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BLACK HOLES: DETECTION METHODS AND DISCOVERIES
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Our Team
Janet Mariadoss
Kaitlyn Lane
Melanie Marszal
sHELBY PYBUS
Soleil Kelly
Welcome
This website provides information on recent black hole discoveries and detection methods. It was created as part of a final project in an astronomy course for undergraduates at Vanderbilt University (ASTR 3890). Keep scrolling to learn more!
DETECTION METHODS
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STELLAR ORBITS
STELLAR ORBITS SCIENTISTS wins nobel prize
Scientists Andrea Ghez and Reinhard Genzel lead teams that measured the orbital motions of stars around a galactic center and found that the measurements conformed to the general relativity predictions of objects orbiting a black hole. In 2020 they received the Nobel Prize in Physics for demonstrating that a supermassive black hole most likely controls stellar orbits at the center of the Milky Way Galaxy.
Black hole at the galactic center
The team was used infrared imaging to reveal images of the center of the Milky Way galaxy, a region known as Sagittarius A*. The orbits of these stars indicate that there is an extremely large, heavy object in the middle of the Milky Way that pulls on the stars. They mapped the entire orbit of the star S2 and found that its radial velocity increased as it approached Sagittarius A* and decreased as it moved away. These measurements indicated that there was a supermassive object of about 4 million solar masses in this region. Near-infrared and x-ray flares from this object supported the interpretation of the object as a black hole.
Gravitational Waves
What are gravitational waves?
Gravitational waves are the result of the acceleration of massive bodies, causing ripples in the "fabric" of space-time. The magnitude of the mass does not matter, as long as it is greater than zero. Everything with mass creates gravitational waves, but the technology that we have thus far is only able to detect the gravitational waves emitted by very large and relatively close bodies. Gravitational waves were first theorized by Albert Einstein in 1916 alongside his Theory of General Relativity; the first gravitational waves were first observed and experimentally proven to exist in September of 2015, just shy of a century after their first postulation.
LIGO Discovery and Future Implications
Since uncovering a construct so unique and groundbreaking, future implications of the experimental discovery of black holes lead to further encounters with the universe in ways that will change the way we observe and construct new physics forever. LIGO is taking steps closer to the pinnacle of physics, which is closing the gap between general relativity and quantum mechanics. They are relatively easier to observe and extrapolate their innate characteristics in that they do not interact with normal matter nearly as much as electromagnetic waves, making them more undisturbed and free to deduct conclusions from their behavior.
DIRECT IMAGING
EVENT hORIZON team
As of 2019, the Event Horizon Team managed to take the first ever image of the silhouette of a black hole surrounded by its accretion disk by improving upon an existing radio frequency astronomy technique.
Method
The biggest hurdle was distance, with their target, M87*, being 53 million light years away. The team created a network of telescopes called the Event Horizon Telescope (EHT). They used the EHT to improve upon the Very Long Baseline Interferometry (VLBI) technique, which uses an array of telescopes all focused on the same object to effectively create one huge telescope. The more spaced out the telescopes, the better the resolution, so the EHT involves telescopes from the South Pole to Spain. After overcoming gas cloud challenges, the team imaged Sgr A* as well.
X-RAY BINARIES
X-ray binaries are, as the name suggests, binary systems that emit X-rays. They consist of a compact object (black hole or neutron star) and its companion star. Here, we will focus on black hole X-ray binaries. The black hole draws material from the companion star, forming an accretion disk. This material orbits the black hole at various speeds, heating up and moving extremely fast as it nears the Schwarzschild radius. At this point, the material will emit X-ray radiation. We can detect the presence of a black hole in these systems by observing this radiation from the inner part of this accretion disk.
LMXB's and hmxb's
There are two types of X-ray binaries: Low Mass (LMXB) and High Mass (HMXB). The low or high mass refers to the mass of the companion star, not the black hole itself. For an LMXB, the companion star has a mass of less than three stellar masses, and an HMXB star has a mass of greater than 10 stellar masses. X-ray binaries are also classified by the source of the radiation: transient or persistent. LMXBs are usually transient sources because the mass transfer from the companion star to the black hole is not continuous. The system could be “bright” (emitting X-rays) for days to months and then be quiescent, or have a very low mass accretion rate, for months to decades. HMXBs are persistent sources; the mass transfer is relatively regular, and the binary system is always bright without any quiescent periods.
The discovery of active galactic nuclei has allowed astronomers to group together several different classes of galaxies, understand how a galaxy's size can be discerned by the behavior at its core. and understand which galaxies have undergone mergers in the past, and what could be coming for our own someday.
ACTIVE GALACTIC NUCLEUS
An Active Galactic Nucleus (AGN) is an extremely bright central region of a galaxy that is dominated by the light emitted by dust and gas as it falls into a black hole
Telescopes in space and on the ground detect these emissions of gas and dust as light all along the electromagnetic spectrum–from X-rays and visible light to infrared light and radio waves.
They are are active supermassive black holes that emit bright jets and winds, and shape their galaxies, whether they are nearby Seyfert galaxies or extremely distant quasars and blazars.
BIBLIOGRAPHY
https://www.jpl.nasa.gov/edu/news/2019/4/19/how-scientists-captured-the-first-image-of-a-black-hole/
https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy#:~:text=%E2%80%9CWe%20have%20images%20for%20two,extreme%20environments%20than%20ever%20before.%E2%80%9D
https://esahubble.org/wordbank/active-galactic-nucleus/
https://webbtelescope.org/contents/articles/what-are-active-galactic-nuclei
https://www.spitzer.caltech.edu/mission/active-galactic-nuclei-agn-supermassive-black-holes
https://phys.org/news/2016-11-galactic-nuclei.html
https://arxiv.org/pdf/1711.10256.pdf
https://www.nobelprize.org/prizes/physics/2020/ghez/lecture/
https://www.pbs.org/wgbh/nova/article/andrea-ghez/
https://beta.nsf.gov/news/astronomers-discover-closest-black-hole-earth
https://www.nature.com/articles/s41567-020-01096-w
https://iopscience.iop.org/article/10.1086/427175
https://www-xray.ast.cam.ac.uk/xray_introduction/Blackholebinary.html
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