astronomy

L 98-59 d

L 98-59 d 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 L 98-59 d rather than just read about it. In short: L98-59d or TOI-175 d is an exoplanet orbiting the star L 98-59 34.6 light years from Earth. L 98-59 d is the third, potentially fourth, planet in its system.

Key takeaways

L 98-59 d belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect L 98-59 d to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of L 98-59 d from memory before moving on to harder problems.

Reference excerpt

L98-59d or TOI-175 d is an exoplanet orbiting the star L 98-59 34.6 light years from Earth. L 98-59 d is the third, potentially fourth, planet in its system. Its discovery was announced along with L 98-59 b and c in March 2019. L 98-59 d is a super-Earth having a mass of 1.64 M🜨 and has a radius of 1.627 R🜨. It takes 7.450729 days to orbit L 98-59 and orbits at a distance of 4.94% Earth's orbit and has one of the least eccentric orbits in its system with an eccentricity of 0.006. JWST observations of this planet found an atmosphere made of hydrogen, hydrogen sulfide and sulfur dioxide and also found a lava ocean on its surface.

Atmosphere In March 2026 JWST discovered a cloud-free atmosphere around L 98-59 d made of hydrogen, hydrogen sulfide and sulfur dioxide.

Magma ocean The same study that found an atmosphere around this planet found a molten surface made of lava with a temperature of 1900°C.

Formation L 98-59 d formed as a sub-Neptune about 5 billion years ago and its star stripped its atmosphere away. But L 98-59d had an abundance of hydrogen, hydrogen sulfide and sulfur dioxide and over time due to volcanic activity formed an atmosphere with the same elements. L 98-59d has a core mass of 66% Earth's total mass. Its core has a radius 55% the radius of Earth. The L 98-59d we see today is the dying remnant of a mini-Neptune in the process of losing its atmosphere and becoming airless.

References

Illustrations

Worked examples

Example 1 — a first encounter with L 98-59 d

Start with the simplest possible case. Write down what L 98-59 d 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 L 98-59 d 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 L 98-59 d 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 L 98-59 d

In research: L 98-59 d 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 L 98-59 d 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: L 98-59 d is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exoplanets discovered by TESS, Exoplanets discovered in 2019, Transiting exoplanets, so understanding it makes those chapters shorter.
In everyday life: Look for L 98-59 d 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 L 98-59 d in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what L 98-59 d 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 L 98-59 d out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is L 98-59 d in simple terms?

L98-59d or TOI-175 d is an exoplanet orbiting the star L 98-59 34.6 light years from Earth. L 98-59 d is the third, potentially fourth, planet in its system.

Why does L 98-59 d 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 L 98-59 d?

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 L 98-59 d.