astronomy

Messier 19

Messier 19 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 Messier 19 rather than just read about it. In short: Messier 19 or M19 (also designated NGC 6273) is a globular cluster in the constellation Ophiuchus. It was discovered by Charles Messier on June 5, 1764 and added to his catalogue of comet-like objects that same year.

Key takeaways

Messier 19 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Messier 19 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 19 from memory before moving on to harder problems.

Reference excerpt

Messier 19 or M19 (also designated NGC 6273) is a globular cluster in the constellation Ophiuchus. It was discovered by Charles Messier on June 5, 1764 and added to his catalogue of comet-like objects that same year. It was resolved into individual stars by William Herschel in 1784. His son, John Herschel, described it as "a superb cluster resolvable into countless stars". The cluster is located 4.5° WSW of Theta Ophiuchi and is just visible as a fuzzy point of light using 50 mm (2.0 in) binoculars. Using a telescope with a 25.4 cm (10.0 in) aperture, the cluster shows an oval appearance with a 3′ × 4′ core and a 5′ × 7′ halo. M19 is one of the most oblate of the known globular clusters. This flattening may not accurately reflect the physical shape of the cluster because the emitted light is being strongly absorbed along the eastern edge. This is the result of extinction caused by intervening gas and dust. When viewed in the infrared, the cluster shows almost no flattening. It lies at a distance of about 28.7 kly (8.8 kpc) from the Solar System, and is quite near to the Galactic Center at only about 6.5 kly (2.0 kpc) away. This cluster contains an estimated 1,100,000 times the mass of the Sun and it is around 11.9 billion years old. The stellar population includes four Cepheids and RV Tauri variables, plus at least one RR Lyrae variable for which a period is known. Observations made during the ROSAT mission failed to reveal any low-intensity X-ray sources.

Illustrations

Worked examples

Example 1 — a first encounter with Messier 19

Start with the simplest possible case. Write down what Messier 19 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 Messier 19 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 Messier 19 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 Messier 19

In research: Messier 19 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 Messier 19 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: Messier 19 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1764, Discoveries by Charles Messier, Globular clusters, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 19 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Messier 19 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 19 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 Messier 19 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 19 in simple terms?

Why does Messier 19 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 Messier 19?

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 Messier 19.