astronomy

GRS 1915+105

GRS 1915+105 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 GRS 1915+105 rather than just read about it. In short: GRS 1915+105 or V1487 Aquilae is an X-ray binary star system containing a main sequence star and a black hole. Transfer of material from the star to the black hole generates a relativistic jet, making this a microquasar system.

Key takeaways

GRS 1915+105 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GRS 1915+105 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GRS 1915+105 from memory before moving on to harder problems.

Reference excerpt

GRS 1915+105 or V1487 Aquilae is an X-ray binary star system containing a main sequence star and a black hole. Transfer of material from the star to the black hole generates a relativistic jet, making this a microquasar system. The jet exhibits apparent superluminal motion. It was discovered on August 15, 1992 by the WATCH all-sky monitor aboard Granat. "GRS" stands for "GRANAT source", "1915" is the right ascension (19 hours and 15 minutes) and "105" reflects the approximate declination (10 degrees and 56 arcminutes). The near-infrared counterpart was determined by spectroscopic observations. The binary system lies 11,000 parsecs away in Aquila. The black hole in GRS 1915+105 is 10 to 18 solar masses. The black hole rotates at least 950 times per second, giving it a spin parameter >0.82 (1.0 is the theoretical maximum).

Galactic superluminal source

In 1994, GRS 1915+105 became the first known galactic source that ejects material with apparent superluminal motion velocities. Observations with high resolution radio telescopes such as VLA, MERLIN, and VLBI show a bi-polar outflow of charged particles, which emit synchrotron radiation at radio frequencies. These studies have shown that the apparent superluminal motion is due to a relativistic effect known as relativistic aberration, where the intrinsic velocity of ejecta is actually about 90% the speed of light.

Growth regulation Repeat observations by the Chandra X-Ray Observatory over the period of a decade have revealed what may be a mechanism for self-regulation of the rate of growth of GRS 1915+105. The jet of materials being ejected is occasionally choked off by a hot wind blowing off the accretion disk. The wind deprives the jet of materials needed to sustain it. When the wind dies down, the jet returns.

Illustrations

Worked examples

Example 1 — a first encounter with GRS 1915+105

Start with the simplest possible case. Write down what GRS 1915+105 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 GRS 1915+105 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 GRS 1915+105 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 GRS 1915+105

In research: GRS 1915+105 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 GRS 1915+105 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: GRS 1915+105 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aquila (constellation), Black hole X-ray binaries, K-type giants, so understanding it makes those chapters shorter.
In everyday life: Look for GRS 1915+105 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 GRS 1915+105 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GRS 1915+105 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 GRS 1915+105 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GRS 1915+105 in simple terms?

Why does GRS 1915+105 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 GRS 1915+105?

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 GRS 1915+105.