astronomy

Messier 68

Messier 68 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 68 rather than just read about it. In short: Messier 68 (also known as M68 or NGC 4590) is a globular cluster found in the east south-east of Hydra, away from its precisely equatorial part. It was discovered by Charles Messier in 1780.

Key takeaways

Messier 68 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 68 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 68 from memory before moving on to harder problems.

Reference excerpt

Messier 68 (also known as M68 or NGC 4590) is a globular cluster found in the east south-east of Hydra, away from its precisely equatorial part. It was discovered by Charles Messier in 1780. William Herschel described it as "a beautiful cluster of stars, extremely rich, and so compressed that most of the stars are blended together". His son John noted that it was "all clearly resolved into stars of 12th magnitude, very loose and ragged at the borders". M68 is centred about 33,600 light-years away from Earth. It is orbiting our galaxy's galactic bulge with a great eccentricity of 0.5. This takes it to 100,000 light years from the center. It is one of the most metal-poor globular clusters, which means it has a paucity of elements other than hydrogen and helium. The cluster may be undergoing core-collapse, and it displays signs of being in rotation. The cluster may have been acquired in its gravitational tie to the Milky Way through accretion from a satellite galaxy. As of 2015, 50 variable stars have been identified in this cluster; the first 28 being identified as early as 1919–20 by American astronomer Harlow Shapley. Most of the variables are of type RR Lyrae, or periodic variables. Six of the variables are of the SX Phoenicis variety, which display short pulsating behavior.

Gallery

Illustrations

Worked examples

Example 1 — a first encounter with Messier 68

Start with the simplest possible case. Write down what Messier 68 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 68 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 68 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 68

In research: Messier 68 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 68 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 68 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1780, Discoveries by Charles Messier, Globular clusters, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 68 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 68 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 68 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 68 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 68 in simple terms?

Messier 68 (also known as M68 or NGC 4590) is a globular cluster found in the east south-east of Hydra, away from its precisely equatorial part. It was discovered by Charles Messier in 1780.

Why does Messier 68 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 68?

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 68.