astronomy

WISE 1639−6847

WISE 1639−6847 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 WISE 1639−6847 rather than just read about it. In short: WISE J163940.83−684738.6 (designation is abbreviated to WISE 1639−6847, or W1639) is a brown dwarf of spectral class Y0 pec, located in the constellation Triangulum Australe at 15.5 light-years from Earth. It is the closest star or brown dwarf in its constellation, and the second closest known Y dwarf as of February 2024.

Key takeaways

WISE 1639−6847 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect WISE 1639−6847 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WISE 1639−6847 from memory before moving on to harder problems.

Reference excerpt

WISE J163940.83−684738.6 (designation is abbreviated to WISE 1639−6847, or W1639) is a brown dwarf of spectral class Y0 pec, located in the constellation Triangulum Australe at 15.5 light-years from Earth. It is the closest star or brown dwarf in its constellation, and the second closest known Y dwarf as of February 2024.

Discovery WISE 1639−6847 was discovered in 2012 by C. G. Tinney et al. from data, collected by Wide-field Infrared Survey Explorer (WISE) Earth-orbiting satellite—NASA infrared-wavelength 40 cm (16 in) space telescope, which mission lasted from December 2009 to February 2011. In 2012 Tinney et al. carried out follow-up observations of WISE 1639−6847 using the FourStar infrared mosaic camera mounted on the 6.5 m Magellan Baade telescope at Las Campanas Observatory, Chile (on 2012 May 10–11 (UT)); and spectroscopy using the Folded-port Infrared Echellette (FIRE) also mounted on the 6.5 m Magellan Baade telescope (on 2012 July 10 (UT)). In 2012 Tinney et al. published a paper in The Astrophysical Journal, where they presented discovery of a newfound by WISE Y-type brown dwarf WISE 1639−6847 (the only brown dwarf discovery, presented in the article): the paper was accepted for publication on 20 September 2012, submitted to arXiv on 27 September 2012, and published in November 2012.

Physical properties WISE 1639−6847 has absolute magnitude in J-band 22.14 ± 0.22. WISE 1639−6847 was first classified to have a spectral type between Y0 and Y0.5. Observations with Hubble WFC3 near-infrared grism spectroscopy showed that the J-band peak matched with the Y0 standard. The Y-band peak and the Y-J color showed that it was unusual compared to other Y-dwarfs and therefore a spectral type of Y0 pec was applied. The pec stands for peculiar or unusual. Modelling of this Y-dwarf struggles to reproduce the spectrum. Only with rather unrealistic high temperature and low gravity it was possible to reproduce the spectrum.

See also List of nearest stars and brown dwarfs List of Y-dwarfs

References

Illustrations

Worked examples

Example 1 — a first encounter with WISE 1639−6847

Start with the simplest possible case. Write down what WISE 1639−6847 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 WISE 1639−6847 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 WISE 1639−6847 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 WISE 1639−6847

In research: WISE 1639−6847 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 WISE 1639−6847 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: WISE 1639−6847 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 2012, Brown dwarfs, Triangulum Australe, so understanding it makes those chapters shorter.
In everyday life: Look for WISE 1639−6847 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 WISE 1639−6847 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WISE 1639−6847 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 WISE 1639−6847 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WISE 1639−6847 in simple terms?

Why does WISE 1639−6847 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 WISE 1639−6847?

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 WISE 1639−6847.