Show Notes
About This Episode
The poster on every classroom wall shows eight planets arranged neatly around the Sun, with a clear edge at Neptune. It is one of the most widely reproduced images in science education, and it is, in important ways, wrong. The solar system does not end at Neptune. Its gravitational reach extends halfway to the nearest star. 99.9% of its mass is the Sun. Pluto's demotion happened not because it shrank but because we kept discovering new objects and realised the definition of a planet had never been precise enough.
Mads Fredslund Andersen is a telescope and satellite manager at the Department of Physics and Astronomy at Aarhus University in Denmark. He manages a network of telescopes distributed across three continents and works on the satellite side of space research, including a student cube satellite designed to photograph Greenland's glaciers from orbit. His day-to-day work sits at the intersection of what we can observe and what the observations tell us about the structure of the universe we live in.
In this episode, Mads and Mikkel Svold take a close look at our own neighbourhood. They cover how the solar system formed from a collapsing gas cloud, why the boundary of the solar system is genuinely hard to define, how Jupiter protects Earth from incoming asteroids, why Pluto lost its planet status, and what excites Mads most about the next generation of solar system exploration: manned Mars missions and the ice moons of Jupiter and Saturn, where liquid water beneath the ice may be the most promising place to look for life beyond Earth.
In This Episode
- Why the standard poster of the solar system is misleading and where the real boundary lies
- How 99.9% of all the material in the solar system is concentrated in the Sun
- How the solar system formed from a rotating gas cloud, and why the planets did not fall into the Sun
- Why Jupiter's gravity plays a significant role in deflecting asteroids and comets away from Earth
- How scientists determine what is inside planets they cannot probe directly
- Why Pluto was reclassified as a dwarf planet, and what the "cleared orbit" definition actually means
- Whether the solar system is unusual, and what exoplanet discoveries since 1995 have shown
- What Mads is most looking forward to: manned Mars missions and the ice moons of the outer planets
Chapters
- What Mads does as a telescope and satellite manager
- What is the solar system and where does it end
- The Oort Cloud and the problem of defining boundaries
- How the solar system formed
- What is inside planets, and how we know
- Jupiter as Earth's protector
- Pluto's demotion and the planet definition
- Is the solar system unique
- Future exploration: Mars and the ice moons
Key Quotes
"Most of the stuff, it's 99.9% of the whole material in the solar system is in the Sun."
"It's a fairly vague way of defining where it is."
"Jupiter, the largest of the planets in the solar system, is somehow protecting against the inward coming asteroids and comets."
"I hope in my lifetime that we will have man missions to Mars. That will be amazing."
About Mads Fredslund Andersen
Mads Fredslund Andersen is a telescope and satellite manager at the Department of Physics and Astronomy at Aarhus University in Denmark. He oversees a network of robotic telescopes located in Tenerife, China, and Australia, as well as satellite projects including a student cube satellite designed to monitor climate changes in Greenland from orbit. His work connects ground-based telescope observation with space-based data collection, and he is involved in collaborations with major NASA satellite missions.
Resources Mentioned
- Aarhus University Department of Physics and Astronomy — Mads Fredslund Andersen's research page
- NASA missions to Mars — information on Mars rovers and the ongoing Mars exploration programme
Contact and Follow
Questions, topic ideas, or guest suggestions: [podcast contact email]
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