astronomy

HD 121504

HD 121504 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 121504 rather than just read about it. In short: HD 121504 is a star with an orbiting exoplanet in the southern constellation of Centaurus. It is located at a distance of 136 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of 19.6 km/s.

Key takeaways

HD 121504 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 121504 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 121504 from memory before moving on to harder problems.

Reference excerpt

HD 121504 is a star with an orbiting exoplanet in the southern constellation of Centaurus. It is located at a distance of 136 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of 19.6 km/s. With an apparent visual magnitude of 7.54, this star is too faint to be visible to the naked eye. It shows a high proper motion, traversing the celestial sphere at an angular rate of 0.270 arcsec yr−1. The spectrum of this star presents as an ordinary G-type main-sequence star, a yellow dwarf similar in appearance to the Sun, having a stellar classification of G2V. It is roughly two billion years old and is spinning with a rotation period of 8.6 days. The star has 16% more mass than the Sun and a 15% greater radius. The metallicity (the abundance of elements more massive than helium) is higher than solar. The star is radiating 162% of the luminosity of the Sun from its photosphere at an effective temperature of 6,089 K. A nearby visual companion, designated as SAO 241323 has been proposed as a component of the system. However, the pair form an optical binary with an angular separation of 34.2″, and in reality this is a white giant star located thousands of light years away.

Exoplanet In 2000 the Geneva Extrasolar Planet Search Team announced the discovery of an extrasolar planet orbiting the star.

Worked examples

Example 1 — a first encounter with HD 121504

Start with the simplest possible case. Write down what HD 121504 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 121504 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 121504 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 121504

In research: HD 121504 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 121504 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 121504 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Centaurus, Double stars, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 121504 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 121504 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 121504 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 121504 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 121504 in simple terms?

Why does HD 121504 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 121504?

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 121504.