astronomy

NGC 185

NGC 185 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 185 rather than just read about it. In short: NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy located 2.08 million light-years from Earth, appearing in the constellation Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy (M31).

Key takeaways

NGC 185 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 185 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 185 from memory before moving on to harder problems.

Reference excerpt

NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy located 2.08 million light-years from Earth, appearing in the constellation Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy (M31). NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707". John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his General Catalogue of Nebulae and Clusters. NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory. Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is usually classified as a Type II Seyfert galaxy, though its status as a Seyfert is questioned. It is possibly the closest Seyfert galaxy to Earth, and is the only known Seyfert in the Local Group.

Distance measurements At least two techniques have been used to measure distances to NGC 185. The surface brightness fluctuations distance measurement technique estimates distances to galaxies based on the graininess of their appearance. The distance measured to NGC 185 using this technique is 2.08 ± 0.15 Mly (640 ± 50 kpc). However, NGC 185 is close enough that the tip of the red giant branch (TRGB) method may be used to estimate its distance. The estimated distance to NGC 185 using this technique is 2.02 ± 0.2 Mly (620 ± 60 kpc).

Star formation Martínez-Delgado, Aparicio, & Gallart (1999) looked into the star formation history of NGC 185 and found that the majority of star formation in NGC 185 happened at early times. In the last ~1 Gyr, stars have formed only near the center of this galaxy. Walter Baade discovered young blue objects within this galaxy in 1951, but these have turned out to be star clusters and not individual stars. A supernova remnant near the center was also discovered by Martínez-Delgado et al.

See also List of Andromeda's satellite galaxies

References

External links

NGC 185 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 NGC 185

Start with the simplest possible case. Write down what NGC 185 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 185 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 185 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 185

In research: NGC 185 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 185 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 185 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Andromeda Subgroup, Caldwell objects, Cassiopeia (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for NGC 185 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 185 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 185 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 185 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 185 in simple terms?

Why does NGC 185 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 185?

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 185.