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Artist’s impression of the path of the star S2 as it passes very close to the supermassive black hole at the centre of the Milky Way. Credit: ESO/M. Kornmesser

Annotated image of the path of the star S2 as it passes very close to the supermassive black hole at the center of the Milky Way. Credit: ESO/M. Kornmesser

This artist’s impression video shows the path of the star S2 as it passes very close to the supermassive black hole at the centre of the Milky Way. As it gets close to the black hole the very strong gravitational field causes the colour of the star to shift slightly to the red, an effect of Einstein’s general thery of relativity. In this graphic the colour effect, speed and size of the objects have been exaggerated for clarity. More information and download options: Credit: ESO/M. Kornmesser Category Science & Technology License Creative Commons Attribution license (reuse allowed)

This zoom video sequence starts with a broad view of the Milky Way. We then dive into the dusty central region to take a much closer look. There lurks a 4-million solar mass black hole, surrounded by a swarm of stars orbiting rapidly. We first see the stars in motion, thanks to 26 years of data from ESO's telescopes. We then see an even closer view of one of the stars, known as S2, passing very close to the black hole in May 2018. The final part shows a simulation of the motions of the stars. More information and download options: Credit: ESO/GRAVITY Collaboration Category Science & Technology License Creative Commons Attribution license (reuse allowed)

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Gravitional Lensing

Gravitional Lensing explained

Published on Jan 26, 2017 Objects with large masses such as galaxies or clusters of galaxies warp the spacetime surrounding them in such a way that they can create multiple images of background objects. This effect is called strong gravitational lensing. More information and download options: Credit: ESA/Hubble, NASA Category Science & Technology License Creative Commons Attribution license (reuse allowed)

The video above illustrates the varying light-travel times of the distant supernova
as the light traverses around the lumpy space within the galaxy cluster MACS J1149.
Credit: NASA, ESA, Ann Field and G. Bacon (STScI).

What is Gravitational Lensing?

Hubble image of a luminous red galaxy (LRG) gravitationally distorting the light from a much more distant blue galaxy, a technique known as gravitational lensing. Credit: ESA/Hubble & NASA

Published on Feb 5, 2015 Gravity's a funny thing. Not only does it tug away at you, me, planets, moons and stars, but it can even bend light itself.
And once you're bending light, well, you've got yourself a telescope. Support us More stories Follow us on Twitter: @universetoday Follow us on Tumblr: Like us on Facebook: Google+ - Instagram Team: Fraser Cain - @fcain Jason Harmer - @jasoncharmer Susie Murph - @susiemmurph Brian Koberlein - @briankoberlein Chad Weber - weber.chad@gmail.com Kevin Gill - @kevinmgill Created by: Fraser Cain and Jason Harmer Edited by: Chad Weber Music: Left Spine Down - “X-Ray”

Icarus, the farthest individual star ever seen, shown at left. Panels at right show the view in 2011, without Icarus visible, compared with the star’s brightening in 2016. Credit: NASA, ESA and Patrick Kelly/University of Minnesota

This video shows the galaxy cluster MACS J1149.5+223. Thanks to a lucky alignment between the cluster, a dense object within it and a distant star, the image of the distant star was magnified by a factor of 2000, making it visible by the NASA/ESA Hubble Space Telescope. Like the galaxy in which the star is located, the star is actually visible several times. However, the light from the second image of the star was redirected by another massive object in the cluster and only became visible when this object moved out of the line of sight. The video shows the position of the two images of the star within the cluster. More information and download options:

Examples of Gravitional Lensing

An Example of Gravitional Lensing


ALMA_StrongLensing_SDP81_NRAO from NRAO Outreach on Vimeo.

The large blue light is a lensing galaxy in the foreground, called SDP81, about 4 billion light years away.
The red arcs are the distorted image of a more distant galaxy, about 12 billion light years away.
By analyzing small distortions in the red, distant galaxy, astronomers have determined that a dwarf dark galaxy,
represented by the white dot in the lower left, is bound to SDP81.
The image is a composite from ALMA and the Hubble.
Image: Y. Hezaveh, Stanford Univ./ALMA (NRAO/ESO/NAOJ)/NASA/ESA Hubble Space Telescope

The "Canarias Einstein Ring." The green-blue ring is the source galaxy, the red one in the middle is the lens galaxy.
The lens galaxy has such strong gravity, that it distorts the light from the source galaxy into a ring.
Because the two galaxies are aligned, the source galaxy appears almost circular.
Image: This composite image is made up from several images taken with the DECam camera on the Blanco 4m telescope
at the Cerro Tololo Observatory in Chile.

