astronomy

Messier 47

Messier 47 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 47 rather than just read about it. In short: Messier 47 (M47 or NGC 2422), also known as NGC 2478 is an open cluster in the southern constellation of Puppis. It was discovered by Giovanni Batista Hodierna before 1654 and re-discovered by Charles Messier in 1771.

Key takeaways

Messier 47 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 47 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 47 from memory before moving on to harder problems.

Reference excerpt

Messier 47 (M47 or NGC 2422), also known as NGC 2478 is an open cluster in the southern constellation of Puppis. It was discovered by Giovanni Batista Hodierna before 1654 and re-discovered by Charles Messier in 1771. It was also independently discovered by Caroline Herschel. There is no cluster in the position indicated by Messier, which he expressed in terms of its right ascension and declination with respect to the star 2 Puppis. However, if the signs (+ and −) that he wrote are swapped, the position matches. Until that equivalency was found, M47 was considered a lost Messier Object. The identification was made in 1959 by Canadian astronomer T. F. Morris. M47 is about 1,600 light-years away and is about 78 million years old. The member stars have been measured down to red dwarfs at apparent magnitude 19. There are around 500 members, the brightest being HD 60855, a magnitude 5.7 Be star. The cluster is dominated by hot class B main sequence and giant stars, but a noticeable colour contrast comes from its brightest red giants. It about a degree from Messier 46, which is much older and much further away.

Illustrations

Worked examples

Example 1 — a first encounter with Messier 47

Start with the simplest possible case. Write down what Messier 47 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 47 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 47 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 47

In research: Messier 47 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 47 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 47 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1654, Messier objects, NGC objects, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 47 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 Messier 47 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 47 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 47 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 47 in simple terms?

Why does Messier 47 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 47?

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 47.