Stand on Sedna and the Sun is just a bright star in a black sky, with temperatures around minus 240 degrees Celsius. This episode journeys to one of the loneliest worlds we know, discovered in 2003 at Palomar Observatory by Michael Brown, Chad Trujillo, and David Rabinowitz, who nicknamed it the Flying Dutchman because it crawled across the sky so slowly.

We cover the naming dispute with the International Astronomical Union, why the lack of a moon leaves Sedna’s mass and density unknown, and what the James Webb Space Telescope revealed about its surface of water, methane, ethane, and nitrogen ices coated in reddish tholins. We then tackle the central mystery: an 11,400-year orbit that swings from 76 to 937 astronomical units, too far out to have been scattered by Neptune and too close in to be shaped by galactic tides. We weigh three explanations, a passing star in the Sun’s birth cluster, capture from a passing brown dwarf, and shepherding by a hypothetical Planet Nine, and explain why a mission timed to Sedna’s 2076 perihelion is such a rare opportunity.

• Why Kepler’s third law makes a moon the best scale for weighing a distant world
• How tholins preserve prebiotic chemistry on an undisturbed surface
• The gravitational no man’s land of the inner Oort cloud
• Launch options in 2033 or 2046 plus fusion rocket and solar sail concepts
• The 1-in-80 chance of spotting Sedna and what that implies about hidden worlds