双语阅读

"We haven't found them all."

“我们还没有全部找到。”

An asteroid in the glare from the sun.

Credit: DOE / FNAL / DECam / CTIO / NOIRLab / NSF / AURA / J. da Silva / Spaceengine

在耀眼的太阳光下，一颗小行星。

图片来源:DOE / FNAL / DECam / CTIO / NOIRLab / NSF / AURA / J. da Silva / Spaceengine

Astronomers are vigilantly scanning the skies for asteroids that veer into Earth's solar system neighborhood. But, some are hidden.

天文学家正在警惕地扫描天空，寻找转向地球太阳系附近的小行星。但是，有些是隐藏的。

Most asteroids — leftover rubble from our solar system's formation some 4.6 billion years ago — orbit the sun between Mars and Jupiter. Millions exist out there. But in the inner solar system, asteroids are obscured by the blinding glare from the sun.

大多数小行星——大约46亿年前太阳系形成时留下的残骸——在火星和木星之间绕太阳运行。数以百万计的人生活在那里。但在太阳系内部，小行星会被太阳耀眼的强光遮蔽。

Now, a new survey of space rocks in regions around the orbits of Venus and Mercury have spotted sizable asteroids in this elusive zone of space. One is nearly a mile wide, the type of "planet-killer" rock that would decimate life on Earth. Fortunately, these rocks don't currently pose any danger to our planet, nor will they for the foreseeable future — though over centuries, or much longer, one of the asteroids' orbits may change and potentially pose a threat.

现在，对金星和水星轨道附近区域的太空岩石进行的一项新的调查发现，在这一难以捉摸的太空地带有相当大的小行星。其中一块近1英里宽，是一种“行星杀手”岩石，可以毁灭地球上的生命。幸运的是，这些岩石目前不会对我们的星球构成任何威胁，在可预见的未来也不会——尽管在几个世纪或更长时间内，其中一颗小行星的轨道可能会改变，并可能构成威胁。

To find these rocks, scientists must scour the sky at twilight (at dawn and dusk). They get just 10 minutes. At dusk, for example, they have the narrow viewing time after the sun has dimmed, but before this sun-facing sky disappears under the horizon.

为了找到这些岩石，科学家们必须在黄昏时分(黎明和黄昏)搜寻天空。他们只有10分钟的时间。例如，在黄昏，他们只有很短的观看时间，在太阳变暗之后，但在这面朝太阳的天空消失在地平线之下之前。

"You don't have a lot of time," Scott Sheppard, an astronomer at the Carnegie Institution for Science, told Mashable. Sheppard led the new research about these twilight asteroid discoveries, which was recently published in The Astronomical Journal.

“你没有很多时间，”卡内基科学研究所的天文学家斯科特·谢泼德告诉Mashable。谢帕德领导了关于这些黄昏小行星发现的新研究，该研究最近发表在《天文学杂志》上。

A powerful telescope is needed to find these rocks. At 7,200 feet up in Chile, scientists attached a camera, called the Dark Energy Camera, to a 4-meter (13-foot) wide telescope. It's the biggest camera on a telescope of such a large size, explained Sheppard, and it can view great swathes of the sky. (Previously, astronomers used it to look for truly deep space objects, beyond Pluto.) In just one image, scientists can view a region of sky encompassing about 11 full moons, as opposed to their previous twilight-viewing capabilities of around two full moons.

要找到这些岩石，需要一台功能强大的望远镜。在智利7200英尺的高空，科学家们在一个4米(13英尺)宽的望远镜上安装了一个名为“暗能量相机”的相机。谢帕德解释说，这是如此大尺寸的望远镜中最大的相机，它可以看到大片的天空。(此前，天文学家用它来寻找冥王星以外的真正深空天体。)仅在一张图像中，科学家就可以看到一个包含大约11个满月的天空区域，而不是以前观测大约两个满月的黄昏能力。

So far, they've spotted three "near-Earth asteroids," or NEAs. It doesn't actually mean they're literally "near" Earth, like the moon. It means they're relatively near — because space is huge. These are rocks whose orbit can at times pass within some 30 million miles of Earth's orbit around the sun (not necessarily Earth itself), explains NASA.

