 (Hình minh họa: NASA/JPL-Caltec via Getty Images) |
Một vụ va chạm như thế, nếu xảy ra, có thể tỏa ra một năng lượng mạnh bằng vài ngàn quả bom nguyên tử. Tuy nhiên, NASA liền vội trấn an khi loan báo rằng, thiên thạch do nhà thiên văn người Ukraine khám phá và đặt tên 2013 TV135 rất ít có cơ hội đụng phải quả đất.
NASA nói, 99.99% chắc chắn là khi nó xẹt trở lại vào năm 2032, nó chỉ đi vù ngang qua chúng ta mà thôi, và xác suất xảy ra sự va chạm này chỉ là 1 trên 63,000.
Thiên thạch 2013 TV135 được phát hiện vào ngày 8 Tháng Mười, thời gian mà NASA phải đóng cửa vì xảy ra vụ chính phủ liên bang đóng cửa. Nó nhanh chóng được xếp vào chung với hơn 10,000 vật thể khác bay gần quả đất và được xem là vô hại.
Ðường đi ngang trái đất của 2013 TV135 vào hôm 16 Tháng Chín không được xem là suýt đụng phải vì nó ở tận khoảng cách 4.2 triệu dặm, tương đương với 15 lần khoảng cách từ trái đất đến mặt trăng. (TP)
NASA nói, 99.99% chắc chắn là khi nó xẹt trở lại vào năm 2032, nó chỉ đi vù ngang qua chúng ta mà thôi, và xác suất xảy ra sự va chạm này chỉ là 1 trên 63,000.
Thiên thạch 2013 TV135 được phát hiện vào ngày 8 Tháng Mười, thời gian mà NASA phải đóng cửa vì xảy ra vụ chính phủ liên bang đóng cửa. Nó nhanh chóng được xếp vào chung với hơn 10,000 vật thể khác bay gần quả đất và được xem là vô hại.
Ðường đi ngang trái đất của 2013 TV135 vào hôm 16 Tháng Chín không được xem là suýt đụng phải vì nó ở tận khoảng cách 4.2 triệu dặm, tương đương với 15 lần khoảng cách từ trái đất đến mặt trăng. (TP)
Asteroid 2013 TV135: doomsday again (yawn)
Asteroid 2013 TV135 has a 99.998% chance of missing Earth in 2032. Yet it's the 0.002% possibility that is capturing the headlines
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An asteroid plunges towards the Earth. Relax. It (probably) won't happen. Illustration: Getty Images
Head for the hills (although that won't save you). A number of lurid internet headlines today are heavily hinting at doom in 2032 because a 410-metre-wide asteroid could hit the Earth.
If it does, the reports say, it could create an explosion 50 times greater than the biggest nuclear bomb ever detonated. The unreported details, however, paint a rather different picture.
On 8 October 2013, astronomers at the Crimean Astrophysical Observatory in the Ukraine discovered an asteroid. Catalogued as 2013 TV135, it is just one of 10,332 near-Earth objects known to exist.
Astronomers tracked it over subsequent nights, piecing together its orbit. They realised that it had made a close pass to Earth on 16 September, drawing within 6.7 million kilometres of our planet.
Although that is more than 17 times the distance to the moon, any asteroid that can pass closer to Earth than 7.5 million kilometres is automatically dubbed "potentially hazardous" and listed by the International Astronomical Union on a webpage that is rather alarmingly called Dangerous.html.
Things got worse. Based on the preliminary orbit calculation, 2013 TV135 could find itself close to Earth again in 2032. In that year, uncertainties in the orbit mean that it has a 1-in-63,000 chance of hitting our planet. And the doomsday headlines were born.
Yesterday, Nasa rushed to issue "a reality check", in which Don Yeomans, the manager of Nasa's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California stated, "To put it another way, that puts the current probability of no impact in 2032 at about 99.998 percent."
It didn't calm the waters. Instead, the reports chose to highlight that 2013 TV135 had been given a rating of one out of ten on the Torino scale, which ranks the impact hazard associated with near-Earth objects.
As an implication of the danger, the reports point out that there is only one other level 1 asteroid currently known. That's true but it only tells half the story. Upon discovery, a couple of dozen other asteroids have been classed level 1 or more, only to be downgraded later.
The reason is that initially astronomers have very little information with which to calculate an orbit. So the possible path through space is highly uncertain. If Earth appears anywhere within that uncertain path, the asteroid is given a rating on the Torino Scale, usually level 1.
To highlight that this is entirely normal, the exact wording for a level 1 asteroid is: "A routine discovery in which a pass near Earth is predicted that poses no unusual level of danger. Current calculations show the chance of collision is extremely unlikely with no cause for public attention or public concern. New telescopic observations very likely will lead to re-assignment to Level 0." (My emphasis)
The irony of the latest set of headlines is that the level 1 wording was explicitly revised in 2005 to make clear that such asteroids are usually downgraded to level 0 with subsequent tracking and not worthy of public concern.
Indeed, in yesterday's ignored Nasa release, Yeomans went on to say, "This is a relatively new discovery. With more observations, I fully expect we will be able to significantly reduce, or rule out entirely, any impact probability for the foreseeable future."
Astronomers will now be looking back through archive sky images in case 2013 TV135 was spotted before but overlooked. They will also be tracking the asteroid whenever possible. By far the most likely outcome in the next few days or weeks is that 2013 TV135 will be downgraded to Level 0, meaning "no hazard".
