astronomy

Proxima Centauri d

Proxima Centauri 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 Proxima Centauri d rather than just read about it. In short: Proxima Centauri d (also called Proxima d) is a confirmed exoplanet orbiting the red dwarf star Proxima Centauri, the closest star to the Sun and part of the Alpha Centauri triple star system. Together with one or two other planets in the Proxima Centauri system, it is the closest known exoplanet to the Solar System, located approximately 4.2 light-years (1.3 parsecs; 40 trillion kilometres; 25 trillion miles) away…

Key takeaways

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

Reference excerpt

Proxima Centauri d (also called Proxima d) is a confirmed exoplanet orbiting the red dwarf star Proxima Centauri, the closest star to the Sun and part of the Alpha Centauri triple star system. Together with one or two other planets in the Proxima Centauri system, it is the closest known exoplanet to the Solar System, located approximately 4.2 light-years (1.3 parsecs; 40 trillion kilometres; 25 trillion miles) away in the constellation of Centaurus. The first signs of the exoplanet emerged as a weak 5.15-day signal in radial velocity data taken from the Very Large Telescope during a 2020 study on Proxima b's mass. This signal was formally proposed to be a candidate exoplanet by Faria et al. in a follow-up paper published in February 2022, and was independently confirmed in 2025.

Characteristics Proxima d is a sub-Earth at least one-quarter of the mass of Earth (or twice the mass of Mars), orbiting at roughly 0.029 AU (4.3 million km; 2.7 million mi) every 5.1 days. It is the least massive and innermost known planet of the Proxima Centauri system. It was the least massive exoplanet detected with the radial velocity method from 2022 until the discovery of Barnard's Star e in 2025. Its proximity to the star and short orbital period of 5.1 days suggest that it is likely tidally locked due to strong tidal forces. Although Proxima d orbits too close to its star to have a habitable equilibrium temperature (which likely reaches 360 K (87 °C; 188 °F) from about 190% of Earth's irradiation—assuming an Earth-like reflectivity, it is theoretically possible that Proxima d possesses polar regions with habitable temperatures. Since Proxima d has only been detected by the radial velocity method, only a minimum mass is known; the true mass depends on the orbital inclination. Assuming an inclination of 47°, coplanar with its host star's rotation, its true mass would be 0.357±0.072 M🜨. Initially, Proxima d was considered a candidate exoplanet because it had not been independently confirmed by more than one observatory, but some astronomers regarded it as confirmed because it could be detected via different methods of measuring the same radial velocity data. As of 2022, Proxima d had been detected by the ESPRESSO spectrograph on the Very Large Telescope, and also at a 2σ level (which does not constitute confirmation) by the HARPS spectrograph at the La Silla Observatory. Independent confirmation of Proxima d was achieved with the NIRPS spectrograph in work published in July 2025. In May 2026, a study of Proxima Centauri found evidence of star-planet magnetic interaction for both Proxima d and Proxima b, implying the presence of magnetic fields on both planets. Proxima d is estimated to have a magnetic field strength of around 16 G, much greater than that of Earth (0.25–0.65 G). Similar star-planet interaction was previously observed at YZ Ceti b.

See also List of nearest exoplanets List of smallest exoplanets Proxima Centauri c

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with Proxima Centauri d

Start with the simplest possible case. Write down what Proxima Centauri 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 Proxima Centauri 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 Proxima Centauri 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 Proxima Centauri d

In research: Proxima Centauri 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 Proxima Centauri 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: Proxima Centauri d is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exoplanets detected by radial velocity, Exoplanets discovered in 2022, Proxima Centauri, so understanding it makes those chapters shorter.
In everyday life: Look for Proxima Centauri 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 Proxima Centauri d in 20 minutes

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

Frequently asked questions

What is Proxima Centauri d in simple terms?

Why does Proxima Centauri 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 Proxima Centauri 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 Proxima Centauri d.