Starchaser: Extraordinary Astronomer Jay Pasachoff

Episode Summary

Executive Summary: This episode pairs a LightSail 2 launch update with an extended conversation with astronomer Jay Pasachoff about eclipses, solar physics, astronomy history, and science communication. Pasachoff discusses his work on the Sun, the coming Chile eclipse, the Hubble tension, gravitational waves, and how art, literature, and historical texts deepen public understanding of astronomy.

Main Topics: LightSail 2 launch and mission upgrades: Jason Davis explains that LightSail 2 has arrived in Florida for integration and imminent launch, and details the differences from LightSail 1: a higher orbit for solar sailing, added momentum wheel, and laser retroreflectors for precise tracking. Solar sailing and spacecraft navigation: The conversation explains why LightSail 2 must fly higher than ISS-like low Earth orbit to reduce atmospheric drag and allow sunlight pressure to measurably change the orbit, plus how torque rods and momentum wheels control orientation. Jay Pasachoff’s eclipse career and Chile expedition: Pasachoff describes a lifetime of eclipse observing, his upcoming 35th total solar eclipse and 71st eclipse overall, and preparations for the July 2 total eclipse in Chile with NSF-funded research teams. Solar corona research and the Parker Solar Probe: Pasachoff explains how eclipse observations complement Parker Solar Probe data, especially for understanding coronal temperatures, magnetic structures, and competing heating theories like nanoflares and wave motions. Astronomy’s evolving big questions: Hubble constant and gravitational waves: Pasachoff highlights the growing tension between Hubble constant measurements from Planck and supernova methods, and the importance of LIGO’s gravitational-wave detections, now frequent enough to reshape textbooks. Astronomy in history, art, and literature: The discussion ranges from Whitman’s poem to rare books by Galileo, Copernicus, and Kepler, and Pasachoff’s collaboration with art historian Roberta Olson on a book connecting astronomy with visual art.

Key Arguments: LightSail 2 must fly in a higher orbit because atmospheric drag in low Earth orbit would otherwise overwhelm the small solar-sail thrust. A single momentum wheel is needed on LightSail 2 because rotating a deployed sail requires stronger attitude-control capability than LightSail 1 had. Retroreflectors on LightSail 2 enable precise ground-based laser ranging, which is essential for detecting tiny orbit changes caused by solar sailing. Pasachoff argues eclipses remain scientifically valuable because they let researchers measure coronal structure, temperatures, and dynamics that are otherwise hard to observe. He emphasizes that the Sun’s corona-heating problem is not solved by one theory; multiple competing explanations still need discrimination through observations. The Hubble constant discrepancy is now serious enough that it may require revisions to early-universe cosmology rather than being a simple measurement error. General relativity’s eclipse-based confirmation in 1919 remains one of astronomy’s most consequential public and scientific milestones. Pasachoff argues that understanding science history, art, and literature increases rather than decreases appreciation of the night sky and astronomy.

Data Points: LightSail 2 launch date: June 22 - Projected launch date discussed by Jason Davis LightSail 2 launch time: 11:30 PM - Night launch window for the Falcon Heavy Target orbit altitude: about 720 km - Chosen to reduce atmospheric drag enough for measurable solar sailing Approximate drag threshold for sailing: around 700 km - Pasachoff and Davis note solar sailing becomes effective near this altitude ISS orbit altitude: about 500 km - Used as comparison for atmospheric drag in low Earth orbit Total solar eclipses observed by Pasachoff: 35 - He says the Chile eclipse will be his 35th total eclipse All solar eclipses observed by Pasachoff: 71 - Includes total, annular, and partial eclipses Upcoming eclipse date: July 2 - Total solar eclipse observation planned in Chile NSF grant duration: 3 more years - Funding confirmed for Pasachoff’s eclipse research Corona temperature diagnostic ions: iron XIII and iron X - Spectral lines used to compare hotter and cooler coronal regions Solar wind speed: 250 to 750 km/s - Bruce Betts’ random space fact NASA administrators who served more than once: 2 - James C. Fletcher and Alan Lovelace were named as repeat administrators LIGO event rate: a couple of events a week - Pasachoff notes the detectors are now seeing frequent detections Eclipse 2017 attendance example: 16,000 people - Pasachoff recalls observing the 2017 eclipse in Carbondale, Illinois Solar rotation control turns: two 90-degree turns each orbit - LightSail 2 uses momentum wheel control to rotate the sail

Pivotal Quotes: "I’m an eclipse proceeder." — Jay Pasachoff: His preferred alternative to being called an eclipse chaser "To go to a partial eclipse is like going to the ticket booth, but not seeing the game." — Jay Pasachoff: He explains why totality matters scientifically and experientially "For me and many people like me, knowing in more detail what the sky is like really adds enjoyment." — Jay Pasachoff: He defends the value of science in enhancing appreciation of the heavens

Implications: The episode shows how incremental spacecraft design, precise measurements, and long-term eclipse science drive both exploration and fundamental physics. It also argues that astronomy’s appeal grows when linked to history, art, and public communication.