7/1/2026 Science with the world’s largest telescopes Dr Katharine Johnston
You may be thinking… Why do we need very large telescopes? If you find yourself thinking that, then you’re in the right place! Regular telescopes can only provide a certain level of detail of astronomical objects. This led scientists to develop very large telescopes to observe supernovas, interstellar dust and supermassive black holes with a much higher resolution (and no, we’re not talking about Oasis, the Christopher Nolan film or Muse).
There are many types of large telescope, some include:
Big optical telescope Big radio telescope Very long baseline interferometry (VLBI) Very long baseline array (VLBA) These all contribute to obtaining higher resolution images that researchers can analyse. An example of a big optical telescope is the Very Large Telescope (VLT), which is 8.2m in diameter and also has four smaller auxiliary telescopes [1], which are smaller, movable telescopes with a diameter of 1.8m each [2]. These telescopes form an interferometer when they’re used together. An interferometer merges sources of light to depict a pattern that cannot be studied any other way because of the small measurements involved [3].
Big radio telescopes are even larger than big optical telescopes so that celestial bodies with a longer wavelength can be studied in the same level of detail. Some examples involve, the Lovell telescope (76m diameter), the Effelsberg telescope (100m diameter) and the FAST (five-hundred-metre Aperture Spherical Telescope) telescope.
(Insert image from seminar of the sky with interstellar dust taken at ALMA)
This image was taken by the ALMA (Atacama Large Millimetre Array) telescope. It is located in the Chajnantor plateau in the Atacama Desert, Chile and is 16500ft above sea level. It is comprised of 66 antennas (dishes of 7m or 12m diameter) which are used together to form one giant telescope or interferometer. As Earth rotates, an aperture is made from the many smaller telescopes (which is where the main lens determines how much light is gathered for the brightness and detail of observed astronomical objects). The black splotches are molecules of interstellar dust. They are a big conglomeration of carbon or silicon-based molecules. When looking with visible light, this dust blocks the light by absorbing or scattering the A solution to this problem is observing the same image at a longer wavelength. Wien’s law states that if something is emitting thermally, then it must be a black body, which means that everything it absorbs, remains.
The world’s largest telescope is called the Event Horizon telescope (which is also one of the largest interferometers) with a maximum baseline of 10700km. A baseline is the distance between two telescopes in an interferometer. It combines many different telescope facilities from across the world (including ALMA). Wavelengths that can be observed are between 1.3mm and recently, 0.87mm, which is useful for obtaining higher resolution images using the VLBI technique. The very long baseline interferometry technique stores the data on disks and ship the information to supercomputers at MIT and Max Planck Institute for Radio Astronomy in Germany. The supermassive blackholes at the centre of our galaxy (the Milky Way) and at the centre of M87* (which is a star in another galaxy) were able to be analysed by this telescope to deduce that lens rings are common features of black holes, magnetic fields are dynsmicslly important for black holes, and how to find angular momentum of black holes.
In order to understand the universe, very large telescopes are extremely important as they allow scientists to observe celestial bodies clearly and in greater detail than they would be able to otherwise. Interferometry has allowed astronomy to be revolutionised by having several telescopes be used as one Earth-sized telescope.
References:
[1] information@eso.org, “Very Large Telescope,” www.eso.org. https://www.eso.org/public/unitedkingdom/teles-instr/paranal-observatory/vlt/
[2] information@eso.org, “Auxiliary Telescopes - Very Large Telescope Interferometer,” Eso.org, 2025. https://www.eso.org/public/unitedkingdom/teles-instr/paranal-observatory/vlt/auxiliarytelescopes/ (accessed Jan. 07, 2026).
[3] LIGO Caltech, “What is an Interferometer?,” LIGO Lab | Caltech, 2019. https://www.ligo.caltech.edu/page/what-is-interferometer
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Presentation: 13/15
You have followed the criteria of including the speaker’s name, title and date of the seminar, shown clearly at the start of the blogpost.
Content: 14/15
Conveyed the mechanisms behind ALMA array by summarising the majority of the content in the Katharine ‘s seminar.
Context: 13/15
Provided good background on why radio waves are used to see through interstellar dust.
Style: 13/15
It is persuasive to read due to the immediate hook of the rhetorical question and use of concepts that are common knowledge in the opening paragraph. As well as the blogpost explains concepts that are foreign to general public in relatively simple terminology, i.e. Wein’s law
Other sources: 15/15
Referenced additional sources for readers to explore for the factuality of the blogpost content.
Overall Mark: 14/15
Feedback:
Misspelt dynamically ,“dynsmicslly ”, the bullet point list needs a spacing with the following paragraph possibly expand on why the ALMA has such a high altitude.
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- Blog overall presentation (2/3)
The key information is included, a few minor spelling mistakes and the layout seems a little blocky
- Accurate reporting of the seminar’s take-home message (3/3)
A lot of the general and technical is covered to a good standard
- Accurate contextualisation of the research topic (3/3)
The research topic of the seminar is covered very well
- Additional assessment using external sources with a direct quote (3/3)
Good variety of sources for an in-depth further reading
- Writing style and technical level for a lay audience (2/3)
For a lay audience the writing style is good, but again the whole thing seems a little bit blocky. Perhaps smaller sections/paragraphs could help