astronomy

SDSS J1004+4112

SDSS J1004+4112 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 SDSS J1004+4112 rather than just read about it. In short: SDSS J1004+4112 is a gravitationally-lensed quasar located in the constellation of Leo Minor. It has a redshift of (z) 1.73 indicating a light-travel time distance of 10 billion light-years.

Key takeaways

SDSS J1004+4112 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SDSS J1004+4112 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SDSS J1004+4112 from memory before moving on to harder problems.

Reference excerpt

SDSS J1004+4112 is a gravitationally-lensed quasar located in the constellation of Leo Minor. It has a redshift of (z) 1.73 indicating a light-travel time distance of 10 billion light-years. This object was first discovered by a team of astronomers in December 2003.

Description SDSS J1004+4112 is classified a quadruple imaged quasar with a separation of 14.62 arcseconds. When imaged, it is separated into four components and lensed by a foreground galaxy cluster located at a redshift of (z) 0.68 based on follow-up imaging observations by Subaru Telescope, making this the first known object lensed by a cluster. A fifth image was discovered by astronomers based on a detection of a faint source located inside of the brightest cluster galaxy in the cluster. Further observations also showed there are seven other imaged galaxies behind SDSS J1004+4112 and the cluster, one of them located at (z) 3.332. Astronomers have found SDSS J1004+4112 displays multiple time delays. Based on optical monitoring data results by J. Fohlmeister, the time delay between the A and B components were calculated as 38.4 ± 2.0 days with B as the leading component. Later in 2008, Fohlmeister would measure the time delays again and found the C component has a time-delay of 2.3 years while also refining the time delay value of A and B components as 40.6 ± 1.8 days. An estimate of 2457 days was found for the D component lagging behind C, making this the longest known measured time delay. Astronomers also noted the A and B components showed evidence of microlensing with flux ratios switching from 0.44 ± 0.01 magnitude to 0.29 ± 0.01 magnitude and vice versa. Spectroscopy observations conducted in 2004 showed the quasar's spectra shows emission lines differences between the lens images. When probed, the A component displayed signs of strong enhancement in the emission line wing of its ionization lines, indicating the evidence of microlensing of the broad emission line region. A 28-day long amplification period was recorded for the emission lines of the A component. A study published in 2019 showed that the four components of SDSS J1004+4112 display polarization. Based on spectroscopy and polarimetric observations, astronomers noted the A and B components have a polarization angle of 40-50° while the polarization angle for the C and D components is 140°. They also noted the D component displays a significant fraction of polarization variability. The quasar is found to display X-ray emission from the lens images based on Chandra X-ray observations and has a supermassive black hole mass of 108.4 ± 0.2 M☉ based on a magnesium emission line width. There are also detections of both redshifted and blueshifted lines from the quasar with the quasar's half-light radius of the accretion disk estimated as (0.70 ± 0.04)RE = (6.4 ± 0.4) light-days.

References

External links SDSS J1004+4112 on SIMBAD

Illustrations

Worked examples

Example 1 — a first encounter with SDSS J1004+4112

Start with the simplest possible case. Write down what SDSS J1004+4112 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 SDSS J1004+4112 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 SDSS J1004+4112 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 SDSS J1004+4112

In research: SDSS J1004+4112 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 SDSS J1004+4112 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: SDSS J1004+4112 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Active galaxies, Astronomical objects discovered in 2003, Gravitationally lensed quasars, so understanding it makes those chapters shorter.
In everyday life: Look for SDSS J1004+4112 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 SDSS J1004+4112 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SDSS J1004+4112 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 SDSS J1004+4112 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SDSS J1004+4112 in simple terms?

SDSS J1004+4112 is a gravitationally-lensed quasar located in the constellation of Leo Minor. It has a redshift of (z) 1.73 indicating a light-travel time distance of 10 billion light-years.

Why does SDSS J1004+4112 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 SDSS J1004+4112?

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 SDSS J1004+4112.