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Westbrook Nebula

Westbrook Nebula 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 Westbrook Nebula rather than just read about it. In short: Westbrook Nebula (CRL 618) is a bipolar protoplanetary nebula which is located around 3600 light years from Earth in the constellation of Auriga. It is being formed by a star that has passed through the red giant phase and has ceased nuclear fusion at its core.

Westbrook Nebula — main illustration
Westbrook Nebula — illustration

Key takeaways

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

Reference excerpt

Westbrook Nebula (CRL 618) is a bipolar protoplanetary nebula which is located around 3600 light years from Earth in the constellation of Auriga. It is being formed by a star that has passed through the red giant phase and has ceased nuclear fusion at its core. This star is concealed at the center of the nebula, and is ejecting gas and dust at velocities of up to 200 km/s. The nebula is named after William E. Westbrook, who died in 1975.

This nebula began to form about 200 years ago, and primarily consists of molecular gas. The outer part of the nebula is the result of interaction between rapid bipolar outflow and the gas that was ejected when the star was passing through its asymptotic giant branch phase. The lobes are inclined about 24° to the line of sight. The energy being radiated from the nebula consists of scattered light from the star at the core, light being emitted from a compact HII region surrounding the star, and energy from the shock-excited gas in the lobes. The dynamics of the molecular gas envelope can be studied by examining microwave emission-line spectra from carbon monoxide rotational transitions. These spectra show two distinct velocity components. The narrow cores of the spectral lines show the familiar parabolic profile of a slow (20 km/sec), high optical depth stellar wind from an Asymptotic Giant Branch (AGB) star. This material was expelled before the object became a protoplanetary nebula and constitutes the bulk of the nebula's mass. A second component arising from the far faster post-AGB wind is also visible. The fast (>190 km/sec) wind component becomes more prominent in higher frequency, higher energy spectral lines, because the fast wind has a higher temperature than the slow AGB wind. The central star is believed to be of spectral class B0 and has 12,200 times the solar luminosity of the sun. The photosphere of this star is now hot enough to have begun ionizing the nebula, and the ionization region is expanding rapidly. The size and rate of growth indicates that ionization began around the year 1971. Once a sizeable portion of the nebula has been ionized, it will have become a planetary nebula. This means the Westbrook Nebula is at a somewhat more advanced evolutionary stage than the Egg Nebula, whose spectral class F5 star has not yet begun to ionize the nebula material.

References

Illustrations

Westbrook Nebula illustration
Westbrook Nebula: Two spectra of carbon monoxide in the Westbrook Nebula are shown. The component shown in yellow arises from the slow wind from the star's AGB phase. The component shown in red is from the faster wind expelled after the star left the AGB. Adapted from Gammie et al..[5]
Two spectra of carbon monoxide in the Westbrook Nebula are shown. The component shown in yellow arises from the slow wind from the star's AGB phase. The component shown in red is from the faster wind expelled after the star left the AGB. Adapted from Gammie et al..[5]

Worked examples

Example 1 — a first encounter with Westbrook Nebula

Start with the simplest possible case. Write down what Westbrook Nebula 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 Westbrook Nebula 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 Westbrook Nebula 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 Westbrook Nebula

In research
Westbrook Nebula 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 Westbrook Nebula 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
Westbrook Nebula is common in secondary-school and first-year university syllabi. It links to neighbouring topics Auriga, Protoplanetary nebulae, so understanding it makes those chapters shorter.
In everyday life
Look for Westbrook Nebula 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 Westbrook Nebula in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Westbrook Nebula means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Westbrook Nebula out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Westbrook Nebula in simple terms?

Westbrook Nebula (CRL 618) is a bipolar protoplanetary nebula which is located around 3600 light years from Earth in the constellation of Auriga. It is being formed by a star that has passed through the red giant phase and has ceased nuclear fusion at its core.

Why does Westbrook Nebula 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 Westbrook Nebula?

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 Westbrook Nebula.

Tags

  • Auriga
  • Protoplanetary nebulae

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