2024 年 4 月 6 日
解开星系M51
影像提供与版权:数据提供 -Hubble Heritage Project,解开影像 - Paul Howell
说明： 在这幅2005年哈伯太空望远镜拍摄的M51之再处理影像里，这个宏伟螺旋星系的螺旋臂，经过数位转置后加以拉直。M51是原始的"螺旋星云"之一，而它的螺旋臂和星系中心的距离，呈几何级数递增，故其螺旋臂可用名为对数螺线的数学曲线来描述。因此，把哈伯M51影像的像素相对星系中心之坐标取对数，就能把此星系的螺旋臂转置成这些对角直线。这幅转置后的影像，明确的指证这些螺旋臂，就是发生恒星诞生活动的位置，故散布著大量的粉红恒星形成区和泛蓝年轻星团。此外，位在影像顶端的伴星系NGC5195，看似改变了通过它前方的旋臂之轨迹，而其本身则几乎未受转置的影响。亦称为神奇螺旋的对数螺线，常出现在各种尺度的自然现象里。例如：对数螺线可用来描述台风、气泡室的次原子粒子迹线、及花椰菜。
With your “Archived Chats” folder finally hidden from view in the chat list area, if the other party decides to send you a new message, the conversation will pop up again in your regular chat feed. To ensure your conversation remains hidden, mute the conversation in question by following the below instructions.Find your “Archived Chats” folder. If you’ve hidden it from view on your mobile, swipe from the top of the app and release to bring back the folder. Long-tap on the conversation in question and select the “Sound” icon at the top. Select “Disable” to stop worrying the conversation will resurface in the app’s main area. On PC, tap on the hamburger menu in the upper-left corner. Select “Archived chats” at the top to get the conversation you hid. Select the chat in question, right-click on it and opt for the “Mute Notifications” option. Hit “Mute forever” or “Mute for…” and select a time frame that suits your needs.
With Telegram, you can send messages, photos, videos and files of any type (doc, zip, mp3, etc), as well as create groups for up to 200,000 people or channels for broadcasting to unlimited audiences. You can write to your phone contacts and find people by their usernames. As a result, Telegram is like SMS and email combined — and can take care of all your personal or business messaging needs. In addition to this, we support end-to-end encrypted voice calls.
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Telegram is for everyone who wants fast and reliable messaging and calls. Business users and small teams may like the large groups, usernames, desktop apps and powerful file sharing options. You can appoint admins with advanced tools to help these communities prosper in peace. Public groups can be joined by anyone and are powerful platforms for discussions and collecting feedback.In case you're more into pictures, Telegram has animated gif search, a state of the art photo editor, and an open sticker platform (find some cool stickers here or here). What's more, there is no need to worry about disk space on your device. With Telegram's cloud support and cache management options, Telegram can take up nearly zero space on your phone.
Unlike WhatsApp, Telegram is a cloud-based messenger with seamless sync. As a result, you can access your messages from several devices at once, including tablets and computers, and share an unlimited number of photos, videos and files (doc, zip, mp3, etc.) of up to 2 GB each. And if you don't want to store all that data on your device, you can always keep it in the cloud.Thanks to our multi-data center infrastructure and encryption, Telegram is faster and way more secure. On top of that, Telegram is free and will stay free — no ads, no subscription fees, forever.
Yes! Voice calls are currently available to users around the world.
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