This Q&A session addresses a range of astronomical questions. Topics include the formation of spiral arms in protoplanetary discs, the ongoing selection process for the Artemis 3 lunar landing site near the Moon's south pole, and the minimum size for a star, identified as red dwarfs at about 7.5% of the Sun's mass. The discussion extends to practical advice on building a Dobsonian telescope, including the possibility of grinding one's own mirror. More speculative questions cover the potential for advanced civilizations to accidentally create black holes and the nature of gas giant cores, specifically Jupiter's metallic hydrogen core and gradual density increase. The host also shares recommendations for current science fiction media.
Cosmic Queries Answered: Protoplanetary Discs, Star Sizes, Lunar Landings, and More
The Atacama Large Millimeter/submillimeter Array (ALMA) has captured images showing that protoplanetary discs can indeed form spiral arms, similar to galaxies, due to comparable gravitational forces.
These discs show surprising diversity and are often smaller than anticipated, with many being smaller than Jupiter's orbit, suggesting our solar system might be unusually large for its star type.
The exact landing site for Artemis 3 near the Moon's south pole is still undecided, but NASA is using AI and machine learning to evaluate about a dozen potential locations.
Criteria include terrain (rocks, slopes), sunlight availability, proximity to permanently shadowed craters (containing water ice), resource availability, scientific interest, and communication links with Earth. A decision is anticipated within a year (from the recording date of late April 2025).
The smallest stars capable of fusing hydrogen are red dwarfs (M-dwarfs), which can be about 7.5% the mass of the Sun, or roughly 75-80 times the mass of Jupiter.
These stars are long-lived (trillions of years), fully convective (allowing them to use more of their fuel), and significantly smaller in diameter than the Sun (e.g., 70,000-350,000 km vs. the Sun's 1.5 million km).
Building a Dobsonian telescope (e.g., a 150mm/6-inch model) is highly recommended for those with time and resources, especially where commercial options are expensive.
Dobsonians are simple, "light bucket" telescopes offering great views for their cost. They typically feature a tube, a primary mirror, secondary optics, and a simple alt-azimuth mount.
DIY options range from using pre-made mirror parts to grinding your own mirror from a blank, a process that teaches a lot about optics.
While excellent for visual astronomy, the standard alt-azimuth mount makes astrophotography and automated tracking more challenging but not impossible to modify.
00:13:12 Artificial Black Holes as a "Great Filter":
While natural black holes form from massive star implosions, it's theoretically possible for advanced civilizations to create micro black holes (e.g., with future particle colliders, though current ones like LHC cannot).
If such an artificial black hole didn't evaporate, it could pose a danger by consuming its parent planet. However, the vast number and mass of observed black holes are consistent with natural formation.
Gas giants like Jupiter do not have a solid surface you could land on. Instead, they feature a gradual transition in density, pressure, and temperature.
Jupiter's core likely contains 15-30 Earth masses of "metals" (elements heavier than helium).
Under immense pressure and temperature, hydrogen deep within Jupiter becomes "metallic hydrogen," a fluid conductor responsible for its strong magnetic field. This metallic hydrogen is denser than iron but behaves like a liquid.
The transition from the outer cloud tops (gaseous, ~70km deep) to the super-dense, super-hot core (90,000Β°C) is a smooth gradient with no distinct "surface."