到目前为止，他们已经发现了三颗“近地小行星”(NEAs)。这并不意味着它们真的像月球一样“靠近”地球。这意味着它们相对较近——因为空间很大。美国国家航空航天局解释说，这些岩石的轨道有时可以在地球绕太阳轨道约3000万英里(不一定是地球本身)的范围内经过。

The Víctor M. Blanco 4-meter Telescope is used to detect asteroids at twilight.

Credit: CTIO / NOIRLab / NSF/ AURA / D. Munizaga

Víctor M. Blanco 4米望远镜用于探测黄昏时的小行星。

来源:CTIO / NOIRLab / NSF/ AURA / D. Munizaga

The designation also doesn't mean they're a threat. No known asteroid over 460 feet across will threaten Earth in the next century or so. Crucially, the chances of a major impact in our lifetimes is, as far as we know, extremely small, Eric Christensen, the director of the near asteroid-seeking Catalina Sky Survey in Arizona, told Mashable earlier this year. As Mashable reported:

这一称号也不意味着它们是威胁。下个世纪左右，没有直径超过460英尺的小行星会威胁到地球。关键是，据我们所知，在我们的一生中发生重大撞击的可能性非常小，埃里克·克里斯滕森(Eric Christensen)今年早些时候对Mashable说，他是亚利桑那州寻找近小行星的卡特琳娜巡天计划的负责人。据Mashable报道:

Impacts by objects around 460 feet in diameter occur every 10,000 to 20,000 years, and a "dinosaur-killing" impact from a rock perhaps a half-mile across or larger happens on 100-million-year timescales. Though something smaller could certainly surprise us, like the unexpected football-field-sized asteroid that swung just 40,000 miles from Earth in 2019. That's why watching is critical. We might not be able to nudge an approaching rock away from our planet — that's an ambitious space endeavor that takes years of planning — but we can prepare for an impact and move people out of the way.

直径约460英尺的物体的撞击每1万到2万年发生一次，直径约半英里或更大的岩石的“恐龙灭绝”撞击发生在1亿年的时间尺度上。不过，更小的东西肯定会让我们惊讶，比如2019年，一颗足球场大小的小行星出乎意料地距离地球只有4万英里。这就是为什么观察至关重要。我们可能无法将一块接近地球的岩石推离我们的星球——这是一项需要数年规划的雄心勃勃的太空努力——但我们可以为撞击做好准备，让人们离开。

Two of the three newly revealed asteroids, however, are indeed of "planet-killer" size. They likely came from the main asteroid belt, where most asteroids live. The near-Earth asteroids are on eccentric orbits that are stable for a million years or so, explained Sheppard. But as they interact with the gravity of nearby planets, their orbits can shift. Eventually, they'll most likely be ejected to the outer solar system.

然而，在新发现的三颗小行星中，有两颗确实具有“行星杀手”的大小。它们很可能来自主小行星带，大多数小行星都生活在主小行星带。Sheppard解释说，近地小行星在偏心轨道上运行，可以稳定100万年左右。但当它们与附近行星的引力相互作用时，它们的轨道会发生变化。最终，它们极有可能被喷射到外太阳系。

"There's no danger."

“没有危险。”

The largest of these objects, 2022 AP7, is expected to pass extremely close to Venus — within a few thousand miles — in the next 1,000 years. It could potentially hit Venus, though that probability remains low. "It's unlikely to happen, but you never know," noted Sheppard. One day in the future, 2022 AP7 may also travel into the path of Earth's orbit, too. That's why this colossal rock also earns the designation of "Potentially Hazardous Asteroid" (meaning it's bigger than 460 feet wide and its orbit passes within 4.6 million miles of Earth's orbit, or path, around the sun.)

这些天体中最大的一个，2022 AP7，预计将在未来1000年里非常接近金星——在几千英里之内。它有可能撞击金星，尽管这种可能性仍然很低。“这不大可能发生，但你永远不知道，”谢帕德说。在未来的某一天，2022年的AP7也可能会进入地球轨道。这就是为什么这颗巨大的岩石还获得了“潜在危险小行星”的称号(这意味着它的宽度超过460英尺，其轨道在地球绕太阳轨道460万英里的范围内。)

But that day, if it ever occurs, isn't any time soon. That possibility is on the order of centuries or millennia away. "There's no danger," Sheppard emphasized. "There are no interactions with Earth in the foreseeable future."

