astronomy

NGC 3891

NGC 3891 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 3891 rather than just read about it. In short: NGC 3891 is a large spiral galaxy in the constellation of Ursa Major. Its velocity with respect to the cosmic microwave background is 6,581±20 km/s, which corresponds to a Hubble distance of 316.6 ± 22.2 Mly (97.06 ± 6.80 Mpc).

Key takeaways

NGC 3891 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 3891 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3891 from memory before moving on to harder problems.

Reference excerpt

NGC 3891 is a large spiral galaxy in the constellation of Ursa Major. Its velocity with respect to the cosmic microwave background is 6,581±20 km/s, which corresponds to a Hubble distance of 316.6 ± 22.2 Mly (97.06 ± 6.80 Mpc). However, 10 non-redshift measurements give a slightly farther mean distance of 330.46 ± 14.72 Mly (101.320 ± 4.514 Mpc). It was discovered by German-British astronomer William Herschel on 3 February 1788. NGC 3891 is a LINER galaxy, i.e. a galaxy whose nucleus has an emission spectrum characterized by broad lines of weakly ionized atoms. It is also a radio galaxy, i.e. it has giant regions of radio emission extending well beyond its visible structure. NGC 3891 is a member of the Coma cluster.

Supernovae Two supernovae have been observed in NGC 3891:

SN 2006or (Type Ia, mag. 16.3) was discovered by Tim Puckett and A. Kroes on 18 November 2006. SN 2018bdv (Type II-P, mag. 18.53) was discovered by Gaia Photometric Science Alerts on 29 April 2018.

See also List of NGC objects (3001–4000)

References

External links Media related to NGC 3891 at Wikimedia Commons NGC 3891 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 3891

Start with the simplest possible case. Write down what NGC 3891 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 3891 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 3891 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 3891

In research: NGC 3891 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 3891 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 3891 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1788, Coma Cluster, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3891 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study NGC 3891 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3891 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 3891 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3891 in simple terms?

Why does NGC 3891 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 3891?

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 3891.