The Solar Probe: Time to Go Deeper Into the Sun Than Ever Before

On the solar probe, the Sun, and what it has told us.

This is an article for paid subscribers. Thank you for your support this year! I wish you all a Merry Christmas, a happy New Year, and a wonderful start to 2025.

---

Parker approaching the Sun, as imagined by an artist. Image credit: NASA/Johns Hopkins APL/Steve Gribben

On Christmas Eve the Parker Solar Probe will make its closest approach to the Sun. There isn’t anything deliberate about this date: Parker’s other close approaches are scattered across the calendar, timed more by the motions of the stars and planets than by any desire for symbolism. It is just coincidence, in all likelihood, but there we have it anyway.

The details of the approach are impressive. On December 24th Parker will fly less than six million kilometers, or four million miles, from the surface of the Sun. At the same time it will briefly become the fastest moving object ever built by humanity, traversing two hundred kilometres in a single second.

Such numbers are hard to grasp, but for a moment let’s try. At this speed, equal to 700,000kph or 430,000mph, Parker could travel from New York to London in twenty-nine seconds flat, reach Tokyo less than a minute later and then go on to the Moon before half an hour had passed.

Even so, this speed can be made to look slow. Parker will reach just a twentieth of one percent of the speed of light, showing that despite being the fastest thing ever built, we have an awful lot of room to go faster. Sadly, nothing seems likely to do so soon. Parker’s Christmas Eve record will certainly stand for the next few decades at least.

Neither will any other probe venture closer to the Sun in the foreseeable future. Doing so is hard. The Sun is hot, emits intense radiation, and sits at the bottom of a deep gravity well. Getting there is difficult, surviving once you do is even harder. You really need, in other words, a good reason to go there at all.