astronomy

HD 89744

HD 89744 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 89744 rather than just read about it. In short: HD 89744 is a star in the northern circumpolar constellation of Ursa Major, positioned about 0.4° due south of the bright star μ UMa. This object has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.73.

Key takeaways

HD 89744 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 89744 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 89744 from memory before moving on to harder problems.

Reference excerpt

HD 89744 is a star in the northern circumpolar constellation of Ursa Major, positioned about 0.4° due south of the bright star μ UMa. This object has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.73. The distance to this star has been measured using the parallax method, which locates it 126 light-years from the Sun. It is drifting closer with a radial velocity of −4.4 km/s. There are two known exoplanets orbiting this star. At various times the star HD 89744 has been assigned a stellar classification of F7V, F7IV-V, and F8IV, suggesting it is an F-type main-sequence star that is evolving onto the subgiant branch. It is ~8.4 billion years old with an inactive chromosphere and is spinning with a projected rotational velocity of 9.3 km/s. The star is 2.16 times the size of the Sun with 1.4 times the Sun's radius. It is a high metallicity star, showing a greater abundance of heavier elements than in the Sun. The star is radiating 6.4 times the luminosity of the Sun from its photosphere at an effective temperature of 6,381 K. This star was identified as a member of the AB Doradus moving group by J. López-Santiago and collaborators in 2006. It was later shown that its evolutionary state is incompatible with membership. In 2001, a faint co-moving companion was identified at an angular separation of 63.1″ from the primary. This is equivalent to a linear projected separation of 2,456 AU (0.04 ly). The companion, designated component B, is an L-class (~L0.5) brown dwarf with a mass of ~0.076 M☉.

Planetary system In April 2000, a planet was discovered using radial velocity measurements taken at Fred Lawrence Whipple Observatory and Lick Observatory. The orbital parameters were updated in 2006 and 2007 using additional measurements. A second candidate planet with a much longer period was discovered in 2019.

See also List of exoplanets discovered before 2000 - HD 89744 b

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 89744

Start with the simplest possible case. Write down what HD 89744 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 89744 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 89744 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 89744

In research: HD 89744 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 89744 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 89744 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bright Star Catalogue objects, Brown dwarfs, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 89744 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 89744 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 89744 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 89744 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 89744 in simple terms?

Why does HD 89744 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 89744?

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 89744.