astronomy

HD 118203

HD 118203 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 118203 rather than just read about it. In short: HD 118203 is a star with an orbiting exoplanet located in the northern circumpolar constellation of Ursa Major. It has the proper name Liesma, which means flame, and it is the name of a character from the Latvian poem Staburags un Liesma (Staburags and Liesma).

Key takeaways

HD 118203 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 118203 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 118203 from memory before moving on to harder problems.

Reference excerpt

HD 118203 is a star with an orbiting exoplanet located in the northern circumpolar constellation of Ursa Major. It has the proper name Liesma, which means flame, and it is the name of a character from the Latvian poem Staburags un Liesma (Staburags and Liesma). The name was selected in the NameExoWorlds campaign by Latvia, during the 100th anniversary of the IAU. The apparent visual magnitude of HD 118203 is 8.06, which means it is invisible to the naked eye but it can be seen using binoculars or a telescope. Based on parallax measurements, it is located at a distance of 300 light years from the Sun. The star is drifting closer with a radial velocity of −29 km/s. Based on its position and space velocity this is most likely (97% chance) an older thin disk star. An exoplanet has been detected in a close orbit around the star. The spectrum of HD 118203 matches a G-type main-sequence star with a class of G0V. Despite that spectral classification, it appears to have evolved away from the main sequence to become a subgiant. It has a low level of chromospheric activity, which means a low level of radial velocity jitter for planet detection purposes. The star has 1.23 times the mass of the Sun and double the Sun's radius. It is around 5.4 billion years old and is spinning with a projected rotational velocity of 7.0 km/s. HD 118203 is radiating 3.8 times the luminosity of the Sun from its photosphere at an effective temperature of 5,741 K.

Planetary system In 2006, a hot Jupiter, HD 118203 b, was reported in an eccentric orbit around this star. It was discovered using the radial velocity method based on observation of high-metallicity stars begun in 2004. In 2020, it was found that this is a transiting planet, which allowed the mass and radius of the body to be determined. This exoplanet has more than double the mass of Jupiter and is 13% greater in radius. The fact that the parent star is among the brighter known planet hosts (as of 2020) makes it an interesting object for further study. This planet received the proper name Staburags in the 2019 NameExoWorlds campaign. In 2024, the star HD 118203 was found to display variability with a period matching that of planet b's orbit, suggesting magnetic interaction between the star and planet. Also in 2024, a second massive planet was discovered using radial velocity observations as well as Hipparcos and Gaia astrometry. HD 118203 c is about 11 times the mass of Jupiter and takes 14 years to complete an orbit around the star. Like planet b, the orbit of planet c is close to edge-on, suggesting an aligned planetary system. The presence of any additional transiting planets at least twice the size of Earth and with periods less than 100 days was ruled out by the observations.

Worked examples

Example 1 — a first encounter with HD 118203

Start with the simplest possible case. Write down what HD 118203 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 118203 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 118203 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 118203

In research: HD 118203 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 118203 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 118203 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, G-type main-sequence stars, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 118203 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 118203 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 118203 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 118203 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 118203 in simple terms?

Why does HD 118203 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 118203?

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 118203.