astronomy

NGC 864

NGC 864 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 864 rather than just read about it. In short: NGC 864 is a star-forming intermediate spiral galaxy located in the Cetus constellation. It's also classified as an isolated galaxy on the AMIGA (Analysis of the Interstellar Medium of Isolated Galaxies) catalogue as CIG 96.

Key takeaways

NGC 864 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 864 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 864 from memory before moving on to harder problems.

Reference excerpt

NGC 864 is a star-forming intermediate spiral galaxy located in the Cetus constellation. It's also classified as an isolated galaxy on the AMIGA (Analysis of the Interstellar Medium of Isolated Galaxies) catalogue as CIG 96. Its discovery and first description was realized by William Herschel in October 25th, 1785 and the findings made public through his Catalogue of Nebulae and Clusters of Stars, published in 1786. Due to its diameter, declination and inclination, NGC 864 was selected in 2012 by a group of astronomers working at the Roque de los Muchachos Observatory as an object for kinematics study. Besides collecting data to help understand NGC 864's morphology, the objective of the project was to develop a method of flux-calibration for the new GHαFaS system on the William Herschel Telescope.

Morphology Galaxies are the basic building blocks of the Universe and their formation is of great interest in current astrophysical research. A galaxy's morphology is the result of both externally driven (like a galaxy merger) and internal evolution (as in a spiral pattern driven). Using ACAM and GHαFaS to produce high spectral resolution Hα images of NGC 864, and integral-field spectrograph data, astronomers were able to determine its bar presents bright regions of massive star formation at the ends, where two asymmetric arms arise. NGC 864's outer spiral shows a flocculent pattern, leading some astronomers to classify it as a grand design galaxy.

Integral HI spectrum asymmetry Due to its isolation, one of the most interesting characteristics of this galaxy is its asymmetry. The asymmetry in galaxies located in high-density areas is often the result of galaxy-galaxy interaction, like in a merger. The origin of asymmetries in isolated galaxies however, is not well understood. Some astronomers suggest it could originate from long-lived dynamical instabilities. In a study from 2005, astronomers realized an integral HI spectra of NGC 864, producing a detailed analysis of its HI density distribution and velocity field. The data showed the interstellar medium to be symmetric in velocity, but asymmetric in intensity, suggesting the possibility of its asymmetry being the result of an internal dynamical instability unlikely. The researchers speculate NGC 864's asymmetry might have been the result of a minor galaxy companion crossing the equatorial plane just outside the optical disc but still within the extended HI disc, causing the warp 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 864

Start with the simplest possible case. Write down what NGC 864 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 864 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 864 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 864

In research: NGC 864 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 864 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 864 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cetus (constellation), IRAS catalogue objects, Intermediate spiral galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 864 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 864 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 864 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 864 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 864 in simple terms?

Why does NGC 864 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 864?

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 864.