science

NGC 6401

NGC 6401 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 NGC 6401 rather than just read about it. In short: NGC 6401 is a globular cluster in the equatorial constellation of Ophiuchus. This star cluster was discovered by German-English astronomer William Herschel in 1784, but he mistakenly classified it as a bright nebula.

Key takeaways

NGC 6401 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NGC 6401 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 6401 from memory before moving on to harder problems.

Reference excerpt

NGC 6401 is a globular cluster in the equatorial constellation of Ophiuchus. This star cluster was discovered by German-English astronomer William Herschel in 1784, but he mistakenly classified it as a bright nebula. Later, his son John Herschel came to the same conclusion because the technology of the day did not allow the individual stars to be visually resolved. It is visible in a small telescope, with an apparent visual magnitude of 7.4 and an angular diameter of 4.8′. This cluster is located at a distance of 25.1 kly (7.70 kpc) from the Sun and is orbiting in the galactic bulge, in the inner part of the Milky Way galaxy. Because of its high mass, it may be gravitationally trapped inside the Milky Way's bar. From the perspective of the Earth, this cluster is situated 5.3° from the Galactic Center and is strongly reddened due to extinction from interstellar dust. NGC 6401 is a very old cluster with an estimated age of 13.2±1.2 Gyr, but has not undergone core collapse. It has a cluster radius of 2.4′. 23 class ab and 11 class c RR Lyrae variables have been identified within a cluster radius of the core. From this, it is deduced that this is an Oosterhoff type I (Oo I) cluster. During the June 2011 lunar eclipse, a Total Lunar Eclipse, it was occulted by the Moon over Europe, North Africa and Southwest Asia. This will happen again during the June 2076 lunar eclipse over Eastern North America, Cuba, the Atlantic Ocean, Southeast Europe and the northern half of Africa.

References

External links Media related to NGC 6401 at Wikimedia Commons NGC 6401 SEDS.org (Revised NGC) NGC 6401 NASA Extragalactic Database

Illustrations

Worked examples

Example 1 — a first encounter with NGC 6401

Start with the simplest possible case. Write down what NGC 6401 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 NGC 6401 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 NGC 6401 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 NGC 6401

In research: NGC 6401 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 NGC 6401 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: NGC 6401 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Globular clusters, NGC objects, Ophiuchus, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 6401 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 NGC 6401 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 6401 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 NGC 6401 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 6401 in simple terms?

Why does NGC 6401 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 NGC 6401?

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 NGC 6401.