astronomy

HD 87816

HD 87816 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 87816 rather than just read about it. In short: HD 87816 is a star in the constellation Vela. With an apparent magnitude of 6.499, it is very close to the average threshold for naked eye visibility, and can only be viewed from sufficiently dark skies, far from light pollution.

Key takeaways

HD 87816 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 87816 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 87816 from memory before moving on to harder problems.

Reference excerpt

HD 87816 is a star in the constellation Vela. With an apparent magnitude of 6.499, it is very close to the average threshold for naked eye visibility, and can only be viewed from sufficiently dark skies, far from light pollution. Based on parallax measurements, it lies at a distance of 436 light-years. It is moving away from the Solar System at a velocity of 4.7 km/s. The spectrum of this star matches a spectral class of K1III, with the luminosity class III indicating it is a giant star that has exhausted the hydrogen at its core. It is now fusing helium, being in the evolutionary stage known as the horizontal branch. The star has 2.4 times the Sun's mass, having grown to a radius 9.0 times the radius of the Sun. It shines with 45 times the Sun's luminosity at an effective temperature of 4,989 K. The temperature gives it the orange hue typical of K-type stars. HD 87816 was once believed to be a variable star and received the variable-star designation R Velorum, but it is now considered a constant star.

Planetary system HD 87816 hosts two known exoplanets, discovered in 2025 via Doppler spectroscopy. Both are gas giants, like Jupiter and Saturn. Planet b has a minimum mass of 6.7 Jupiter masses (MJ). It takes 484 days (1.33 years) to complete an orbit around HD 87816 and has a very high orbital eccentricity of 0.78, among the highest of exoplanets orbiting giant stars. Planet c has a minimum mass of 12.2 Jupiter masses. It takes 7,600 days (21 years) to complete an orbit around its host, and has a low eccentricity of 0.11.

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 87816

Start with the simplest possible case. Write down what HD 87816 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 87816 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 87816 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 87816

In research: HD 87816 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 87816 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 87816 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bright Star Catalogue objects, Durchmusterung objects, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 87816 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 87816 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 87816 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 87816 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 87816 in simple terms?

Why does HD 87816 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 87816?

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 87816.