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天文学家运用哈勃太空望远镜，透过观测天王星极光的旋转运动测定其内部自转速率，精确度比过去的推算提升了一千倍。这项突破性的成果，为未来行星科学研究奠定了关键的新基准。行星的自转周期是理解其内部结构与磁场的重要基础，但对于像天王星这样遥远的天体而言，准确掌握其自转速率极具挑战性。为了解决这项难题，天文学家发展出一项崭新技术：透过观测天王星极光的旋转运动来推算其自转速率。这些极光是高能粒子流入天王星磁极区域，与上层大气互动后所产生的发光现象。研究团队分析了哈勃望远镜自 2011 年以来超过十年的紫外线极光观测资料，建立出磁场模型，并成功比对极光与磁极位置的时间变化，从而推算出天王星完整自转一圈的时间为 17 小时 14 分 52 秒，比 1986 年 NASA 航海家二号飞掠时的估计值多出 28 秒，精确度也提升了一千倍。 Nature Astronomy:A new rotation period and longitude system for Uranus 天文館:哈伯測量天王星自轉速率，精確度提升千倍
天文学家运用哈勃太空望远镜，透过观测天王星极光的旋转运动测定其内部自转速率，精确度比过去的推算提升了一千倍。这项突破性的成果，为未来行星科学研究奠定了关键的新基准。行星的自转周期是理解其内部结构与磁场的重要基础，但对于像天王星这样遥远的天体而言，准确掌握其自转速率极具挑战性。为了解决这项难题，天文学家发展出一项崭新技术：透过观测天王星极光的旋转运动来推算其自转速率。这些极光是高能粒子流入天王星磁极区域，与上层大气互动后所产生的发光现象。研究团队分析了哈勃望远镜自 2011 年以来超过十年的紫外线极光观测资料，建立出磁场模型，并成功比对极光与磁极位置的时间变化，从而推算出天王星完整自转一圈的时间为 17 小时 14 分 52 秒，比 1986 年 NASA 航海家二号飞掠时的估计值多出 28 秒，精确度也提升了一千倍。 Nature Astronomy:A new rotation period and longitude system for Uranus 天文館:哈伯測量天王星自轉速率，精確度提升千倍
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Telegram and Signal Havens for Right-Wing Extremists
Since the violent storming of Capitol Hill and subsequent ban of former U.S. President Donald Trump from Facebook and Twitter, the removal of Parler from Amazon’s servers, and the de-platforming of incendiary right-wing content, messaging services Telegram and Signal have seen a deluge of new users. In January alone, Telegram reported 90 million new accounts. Its founder, Pavel Durov, described this as “the largest digital migration in human history.” Signal reportedly doubled its user base to 40 million people and became the most downloaded app in 70 countries. The two services rely on encryption to protect the privacy of user communication, which has made them popular with protesters seeking to conceal their identities against repressive governments in places like Belarus, Hong Kong, and Iran. But the same encryption technology has also made them a favored communication tool for criminals and terrorist groups, including al Qaeda and the Islamic State.
How to Invest in Bitcoin?
Like a stock, you can buy and hold Bitcoin as an investment. You can even now do so in special retirement accounts called Bitcoin IRAs. No matter where you choose to hold your Bitcoin, people’s philosophies on how to invest it vary: Some buy and hold long term, some buy and aim to sell after a price rally, and others bet on its price decreasing. Bitcoin’s price over time has experienced big price swings, going as low as $5,165 and as high as $28,990 in 2020 alone. “I think in some places, people might be using Bitcoin to pay for things, but the truth is that it’s an asset that looks like it’s going to be increasing in value relatively quickly for some time,” Marquez says. “So why would you sell something that’s going to be worth so much more next year than it is today? The majority of people that hold it are long-term investors.”
