astronomy

NGC 520

NGC 520 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 520 rather than just read about it. In short: NGC 520, also known as the Flying Ghost, is a pair of colliding spiral galaxies about 105 million light-years away in the constellation Pisces. They were discovered by astronomer William Herschel on 13 December 1784.

Key takeaways

NGC 520 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 520 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 520 from memory before moving on to harder problems.

Reference excerpt

NGC 520, also known as the Flying Ghost, is a pair of colliding spiral galaxies about 105 million light-years away in the constellation Pisces. They were discovered by astronomer William Herschel on 13 December 1784. Halton Arp called this the second-brightest very disturbed galaxy in the sky, and it is as bright in the infrared and radio bands as the Antennae Galaxies. Simulations indicate this object consists of two galactic disks that began interacting about 300 million years ago. The system is still in an early stage of its merger, showing two separate velocity systems in the spectra, and two small tails. Two galactic nuclei have been detected, and one is an H II nucleus.

The main galactic component is being viewed edge-on, making it fainter in the optical band. The secondary component is brighter but less massive than the main, and is located to the northwest. They are separated by a dark lane of dust. The region of the galaxies outside their nuclei experienced a period of increased star formation roughly around the time they began to interact. Two dwarf objects are located in the vicinity of this merging pair, and one of them, designated UGC 957, is located in the northern tidal tail – it may be the result of the interaction. When viewed in the X-ray band, the interacting galaxies appear around half as luminous as expected given their merger state. Analysis of the gas and molecular features suggests the secondary merger component is gas poor. Most of the star formation, therefore, took place in the gas-rich main component to the southeast. 15 X-ray sources are detected within the merger, with many of them displaying long-term variability. A large galactic wind is evident, being driven by the starburst activity.

Supernova One supernova has been observed in NGC 520: SN 2025zjx (Type II, mag. 21.68) was discovered by Pan-STARRS on 29 September 2025.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 520

Start with the simplest possible case. Write down what NGC 520 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 520 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 520 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 520

In research: NGC 520 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 520 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 520 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arp objects, Astronomical objects discovered in 1784, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 520 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 520 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 520 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 520 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 520 in simple terms?

Why does NGC 520 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 520?

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 520.