小行星就要撞地球了，该逃的逃，该散的散吧。sorry，看错了，2135年的事

[chicago666]

NASA boosts impact risk from 'potentially hazardous' asteroid Bennu​

Scott Sutherland
Meteorologist/Science Writer
While the chances are still extremely low, new findings from the OSIRIS-REx mission have made an impact with Bennu slightly more likely.
Potentially hazardous asteroid Bennu just became slightly more potentially dangerous.
Over a century from now, in 2135, a half-kilometre-wide asteroid named 101955 Bennu will pass between the Earth and the Moon. While there is absolutely no chance of an impact with Bennu at that time, the close encounter throws uncertainty into the predictions. As a result, there's no saying for sure that Earth will be safe from Bennu afterward.
Before NASA sent their OSIRIS-REx spacecraft to Bennu, astronomers tracked asteroid Bennu using telescopes. Their observations gave us very accurate calculations of Bennu's orbit. The relatively close passes of Bennu in 1999, 2005 and 2011 helped with this. Although it was officially classified as a "Potentially Hazardous Asteroid" (PHA), NASA could rule out any possibility of a Bennu impact for the next 100+ years.
However, the September 2135 encounter added an extra complication. The asteroid comes very close to Earth at that time. On September 24 of that year, its absolute minimum distance could be around 110,000 km from the planet's surface or less than one-third the distance to the Moon. As it flies past, it will encounter one of several 'gravitational keyholes'. As it passes through one of these tiny points in space, Earth's gravity will tug on the asteroid and alter its orbit around the Sun.

This screenshot of an animation used during the NASA press briefing on Wednesday, August 11, 2021, shows the potential paths of Bennu during the 2135 flyby, based on the most up-to-date telescope observations, with a separate 'gravitational keyhole' for each path. Credit: NASA/Goddard
Even with the carefully plotted orbit of Bennu, the minor uncertainties made it challenging to tell which 'keyhole' it would pass through during that 2135 flyby. Thus, there was no way to know with any certainty which orbit it would end up on afterward.
This was of great concern to scientists because it introduced over 150 possible impacts, with a cumulative 1 in 2,700 impact chance between 2135 and 2300. The most likely impact would be on September 24, 2182.

The effects of one particular 'gravitational keyhole' could have disastrous results in 2182. Credit: NASA/Goddard
With OSIRIS-REx following along with the asteroid for over two years, though, it gave scientists an unprecedented chance to closely track the influence of the Yarkovsky effect.
The Yarkovsky effect is a tiny, constant 'push' that an asteroid receives as it radiates heat into space.
Watch below: How the Sun pushes asteroids around the solar system
According to Davide Farnocchia from the Center for Near Earth Object Studies (CNEOS) at NASA's Jet Propulsion Lab, who is the lead author of a new study published this week, the force of this 'push' on Bennu is equivalent to about the weight of three grapes.
"Think about that, just three grapes," Farnocchia said in a NASA teleconference on Wednesday. "Because this acceleration is persistent, its effect builds up over time, and it becomes very significant by the time we get to 2135."
"The OSIRIS-REx data give us so much more precise information, we can test the limits of our models and calculate the future trajectory of Bennu to a very high degree of certainty through 2135," Farnocchia said in a NASA press release. "We've never modelled an asteroid's trajectory to this precision before."
Based on their study of the Yarkovsky effect on Bennu, Farnocchia and his colleagues calculated an updated cumulative probability of a Bennu impact between 2135 and 2200. Instead of 1 in 2,700, the chance is now just 1 in 1,750. The individual chance of an impact on September 24, 2182, is now 1 in 2,700.
It should be noted that these probabilities are tiny.
A 1 in 1,750 chance is equal to a 0.057 per cent impact probability, while 1 in 2,700 is equivalent to 0.037 per cent. That means there's over a 99.94 per cent chance that Bennu will miss Earth on all the potential encounters it has towards the end of the 22nd century. Specifically for September 2182, there's a 99.96 per cent chance of a miss.
During their research, Farnocchia and the others accounted for every conceivable force that could affect Bennu's orbit. They even considered whether the Touch-and-Go (TAG) maneuver that netted NASA a sample of the asteroid was enough to alter its trajectory.
Watch below: NASA's OSIRIS-REx tags asteroid Bennu
"The force exerted on Bennu's surface during the TAG event were tiny even in comparison to the effects of other small forces considered," Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center, said in the press release. "TAG did not alter Bennu's likelihood of impacting Earth."
The next steps in determining Bennu's true potential as a threat to Earth will come in 2023 and 2037.
In 2023, OSIRIS-REx will swing past Earth. On its way past, it will drop off the sample it collected from Bennu's surface back in the Fall of 2020. As scientists examine these samples in the laboratory, we will learn more about Bennu's composition. This might provide information about how we could deflect such an asteroid on an impact trajectory.
In 2037, Bennu will be making its next close (but safe) flyby past Earth. During this pass, radio telescopes can gather radar data on the asteroid. These readings will help confirm the calculations made based on OSIRIS-REx's data and give us an even better estimate of its exact path for that 2135 encounter.

