astronomy

Gliese 12

Gliese 12 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 Gliese 12 rather than just read about it. In short: Gliese 12 (GJ 12) is a red dwarf star located 39.7 light-years (12.2 parsecs) away in the constellation Pisces. It has about 24% the mass and 26% the radius of the Sun, and a temperature of about 3,296 K (3,023 °C; 5,473 °F).

Key takeaways

Gliese 12 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gliese 12 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 12 from memory before moving on to harder problems.

Reference excerpt

Gliese 12 (GJ 12) is a red dwarf star located 39.7 light-years (12.2 parsecs) away in the constellation Pisces. It has about 24% the mass and 26% the radius of the Sun, and a temperature of about 3,296 K (3,023 °C; 5,473 °F). It is an inactive star and hosts one known exoplanet.

Planetary system The transiting exoplanet Gliese 12 b was discovered by TESS, and two independent studies confirming it as a planet were published in May 2024. Gliese 12 b is similar in size to Earth and Venus, and completes an orbit around its star every 12.8 days. Initially its mass was poorly constrained but was determined to be less than 4 times that of Earth. Measurements gathered in 2025 studies provided mass measurements of 0.71 and 0.95 Earth masses (M🜨). The latter also measured a planetary radius of 0.934 R🜨, and found a density of 7.0+2.3−2.1 g/cm3, higher than the densities of the Solar System's terrestrial planets. This suggests a likely rocky composition, similar to Venus. While this, the former study used the discovery paper's radius (0.958 R🜨) and found a lower density that give less constraints on its composition. Scenarios such as an Earth-like composition, volatile-dominated composition, iron-poor, or even a combination are all plausible. Along with the planets of TRAPPIST-1 and LHS 1140 b, Gliese 12 b is one of the nearest known relatively temperate transiting exoplanets, and so is a promising target for the James Webb Space Telescope to determine whether it has retained an atmosphere. Gliese 12 b orbits slightly closer than the inner edge of its star's habitable zone, with an insolation between those of Earth and Venus. Its equilibrium temperature, assuming an albedo of zero, is 315 K (42 °C; 107 °F); if it has an atmosphere, the surface temperature would be greater than this. Assuming an albedo similar to Venus, the equilibrium temperature is 218 K (−55 °C; −67 °F).

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with Gliese 12

Start with the simplest possible case. Write down what Gliese 12 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 Gliese 12 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 Gliese 12 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 Gliese 12

In research: Gliese 12 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 Gliese 12 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: Gliese 12 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Gliese and GJ objects, M-type main-sequence stars, Pisces (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 12 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 Gliese 12 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 12 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 Gliese 12 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 12 in simple terms?

Why does Gliese 12 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 Gliese 12?

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 Gliese 12.