samanthascibelli’and’john’noé’ · teaching center (ltc), dr. noé and the students working...
TRANSCRIPT
GENERAL RELATIVITY
• The base of a wine glass was held by hand up to a small LED light
• The orienta@on of the base of the wine glass was adjusted to see different lensing effects
I would like to thank Stony Brook University, The Laser Teaching Center (LTC), Dr. Noé and the students working in the LTC this spring for the resources and guidance needed to conduct this project.
Fig. 1 – Here is an interpreta@on of how massive objects, in this case earth, curve space-‐@me. The more massive an object the larger the
distor@on of this space-‐@me.
Fig. 4 – This diagram shows the difference in a convex lens versus a gravita@onal lens [4]. Fig. 4a shows a convex lens that focuses parallel light rays onto a point (a focus). Fig. 4b shows a gravita@onal lens that focuses line onto a line rather than a
point. Because a gravita@onal lens is not perfect (no focal point) the image is deformed.
Fig. 6a Fig. 6b
Table 1
• Iden@fied gravity as a geometric property of space and @me, known as space-‐@me
• Einstein predicated in 1915 that massive objects curves this space-‐@me [3]
• Einstein's theory was confirmed by observa@ons during a solar eclipse in 1919
• Many other experimental observa@ons, such as gravita@onal waves, gravita@onal redshiZ, gravita@onal @me delay and gravita@onal lensing, have further confirmed Einstein’s predic@ons
GRAVITATIONAL LENSING • Defined simply as the focusing of light from distant stars or
galaxies when the closer intervening object, or 'lens', is massive enough
• The view of the distant universe is disturbed by gravita@onal lensing; this affects physicists physical understanding of various classes of extragalac@c objects [3]
• Light always wants to follow the shortest possible path between two points, therefore if a mass is present the space is curved and the shortest distance becomes a curve [4]
• If the observer, source and deflector lie in a straight line, the original light source will appear as a ring (Einstein Ring); if any misalignment occurs mul@ple arcs will appear instead
Introduc5on
h`p://upload.wikimedia.org/wikipedia/commons/2/22/Space@me_curvature.png
Fig. 2 – Here is a geometric portrayal of gravita@onal lensing where a massive galaxy acts as a lens and produces two images of one star.
h`p://www.genetology.net/index.php/932/algemeen/
GENERAL RELATIVITY
• Gravita@onal lenses can help astronomers map the invisible dark ma`er of the universe as well as probe the internal structure of quasars, locate black holes, and detect Earth-‐mass exoplanets [4]
• Modeling gravita@onal lensing demonstrates effects of general rela@vity in a way that is comprehensible
Purpose
Fig. 3 –Diagram of the setup used in this demonstra@on.
• The base of a wine glass was held by hand up to a small LED light ~ 12 inches away (close proximity to light gives be`er lensing effect)
• Orienta@on of the base of the wine glass was adjusted to see different lensing effects (the angle determines an arc, mul@ple arcs or a ring appears)
Experimental Method
Fig. 6 – The Einstein Ring is an example of a strong lensing effect and is rarely seen in nature [3]. In Fig. 6a we can see the “Einstein Ring” when looking right down the wineglass stem through the bowl of the glass, with the red LED light sijng right in the center. Fig. 6b shows one of
the few ‘Einstein Rings’ seen in the universe; a Horseshoe Einstein Ring shows the gravity of a red galaxy has distorted the light from a much more distant blue galaxy, but here the lens alignment is so precise that
the galaxy is is a horseshoe, nearly a complete ring.
Fig. 7 – One of the more common types lensing is shown here where mul@ple arcs are produced instead of one complete ring. Fig.7a shows four mul@ple arcs, a “quad”, when the LED was shown through the base of the wine glass at an angle. Fig. 7b is an example of a galaxy group lens in the CFHTLS-‐SL2S, called SL2SJ021408-‐053532, that shows a very complex arc
structure (in light blue).
Data/Analysis
h`p://www.cqt.hawaii.edu/News/StrongLensing/PRIm.html
Fig. 7a Fig. 7b
h`p://apod.nasa.gov/apod/ap111221.html
Fig. 8 – Once again, a more common type of lensing where only two arcs are shown in a “double” system. Fig.7a shows two arcs, when the LED was shown through the base of the wine glass at a less extreme angle
than the “quad” system. Fig.7b shows an object named SDSS J120540.43+491029.3. It is one of eight similar objects found by
combining the work of the Sloan Digital Sky Survey and NASA’s Hubble Space Telescope.
