astronomy

HD 149989

HD 149989 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 HD 149989 rather than just read about it. In short: HD 149989 is a single, variable star in the southern constellation of Ara, located near the western constellation border with Norma. It has the variable star designation V872 Arae, while HD 149989 is the identifier from the Henry Draper Catalogue.

Key takeaways

HD 149989 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 149989 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 149989 from memory before moving on to harder problems.

Reference excerpt

HD 149989 is a single, variable star in the southern constellation of Ara, located near the western constellation border with Norma. It has the variable star designation V872 Arae, while HD 149989 is the identifier from the Henry Draper Catalogue. This is a dim star near the lower limit of visibility to the naked eye with an apparent visual magnitude that fluctuates around 6.30. It is located at a distance of 167 light years from the Sun based on parallax, and is drifting further away with a radial velocity of 46 km/s. HD 149989 was discovered to be a variable star when the data from the Hipparcos mission was analyzed. The discovery was published in 1997, in the list of periodic variables seen by that satellite. In 1998, Conny Aerts et al. sifted through that list, and determined that HD 149989 is a Gamma Doradus type star. It has a period of 0.42658 days. It was given its variable star designation in March 2000. This object is an A-type main-sequence star with a stellar classification of A9 V. A 2016 survey of γ Doradus stars found a class of F1 V nn m-4, where the 'nn' indicates "nebulous" lines due to rapid rotation and the 'm-4' means a metal-poor star with metal lines that match a class of A7. It is around 1.1 billion years old and is spinning with a projected rotational velocity of 136 km/s.

References

External links HIP 81650 Image HD 149989

Illustrations

Worked examples

Example 1 — a first encounter with HD 149989

Start with the simplest possible case. Write down what HD 149989 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 HD 149989 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 HD 149989 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 HD 149989

In research: HD 149989 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 HD 149989 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: HD 149989 is common in secondary-school and first-year university syllabi. It links to neighbouring topics A-type main-sequence stars, Ara (constellation), Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 149989 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 HD 149989 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 149989 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 HD 149989 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 149989 in simple terms?

Why does HD 149989 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 HD 149989?

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 HD 149989.