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- 2022 - Blackholes how to measure their mass? The more distant galaxies are more challenging. New techniques must be used to measure radius and rotation because they are so far away. A breakthrough was the finding of two blackholes orbiting each other.
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- Monster blackholes hide in the centers of most galaxies. A new technique is helping astronomers measure the mass of some of the very largest blackholes in the far reaches of the universe. These blackholes lie in the centers of these very faint, distant galaxies. This new approach could improve astronomer’s understanding of how these blackholes form and evolve, and how they influence galaxy evolution.
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- Astronomers now theorize that at the heart of nearly every large galaxy there is a supermassive blackhole. These monsters can be millions or billions solar mass. They do not radiate or reflect light. They can not be seen directly. But, as the gravity of the blackhole draws in dust and gas from the surrounding galaxy, it creates a swirling disk of material that falls into the blackhole.
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- That in falling material heats up and begins to radiate light, making the blackhole indirectly visible. The light can become so bright as to outshine the entire galaxy. These brightest galaxies are called “active galactic nuclei, AGNs” or , the brightest of them all are called “quasars”. Quasars seen all away across the universe indicate the presence of supermassive blackholes.
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- Blackholes have three measurable properties: mass , spin , and charge. To calculate mass we need to observe the gas or stars moving around the galactic center. By defining the orbit and speed you can calculate mass. However, these most distant galaxies can not resolve stars or clouds around the center blackhole.
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- Astronomers use a technique called “reverberation mapping” to calculate mass.
They compare the brightness of the radiating gas in the outer region of the galaxy with that found at the inner region of the galaxy
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- The gas at the inner region affects the fast moving gas farther out. However, light takes time to travel outward , or to reverberate, causing a delay between the changes seen in the inner region and the effect it has on the outer region. Measuring the delay reveals how far away the outer disk of gas is from the center of the blackhole. Couple this with the rotation rate and you can calculate the mass.
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- This observation and calculation takes many months to do. Only 60 blackholes have been measured over the past 20 years of observation. Reverberation time delay rates have been measured for 44 quasars calculating blackhole masses from 5 million to 1.7 billion Solar Mass.
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- The more distant the quasar the further back in time. Astronomers are writing the history of the birth of the universe with these observations. To date they have studied 850 quasars over multiple years. They continue to collect data and to calculate masses of these distant blackholes.
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- Good, accurate data and calculations require observations over multiple years.
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- For the first time, astronomers a have found a pair of blackholes orbiting each other. Much remains uncertain how these giants grow and how they influence the universe around them. The gravitational effects were used to calculate a 15 billion Solar Mass for the two blackholes. One might be 2 ,or even 4, times bigger than the other. They could be a distance of only 24 light years apart.
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- Astronomers believe these two blackholes were created from dozens of galaxies merging together. Possibly these two might even merge into a single giant blackhole.
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- Astronomers measured the orbital rate of just one micro-arc second per year. If that arc was measured for a planet orbiting our closest star 4 lightyears away that would be a movement of 0.4 inches an arc second. This calculates to a single orbit for the blackholes to be 30,000 years.
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- Because the universe is expanding these two supermassive blackholes may never merge. However, astronomers hope to learn much more from this unusual astronomical event. No one said this going to be easy.
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- Other Reviews on this topic:
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- 2020 - . Blackholes when did they first appear? How did the first stars form?
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- 1936. - Are there rogue blackholes? Could they explain Dark Matter?
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- 1918. - Which came first blackholes or galaxies?
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- 1908. - How the mass of a blackhole is calculated?
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- These reviews list an index of several other reviews on what we have learned about blackholes. All available upon request.
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