astronomy

HD 147506

HD 147506 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 147506 rather than just read about it. In short: HD 147506, also known as HAT-P-2 and formally named Hunor, is a magnitude 8.7 F8 dwarf star that is somewhat larger and hotter than the Sun. The star is approximately 419 light-years (128 parsecs) from Earth and is positioned near the keystone of Hercules.

Key takeaways

HD 147506 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 147506 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 147506 from memory before moving on to harder problems.

Reference excerpt

HD 147506, also known as HAT-P-2 and formally named Hunor, is a magnitude 8.7 F8 dwarf star that is somewhat larger and hotter than the Sun. The star is approximately 419 light-years (128 parsecs) from Earth and is positioned near the keystone of Hercules. It is estimated to be 2 to 3 billion years old, towards the end of its main sequence life. There is one known transiting exoplanet, and a second planet not observed to transit.

Nomenclature The designation HD 147506 comes from the Henry Draper Catalogue. When the star was found to have a planet by the HATNet Project, it was assigned the designation HAT-P-2, indicating that it was the second star found to have a planet by this project. The star HAT-P-2 has the proper name Hunor. The name was selected in the NameExoWorlds campaign by Hungary, during the 100th anniversary of the IAU. Hunor was a legendary ancestor of the Huns and the Hungarian nation, and brother of Magor (name of the planet HAT-P-2b).

Variability In addition to being a planetary transit variable, there are also stellar pulsations induced by the planet. This is the first known instance of a planet inducing pulsations in its host star. The amplitude is very small at approximately 40 parts per million. These pulsations correspond to exact harmonics of the planet's orbital frequency, indicating they are of a tidal origin.

Planetary system Orbiting the star is HAT-P-2b, later named Magor, which was at the time of its discovery the most massive transiting exoplanet. At around 9 times the mass of Jupiter and an estimated surface temperature of ~900 kelvins, on a 5.6 day orbit, this planet is unlike any previously discovered transiting planet. The planet has a large mass (nine times the mass of Jupiter), and a surface gravity 25 times that exerted by the Earth. Its orbital eccentricity is very large (e = 0.5). Since tidal forces should have reduced the orbital eccentricity of this planet, it was speculated that another massive planet found outside the orbit of HAT-P-2b is in orbital resonance with HAT-P-2b. The planet was discovered by the HATNet Project, and the researchers there found the planet to be 10-20% larger than Jupiter. This discovery is important as it provides further support for the existing theory of planetary structure. Additional measurements taken over six years show a long-term linear trend in the radial velocity data consistent with a companion of 15 Jupiter masses or greater. Adaptive optics images were taken at the Keck telescope, and when combined with the radial velocity data show the maximum mass of the companion is that of an M dwarf star. In 2023 the presence of an outer companion, HAT-P-2c, was confirmed, and its mass found to be planetary at around 11 times that of Jupiter.

Worked examples

Example 1 — a first encounter with HD 147506

Start with the simplest possible case. Write down what HD 147506 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 147506 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 147506 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 147506

In research: HD 147506 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 147506 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 147506 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, F-type main-sequence stars, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 147506 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 147506 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 147506 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 147506 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 147506 in simple terms?

Why does HD 147506 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 147506?

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 147506.