[返回科技频道首页]·[所有跟帖]·[ 回复本帖 ] ·[热门原创] ·[繁體閱讀]·[版主管理]
NASA去年在太阳系外发现一颗奇异的行星
送交者: 大号蚂蚁[☆★★我佛慈悲★★☆] 于 2020-04-15 22:12 已读 2081 次  

大号蚂蚁的个人频道

NASA has found a strange alien planet sitting outside our solar system. The world is cool and small: two characteristics that make it a very strange thing indeed for scientists to find. Why is this unusual?

The planet mentioned in the news story is called HD 21749b, and it was discovered by NASA’s new TESS (Transiting Exoplanets Survey Satellite) mission. What makes it notable is a combination of factors. Any one of them alone would not be that big a deal, but the combination makes this planet quite significant. Breaking it down: 6park.com

HD 21749b is three times the diameter of Earth and 23 times the mass, so it’s more of a midsize planet than a small one. Planets of that size are not unusual, but the size and inferred density of HD 21749b place it right on the dividing line between rocky, Earthlike planets and slightly bigger, gassy worlds that resemble Neptune. Scientists are eager to understand why planets seem to fall strongly into one category or the other. 6park.com

There’s nothing particularly strange about the temperature of HD 21749b, either. Its “equilibrium temperature” is about 300 degrees F (and it could be warmer still if it has a heat-trapping atmosphere), so it’s not exactly cool by human standards. But it is relatively cool compared to many other known super-Earth and mini-Neptune planets. There is no equivalent planet in our solar system, and we don’t know much about what conditions might be like on such a world. Now we can find out! 6park.com

HD 21749b happens to be fairly nearby (53 light years away), and it transits its star, meaning that it appears to pass right in front of the star and cast a little shadow as seen from Earth. Watching how the star’s light passes through the planet’s atmosphere can reveal the composition of the planet, the layering of its atmosphere, and even the presence of clouds. Finding nearby transiting planets is the purpose of TESS. 6park.com

6park.com

Put those characteristics together and you can see why scientists are intrigued by HD 21749b. Calling it a “very strange thing,” as this news story does, is silly, however. We’ve found planets that orbit backwards, planets that are puffed like marshmallows, planets that may be made of diamond…I’d call those strange. A warm rocky planet with a thick atmosphere (a likely interpretation of HD 21749b), not so much.

In fact, what’s most interesting about HD 21749b is precisely that it is not strange! It’s just a little larger and hotter than Earth, making it a prime test subject. Truly Earthlike planets will be harder to study. This planet will offer a great learning experience in how to find and examine a true Earth twin. It will probably also teach us a lot about which kinds of worlds really could support life, and which ones turn out to be harsh and inhospitable on closer examination.


贴主:大号蚂蚁于2020_04_15 22:20:44编辑
喜欢大号蚂蚁朋友的这个贴子的话, 请点这里投票,“赞”助支持!
[举报反馈]·[ 大号蚂蚁的个人频道 ]·[-->>参与评论回复]·[用户前期主贴]·[手机扫描浏览分享]·[返回科技频道首页]
帖子内容是网友自行贴上分享,如果您认为其中内容违规或者侵犯了您的权益,请与我们联系,我们核实后会第一时间删除。

所有跟帖:        ( 主贴楼主有权删除不文明回复,拉黑不受欢迎的用户 )


    用户名:密码:[--注册ID--]

    标 题:

    粗体 斜体 下划线 居中 插入图片插入图片 插入Flash插入Flash动画


         图片上传  Youtube代码器  预览辅助

    打开微信,扫一扫[Scan QR Code]
    进入内容页点击屏幕右上分享按钮

    楼主本栏目热帖推荐:

    >>>>查看更多楼主社区动态...






    [ 留园条例 ] [ 广告服务 ] [ 联系我们 ] [ 个人帐户 ] [ 版主申请 ] [ Contact us ]