Our Unique, Optimal-for-Life, Supermassive Black Hole
I have a problem with the Star Wars movies. Each film opens with the famous words, "In a galaxy far, far away. . . ." Astronomers have observed far, far away galaxies by the thousands, and, unfortunately for Luke Skywalker and friends, none yet seen comes close to possessing the features necessary to allow for advanced life. Our Milky Way Galaxy remains the only known advanced-life-friendly galaxy.
Over the years since astronomers gained the technology to study distant galaxies closely, they have been building a growing list of characteristics that make our home galaxy, the Milky Way Galaxy (MWG), uniquely suitable as a site for advanced life. The latest addition to that list is spectacular: a supermassive black hole like none other.
Research tells us that a supermassive black hole (SMBH)—an object more than a million times the mass of the Sun—resides at the core of every medium, large, and giant galaxy. The galactic core's quantity and density of stars and gas make these SMBHs inevitable.
The "event horizon" is a theoretical boundary around a black hole from which nothing, not even light, can escape. From just outside the event horizon, a typical SMBH emits radiation so intense and deadly as to render advanced life anywhere within the surrounding galaxy impossible. For supergiant galaxies, this radiation can be so powerful as to make advanced life impossible not only within the galaxy itself, but also in thousands of neighboring galaxies. Providentially for us, our galaxy is sufficiently distant from supergiant galaxies that their SMBHs pose no risk to us.
Given that the radiation from the SMBHs in other galaxies is deadly, why isn't the radiation from ours?
Our SMBH's Unusually Low Mass
A principal reason is that our supermassive black hole comes in at a far lower mass—only 4.02 ± 0.16 million times the solar mass1—than the SMBHs in other galaxies of similar size. This comparatively low SMBH mass, in turn, means that far less radiation of the deadly kind emanates from it.
Our SMBH's low mass differs dramatically from what astronomers would anticipate, based on what they observe in all other galaxies. In other galaxies, they see a consistent correlation between the mass of the SMBHs and four specific characteristics of the galaxies wherein they reside. These four predictors are:
1.The number of globular clusters—very dense arrays of 100,000–10,000,000 stars (see Figure 1)—orbiting the galaxy,2
2.The mass of the galaxy's central bulge (see Figure 2),3 which, in most galaxies, contains about half of the galaxy's stars,
3.The galaxy's luminosity,4 and
4.The velocity dispersion (range of velocities) of the stars in the galaxy's central bulge.5
Astronomers also have observed that the mass of a typical SMBH correlates to the type of galaxy that surrounds it.6 For example, the SMBH in an elliptical field galaxy that exists outside of, or on the fringes of, a galaxy cluster will be less massive than the SMBH in a supergiant elliptical galaxy near the core of a large galaxy cluster. Studies also show that the SMBH in a spiral galaxy will be less massive than the SMBH in an elliptical field galaxy. SMBHs in spiral galaxies with a central bar-like structure tend to be slightly less massive than SMBHs in spiral galaxies without a central bar-like structure.7
Because the MWG is a spiral galaxy with a central bar-like structure (see Figure 3), astronomers would expect our SMBH to be at least somewhat less massive than the four predictors listed above would indicate. That expectation is based on the average characteristics of known galaxies. However, the mass of our galaxy's SMBH appears far lower than these differences would imply.
The mass of the Andromeda Galaxy's SMBH, for example, does align with the four typical predictors. However, given that the MWG possesses the same mass as the Andromeda Galaxy (total mass for both equals about 1.5 trillion solar masses)8 and given that both are spiral galaxies with a bar,9 our galaxy's SMBH should have about the same mass as Andromeda's. Instead, it measures nearly 20 times less massive.
Due to this extraordinary feature, our galaxy's SMBH has nearly 20 times less potential to emit deadly radiation from the region just outside its event horizon. This difference by a factor of 20 in the mass of our SMBH explains, in part, why advanced life can exist and survive in the MWG.
Our SMBH's Unusual Quietness
Another important factor that allows for advanced life to exist in the MWG is that its SMBH remains abnormally quiet, at present. The quantity and intensity of deadly radiation emitted by a SMBH depend on how much gas and dust, plus how many comets, asteroids, planets, and/or stars, the SMBH is drawing toward its event horizon. SMBHs in nearby galaxies consume, on average, one solar-type star about every 100,000 years.10 When this consumption occurs, a bright flare, lasting several months, sends deadly radiation throughout the galaxy. These same galaxies consume stars smaller than the Sun about once every 10,000 years, and the shower of deadly radiation in these cases lasts several days to weeks. These galaxies also consume molecular gas clouds on time scales ranging from once a century to once every few millennia. These events, likewise, result in deadly radiation emission lasting days to weeks.
By contrast, our galaxy's SMBH produces tiny flares on an almost daily basis that last only hours.11 In 2012, three astronomers demonstrated what feeds this consumption process: the existence of spherical clouds of comets and asteroids (similar to our solar system's Oort cloud) surrounding all SMBHs in active galactic nuclei.12 Because a relatively modest Oort cloud surrounds our galaxy's SMBH, frequent tiny flares are the norm for us.13
As several astronomers have noted, the MWG's nucleus is exceptionally quiet and has been for billions of years.14 The low mass of our galaxy's SMBH, the tiny size of its surrounding Oort cloud, and the lack of merger events with large- and medium-sized dwarf galaxies over the past several billion years explain why advanced life has survived and thrived on Earth throughout the past 3.8 billion years. That extremely low activity level just outside the event horizon of both our SMBH and the nearby Andromeda Galaxy's SMBH over the past 10,000 years has allowed global human civilization to emerge and flourish.
