astronomy

HAT-P-38b

HAT-P-38b 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 HAT-P-38b rather than just read about it. In short: HAT-P-38b, formally named Hiisi, is a transiting exoplanet orbiting the G-type star HAT-P-38 821 light-years from the Solar System in the constellation Triangulum. Nomenclature The planet's designation is derived from the host star's designation and the fact that it was the first planet to be discovered around the star, hence the "b" in its name.

Key takeaways

HAT-P-38b belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HAT-P-38b to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HAT-P-38b from memory before moving on to harder problems.

Reference excerpt

HAT-P-38b, formally named Hiisi, is a transiting exoplanet orbiting the G-type star HAT-P-38 821 light-years from the Solar System in the constellation Triangulum.

Nomenclature The planet's designation is derived from the host star's designation and the fact that it was the first planet to be discovered around the star, hence the "b" in its name. In 2019, it was selected for the second NameExoWorlds campaign for Finland as part of the IAU's 100th anniversary. The approved name for the planet is Hiisi, which represents sacred localities and later evil spirits from Finnic mythology. It shares this name with the binary companion of the trans-Neptunian object 47171 Lempo.

Discovery The transits of HAT-P-38 were first observed between August and November 2010 by using two telescopes related to the HATNet Project: The HAT-6 telescope in Arizona and the HAT-8 telescope in Hawaii. Astronomers observed a transit curve with a period of 4.64033 days. Later observations of the star's radial velocity using the High Dispersion Spectrograph confirmed HAT-P-38b's planetary status and it also yielded its mass in the process.

Properties HAT-P-38b is a hot Saturn that takes over 4 days to circle its host star in a relatively circular and tight orbit; it has a separation of 0.0519 astronomical units. HAT-P-38b has 26.6% the mass of Jupiter, which is similar to that of Saturn. However, tidal heating from HAT-P-38 causes the planet to bloat to 82.5% the radius of Jupiter. It has an equilibrium temperature of 1,082 K. The planet has a density of 590 kg/m3, which is half of that of water (the density of water is 1,000 kg/m3). The average gravitational acceleration of the planet is 9.77 m/s2, which is slightly smaller compared to the gravitational acceleration at the surface of the Earth.

In 2017, the atmospheres of HAT-P-38b and WASP-67b were compared since both planets had similar properties. Giovanni Bruno and colleagues detected water vapor in both planets, with HAT-P-38b having the greater abundance in its atmosphere. This indicates that the atmosphere lacks clouds or hazes.

References

Illustrations

Worked examples

Example 1 — a first encounter with HAT-P-38b

Start with the simplest possible case. Write down what HAT-P-38b 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 HAT-P-38b 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 HAT-P-38b 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 HAT-P-38b

In research: HAT-P-38b 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 HAT-P-38b 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: HAT-P-38b is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exoplanets discovered by HATNet, Exoplanets discovered in 2012, Exoplanets with proper names, so understanding it makes those chapters shorter.
In everyday life: Look for HAT-P-38b 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 HAT-P-38b in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HAT-P-38b 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 HAT-P-38b out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HAT-P-38b in simple terms?

HAT-P-38b, formally named Hiisi, is a transiting exoplanet orbiting the G-type star HAT-P-38 821 light-years from the Solar System in the constellation Triangulum. Nomenclature The planet's designation is derived from the host star's designation and the fact that it was the first planet to be disco…

Why does HAT-P-38b 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 HAT-P-38b?

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 HAT-P-38b.