astronomy

Messier 93

Messier 93 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 93 rather than just read about it. In short: Messier 93 or M93, also known as NGC 2447 or the Critter Cluster, is an open cluster in the modestly southern constellation Puppis, the imagined poop deck of the legendary Argo. Observational history and appearance It was discovered by Charles Messier then added to his catalogue of comet-like objects in 1781.

Key takeaways

Messier 93 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 93 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 93 from memory before moving on to harder problems.

Reference excerpt

Messier 93 or M93, also known as NGC 2447 or the Critter Cluster, is an open cluster in the modestly southern constellation Puppis, the imagined poop deck of the legendary Argo.

Observational history and appearance It was discovered by Charles Messier then added to his catalogue of comet-like objects in 1781. Caroline Herschel, the younger sister of William Herschel, independently discovered it in 1783, thinking it had not yet been catalogued by Messier. Walter Scott Houston (died 1993) described its appearance:

Some observers mention the cluster as having the shape of a starfish. With a fair-sized telescope, this is its appearance on a dull night, but [a four-inch refractor] shows it as a typical star-studded galactic cluster.

Properties It has a Trumpler class of I 3 r, indicating it is strongly concentrated (I) with a large range in brightness (3) and is rich in stars (r). M93 is about 3,380 light-years from the solar radius and has a great spatial radius of 10 light-years, a tidal radius of 13.1±2.3 ly, and a core radius of 4.2 ly. Its age is estimated at 387.3 million years. It is nearly on the galactic plane and has an orbit that varies between 28–29 kly (8.5–8.9 kpc) from the Galactic Center over a period of 242.7±7.9 Myr. Fifty-four variable stars have been found in M93, including one slowly pulsating B-type star, one rotating ellipsoidal variable, seven Delta Scuti variables, six Gamma Doradus variables, and one hybrid δ Sct/γ Dor pulsator. Four spectroscopic binary systems within include a yellow straggler component.

Gallery

Illustrations

Worked examples

Example 1 — a first encounter with Messier 93

Start with the simplest possible case. Write down what Messier 93 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 93 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 93 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 93

In research: Messier 93 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 93 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 93 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1781, Discoveries by Charles Messier, Messier objects, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 93 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 93 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 93 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 93 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 93 in simple terms?

Messier 93 or M93, also known as NGC 2447 or the Critter Cluster, is an open cluster in the modestly southern constellation Puppis, the imagined poop deck of the legendary Argo. Observational history and appearance It was discovered by Charles Messier then added to his catalogue of comet-like objec…

Why does Messier 93 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 93?

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 93.