astronomy

HD 109749

HD 109749 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 109749 rather than just read about it. In short: HD 109749 is a binary star system about 206 light years away in the constellation of Centaurus. The pair have a combined apparent visual magnitude of 8.08, which is too faint to be visible to the naked eye.

Key takeaways

HD 109749 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 109749 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 109749 from memory before moving on to harder problems.

Reference excerpt

HD 109749 is a binary star system about 206 light years away in the constellation of Centaurus. The pair have a combined apparent visual magnitude of 8.08, which is too faint to be visible to the naked eye. The primary component has a close orbiting exoplanet companion. The system is drifting closer with a heliocentric radial velocity of −13.2 km/s. The primary component, HD 109749 A, is a G-type subgiant star with a spectral type of G3IV, indicating it is an evolved star with a luminosity higher than that of a main sequence star. It has a mass of 1.14 M☉ and a radius of 1.21 R☉. The star is shining with a luminosity of 1.55 L☉ and has an effective temperature of 5,860 K. Evolutionary models estimate an age of 4.1 billion years. HD 109749 A is chromospherically inactive and has a high metallicity, with an iron abundance 178% of Sun's. The secondary, HD 109749 B, is a K-type main sequence star with an apparent magnitude of 10.3. It has a mass of about 0.78 M☉ and is located at a separation of 8.4 arcseconds, which corresponds to a projected separation of 490 AU. This star has the same proper motion as the primary and seems to be at the same distance, confirming they form a physical binary system.

Planetary system In 2005, an exoplanet was discovered around HD 109749 A. It was detected by the radial velocity method as part of the N2K Consortium. It is a hot Jupiter with a minimum mass of 0.28 MJ and a semimajor axis of 0.06 AU.

See also HD 149143 List of extrasolar planets

References

Worked examples

Example 1 — a first encounter with HD 109749

Start with the simplest possible case. Write down what HD 109749 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 109749 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 109749 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 109749

In research: HD 109749 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 109749 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 109749 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Binary stars, Centaurus, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 109749 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “HD 109749” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study HD 109749 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 109749 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 109749 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 109749 in simple terms?

Why does HD 109749 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 109749?

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 109749.