astronomy

HD 99109

HD 99109 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 99109 rather than just read about it. In short: HD 99109 is an orange-hued star with an exoplanetary companion in the constellation of Leo. It has an apparent visual magnitude of +9.10, which is too faint to be visible to the naked eye.

Key takeaways

HD 99109 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 99109 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 99109 from memory before moving on to harder problems.

Reference excerpt

HD 99109 is an orange-hued star with an exoplanetary companion in the constellation of Leo. It has an apparent visual magnitude of +9.10, which is too faint to be visible to the naked eye. The distance to this system is 179 light-years based on parallax, and it is drifting further away with a radial velocity of +33 km/s. The star is one and half degrees away from the celestial equator to the south. The stellar classification of this star is G8/K0IV, matching a late G or early K-type subgiant star. It appears to be past the end of its main sequence lifetime, having exhausted the supply of hydrogen at its core. The star is 93% as massive as the Sun and has 90% of the Sun's radius. It is spinning with a projected rotational velocity of ~2 km/s and has over twice the abundance of iron relative to hydrogen than the Sun. The star is radiating 56% of the Sun's luminosity from its photosphere at an effective temperature of 5,270 K. As of 2006, one extrasolar planet has been confirmed to be orbiting the star. The star HD 99109 is named Shama. The name was selected in the NameExoWorlds campaign by Pakistan, during the 100th anniversary of the IAU. Shama (شمع) is an Urdu literary term meaning a small lamp or flame. The exoplanet companion is called Perwana, meaning 'moth' in Urdu, alluding to the eternal love of an object circling a source of light.

Planetary system The planet HD 99109 b has an orbit comparable in eccentricity to the planet Mars in the Solar System but has a mass at least half that of Jupiter. Stability analysis reveals that Earth-size planets could have stable orbits in the planet's Trojan points, located 60 degrees ahead and behind the planet's position in its orbit.

References

Worked examples

Example 1 — a first encounter with HD 99109

Start with the simplest possible case. Write down what HD 99109 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 99109 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 99109 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 99109

In research: HD 99109 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 99109 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 99109 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, Henry Draper Catalogue objects, Hipparcos objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 99109 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 99109 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 99109 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 99109 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 99109 in simple terms?

HD 99109 is an orange-hued star with an exoplanetary companion in the constellation of Leo. It has an apparent visual magnitude of +9.10, which is too faint to be visible to the naked eye.

Why does HD 99109 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 99109?

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 99109.