There is a summary of the key characteristics of astronomical telescopes in a previous post, at https://physbang.com/2026/03/15/a-level-guide-to-astronomical-telescopes/. This article builds on that general overview by explaining a specific skill; how to draw a ray diagram for a refracting telescope in normal adjustment. First, what is "normal adjustment"? It is when the objective and eyepiece lenses … Continue reading Ray Diagram for a Telescope in Normal Adjustment
The formation, life and death of stars
All stars are born through the same basic mechanism but their evolution depends on their size. In particular, all stars go through a hydrogen-fuel stage but the time spent fusing hydrogen is determined by the star's initial mass. The final fate of a star is also predicted by its mass; some stars will simply fade … Continue reading The formation, life and death of stars
Classification of Stars
The obvious way to classify stars is by their appearance; how bright they are and their colour. In both cases, we are referring to properties judged using the human eye from the location of planet Earth. Sadly, our eyes are not a good judge of colour (equal amounts of red and green light are perceived … Continue reading Classification of Stars
Kepler: Greater than Copernicus
Copernicus is generally credited with having first described the “true” arrangement of the solar system at a time when Science was being reborn after the Dark Ages. So revolutionary was his book De Revolutionibus that he withheld it for more than 10 years before finally publishing a small number of copies in 1543. As he … Continue reading Kepler: Greater than Copernicus
Mammoth effort to image our galaxy in infra-red
Astronomers working on the European Southern Observatory's (ESO's) Visible and Infra-Red Telescope for Astronomy (VISTA) have today published the biggest ever dataset of infra-red images of the Milky Way. A few of the images captured by the ESO VISTA project. Full details about this composite can be found at https://www.eso.org/public/images/eso2413a/ Importantly, capturing images using infra-red … Continue reading Mammoth effort to image our galaxy in infra-red
The coldest exoplanet ever seen
Most exoplanets (planets that are outside the Solar System) are detected indirectly. Either a temporary and regular dimming is measured as they pass in front of the host star or their orbit causes a wobble that produces a periodic red-shift in the star's spectrum. Only a small number of planets have then gone on to … Continue reading The coldest exoplanet ever seen
Astronomy versus Cosmology
The word "astronomy" means the arrangement of the stars but we apply it to the arrangement of the entire Universe, not just stars. It is an observational science, since experiments are difficult to perform on solar systems and galaxies - let alone the entire Universe. Cosmology, on the other hand, is more philosophical and is … Continue reading Astronomy versus Cosmology
BBC Bitesize – Paper 1 Revision
November's trial examination will include everything in Paper 1. This means everything that was due to be covered in Y10 - and that in turn means a fair amount of content that you had to study at home during the lockdown. Now you are about to be tested on what you know and it is … Continue reading BBC Bitesize – Paper 1 Revision
Home Study Projects
Constantly going over things that you have already learned can get a bit boring so if you want to extend your knowledge over the summer holiday then it's a good idea to do so using some fresh material. Finding suitable resources can be tricky so let me suggest some materials that are provided online at … Continue reading Home Study Projects
Black Holes
In our course, we cover Black Holes only as the final product of a collapsed super-massive star but if you want to know more about these fascinating objects then I highly recommend the ten-minute video by Perimeter Institute. To view the video, go to https://www.youtube.com/watch?v=TfdviKnUZOA&list=PL1608DAAD37A04B35 The same collection of videos also has a great six-minute … Continue reading Black Holes
Mr Tarrant's physbang 'blog 