Nerby Supernova Blast

[Zhelom1973]

What if a nearby star let say about 15LY goes supernova, ¿how much time will take the shockwaves to reach the earth?

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What if a nearby star let say about 15LY goes supernova, &iquest;how much time will take the shockwaves to reach the earth? <br />Posted by Zhelom1973</DIV><br /><br />Welcome to Space.com</p><p>Well, the light will take 15 years to get here. 15 LY, means 15 Light Years, which is the fastest possible speed in the Universe.&nbsp;(BTW, there are no supernova candidates that close to us, BTW)</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[Archer17]

Everyone here would definitely have a very bad day. <div class="Discussion_UserSignature"> </div>

 

[robnissen]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Everyone here would definitely have a very bad day. <br />Posted by archer17</DIV><br /><br /><p><font size="3">This link explains that a SN needs to within about 30 ly to kill life on earth, and there are no stars within 60 ly that will go SN within the next few million years.</font></p><p><font size="3">http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980521a.html</font></p><p><font size="3">One interesting potential supernova is Eta Carinae, which&nbsp;may go supernove tomorrow (or even hypernova), or it may go SN in a 100K years.&nbsp; Although it is about 7500 LYs away, Earth is not home free.&nbsp; A supernova can eject massive gamma rays perpendicular to its rotation.&nbsp; If Earth was hit with these targeted gamma rays, it could kill life on Earth.&nbsp; It appears for now that while earth is close to perpindicular to ECs rotation, it is far&nbsp;enough away from 90 degrees not to&nbsp;be hit.&nbsp; But it is also possible that EC could wobble in its rotation such that&nbsp;earth could end up staring down the barrel of a loaded SN.</font></p>

 

[derekmcd]

Much would depend on whether it was a type Ia supernova or a type II.&nbsp; IIRC, there is an order of magnitude difference (or 2 or 3) in the amount of Ergs between the two.&nbsp; Should a gamma ray burst develop, it gets worse.&nbsp; I don't believe there is a definitive answer as to a specific distance. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[Zhelom1973]

<p>Thanks you all for the posts, I know indeed there is no possible candidate to become a SN&nbsp;within 50 Ly from the Earth, but the question is merly hypotetichal, only to know how fast the shock wave could reach the earth estimating the 15 Ly distance the light will take 15 years to reach the planet but, what about the rest of it and I m not talking about only the gamma rays brust, but aso the energy released form such explosion, let me give you guys some proportions for you :</p><p>Star Name: XYXYXY</p><p>Star Mass:&nbsp;120 Times Bigger than our sun</p><p>Supernova Type: II</p><p>Distance from Earth: 15LY</p><p><br />Best Regards</p><p>&nbsp;</p>

 

