astronomy

HD 159868

HD 159868 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 159868 rather than just read about it. In short: HD 159868 is a star in the southern constellation of Scorpius, positioned about 0.3° to the ESE of the bright star Theta Scorpii. With an apparent visual magnitude of +7.24, it is too faint to be visible to the naked eye but can be viewed with a small telescope.

Key takeaways

HD 159868 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 159868 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 159868 from memory before moving on to harder problems.

Reference excerpt

HD 159868 is a star in the southern constellation of Scorpius, positioned about 0.3° to the ESE of the bright star Theta Scorpii. With an apparent visual magnitude of +7.24, it is too faint to be visible to the naked eye but can be viewed with a small telescope. The star lies at a distance of 182 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −24 km/s.

Properties The spectrum of HD 159868 matches a G-type main-sequence star with a stellar classification of G5V. It has a relatively low surface gravity for its class, which suggests it is slightly evolved off the main sequence. The star is chromospherically inactive with a slow rotation rate, having a projected rotational velocity of 2.1 km/s. It is an estimated 6.6 billion years old with 8–12% more mass than the Sun and nearly double the Sun's radius. The star is radiating 3.8 times the luminosity of the Sun from its photosphere at an effective temperature of 5,558 K.

Planetary system In 2007, a planet of the star was announced by astronomer Simon J. O'Toole and collaborators. The planet (designated HD 159868 b) is likely to be a gas giant. Preliminary orbital elements suggested the orbit is extremely eccentric at the average distance of 2 astronomical units (AU), ranging as close as 0.62 AU to as far as 3.38 AU. In 2012, a second planet of the star was announced by astronomer Robert A. Wittenmyer and associates. The orbit of the first planet was significantly revised during the investigation.

See also HD 219828 HD 28185 List of extrasolar planets

References

External links "HD 159868". Exoplanets. Archived from the original on 2008-05-14. Retrieved 2008-07-19. "Notes for star HD 159868". Extrasolar Planets Encyclopaedia. Archived from the original on July 2, 2007. Retrieved 2008-07-19.

Worked examples

Example 1 — a first encounter with HD 159868

Start with the simplest possible case. Write down what HD 159868 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 159868 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 159868 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 159868

In research: HD 159868 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 159868 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 159868 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, G-type main-sequence stars, Gliese and GJ objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 159868 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 159868 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 159868 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 159868 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 159868 in simple terms?

Why does HD 159868 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 159868?

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 159868.