Another Einstein Ring. This one is named LRG 3-757. This one was discovered by the Sloan Digital Sky Survey,
but this image was captured by Hubble’s Wide Field Camera 3. Image: NASA/Hubble/ESA

Ancient eye in the sky

July 26, 2016 Source: National Astronomical Observatory of Japan Summary: Light from a distant galaxy can be strongly bent by the gravitational influence of a foreground galaxy.
That effect is called strong gravitational lensing. Normally a single galaxy is lensed at a time.
The same foreground galaxy can – in theory – simultaneously lens multiple background galaxies.
Although extremely rare, such a lens system offers a unique opportunity to probe the fundamental
physics of galaxies and add to our understanding of cosmology. One such lens system has recently been discovered
and the discovery was made not in an astronomer’s office, but in a classroom. It has been dubbed the Eye of Horus,
and this ancient eye in the sky may help us understand the history of the universe.

Eye of Horus in pseudo color. Enlarged image to the right (field of view of 23 arcseconds x 19 arcseconds)
show two arcs/rings with different colors. The inner arc has a reddish hue, while the outer arc has a blue tint.
There are also the lensed images of the background galaxies which are originally the same galaxies as the inner and the outer arcs.
The yellow-ish object at the center is a massive galaxy at z = 0.79 (distance 7 billion light years),
which bends the light from the two background galaxies. Credit: NAOJ

The ALMA Observatory

ALMA will consist of 66 individual antennae like these when it is complete.
The facility is located in the Atacama Desert in Chile, at 5,000 meters above sea level.
Credit: ALMA (ESO / NAOJ / NRAO)

A Giant Lensed Galaxy Arc

The view of a distant galaxy (nearly 10 billion light-years away) has been warped into a nearly 90-degree arc
of light by the gravity of the galaxy cluster known as RCS2 032727-132623 (about 5 billion light-years away).
Credit: NASA, ESA, J. Rigby (NASA GSFC), K. Sharon (KICP, U Chicago), and M. Gladders and E. Wuyts (U Chicago)

'Fireworks' Images from Hubble Telescope Capture Stars Forming Just After the Big Bang
By Nola Taylor Redd, Space.com Contributor | July 8, 2017 07:53am ET

The Hubble Space Telescope captured this view of the galaxy cluster SDSS J1110+6459, which lies 6 billion light-years from Earth and contains hundreds of galaxies. Credit: T. Johnson/NASA/ESA A natural magnifying glass has sharpened images captured by NASA's Hubble Space Telescope, revealing a distant galaxy that contradicts existing theories about early star formation. By pairing Hubble with a massive galaxy cluster, scientists captured images 10 times sharper than the space telescope could snap on its own.

In this Hubble photograph of a distant galaxy cluster, a spotty blue arc stands out against a background of red galaxies. The arc consists of three separate images of a galaxy in the background called SGAS J111020.0+645950.8, which has been magnified and distorted through a process known as gravitational lensing. Credit: T. Johnson/NASA/ESA

The newly spotted galaxy lies about 11 billion light-years from the sun. Because of the connection between distance and time, that means astronomers can see it as it looked 11 billion years ago, only a few billion years after the Big Bang that kick-started the universe about 13.8 billion years ago.

Chance microlensing events enable astronomers to probe distant quasars

Artist’s rendering of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times
that of the Sun. Natural gravitational ‘microlenses’ can provide a way to probe these objects, and now a team of astronomers
have seen hints of quasar brightness changes that hint at their presence.
Image credit: ESO/M. Kornmesser.


The technique of gravitational lensing relies on the presence of a large cluster of matter between the observer and the object to magnify light coming from that object. Credit: NASA

Predicting Gravitational Lensing by Stellar Remnants

Predicting Gravitational Lensing by Stellar Remnants(PDF)

A Hubble image of the white dwarf star PM I12506+4110E (the bright object, seen in black in this negative print) and its field which includes two distant stars PM12-MLC1&2. Credit: Harding et al./NASA/HST

Hubble image showing the white dwarf star Stein 2051B and the smaller star below it appear to be close neighbors. Credit: NASA/ESA/K. Sahu (STScI)

Illustration revealing how the gravity of a white dwarf star warps space and bends the light of a distant star behind it. Credits: NASA, ESA, and A. Feild (STScI)

Animation showing the white dwarf star Stein 2051B as it passes in front of a distant background star. Credit: NASA

Artist’s impression of the binary pair made up by a white dwarf star in orbit around Sirius (a white supergiant). Credit: NASA, ESA and G. Bacon (STScI)


Gravitional Lensing caused by Galaxies

This illustration shows how gravitational lensing works. The gravity of a large galaxy cluster is so strong, it bends, brightens and distorts the light of distant galaxies behind it. The scale has been greatly exaggerated; in reality, the distant galaxy is much further away and much smaller. Credit: NASA, ESA, L. Calcada

