astronomy

Gliese 176

Gliese 176 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 176 rather than just read about it. In short: Gliese 176 is a small star with an orbiting exoplanet in the constellation of Taurus. With an apparent visual magnitude of 9.95, it is too faint to be visible to the naked eye but is the nearest star in the constellation, with a distance of 30.9 light years based on parallax measurements, and is drifting further away with a heliocentric radial velocity of 26.4 km/s.

Key takeaways

Gliese 176 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 176 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 176 from memory before moving on to harder problems.

Reference excerpt

Gliese 176 is a small star with an orbiting exoplanet in the constellation of Taurus. With an apparent visual magnitude of 9.95, it is too faint to be visible to the naked eye but is the nearest star in the constellation, with a distance of 30.9 light years based on parallax measurements, and is drifting further away with a heliocentric radial velocity of 26.4 km/s. This is an M-type main-sequence star, sometimes called a red dwarf, with a stellar classification of M2V. It has 49% of the Sun's mass and 47% of the radius of the Sun. The star is radiating just 3.5% of the luminosity of the Sun from its photosphere at an effective temperature of 3,632 K. It is estimated to be around nine billion years old, and is spinning slowly with a rotation period of 40 days. The star is orbited by a Super-Earth.

Planetary system A planetary companion to Gliese 176 was announced in 2008. Radial velocity observations with the Hobby-Eberly Telescope (HET) showed a 10.24-day periodicity, which was interpreted as being caused by a planet. With a semi-amplitude of 11.6 m/s, its minimum mass equated to 24.5 Earth masses, or approximately 1.4 Neptune masses. Observations with the HARPS spectrograph could not confirm the 10.24-day variation. Instead, two other periodicities were detected at 8.78 and 40.0 days, with amplitudes below the HET observational errors. The 40-day variation coincides with the rotational period of the star and is therefore caused by activity, but the shorter-period variation is not explained by activity and is therefore caused by a planet. Its semi-amplitude of 4.1 m/s corresponds to a minimum mass of 8.4 Earth masses, making the planet a Super-Earth. In an independent study, observations with Keck-HIRES also failed to confirm the 10.24-day signal. An 8.77-day periodicity - corresponding to the planet announced by the HARPS team - was detected to intermediate significance, though it was not deemed significant enough to claim a planetary cause with their data alone.

See also List of extrasolar planets Gliese 674

References

Worked examples

Example 1 — a first encounter with Gliese 176

Start with the simplest possible case. Write down what Gliese 176 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 176 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 176 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 176

In research: Gliese 176 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 176 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 176 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, Gliese and GJ objects, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 176 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 176 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 176 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 176 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 176 in simple terms?

Why does Gliese 176 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 176?

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 176.