astronomy

NGC 922

NGC 922 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 922 rather than just read about it. In short: NGC 922 is a peculiar galaxy in the southern constellation of Fornax. Its velocity with respect to the cosmic microwave background is 2879 ± 15 km/s, which corresponds to a Hubble distance of 138.5 ± 9.7 Mly (42.46 ± 2.98 Mpc).

Key takeaways

NGC 922 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 922 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 922 from memory before moving on to harder problems.

Reference excerpt

NGC 922 is a peculiar galaxy in the southern constellation of Fornax. Its velocity with respect to the cosmic microwave background is 2879 ± 15 km/s, which corresponds to a Hubble distance of 138.5 ± 9.7 Mly (42.46 ± 2.98 Mpc). Additionally, 17 non-redshift measurements give a distance of 138.88 ± 7.47 Mly (42.582 ± 2.291 Mpc). It was discovered by German-British astronomer William Herschel on 17 November 1784. NGC 922 is one of the nearest known collisional galaxies. This object was described by the Herschels as "considerably faint, pretty large, round, gradually pretty much brighter middle." The general form is described by the morphological classification of SB(s)cd pec, which indicates a peculiar (pec) barred spiral galaxy (SB) with no inner ring system around the bar (s) and loosely-wound spiral arms (cd).

This object was originally described as a dust-obscured grand-design galaxy – a term used to indicate a type of spiral galaxy with prominent and well-defined spiral arms. However, observation of its features suggests it has undergone a merger with a gas-rich dwarf galaxy. This has resulted in a distinctive C-shaped ring of H-alpha emission. About 104 kpc away from NGC 922, there is a dwarf galaxy called S2 that was once thought to have been responsible for NGC 922's structure. A stellar plume is seen extending from the galaxy in the direction of S2, located about 8′ away. However, the stellar plume is not connected to S2, and S2 also has it own tidal structure, which would not be possible if it had already "punched" through NGC 922. The main galaxy has a stellar mass estimated 5.47 billion times the mass of the Sun (solar mass), while the dwarf companion has 28.2 million solar masses. The net mass of NGC 922 is estimated as 75 billion solar masses within a radius of 13.4 kpc, with 72% being in the form of dark matter and 20% as neutral hydrogen. It is a starburst galaxy, and the collision has resulted in star formation at the rate of 7–8 M☉·yr−1. New star clusters have been formed in the ring or bar with a mean age of 16 million years, whereas older clusters of 50 million years or more are predominantly found in the nuclear region. The tidal plume pointing toward the companion mainly consists of much older stars, indicating not much new star formation has taken place in that feature.

Supernovae Three supernovae have been observed in NGC 922:

SN 2002gw (Type II, mag. 17.3) was discovered by Takao Doi and Berto Monard on 13 October 2002. SN 2008ho (Type II-P, mag. 16.5) was discovered by CHASE (CHilean Automatic Supernovas sEarch) on 26 November 2008. SN 2024fa (Type II, mag. 17.98) was discovered by The Young Supernova Experiment (YSE) on 3 January 2024.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 922

Start with the simplest possible case. Write down what NGC 922 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 922 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 922 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 922

In research: NGC 922 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 922 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 922 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1784, Barred spiral galaxies, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 922 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 922 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 922 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 922 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 922 in simple terms?

Why does NGC 922 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 922?

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 922.