The ultimate Hollywood disaster movie would portray the catastrophic consequences of a nearby supernova eruption. If one were to occur within 1,000 light-years of Earth, it would be the end of civilization as we presently enjoy. A supernova eruption closer than 100 light-years from Earth would bring devastating health consequences for human beings.

Supernovae are the final titanic explosions of stars with initial masses that exceed 9 times the Sun’s mass. At peak brightness, a single supernova can outshine 100 billion ordinary stars. Figure 1 below shows a supernova outshining its host galaxy, NGC 4526.

Figure 1: Supernova 1994D in the NGC 4526 Galaxy. The supernova is to the lower left of the galaxy’s spiral arm structure. Image credit: NASA/ESA/Hubble Space Telescope

 

Supernovae are especially common in spiral galaxies. While our Milky Way Galaxy’s supernova eruption rate has been slowly declining over the past three billion years, it still averages about three supernova eruptions per century.

Not all spiral galaxies have supernova eruption rates as low as the Milky Way Galaxy (MWG). NGC 1559 is a barred spiral galaxy just like the MWG (see figure 2). Though it is a hundred times smaller than the MWG, NGC 1559 has had four supernova eruptions within the past 35 years. Taking into account NGC 1559’s much smaller size, its supernova eruption rate works out to 400 times greater than the average rate for the MWG!

Figure 2: The Barred Spiral Galaxy NGC 1559. Image credit: NASA/ESA/Hubble/Mathias Jage

Even with a rate as low as three supernova eruptions per century for the MWG, one would wonder how humanity has escaped devastation. Part of the answer is that the MWG is large—about 100,000 light-years in diameter. The major part of the answer, however, is that humans are living on Earth at a time when very few nearby supernovae have erupted and those that have were not near enough to wipe us out.

Ice Age Supernovae
Astronomer Richard Firestone’s analysis of the radiocarbon and beryllium isotope ratio records established that within the last 300,000 years, 23 supernovae have erupted within 1,000 light-years of Earth.¹ This rate is more than four times below the normative rate.

Carbon-14 dating leaves little doubt that humans have been on Earth for at least the past 45,000 years. Firestone showed that the same “radiocarbon record for the past 50 kyr [50,000 years] is completely explained by the occurrence of four, powerful, near-Earth (<300 pc) [less than 980 light-years] cosmic ray events.”² Table 1 shows the dates and distances from Earth of these four past supernova eruptions.

Table 1: Recent Nearby Supernova Eruptions

date (years ago)	distance (light-years)
44,000	360
37,000	590
32,000	520
22,000	810

For the supernova event that occurred 44,000 years ago, during the several months following the eruption, Earth’s surface life was exposed to about 40 times the current cosmic radiation dose. Over the next 1,500 to 3,500 years, the cosmic radiation exposure was 4 times the current dose level. In the months following the 37,000 and 32,000 years ago events, Earth’s surface life was exposed to about 15 and 19 times the present cosmic radiation dose.

The consequences for human exposure to cosmic radiation 40, 19, and 15 times more intense than the current level was enhanced mutation rates and incidences of cancer. The production of much greater amounts of NO_x compounds in the atmosphere caused respiratory health issues.

Beyond human health consequences, the much more intense cosmic radiation devastated the stratospheric ozone shield. This devastation dramatically increased the amount of ultraviolet radiation reaching Earth’s surface.

This increased ultraviolet radiation brought three major consequences. First, it dramatically lowered the food productivity of plants. Second, it brought global mean temperature increases of 3–4° Celsius, increases that are observed in the Antarctic and Greenland ice core records. Third, it devastated phytoplankton, thereby contributing to global warming and depleting fish stocks.

While not severe enough to bring about the extinction of the human species, each of the events listed in Table 1 would have made the maintenance of the current human population level and human civilization level impossible, not just for several months but for at least several centuries, if not for several millennia. For all four of the events listed in Table 1, it would not be possible to grow sufficient food to feed in excess of a billion human beings.

Interglacial Supernovae
For the past 10,000 years humans have been enjoying a warm interglacial period. It is an interglacial like no other. It is the only one where the global mean temperature has not changed by more than 2° Celsius. Because of this unprecedented period of extreme global stability, Earth is able to sustain more than 7 billion humans, where most of these humans have access to high-technology civilization.

This same time period is unprecedented in another way. During this period there has not been a single supernova eruption closer to Earth than 5.080 light-years. Table 2 lists all the detected supernovae during the last 10,000 years. Since a supernova as close to Earth as 5,000 light years would be as bright to human observers as the full Moon, we can be confident that no such event would have escaped human attention. Thus, the past 10,000 years must have been free of any supernova events closer to Earth than 5,000 light-years.

Table 2: Known Supernova Eruptions in the Past 10,000 Years

date	distance (light-years)
185 AD	8,200
386 AD	14,700
393 AD	34,000
1006 AD	5,080
1054 AD	6,520
1181 AD	10,430
1572 AD	7,490
1604 AD	9,450
1671 AD	11,080
1868 AD	25,000

Supernova eruptions as distant as the ones listed in Table 2 pose no health threat to humanity. Neither do they pose any limitations on food productivity and, thus, on human population levels. Some of the more nearby supernova events in Table 2 could damage satellite electronics.

As my sons remind me, any damage to the GPS system of satellites would be the end of civilization as we know it. Fortunately for my sons and other members of their generation, there has not been a single supernova eruption closer than 10,000 light-years during the past 400 years. At that distance, supernova eruptions pose no threat to electronics and technology we currently possess or conceivably could develop within the next several decades.

It seems evident that God has had his supernatural hand on the MWG’s supernova events. At the same time that he has blessed us with an unprecedented period of extreme climate stability, he also has blessed us with an unprecedented period of no supernova eruptions that could possibly limit our population, technology, or capability to take the good news of salvation through Jesus Christ to all the people groups of the world.