The notable gravitational lens known as the Cosmic Horseshoe is found in Leo. Credit: NASA/ESA/Hubble

A sample of the handmade photos of gravitational lenses that the astronomers used to train their neural network. Credit: Enrico Petrillo/Rijksuniversiteit Groningen

For further reading

Spiral galaxy A1689B11 sits behind a massive cluster of galaxies that acts as a lens, producing two magnified images of the spiral galaxy in different positions in the sky. Credit: James Josephides


Composite image showing the discovery of the most distant known star using the NASA/ESA Hubble Space Telescope. Credit: NASA & ESA and P. Kelly (University of California, Berkeley)

Appearance of LS1

This video shows the galaxy cluster MACS J1149.5+223. Thanks to a lucky alignment between the cluster, a dense object within it and a distant star, the image of the distant star was magnified by a factor of 2000, making it visible by the NASA/ESA Hubble Space Telescope. Like the galaxy in which the star is located, the star is actually visible several times. However, the light from the second image of the star was redirected by another massive object in the cluster and only became visible when this object moved out of the line of sight. The video shows the position of the two images of the star within the cluster. More information and download options: Credit: ESA/Hubble, NASA.

Gravitational lensing in MACS J1149-2223

This animation shows the effect of strong gravitational lensing, which can also be seen in the galaxy MACS J1149-2223 The mass of the galaxy cluster bends and magnifies the light of more distant objects in the background, making them appear brighter and hence allows telescopes to see them; it also leads to multiple images of the same object. This way Hubble detected the most distant star know to date, called LS1. More information and download options: Credit: ESA/Hubble, L. Calçada

Hubblecast 108 Light: Hubble finds most distant star

Astronomers have used Hubble to make an incredible discovery — they have observed the most distant star ever seen. The bright blue star existed only 4.4 billion years after the Big Bang. This incredible distant star allows astronomers to learn more about the formation and evolution of stars in the early Universe. More information and download options: Subscribe to Hubblecast in iTunes! Receive future episodes on YouTube by pressing the Subscribe button above or follow us on Vimeo: Watch more Hubblecavideo.web_category.allst episodes: Credit: Directed by: Mathias Jäger Visual design and editing: Nico Bartmann Written by: Mathias Jäger Images: ESA/Hubble, NASA Videos: ESA/Hubble, L. Calçada, M. Kornmesser Animations: NASA, ESA/Hubble, M. Kornmesser, L. Calçada Music: John Stanford (johnstanfordmusic.com) Web and technical support: Mathias Andre and Raquel Yumi Shida Executive producer: Lars Lindberg Christensen

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Gravitional waves!



Detection of an unusually bright X-Ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy. Credit: NASA/CXC/Stanford/I. Zhuravleva et al.

Caption This is the LIGO signal that heralded the era of gravitational wave astronomy. Credit Caltech/MIT/LIGO Lab


Two different "chirps" of gravitational waves produced by black holes

Published on Jun 15, 2016 The best-fit models of LIGO’s gravitational-wave signals are converted into sounds.
The first sound is from modeled gravitational waves detected by LIGO on Dec. 26, 2015, when two black holes merged.
This is then compared to the first-ever gravitational waves detected by LIGO on Sept. 14, 2015, when two higher-mass black holes merged.
This sequence is repeated. The pitch of both signals is then increased, allowing them to be heard more easily,
and this sequence is also repeated. Category Education License Standard YouTube License

LIGO again detects gravitational waves Massachusetts Institute of Technology (MIT)

Published on Jun 15, 2016 For the second time, scientists have directly detected gravitational waves — ripples through the fabric of space-time,
created by extreme, cataclysmic events in the distant universe Learn more
The team has determined that the incredibly faint ripple that eventually reached Earth was produced by two black holes colliding
at half the speed of light, 1.4 billion light years away. Video produced and edited by Melanie Gonick/MIT Two Black Holes Merge into One simulation: SXS LIGO's First Observing Run timeline image: LIGO Ripples in Spacetime Pond animation: LIGO/T. Pyle Black Holes withKnown Masses image: LIGO Comparing "Chirps" from Black Holes animation: LIGO Spiral Dance of Black Holes still image: LIGO/T. Pyle Category Science & Technology License Standard YouTube License

Gravitational waves: A new type of astronomy Gravitational waves provide key to some of the universe's greatest mysteries

[Artist Impression of the Big Bang] 20 Jun 2016 at 07:02, Katyanna Quach The first time physicists announced that the Laser Interferometer Gravitational-wave Observatory (LIGO)
had detected gravitational waves, on September 14, 2015, it was breaking news. The discovery coincided with the
100-year anniversary of Einstein's theory of General Relativity, which predicted the existence of gravitational waves.
Last week's announcement that LIGO had detected a second round of gravitational waves proved that the first signal was not a fluke.
The tremendous effort from thousands of physicists, engineers and computer scientists to design, build, and maintain LIGO,
and analyse its results, have paid off. The detector is alive and working well – uncovering signals from the most violent events
happening in our universe.

