astronomy

Messier 46

Messier 46 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 46 rather than just read about it. In short: Messier 46 or M46, also known as NGC 2437, is an open cluster of stars in the slightly southern constellation of Puppis. It was discovered by Charles Messier in 1771.

Key takeaways

Messier 46 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 46 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 46 from memory before moving on to harder problems.

Reference excerpt

Messier 46 or M46, also known as NGC 2437, is an open cluster of stars in the slightly southern constellation of Puppis. It was discovered by Charles Messier in 1771. Dreyer described it as "very bright, very rich, very large." It is about 5,000 light-years away. There are an estimated 500 stars in the cluster with a combined mass of 453 M☉, and it is thought to be a mid-range estimate of 251.2 million years old. The cluster has a very broadest (tidal) radius of 37.8 ± 4.6 ly (11.6 ± 1.4 pc) and core radius of 8.5 ± 1.3 ly (2.6 ± 0.4 pc). It has a greater spatial extent in infrared than in visible light, suggesting it is undergoing some mass segregation with the fainter (redder) stars migrating to a coma (tail) region. The fainter stars that extend out to the south and west may form a tidal tail due to a past interaction. The planetary nebula NGC 2438 appears to lie within the cluster near its northern edge (the faint almost rainbow array of colored smudge at the top-center of the image), but it is most likely unrelated since it does not share the cluster's radial velocity. This makes for superimposed objects of interest, another instance perhaps being NGC 2818. On the other hand, the illuminating star of the bipolar Calabash Nebula shares the radial velocity and proper motion of Messier 46, and is at the same distance, so is a bona fide member of the open cluster. M46 is located close by to another open cluster, Messier 47. M46 is about a degree east of M47 in the sky, so the two fit well in a binocular or wide-angle telescope field.

See also List of Messier objects Messier object

References

External links

Messier 46, SEDS Messier pages Messier 46, Amateur Astronomer Image – Waid Observatory Dark Atmospheres Photography – M46 w/ NGC 2438 detail NASA Astronomy Picture of the Day: M46 and NGC 2438: Young and Old (5 March 1999) NASA Astronomy Picture of the Day: Stars Young and Old (26 March 2009) – featuring M46 NASA Astronomy Picture of the Day: M64 Plus Two (17 April 2015)

Messier 46 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Illustrations

Worked examples

Example 1 — a first encounter with Messier 46

Start with the simplest possible case. Write down what Messier 46 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 46 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 46 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 46

In research: Messier 46 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 46 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 46 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1771, Discoveries by Charles Messier, Messier objects, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 46 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 46 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 46 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 46 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 46 in simple terms?

Messier 46 or M46, also known as NGC 2437, is an open cluster of stars in the slightly southern constellation of Puppis. It was discovered by Charles Messier in 1771.

Why does Messier 46 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 46?

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 46.