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GQ Leonis

GQ Leonis 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 GQ Leonis rather than just read about it. In short: GQ Leonis (GSC 00870-00798) is a variable star located in the zodiac constellation of Leo, close to the second-magnitude star Denebola. With an apparent magnitude of 10.8, it is too faint to be seen by the naked eye but observable using a telescope with an aperture of 35 mm (1.4 in) or larger.

GQ Leonis — main illustration
GQ Leonis — illustration

Key takeaways

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

Reference excerpt

GQ Leonis (GSC 00870-00798) is a variable star located in the zodiac constellation of Leo, close to the second-magnitude star Denebola. With an apparent magnitude of 10.8, it is too faint to be seen by the naked eye but observable using a telescope with an aperture of 35 mm (1.4 in) or larger. It is situated at a distance of 200 light-years (61 parsecs) according to Gaia EDR3 parallax measurements, and is advancing towards the Solar System at a heliocentric radial velocity of −12.121 km/s.

Physical properties This is a K-type main-sequence star with the spectral type K5Ve, where the "e" suffix denotes the presence of emission lines. It is considered to be a field star, not part of any star cluster. It is expected to have a radius of about 0.8 R☉, and shines at an effective temperature of 4,364 K (7,396 °F), giving it an orange hue. It is poorer in heavy elements than the Sun with a metallicity of −0.171, meaning it has 10−0.171 ≈ 67% the Sun's iron content. Age estimates vary between publications, but the consensus is that it is young and very active, as evidenced by strong emission in the calcium H and K lines and the Balmer series. The star is also a source of X-rays and extreme ultraviolet (EUV) radiation.

Variability

In 2001, the star was reported to show low-amplitude photometric variations with a period of 4.45 days. It was suspected that the star was a BY Draconis variable due to the period paired with the X-ray and EUV emissions. This was confirmed in 2004 in a paper which also newly classified HD 77191 and V573 Puppis as BY Dra variables. The star received its variable-star designation GQ Leonis in 2003.

Stellar companions Slow fluctuations are known to occur in the star's radial velocity. In a 2019 study, a 572-day (1.57 a) period was mentioned to fit the observed variations, but other periods remain possible. This object is also a visual binary, designated MET 57Aa/Ab in the Washington Double Star Catalog, with a separation of 0.25 arcseconds and a period of roughly 45 years. Additionally, an optical component (MET 57B) exists 9.5 arcseconds away.

References

Illustrations

GQ Leonis illustration
GQ Leonis: Light curves for GQ Leonis. The upper panel shows the short term variability as seen by TESS,[15] and the lower panel shows the brightness over a much longer time interval as seen by ASASSN.[16]
Light curves for GQ Leonis. The upper panel shows the short term variability as seen by TESS,[15] and the lower panel shows the brightness over a much longer time interval as seen by ASASSN.[16]

Worked examples

Example 1 — a first encounter with GQ Leonis

Start with the simplest possible case. Write down what GQ Leonis 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 GQ Leonis 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 GQ Leonis 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 GQ Leonis

In research
GQ Leonis 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 GQ Leonis 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
GQ Leonis is common in secondary-school and first-year university syllabi. It links to neighbouring topics BY Draconis variables, Binary stars, Emission-line stars, so understanding it makes those chapters shorter.
In everyday life
Look for GQ Leonis 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 GQ Leonis in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what GQ Leonis means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain GQ Leonis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GQ Leonis in simple terms?

GQ Leonis (GSC 00870-00798) is a variable star located in the zodiac constellation of Leo, close to the second-magnitude star Denebola. With an apparent magnitude of 10.8, it is too faint to be seen by the naked eye but observable using a telescope with an aperture of 35 mm (1.4 in) or larger.

Why does GQ Leonis 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 GQ Leonis?

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 GQ Leonis.

Tags

  • BY Draconis variables
  • Binary stars
  • Emission-line stars
  • K-type main-sequence stars
  • Leo (constellation)
  • Objects with variable star designations

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