ArticleslgStudy

astronomy

TrES-2b

TrES-2b 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 TrES-2b rather than just read about it. In short: TrES-2b (also known as Kepler-1a or GSC 03549-02811a) is an extrasolar planet orbiting the star TrES-2A located 750 light years away from the Solar System. The planet was identified in 2011 as the darkest known exoplanet, reflecting less than 1% of any light that hits it.

TrES-2b — main illustration
TrES-2b — illustration

Key takeaways

  • TrES-2b belongs to astronomy; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect TrES-2b to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of TrES-2b from memory before moving on to harder problems.

Reference excerpt

TrES-2b (also known as Kepler-1a or GSC 03549-02811a) is an extrasolar planet orbiting the star TrES-2A located 750 light years away from the Solar System. The planet was identified in 2011 as the darkest known exoplanet, reflecting less than 1% of any light that hits it. Reflecting less light than charcoal, on the surface the planet is said to be pitch black, although it does emit dim red glow due to its temperature. The planet's mass and radius indicate that it is a gas giant with a bulk composition similar to that of Jupiter. Unlike Jupiter, but similar to many planets detected around other stars, TrES-2b is located very close to its star and belongs to the class of planets known as hot Jupiters. This system was within the field of view of the Kepler spacecraft. This planet continues to be studied by other projects, and the parameters are continuously improving. A 2007 study improved stellar and planetary parameters. A 2008 study concluded that the TrES-2 system is a binary star system. This significantly affects the values for the stellar and the planetary parameters.

Discovery

TrES-2b was discovered on August 21, 2006 by the Trans-Atlantic Exoplanet Survey (TrES) by detecting the transit of the planet across its parent star using Sleuth (Palomar Observatory, California) and PSST (Lowell Observatory, Arizona), part of the TrES network of 10–cm telescopes. The discovery was confirmed by the W. M. Keck Observatory in September 2006, by measuring the radial velocity of the star that hosts TrES-2b.

Spin-orbit angle In August 2008 more details of the relationship between the parent star and the orbit of the planet were published. The orbit was determined to be tilted by −9±12° from the stellar equator. The orbital direction was determined to be in the same direction as the star's rotation (prograde).

Kepler mission

NASA launched Kepler in March 2009. The spacecraft is dedicated to the discovery of extrasolar planets by the transit method from solar orbit. In April 2009 the project released the first light images from the spacecraft, and TrES-2b was one of two objects highlighted in these images. Although TrES-2b is not the only known exoplanet in the field of view of this spacecraft it is the only one identified in the first light images. This object is important for calibration and check-out.

The Kepler mission also managed to detect the mass of the planet from Kepler data alone through the analysis of the light curve of the host star. In addition to detecting the planet directly, the planet was also detected by analysis of the star brightness caused by the gravitational tug of TrES-2b by shape distortion of the host star and by light variations due to Doppler beaming.

Physical characteristics

Albedo The first important result from the Kepler Mission about TrES-2b is an extremely low geometric albedo measured in 2011, making it the intrinsically darkest known exoplanet. If the entire day–night contrast were due to geometric albedo, it would be 2.53%, but modeling suggests that much of this is dayside emission due to the planet's high temperature and the true albedo is much lower. It is estimated to be less than 1%, and for the best-fit model, it is about 0.04%. This makes TrES-2b the darkest known exoplanet, reflecting less of the light that strikes it than coal or black acrylic paint. It isn't clear why the planet is so dark. One reason could be the absence of reflective clouds such as those that make Jupiter so bright due to TrES-2b's proximity to its parent star and the consequent high temperature. Another reason could be the presence in the atmosphere of light-absorbing chemicals such as vaporized sodium, potassium, or gaseous titanium oxide; however, Kipping and Spiegel excluded heavy oxides of titanium and vanadium from their models, as it seems unrealistic that condensed, heavy compounds be present in the upper atmosphere. They also note that in general, hot Jupiters are expected to be dark, because "absorption due to the broad wings of the sodium and potassium D lines is thought to dominate their visible spectra", and, apart from that of Kepler-7b (38±12%), albedo measurements for hot Jupiters have generally given only upper limits.

Temperature The planet is likely to be tidally locked to the parent star. In 2015, the planetary nightside temperature was estimated to be equal to 1885+51−66 K. Although it reflects very little light, it emits a dim reddish glow due to its temperature.

See also WASP-12b, another hot Jupiter with a low albedo List of largest exoplanets List of nearest exoplanets

Notes

References

External links

Host to 'Hot Jupiter' (labeled) NASA, 2009-04-16 TrES-2: Most Massive Nearby Transiting Exoplanet Jupiter-Sized Transiting Planet Found by Astronomers Using Novel Telescope Network Light curve for TrES-2b using differential photometry

Illustrations

TrES-2b illustration
TrES-2b: The radial velocity of GSC 03549–02811 over time, caused by the presence of TrES-2 b.
The radial velocity of GSC 03549–02811 over time, caused by the presence of TrES-2 b.
TrES-2b: Size comparison of TrES-2b with Jupiter
Size comparison of TrES-2b with Jupiter
TrES-2b: The GSC 03549-02811 system as seen from the Kepler spacecraft. (Celestial north is toward the lower left corner and the subject is in the center of the photograph as seen clearly in the enlarged view.)
The GSC 03549-02811 system as seen from the Kepler spacecraft. (Celestial north is toward the lower left corner and the subject is in the center of the photograph as seen clearly in the enlarged view.)
TrES-2b: An artist's impression of TrES-2b
An artist's impression of TrES-2b

Worked examples

Example 1 — a first encounter with TrES-2b

Start with the simplest possible case. Write down what TrES-2b 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 TrES-2b 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 TrES-2b 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 TrES-2b

In research
TrES-2b 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 TrES-2b 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
TrES-2b is common in secondary-school and first-year university syllabi. It links to neighbouring topics Draco (constellation), Exoplanets discovered in 2006, Exoplanets with Kepler designations, so understanding it makes those chapters shorter.
In everyday life
Look for TrES-2b 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study TrES-2b in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what TrES-2b 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 TrES-2b out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TrES-2b in simple terms?

TrES-2b (also known as Kepler-1a or GSC 03549-02811a) is an extrasolar planet orbiting the star TrES-2A located 750 light years away from the Solar System. The planet was identified in 2011 as the darkest known exoplanet, reflecting less than 1% of any light that hits it.

Why does TrES-2b 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 TrES-2b?

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 TrES-2b.

Tags

  • Draco (constellation)
  • Exoplanets discovered in 2006
  • Exoplanets with Kepler designations
  • Giant planets
  • Hot Jupiters
  • Transiting exoplanets

Keep exploring