Seeds of black holes could be revealed by gravitational waves detected in space Published: Sunday, June 26, 2016 - 18:32 in Astronomy & Space

Scientists led by Durham University's Institute for Computational Cosmology ran the huge cosmological simulations
that can be used to predict the rate at which gravitational waves caused by collisions between the monster black holes might be detected.
The amplitude and frequency of these waves could reveal the initial mass of the seeds from which the first black holes grew
since they were formed 13 billion years ago and provide further clues about what caused them and where they formed, the researchers said.

What Are Gravitational Waves?

Published on Jun 8, 2015 When massive objects crash into each other, there should be a release of gravitational waves. So what are these things and how can we detect them? Support us More stories at: Follow us on Twitter: @universetoday Follow us on Tumblr Like us on Facebook Google+ - Instagram - Created by: Fraser Cain and Jason Harmer Edited by: Chad Weber Music: Left Spine Down - “X-Ray” Who wants to bet against Einstein? You? You? What about you?

An artist’s impression of two merging black holes. Image: NASA/CXC/A. Hobart


In February 2016, LIGO detected gravity waves for the first time. As this artist's illustration depicts, the gravitational waves were created by merging black holes. Credit: LIGO/A. Simonnet.

LIGO’s two facilities, located in Livingston, Louisiana, and Hanford, Washington. Credit:Ligo.caltech.edu

The universe unlocked: gravitational waves detected

Published on Feb 11, 2016 Watch Monash astrophysicists and LIGO Scientific Collaborators Dr Eric Thrane and Dr Paul Lasky describe the incredible event which took place about 1.4 billion years ago, generating the first ever gravitational wave to be detected on 14 September 2015 by the Laser Interferometer Gravitational-wave Observatory (LIGO) detectors in the USA. They describe the moment of realisation that this was a real gravitational wave, the significance of the detection and how it could unlock the secrets of the universe.


Recent Gravity waves observations - on info-quest's server!

Gravitational waves are thought to cause a rippling effect on spacetime.

Published on Jun 15, 2016 Read more: The pair of black holes responsible for the first ever detected gravitational wave may have been spat out of a mosh pit at the center of a globular star cluster. Category Science & Technology License Standard YouTube License

New gravitational wave detection shows shape of ripples from black hole collision

Gravitational wave article from the Guardian


Artist's impression of merging binary black holes. Credit: LIGO/A. Simonnet.

Optical and x-ray data on two of the new black hole pairs discovered. Credit: NASA/CXC/Univ. of Victoria/S.Ellison et al./George Mason Univ./S.Satyapal et al./SDSS

Illustration of a pair of black holes. Credit: NASA/CXC/A.Hobart

Artist’s impression of binary black hole system in the process of merging. Credit: Bohn et al.

Artist’s conception of two merging black holes, similar to those detected by LIGO on January 4th, 2017. Credit: LIGO/Caltech

A Quick Look at J140737 and J122104

Astronomers have found five new supermassive black holes in the centers of galaxies. When galaxies collide and merge with each other, it can force their supermassive black holes close together. While models predict this would happen, it has been very difficult to find these giant black hole pairs until now. The combination of data from Chandra, WISE, and the Large Binocular Telescope led to this bumper crop of black holes. This discovery could lead to a better understanding of how giant black holes grow.


Artist's illustration of two merging neutron stars. The narrow beams represent the gamma-ray burst 
while the rippling spacetime grid indicates the isotropic gravitational waves that characterize the merger.
 Swirling clouds of material ejected from the merging stars are a possible source of the light that was seen at lower energies.
 Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet

Observations of the kilonova. 
Credit: P.K. Blanchard/ E. Berger/ Pan-STARRS/DECam.

This animation shows how LIGO, Virgo, and space- and ground-based telescopes zoomed 
in on the location of gravitational waves detected August 17, 2017 by LIGO and Virgo.
 By combining data from the Fermi and Integral space missions with data from LIGO and Virgo, 
 scientists were able to confine the source of the waves to a 30-square-degree sky patch.
 Visible-light telescopes searched a large number of galaxies in that region, 
 ultimately revealing NGC 4993 to be the source of gravitational waves.

