astronomy

TRAPPIST-1h

TRAPPIST-1h 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 TRAPPIST-1h rather than just read about it. In short: TRAPPIST-1h is an exoplanet orbiting around the ultra-cool red dwarf star TRAPPIST-1, located 40.7 light-years (12.5 parsecs) away from Earth in the constellation Aquarius. The planet is one of seven planets to be discovered orbiting the star in 2017 using observations from the Spitzer Space Telescope.

Key takeaways

TRAPPIST-1h belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect TRAPPIST-1h to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of TRAPPIST-1h from memory before moving on to harder problems.

Reference excerpt

TRAPPIST-1h is an exoplanet orbiting around the ultra-cool red dwarf star TRAPPIST-1, located 40.7 light-years (12.5 parsecs) away from Earth in the constellation Aquarius. The planet is one of seven planets to be discovered orbiting the star in 2017 using observations from the Spitzer Space Telescope. In the following years, more studies were able to refine its physical parameters. The outermost known planet in its system, it is roughly one third the mass of Earth, and about 76% as large. Its relatively low density indicates that it is likely water-rich, like several other planets in the system.

Physical characteristics

Mass, radius, and temperature TRAPPIST-1h has a radius of 0.755 R🜨, a mass of 0.326 M🜨, and about 57% Earth's surface gravity. It was initially estimated to have a density of 3.97 g/cm3, similar to that of Mars. Given this density, about ≤5% of its mass may be water, likely in the form of a thick ice shell, since it only receives about 13% of the stellar flux that Earth does. It has an equilibrium temperature of 169 K (−104 °C; −155 °F), similar to that of Earth's south pole.

Host star

TRAPPIST-1h orbits the ultracool dwarf star TRAPPIST-1. It is 0.12 R☉ and 0.09 M☉, with a temperature of 2,566 K and an age of about 7.6 billion years old. For comparison, the Sun has a temperature of 5,778 K and is about 4.6 billion years old. TRAPPIST-1 is also very dim, with about 0.0005 times the luminosity of the Sun. The star's apparent magnitude, or how bright it appears from Earth's perspective, is 18.8. Therefore, it is too dim to be seen with the naked eye.

Orbit Despite it being the most distant known planet in its system, TRAPPIST-1h orbits its host star with an orbital period of about 18.77 days and an orbital distance of about 0.0619 AU. This is even smaller than Mercury's orbit around the Sun (which is about 0.38 AU). It is in 3:2 resonance with TRAPPIST-1g.

Stable liquid water Although TRAPPIST-1h's orbit falls near its star's frost line, it could harbor liquid water under an H2-rich atmosphere, either primordial or resulting from continuous outgassing combined with internal heating, although existence of such atmosphere was strongly disfavored by observations in 2021 and 2022. If ice-covered, it could also potentially harbor a subsurface ocean by way of tidal heating, which could lead to cryovolcanism in the form of erupting geysers.

Illustrations

Worked examples

Example 1 — a first encounter with TRAPPIST-1h

Start with the simplest possible case. Write down what TRAPPIST-1h 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 TRAPPIST-1h 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 TRAPPIST-1h 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 TRAPPIST-1h

In research: TRAPPIST-1h 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 TRAPPIST-1h 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: TRAPPIST-1h is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aquarius (constellation), Exoplanets discovered in 2017, Near-Earth-sized exoplanets, so understanding it makes those chapters shorter.
In everyday life: Look for TRAPPIST-1h 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 TRAPPIST-1h in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what TRAPPIST-1h 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 TRAPPIST-1h out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TRAPPIST-1h in simple terms?

Why does TRAPPIST-1h 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 TRAPPIST-1h?

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 TRAPPIST-1h.