by Black hole week is in full swing right now, and to celebrate, NASA has released stunning views of the heart of a distant spiral galaxy – as well as the monster supermassive black hole that resides in that heart .
The observations were made by the X-ray Imaging and Spectroscopy Mission (XRISM), led by the Japan Aerospace Exploration Agency (JAXA) with contributions from NASA; they show the center of the spiral galaxy NGC 4151.
This galaxy, located about 43 million light-years away (along with its current supermassive black hole, estimated to have the mass of 20 million suns) appears in vibrant reds and bright blues due to radio waves that to add. That addition comes through data from the Very Large Array (VLA) and the Isaac Newton Telescope Group.
However, there is more to XRISM (“crisis”) observations than their aesthetic value. The X-ray space telescope was able to distinguish iron fingerprints in this galaxy’s Active Galactic Nucleus (AGN), which could help determine the fate of the material swirling around its supermassive black hole. .
Related: An image of the central region of the spiral galaxy NGC 4151 which contains a supermassive black hole
“XRISM’s Resolve instrument captured a detailed spectrum of the area around the black hole,” Brian Williams, NASA’s XRISM project scientist at Goddard Space Flight Center, said in a statement. “The peaks and troughs are like chemical fingerprints that tell us what elements are present and reveal clues about the fate of matter as it approaches the black hole.”
A supermassive black hole engine
Like all AGN, the central engine of NGC 4151 shines brightly because it is powered by a supermassive black hole actively feasting on the surrounding matter.
Not all supermassive black holes are so fat, however. For example, Sagittarius A* (Sgr A*) at the heart of our galaxy, the Milky Way, is so rare that, if it were human, it would consume about one grain of rice every 1 million years.
On the other hand, for an AGN, gas and dust fed by the black hole form a monster within a flattened cloud, called an accretion disk, around the black hole itself. The black hole’s massive gravity also generates intense tidal forces in this accretion disk, which warm the disk and cause it to lie flat.
In addition, matter that does not enter the maw of the monster black hole can be directed towards the object’s poles by powerful magnetic fields that accelerate these particles to near-light speeds, blasting out as two jets, one from each pole This scenario is accompanied by a burst of electromagnetic radiation that, when combined with emission from the accretion disk, produces an AGN brighter than the combined light of all the stars in the surrounding galaxy.
The AGN of NGC 4151 is particularly bright, even for such an active galaxy region, and shows a high degree of variability. This, combined with the fact that it is at the heart of one of the closest active galaxies known, makes the black hole NGC 4151 an ideal subject of study.
The AGN was previously investigated by the Hubble Space Telescope and NASA’s Chandra X-ray Observatory, in an effort to learn more about the interaction between its supermassive black hole and its environment. Understanding the dynamics of both can reveal how the growth of these cosmic titans affects the growth of the galaxies around them.
XRISM is counting calories
XRISM has a distinct advantage over Hubble when it comes to studying AGN NGC 4151. This galaxy happens to be unusually bright in the X-rays that XRISM is capable of studying.
Using its Resolve instrument, which studies the Universe using just 36 pixels, XRISM was able to reconstruct the spectrum of light coming from the AGN. Because chemical elements and compounds absorb and emit light at characteristic wavelengths, they leave their “fingerprints” in such spectra. Sure enough, in the Resolve spectrum from the core of NGC 4151, scientists were able to determine the energies of this AGN peak just below the characteristic emission line associated with the element iron.
Scientists have theorized that most of the power of AGNs is reflected by X-rays emanating from regions of hot and flaming material embedded in the accretion disk near its central black hole. When these X-rays are reflected from the cooler and denser regions of the same swirling cloud of matter, they are believed to cause iron to flare in those regions — indeed the cause of this discovery.
That means the discovery of iron and an X-ray peak around this supermassive black hole creates a clearer picture of the phenomena found in such discs and bulge patches.
The spectrum from the AGN at the core of NGC 4151 also shows absorption lines characteristic of iron in its surroundings. Iron appears to be absorbing rather than emitting in these regions because they are cooler than the dense patches of the accretion disk close to the black hole.
All of this radiation is about 2,500 times more energetic than light in the visible region of the electromagnetic spectrum, the only type of light that our eyes can detect.
RELATED STORIES:
— How do some black holes get so big? The James Webb Space Telescope may have an answer
— The brightest quasar ever seen is powered by the black hole that eats ‘a sun a day’
— Record breaker! The Milky Way’s most monstrous stellar mass black hole is a sleeping giant lurking close to Earth (Video)
Although this particular result from XRISM focuses on iron, it is not the only element that the X-ray telescope can distinguish. The satellite can detect the elements sulfur, calcium, argon and others in AGNs (as well as other celestial bodies) depending on the source.
Each of these elements can tell scientists a different aspect of the stories of the celestial bodies they surround, or even compose. XRISM is therefore a vital instrument for the future of astronomy and the effort to decode the X-ray sky.
