astronomy

HD 102117

HD 102117 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 102117 rather than just read about it. In short: HD 102117 or Uklun is a star in the southern constellation of Centaurus. With an apparent visual magnitude of 7.47, it is too dim to be seen without binoculars or a small telescope.

Key takeaways

HD 102117 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 102117 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 102117 from memory before moving on to harder problems.

Reference excerpt

HD 102117 or Uklun is a star in the southern constellation of Centaurus. With an apparent visual magnitude of 7.47, it is too dim to be seen without binoculars or a small telescope. It is located at a distance of approximately 129 light-years from the Sun based on parallax. HD 102117 is drifting further away with a radial velocity of +50 km/s, having come to within 43.9 light-years some 692,000 years ago. It has one known planet. The stellar classification of HD 102117 is G6V, which matches the spectrum of an ordinary G-type main-sequence star. It is roughly five billion years old and is spinning with a projected rotational velocity of 0.9 km/s. The star shows only a low level of chromospheric activity and is photometrically stable, meaning it doesn't vary significantly in brightness. It appears metal-enriched, showing a higher abundance of heavy elements compared to the Sun.

Planetary system In 2004, the Anglo-Australian Planet Search announced a planet orbiting the star. A short time later the HARPS team also announced the presence of a planet around this star. Both groups detected this planet with the radial velocity method. HD 102117, and its planet HD 102117b, were chosen as part of the 2019 NameExoWorlds campaign organised by the International Astronomical Union, which assigned each country a star and planet to be named. HD 102117 was assigned to Pitcairn Islands. The winning proposal named the star Uklun, from the word aklan 'we/us' in the Pitcairn language, and the planet Leklsullun , from the phrase lekl salan 'child/children' (lit. 'little person').

See also List of extrasolar planets HARPS spectrograph Anglo-Australian Planet Search

References

External links "HD 102117". Exoplanets. Archived from the original on 2012-03-04. Retrieved 2009-05-23.

Worked examples

Example 1 — a first encounter with HD 102117

Start with the simplest possible case. Write down what HD 102117 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 102117 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 102117 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 102117

In research: HD 102117 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 102117 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 102117 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Centaurus, Durchmusterung objects, G-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for HD 102117 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 102117 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 102117 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 102117 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 102117 in simple terms?

HD 102117 or Uklun is a star in the southern constellation of Centaurus. With an apparent visual magnitude of 7.47, it is too dim to be seen without binoculars or a small telescope.

Why does HD 102117 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 102117?

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 102117.