系外行星我们适合在哪里

It has only been about 30 years since the first planet outside our own solar system, an exoplanet, was confirmed. The chronology of exoplanet discovery is quite complex due to the fact that earlier observations, one as early as 1917, were not initially recognized as evidence of an exoplanet.

距太阳系外的第一个行星被确认是距我们只有30年的时间。 系外行星发现的时间顺序非常复杂，原因是早在1917年的早期观测就没有被最初认为是系外行星的证据。

After a period of Earth-based and Hubble telescope discoveries, a space telescope, named Kepler, dedicated to the task of finding exoplanets was launched in 2009. Pointed permanently to just a tiny part of the night sky, it patiently recorded light coming from over 500,000 stars for several years.

经过一段时间的地球和哈勃望远镜发现后，2009年发射了一个名为开普勒的太空望远镜，专门用于寻找系外行星。它永久地指向夜空的一小部分，耐心地记录了来自500,000星，持续数年。

Photo by Greg Rakozy on Unsplash Greg Rakozy在 Unsplash上 拍摄的照片

During its roughly 10 year mission, it detected over 2,600 new exoplanets. That, together with other discoveries, brings the total of known exoplanets to a little over 4,000. And many of these exoplanets have estimates for their orbital period, their mass, their radius, and so on. In this post, I am focussing on their masses and radii and comparing them to the planets in our solar system.

在大约10年的飞行任务中，它发现了2600多颗新系外行星。 这与其他发现一起，使已知系外行星总数增加到4,000多一点。 许多此类系外行星都对其轨道周期，质量，半径等进行了估算。 在这篇文章中，我将重点关注它们的质量和半径，并将它们与我们太阳系中的行星进行比较。

获取系外行星数据 (Obtaining Exoplanet Data)

In the Wolfram Language, these exoplanets are directly accessible from the programmatic interface to Wolfram Knowledgebase. In the notebook interface, you can access any entity, not just exoplanets, with a nifty user interface:

在Wolfram语言中，可以从Wolfram知识库的程序界面直接访问这些系外行星。 在笔记本界面中，您可以使用漂亮的用户界面访问任何实体，而不仅是系外行星：

(image by author) (作者提供的图片)

The final result above can also be represented in a plain-text code form. They are exactly the same thing:

上面的最终结果也可以用纯文本代码形式表示。 它们是完全一样的：

EntityClass["Exoplanet", All]

We can obtain the masses and radii for each planet with a simple query:

我们可以通过简单的查询来获取每个行星的质量和半径：

data = ExoplanetData[ EntityClass["Exoplanet", All], { EntityProperty["Exoplanet", "Mass", {"Uncertainty" -> "Around"}], EntityProperty["Exoplanet", "Radius", {"Uncertainty" -> "Around"}]}, "EntityAssociation"]

Many exoplanets do not have an estimate for their mass and/or radius, and the ones that do often have significant uncertainties attached to them. A random sample of ten rows of the data shows what the typical situation looks like:

许多系外行星无法估计其质量和/或半径，而确实存在着很大的不确定性。 十行数据的随机样本显示了典型情况：

(image by author) (作者提供的图片)

After filtering out the cases with either missing mass or radius, we get a nice clean dataset (another random sample of ten rows is shown):

在过滤掉质量或半径缺失的情况后，我们得到了一个很好的干净数据集(显示了另一个随机的十行样本)：

(image by author) (作者提供的图片)

绘制数据 (Plotting the Data)

It is now quite easy to plot the mass versus the radius for each exoplanet. The extra thin vertical and horizontal lines indicate the uncertainty for each exoplanet:

现在非常容易绘制每个系外行星的质量与半径的关系图。 细细的垂直和水平线表示每个系外行星的不确定性：

(image by author) (作者提供的图片)

It is not unsurprising to see a large number of bigger exoplanets. Bigger planets are easier to spot and so more of them have been detected.

看到大量更大的系外行星并不奇怪。 较大的行星更容易发现，因此已经发现了更多的行星。

To compare these exoplanets with the planets in our solar system, we need to get them, and their masses and radii, first:

为了将这些系外行星与我们太阳系中的行星进行比较，我们需要首先获取它们以及它们的质量和半径：

EntityValue[ EntityClass["Planet", All], {"Mass", "Radius"}, "EntityAssociation"]

Using the additional data, we can now repeat the same plot but with the solar system planets included:

使用其他数据，我们现在可以重复相同的图，但其中包括太阳系行星：

(image by author) (作者提供的图片)

This is quite interesting. It shows that there are quite a few exoplanets that are even bigger than Jupiter. There is an upper limit of course because at some size a very large planet will become a very small star.

这很有趣。 它表明有许多系外行星甚至比木星还要大。 当然有一个上限，因为在某种尺寸下，一个非常大的行星将变成一个非常小的恒星。

On the other end of the exoplanet spectrum, it is clear we have not found many very small planets. Even Mars sits outside the main cluster of detected exoplanets. Hopefully one day we will find lots of those too!

在系外行星光谱的另一端，很明显我们还没有发现很多非常小的行星。 甚至火星也位于探测到的系外行星的主要星系之外。 希望有一天我们也能找到很多！

NASA (public domain) NASA (公共领域)

The full Wolfram notebook with code is available online here.

完整的Wolfram笔记本和代码可在此处在线获得。

翻译自: https://towardsdatascience.com/exoplanets-where-do-we-fit-in-8f21b06d33fe

相关资源：太阳系外行星作为改变引力的探测器