astronomy

NGC 2115

NGC 2115 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 2115 rather than just read about it. In short: NGC 2115 is a large lenticular galaxy in the constellation of Pictor. Its velocity with respect to the cosmic microwave background is 7,087±23 km/s, which corresponds to a Hubble distance of 340.9 ± 23.9 Mly (104.52 ± 7.33 Mpc).

Key takeaways

NGC 2115 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 2115 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 2115 from memory before moving on to harder problems.

Reference excerpt

NGC 2115 is a large lenticular galaxy in the constellation of Pictor. Its velocity with respect to the cosmic microwave background is 7,087±23 km/s, which corresponds to a Hubble distance of 340.9 ± 23.9 Mly (104.52 ± 7.33 Mpc). It was discovered by British astronomer John Herschel on 4 January 1837.

Pair of interacting galaxies The apparent magnitude of PGC 18002, the galaxy further south, is 15.1 and was certainly not observed by Herschel. The radial velocities of these two galaxies are almost equal, so they are at the same distance from us and, judging by their shape, they are in gravitational interaction.

Identification In the NASA/IPAC Extragalactic Database, NGC 2115 appears as a pair of galaxies. To view the data for NGC 2115, it must be identified as NGC 2115A or PGC 18001. The other galaxy in the pair is identified in this database as NGC 2115B, which is PGC 18002. [Note: This can cause confusion, as other databases, such as SIMBAD, identify PGC 18002 as NGC 2115A.]

Supernova One supernova has been observed in NGC 2115:

SN 2021clw (Type Ia, mag. 16.7) was discovered by ASAS-SN on 10 February 2021.

See also List of NGC objects (2001–3000)

References

External links Media related to NGC 2115 at Wikimedia Commons NGC 2115 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 2115

Start with the simplest possible case. Write down what NGC 2115 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 2115 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 2115 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 2115

In research: NGC 2115 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 2115 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 2115 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1837, Discoveries by John Herschel, ESO objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 2115 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 2115 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 2115 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 2115 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 2115 in simple terms?

Why does NGC 2115 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 2115?

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 2115.