astronomy

NGC 789

NGC 789 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 789 rather than just read about it. In short: NGC 789 is a spiral galaxy in the constellation of Triangulum. Its velocity with respect to the cosmic microwave background is 5,013±20 km/s, which corresponds to a Hubble distance of 241.2 ± 16.9 Mly (73.94 ± 5.19 Mpc).

Key takeaways

NGC 789 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 789 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 789 from memory before moving on to harder problems.

Reference excerpt

NGC 789 is a spiral galaxy in the constellation of Triangulum. Its velocity with respect to the cosmic microwave background is 5,013±20 km/s, which corresponds to a Hubble distance of 241.2 ± 16.9 Mly (73.94 ± 5.19 Mpc). It was discovered by German astronomer Heinrich Louis d'Arrest on 24 August 1865. NGC 789 has a possible active galactic nucleus, i.e. it has a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars.

NGC 777 group NGC 789 is a member of the NGC 777 Group (also known as LGG 42). There are 13 galaxies in the group, including NGC 750, NGC 751, NGC 761, NGC 777, NGC 783, and NGC 785.

Supernovae Two supernovae have been observed in NGC 789:

SN 2004ad (type unknown, mag. 17.0) was discovered by British amateur astronomer Mark Armstrong on 1 March 2004. SN 2026ovz (Type II, mag. 16.1125) was discovered by the Zwicky Transient Facility on 10 June 2026.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 789

Start with the simplest possible case. Write down what NGC 789 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 789 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 789 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 789

In research: NGC 789 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 789 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 789 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1865, Discoveries by Heinrich Louis d'Arrest, IRAS catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 789 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study NGC 789 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 789 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 789 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 789 in simple terms?

Why does NGC 789 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 789?

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 789.