但即使那一天真的到来，也不会很快。这种可能性在几个世纪或几千年后才会出现。“没有危险，”谢帕德强调说。“在可预见的未来，它不会与地球发生相互作用。”

Unfortunately, this reality won't stop some news sites from publishing misleading and scaremongering headlines about the newly found space rocks, such as, I kid you not: "Huge ‘planet killer’ asteroid discovered – and it’s heading our way." That's rubbish. In fact, any time a news site or entity on social media warns of an asteroid "headed our way," ignore it. These egregious efforts are just seeking your clicks. These dubious stories are published weekly. Yet, NASA has literally never even issued a warning about a menacing, incoming asteroid. If a space rock ever does become a threat, NASA, the White House, and political leaders will be involved.

不幸的是，这一现实并不能阻止一些新闻网站发布关于新发现的太空岩石的误导性和耸人听闻的标题，比如，我不骗你:“发现了巨大的‘星球杀手’小行星——它正向我们飞来。”这是垃圾。事实上，每当新闻网站或社交媒体上的实体警告有一颗小行星“朝我们飞来”时，请忽略它。这些过分的努力只是为了获得你的点击量。这些可疑的故事每周都发表。然而，美国国家航空航天局甚至从来没有发布过关于小行星威胁性的警告。如果太空岩石真的成为威胁，NASA、白宫和政治领导人都会参与进来。

To protect humanity from asteroid strikes, astronomers and planetary defense experts want to know where most of the near-Earth asteroids are headed. If one is projected to one day — perhaps in decades or centuries — come unsettlingly close to Earth, then we can do something about it. "You need to know what's coming, when it's coming, and how hard it's going to hit," Christensen told Mashable. Even a smaller asteroid, some 100- to 170-feet across, could destroy a place like Kansas City, home to half a million people. So the surveys for rocks large and "small" are vital.

为了保护人类免受小行星撞击，天文学家和行星防御专家想知道大多数近地小行星的去向。如果有一天——也许在几十年或几个世纪之后——有一颗小行星会令人不安地接近地球，那么我们就可以为此做点什么。克里斯滕森对Mashable说:“你需要知道会发生什么，什么时候会发生，以及它会有多猛烈。”即使是一颗直径约100至170英尺的小小行星，也能摧毁像堪萨斯城这样有50万人口的地方。因此，对大小岩石的调查至关重要。

A graph showing near-Earth asteroid discoveries

Credit: NASA / Center for Near Earth Object Studies

显示在地球附近发现的小行星的图表

图片来源:NASA /近地天体研究中心

With enough time (years), NASA recently has proven that we have the ability to slightly change an asteroid's trajectory, and thereby save Earth from a potential disaster. The space agency recently crashed a vending machine-sized spacecraft in an asteroid the size of a stadium. The sci-fi-like endeavor, called DART, or Double Asteroid Redirection Test, was a successful mission to see how civilization could alter the path of a menacing asteroid, should one be on a collision course with our planet.

有了足够的时间(数年)，NASA最近证明了我们有能力轻微改变小行星的轨道，从而使地球免于潜在的灾难。美国宇航局最近在一颗体育场大小的小行星上撞毁了一架自动贩卖机大小的航天器。这一类似科幻小说的尝试被称为DART(双小行星重定向测试)，是一项成功的任务，旨在观察文明如何改变一颗威胁地球的小行星的路径，如果一颗小行星与我们的星球发生碰撞的话。

Of the largest class of near-Earth space rocks — those 1 km wide or larger — astronomers estimate they've found around 95 percent of them. They are non-threatening. As of November 2022, they've located 857. That means there are some 20 to 50 of those "planet-killer" asteroids still out there. Astronomers would like to find more, just to be safe. That means peering into the twilight sky.

在最大的一类近地太空岩石中——那些1公里宽或更大的——天文学家估计他们已经发现了大约95%的近地太空岩石。它们没有威胁性。截至2022年11月，他们已经找到了857个。这意味着还有20到50颗这样的“行星杀手”小行星存在。为了安全起见，天文学家希望能找到更多。这意味着凝视黄昏的天空。

"We haven't found them all," Sheppard said.

“我们还没有找到所有的小行星，”谢帕德说。