 

[chicago666]

美国宇航局增加了来自“潜在危险”小行星本努的撞击风险

斯科特·萨瑟兰
气象学家/科学作家
虽然可能性仍然极低，但 OSIRIS-REx 任务的新发现对 Bennu 产生的影响略有增加。


具有潜在危险的小行星 Bennu 只是变得更加危险。

一个多世纪后的 2135 年，一颗名为 101955 Bennu 的半公里宽的小行星将在地球和月球之间经过。 虽然当时绝对不可能与 Bennu 产生影响，但近距离接触给预测带来了不确定性。 因此，没有人可以肯定地说，地球以后会不会受到 Bennu 的伤害。

在 NASA 将他们的 OSIRIS-REx 航天器发送到 Bennu 之前，天文学家使用望远镜跟踪了小行星 Bennu。 他们的观察为我们提供了对 Bennu 轨道的非常准确的计算。 本努在 1999 年、2005 年和 2011 年相对接近的传球对此有所帮助。 尽管它被官方归类为“潜在危险小行星”（PHA），但 NASA 可以排除在未来 100 多年内发生本努撞击的任何可能性。

然而，2135 年 9 月的遭遇增加了额外的复杂性。 当时这颗小行星离地球非常近。 在那年的 9 月 24 日，它的绝对最小距离可能是距地球表面约 110,000 公里，或者不到到月球距离的三分之一。 当它飞过时，它会遇到几个“引力锁孔”之一。 当它穿过太空中的这些微小点之一时，地球的引力将牵引小行星并改变其绕太阳运行的轨道。


在 2021 年 8 月 11 日星期三举行的 NASA 新闻发布会上使用的动画截图显示了 Bennu 在 2135 飞越期间的潜在路径，基于最新的望远镜观测，带有单独的“引力锁孔”，用于 每条路径。 图片来源：美国宇航局/戈达德

即使仔细绘制了 Bennu 的轨道，微小的不确定性也使得判断它在 2135 年飞越期间将通过哪个“钥匙孔”具有挑战性。 因此，没有办法确切地知道它之后会在哪个轨道上结束。

这引起了科学家们的极大关注，因为它引入了 150 多种可能的影响，在 2135 年到 2300 年之间，累积的影响几率为 2,700 分之一。最有可能的影响发生在 2182 年 9 月 24 日。


一个特殊的“引力锁孔”的影响可能会在 2182 年造成灾难性的后果。图片来源：NASA/Goddard

然而，随着 OSIRIS-REx 跟随这颗小行星两年多的时间，它给了科学家一个前所未有的机会来密切跟踪 Yarkovsky 效应的影响。

Yarkovsky 效应是小行星在向太空辐射热量时接收到的微小而持续的“推力”。

观看下方：太阳如何推动小行星环绕太阳系


美国宇航局喷气推进实验室近地天体研究中心 (CNEOS) 的戴维德·法诺基亚 (Davide Farnocchia) 是本周发表的一项新研究的主要作者，他表示，这种对 Bennu 的“推动”力大约相当于 三个葡萄。

“想想看，只有三颗葡萄，”法诺基亚在周三的 NASA 电话会议上说。 “因为这种加速是持久的，它的影响会随着时间的推移而增强，当我们到达 2135 年时，它变得非常重要。”

“OSIRIS-REx 数据为我们提供了更精确的信息，我们可以测试我们模型的极限，并以非常高的确定性计算 Bennu 的未来轨迹到 2135 年，”法诺基亚在 NASA 的一份新闻稿中说。 “我们以前从未将小行星的轨迹模拟到这种精度。”

根据对 Bennu 的 Yarkovsky 效应的研究，Farnocchia 和他的同事计算了 2135 年到 2200 年之间 Bennu 撞击的更新累积概率。而不是 2,700 分之一，现在只有 1,750 分之一。 2182 年 9 月 24 日发生影响的个人几率现在是 2,700 分之一。

应该指出的是，这些概率很小。

1,750 分之一的机会等于 0.057% 的影响概率，而 2,700 分之一等于 0.037%。 这意味着 Bennu 有超过 99.94% 的可能性会在接近 22 世纪末的所有潜在遭遇中错过地球。 特别是对于 2182 年 9 月，有 99.96% 的机会错过。

在他们的研究中，法诺基亚和其他人考虑了可能影响本努轨道的所有可能的力量。 他们甚至考虑让 NASA 获取小行星样本的 Touch-and-Go (TAG) 机动是否足以改变其轨迹。

观看下方：美国宇航局的 OSIRIS-REx 标记小行星 Bennu


美国宇航局戈达德太空飞行中心的 OSIRIS-REx 项目经理 Rich Burns 在新闻稿中说：“即使与考虑的其他小力量的影响相比，在 TAG 事件期间施加在 Bennu 表面的力量也很小。” “TAG 并没有改变 Bennu 撞击地球的可能性。”

确定 Bennu 对地球构成威胁的真正潜力的下一步将在 2023 年和 2037 年进行。

2023 年，OSIRIS-REx 将掠过地球。 在经过的路上，它将在 2020 年秋季从 Bennu 表面收集的样本掉落。当科学家在实验室检查这些样本时，我们将更多地了解 Bennu 的成分。 这可能会提供有关我们如何在撞击轨迹上偏转这样一颗小行星的信息。

2037 年，Bennu 将进行下一次近距离（但安全）飞越地球。 在此过程中，射电望远镜可以收集小行星的雷达数据。 这些读数将有助于确认基于 OSIRIS-REx 数据所做的计算，并让我们更好地估计其在 2135 年遭遇的确切路径。

 

[chicago666]

2135年，那个时候坛子里所有人都玩完了，好可怕。

 

[zeus190]

我孙子表示毫无压力。

 

[mass]

半公里宽, 2134年核平了丫的。