astronomy

NGC 7742

NGC 7742 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 7742 rather than just read about it. In short: NGC 7742 (also known as the Fried Egg Galaxy) is a face-on unbarred spiral galaxy in the constellation Pegasus. Its velocity with respect to the cosmic microwave background is 1292 ± 26 km/s, which corresponds to a Hubble distance of 62.2 ± 4.5 Mly (19.06 ± 1.39 Mpc).

Key takeaways

NGC 7742 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 7742 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 7742 from memory before moving on to harder problems.

Reference excerpt

NGC 7742 (also known as the Fried Egg Galaxy) is a face-on unbarred spiral galaxy in the constellation Pegasus. Its velocity with respect to the cosmic microwave background is 1292 ± 26 km/s, which corresponds to a Hubble distance of 62.2 ± 4.5 Mly (19.06 ± 1.39 Mpc). In addition, six non-redshift measurements give a farther distance of 84.09 ± 26.51 Mly (25.783 ± 8.129 Mpc). It was discovered by astronomer William Herschel on 18 Oct 1784. NGC 7742 is unusual in that it contains a ring but no bar. Typically, bars are needed to produce a ring structure. The bars' gravitational forces move gas to the ends of the bars, where it forms into the rings seen in many barred spiral galaxies. In this galaxy, however, no bar is present, so this mechanism cannot be used to explain the formation of the ring. O. K. Sil'chenko and A. V. Moiseev proposed the ring was formed partly as the result of a merger event in which a smaller gas-rich dwarf galaxy collided with NGC 7742. As evidence for this, they point to the unusually bright central region, the presence of highly inclined central gas disk, and the presence of gas that is counterrotating (or rotating in the opposite direction) with respect to the stars. It is also classified as a Type II Seyfert Galaxy.

Supernovae Two supernovae have been observed in NGC 7742:

SN 1993R (Type II, mag. 17) was discovered by the Leuschner Observatory Supernova Search (LOSS) on 2 June 1993. SN 2014cy (Type II-P, mag. 16.2) was discovered by Ken'ichi Nishimura on 31 August 2014.

See also NGC 7217 – a face-on spiral galaxy with identical characteristics Sombrero Galaxy – a similar galaxy with a dust ring

Gallery

References

External links Media related to NGC 7742 at Wikimedia Commons NGC 7742 at ESA/Hubble

NGC 7742 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Illustrations

Worked examples

Example 1 — a first encounter with NGC 7742

Start with the simplest possible case. Write down what NGC 7742 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 7742 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 7742 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 7742

In research: NGC 7742 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 7742 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 7742 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1784, Discoveries by William Herschel, IRAS catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 7742 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 7742 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 7742 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 7742 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 7742 in simple terms?

Why does NGC 7742 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 7742?

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 7742.