第290集：失败的恒星

本集《天文学播客》由斯威本大学在线天文学项目赞助，这是全球运行时间最长的在线天文学学位课程。

This episode of Astronomy Cast is brought to you by Swinburne Astronomy Online, the world's longest running online astronomy degree program.

欲了解更多信息，请访问 astronomy.swin.edu.au。

Visit astronomy.swin.edu.au for more information.

《天文学播客》第290期，2013年1月21日星期一，主题：失败的恒星。

Astronomy Cast, episode 290 for Monday, 01/21/2013, failed stars.

欢迎收听《天文学播客》，这是我们每周基于事实的宇宙探索之旅，帮助您不仅了解我们知道了什么，更了解我们是如何知道这些的。

Welcome to Astronomy Cast, our weekly facts based journey through the cosmos where we help you understand not only what we know, but how we know what we know.

我的名字是弗雷泽·凯恩。

My name is Fraser Cain.

我是《今日宇宙》的出版人，和我一起的是帕梅拉·盖伊博士，她是南伊利诺伊大学爱德华兹维尔分校的教授，也是CosmoQuest的主任。

I'm the publisher of Universe Today, and with me is doctor Pamela Gay, a professor at Southern Illinois University Edwardsville and the director of CosmoQuest.

嘿，帕梅拉。

Hey, Pamela.

你最近怎么样？

How are doing?

我很好。

I'm doing well.

你怎么样，弗雷泽？

How are you doing, Fraser?

很好。

Good.

你注意到我加上了‘CosmoQuest的负责人’了吗？

Did you notice I added that director of CosmoQuest?

我。

I

注意到了。

did.

这非常令人兴奋。

That's very exciting.

我们已经做了这么长时间的CosmoQuest了，却总是忘记在所有我们做的事情中提到它。

Well, we've been doing CosmoQuest for so long, and we keep forgetting to include it in all the things that we do.

所以，对于从未听说过CosmoQuest的人，它是什么？

So for anyone who's never heard of CosmoQuest, what is it?

这是一个面向公众的在线研究平台。

It is a online research facility designed for the public.

我们的目标是为任何对参与太阳系和太空探索感兴趣的人提供机会，让他们能以与科学家相同的方式参与其中。

So we work to bring anyone out there who's interested in becoming part of solar system and space exploration an opportunity to engage in the same ways that scientists do.

我们有公民科学活动，还有每周的研讨会。

We have citizen science activities, we have weekly seminars.

我们还提供了包括论坛在内的多种不同参与方式。

We have a whole range of different ways including forums.

我们已将关于天文学和宇宙的今日论坛整合进了CosmoQuest。

We wove in the about astronomy universe today forums into CosmoQuest.

我们提供了多种方式供你参与其中。

We have a whole variety of ways for you to get involved in.

我希望你能花点时间访问 cosmicquest.org 了解一下。

I hope you'll take the time to check it out at cosmicquest.org.

嗯。

Yeah.

你可以对月球上的陨石坑进行分类，寻找太阳系中的冰冻天体。

You can you can classify craters on the moon, search for icy objects in the solar system.

我们的目标其实是帮助普通人与科学家一起开展真正的科学研究。

You know, really our goal is to try and help regular folk combine with scientists to do real science.

而这正是我们正在做的事情。

And and this is where we're this is what we're doing.

所以

So

而且我们正在取得成功。

And and we're succeeding.

绝对如此。

Absolutely.

是的。

Yeah.

嗯。

Yeah.

嗯。

Yeah.

不。

No.

太棒了。

It's awesome.

好的。

Okay.

很好。

Great.

我有个简短的公告。

I have one quick announcement.

抱歉。

So sorry.

所以我们正在逐步关闭 Astro Gear 商店，因为虽然我们非常喜爱你们所有人，但你们购买的东西并不多。

So so we are in the process of phasing out the Astro Gear store because while we love all of you, you don't buy a lot of things.

同时，在我们调整员工的过程中，我们优秀的乔·雷已经去追求更好的发展了。

And, as as we're working to to change out our staff, one of our wonderful Joe Ray has gone on to wonderful and better things than us.

我们非常难过，但为他感到骄傲。

We're very sad, but we're proud of him.

他之前负责经营我们的商店。

And he was the person running our store.

因此，未来我们仍会继续提供T恤，但其他所有商品都已进入清仓阶段。

So we will continue to offer t shirts into the future, but everything else we have is on closeout.

所以，如果你想购买东西，现在就是最好的时机。

So if you want to buy things, now is when you should buy things.

网址是 astrogear.com。

So that's astrogear.com.

好的。

Alright.

买点东西。

Buy things.

买点东西。

Buy things.

好的。

Alright.

我们现在就开始吧

We're gonna give now now can we start the

展示？

show?

是的。

Yes.

现在我们可以开始了

Now we can start

表演。

the show.

好的。

Alright.

本集《天文学播客》由第八灯公司赞助播出。

This episode of Astronomy Cast is brought to you by eighth Light Inc.

第八灯是一家敏捷软件开发公司。

Eighth Light is an agile software development company.

他们打造美观、耐用且可靠的应用程序。

They craft beautiful applications that are durable and reliable.

第八灯按需提供纪律严明的软件领导力，并分享其专业知识，以提升您的项目。

Eighth Light provides disciplined software leadership on demand and shares its expertise to make your project better.

如需更多信息，请访问他们的网站：www.eighthlight.com。

For more information, visit them online at www.eighthlight.com.

请记住，网址是 www.thedigit8thlight.com。

Just remember, that's www.thedigit8thlight.com.

给他们发个消息。

Drop them a note.

Eighth Light，软件是他们的技艺。

Eighth Light, software is their craft.

