astronomy

GQ Lupi b

GQ Lupi b 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 Lupi b rather than just read about it. In short: GQ Lupi b, or GQ Lupi B is a substellar companion to the T Tauri star GQ Lupi. Classified as either an exoplanet or a brown dwarf, this object is still in the early stages of its formation, accreting gas from its circumplanetary disk.

Key takeaways

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

Reference excerpt

GQ Lupi b, or GQ Lupi B is a substellar companion to the T Tauri star GQ Lupi. Classified as either an exoplanet or a brown dwarf, this object is still in the early stages of its formation, accreting gas from its circumplanetary disk. GQ Lupi b is orbiting at nearly 100 astronomical units from the star, with an estimated orbital period around a millennium. The object was discovered by R. Neuhäuser et al., through direct imaging and announced in April 2005, less than a month before the full confirmation of 2M1207b was announced. Along with 2M1207b, this was one of the first extrasolar planet candidates to be directly imaged.

Discovery GQ Lupi b was discovered in 2005 by a team led by R. Neuhäuser. By analysing data taken from the NACO adaptive optics aboard the Very Large Telescope, they discovered a faint companion to GQ Lupi A, and combining this with archival observations from the Subaru and Hubble Space Telescopes, they were able to confirm that the companion co-moves with the star and thus is gravitationally bound. At the time, this was considered to be the first direct imaging discovery of a planetary-mass companion orbiting a star. The image was made with the European Southern Observatory's VLT telescope at the Paranal Observatory, Chile on June 25, 2004. In 2006, the IAU's Working Group on Extrasolar Planets described GQ Lup b as a "possible planetary-mass companion to a young star".

Location GQ Lupi b is within the Lupus I molecular cloud, a star-forming region that is part of the Scorpius–Centaurus association. The cloud is located at a distance of roughly 460 ± 160 light-years (140 ± 50 parsecs). The GQ Lupi system is located at a distance of 501.7+2.2−2.7 ly (153.82+0.67−0.82 pc). As seen from Earth, it is within the constellation of Lupus.

Orbit and surroundings GQ Lupi b orbits at a semi-major axis of 98 astronomical units from its host star, having a moderate orbital eccentricity of 0.35. This means that the farthest passage (apoastron) occurs at 132 au while the closest passage (periastron) occurs at 64 au. The orbital period is of roughly 920 years, and the orbit's inclination relative to Earth is 48°.

Host star

GQ Lupi is a T Tauri star, with a variable apparent magnitude ranging from 11.3 at brightest and 14.3 at faintest. Its spectral type is K7Ve, with the 'e' indicating emission lines in the spectrum, which in classical T Tauri stars such as GQ Lupi results from a surrounding, extensive disk. The star has 1.03±0.05 times the mass of the Sun, 1.75+0.06−0.07 times the Sun's radius, and an effective temperature of 4306±35 K. Its estimated age is 2.8+1.8−1.1 million years, which is thought to be the same of GQ Lupi b. GQ Lupi also likely has a more widely-separated stellar companion, named 2MASS J15491331-3539118 or GQ Lupi C. This star has a projected separation of from 2400 au from the primary, has roughly 0.15 times the mass of the Sun, 0.9 times the Sun's radius, and an effective temperature of 3200 K.

Circumplanetary material Emission by hydrogen in the near-infrared (Paschen-beta) was first detected in 2007 with the Very Large Telescope (VLT). This was interpreted as a sign of accretion of material from a disk. Additionally H-alpha emission was detected with Hubble. As a very young object, GQ Lupi b is still embedded in its circumplanetary disk, composed by gas and dust, and accretes gas from it. The disk has a radius of 80±10 RJ and is inclined at 85.6±0.5° relative to Earth. There is evidence for a cavity within the disk, which has been suggested to be caused the accretion of dust by forming satellites. Thus, the disk of GQ Lupi b may be in its late stages where the formation of satellites is taking place and the inner parts were already cleared. The accretion rate of GQ Lupi b is estimated at 3.2×10−7 MJ per year.

Physical parameters As a young object that is still contracting, GQ Lupi b still retain a fairly large radius and a hot temperature when compared to older objects. Cold substellar objects are predicted to have radii below 1.2 RJ, while GQ Lupi b is over double or triple this.

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Illustrations

Worked examples

Example 1 — a first encounter with GQ Lupi b

Start with the simplest possible case. Write down what GQ Lupi b 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 Lupi b 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 Lupi b 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 Lupi b

In research: GQ Lupi b 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 Lupi b 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 Lupi b is common in secondary-school and first-year university syllabi. It links to neighbouring topics Brown dwarfs, Exoplanets detected by direct imaging, Exoplanets discovered in 2005, so understanding it makes those chapters shorter.
In everyday life: Look for GQ Lupi b 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 Lupi b in 20 minutes

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

Frequently asked questions

What is GQ Lupi b in simple terms?

Why does GQ Lupi b 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 Lupi b?

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 Lupi b.