astronomy

IC 10

IC 10 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 10 rather than just read about it. In short: IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by American astronomer Lewis Swift on 8 October 1887.

Key takeaways

IC 10 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 10 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IC 10 from memory before moving on to harder problems.

Reference excerpt

IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by American astronomer Lewis Swift on 8 October 1887. In 1935 Nicholas Mayall became the first to suggest that the object is extragalactic. Edwin Hubble suspected it might belong to the Local Group of galaxies, but its status remained uncertain for decades. The radial velocity of IC 10 was measured in 1962, and it was found to be approaching the Milky Way at approximately 350 km/s, strengthening the evidence for its membership in the Local Group. Its membership in the group was finally confirmed in 1996 by direct measurements of its distance based on observations of Cepheids; most estimates place the galaxy 2–3 million light years from Earth, with some estimates ranging from 1.5–4.5 million light years. Despite its closeness, the galaxy is rather difficult to study because it lies near the plane of the Milky Way and is therefore heavily obscured by interstellar matter. The apparent distance between IC 10 and the Andromeda Galaxy is about the same as the apparent distance between the Andromeda Galaxy and the Triangulum Galaxy, which suggests that IC 10 may belong to the M31 subgroup. IC 10 is the only known starburst galaxy in the Local Group of galaxies; it has many more Wolf–Rayet stars per square kiloparsec (5.1 stars/kpc2) than the Large Magellanic Cloud (2.0 stars/kpc2) or the Small Magellanic Cloud (0.9 stars/kpc2). Although the galaxy has a luminosity similar to the SMC, it is considerably smaller, with an estimated diameter of around 5000 light years. Its higher metallicity compared to the SMC suggests that star formation activity has continued for a longer time period. The H II regions in IC 10 have all formed recently, within the last 10 Myr. The evolutionary status of the Wolf–Rayet stars suggests that they all formed in a relatively short timespan. The ratio between the two types of Wolf–Rayet stars (WC stars and WN stars) in IC 10 is very different from the ratio in other galaxies in the Local Group, which may be somehow due to the starburst nature of the galaxy. Currently, the galaxy produces stars at the rate of 0.04–0.08 solar masses per year, which means that the gas supply in the galaxy can last for only a few billion years longer. Observations of IC 10 in the far-infrared show that the dust in this mild starburst galaxy is deficient in small grains. It is hypothesized that any small grains that formerly existed were destroyed by strong ultraviolet radiation in the areas around the hot luminous stars that were formed in the galaxy's recent burst of star formation. The galaxy has a huge envelope of hydrogen gas, with an apparent size measuring 68′ × 80′, which is far larger than the apparent size of the galaxy in visible light (5.5′ × 7.0′). IC 10 is also unusual in the respect that the visible part of the galaxy seems to rotate in a different direction than the outer envelope. It has an H II nucleus.

Gallery

Illustrations

Worked examples

Example 1 — a first encounter with IC 10

Start with the simplest possible case. Write down what IC 10 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 10 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 10 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 10

In research: IC 10 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 10 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 10 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1887, Cassiopeia (constellation), Discoveries by Lewis Swift, so understanding it makes those chapters shorter.
In everyday life: Look for IC 10 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 10 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IC 10 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 10 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IC 10 in simple terms?

IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by American astronomer Lewis Swift on 8 October 1887.

Why does IC 10 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 10?

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 10.