Expert: Philip Stahl - 7/5/2008

Question
QUESTION: if a type Ia supernova, at the distance of 1000 pc, dumps as much gamma-ray radiation onto the earth as 1,000 solar flares then what would happen to us if ik pegasi explodes as a ia supernova roughly 300-500 light years away in a few million years??
(because its moving away from us at 20.4km/s)

ANSWER: Hello,

How many rounds are we going to go with this?

Anyway, it seems you have misconstrued the answer to the question.I never said anywhere that this alleged (to be) Type 1a supernova "dumps as much gamma radiation" as "1000 solar flares". I said ONE Type IV solar flare produced more radiation that the intensity figure you cited (100,000 erg/(cm^2) )

Let us say that at 1 kpc this amount of radiation would be expected to be produced from the exploding star. Then at a distance of 500 kpc the intensity would be at (from the inverse square law for radiation):

~ 4 x 10^5 ergs/cm^2

This is definitely larger than the output from the largest flares recorded on the Sun, and thus likely to significantly erode the ozone layer. Perhaps by as much as 90% or maybe even 100%.

Is this the end of human life? Not necessarily. The ozone region over the Antarctic was already absent from some years, and this didn't annihilate penguins etc.

Yes, much more UV radiation from the Sun will penetrate, but humans will have to adapt to it, at least for the period it's missing. Most likely that means staying indoors a lot more, and wearing protective eye wear, clothing when going outside.

Contrast this now with a plausible runaway greenhouse effect by ~ 2050 (according to the Hadley supercomputer forecasts). You are basically, in that scenario, looking at fires such as now striking California, all over the world - combined with enormous downpours in other areas, e.g. Bangladesh, Caribbean (such as recently flooded numerous Mississippi River towns) and also increased heat waves to the point that 120F - 135F days will be commonplace with not much respite at night.

I can tell you right now - with the oil and power grid situation the way it is, it will be impossible to stay cool. Power grids will go down like so many tenpins. A much worsened shortage of oil will add to the woes, and there is no way that "solar" or "wind" will keep 3+ billion people cool! Not even at 78F in their little domeciles.

As we saw in France, in 2003, when 11,000+ people died from the sustained heat - it is not going to be pretty. More than likely MILLIONS will perish around the world - from Singapore to Australia to the Sudan and all points in betwee,  and this toll will be taken every year (and in increasing numbers).

By some reckonings, within 20 years of the initiation of the runaway greenhouse effect, the Great Lakes will no longer exist (evaporation - such as now occurring with Lake Mead), nor will most of the larger fresh water lakes (and smaller ones) of the world. What the sustained mean temperatures of the heat waves (> 135 F each day) don't kill, the lack of water will.

THIS is what we need to worry about. Not IK Pegasi's possible supernova-ing, and trying to parse how much gamma radiation, at what distance, eliminates 70% of the ozone layer, or 85% or 95%.

---------- FOLLOW-UP ----------

QUESTION: thankyou for your response

Well yes, climate change is something to be concerned about.
But I'm not convinced that humans are to blame for that

for example the temperature graphs from nasa show that:
a. From 1940-1970 CO2 rose moderately yet the earth's temperature actually cooled.
b. The temperature in the United States peaked in the mid-1930s, cooled for about 60 years, and now has risen slightly again, although still not as much as it was in the 30s.
These graphs can be found at www.giss.nasa.gov.
people back in the 70's concerned of global cooling
now its global warming...

anyhow i guess my real concerns aren't in place because i'm more concerned about some hypothetical explosion 150 light years from here...
i guess what i'm confused about is one article on wikipedia said gamma rays from the ia supernova explosion could effect us from 1 kiloparsec away ...i don't know if thats true or not..

i also heard that it can't affect us in anyway if its over 100 ly away

so i'm just a little confused
and so i'm just wondering if this thing is going to explode and kill us all or not lol....

thankyou philip


Answer
Hello,

Again, you are confusing different aspects of the problem, in this case global dimming with global warming. It has been evident with some recent studies (e.g. Gerry Stanhill) that global "dimming" was quite pronounced in the decades you note and actually concealed much of global warming's worst effects. Although the effect varied greatly from place to place, overall the decline amounted to 1-2% globally per decade between the 1950s and the 1990s.

