer worlds of our Solar System, and about the gas giant and ice giant worlds found throughout the Universe? Remarkably, if you had asked this same question 30 years ago, we would have had a quaint story about how planets form and why our Solar System has the planets it does, and we assumed that these rules would be extended to all solar systems in the galaxy and Universe. But with the deluge of exoplanet data, accompanied by better observations and simulations of our Solar System, that old story isn’t even the half of it.
I’m so lucky to get to interview Heidi Hammel for this edition of the podcast, who, as a bonus, was the lead investigator on the Hubble Space telescope when Comet Shoemaker-Levy 9 impacted Jupiter back in 1994! Come listen to one of my favorite interviews ever today!
(Image credit: NASA/Voyager 2)
Voyager’s ‘Cosmic Map’ Of Earth’s Location Is Hopelessly Wrong
“Most neutron stars don’t appear as pulsars to us, simply because their “pulses” aren’t lined up with planet Earth. But over time, pulsars can newly appear or disappear, which we’ve actually seen happen since the Voyager probes were launched. As objects rotate and orbit in space, their relative orientations change, so the pulsars that are pointing at us today won’t be pointing at us millions of years in the future. Additionally, pulsars that aren’t pointing at us today will be pointing at us in millions of years. Compound that with the fact that neutron stars adjust their rotation periods over time (via starquakes and pulsar speedup), and it’s clear that both the periods and orientations of these pulsars change dramatically over millions of years. By the time any alien picks up our pulsar map, it will be woefully out-of-date.”
When the Voyager and Pioneer spacecraft were launched, they contained a message emblazoned on them: a map of 14 pulsars, showing the location of Earth relative to them. This was a brilliant idea: showcase bright, unique identifiers, complete with their observed periods and distances from our world, and people would be able to find Earth. If we wanted to be found, it was the best idea 1977 had to offer. But 40 years later, the idea is fundamentally flawed. There are up to a billion pulsars in the Milky Way, their periods change long-term, and their orientations are variable over time, meaning they won’t be pointing at Earth in the future. If we wanted to be detected, we’d be much better off sending the same information we use to detect exoplanetary systems today!
Although it was a very clever idea presented just 10 years after the discovery of pulsars, we now know that Voyager’s cosmic map to find Earth will be hopelessly wrong by the time an alien civilization finds it.