Editing Gravitational lens (section)

==Search for gravitational lenses==
<!---[[File:Heic1401a-Abell2744-20140107.jpg|thumb|[[Abell 2744]] [[galaxy cluster]] - [[Hubble Space Telescope#Frontier Fields program|Hubble Frontier Fields view]] (7 January 2014).<ref name="NASA-20140107">{{cite news |last1=Clavin |first1=Whitney |last2=Jenkins |first2=Ann |last3=Villard |first3=Ray |title=NASA's Hubble and Spitzer Team up to Probe Faraway Galaxies |url=http://www.jpl.nasa.gov/news/news.php?release=2014-007 |date=7 January 2014 |work=[[NASA]] |access-date=8 January 2014 }}</ref>]]--->
[[File:MACS J1206.jpg|thumb|This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster [[MACS J1206]].]]

Most of the gravitational lenses in the past have been discovered accidentally. A search for gravitational lenses in the northern hemisphere (Cosmic Lens All Sky Survey, CLASS), done in radio frequencies using the Very Large Array (VLA) in New Mexico, led to the discovery of 22 new lensing systems, a major milestone. This has opened a whole new avenue for research ranging from finding very distant objects to finding values for cosmological parameters so we can understand the universe better.

A similar search in the southern hemisphere would be a very good step towards complementing the northern hemisphere search as well as obtaining other objectives for study. If such a search is done using well-calibrated and well-parameterized instruments and data, a result similar to the northern survey can be expected. The use of the Australia Telescope 20&nbsp;GHz (AT20G) Survey data collected using the Australia Telescope Compact Array (ATCA) stands to be such a collection of data. As the data were collected using the same instrument maintaining a very stringent quality of data we should expect to obtain good results from the search. The AT20G survey is a blind survey at 20&nbsp;GHz frequency in the radio domain of the electromagnetic spectrum. Due to the high frequency used, the chances of finding gravitational lenses increases as the relative number of compact core objects (e.g. quasars) are higher (Sadler et al. 2006). This is important as the lensing is easier to detect and identify in simple objects compared to objects with complexity in them. This search involves the use of interferometric methods to identify candidates and follow them up at higher resolution to identify them. Full detail of the project is currently under works for publication.

[[File:Helping Hubble SDSS J0915+3826.tif|thumb|left|Galaxy cluster SDSS J0915+3826 helps astronomers to study star formation in galaxies.<ref>{{cite web |title=Helping Hubble |url=https://www.spacetelescope.org/images/potw1844a/ |website=www.spacetelescope.org |access-date=29 October 2018}}</ref>]]

Microlensing techniques have been used to search for planets outside the [[Solar System]].  A statistical analysis of specific cases of observed microlensing over the time period of 2002 to 2007 found that most stars in the [[Milky Way]] galaxy hosted at least one orbiting planet within 0.5 to 10 AU.<ref>{{Cite journal|last1=Cassan|first1=A.|last2=Kubas|first2=D.|last3=Beaulieu|first3=J.-P.|last4=Dominik|first4=M.|last5=Horne|first5=K.|last6=Greenhill|first6=J.|last7=Wambsganss|first7=J.|last8=Menzies|first8=J.|last9=Williams|first9=A.|title=One or more bound planets per Milky Way star from microlensing observations|journal=Nature|volume=481|issue=7380|pages=167–169|doi=10.1038/nature10684|arxiv = 1202.0903 |bibcode = 2012Natur.481..167C |year=2012|pmid=22237108|s2cid=2614136}}</ref>

In 2009, weak gravitational lensing was used to extend the mass-X-ray-luminosity relation to older and smaller structures than was previously possible to improve measurements of distant galaxies.<ref>{{cite web| url = https://www.sciencedaily.com/releases/2010/01/100119172846.htm| title = Cosmology: Weak gravitational lensing improves measurements of distant galaxies |date=January 21, 2010 |work=ScienceDaily |author=DOE/Lawrence Berkeley National Laboratory}}</ref>

