At the meeting of the Society in November last I mentioned that on the day of the next opposition of the planet Mars, the Earth and Moon, as seen from Mars, would cross the Sun’s disk, a phenomenon which has not happened since the year 1800, and I stated the chief circumstances connected with the … Continue reading Transit Of Earth
At the end of my previous post on this topic, I left you with a diagram of the solar system’s orientation and approximate trajectory in its orbit around the Milky Way galaxy. Below, we’re looking past the solar system towards the galactic core. The plane of the galaxy runs horizontally across the image, north is … Continue reading The Solar System’s Place In The Milky Way: Part 2
As this post goes live, it’s only a few days until an annular solar eclipse, like the one pictured above, will sweep across the Americas on 14 October 2023. Annular eclipses get their name from Latin anulus, “small ring”, which refers to the ring of sunlight that’s visible around the lunar disc, as shown in the image … Continue reading Annular Solar Eclipse
We recently had a blue supermoon (on 31 August 2023). If you saw it, did you think it was super? Me neither. In my previous post, I wrote about blue moons—what they are, why they happen—and in this post I aim to do the same for supermoons. Supermoons happen when a full moon occurs at a … Continue reading Blue Supermoon: Part 2
On 31 August 2023 we’re going to have a blue supermoon, which will be neither particularly blue, nor particularly super, though to read some of the media coverage of these events, you might expect to see something like the image above. So I thought I might write a bit about blue moons (this post) and … Continue reading Blue Supermoon: Part 1
When I wrote recently about the pole stars of other planets, I was aware of one thing my sky maps didn’t show—the rotation poles of our galaxy. They weren’t really relevant to that discussion, but I’m now prompted to write a bit about the Milky Way galaxy, and our relationship to it, because I’ve just … Continue reading The Solar System’s Place In The Milky Way: Part 1
This is, to a large extent, a companion piece to my post about leap seconds, in which I described how the irregular rotation of the Earth means that the time as measured by our atomic clocks would fall out of synchrony with the actual movement of the sun in the sky, were it not for … Continue reading The Advent Of Atomic Time
When I wrote about Philip Latham’s juvenile science-fiction novel Missing Men Of Saturn (1953) recently, I pointed out that Latham had made an astronomically well-informed guess about a possible pole star for Saturn’s moon Titan. Latham (a professional astronomer) knew the orientation of Saturn’s rotation axis, which would have allowed him to deduce the location … Continue reading Pole Stars Of Other Planets?
The “Phenomena” posts have been a little tied up with abstruse orbital mechanics and obscure revisions to lists of Scottish hills, of late, so I thought it might be time for a break from all that. So this post is about something superficially trivial in the film 2001: A Space Odyssey, which has mildly annoyed … Continue reading Which Way Does Space Station V Rotate?
1. All planets move in elliptical orbits, with the sun at one focus.2. A line that connects a planet to the sun sweeps out equal areas in equal times.3. The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit. Kepler’s Laws of Planetary Motion (formulated … Continue reading Keplerian Orbital Elements