:More information and download options


The kilonova became red and faded by a factor of over 20 in just a few days. 
This rapid change was captured by Las Cumbres Observatory telescopes as night time moved around the globe.
 Credit: Sarah Wilkinson / LCO.


On 17 August 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO)
 and the Virgo Interferometer both detected gravitational waves from the collision 
 between two neutron stars. Within 12 hours observatories had identified the source 
 of the event within the lenticular galaxy NGC 4993, shown in this image gathered with the NASA/ESA Hubble Space Telescope.
 The associated stellar flare, a kilonova, is clearly visible in the Hubble observations. 
 This is the first time the optical counterpart of a gravitational wave event was observed.
 Hubble observed the kilonova gradually fading over the course of six days, as shown in these observations
 taken in between 22 and 28 August (insets).
 Credit: NASA and ESA. Acknowledgment: A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), and A. Fruchter and O. Fox (STScI).

This is the first optical image ever to show an event initially detected as a Gravitational Wave (GW), 
designated GW170817, shown left. Afterglow, designated as SSS17a, is left over from the explosion of two neutron stars
 that collided in galaxy NGC 4993 (shown centre). Only 10.9 hours after triggering the largest astronomical search in history,
 GW170817’s afterglow was discovered by the Swope 1-m telescope at the Las Campanas Observatory, in Chile.
 Four days later, image on right shows afterglow dimming in brightness and changing from blue to red.
 CREDIT: Las Campanas Observatory, Carnegie Institution of Washington (Swope + Magellan)

ANIMATION (you may have to click image for animation in some browsers): This time-lapse image of the afterglow of GW170817 
shows it continuing to increase in radio wavelength brightness over the first month, and was provided by
 the National Radio Astronomy Observatory Very Large Array radio telescope.

Change in brightness of GW170817’s afterglow over time since explosion (merger),
 is shown in these light-curves. Brightness in 14 different optical wavelengths is shown,
 including invisible ultraviolet, and visible blue, green, and yellow, 
 and invisible infrared wavelengths in orange and red. Afterglow fades quickly in all wavelengths,
 except infrared. In infrared, afterglow continues to brighten until ~3 days after explosion, before beginning to fade. 
 CREDIT: Las Campanas Observatory, Carnegie Institution of Washington (Swope + Magellan)

Afterglow faded from optical observations over days to weeks. Here, however, as observed
 at radio frequencies by the Very Large Array radio telescope, the electromagnetic counterpart to GW170817
 is seen brightening over the first month since explosion. 
 CREDIT: Courtesy of Gregg Hallinan, California Institute of Technology, and the National Radio Astronomy Observatory Very Large Array radio telescope

Science vs Cinema host Dr. Andy Howell explains the discovery of a never-before-seen astronomical phenomenon: 
a KILONOVA, the merger of two neutron stars detected via gravitational waves, which was observed by Las Cumbres Observatory.

New Gravitational Wave Discovery (Press Conference and Online Q&A Session)

0:00:15 Gravitational Wave Panel 0:38:20 Press Conference Q&A (Gravitational Wave Panel) 0:51:35 YouTube Q&A Session (Part 1) 1:15:20 EM Follow-up Panel 1:59:55 Press Conference Q&A (EM Follow-up Panel) 2:24:40 YouTube Q&A Session (Part 2) New details and discoveries made in the ongoing search for gravitational waves! Two panels with Q&A from the press conference hosted by the National Press Club in Washington, D.C. In between and after the two panels we did answer questions live from the YouTube chat from our YouTube Studio . It was the first time we were trying something like that ... and it did not go without some fun technical hick-ups. ^^ Find details about the new detection at Make sure to subscribe to the official LIGO Virgo YouTube Channel

Superfast Jet of Material Blasted Out From Last Year’s Neutron Star Merger

Thanks to the following 3 observatories

In August of 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected waves that were believed to be caused by a neutron star merger. This “kilonova” event, known as GW170817, was the first astronomical event to be detected in both gravitational and electromagnetic waves – including visible light, gamma rays, X-rays, and radio waves.

Artist’s illustration of two merging neutron stars. The narrow beams represent the gamma-ray burst while the rippling spacetime grid indicates gravitational waves. Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet

Artist’s impression of the kilova event, with images indicating how the resulting object brightened over time. Credit: NASA/CXC/Trinity University/D. Pooley et al. Illustration: NASA/CXC/M.Weiss

Illustration of the resulting black hole caused by GW170817. Credit: NASA/CXC/M.Weiss


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Gravity Waves

From einstein-online.info

See also my section on the Lisa Gravitional Observatory pathfinder:


What do gravitational waves do?