{{As of|2013}} the most distant gravitational lens galaxy, [[J1000+0221]], had been found using [[NASA]]'s [[Hubble Space Telescope]].<ref>{{cite web|last=Sci-News.com|title=Most Distant Gravitational Lens Discovered|url=http://www.sci-news.com/astronomy/science-gravitational-lens-01478.html|website=Sci-News.com|access-date=22 October 2013|date=21 Oct 2013 |archive-url=https://web.archive.org/web/20131023092313/http://www.sci-news.com/astronomy/science-gravitational-lens-01478.html|archive-date=23 October 2013|url-status=dead}}</ref><ref>{{cite journal|last=van der Wel|first=A.|display-authors=etal|title=Discovery of a Quadruple Lens in CANDELS with a Record Lens Redshift|journal=Astrophysical Journal Letters|date=2013|arxiv=1309.2826|bibcode = 2013ApJ...777L..17V |doi = 10.1088/2041-8205/777/1/L17|volume=777|issue=1|pages=L17|s2cid=55728208}}</ref>  While it remains the most distant quad-image lensing galaxy known, an even more distant two-image lensing galaxy was subsequently discovered by an international team of astronomers using a combination of [[Hubble Space Telescope]] and [[Keck telescope]] imaging and spectroscopy.  The discovery and analysis of the [[IRC 0218 lens]] was published in the ''[[Astrophysical Journal Letters]]'' on June 23, 2014.<ref>{{cite journal|last=Wong|first=K.|display-authors=etal|title=Discovery of a Strong Lensing Galaxy Embedded in a Cluster at z = 1.62|journal=Astrophysical Journal Letters|date=2014|volume=789|issue=2|pages=L31|doi=10.1088/2041-8205/789/2/L31|bibcode=2014ApJ...789L..31W|arxiv = 1405.3661 |s2cid=56376674}}</ref>

Research published September 30, 2013 in the online edition of ''[[Physical Review Letters]]'', led by [[McGill University]] in [[Montreal]], [[Québec]], Canada, has discovered the [[B-modes]], that are formed due to gravitational lensing effect, using [[National Science Foundation]]'s [[South Pole Telescope]] and with help from the Herschel space observatory. This discovery would open the possibilities of testing the theories of how our universe originated.<ref>{{cite journal|last=NASA/Jet Propulsion Laboratory|date=October 22, 2013|title=Long-sought pattern of ancient light detected|journal=ScienceDaily|access-date=October 23, 2013|url=https://www.sciencedaily.com/releases/2013/10/131022101009.htm}}</ref><ref>{{cite journal|author=Hanson, D. <!---|authors=D. Hanson, S. Hoover, A. Crites, P. A. R. Ade, K. A. Aird, J. E. Austermann, J. A. Beall, A. N. Bender, B. A. Benson, L. E. Bleem, J. J. Bock, J. E. Carlstrom, C. L. Chang, H. C. Chiang, H-M. Cho, A. Conley, T. M. Crawford, T. de Haan, M. A. Dobbs, W. Everett, J. Gallicchio, J. Gao, E. M. George, N. W. Halverson, N. Harrington, J. W. Henning, G. C. Hilton, G. P. Holder, W. L. Holzapfel, J. D. Hrubes, N. Huang, J. Hubmayr, K. D. Irwin, R. Keisler, L. Knox, A. T. Lee, E. Leitch, D. Li, C. Liang, D. Luong-Van, G. Marsden, J. J. McMahon, J. Mehl, S. S. Meyer, L. Mocanu, T. E. Montroy, T. Natoli, J. P. Nibarger, V. Novosad, S. Padin, C. Pryke, C. L. Reichardt, J. E. Ruhl, B. R. Saliwanchik, J. T. Sayre, K. K. Schaffer, B. Schulz, G. Smecher, A. A. Stark, K. T. Story, C. Tucker, K. Vanderlinde, J. D. Vieira, M. P. Viero, G. Wang, V. Yefremenko, O. Zahn, M. Zemcov--->
|title=Detection of B-Mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope|journal=Physical Review Letters|date=Sep 30, 2013|volume=111|issue=14|pages=141301|series=14|doi=10.1103/PhysRevLett.111.141301|pmid=24138230|arxiv = 1307.5830 |bibcode = 2013PhRvL.111n1301H |s2cid=9437637|display-authors=etal}}</ref>
{{wide image|14-283-Abell2744-DistantGalaxies-20141016.jpg|800px|align-cap=center|[[Abell 2744]] [[galaxy cluster]] - extremely distant [[galaxies]] revealed by [[gravitational lensing]] (16 October 2014).<ref name="NASA-20140107">{{cite news |last1=Clavin |first1=Whitney |last2=Jenkins |first2=Ann |last3=Villard |first3=Ray |title=NASA's Hubble and Spitzer Team up to Probe Faraway Galaxies |url=http://www.jpl.nasa.gov/news/news.php?release=2014-007 |date=7 January 2014 |work=[[NASA]] |access-date=8 January 2014 |archive-date=9 July 2018 |archive-url=https://web.archive.org/web/20180709164545/https://www.jpl.nasa.gov/news/news.php?release=2014-007 |url-status=dead }}</ref><ref name="NASA-20141016">{{cite web |last1=Chou |first1=Felecia |last2=Weaver |first2=Donna |title=RELEASE 14-283 - NASA's Hubble Finds Extremely Distant Galaxy through Cosmic Magnifying Glass |url=http://www.nasa.gov/press/2014/october/nasa-s-hubble-finds-extremely-distant-galaxy-through-cosmic-magnifying-glass/ |date=16 October 2014 |work=[[NASA]] |access-date=17 October 2014 }}</ref>}}