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Could A Faraway Supernova Threaten Earth?

Supernovae, just like any other explosions, are really cool. But, just like any other explosion, it’s preferable to have them happen at a good distance. The star T Pyxidis, which lies over 3,000 light-years away from the Earth in the constellation Pyxis, was previously thought to be far enough away that if anything happened in the way of a supernova, we’d be pretty safe.

According to Edward Sion, Professor of Astronomy and Physics at Villanova University, T Pyxidis may be in fact a “ticking time bomb,” and potential threat to the Earth if it were to go supernova, which it may do sometime in the future, though very, very far in the future on our timescale: by Scion’s calculations, at least 10 million years.

Sion presented his findings at the American Astronomical Society Meeting in Washington, D.C. earlier today. T Pyxidis, which lies in the constellation Pyxis, is what is called a recurring nova. The star, which is a white dwarf, accretes gas from a companion star. As the amount of matter increases in the white dwarf, it occasionally builds up to the point where there is a runaway thermonuclear reaction in the star, and it ejects large quantities of material.

T Pyxidis has had five different outbursts over the course of observations of the star. It was the American Association of Variable Star Observers’ variable star of the month in April, 2002.  The first was in 1890, followed by another outburst in 1902 (these two were discovered much later on photographic plates in the Harvard plate collection). The next three were in 1920, 1944 and 1967. Its average for outbursts is about 19 years, but there hasn’t been one since the 1966 brightening.

The distance estimate to T Pyxidis, revised to 3,260 light-years from the previously estimated distance of 6,000 light-years has prompted a reconsideration of the details about the white dwarf. Hubble images that have been taken of the star would then have to be re-examined so as to revise the amount of mass the star is expected to be ejecting.

If the recurring novae are ejecting enough material, then the white dwarf would stay small enough to continue to go through the phase of recurring novae. However, if the shells of gas repeatedly ejected by the star do not carry enough mass away, it would eventually build up to pass the Chandrasekhar limit – 1.4 times the mass of the Sun – and become a Type Ia supernova, one of the most destructive events in our Universe.

Sion concluded the presentation with the statement (shown here on his last powerpoint slide) that “A Type Ia supernova exploding within 1000 parsecs of Earth will greatly affect our planet”

A supernova within 100 light-years of the Earth would likely be a catastrophic event for our planet, but something as far out as T Pyxidis may or may not damage the Earth. One of the journalists in attendance pointed out this possibility during the questions session and Sion said that the main danger lies in the amount of X-rays and gamma rays that stream from such an event, which could destroy the protective ozone layer of the Earth and leave the planet vulnerable to the ultraviolet light streaming from the Sun.

There remains some doubt as to whether T Pyxidis will go supernova at all. There is a good treatment of this subject in “The Nova Shell and Evolution of the Recurrent Nova T Pyxidis” by Bradley E. Schaefer et al. on Arxiv.

If you’re worried about the dangers of exploding stars, you should check out this video by Phil Plait, the Bad Astronomer. He’ll calm you down.

Source: AAS Press Conference on USTREAM, Space.com

Comments on this entry are closed.

  • agesilaus January 4, 2010, 4:46 PM

    I thought Beetlegeuse was more of a concern, it’s only 640 lya.

  • Lawrence B. Crowell January 4, 2010, 5:46 PM

    The nebula there has a slight resemblence to a swastika.

    I am sure life on Earth has faced supernova of this sorts in the past. Doubtless life on Earth will survive this one, once it has rebounded from the chaos we are creating and are then gone.

    LC

  • Lawrence B. Crowell January 4, 2010, 5:54 PM

    As a small question or controversy, I keep hearing Betelgeuse pronounced everywhere as beetlejuice. Yet I have always thought this was wrong. The name is German and I have always thought it should be pronounced as Be-tel-guise. Yet I suppose the anglophone pronounciation wins the day, at least over here.

    LC

  • star-grazer west coast January 4, 2010, 5:59 PM

    From reading articles and my understanding, should Betelgeuse detonate, about 1% of Earths’ human population (about 65million) will be affected by cancer that affects the whole body and fortunately for the victims, the demise is quick. There are many articles I’ve read, I don’t know how they come up with the figures, but they estimate in a normal year, about 1million people is affected by whole body cancer and dies quickly, these are medical mysteries because the cancer does not start from a certain area of the body but the whole body. I’ve known at least 1 person who succumbed
    to whole-body cancer. It appears the cause for these whole-body cancer is cosmic rays/Neutrinos interacting with the human cells and cause some form of chain reaction I’m not capable of explaining. This article about a future type 1a is too far away to make much of a difference to the human death rate

  • IVAN3MAN January 4, 2010, 6:03 PM

    At the fourth paragraph, in the fifth line:

    It’s average for outbursts is about 19 years,…

    That should be an Its, not “It’s”.

