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Is IK Pegasi (HR 8210) dangerous to us at all?

  1. Jun 26, 2008 #1
    IK Pegasi (HR 8210) is a binary star system that is ~150 light years from us that is expected to blow up as a 1a supernova in a few million years.
    I've heard that the minimum safe distance from supernovae is ~30 light years away. I'm not sure if this is true or not.
    I have three questions regarding this topic.

    1) If this star exploded as a type 1a right now, would it be a threat to us?
    2) What is the safe distance (in light years) from these supernovae?
    3) does that safe distance from supernovae apply to all types of supernovae? (II, 1a, 1b, 1c)
  2. jcsd
  3. Jun 27, 2008 #2
    A supernova is dangerous for us is it stands at a distance less than 100 ly.
  4. Jul 4, 2008 #3
    I'm a little confused because on this excerp from http://www.tass-survey.org/richmond/answers/snrisks.txt

    the author says gamma radiation could be a threat at more than 1 kiloparsec away

    Gamma-rays from the explosion (much based on words of wisdom from
    David Palmer - thanks, Dave!)

    One way to estimate the effect of SNe in gamma-rays is to compare the
    amount of power they produce in gamma-rays ALONE with that from the
    Sun at ALL wavelengths:
    distance at which power
    power is equal to Sun's total
    Sun 10^33 erg/s (all wavelengths) 1 AU
    SN II 10^39 erg/s (gamma + X-rays) 1200 AU ~ 0.006 pc
    SN Ia 2x10^41 erg/s (gamma + X-rays) 17000 AU ~ 0.08 pc

    In somewhat more detail: both X-rays and Gamma-rays from SN 1987A
    were due to the decay of radionucleides, primarily Co56 from the
    Ni56->Co56->Fe56 decay chain. Gamma rays, primarily at
    0.847 and 1.238 MeV, were downgraded by Compton scattering in the
    envelope (keeping the envelope hot and luminous) and then emerged at
    lower energies in the X-ray and gamma-ray range. The unscattered
    photons at 0.847 and 1.238 were also seen.

    In greater detail: observations of the flux in X-rays and gamma
    rays from the Sun reveal that most of the energy is in the X-rays,
    with relatively small fractions in the gamma-ray regime. Using data
    from Colhane et al. (Solar Physics 153, 307 [1994]), Baoz et al.
    (Solar Physics 153, 33 [1994]) and McConnell et al. (Adv. Space Res.,
    v 13, n 9, 245 [1993]), I find

    Energy from Sun during flares
    Satellite energy range duration total power (erg/cm^2)
    Yohkoh 20-? keV 10 sec 350
    COMPTEL (GRO) 1-10 MeV 900 sec 0.01
    GAMMA-1 > 30 MeV 600 sec 0.0002

    By comparison, the flux in the 847 and 1238 keV lines due to
    the decay of Ni-56 in a type Ia SN is estimated to be (data from
    Ruiz-Lapuente et al., ApJ 417, 547 [1993]) at a distance of 1000 pc

    SN Ia ~1 MeV ~60 days ~40,000

    This is significant -- a type Ia SN, at the distance of 1000 pc,
    dumps as much gamma-ray radiation onto the earth as 1,000
    solar flares.
    Even when the Sun is at the peak of its activity
    cycle, I don't think it flares ten times a day, so, even at a
    kiloparsec, a type Ia SN would outshine the Sun in gamma rays.

    However, while I _do_ know that we easily survive even the greatest
    solar flares, I don't know how a large increase in the gamma-ray
    flux over a period of several months would affect the earth's
    atmosphere. Steve Thorsett, in a preprint "Terrestial Implications
    of Cosmological Gamma-Ray Burst Models," quotes sources which
    suggest that considerably more than 100,000 erg/(cm^2) in
    gamma-rays are needed to destroy the ozone layer, so it seems
    that a type Ia would have to be closer than 1 kpc to cause
    significant damage.
  5. Jul 7, 2008 #4
    I think we will have much bigger problems in the next million years...
  6. Jul 7, 2008 #5
    i don't know how accurate that statement i about one kilo-parsec because i asked some guy from NASA and he said that ik pegasi will be about 500 light years away in a few million years
    and probably won't even explode for a few 100 million years.
    and he said a supernova farther than 200 lightyears is where there is no effects what so ever on our atmosphere
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