Its unusually low mass and quietness demonstrate why our galaxy's SMBH is like none other. It appears exquisitely fine-tuned and designed to make possible not only the existence of human beings but also the development of global, high-technology civilization. Thus, the notion that Someone intended billions of humans to exist, to possess high levels of technology, and to use that technology for a specified purpose stands as a firmly plausible—I would say the most plausible—scenario. •
1. A. Boehle et al., "An Improved Distance and Mass Estimate for Sgr A* from a Multistar Orbit Analysis," Astrophysical Journal 830 (Oct. 3, 2016): doi:10.3847/0004-637X/830/1/17.
2. Rosa A. González-Lópezlira et al., "The Relation between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies: The Case Study of NGC 4258," Astrophysical Journal 835 (Jan. 30, 2017): doi:10.3847/1538-4357/835/2/184.
3. Yohei Miki et al., "Hunting a Wandering Supermassive Black Hole in the M31 Halo Hermitage," Astrophysical Journal 783 (Feb. 20, 2014): doi:10.1088/0004-637x/783/2/87.
4. Kayhan Gültekin et al., "The M-σ and M-L Relations in Galactic Bulges, and Determinations of Their Intrinsic Scatter," Astrophysical Journal 698 (May 19, 2009): doi:10.1088/0004-637X/698/1/198.
5. Alper K. Ateş, Can Battal Kılınç, Cafer İbanoğlu, "On the M-σ Relationship and SMBH Mass Estimates of Selected Nearby Galaxies," International Journal of Astronomy and Astrophysics 3 (July 2013): doi:10.4236/ijaa.2013.33A001; Wol-Rang Kang et al., "Calibrating Stellar Velocity Dispersions Based on Spatially Resolved H-Band Spectra for Improving the MBH-σ* Relation," Astrophysical Journal 767 (April 10, 2013): doi:10.1088/0004-637X/767/1/26.
6. K. Zubovas and A. R. King, "The M-σ Relation in Different Environments," Monthly Notices of the Royal Astronomical Society 426:4 (Nov. 11, 2012), 2751–2757: doi:10.1111/j.1365-2966.2012.21845.x.
7. Markus Hartman et al., "The Effect of Bars on the M•-σe Relation: Offset, Scatter, and Residuals Correlations," Monthly Notices of the Royal Astronomical Society 441:2 (June 21, 2014), 1243–1259: doi:10.1093/mnras/stu627; Sergei Nayakshin, Chris Power, and Andrew R. King, "The Observed M-σ Relations Imply that Super-Massive Black Holes Grow by Cold Chaotic Accretion," Astrophysical Journal 753:1 (June 11, 2012): doi:10.1088/0004-637X/753/1/15.
8. Laura L. Watkins et al., "Evidence for an Intermediate-Mass Milky Way from Gaia DR2 Halo Globular Cluster Motions," Astrophysical Journal 873:2 (March 12, 2019): doi:10.3847/1538-4357/ab089f; Prajwal R. Kafle et al., "The Need for Speed: Escape Velocity and Dynamical Mass Measurements of the Andromeda Galaxy," Monthly Notices of the Royal Astronomical Society 475:3 (April 2018): doi:10.1093/mnras/sty082; Jorge Peñarrubia et al., "A Dynamical Model of the Local Cosmic Expansion," Monthly Notices of the Royal Astronomical Society 443:3 (Sept. 21, 2014): doi:10.1093/mnras/stu879.
9. Rachael L. Beaton et al., "Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy," Astrophysical Journal Letters 658:2 (April 1, 2007): doi:10.1086/514333.
10. Kastytis Zubovas, Sergei Nayakshin, and Sera Markoff, "Sgr A* Flares: Tidal Disruption of Asteroids and Planets?" Monthly Notices of the Royal Astronomical Society 421:2 (April 1, 2012): doi:10.1111/j.1365-2966.2011.20389.x.
12. Sergei Nayakshin, Sergey Sazonov, and Rashid Sunyaev, "Are Supermassive Black Holes Shrouded by 'Super-Oort' Clouds of Comets and Asteroids?" Monthly Notices of the Royal Astronomical Society 419:2 (Jan. 11, 2012): doi:10.1111/j.1365-2966.2011.19777.x.
13. Ibid., note 10.
14. F. Hammer et al., "The Milky Way, an Exceptionally Quiet Galaxy: Implications for the Formation of Spiral Galaxies," Astrophysical Journal 662:1 (June 10, 2007): doi:10.1086/516727; F. Hammer et al., "The Milky Way and Other Spiral Galaxies," Assembling the Puzzle of the Milky Way, edited by C. Reylé, A. Robin, and M. Schultheis, EPJ Web of Conferences 19 (Feb. 7, 2012): doi:10.1051/epjconf/20121901004.
is an astrophysicist and the founder and president of the science-faith think tank Reasons to Believe (RTB).This article originally appeared in Salvo, Issue #50, Fall 2019 Copyright © 2020 Salvo | www.salvomag.com https://salvomag.com/article/salvo50/dark-matters