astronomy

James Clerk Maxwell Telescope

James Clerk Maxwell Telescope is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand James Clerk Maxwell Telescope rather than just read about it. In short: The James Clerk Maxwell Telescope (JCMT) is a submillimetre-wavelength radio telescope at Mauna Kea Observatory in Hawaii, US. The telescope is near the summit of Mauna Kea at 13,425 feet (4,092 m).

Key takeaways

James Clerk Maxwell Telescope belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect James Clerk Maxwell Telescope to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of James Clerk Maxwell Telescope from memory before moving on to harder problems.

Reference excerpt

The James Clerk Maxwell Telescope (JCMT) is a submillimetre-wavelength radio telescope at Mauna Kea Observatory in Hawaii, US. The telescope is near the summit of Mauna Kea at 13,425 feet (4,092 m). Its primary mirror is 15 metres (16.4 yards) across: it is the largest single-dish telescope that operates in submillimetre wavelengths of the electromagnetic spectrum (far-infrared to microwave). Scientists use it to study the Solar System, interstellar dust and gas, and distant galaxies. The JCMT started operations in 1987, and was funded until February 2015 by a partnership between the United Kingdom and Canada, and the Netherlands. It was operated by the Joint Astronomy Centre and was named in honour of mathematical physicist James Clerk Maxwell. In March 2015 the operation of the JCMT was taken over by the East Asian Observatory. Funding is provided by the National Astronomical Observatory of China, National Astronomical Observatory of Japan, Korea Astronomy and Space Science Institute, and the Academia Sinica Institute of Astronomy and Astrophysics of Taiwan. The telescope was combined with the Caltech Submillimeter Observatory next to it to form the first submillimetre astronomical interferometer. This success was important driving the construction of the later Submillimeter Array and the Atacama Large Millimeter Array (ALMA) interferometers. In recent years the JCMT has also taken part in Event Horizon Telescope observations, which produced the first direct image of a black hole. The JCMT was also involved in the discovery of phosphine, a potential biomarker, in the atmosphere of Venus.

History In the late 1960s, the Astronomy Committee of the UK's Science Research Council (SRC, the forerunner of STFC) considered the importance of astronomical observations at submillimetre and millimetre wavelengths. After a series of proposals and debates, in 1975, the SRC millimetre steering committee concluded that it would be possible to construct a 15-metre diameter telescope capable of observing at wavelengths down to 750–800 μm. The project, then called the National New Technology Telescope (NNTT), was to be an 80/20 per cent collaboration with the Netherlands Organisation for the Advancement of Science. Site tests were made at Mauna Kea in Hawaii, the Pinaleno Mountains in Arizona, and a site in Chile; and Mauna Kea was chosen. The NNTT was to be larger and with more instruments than competing telescopes such as the CSO and SMT. The final specifications called for the "world's largest telescope optimised for submillimetre wavelengths". It was to be a parabolic 15-metre antenna composed of 276 individually adjustable panels with a surface accuracy of better than 50 μm. It would be an altitude-azimuth mounted Cassegrain telescope with a tertiary mirror to direct the incoming radiation onto a number of different receivers. The antenna and mountings were to be protected from the elements by a co-rotating carousel with a transparent membrane stretched across the carousel aperture. Building work started in 1983 and went well. In 1984, the telescope was shipped from England to Hawaii. After the original shipper broke down at the last minute, the telescope was given to a commercial captain who was supposed to deliver it directly to Hawaii. Instead, the captain sailed to Holland to pick up a shipment of explosives, then was delayed at the Panama Canal, allegedly because special clearance was needed to transport the explosives through the canal. The captain then delivered the explosives to Ecuador before finally reaching Hawaii. Waiting just outside of territorial waters, the captain demanded that the late delivery charges—now almost equal to that of the shipping charges—be waived, and threatened to throw the telescope overboard if his demand was not met. The telescope team was able to get a court order to give up the board, and the ship was subsequently boarded and the captain arrested at gunpoint by the Coast Guard. The telescope saw first light in 1987. The name for the final facility was changed to the James Clerk Maxwell Telescope. The telescope itself was operated by the Joint Astronomy Centre (JAC), from Hilo, Hawaii. From 1987 until March 2013 the telescope was funded by a partnership of the United Kingdom (55 per cent), Canada (25 per cent), and the Netherlands (20 per cent). In 2013 the Netherlands withdrew, and until 2015 the shares became UK 75 per cent, Canada 25 per cent. In March 2015, the UK and Canada handed over ownership of the JCMT to the East Asian Observatory, which is funded by Japan, China, Taiwan and South Korea, together with a consortium of Universities from the United Kingdom and Canada.

Instrumentation

The JCMT has two kinds of instruments: broadband continuum receivers and heterodyne detection spectral line receivers. Continuum emission is a tracer of star formation in other galaxies and gives astronomers clues to the presence, distance, and evolution history of galaxies other than our own. Within our own galaxy dust emission is associated with stellar nurseries and planet forming star systems. Spectral-line observations can be used to identify particular molecules in molecular clouds, study their distribution and chemistry and determine gas velocity gradients across astronomical objects (because of the doppler effect).

SCUBA

The older continuum single pixel UKT14 bolometer receiver was replaced around 1995 by the Submillimetre Common-User Bolometer Array (SCUBA). This instrument operated simultaneously at wavelengths of 450 and 850 micron (with 91 and 37 pixels, respectively), and was sensitive to the thermal emission from interstellar dust. SCUBA was a ground-breaking instrument, among the most high-impact astronomy instruments from 1997 to 2003; it was retired from service in 2005, and is now in the National Museum of Scotland.

SCUBA-2 SCUBA was succeeded by SCUBA-2, which was commissioned in 2011. This ground-breaking camera consists of large arrays of superconducting transition edge sensors with a mapping speed hundreds of times larger than SCUBA. It has 5120 array elements at both 450 and 850 micron wavelength (10,240 total pixels). It has been conducting the JCMT legacy surveys since November, 2011, including the SCUBA-2 All Sky Survey, and was made available for general astronomical observations in February, 2012. Two ancillary instruments, FTS-2 and POL-2, add spectroscopic and polarimetric capabilities to SCUBA-2.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with James Clerk Maxwell Telescope

Start with the simplest possible case. Write down what James Clerk Maxwell Telescope claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to James Clerk Maxwell Telescope before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about James Clerk Maxwell Telescope ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of James Clerk Maxwell Telescope

In research: James Clerk Maxwell Telescope appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses James Clerk Maxwell Telescope in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: James Clerk Maxwell Telescope is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical observatories in Hawaii, Astronomy in the United Kingdom, Buildings and structures in Hawaii County, Hawaii, so understanding it makes those chapters shorter.
In everyday life: Look for James Clerk Maxwell Telescope outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study James Clerk Maxwell Telescope in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what James Clerk Maxwell Telescope means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain James Clerk Maxwell Telescope out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is James Clerk Maxwell Telescope in simple terms?

The James Clerk Maxwell Telescope (JCMT) is a submillimetre-wavelength radio telescope at Mauna Kea Observatory in Hawaii, US. The telescope is near the summit of Mauna Kea at 13,425 feet (4,092 m).

Why does James Clerk Maxwell Telescope matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study James Clerk Maxwell Telescope?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on James Clerk Maxwell Telescope.