astronomy

NGC 3640

NGC 3640 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 3640 rather than just read about it. In short: NGC 3640 is an elliptical galaxy located in the constellation Leo. It is located at a distance of circa 75 million light years from Earth, which, given its apparent dimensions, means that NGC 3640 is about 90,000 light years across.

Key takeaways

NGC 3640 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 3640 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3640 from memory before moving on to harder problems.

Reference excerpt

NGC 3640 is an elliptical galaxy located in the constellation Leo. It is located at a distance of circa 75 million light years from Earth, which, given its apparent dimensions, means that NGC 3640 is about 90,000 light years across. It was discovered by William Herschel on February 23, 1784. It is a member of the NGC 3640 Group of galaxies, which is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster. It lies 2 degrees south of Sigma Leonis and is a member of the Herschel 400 Catalogue. It is condensed and can be spotted with a small telescope from suburban skies.

Characteristics NGC 3640 is an elliptical galaxy with a highly disturbed stellar component. The galaxy features boxy isophotes, and patchy shell-like features. These features indicate a recent merger with a smaller gas-poor galaxy. A dust lane is observed along the minor-axis, spanning 30 arcseconds in a north-south direction. The galaxy has a high rotational velocity, estimated to be 120 ± 10 km/s, higher than that of other elliptical galaxies of similar luminosity. The HI mass of the galaxy is estimated to be 1.85×107 M☉ and the mass of HII less than 7.44×107 M☉. In the centre of NGC 3640 lies a supermassive black hole whose mass is estimated to be roughly 100 million (107.99 ± 0.39) M☉ based on the Sérsic profile.

Nearby galaxies NGC 3640 is the foremost galaxy in a galaxy group known as the NGC 3640 group. Other members of the group include NGC 3630, NGC 3641, NGC 3643, and NGC 3664. NGC 3640 forms a pair with NGC 3641, which lies 2.5 arcminutes south from NGC 3640. The group belongs to the Leo II groups, a large collection of galaxies belonging to the Virgo Supercluster scattered across 30 million light years of space west of the Virgo Cluster.

See also NGC 2865 and NGC 5018 - two other elliptical galaxies with disturbed morphology

References

External links Media related to NGC 3640 at Wikimedia Commons NGC 3640 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images NGC 3640 on SIMBAD

Illustrations

Worked examples

Example 1 — a first encounter with NGC 3640

Start with the simplest possible case. Write down what NGC 3640 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 3640 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 3640 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 3640

In research: NGC 3640 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 3640 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 3640 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1784, Discoveries by William Herschel, Elliptical galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3640 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 3640 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3640 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 3640 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3640 in simple terms?

Why does NGC 3640 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 3640?

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 3640.