astronomy

NGC 3642

NGC 3642 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 3642 rather than just read about it. In short: NGC 3642 is a spiral galaxy in the constellation Ursa Major. The galaxy has a low-ionization nuclear emission-line region.

Key takeaways

NGC 3642 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 3642 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3642 from memory before moving on to harder problems.

Reference excerpt

NGC 3642 is a spiral galaxy in the constellation Ursa Major. The galaxy has a low-ionization nuclear emission-line region. It is located at a distance of circa 30 million light years from Earth, which, given its apparent dimensions, means that NGC 3642 is about 50,000 light years across. The galaxy is characterised by an outer pseudoring, which was probably formed after the accretion of a gas rich dwarf galaxy.

Structure NGC 3642 is a spiral galaxy without a bar. In the nucleus there is a supermassive black hole with an estimated mass of 26-31 million M⊙, based on the intrinsic velocity dispersion as measured by the Hubble Space Telescope, or 15 million M⊙, based on the bulge luminosities in near-infrared Ks-band. Around the nucleus, a one-armed spiral forms a ring, and it is possible that it leads material towards the nucleus. The nucleus is surrounded by an inner flocculent spiral. The outer part of the spiral forms a pseudoring that extends for about half a circle. The outer part of the spiral is warped, while its main part features an ordinary differentially rotating disk. The HI gas is also warped and extends further on the western side.

Nearby galaxies The galaxy belongs to the NGC 3642 group (also known as the NGC 3610 group), a galaxy group that also includes NGC 3610, NGC 3619, NGC 3669, NGC 3674 and NGC 3683. Other nearby galaxies include NGC 3440, NGC 3445, NGC 3458, NGC 3543 and NGC 3613.

Gallery

References

External links

NGC 3642 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 3642

Start with the simplest possible case. Write down what NGC 3642 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 3642 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 3642 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 3642

In research: NGC 3642 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 3642 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 3642 is common in secondary-school and first-year university syllabi. It links to neighbouring topics NGC objects, Principal Galaxies Catalogue objects, UGC objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3642 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 3642 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3642 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 3642 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3642 in simple terms?

NGC 3642 is a spiral galaxy in the constellation Ursa Major. The galaxy has a low-ionization nuclear emission-line region.

Why does NGC 3642 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 3642?

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 3642.