However, that story – of human endeavour and professional conduct – won't make the headlines.
Stuart Clark is the author is Voyager: 101 Wonders Between Earth and the Edge of the Cosmos (Atlantic)
If it does, the reports say, it could create an explosion 50 times greater than the biggest nuclear bomb ever detonated. The unreported details, however, paint a rather different picture.
On 8 October 2013, astronomers at the Crimean Astrophysical Observatory in the Ukraine discovered an asteroid. Catalogued as 2013 TV135, it is just one of 10,332 near-Earth objects known to exist.
Astronomers tracked it over subsequent nights, piecing together its orbit. They realised that it had made a close pass to Earth on 16 September, drawing within 6.7 million kilometres of our planet.
Although that is more than 17 times the distance to the moon, any asteroid that can pass closer to Earth than 7.5 million kilometres is automatically dubbed "potentially hazardous" and listed by the International Astronomical Union on a webpage that is rather alarmingly called Dangerous.html.
Things got worse. Based on the preliminary orbit calculation, 2013 TV135 could find itself close to Earth again in 2032. In that year, uncertainties in the orbit mean that it has a 1-in-63,000 chance of hitting our planet. And the doomsday headlines were born.
Yesterday, Nasa rushed to issue "a reality check", in which Don Yeomans, the manager of Nasa's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California stated, "To put it another way, that puts the current probability of no impact in 2032 at about 99.998 percent."
It didn't calm the waters. Instead, the reports chose to highlight that 2013 TV135 had been given a rating of one out of ten on the Torino scale, which ranks the impact hazard associated with near-Earth objects.
As an implication of the danger, the reports point out that there is only one other level 1 asteroid currently known. That's true but it only tells half the story. Upon discovery, a couple of dozen other asteroids have been classed level 1 or more, only to be downgraded later.
The reason is that initially astronomers have very little information with which to calculate an orbit. So the possible path through space is highly uncertain. If Earth appears anywhere within that uncertain path, the asteroid is given a rating on the Torino Scale, usually level 1.
To highlight that this is entirely normal, the exact wording for a level 1 asteroid is: "A routine discovery in which a pass near Earth is predicted that poses no unusual level of danger. Current calculations show the chance of collision is extremely unlikely with no cause for public attention or public concern. New telescopic observations very likely will lead to re-assignment to Level 0." (My emphasis)
The irony of the latest set of headlines is that the level 1 wording was explicitly revised in 2005 to make clear that such asteroids are usually downgraded to level 0 with subsequent tracking and not worthy of public concern.
Indeed, in yesterday's ignored Nasa release, Yeomans went on to say, "This is a relatively new discovery. With more observations, I fully expect we will be able to significantly reduce, or rule out entirely, any impact probability for the foreseeable future."
Astronomers will now be looking back through archive sky images in case 2013 TV135 was spotted before but overlooked. They will also be tracking the asteroid whenever possible. By far the most likely outcome in the next few days or weeks is that 2013 TV135 will be downgraded to Level 0, meaning "no hazard".
However, that story – of human endeavour and professional conduct – won't make the headlines.
Stuart Clark is the author is Voyager: 101 Wonders Between Earth and the Edge of the Cosmos (Atlantic)
Asteroid 2013 TV135 – A Reality Check
Oct. 17, 2013
This diagram shows the orbit of asteroid 2013 TV135
(in blue), which has just a 1-in-63,000 chance of impacting Earth. Its risk to
Earth will likely be further downgraded as scientists continue their
investigations.
Image Credit:
NASA/JPL-Caltech
Image Token:
Feature Link:
Newly discovered asteroid 2013 TV135 made a close approach to Earth on Sept. 16, when it came within about 4.2 million miles (6.7 million kilometers). The asteroid is initially estimated to be about 1,300 feet (400 meters) in size and its orbit carries it as far out as about three quarters of the distance to Jupiter's orbit and as close to the sun as Earth's orbit. It was discovered on Oct. 8, 2013, by astronomers working at the Crimean Astrophysical Observatory in Ukraine. As of Oct. 14, asteroid 2013 TV135 is one of 10,332 near-Earth objects that have been discovered.
With only a week of observations for an orbital period that spans almost four years, its future orbital path is still quite uncertain, but this asteroid could be back in Earth’s neighborhood in 2032. However, NASA’s Near-Earth Object Program Office states the probability this asteroid could then impact Earth is only one in 63,000. The object should be easily observable in the coming months and once additional observations are provided to the Minor Planet Center in Cambridge, Mass., the initial orbit calculations will be improved and the most likely result will be a dramatic reduction, or complete elimination, of any risk of Earth impact.
"To put it another way, that puts the current probability of no impact in 2032 at about 99.998 percent," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. "This is a relatively new discovery. With more observations, I fully expect we will be able to significantly reduce, or rule out entirely, any impact probability for the foreseeable future."
NASA detects, tracks and characterizes asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and identifies their orbits to determine if any could be potentially hazardous to our planet.
JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.
More information about asteroids and near-Earth objects is at: http://www.jpl.nasa.gov/asteroidwatch .
D.C. Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle@jpl.nasa.gov
2013-300
http://www.nasa.gov/mission_pages/asteroids/news/asteroid20131017.html
Jet Propulsion Laboratory, Pasadena, Calif.
agle@jpl.nasa.gov
2013-300
http://www.nasa.gov/mission_pages/asteroids/news/asteroid20131017.html
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