From our single benefit location of the universe, the three-dimensional location is really difficult to understand.
We can easily map the stars in relation to each other, but it is very difficult to know which is near and which is far.
One way to determine the distance of objects in space is by using standard candles – known internal luminous objects. Astronomers measure the difference between how bright a light object really is, and how it appears to us light-years away, and use that difference to calculate how much light travels.
These candles include pulsing stars whose inner brightness is connected to the time of its pulses, and with a supernova limited peak brightness range.
Now, astronomers have demonstrated the subtlety of what seems to be the universe’s most probable instrument for this mass – supermassive black holes. Or, at least, their echoes.
“Measuring the distance of the universe is a fundamental challenge in astronomy, so the possibility of taking an extra trick in one’s sleeve is very exciting,” said Yu Shen, an astronaut from the University of Illinois at Urbana-Champaign.
You may feel a little confused here. While it is true that we know (more or less) how bright black holes are, it is of no help – because it is, as opposed to bright.
They do not emit any sensible radiation; They’re effectively invisible.
The Milky Way galaxy contains billions of star-mass black holes; We have identified only a handful of people.
Supermassive black holes in the heart of galaxies, however, are very different kettles of fish.
No, we still can’t see them; But if it is active, the surrounding material becomes really very bright. And the way light behaves in this immediate environment can be used to work out its inner brightness.
An active supermassive black hole is one that feeds the material, and this material is designed around a black hole in a well-known architecture. At the center is the supermassive black hole itself, an organism that could be tens of millions to billions of times the mass of the Sun.
Around this a disk of material rotates, entering a black hole by gravity, like a little water circulating and falling into a gutter. This is an attraction disc and the intense gravitational and frictional forces in it heat up the material and cause it to bring a bright glow. But astronomers have not measured it.
(Alma [ESO/NAOJ/NRAO])
Outside the accretion disc is a large cloud, a dusty sweet-shaped ring called a torus. The whole composition is placed as in the picture above. It is the external torus that is the key to a technique known as echo mapping or reverberation mapping.
Each time and again, the area of the action disc near the active supermassive black hole fills brightly in mostly optical and ultraviolet wavelengths – and when it reaches the torus, it “echoes”.
Ical optical and ultraviolet light is absorbed by the dust cloud, which as a mid-infrared light heats and emits thermal energy.
Attraction disks can be large; It can take years for light to reach and re-emit torus. But we know the speed of light, so astronomers can use the time between a flame and an echo to calculate the distance between the inner disk and the inner edge of the torus.
This is where it gets really clever. We know that the inner edge of the enhanced disc is very hot. And we know that the disk cools as we move beyond the black hole.
Only when the temperature rises to about 1,200 degrees Celsius (2,200 degrees Fahrenheit) can dust clouds form.
Therefore, the distance between the torus and the inner edge of the attraction disc is directly proportional to the very hot temperature.
If we know the distance, we can calculate the temperature – and once we know the temperature, we can calculate how much light that region emits. Boom. Internal brightness. It’s called a link RL relationship (For radius and luminosity).
Well, obviously it’s not as easy as “booming”. You need to look at black holes very carefully over a long period of time to detect a time / ultraviolet flash and mid-infrared echo.
A team of astronomers led by Qian Yang of the University of Illinois at Urbana-Champaign combined data from nearly two decades of data collected by ground-based optical telescopes to detect two-point flash.
They then studied data collected between 2010 and 2019 to find corresponding infrared flares through NASA’s near-Earth ject project Wide Field Infrared Survey Explorer.
They identified 587 supermassive black holes with 7-pixel flash and mid-infrared echoes – the largest survey of its kind.
And although there is still scope to improve the data – infrared surveys have not been able to expand the full infrared range, which means that there is absolute uncertainty in the calculation of distances – they have confirmed that the RL relationship scales, and that it resonates. The same way towards supermassive black holes of all sizes in their sample.
The work of refining the measurements will continue.
The team is working to improve their models to better block the behavior of dust and how to emit their infrared light. And, of course, the ongoing survey with good technology will continue to provide high quality observations.
“The beauty of echo mapping technology is that this supermassive black hole doesn’t go away anytime soon,” Yang said. “So we can measure the dust echoes again for the same system to improve the distance measurement.”
Research has been published in Astrophysical Journal.
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