Instruct: Given a question, retrieve passages that answer the question.
Query: What kind of telescope was used to get pictures of the black hole?
The Event Horizon Telescope (EHT) is a project to create a large telescope array consisting of a global network of radio telescopes and combining data from several very-long-baseline interferometry (VLBI) stations around the Earth. The aim is to observe the immediate environment of the supermassive black hole Sagittarius A* at the center of the Milky Way, as well as the even larger black hole in the supergiant elliptical galaxy Messier 87, with angular resolution comparable to the black hole's event horizon.[1][2][3][4][5]
General relativity predicts the smallest primordial black holes would have evaporated by now, but if there were a fourth spatial dimension – as predicted by string theory – it would affect how gravity acts on small scales and "slow down the evaporation quite substantially". This could mean there are several thousand black holes in our galaxy. To test this theory, scientists will use the Fermi Gamma-ray Space Telescope which was put in orbit by NASA on June 11, 2008. If they observe specific small interference patterns within gamma-ray bursts, it could be the first indirect evidence for primordial black holes and string theory.
The presence of an active nucleus demonstrates that a supermassive black hole is present in NGC 1275's center. The black hole is surrounded by a rotating disk of molecular gas. High-resolution observations of the rotation of this disk obtained using adaptive optics at the Gemini North telescope indicate a central mass of approximately 800 million Solar masses, including both the mass of the black hole and of the inner core of the gas disk.
The telescope will be used to study the event horizons of black holes and to test how general relativity behaves in environments with extreme gravity. 
O'Dowd studies black holes and quasars by using gravitational lensing. He uses the Hubble Space Telescope to look at distant quasars that line up with nearby galaxies. Those galaxies act like additional lenses on the telescope, allowing scientists to see much closer to the black hole than is otherwise possible.
Regarding "Black Hole Sun", Cornell stated, "It's just sort of a surreal dreamscape, a weird, play-with-the-title kind of song." He also said that "lyrically it's probably the closest to me just playing with words for words' sake, of anything I've written. I guess it worked for a lot of people who heard it, but I have no idea how you'd begin to take that one literally." In another interview he elaborated further, stating, "It's funny because hits are usually sort of congruent, sort of an identifiable lyric idea, and that song pretty much had none. The chorus lyric is kind of beautiful and easy to remember. Other than that, I sure didn't have an understanding of it after I wrote it. I was just sucked in by the music and I was painting a picture with the lyrics. There was no real idea to get across." Commenting upon how the song was misinterpreted as being positive, Cornell said, "No one seems to get this, but 'Black Hole Sun' is sad. But because the melody is really pretty, everyone thinks it's almost chipper, which is ridiculous." When asked about the line, "Times are gone for honest men", Cornell said:
Filippenko developed and runs the Katzman Automatic Imaging Telescope (KAIT), a fully robotic telescope which conducts the Lick Observatory Supernova Search (LOSS), the most successful nearby supernova search. He is also a member of the Nuker Team which uses the Hubble space telescope to examine supermassive black holes and determined the relationship between a galaxy's central black hole's mass and velocity dispersion. The Thompson-Reuters "incites" index ranked Filippenko as the most cited researcher in space science for the ten-year period between 1996 and 2006.
In 1970, Hawking postulated what became known as the second law of black hole dynamics, that the event horizon of a black hole can never get smaller. With James M. Bardeen and Brandon Carter, he proposed the four laws of black hole mechanics, drawing an analogy with thermodynamics. To Hawking's irritation, Jacob Bekenstein, a graduate student of John Wheeler, went further—and ultimately correctly—to apply thermodynamic concepts literally. In the early 1970s, Hawking's work with Carter, Werner Israel and David C. Robinson strongly supported Wheeler's no-hair theorem, one that states that no matter what the original material from which a black hole is created, it can be completely described by the properties of mass, electrical charge and rotation. His essay titled "Black Holes" won the Gravity Research Foundation Award in January 1971. Hawking's first book, "The Large Scale Structure of Space-Time," written with George Ellis, was published in 1973.
Alongside Heino Falcke and Michael Kramer, he received a
14 million euro research grant of the European Research Council for further
studies into black holes with the goal to construct a black hole camera using the Event Horizon Telescope. This would allow testing of general theory of relativity by creating an image of the black hole shadow.
It is possible, in some theories of quantum gravity, to calculate the quantum corrections to ordinary, classical black holes. Contrarily to conventional black holes, which are solutions of gravitational field equations of the general theory of relativity, quantum gravity black holes incorporate quantum gravity effects in the vicinity of the origin, where classically a curvature singularity occurs. According to the theory employed to model quantum gravity effects, there are different kinds of quantum gravity black holes, namely loop quantum black holes, non-commutative black holes, asymptotically safe black holes. In these approaches, black holes are singularity-free.
The Nuker Team was formed to use the Hubble Space Telescope, with its high-resolution imaging and spectroscopy, to investigate the central structure and dynamics of galaxies. The team used the HST to examine supermassive black holes and determined the relationship between a galaxy's central black hole's mass and velocity dispersion. The team continues to conduct research and publish papers on the supermassive black holes of galaxies and clusters. The group was initially formed by Tod R. Lauer, then a first year postdoc. At the first meeting of the group held at Princeton University in June 1985, Sandra Faber was elected the group leader.
MAXI J1659-152 is a rapidly rotating black-hole/star system, discovered by NASA's Swift space telescope on September 25, 2010. On March 19, 2013, ESA's XMM-Newton space telescope has helped to identify a star and a black hole that orbit each other at the rate of once every 2.4 hours.