But what do gravitational waves do? For that, let us look at a simplified, entirely hypothetical situation.
(The following are variations on images and animations originally published here on Einstein Online.)
Consider particles drifting in space, far from any sources of gravity. Imagine that the particles (red)
are arranged in a circle around a center (marked in black): If a simple gravitational wave were to pass through this image, coming directly at the reader,
distances between these particles would change rhythmically as follows:

Note the distinctive pattern: When the circle is stretched in the vertical direction,
it is compressed in the horizontal direction, and vice versa. That’s typical for gravitational waves (“quadrupole distortion”). It’s important to keep in mind that this animation, and the ones that will follow,
exaggerate the gravitational wave’s effect quite considerably.

Gravitational waves moving through space

Just remember that neither the lines nor the whitish surface is physical. On the contrary,
if we want the particles to be maximally susceptible to the effect of the gravitational wave,
we should make sure they are truly floating freely, and certainly they shouldn’t be linked in any way!

As you can see, the wave is propagating through space. For instance, the point where the vertical distances
within the circle of particles is maximal is moving towards the observer. The wave nature can be seen even more clearly
if we look at this cylinder directly from the side:

As you can see, the wave is propagating through space. For instance, the point where the vertical distances
within the circle of particles is maximal is moving towards the observer.
The wave nature can be seen even more clearly if we look at this cylinder directly from the side:

Objects in orbit

The simplest situation that produces gravitational waves in the cosmos is almost ubiquitous:
two or more objects orbiting around each other under their own gravity.
The waves they generate are reminiscent to a very slow mixer in the middle of a pool of water:
This is not something you would see, of course. The wave that is pictured here represents the strength
of the minute changes in distance that would be caused by the gravitational wave, just as we’ve seen in
Gravitational waves and how they distort space.
The animation is courtesy of Sascha Husa of the Universitat de les Illes Balears.

Gravitational Waves Discovered: A New Window on the Universe

illustration of Markarian 231, a binary black hole 1.3 billion light years from Earth.
Their collision generated the first gravitational waves we've ever detected.
Image: NASA

Published on Oct 20, 2015 What happens when two black holes collide? This extreme scenario likely occurs in the centers
of some merging galaxies and multiple star systems. The featured video shows a computer animation of the final
stages of such a merger, while highlighting the gravitational lensing effects that would appear on a background starfield.
The black regions indicate the event horizons of the dynamic duo, while a surrounding ring of shifting background stars
indicates the position of their combined Einstein ring. All background stars not only have images visible outside of
this Einstein ring, but also have one or more companion images visible on the inside. Eventually the two black holes coalesce.
The end stages of such a merger may provide a strong and predictable blast of gravitational radiation, a much sought after form of
radiation different than light that has never yet been directly observed. Virtues Inherited, Vices Passed On by Chris Zabriskie is licensed under a Creative Commons Attribution license (https://creativecommons.org/licenses/...) Source: http://chriszabriskie.com/reappear/ Artist: http://chriszabriskie.com/ When Black Holes Collide Video Credit & Copyright: Simulating Extreme Spacetimes Collaboration http://www.black-holes.org/about-us/p... http://www.black-holes.org/ Category Science & Technology License Creative Commons Attribution license (reuse allowed) Remix this video

Infographic: What made Gravitional waves?

Nature News, March 23, 2016, doi:10.1038/531428a Source: Ref. [1]/Nik Spencer/Nature But the Event also marks the start of a long-promised era of gravitational-wave astronomy. Detailed analysis of the signal
has already yielded insights into the nature of the black holes that merged, and how they formed.
With more events such as these—the LIGO team is analysing several other candidate events captured during the detectors'
four-month run, which ended in January—researchers will be able to classify and understand the origins of black holes,
just as they are doing with stars.

How do we observe Gravitational Waves?

The Laser Interferometer Gravitational-Wave Observatory (LIGO)facility in Livingston, Louisiana.
The other facility is located in Hanford, Washington.
Image: LIGO

Interferometric gravitational wave detectors: the set-up

Light is sent into the detector from the (laser) light source LS to the beamsplitter B which,
true to its name, sends half of the light on to the mirror M1 and lets the other half through to the mirror M2.
At M1 and M2, respectively, the light is reflected back to the beam splitter. There, the light arriving from M1 (or M2)
is split again, with half going towards the light detector LD, the other half back in the direction of the light source LS.
We will ignore the latter half and pretend, for the sake of our simplified explanation, that all the light reaching B
from M1 or M2 goes on to the light detector LD.