  • Paul Eaton-Jones January 5, 2010, 2:33 AM

    If the star expels enough matter at every outburst then it won’t go supernova and earth is safe and it seems to be doing just that so we’re going to be o.k. When it does go supernova in ten million years time humanity won’t be here so once again we can relax. It really does annoy me when what could be an interesting astronomical article is turned round to focus on how it could/maybe/perhaps impact on humans when in fact the threat it as good as non-existant. The universe is not about us.
    BTW, I was always under the impression that Betelgeaux or Betelgeuse [but never Beetlejuice] is a corruption of the Arabic word ‘al jausa’ which if I remember means ‘middle star’.

  • Torbjorn Larsson OM January 5, 2010, 6:15 AM

    I’ll have to agree with the ‘not very realistic catastrophe’ analysis.

    IIRC we have weathered at least one mass extinction believed to be caused by a supernova. In general, before the Permian event that nearly killed us off, life lost diversity that it never recovered fully between each mass extinction. Somehow that near death experience turned the ecologies around so instead we now measurably gain diversity by mass extinctions.

    Also, the recovery time has been downsized to below 1 My, which is twice the lifetime of H. erectus.
    Which was a long time for a species. Similarly A. ramidus lineage was long lived.

    All I’m saying here is that potentially long-lived Homo may likely see a mass extinction, whether the ongoing anthropic mass population/GW one or a supernova one on top, out. And benefit from it.

    Supernovas created life by creating our solar system. They aren’t much of a destroyer, perhaps a “pepper-upper”.

  • Torbjorn Larsson OM January 5, 2010, 6:31 AM

    @ swc:

    I’m not into medicine, and I have vague recollections of this, but I believe whole body cancers aren’t considered mysterious and that the scenario goes something like this:

    Cancer is, as disease in general, an evolutionary process. I.e. cancer cells in some form or other is all the time developing in animal bodies, and the ones that survive are adapted to our disease defenses.

    They are also adapted in other ways, and I believe whole body cancers are such that they both seed and hormonally suppress rival daughter cells (cancers tend to be sloppy growers by virtue of being non-repressed growers, so loose cells) that encroach on their resources.

    Cancers can be good at manipulating natural cellular growth hormones, again by virtue of being non-repressed growing cells. Generally they hit on the mechanism of manipulating them to grow feeding blood vessels into their growth zone. Those that don’t manage any of this, that compete with each other wholesale for scant resources, are more likely taken care of by our immune system.

    In at least some whole body cancer victims the whole body then has relatively dormant and hiding daughter cells. Those can be set off simultaneously by such things as cancer therapy removing the original suppressing “mother” cancer cluster. (This I believe is another reason, besides remaining broken off cancer tissue, that cancer operations are claimed to be accompanied by cellular toxins that kill growing cells.) This would look a whole body cancer syndrome.

    Note, this vague memory may or may not be a folk tale at this point. You have to check it up.

  • star-grazer west coast January 5, 2010, 9:54 AM

    @Torbjorn Larsson
    I’m really not knowledgeble in the medical field, what I do know is, there was absolutely no history of cancer in the family nor were the persons’ living nor involved in a cancerous lifestyle(smoking,etc) concerning the articles I’ve read.
    About 25 years ago, a close friends’ wife suddenly went from top of life to complete symptoms of cancer throughout her body, in 5 weeks she died dispite all attempts from the medical field to save her. She lost over 70% of her body weight that quickly.Complete autosy showed complete cellular destruction throughout her body.
    Thank you for your explanation.

  • star-grazer west coast January 5, 2010, 10:08 AM

    @Torbjorn Larsson
    addendum, now I remember, she went into coma 48 hours after symptoms started and according to my friend and the hospital, she should’ve died about 8 days after start but life-support kept her alive a few more weeks but destruction of her body continued until the end. This really shocked all who knew/ involved in this case!!!!

  • Paul Eaton-Jones January 6, 2010, 6:06 AM

    I believe that there is evidence that around 37,000 most if not all the ozone layer was blasted off by some ‘nearby’ supernova which hasn’t appeared to have affected us unduly. Also we suffered near extintion about 87,000 years ago when mount Toba erupted in probably the biggest bang since the big one and reduced humans down to a few very few thousand. Apparently [some] geneticists have identified a genetic ‘bottleneck’ which corresponds to a small pool from just after that time.

  • teleskopy.net January 8, 2010, 5:11 AM

    I believe that the main reason Betelgeuse supernova is considered less dangerous because her spin axis is not pointed at us (as seems to be the case here) so there is little risk that jet of high energy particles resulting in explosion will strip Earth ozone layer. T Pyx from the picture at least looks like its pointed in our direction, so we better start stocking up on uv filters… well in 10 mln years we shall have enough, right ?

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