astronomy

GJ 3378

GJ 3378 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 GJ 3378 rather than just read about it. In short: GJ 3378, also known as LHS 1805, is a red dwarf star located around 25.2 light years (7.73 parsecs) away from Earth in the northern constellation of Camelopardalis. It is a small star with a mass of 0.3 solar masses and a radius of 0.3 solar radii.

Key takeaways

GJ 3378 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GJ 3378 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GJ 3378 from memory before moving on to harder problems.

Reference excerpt

GJ 3378, also known as LHS 1805, is a red dwarf star located around 25.2 light years (7.73 parsecs) away from Earth in the northern constellation of Camelopardalis. It is a small star with a mass of 0.3 solar masses and a radius of 0.3 solar radii. It is also a cool and quiet star with an effective temperature of 3,340 K and a luminosity of 0.9% solar luminosity. As of 2026, only one exoplanet, a super-Earth known as GJ 3378b, has been discovered orbiting within the conservative habitable zone. While it is likely that this planet has a terrestrial composition, it is placed near the cosmic shoreline meaning that it is potentially subjected to its parent star stripping away its atmosphere.

Characteristics GJ 3378 has a mass of about 0.26±0.02 solar masses and a radius of 0.279±0.005 solar radii. It has a luminosity of 2.1 solar luminosity and an effective temperature of 3,378±30 K. It was measured to have an average density of 17.7 g/cm3. It was initially given a rotational period of 95.1±2.3 days however Sabotta et al. (2021) reported a slower rotational period of 83.4 days. It has a metallicity that is close to the solar value, with an M/H dex of −0.10±0.10. The magnetic field of GJ 3378 has been clearly detected. It is small-scaled and has a mean strength of 150±50 Gauss (unit), making it a very quiet and cool star. Because GJ 3378 is a star with a mass lower than 0.35 solar masses, it is a fully-convective star.

Planetary system

Moutou et al. (2024) proposed evidence for an exoplanet and obtained data on its orbit and mass using observations from the SPIRou (Spectropolarimètre infrarouge) located at the Canada–France–Hawaii Telescope (CFH) in Hawaii, United States. They reported that this planet has an eccentric orbit and an orbital period of 24.73±0.06 days. They proposed a minimum mass of 5.26 Earth masses making it a sub-Neptunian or Super-Earth type planet. Robertson et al. (2026) conducted a survey of fully convective stars within the Solar neighborhood using the near-infrared spectrograph HPF on the Hobby-Eberly Telescope (HET) at McDonald Observatory in Texas, US. They refined the planet's orbital period down to 21.45±0.01 days and its minimum mass down to 2.3±0.4 Earth masses. They also gave estimates for its orbital distance and equilibrium temperature of 0.09673±0.00080 AU and 272±7 K respectively. Even with the reduced orbital period presented by Robertson et al. (2026), GJ 3378b would orbit within the conservative habitable zone (HZ) of the star where water could be present in its liquid state. Their reduced mass estimates would also make it more likely that this planet has a terrestrial composition. This could mean that it is a potentially habitable exoplanet. However GJ 3378b has been placed near the cosmic shoreline meaning that its atmosphere may have been lost due to radiative stripping by the parent red dwarf star.

References

Illustrations

Worked examples

Example 1 — a first encounter with GJ 3378

Start with the simplest possible case. Write down what GJ 3378 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 GJ 3378 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 GJ 3378 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 GJ 3378

In research: GJ 3378 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 GJ 3378 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: GJ 3378 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Camelopardalis, Gliese and GJ objects, M-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for GJ 3378 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 GJ 3378 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GJ 3378 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 GJ 3378 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GJ 3378 in simple terms?

Why does GJ 3378 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 GJ 3378?

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 GJ 3378.