Interferometric gravitational wave detectors: Operation

Light starts at the light source to the left. Light that has left the source together, travels together
(so green and red pulses are side by side) until the beam splitter. The beam splitter then sends the green pulses on
their upward journey and lets the red pulses pass on their way towards the mirror on the right.
All the particles that arrive back at the beamsplitter after reflection at M1 or M2. At the beamsplitter,
they are directed towards the light detector at the bottom. In this setup, the horizontal arm is slightly longer than the vertical arm. Red particles have to cover some extra distance.
That is why they arrive at the detector a bit later, and we get an alternating rhythm: green, red, green, red, with equal distances in between.
This will become important later on.

Here is a diagram, a kind of registration strip, which shows the arrival times for red and green pulses at the light detector
(time is measured in “animation frames”): The pattern is clear: red and green pulses arrive evenly spaced, one after the other.

Interferometric gravitational wave detectors: Detection

Next, let’s switch on our standard gravitational wave (exaggerated, passing through the screen towards you, and so on). Here is the result: We have trained our camera on the beamsplitter (so in our image, the beamsplitter doesn’t move). We ignore any slight changes in distance
between beamsplitter and light source/light detector. Instead, we focus on the mirrors M1 and M2, which change their distance from the beamsplitter
just as we would expect from the earlier animations.

Look at the way the pulses arrive at our light detector: sometimes red and green are almost evenly spaced,
sometimes they close together. That is caused by the gravitational wave. Without the wave, we had strict regularity.

Epic Gravitational Wave Detection: How Scientists Did It

To spot gravitational waves directly for the first time ever, scientists had to measure a
distance change 1,000 times smaller than the width of a proton.

This Is What Gravitational Waves Sound Like

Published on Feb 11, 2016 The National Science Foundation (NSF) has announced the detection of gravitational waves by the
Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of ground-based observatories in Hanford, Washington,
and Livingston, Louisiana. Albert Einstein predicted the existence of gravitational waves in his general theory of relativity a century ago,
and scientists have been attempting to detect them for 50 years. Einstein pictured these waves as ripples in the fabric of space-time
produced by massive, accelerating bodies, such as black holes orbiting each other. Scientists are interested in observing and
characterizing these waves to learn more about the sources producing them and about gravity itself. The LIGO detections represent a much-awaited first step toward opening a whole new branch of astrophysics.
Nearly everything we know about the universe comes from detecting and analyzing light in all its forms across the electromagnetic spectrum
– radio, infrared, visible, ultraviolet, X-rays and gamma rays. The study of gravitational waves opens a new window on the universe,
one that scientists expect will provide key information that will complement what we can learn through electromagnetic radiation.
Just as in other areas of astronomy, astronomers need both ground-based and space-based observatories to take full advantage of this new window.
LIGO is sensitive to gravitational waves within the range of 10 to 1,000 cycles per second (10 to 1,000 Hz).
A space-based system would be able to detect waves at much lower frequencies, from 0.0001 to 0.1 Hz, and detect different types of sources
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Published on Feb 11, 2016 After a decades-long quest, The MIT-Caltech collaboration LIGO Laboratories has detected gravitational waves,
opening a new era in our exploration of the universe. Read more: http://news.mit.edu/2016/ligo-first-d... Produced by MIT Video Productions and MIT News Office Producer/Editor: Bill Lattanzi Footage courtesy of: Hans Peter Bischof; California Institute of Technology; Jet Propulsion Laboratory; LIGO,
A Passion for Understanding, by Kai Staats; MIT; National Science Foundation; Roger Smith; Virginia Trimble, widow of
Joseph Weber; Wikipedia Commons Category Science & Technology License Standard YouTube License