[crazyeddie]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Thanks you all for the posts, I know indeed there is no possible candidate to become a SN&nbsp;within 50 Ly from the Earth, but the question is merly hypotetichal, <span style="font-weight:bold" class="Apple-style-span">only to know how fast the shock wave could reach the earth estimating the 15 Ly distance the light will take 15 years to reach the planet but, what about the rest of it </span>and I m not talking about only the gamma rays brust, but aso the energy released form such explosion<br /> Posted by Zhelom1973</DIV></p><p>In the initial explosion, stellar material can be ejected at velocities up to 10% of the speed of light, but the actual rate of expansion over time can be highly variable, depending on the density of the surrounding interstellar medium. &nbsp;So to answer your question, the soonest the electromagnetic radiation can reach us is 15 years, as was already stated, and the very soonest the expanding debris shell can reach us is 150 years, but it would probably take much longer. &nbsp;Here's some excerpts from an interesting website:</p><p><span style="font-family:Arial;font-size:12px;-webkit-border-horizontal-spacing:2px;-webkit-border-vertical-spacing:2px" class="Apple-style-span"><a style="font-family:Arial,'SansSerif'" name="evolve"></a><span style="font-style:italic" class="Apple-style-span">As the ejecta expand out from the star, it passes through the surrounding interstellar medium, heating it from 10</span><sup style="font-family:Arial,'SansSerif'"><span style="font-style:italic" class="Apple-style-span">7</span></sup><span style="font-style:italic" class="Apple-style-span">&nbsp;to 10</span><sup style="font-family:Arial,'SansSerif'"><span style="font-style:italic" class="Apple-style-span">8</span></sup><span style="font-style:italic" class="Apple-style-span">&nbsp;K, sufficient to separate electrons from their atoms and to generate thermal X-rays. The interstellar material is accelerated by the shock wave and will be propelled away from the supernova site at somewhat less than the shock wave's initial velocity. This makes for a thin expanding shell around the supernova site encasing a relatively low density interior.</span></span></p><span style="font-family:Arial;font-size:12px;-webkit-border-horizontal-spacing:2px;-webkit-border-vertical-spacing:2px" class="Apple-style-span"><a style="font-family:Arial,'SansSerif'" name="evolve"></a><p style="font-family:Arial,'SansSerif'">&nbsp;</p><table border="0" style="font-family:Arial,'SansSerif'"><tbody><tr style="font-family:Arial,'SansSerif'"><td style="font-size:12px;font-family:Arial,'SansSerif'"><span style="font-style:italic" class="Apple-style-span">While the material swept up by the shock is much less than the mass of the stellar ejecta, the expansion of the stellar ejecta proceeds at essentially a constant velocity equal to the initial shock wave speed, typically of the order of 10,000 km/s. This is known as the "free expansion" phase and may last for approximately 200 years, at which point the shock wave has swept up as much interstellar material as the initial stellar ejecta. The supernova remnant at this time will be about 10 light years in radius. Although the remnant is radiating thermal X-ray and synchrotron radiation across a broad range of the electromagnetic spectrum (from radio to X-rays), the initial energy of the shock wave will have diminished very little. Line emission from the radioactive isotopes generated in the supernovae contribute significantly to the total apparent brightness of the remnant in the early years, but do not significantly effect the shock wave.</span>

 

[Boris_Badenov]

<font size="2">IIRC Vega is a possible&nbsp;candidate for Supernova. We are very nearly directly in the sights of one pole. And at 25.3 LY it certainly would ruin our day if it cut loose with a GRB.</font> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[crazyeddie]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>IIRC Vega is a possible&nbsp;candidate for Supernova. We are very nearly directly in the sights of one pole. And at 25.3 LY it certainly would ruin our day if it cut loose with a GRB. <br /> Posted by borisis</DIV></p><p>I don't believe Vega is a supernova candidate; it doesn't have enough mass. &nbsp;It will go through a red giant phase and eventually shed enough gas as it puffs off it's outer layers to put itself below the Chandrasekhar limit, and this will not happen for close to a billion years, by which time it's orbit about the galaxy will take it well away from our stellar neighborhood.&nbsp;</p><p>A star must have at least 2.5 times the mass of the sun to become a supernova candidate; Vega's mass is 2.11x&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I don't believe Vega is a supernova candidate; it doesn't have enough mass. &nbsp;It will go through a red giant phase and eventually shed enough gas as it puffs off it's outer layers to put itself below the Chandrasekhar limit, and this will not happen for close to a billion years, by which time it's orbit about the galaxy will take it well away from our stellar neighborhood.&nbsp;A star must have at least 2.5 times the mass of the sun to become a supernova candidate; Vega's mass is 2.11x&nbsp; <br /> Posted by crazyeddie</DIV></p><p>I don't recall the exact masses, but I believe the progenitor stars to produce a supernova need to be around 8 solar masses.&nbsp; Between 8 and 20 results in a neutron star.&nbsp; Beyond 20 solar masses may result in a black hole.&nbsp; Keep in mind, this is the original mass of the star during it's main sequence... not the remnant core.</p><p>The remnant core for the creation of a neutron star is 1.4 solar masses and you are correct with your description of Vega and the Chandrasekhar limit.&nbsp; Beyond 1.4 solar masses for the remant core is referred to as the Tolman-Oppenheimer-Volkoff limit.</p><p>In either case, a supernova event is required (as far as I know) to create a neutron star or black hole.&nbsp; Ulimately, the minimum mass of the progenitor star is about 8 solar masses (give or take 1 or 2). </p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>