astronomy

NGC 7789

NGC 7789 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 NGC 7789 rather than just read about it. In short: NGC 7789 (also known as Caroline's Rose, Caroline's Haystack, or the White Rose Cluster) is an open cluster located around 7,600 light years from Earth in the constellation of Cassiopeia. It is intermediate-age cluster with estimates ranging from 1.4 to 1.7 billion years old.

Key takeaways

NGC 7789 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NGC 7789 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 7789 from memory before moving on to harder problems.

Reference excerpt

NGC 7789 (also known as Caroline's Rose, Caroline's Haystack, or the White Rose Cluster) is an open cluster located around 7,600 light years from Earth in the constellation of Cassiopeia. It is intermediate-age cluster with estimates ranging from 1.4 to 1.7 billion years old. It has a mass of around 6,620.4±762.5 solar masses. It was discovered by Caroline Herschel in 1783. Her brother William Herschel included it in his catalog as H VI.30. This cluster is also known as the "White Rose" Cluster or "Caroline's Rose" Cluster because when seen visually, the loops of stars and dark lanes look like the swirling pattern of rose petals as seen from above.

Characteristics

Age While it is known that the cluster is of intermediate-age, its exact age is known with studies giving estimates ranging from 1.4 to 1.6-1.7 billion years. The wide range of ages and little consensus on the age of NGC 7788 is from the combined effects of differential reddening, high binary fraction and rotation-driven broadening of main-sequence turnoff.

Abundances The abundances of this cluster is not simple but is instead complex with various elements having raised abundances. Elements that are formed through neutron-capture are significantly enhanced in their abundance, particularly barium which has an abundance of [Ba/Fe] +0.47 to +0.48. Elements that are produced by the r-process and s-process on the other hand such as iron and yttrium are not as abundant. There seems to be some minor discrepancies for elements such as calcium, sodium, oxygen and aluminum (only one doublet). Early studies that estimated the photometric metallicity of NGC 7789 placed the cluster as having sub-solar values ([Fe/H] −0.26±0.10). However modern studies have placed the iron abundance to be similar to the Sun at [Fe/H] −0.04±0.05. The nitrogen abundance of stars within NGC 7789 are enhanced compared to the rest of the galaxy. Giant stars in the cluster have a abundance of [N/Fe] 0.15±0.13 while clump stars have a abundance of [N/Fe] 0.26±0.08. Ratios of sodium and aluminum are also enhanced.

Lithium The majority of red giant stars within the cluster have abundances of light elements such as lithium, carbon, nitrogen and oxygen that are consistent. However the stars NGC 7789-193 and NGC 7789-301 have anomalously high abundances of lithium with the latter also having strong helium features. There are two explanations for this abundance, the first is internal mixing of the star during their helium-flash while the second is interactions with a companion star sometime in the past. Either explanation involves the synthesis of lithium through the Cameron-Fowler Berillyum transport mechanism.

Content NGC 7789 has a rich and dense stellar population. It has a large number of main-sequence stars (yellow dwarfs), a prominent red giant population and an unusually large population of blue stragglers.

References

External links Media related to NGC 7789 at Wikimedia Commons

NGC 7789 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images SEDS – NGC 7789

Illustrations

Worked examples

Example 1 — a first encounter with NGC 7789

Start with the simplest possible case. Write down what NGC 7789 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 NGC 7789 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 7789 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 7789

In research: NGC 7789 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 NGC 7789 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 7789 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1783, Cassiopeia (constellation), Discoveries by Caroline Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 7789 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 7789 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 7789 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 7789 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 7789 in simple terms?

Why does NGC 7789 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 NGC 7789?

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 7789.