Terror Defense No Al Qaida Terror
Download 2.62 Mb.
|
- Navigate this page:
- No impact- our isolation in the Milky Way solves, and they only happen in the interior every billion years
- No impact- heavy elements, distance, and early warning.
Gamma Ray BurstsZero risk- we’re too far awayJanek 15 Vanessa earned her bachelor's degree B.S. in Astronomy and Physics from Wheaton College. She currently works in analyzing eclipsing binary star systems. Astronomers See a Massive Black Hole Tear a Star Apart by VANESSA JANEK on JANUARY 28, 2015 http://www.universetoday.com/118555/astronomers-see-a-massive-black-hole-tear-a-star-apart/♥Tina Today, however, Earth appears to be relatively safe. Galaxies that produce GRBs at a far higher rate than our own, such as the Large Magellanic Cloud, are currently too far from Earth to be any cause for alarm. Additionally, our Solar System’s home address in the sleepy outskirts of the Milky Way places us far away from our own galaxy’s more active, star-forming regions, areas that would be more likely to produce GRBs. Interestingly, the fact that such quiet outer regions exist within spiral galaxies like our own is entirely due to the precise value of the cosmological constant – the factor that describes our Universe’s expansion rate – that we observe. If the Universe had expanded any faster, such galaxies would not exist; any slower, and spirals would be far more compact and thus, far more energetically active. No impact- our isolation in the Milky Way solves, and they only happen in the interior every billion yearsPiran and Jimenez 14 Title: On the Role of GRBs on Life Extinction in the Universe Authors: Tsvi Piran, : Racah Institute of Physics, The Hebrew University, Jerusalem Raul Jimenez is a professor of Theoretical Physics and Astrophysics at The Institute of Cosmos and holds a Ph. D in theoretical physics First Author’s Institution Submitted on 8 Sep 2014 (v1), last revised 13 Nov 2014♥Tina Where stars are denser, LGRBs are more likely—the authors find that the innermost 25% of Milky Way stars are likely to see lethal LGRB events at least once per billion years. A billion years into life on Earth, we had just barely mastered photosynthesis and were still a billion years away from cell nuclei. Imagine if every time we got there, the slate was wiped clean by a GRB. We wouldn’t manage to get very far. In addition to looking at the GRB hostility in other areas of the Milky Way, the authors look at other locations in the universe. The Milky Way is isolated enough that we’re not prone to GRBs from nearby galactic neighbors, but in other spots the universe is much more densely packed. The authors posit that those dense regions are less friendly to life because of LGRBs, and that galaxies are only habitable in “in voids and filaments of the cosmic web,” which is a lovely way to put “low-density.” The impact is probable… with a 5 BILLION year time frame, and the probably drops significantly if you only count the ones that will cause real damage.Piran and Jimenez 14 Title: On the Role of GRBs on Life Extinction in the Universe Authors: Tsvi Piran, : Racah Institute of Physics, The Hebrew University, Jerusalem Raul Jimenez is a professor of Theoretical Physics and Astrophysics at The Institute of Cosmos and holds a Ph. D in theoretical physics First Author’s Institution Submitted on 8 Sep 2014 (v1), last revised 13 Nov 2014♥Tina Probability, in %, of at least one GRB having occurred in the past time t with enough flux to produce significant life extinction. For LGRB we show the probability without parentheses when there is a 10% metallicity bias, in parentheses when there is none. We consider three cases of the GRB fluence on Earth (10,100, and 1000 kJ/m2). An inspection of Fig. 2 reveals that maximal danger arises from ∼L∗ bursts. Lower luminosity bursts are more abundant, but their covering fraction of the Galaxy is too small. Higher luminosity bursts can destroy life in a large fraction of the Galaxy, but they are extremely rare. From the point of view of computational certainty, these results are reassuring, as the confidence in our determination of the rate of events around L∗ is good. This is also important from another point of view. Spatially, GRBs are concentrated within regions of the highest SFR [29,30]. The dominance of strong GRBs whose radius of influence is a few kpc implies that we can ignore this spatial inhomogeneity, and the approximation that the distribution of LGRBs follows the distribution of matter in the galaxy holds. We find that the probability of a LGRB, in the past 5 Gyr (giga years), with a fluence of 100 kJ/m2 on Earth to be higher than 90%, and in the last 0.5 Gyr this probability is 50%. It is somewhat surprising that this result (a 50% chance of a biospherically important event in a half Gyr) is so similar to the original calculation in Thorsett [1]. At a lower fluence, 10 kJ/m2, these probabilities are higher than 99.8% (95%) for 5 Gyr (0.5 Gyr), and thus are nearly certain. However, the chances of a truly catastrophic event with a fluence of 1000 kJ/m2 are at most 25%, thus making it unlikely. These probabilities are, of course, much larger (see Table II) if we ignore the suppression of GRBs in the Milky Way due to large metallicity. No impact- heavy elements, distance, and early warning.Phy.org 13 Don’t worry about getting fried by gamma ray burst, researchers say. Dec. 10 2013 Provided by University of Alabama in Huntsville http://phys.org/news/2013-12-dont-fried-gamma-ray.html♥Tina The chances of Earth being fried by a burst are exceedingly rare. In fact, say Dr. Rob Preece, doctoral candidate J. Michael Burgess and Dr. Michael S. Briggs, Earth was actually at the center of the hit from April's big gamma ray burst, which they picked up on equipment aboard the Fermi Space Telescope that UAH and partners NASA/MSFC and the Max Planck Institute for Extraterrestrial Physics in Germany designed and tested. Yes, we took a direct hit. But the collapsing star that created the burst was so far away that it was very weak when it reached us. Stars that collapse and produce these bursts are far away, the researchers say, in portions of the universe that were created early after the Big Bang event, portions where there are a lot of lighter elements that were flung far. Closer to Earth, there are a lot of heavier elements that suppress the collapse of stars. "Our observations show that gamma ray bursts are less common in the immediate universe," said Dr. Briggs. "These bursts occur in younger galaxies," said Burgess. "We're in the oldest galaxy in our immediate universe because as you look deeper into space you are looking back into time." So any burst generated out there will come from really far away where we can detect it early, and it will be a comparative pipsqueak by the time it gets here. "As I was thinking about it, I realized that we would have ample warning," Dr. Preece said. The stars involved are huge. "They blow off winds that we can see well in advance. We would know ahead of time if one of these guys was ready to go off." Directory: file -> view view -> Western Europe after wwii view -> Author study: paul fleischman view -> Qpa1 7ela study Guide view -> Arctic Oil/Gas Neg view -> November 1970 Approximately 150,000-500,000 deaths Bhola Cyclone Bangladesh view -> Grade Level: 6 Unit of Study: Caribbean glce view -> Citation: Duffield, Katy view -> Table of Contents Lesson # view -> Chinese Wind Energy Disad Download 2.62 Mb. Share with your friends:
|