astronomy

HD 154345

HD 154345 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 154345 rather than just read about it. In short: HD 154345 is a star in the northern constellation of Hercules. With an apparent visual magnitude of +6.76 it is a challenge to view with the naked eye, but using binoculars it is an easy target.

Key takeaways

HD 154345 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 154345 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 154345 from memory before moving on to harder problems.

Reference excerpt

HD 154345 is a star in the northern constellation of Hercules. With an apparent visual magnitude of +6.76 it is a challenge to view with the naked eye, but using binoculars it is an easy target. The distance to this star is 59.6 light years based on parallax, but it is drifting closer with a radial velocity of −47 km/s. At least one exoplanet is orbiting this star. The stellar classification of HD 154345 is G8V, matching an ordinary G-type main-sequence star that is generating energy by core hydrogen fusion. The magnetic activity cycle of this star is correlated with the radial velocity variations induced by its putative planetary companion. It is around four billion years old and is spinning with a rotation period of 28 days. The star is smaller and less massive than the Sun. It is radiating 62% of the luminosity of the Sun from its photosphere at an effective temperature of 5,557 K.

Planetary system In 2006, a long-period, wide-orbiting planet was observed by radial velocity, and published in May 2007, gaining the designation HD 154345 b. It has been called a "Jupiter twin". While the existence of HD 154345 b has been unclear due to the correlation of its orbital period with the star's activity cycle, a study in 2021 confirmed its planetary nature. The complete observation of its nine-year orbit rules out any interior planets of minimum mass (m sini) greater than 0.3 Jupiter. The star rotates at an inclination of 50+40−26 degrees relative to Earth. It is probable that the planet shares that inclination. In 2023, the inclination and true mass of HD 154345 b were determined via astrometry, consistent within the margin of error with the stellar rotational inclination. More precise measurements found a nearly edge-on inclination. The system's habitable zone stretches from 0.64 AU out to 1.26 AU, and is narrower than the Sun's. It forms a stable region where an Earth-mass exoplanet could orbit.

References

External links The Extrasolar Planets Encyclopedia: HD 154345

Illustrations

Worked examples

Example 1 — a first encounter with HD 154345

Start with the simplest possible case. Write down what HD 154345 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 154345 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 154345 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 154345

In research: HD 154345 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 154345 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 154345 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 154345 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 154345 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 154345 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 154345 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 154345 in simple terms?

HD 154345 is a star in the northern constellation of Hercules. With an apparent visual magnitude of +6.76 it is a challenge to view with the naked eye, but using binoculars it is an easy target.

Why does HD 154345 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 154345?

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 154345.