Hawking realized that the event horizon of a black hole could only get bigger, not smaller. The area of the event horizon of a black hole gets bigger whenever something falls into the black hole. He also realized that when two black holes combine, the size of the new event horizon is greater than or equal to the sum of the event horizons of the two original black holes. This means that a black hole's event horizon can never get smaller.
Subsequent investigations employed adaptive optics to acquire a better estimate of the mass of the black hole.
One group made observations using the Gemini Near Infrared Integral Field Spectrometer to better determine the mass of the black hole at the center of NGC 1277. The group used similar models to that of van den Bosch, but with higher spatial resolution. After using stellar dynamics and luminosity models to estimate the mass of the black hole, they came to a mass of , similar to the estimate from the follow-up study done by Emsellem, which estimated a mass between 2–5 billion solar masses. 
More recently, a new group made observations using the larger Keck Telescope with superior spatial resolution, and calculated that a black hole with mass fits best. Moreover, this value is an order of magnitude smaller than first reported by van den Bosch, and was noted to probably be an upper limit due to the edge-on rotating disk in NGC 1277.
Black holes are difficult to find because they do not let out any light. They can be found when black holes suck in other stars. When black holes suck in other stars, the black hole lets out X-rays, which can be seen by telescopes.
Orbiting Binary Black Hole Investigation Satellite (ORBIS) is a small space telescope still in development by Japan that will study binary black holes in the X-ray region.
Stellar black holes in close binary systems are observable when matter is transferred from a companion star to the black hole. The energy release in the fall toward the compact star is so large that the matter heats up to temperatures of several hundred million degrees and radiates in X-rays (X-ray astronomy). The black hole therefore is observable in X-rays, whereas the companion star can be observed with optical telescopes. The energy release for black holes and neutron stars are of the same order of magnitude. Black holes and neutron stars are often difficult to distinguish.
The WHT is equipped with a wide range of instruments operating over the optical and near-infrared regimes. These are used by professional astronomers to conduct a wide range of astronomical research. Astronomers using the telescope discovered the first evidence for a supermassive black hole (Sgr A*) at the centre of the Milky Way, and made the first optical observation of a gamma-ray burst. The telescope has 75% clear nights, with a median seeing of 0.7".
The James Gregory Telescope is the largest working optical telescope in the UK and is still used by the School of Physics and Astronomy for research in collaborative projects such as SuperWASP and the study of super massive black holes and their impact on galaxy structure.
Two black holes of between 10 and 20 solar masses each have been discovered, initially with the Very Large Array radio telescope in New Mexico, and corroborated by the Chandra X-ray telescope, in 2012. Their detection implies that gravitational ejection of black holes from clusters is not as efficient as was previously thought, and leads to estimates of a total 5 to 100 black holes within M22. Interactions between stars and black holes could explain the unusually large core of the cluster.
What already has been observed directly in many systems are the lower non-relativistic velocities of matter orbiting further out from what are presumed to be black holes. Direct Doppler measures of water masers surrounding the nuclei of nearby galaxies have revealed a very fast Keplerian motion, only possible with a high concentration of matter in the center. Currently, the only known objects that can pack enough matter in such a small space are black holes, or things that will evolve into black holes within astrophysically short timescales. For active galaxies farther away, the width of broad spectral lines can be used to probe the gas orbiting near the event horizon. The technique of reverberation mapping uses variability of these lines to measure the mass and perhaps the spin of the black hole that powers active galaxies.
In 2009, a team of astronomers using the Swift spacecraft used the luminosity output of S5 0014+81 to measure the mass of the central black hole. To their surprise, they found out that the central black hole of S5 0014+81 is actually 10,000 times more massive than the black hole at the center of our galaxy, or equivalent to 40 billion solar masses. This makes it one of the most massive black holes ever discovered, more than six times the value of the black hole of Messier 87, which was thought to be the largest black hole for almost 60 years, and was coined to be an "ultramassive" black hole.
The Schwarzschild radius of this black hole is 118.35 billion kilometers, giving a diameter of 236.7 billion kilometers, 1,600 astronomical units, or about 40 times the radius of Pluto's orbit, and has a mass equivalent to four Large Magellanic Clouds. What is even more remarkable is that such a large black hole existed so early in the universe, at only 1.6 billion years after the Big Bang. This suggests that supermassive black holes formed very quickly.
His research interests include active galactic nuclei (particularly Seyfert galaxy, Radio galaxy and quasars) and the ways in which large galaxies and their central supermassive black holes have changed and evolved throughout cosmological time. This research has involved the use of a variety of telescopes, including the Hubble Space Telescope, the Very Large Array, MERLIN, the William Herschel Telescope, and the Very Large Telescope.
It is not yet clear whether 47 Tucanae hosts a central black hole. Hubble Space Telescope data constrain the mass of any possible black hole at the cluster's center to be less than approximately 1,500 solar masses. However, in February, 2017, astronomers announced that a black hole of some 2,200 solar masses may be located in the cluster; the researchers detected the black hole's signature from the motions and distributions of pulsars in the cluster. However, a recent analysis of an updated and more extensive timing data set on these pulsars provides no solid evidence in favor of the existence of a black hole.
The Greenland Telescope will become part of the global network of telescopes that makes up the Event Horizon Telescope that will study supermassive black holes and explore the origin of the relativistic jet in the active galaxy Messier 87.