science

PKS 1830−211

PKS 1830−211 is a science 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 PKS 1830−211 rather than just read about it. In short: PKS 1830−211 is a gravitationally-lensed blazar in the southern constellation of Sagittarius, one of the most powerful such objects known. It has a high redshift (z) of 2.507, an indicator of its significant distance.

Key takeaways

PKS 1830−211 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PKS 1830−211 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PKS 1830−211 from memory before moving on to harder problems.

Reference excerpt

PKS 1830−211 is a gravitationally-lensed blazar in the southern constellation of Sagittarius, one of the most powerful such objects known. It has a high redshift (z) of 2.507, an indicator of its significant distance. This flat-spectrum radio quasar (FSRQ) is one of the brightest extraterrestrial radio sources. In visible light, identification of this object is hampered by the galactic plane and an M-type star that lies near the line of sight. This quasar was first detected in 1969 during a radio survey by the Parkes Observatory in Australia. In 1984, it was found to display interplanetary scintillation, suggesting structure on angular scales of less than an arc second. Radio observations in 1988 found an unusual double structure separated by an angle of ~1 arc second. The flat radio spectrum and double structure of this feature are suggestive of gravitational lensing by a foreground galaxy. Interferometric radio telescope observation was used to detect an unusually bright Einstein ring in 1991, spanning a radius of 1″. Radio observations of PKS 1830−211 made over a 13-month period were used to measure changes in flux density. Both components displayed dramatic changes in their flux level, with the fluctuation on one component matched by the other about 44 days later. This lent strong support to the idea this is a gravitationally lensed system. The time delay was refined to 26+4−5 days in 1998. In 1996, absorption of neutral hydrogen was detected at a redshift of 0.19, suggesting a possible second lensing galaxy for a compound gravitational lens. This object was confirmed via infrared imagery in 2005. However, this second galaxy is thought to have a negligible effect on the overall lensing. Imaging of the quasar with the Hubble Space Telescope in 2002 identified the lens galaxy as a normal spiral galaxy at a redshift of 0.886. It is inclined at an angle of 25° to the plane of the sky, appearing nearly face-on. Based on the size of the Einstein ring, this galaxy has a mass of about 1011 M☉, which is comparable to the Milky Way. An independent analysis of the same imaging data suggested the possible presence of a main-sequence star within 0.5″ of the target. A third point-like lensed image of the quasar was detected in 2020, located part way between the other two. PKS 1830−211 is a source for gamma-ray emission that undergoes significant flaring. PKS 1830−211 has been used as a radio source for measuring redshifted molecular species, including ArH+, CF+, HCN, HCO+, H2O, NH3, and OH+. As of 2014, it is the "extragalactic object with the largest number of detected molecular species". In 2023, Rydberg atoms were detected in the foreground galaxy by the MeerKAT telescope array.

References

Illustrations

Worked examples

Example 1 — a first encounter with PKS 1830−211

Start with the simplest possible case. Write down what PKS 1830−211 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 PKS 1830−211 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 PKS 1830−211 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 PKS 1830−211

In research: PKS 1830−211 appears in science 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 PKS 1830−211 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: PKS 1830−211 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Quasars, Sagittarius (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for PKS 1830−211 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 PKS 1830−211 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PKS 1830−211 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 PKS 1830−211 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PKS 1830−211 in simple terms?

Why does PKS 1830−211 matter?

Because it connects several science 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 PKS 1830−211?

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 PKS 1830−211.