Fig. 8a Fig. 8b
Fig. 4a Fig. 4b
Fig. 5 – Here is a diagram where, for an observer O to see a light ray from a distant source S, deviated by a deflector D, more than one image can be seen. Note that O, D, and S are perfectly co-‐aligned [3].
• Einstein showed that a light ray passing at a distance ξ from an object characterized by an axially symmetric mass distribu@on M(ξ ) will undergo a total deflec@on angle â(ξ ), expressed in radians:
, and we can infer from Fig. 4 that and
• You need to adopt a given mass distribu@on (a constant mass M(ξ ) = M) in order to characterize a point-‐like object (a galaxy, star cluster, etc.) • For a gravita@onal lens produces mul@ple images the surface mass density must exceed the cri@cal mass density, which depend on rela@ve distances:
² Dod, Dos, and Dds between the observer (O), the deflector (D) and the source (S) • The Einstein angular radius: propor@onal to the square root of the mass of the deflector and defined as follows if you combine the previous three equa@ons:
• The angular radius is important because it can be used to es@mate the angular separa@on between mul@ple lensed images in a system that is not in perfect
alignment
θE =4GM (≤ DodθE )Dds
c2DodDos
θDds
≅a0Dos
θ =ξDod
h`p://hubblesite.org/gallery/album/exo@c/pr2005032d/large_web
Discussion • Table 1 below shows the different Einstein radii
considering a star, a galaxy, and a cluster of galaxies located at various distances [3]
• Only stars and very compact massive galaxies and galaxy
clusters, for which Σ(<R)/Σc ≥ 1, cons@tute promising mul@ple imaging deflectors [3]
• Note that mul@ple images can s@ll be produced even when there is no axial symmetry
Fig. 8 – Above is Galaxy Cluster CL0024 + 1654 with mul@ple images of a blue background galaxy [1]
• An interes@ng result from the analysis of giant arcs in galaxy clusters is the clusters of galaxies are dominated by dark ma`er
• The typical “mass-‐to-‐light ra@os” for clusters obtained from strong lensing analysis show that there is much more mass then light; M/L ≥ 100M⊙ /L⊙ [1].
• The distribu@on of dark ma`er follows roughly the distribu@on of light in the galaxies, in par@cular the central part of the cluster
• We can use inferred mass distribu@ons to derive the corresponding refrac@ve index distribu@on
• A piece of glass with the appropriate shape ( a wine glass) can demonstrate the same lensing effect seen with galaxies and galaxy clusters
• Therefore, we see from this experiment that a wine glass can act as a probe into the mysteries of gravita@onal lensing and dark ma`er
References 1. A. Abdo, “Gravita@onal Lensing,” Department of Physics and Astronomy
Michigan State University
2. "Gravita@onal Lensing with Wineglasses," 13 Dec. 2004. Web. 13 Apr. 2014.
3. Jean Surdej et al., "Didac@cal Experiments on Gravita@onal Lensing,” Web. 13 Apr. 2014.
4. Rosa M. Ros, “Gravita@onal lenses in the classroom,” Physical Educa@on,
September 2008
I would like to thank Stony Brook University, The Laser Teaching Center (LTC), Dr. Noé and the students working in the LTC this spring for the resources and guidance needed to conduct this project.
Acknowledgements
An Op&cal Demonstra&on of Gravita&onal Lensing Samantha Scibelli and John Noé
Laser Teaching Center, Department of Physics and Astronomy Stony Brook University
Fig. 4 – This diagram shows a convex lens versus a gravita@onal lens [4]. Fig. 4a shows a convex lens that focuses parallel light rays onto a point (a focus). Fig. 4b
shows a gravita@onal lens that focuses line onto a line rather than a point. Because a gravita@onal lens is not perfect (no focal point) the image is deformed.
Fig. 1 – Here is an interpreta@on of how massive objects, in this case earth, curve space-‐@me. The more massive an object the larger the
distor@on of this space-‐@me.
Fig. 6a Fig. 6b
a(ξ ) = 4Gc2
M (ξ )ξ
Table 1