May 10th 2026

Things from Today:

• The Proper Motion of Wolf 359 - See figure and text below.

• Red Dwarf Stars - After showing us the comparison picture of Wolf 359 (below), Peter told us more about Red dwarf stars (of which Wolf 359 is one example). Red dwarfs are the most common type of star in our own galaxy - accounting for around 70% of all stars in the Milky Way. These stars are much smaller than our own sun, ranging from roughly 8% to 60% of the sun's mass. Due to their small size, they are able to continually 'stir' the hydrogen in their outer layers back into their core, thus maintaining nuclear fusion for (in some cases) many trillions of years longer than our own sun will burn. Peter also told us about the questions around the habitability of planets orbiting red dwarfs, due to the tendency of these stars to produce very frequent and very strong solar flares (propelled by their intense magnetic fields).

• Neutrino Oscillations - We had a brief conversation about neutrino oscillations and lepton flavour violation. Presently, physicists have not observed any interactions that leads to charged leptons changing their flavour (e.g. a muon decalying into an electron plus a photon). However... we observe neutrinos (un-charged leptons) changing their flavour very frequently. There are a number of 'beyond the standard model' theories that predict these flavour changing interactions of the charged leptons, but so far none have been seen.

• Water on Mercury - We discussed the interesting (and perhaps surprising) existence of water ice on the surface of Mercury. This is surprising, as Mercury is so close to the sun that it's day-time temperature can exceed 430 degrees celsius (more than hot enough to boil away any water). However... Mercury has a number of deep craters located at it's north and south poles that are in perpetual shade. As Mercury has no atmosphere of any significance, the extreme heat of its daylight regions does not transfer to these shaded craters. The existence of water ice in these polar craters was confirmed by the NASA MESSENGER spacecraft in 2012.

• Tidal Locking - We discussed the feature of orbital mechanics that leads to many orbiting bodies (such as the Earth and the Moon) becoming 'tidally locked'. The Moon is already tidally locked to the Earth, which means the Moon only ever shows us one side of itself. Technically speaking... the Earth is also very slowly becoming tidally locked to the Moon - although, this process will take far longer than the 5 billion year life span of the sun will allow! (I got these numbers wrong today - I did not realise that this process would take nearly 50 billion years to complete!).

Extra Reading:

• [Article] What Causes Lightning? The Answer Keeps Getting More Interesting - C Wood (Quanta Magazine)

• [Article] How do you define a Planet? - K Howells (The Planetary Report)

Extra Watching / Listening:

• [Podcast] Scotohylology (DARK MATTER) with Dr. Flip Tanedo - Alie Ward (Ologies Podcast)

• [Video] The Hidden Galaxy (Caldwell 5 or IC 342) - DeepSkyVideos

Homework

This 'homework' is recurring, and one I like to set my own students (and try to stick to myself!):

1. Learn something new everyday.

2. Share what you know with someone else.

3. Look at the world and "think like a Martian".

If you learn something interesting, I would love to hear about it! Tell me about it next time or drop me an email!

spacetime-sundays@science-on-sea.com