astronomy

NGC 871

NGC 871 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 871 rather than just read about it. In short: NGC 871 is a barred spiral galaxy in the Aries constellation. Its discovery and first description was realized by William Herschel on October 14, 1784 and the findings made public through his Catalogue of Nebulae and Clusters of Stars in 1786.

Key takeaways

NGC 871 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 871 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 871 from memory before moving on to harder problems.

Reference excerpt

NGC 871 is a barred spiral galaxy in the Aries constellation. Its discovery and first description was realized by William Herschel on October 14, 1784 and the findings made public through his Catalogue of Nebulae and Clusters of Stars in 1786. By using the galaxies' radial velocities and distances as a grouping factor, astronomers assign this galaxy to LGG (Lyon Groups of Galaxies) 53 along with 8 other members (UGC 1693, UGC 1761, NGC 876, NGC 877, UGC 1817, IC 1791 and UGC 1773).

Galaxy group NGC 871/6/7 At the current epoch, most galaxies can be found in medium-density group environments, where tidal interactions play an important role in galactic evolution. Several nearby, gas-rich groups exhibit clear signs of these interactions, giving the opportunity for scientists to study how galaxies are formed and interact with each other. In 2012 astronomers conducted an extensive survey to measure the Hl emissions from NGC 871 and other galaxies in LGG 53, using the Giant Metrewave Radio Telescope and Canada–France–Hawaii Telescope. This galaxy group first attracted attention due to its gas-rich interaction as well as harboring AGC (Arecibo General Catalog) 749170, a galaxy with a mass of ~×109.3 M☉. This group resides in a common HI distribution with a total HI mass of Mhl 6 x 10×1010 M☉. Such a massive structure is very rare in the local Universe (galaxies with a Mhl > ×1010 M☉ represents less 2 per cent of cases) and each large spiral in NGC 871/6/7 seems to exceeds this value. The study suggests seven of the eight gas-rich detections (three spirals and four dwarfs) contain stellar components and appear to be standard dark-matter dominated galaxies that were built during the epoch of galaxy assembly. AGC 749170 however is probably the result of major mergers and very active tidal interaction, resulting in the massive structure we can observe today.

See also New General Catalogue List of NGC objects

References

External links NASA/IPAC Extragalactic Database - Extensive database of NGC objects.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 871

Start with the simplest possible case. Write down what NGC 871 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 871 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 871 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 871

In research: NGC 871 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 871 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 871 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aries (constellation), Astronomical objects discovered in 1784, Barred spiral galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 871 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 871 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 871 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 871 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 871 in simple terms?

Why does NGC 871 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 871?

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 871.