astronomy

NGC 6118

NGC 6118 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 6118 rather than just read about it. In short: NGC 6118 is a grand design spiral galaxy located 83 million light-years away in the constellation Serpens (the Snake). It was discovered by German-British astronomer William Herschel on 14 April 1785.

Key takeaways

NGC 6118 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 6118 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 6118 from memory before moving on to harder problems.

Reference excerpt

NGC 6118 is a grand design spiral galaxy located 83 million light-years away in the constellation Serpens (the Snake). It was discovered by German-British astronomer William Herschel on 14 April 1785. NGC 6118 measures roughly 110,000 light-years across; about the same as our own galaxy, the Milky Way. Its shape is classified as SA(s)cd, meaning that it is unbarred and has several rather loosely wound spiral arms. The large numbers of bright bluish knots are active star-forming regions where some very luminous and young stars can be perceived. Because NGC 6118 has loosely wound spiral open arms, no clear defined spiral arms like the Milky Way galaxy and lacks a central bar, the galaxy thus does not have a galactic habitable zone like the Milky Way. For the Milky Way, the galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs and an inner radius close to the Galactic Center, both of which lack hard boundaries. NGC 6118 is difficult to see with a small telescope. Amateur astronomers have nicknamed it the "Blinking Galaxy", as it has a tendency to flick in and out of view with different eye positions.

Supernovae Two supernovae have been observed in NGC 6118:

SN 2004dk was first reported by James Graham and Weidong Li on 1 August 2004. They found it by studying images produced by the Lick Observatory Supernova Search (LOSS) program with the 76 cm Katzman Automatic Imaging Telescope (KAIT) in San Jose, CA. SN 2004dk was initially classified by European Southern Observatory astronomer Fernando Patat et al. on 4 Aug 2004 as a Type Ic supernova. Type Ib and Ic supernovae are the end result of massive stars (> 8 solar masses) that have run out of nuclear fuel. Normally one would expect to see evidence of hydrogen and helium, but when these supernova occur in a binary system the companion has sometimes gravitationally stripped the outer layers of the progenitor star away, leaving only the heavier elements. Type Ib supernovae have no hydrogen, while Type Ic have neither hydrogen or helium. Over the following weeks, Alexei Filippenko et al. and the University of California at Berkeley discovered prominent He I absorption lines, thus changing the classification of the supernova to Type Ib. SN 2020hvp (Type Ib, mag. 18.2) was discovered by ATLAS on 21 April 2020.

See also List of NGC objects (6001–7000)

References

External links Media related to NGC 6118 at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with NGC 6118

Start with the simplest possible case. Write down what NGC 6118 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 6118 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 6118 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 6118

In research: NGC 6118 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 6118 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 6118 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1785, Discoveries by William Herschel, IRAS catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 6118 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 6118 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 6118 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 6118 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 6118 in simple terms?

Why does NGC 6118 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 6118?

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 6118.