Dark Energy Attracts? Astrophysicists Jason Rhodes and Alina Kiessling

Episode Summary

Executive Summary: This episode weaves together planetary science, policy, and personal discovery: a budget update on NASA funding, eclipse preparation advice, and a deep interview with JPL scientists Jason Rhodes and Alina Kiesling on dark energy, exoplanets, coronagraphs, starshades, Euclid, LSST, and a proposed airship challenge. It closes with Bruce Betts’ skywatching update and eclipse trivia.

Main Topics: NASA budget and Space Policy Edition update: Casey Dreyer explains Senate NASA funding, noting mixed news: some increases for SLS/Orion, but cuts to science and Earth science. The conversation emphasizes that planetary science may ultimately fare better in House-Senate negotiations, though the looming government shutdown deadline is the major concern. Great American Eclipse preparation: Bill Nye urges safe viewing practices, promotes eclipse glasses and Planetary Society resources, and describes his travel to eclipse events at Southern Illinois University and Homestead National Monument. The segment stresses the rarity and accessibility of the 2017 total solar eclipse. Dark energy as a scientific mystery: Jason Rhodes and Alina Kiesling explain dark energy as the name for our ignorance about the accelerating expansion of the universe. They describe how current measurements increasingly resemble a cosmological constant, but the underlying physics remains unknown. Future exoplanet missions: WFIRST, HabEx, coronagraphs, and starshades: The guests outline how WFIRST and future missions aim to directly image exoplanets, use coronagraphs to suppress starlight, and potentially deploy starshades to block stellar light externally. They discuss technical challenges, optical contrast requirements, and the goal of measuring atmospheric biosignatures. Large-scale simulations and mission coordination: Alina discusses n-body and hydrodynamic simulations needed for dark energy surveys such as WFIRST, Euclid, and LSST. A major theme is the need for cross-agency collaboration to share supercomputing resources, simulation pipelines, and analysis methods. Airships as near-space science platforms: The interview introduces a NASA-backed 20-20-20 airship challenge concept: an airship flying at 20 kilometers with a 20-kilogram payload for 20 hours, eventually extending to 200 hours. The goal is to enable stratospheric science for astronomy and Earth observation at lower cost than space missions. Bruce Betts’ skywatching and space trivia: The closing segment covers the Perseids, the total solar eclipse path, the Mars Reconnaissance Orbiter’s launch anniversary, and a trivia question about the Mars-Sun distance difference between perihelion and aphelion.

Key Arguments: NASA’s budget process is unsettled, but the Senate’s proposal is a midpoint compromise and planetary science may recover in final negotiations. Eclipse safety matters because humans instinctively stare at the Sun; proper eclipse glasses are essential for direct viewing. Dark energy is not well understood, but increasingly precise data suggest it behaves like a cosmological constant. WFIRST will not primarily rely on a starshade, but it is being designed to remain compatible with one if NASA later approves such a mission. A starshade’s flower-like shape is necessary to control diffraction and achieve extreme starlight suppression. Direct imaging of Earth-like exoplanets requires dramatically higher contrast than today’s coronagraphs can provide, making HabEx and starshades critical future technologies. Large cosmology surveys depend not just on hardware but on massive simulations and software coordination across NASA, ESA, and DOE projects. Airships could provide long-duration near-space platforms for astronomy and Earth science without the cost and delay of full space missions. Blue-sky research in dark energy may someday produce practical technologies, just as general relativity ultimately enabled GPS. Interagency and international collaboration is central to modern astrophysics, especially for Euclid, WFIRST, and LSST. The romance of science and the romance of a shared scientific career can coexist, even within a married couple working on overlapping missions.

Data Points: NASA budget Senate proposal: $19.5 billion - Senate midpoint between House and White House proposals for NASA FY2018 House NASA proposal: $19.87 billion - Described as the House's stronger number for NASA White House NASA proposal: $19.1 billion - Referenced as the administration's proposal Congressional working days remaining: about 12 working days - Time left to pass a budget before a shutdown deadline WFIRST launch target: mid-2020s, around 2025 - Projected launch window for NASA’s next flagship mission WFIRST telescope aperture: 2.5 meters - Size of WFIRST primary mirror HabEx telescope aperture: about 4 meters - Proposed larger telescope for future exoplanet imaging Starshade diameter for WFIRST: about 30 meters - External occulter concept discussed for WFIRST compatibility Starshade distance for WFIRST: about 30,000 kilometers - Separation from telescope for starshade operation Starshade diameter for HabEx: 72 meters - Larger starshade concept for the Habitable Exoplanet Imaging Mission Starshade distance for HabEx: about 100,000 to 120,000 kilometers - Separation proposed for HabEx observations Internal coronagraph contrast today: about 1,000,000 to 1 - Current state of the art in starlight suppression WFIRST coronagraph contrast goal: about 1,000,000,000 to 1 - Planned performance for WFIRST coronagraph Starshade/coronagraph contrast requirement: about 10,000,000,000 to 1 - Needed to study exoplanets in reflected light in detail Euclid mirror size: 1.2 meters - ESA dark energy mission Euclid sky survey area: 15,000 square degrees - Roughly one-third of the sky over Euclid’s six-year mission Hubble survey comparison: 20 to 30 square degrees - Approximate amount of sky Hubble has surveyed over nearly 30 years LSST camera resolution: 3,200 megapixels (3.2 gigapixels) - Ground-based survey camera discussed in comparison to consumer cameras Typical n-body simulation scale: one trillion particles - Example of current large cosmological simulations Airship challenge payload: 20 kilograms - Part of the 20-20-20 NASA challenge concept Airship challenge altitude: 20 kilometers - Target stratospheric flight altitude Airship challenge endurance: 20 hours initially; 200 hours second stage - Planned challenge milestones Perseid peak: August 12-13 - Annual meteor shower mentioned in What's Up 2017 total solar eclipse date: August 21, 2017 - Great American Eclipse across the United States Mars Reconnaissance Orbiter launch year: 2005 - Space history note in Bruce Betts segment Mars distance difference: 42.5 gigameters - Correct trivia answer for perihelion vs. aphelion distance difference

Pivotal Quotes: "dark energy is what we call our ignorance of what's causing this expanding, accelerating, expanding universe." — Jason Rhodes: Explaining the scientific meaning of dark energy "The flower shape is to allow for a process called diffraction." — Jason Rhodes: Describing why starshades are shaped like a flower "It's a really good question. And one of the things that I will often say when people talk about why do we do this kind of research, I take it back to Einstein's general relativity." — Alina Kiesling: Defending the value of fundamental dark energy research

Implications: The episode underscores how future discoveries about dark energy and exoplanets will depend on precision instruments, shared simulations, and long-term international coordination. It also highlights how near-term public engagement—especially eclipses—helps connect audiences to frontier science.