An artist's impression of a Gamma Ray Burst. Credit: Stanford.edu

Published on Feb 11, 2016 ESA is thrilled to learn that gravitational waves have been detected, and is looking forward to starting
its mission to test technologies that could extend the study of these exotic waves to space. Gravitational waves
are elusive no more: an exciting breakthrough that has been 100 years in the making. In November 1915, Albert Einstein
presented his general theory of relativity, introducing a dramatic change of perspective in the physical understanding
of one of the four fundamental interactions of nature: gravity. This theory describes gravity as the way matter interacts with the flexible
‘spacetime’ it is embedded in. Massive bodies deform spacetime, changing its curvature as they move. When accelerated,
massive bodies produce tiny fluctuations in the fabric of spacetime – gravitational waves – which were first predicted
in a further study published by Einstein in 1918. These minuscule cosmic perturbations have finally been revealed, after almost
a century of theoretical investigations and experimental searches. The discovery was announced today by scientists from the
Laser Interferometer Gravitational-Wave Observatory (LIGO) collaboration. LIGO comprises two gravitational wave detectors in
Livingston, Louisiana and Hanford, Washington, USA, and involves over a thousand scientists from across the world.
The experiment uses laser beams to monitor two perpendicular arms, each extending 4 km, to look for tiny changes in their
length that might be caused by passing gravitational waves. Recently upgraded to become Advanced LIGO, the experiment
obtained this historic result during the first observation run in the new configuration, which collected data between
September 2015 and January 2016. The recorded signal is very strong, and it appears to come from a pair of coalescing
black holes about 1.3 billion light-years away. The two monstrous bodies, with masses equivalent to 36 and 29 times the mass of the Sun,
respectively, merged to form a single, even more gigantic black hole of 62 solar masses, releasing the remaining 3 solar masses
in gravitational waves. Like light, gravitational waves also span a broad spectrum of frequencies, and different astronomical objects
are expected to emit these waves all across the spectrum. Ground-based experiments like LIGO are sensitive to high-frequency waves,
like those coming from coalescing pairs of black holes or neutron stars, with frequencies of 10–1000 Hz.
To detect gravitational waves with lower frequencies, such as those from the merging of supermassive black holes
at the centre of massive galaxies, scientists need to investigate changes in length of much longer arms –
about one million kilometres. This can only be achieved in space, using laser beams to monitor the distance between
three freely falling masses separated by much larger distances than can be achieved on Earth. Category Science & Technology License Standard YouTube License

Gravitational Waves 101: How to Hear the Universe The Good Stuff

Published on Jun 14, 2016 In 2015 scientists working at the Laser Interferometer Gravitational-Wave observatory, or LIGO,
detected gravitational waves for the first time. But how did they do it? What is a gravitational wave?
And why is confirming something that Albert Einstein predicted a hundred years ago one of the greatest
scientific achievements of the past century? HUGE Thanks to the LIGO team and the National Science Foundation for funding amazing projects like LIGO The University of Chicago LIGO group is comprised of Daniel Holz, Ben Farr, Hsin-Yu Chen, and Zoheyr Doctor, and they all contributed to the results described in this video. ►Subscribe: : ►Let us know what you think of our show! The Good stuff patreon ►Follow us on Twitter: ►Follow us on instagram: goodstuffshow ►Like us on facebook Digital street team: Sign up for our mailing list: The Good Stuff is a proud member of the PBS Digital Studios family

Cosmic Clocks Keep Time in the Search for Gravitational Waves
By Calla Cofield, Space.com Staff Writer | August 1, 2016 07:36am ET

The Arecibo Observatory is used by Nanograv, a collaboration using pulsars to search for gravitational waves. Credit: Arecibo Observatory/NSF

This illustration shows how a gravitational wave can interrupt the arrival time of a pulsar's light.
The areas of high and low pressure in the wave (shown in red and blue) change the space between the Earth and the pulsar.
Credit: B. Saxton (NRAO/AUI/NSF)

This artist's illustration shows how a Pulsar Timing Array uses multiple pulsars
to detect the passing of a gravitational wave. An interruption in the arrival time of the
pulsar's light flashes could be caused by multiple variables; once scientists have accounted for all those variables,
they can look for changes caused by a gravitational wave. The arrival time should change for multiple pulsars in the same region of the sky. Credit: David Champion

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Black hole at the center of our Galaxy

Swirling around the dark mass beneath them, this moving animation
shows how scientists used the stars to identify an enormous black hole at the centre of our galaxy.
Researchers monitored the orbit of the stars circling the centre of the Milky Way
to map out the size of the phenomenon, which is four million times heavier than the sun.
Over 16 years they tracked 28 stars and determined the black hole, known as Sagittarius A*,
was influencing their movements.

Read more:

Tracking Stars Orbiting the Milky Way's Central Black Hole

Sequences showing the real images acquired with the VLT, and 2D and 3D animations illustrating the motion of the stars around the black hole at the centre of the Galaxy. 00:10 - zoom and pan the colour image obtained with the VLT; 00:56- zoom in real images of the galaxies, starting from a wide angle view, all the way to the sequence of real images showing the stars orbiting the black hole at the centre; 01:30- fade from the real data to a 3D animation of the stars around the black hole; 02:00- 3D animation showing the S2 star orbiting the black hole 02:35- 2D animation with all the measured stars, reproducing the real observations.

Credit: ESO/ S. Gillessen, R. Genzel In a 16-year long study, using several of ESO's flagship telescopes, a team of German astronomers has produced
the most detailed view ever of the surroundings of the monster lurking at our Galaxy's heart —
a supermassive black hole. The research has unravelled the hidden secrets of this tumultuous region
by mapping the orbits of almost 30 stars, a five-fold increase over previous studies.
One of the stars has now completed a full orbit around the black hole.

Credit: ESO/ S. Gillessen, R. Genzel source:

Enormous Structures Might be Hiding in the Center of our Galaxy

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