astronomy

NGC 3665

NGC 3665 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 3665 rather than just read about it. In short: NGC 3665 is a lenticular galaxy located in the constellation Ursa Major. It is located at a distance of circa 85 million light-years from Earth, which, given its apparent dimensions, means that NGC 3665 is about 85,000 light years across.

Key takeaways

NGC 3665 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 3665 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3665 from memory before moving on to harder problems.

Reference excerpt

NGC 3665 is a lenticular galaxy located in the constellation Ursa Major. It is located at a distance of circa 85 million light-years from Earth, which, given its apparent dimensions, means that NGC 3665 is about 85,000 light years across. It was discovered by William Herschel on March 23, 1789.

Characteristics

NGC 3665 is a lenticular galaxy whose disk is characterised by the presence of a circular dust lane. The galaxy has high molecular gas content, as determined by the detection of CO lines. The molecular gas mass in the galaxy is estimated to be 108.91 M☉. The galaxy has a UV excess that indicates the presence of a young stellar population. The total star formation rate in NGC 3665 is estimated to be 1.7 M☉ per year. This rate is less than the one expected based on the molecular gas reservoirs of the galaxy. It has been suggested that the compact yet massive bulge of the galaxy has stabilised the cold gas, and thus suppressed star formation. The nucleus of the galaxy is active and hosts a low luminosity transition active galactic nucleus (AGN). The most accepted theory for the energy source of AGNs is the presence of an accretion disk around a supermassive black hole. The mass of the black hole in the centre of NGC 3665 is measured using the rotation of the molecular gas around the nucleus as 5.75+1.49−1.18×108 M☉, or 3.8×108 M☉ based on the M–sigma relation. NGC 3665 has been found to emit radio waves. Its emission appears elongated at a position angle perpendicular to the dust lane, with the most luminous region being in the nucleus. The emission extends for more than 5 arcminutes in 610 MHz. In 1.4 GHz, the galaxy has one jet with FRI morphology, that extends for more than 3 kpc. In 5 GHz, emission appears in the nucleus and two jet-like structures. The southeast source has not been resolved, while the northwest extends for 0.7 arcseconds, which corresponds to 120 pc at the distance of NGC 3665. The radio emission is likely associated with a low luminosity AGN.

Supernova One supernova has been detected in NGC 3665, SN 2002hl. It was discovered by T. Boles in unfiltered CCD images taken on November 5, 2002 with a 0.35-m reflector, as part of the U.K. Nova/Supernova Patrol. The supernova had then a magnitude of 16.3. The spectrum of the supernova obtained on November 5 indicated it was a type Ia supernova about one or two months after maximum light.

Nearby galaxies NGC 3665 is the brightest member of a galaxy group known as the NGC 3665 group. Other members of the group include NGC 3648, NGC 3652, NGC 3658, and UGC 6433. NGC 3658 lies 15 arcminutes from NGC 3665.

References

External links

NGC 3665 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images NGC 3665 on SIMBAD

Illustrations

Worked examples

Example 1 — a first encounter with NGC 3665

Start with the simplest possible case. Write down what NGC 3665 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 3665 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 3665 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 3665

In research: NGC 3665 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 3665 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 3665 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1789, Discoveries by William Herschel, Galaxies discovered in 1789, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3665 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 3665 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3665 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 3665 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3665 in simple terms?

Why does NGC 3665 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 3665?

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 3665.