Dimming appears to be caused by air pollution. Burning coal, oil and wood, whether in cars, power stations or cooking fires, produces not only invisible carbon dioxide (the principal greenhouse gas responsible for global warming) but also tiny airborne particles of soot, ash, sulphur compounds and other pollutants.

This visible air pollution reflects sunlight back into space, preventing it reaching the surface. But the pollution also changes the optical properties of clouds. Because the particles seed the formation of water droplets, polluted clouds contain a larger number of droplets than unpolluted clouds.Research shows that this makes them more reflective than they would otherwise be, again reflecting the Sun's rays back into space.

Right now, the evidence points to the dimming effect receding so that the warming that had been concealed by it is now ramping up.Thus, the warming from greenhouse gases has been offset by a strong
cooling effect from dimming - in effect two of our pollutants have been cancelling each other out. This means that the climate may in fact *be more sensitive to the greenhouse effect* than thought.

If so, then this is bad news, according to Dr Peter Cox, one of the world's leading climate modellers. Even the most pessimistic forecasts of global warming may now have to be drastically revised upwards. That means a temperature rise of 10°C by 2100 could be on the cards, giving the UK a climate like that of North Africa,
and rendering many parts of the world uninhabitable. That is unless we act urgently to curb our emissions of greenhouse gases.

Having been in Alaska (1985-86) when Prof. Gunther Weller exposed the large warming there for the first time, and traced it to CO2 concentrations in his ice core samples (dated from the start of the Industrial Revoution) I have NO doubt humans are responsible. The evidence is there, in plain and obvious sight - especially if one ventures to Alaska and looks. You will see the melting permafrost effects all opver Fairbanks, as well as the incredible recession-retreat of the Portage Glacier (near Anchorage) in just one century. THIS CANNOT BE DUE TO ANY SOLAR EFFECTS!!!!

The maximal magnitude of inherent solar -induced climate variability was probably first highlighted by Sabatino Sofia et al in their paper 'Solar Constant: Constraints on Possible Variations Derived from Solar Diameter Measurements', in Science, Vol. 204, 1306, 1979. Their estimate was a solar change in irradiance of roughly 0.1 % averaged over each solar cycle. (Irradiance is a measure of the energy per square meter received from the Sun).

More recent space-based observations appear to show a variation in solar irradiance of at least 0.15% over the standard 11-year solar cycle. (E.g. Parker, E.N., Nature, Vol. 399, p. 416). However, even with this higher percentage ascribed to solar changes, the heating effect is nowhere near comparable to that induced from man-made global warming. (See, e.g. Martin I. Hoffert et al, in Nature, Vol. 401, p. 764).

As the authors in the latter study point out, the heating component arising from greenhouse gas emissions from 1861-1990 amounted to anywhere from 2.0 to 2.8 watts per square meter. The solar variability component detected over the same period amounted to 0.1 to 0.5 watts per square meter. Thus, even the MAXIMUM solar variability amounted to only a fraction (25%) of the MINIMUM power input from human-induced greenhouse warming!


You may also want to read other responses I have given on this topic, as well as go to an excellent site:

www.realclimate.org


Re:IK Pegasi, again, your "confusion" stems from the fact there are no hard and fast data to use by which to extrapolate any current model of IK Pegasi to a future, assumed supernova radiation intensity- produced at a given distance. Even the 100,000 ergs/cm^2 is a pure conjecture. That may or may not be. Probably, what the author intended was to use that as a hypothetical *standard* for SOME influence on the ozone layer for an exploding nameless (garden variety candidate) star at 1 kpc. This is not to say IK Pegasi will attain the same from its own distance, or indeed, exactly what effects it will have.

One would likely have better odds playing his first game of 'blackjack' at a Vegas casino than trying to guess the radiation inten sity and terrestrial effects of IK Pegasi if and when it does explode.

As I indicated, I am much more concerned with global warming than some distant and vague threat from this star. If most predictions of the IPCC turn out to be valid - as I believe they will be from the research I've seen - humans will be well cooked and boiled by the time IK blows its top. And if we haven't colonized other distant worlds by then, it will full stop.....i.e. period....marking the end of the human phase of evolution.