astronomy

GW170104

GW170104 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 GW170104 rather than just read about it. In short: GW170104 was a gravitational wave signal detected by the LIGO observatory on 4 January 2017. On 1 June 2017, the LIGO and Virgo collaborations announced that they had reliably verified the signal, making it the third such signal announced, after GW150914 and GW151226, and fourth overall.

Key takeaways

GW170104 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GW170104 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GW170104 from memory before moving on to harder problems.

Reference excerpt

GW170104 was a gravitational wave signal detected by the LIGO observatory on 4 January 2017. On 1 June 2017, the LIGO and Virgo collaborations announced that they had reliably verified the signal, making it the third such signal announced, after GW150914 and GW151226, and fourth overall.

Event detection The signal was detected by LIGO at 10:11:58.6 UTC, with the Hanford detector picking it up 3 milliseconds before the Livingston detector. Automated analyses did not initially identify this event as information about the state of the Hanford detector was not being correctly recorded. The event was found by a researcher at the Max Planck Institute for Gravitational Physics by visual inspection of triggers from the Livingston detector. The gravitational wave frequency at peak GW strain was 160 to 199 Hz.

Astrophysical origin Analysis indicated the signal resulted from the inspiral and merger of a pair of black holes (BBH) with 31.2+8.4−6.0 and 19.4+5.3−5.9 times the mass of the Sun, at a distance of 880+450−390 megaparsecs (2.9+1.5−1.3 billion light years) from Earth. The resulting black hole had a mass of 48.7+5.7−4.6 solar masses, two solar masses having been radiated away as gravitational energy. The peak luminosity of GW170104 was 3.1+0.7−1.3×1049 W.

Implication for binary black hole formation The spin axes of the black holes were likely misaligned with the axis of the binary orbit. The probability that both spin axes were positively aligned with the orbit is less than 5%. This configuration suggests that the binary black hole system was formed dynamically in a dense star cluster such as a globular cluster, i.e., as a result of gravitational interaction between stars and binary stars, in which case randomly aligned spin axes are expected. The competing scenario, that the system was formed out of a binary star system consisting of two normal (main sequence) stars, is not ruled out but is disfavored as black holes formed in such a binary are more likely to have positively aligned spins.

Graviton mass upper limit The analysis of GW170104 yielded a new upper bound on the mass of gravitons, if gravitons are massive at all. The graviton's Compton wavelength is at least 1.6×1016 m, or about 1.6 light-years, corresponding to a graviton mass of no more than 7.7×10−23 eV/c2. This Compton wavelength is about 9×109 times greater than the gravitational wavelength of the GW170104 event.

See also Gravitational-wave astronomy List of gravitational wave observations

References

Illustrations

Worked examples

Example 1 — a first encounter with GW170104

Start with the simplest possible case. Write down what GW170104 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 GW170104 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 GW170104 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 GW170104

In research: GW170104 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 GW170104 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: GW170104 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2017 in outer space, 2017 in science, Binary stars, so understanding it makes those chapters shorter.
In everyday life: Look for GW170104 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 GW170104 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GW170104 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 GW170104 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GW170104 in simple terms?

Why does GW170104 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 GW170104?

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 GW170104.