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Astrophysics science fair project:
Morphological Identification of Wide-Separation Gravitationally Lensed Quasars




Science Fair Project Information
Title: Morphological Identification of Wide-Separation Gravitationally Lensed Quasars
Subject: Astrophysics
Subcategory: Quasars
Grade level: High School - Grades 10-12
Academic Level: Advanced
Project Type: Experimental
Cost: Medium
Awards: Google Science Fair Finalist
Affiliation: Google Science Fair
Year: 2014
Materials and Techniques: Sloan Digital Sky Survey (SDSS), Structured Query Language (SQL)
Concepts: Gravitational lens
Description: A novel method was developed to identify gravitationally lensed quasars from the Sloan Digital Sky Survey (SDSS). Understanding gravitational lensing can help decipher the properties of dark matter and dark energy. It is hypothesized that if multiple objects in an SDSS image meet both photometric and spectral criteria, then these objects are gravitationally lensed quasar candidates.
Link: https://www.astroleague.org/files/awards/Pranav_Sivakumar_project.pdf
Short Background

Gravitational lens


In the formation known as Einstein's Cross, four images of the same distant quasar appear around a foreground galaxy due to strong gravitational lensing.

A gravitational lens refers to a distribution of matter (such as a cluster of galaxies) between a distant source and an observer, that is capable of bending the light from the source, as it travels towards the observer. This effect is known as gravitational lensing and is one of the predictions of Albert Einstein's general theory of relativity.

Quasars (/ˈkweɪzɑr/) or quasi-stellar radio sources are the most energetic and distant members of a class of objects called active galactic nuclei (AGN). Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that appeared to be similar to stars, rather than extended sources similar to galaxies. Their spectra contain very broad emission lines, unlike any known from stars, hence the name "quasi-stellar." Their luminosity can be 100 times greater than that of the Milky Way. Most quasars were formed approximately 12 billion years ago caused by collisions of galaxies and their central black holes merging to form a supermassive black hole.

While the nature of these objects was controversial until the early 1980s, there is now a scientific consensus that a quasar is a compact region in the center of a massive galaxy surrounding a central supermassive black hole. Its size is 10–10,000 times the Schwarzschild radius of the black hole. The energy emitted by a quasar derives from mass falling onto the accretion disc around the black hole.

Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers can only detect bright objects that emit much light (stars) or large objects that block background light (clouds of gas and dust). These objects make up only a tiny portion of the mass of a galaxy. Microlensing allows the study of objects that emit little or no light.

The Twin Quasar (Twin QSO or Double Quasar or Old Faithful, also known as SBS 0957+561, TXS 0957+561, Q0957+561 or QSO 0957+561 A/B), was discovered in 1979 and was the first identified gravitationally lensed object. It is a quasar that appears as two images, a result from gravitational lensing caused by the galaxy YGKOW G1 that is located in the line of sight between Earth and the quasar.

See also:
https://en.wikipedia.org/wiki/Gravitational_lens
https://en.wikipedia.org/wiki/Quasar
https://en.wikipedia.org/wiki/Gravitational_microlensing
https://en.wikipedia.org/wiki/Twin_Quasar

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)

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