astronomy

IC 1993

IC 1993 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 IC 1993 rather than just read about it. In short: IC 1993 is an unbarred spiral galaxy in the constellation Fornax. It was discovered by Lewis Swift on November 19, 1897.

Key takeaways

IC 1993 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect IC 1993 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IC 1993 from memory before moving on to harder problems.

Reference excerpt

IC 1993 is an unbarred spiral galaxy in the constellation Fornax. It was discovered by Lewis Swift on November 19, 1897. At a distance of about 50 million light-years, and redshift of 1057 km/s, it is one of the closest to us of the 200 galaxies in the Fornax Cluster. IC 1993 is a galaxy with several spiral arms in its disc, and it has a Hubble classification of (R')SA(s)bc, indicating it is an intermediate spiral galaxy with a ring on its outer edges. It is a remote galaxy, far from the center of the Fornax Cluster. It is at the edge of the Fornax Cluster. Near the galaxy is a bright foreground star that makes deep observations more difficult, so the galaxy's apparent magnitude is 12.6. Its size in the night sky is 2.5' x 2.2', and it has a diameter of 45000 light-years. IC 1993 is one of the 25 galaxies known to have rings or partial rings. Most resemble local collisional ring galaxies in morphology, size, and clumpy star formation. Clump ages range from 108 to 109 yr, and clump masses go up to several × 108 solar masses, based on color evolution models. The clump ages are consistent with the expected lifetimes of ring structures if they are formed by collisions. There are 15 other galaxies that resemble the arcs in partial ring galaxies but haven't evident disk emission. Their clumps have bluer colors at all redshifts compared to the clumps in the ring and partial ring sample, and their clump ages are younger than in rings and partial rings by a factor of ~10. In most respects, they resemble chain galaxies except for their curvature. Several rings are symmetric with centered nuclei and no obvious companions. They could be outer Lindblad resonance rings, although some have no obvious bars or spirals to drive them. If these symmetric cases are resonance rings, then they could be the precursors of modern resonance rings, which are only ~30% larger on average. This similarity in radius suggests that the driving pattern speed has not slowed by more by ~30% during the last ~7 Gyr. Those without bars could be examples of dissolved bars.

See also NGC 1425, a similar spiral galaxy, also in the Fornax Cluster NGC 1532, another spiral galaxy in the Fornax Cluster

References

Illustrations

Worked examples

Example 1 — a first encounter with IC 1993

Start with the simplest possible case. Write down what IC 1993 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 IC 1993 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 IC 1993 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 IC 1993

In research: IC 1993 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 IC 1993 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: IC 1993 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1897, Fornax, IC objects, so understanding it makes those chapters shorter.
In everyday life: Look for IC 1993 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 IC 1993 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IC 1993 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 IC 1993 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IC 1993 in simple terms?

IC 1993 is an unbarred spiral galaxy in the constellation Fornax. It was discovered by Lewis Swift on November 19, 1897.

Why does IC 1993 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 IC 1993?

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 IC 1993.