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天文学家发现“灾难性变量”系统：证实了几十年前的预测_我的网站

一 |     President Joe Biden left Israel on Wednesday after a high-stakes diplomatic mission to show solidarity with the U.S. ally, but also securing Israel's commitment to allow humanitarian aid into Gaza and delivering an in-person warning to show restraint."I come to Israel with a simple message: You are not alone," Biden said as he spoke in Tel Aviv.The president compared the atrocities unleashed by Hamas to 9/11, stating Americans understand Israel's demands for justice.But he urged the nation not to be consumed by their outrage, asking officials to be deliberate with their objectives and ask the hard questions as they continue to respond to the terror attacks with airstrikes and a possible ground offensive."After 9/11, we were enraged in the United States. While we sought justice and got justice, we also made mistakes," Biden said.The remarks came off the heels of meetings with Israeli Prime Minister Benjamin Netanyahu and his war cabinet as well as first responders and other Israelis affected by the violence that's unfolded since Oct. 7.Biden achieved one key objective of the trip, as Israel agreed to allow limited quantities of aid to begin to flow into Gaza from Egypt after blocking the Rafah border crossing for more than a week, leaving virtually no options in or out of Gaza."The people of Gaza need food, water, medicine, shelter," Biden said, as he stressed Hamas "does not represent the Palestinian people" and that civilians are suffering under their rule.Biden said the understanding is that the aid will be subject to inspections to ensure it is going to civilians, not Hamas."Let me be clear: If Hamas diverts or steals the assistance, they will have demonstrated once again that they have no concern for the welfare of the Palestinian people and it will end as a practical matter, it will stop the international community from being able to provide this aid," Biden said.In addition, Biden announced $100 million in new U.S. funding for humanitarian assistance in both Gaza and the West Bank to support the more than million people displaced by the conflict.Biden stepped off Air Force One at Ben Gurion Airport in Tel Aviv at about 10:50 a.m. local time. Netanyahu was waiting for Biden and the two leaders, whose relationship spans decades, shared words before exiting in convoys.Amid Biden's words of caution and restraint -- telling Israel they, as a democracy, live by the "rule of law" not the rule of terrorists -- Netanyahu only went so far as to say Israel will continue working with the U.S. to "assure that the minimum requirements are met" as well as efforts to get hostages out of Hamas control."As we proceed in this war, Israel will do everything it can to keep civilians out of harm's way," Netanyahu said. "We've asked them and we will continue to ask them to move to safer areas."Biden's visit, a physically and politically perilous one, comes one day after a deadly blast at a Gaza hospital rocked the area.Hamas blamed the incident on the Israeli Defense Forces while Israel presented materials they say prove it was a failed rocket launch by Palestinian Islamic Jihad.Biden supported Israel's claim that militants in Gaza were responsible for the blast. He told Netanyahu that it "appears it was done by the other team, not you."Later, when asked by a reporter what made him confident the Israelis weren't behind the hospital attack, Biden said it was "the data I was shown by my Defense Department."Biden was set to visit Jordan and meet with Arab leaders there but that summit was canceled after the hospital blast.

After his meetings with Israeli officials, Biden took time to speak with first responders, families of victims and hostages and others affected by the Hamas attacks.The meetings were emotional, as one first responder recounted the atrocities inflicted on women and children.One pediatric physician who moved from New York to Israel years ago told Biden "never could have prepared" in her life for the mass casualty event she experienced following the attacks. Biden shared with her the personal story of when his wife and daughter were killed in a car accident and told her he understands physicians and nurses "make a gigantic difference."。    需要说明的是，这并不是科学记者的夸张之词。天文学家称这些系统为灾难性变星是一个恰当的描述。这个术语描述了一个白矮星和一个次级“正常”恒星的配对，前者是一颗曾经强大的恒星的密集残余物，后者跟太阳类似但质量可能较小。在这对组合的紧密轨道上，白矮星由于其极端的引力而从较大的恒星上吸走恒星物质。周三发表在《自然》上的新灾难性变量的发现其特点是一颗大小为太阳1/100的白矮星和一颗更大的恒星--约是太阳质量的10%并挤在一个木星大小的球体中。

二 | 这对恒星距离地球约3000光年，其被标记为ZTF J1813+4251。它是在兹威基瞬变设施拍摄的图像中被发现，这是一项广域调查，其使用加州帕洛玛天文台的一台望远镜并依次拍摄数百张天空图像。

三 | 兹威克瞬变设施目录使天文学家能寻找恒星亮度的快速变化。

四 | 这就是研究人员发现这对奇特的星体的方式。“这是一个特殊的系统，”麻省理工学院的天体物理学家Kevin Burdge说道。他指出，这是已知的行为最优美的灾难性变数之一。

五 | Burdge和他的同事们搜索了茨威基的数据以试图在深黑的太空中找到灯塔。他们希望看到有规律的眨眼特征--Burdge通常在寻找快速的眨眼，这是因为它们往往是一对恒星快速运行的信号。研究小组看到ZTF J1813+4251每51分钟闪烁一次。据悉，这是其中一颗恒星从另一颗恒星前面经过并使其光线变暗。闪烁的时间跟迄今为止发现的灾难性变星的最短轨道相吻合。通过用夏威夷和西班牙的其他望远镜以及天基望远镜进行观测，这使得研究人员对恒星变得更加集中，并能更准确地测量它发出的光线。不过这引发了一个难题。Burdge在一份新闻稿中指出：“有一颗恒星看起来像太阳，但是太阳无法进入一个短于8小时的轨道。”太阳的质量使它无法拥有如此紧密的轨道。那么为什么这颗木星大小的恒星会这样做呢？Burdge和研究小组已经确定的解释是，这颗白矮星一直在吞噬其伙伴星的一大块氢。这留下了一个更密集的氦气核心，而这有助于稳定紧密的轨道。

六 | 简而言之，研究小组是在这一过程的中间阶段观察这对恒星的，当时白矮星已经剥去了大部分的氢。剥离后的白矮星留下了一个吸积盘，它像土星环一样围绕着核心。“这是一个罕见的案例，我们在从氢到氦的吸积过程中抓住了其中的一个系统，”Burdge说道。在12亿颗恒星中，该算法挑出了我们迄今发现的最有趣的灾难性变数之一。这一幸运的发现有助于支持早先提出的关于大灾变体过渡到超短轨道的理论，该理论是在近四十年前提出的--现在我们知道这确实发生了。该小组还进行了模拟以确定ZTF J1813+4251的最终命运。他们预测，在约7000万年后，这对天体将更快地围绕对方运行，每18分钟做一次完整的循环。尽管人们不会看到它，但一旦激光干涉仪空间天线(LISA)在2030年代末的某个时候进入轨道，那么研究人员将能更详细地研究这个灾难性的变量。这一系列卫星将被用来探测引力波--这些恒星舞伴将产生引力波。

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