A Second Look at Supernova Remnants

By Jon A. Covey, B.A., MT(ASCP)
Edited by Anita K. Millen, M.D., M.P.H., M.A.

Let’s start with learning what a nova is and go from there. According to one idea, a nova is a star that suddenly ejects some of its matter, flares up and emits a tremendous amount of light that is about 10,000 times brighter than a normal star. This lasts for a few days or weeks and then fades away. The expanding shell of ejected gas may be visible telescopically for several years. Another idea is that novae are white dwarfs belonging to two-star (binary) systems. The companion star is a red giant which loses some of its matter to the dwarf. This influx of matter is heated up and flashes away as an expanding shell. [Abell]

What are Supernovae and Remnants?

A white dwarf star that acquires too much matter (possibly from a companion red giant) becomes unstable and explodes is a supernova. When the star’s mass exceeds that of the sun by 1.2 – 1.4 times, the star begins to degenerate and collapses. The star explosively releases the enormous gravitational energy the collapse generated. [Abell, p. 393-394] Alternatively, a supernova occurs when a star uses up all its fuel and cannot produce enough heat and pressure to maintain the weight of the star’s envelope, the star collapses and then explodes. The explosion propels the outer shell of the star into a rapidly expanding gas mass, leaving behind a pulsating star (a pulsar) such as the Crab Nebula of 1054 A.D. [Abell, p. 393-394] Davies says that the term “supernova remnant” refers to the huge cloud of expanding stellar debris that hurtles outwards from the origin at an initial velocity of upwards from 7,000 km/sec.

We can observe new supernovae visually. They are extremely bright, but after a short while, they can be seen only by radio wave telescopes. George Abell says that supernovae may occur in our galaxy at an average rate of between 30-50 years and that they are commonly observed in other galaxies. From this, one can calculate the number of supernova remnants that should be observable.

Craig Bracy mentioned that one could argue that possibly after 6,000 years supernova remnants (SNRs) are no longer observable. I was faced with this objection by some evolutionists on a CompuServe forum. I was about to reply to this objection when an astronomy buff chimed in saying, “And there are nebula that are significantly older than 6,500 years (modern detectors can detect a nebula that is about 150-200,00 years old. After that it has become too dim and diffuse).” Of course, I wanted to know which nebula were significantly older than 6,500 years and he replied that his Astronomy and Scientific American magazines were still packed and he would give me a reply when he unpacked them. He still hasn’t unpacked them, but he agrees that we should be able to observe SNRs well beyond 6,500 years. Initially, he thought I was referring to SNRs in the visible light range only, but when I explained to him that radio telescopes can observe them far longer, he agreed.

There are two things I would like to mention about supernova remnants (SNRs), contrary to what Hugh Ross said on Greg Koukl’s Stand To Reason program on KBRT AM 740 in March 1996. Hugh said that SNRs would be too dim to observe after 6,500 years. First, if there are any SNRs older than 6,500 years we would be able to observe them, and second, if stellar theory is correct, the number of first, second, and third stage SNRs we observe are consistent with a universe only 7,000 years and not with an older universe. Second, Hugh browbeat the caller’s source for this information, Keith Davies. The caller remarked that Davies had also reported that there weren’t enough detectable SNRs in our galaxy if it really was 10-15 billion years old. Hugh decided Davies didn’t have a very good grasp on big bang theory, missing Davies’ point altogether (perhaps because Hugh wants to push his big bang idea). The following comes from Keith Davies’ report in the Proceedings of the Third International Conference On Creationism 1994.

Time Limits for Observing SNRs

Supernova remnants go through three stages. In stage one, SNRs release prodigious quantities of energy. For a short while, a supernova can outshine an entire galaxy and releases enough neutrinos to power all the stars in a galaxy for several years (about 100 billion stars). The total radiative energy expended per second for second stage SNRs is about 1037 ergs. [Cioffi ] This computes to over 3 million years before a SNR radiates half its initial energy. Radio telescopes can easily detect SNRs during this stage. If we could see radio waves, we would see hundreds of luminous objects several times the diameter of the moon. The actual diameters of SNRs can be very big with older ones perhaps 300 light years across. If that doesn’t impress you, think about this. We could take every star in the our galaxy, about 200 billion, and fit them within a volume having as a radius out to the Pluto’s orbit without them touching. [Van Flandern] You could easily place every star in the known universe within the remnants boundary of one older supernova.

When supernovas enter the third stage they begin to thermally radiate, and they continue expanding to about 650 light years.

Expected Number of SNRs

How many supernova remnants should we expect to see based on t = 25 years (the shorter time span between supernova mentioned by Abell)? If the universe is only 7,000 years old, the number of supernova remnants actually seen for each stage is near the theoretical number that should be seen. Which universe (old or young) do these facts supports? Examine the table below and come to your own conclusion.

SNR StageNumber expected Old UniverseNumber expected Young UniverseActual # seen

The final example is the SNR population of the Large Magellanic Cloud. The observations have caused considerable surprise and loss of confidence….” [Cox]

“Why have the large number of expected remnants not been detected?” [Clark]

“Major questions about these objects that should be addressed in the coming decade are: Where have all the remnants gone?” [National Research Council]

They aren’t there yet. The universe isn’t old enough to have the expected number.


Abell, George O., 1984, Realm of the Universe, Saunders College Publishing, New York, pp. 389-390.

Cioffi and McKee, 1988, Supernova Remnants and the Interstellar Medium, Colloquium Proceedings, eds. Roger and Landeck, CUP, p. 437.

Clark and Caswell, 1979, Monthly Notices of the Royal Astronomical Society, 174:267.

Cox, D., 1986, Astrophysical Journal, 304:771-779.

National Research Council, 1983, Challenges to Astronomy and Astrophysics working documents of the Astronomy Survey Committee, p. 166, National Academy Press.

Van Flandern, T., 1993, Dark Matter, Missing Planets & New Comets, North Atlantic Books, Berkeley, p. 181.

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