所以，如果你把足够的氢聚集在一起，引力会将其拉拢，直到温度和压力达到足以引发核聚变的程度。

So if you get enough hydrogen together in one place, gravity pulls it together to the point that the temperature and pressures are enough for fusion to occur.

这就是一颗恒星。

This is a star.

如果你没有足够的氢会怎样？

What happens when you don't have quite enough hydrogen?

那么你就会得到一颗失败的恒星，比如气态巨行星或褐矮星。

Then you get a failed star, like a gas giant planet or a brown dwarf.

所以今天我们要讨论的是失败的恒星。

So today we're gonna talk about failed stars.

所以

So

真惨。

sad.

但实际上，想想看，失败的恒星其实非常普遍。

But actually, think but, you know, failed stars are actually, like, super common.

所以可能比普通恒星更常见？

So maybe more common than regular stars?

它们在宇宙中数量很多。

There's a lot of them out there.

是的。

Yeah.

我认为我们目前还没有足够的统计数据。

I don't think we have enough statistics yet.

奇怪的是，我们真正开始发现这些天体也只是从八十年代开始的。

That's the crazy thing is we've only been finding these things since the eighties really.

而且直到有了2MASS巡天和其他一些项目，我们才真正开始以有意义的方式发现它们，目前也只发现了数百颗。

And and it's it's only been with the two mass survey and a few others that we've really started to be able to find them in a meaningful way, and we're only finding them by the hundreds.

但我们发现的红矮星数量却是以亿计的。

But we find red dwarfs by the bazillions, basically.

是的。

Yes.

好的。

Okay.

那么，让我们谈谈恒星形成的过程，这将帮助我们理解为什么有些恒星会失败。

So let's, so let's talk about sort of the just the process of what it takes to make a star and that will sort of help us understand why things fail.

对。

Right.

关于这个话题，我们有整期节目专门讨论过，回去听听那一期吧。

So so as we have entire shows on this, go back and listen to one of the shows on this.

简而言之，当你有一个巨大的分子气体和尘埃云时，当这个云受到某种冲击或被引力压缩时，所有这些气体会开始坍缩并碎裂。

But in in short, what happens is you have a giant molecular cloud of gas and dust and all of this material as the cloud gets shocked by something or gravitationally compressed by something, all of this gas begins to collapse and fragment.

各个碎片会开始旋转，有时会分裂成多个部分。

And the individual fragments will begin spinning, sometimes will split into multiple pieces.

这就是双星的由来。

This is where binary stars come from.

而有些碎片还不够大，无法进行氢聚变，这就形成了失败的恒星。

And some of those pieces just aren't quite big enough to fuse hydrogen and that's where we end up with failed stars.

现在，事情变得复杂的地方在于：行星的婴儿期是从哪里开始的呢？

Now where things get messy is well then where do baby planets come from?

在这种情况下，你有一个正在分裂和旋转的分子云碎片，在其核心会形成一颗恒星，而围绕这颗恒星的则是一个物质盘，这个盘会进一步分裂成围绕主恒星运行的多个部分。

So in this case you have a a fragmenting spinning chunk o molecular cloud and in its core you end up with a star forming and around that star will be a disk of material and that disk fragments into pieces that are orbiting around the primary star.

当你拥有双星时，就会出现两个正在坍缩和旋转的物质块。

Now then when you have binary stars, end up with two collapsing spinning bits.

而那个非盘状的部分，就是恒星。

And the non disky bit, that's that's the star.

你实际上可能会在形成双星的两个碎片周围都出现盘状结构。

And you can actually end up with disks around both of those fragments that are forming the binary star.

因此，这一切可能变得非常复杂，但关键在于：行星通过吸积过程在物质盘中形成，而恒星则通过分子云的分裂及其碎片坍缩形成，这些碎片最终希望能点燃氢聚变。

So this can all get very complicated but key component here is planets form in a disc of material through an accretion process whereas stars form via the fragmentation of molecular clouds and the collapse of those fragments into things that hopefully burn hydrogen.

对。

Right.

所以，实际上，我们将恒星定义为这种能力。

And so really, you know, we define that star as that ability.

足够的质量聚集在一起，发生了足够的反应，使得聚变发生，恒星就被点燃了。

Enough masses come together, enough is going on that you've got that fusion and the star ignites.

我们的太阳显然是其中之一，但恒星的规模可以小得多，对吧？

And our sun obviously is one of these these stars, but they get a lot smaller, right?

即使很小，它们仍然能维持。

To still have They do.

是的。

Yeah.

那么，还能小到什么程度，仍然能算作恒星呢？

So how how small how how small can you get when you still have star?

你仍然会得到一个成功的标志。

You still, you know, you still get a success ribbon.

根据我们目前的了解，这个临界值接近了，但我们尚未发现最小可能的恒星。

The cut off is near as we can tell and we haven't actually found the smallest possible star that you can have yet.

根据我们目前的理论推测，这个界限大约在木星质量的80到85倍之间。

As near as we can tell from theory is between eighty and eighty five times the mass of Jupiter.

因此，在某个点上，你就不再以太阳作为比较单位，而开始使用木星作为参照。

So at a certain point, you stop using the sun as your unit of comparison and you start using Jupiter.

取木星的质量，乘以80到85倍之间，氢就会开始发生聚变。

So take Jupiter, multiply by somewhere between eighty and eighty five and hydrogen will start fusing.

但如果你反过来，以太阳为参照，那它大约是太阳的百分之多少呢？

But if you were gonna go the other way and look at say the sun, what percentage of the sun would it be?

大概10%左右吗？

Like around 10%?

对。

Right.

所以与太阳相比，这些天体非常小。

So so compared to the sun, these are tiny objects.

它们的质量大约是太阳的7.5%到8%。

These are about seven and a half to 8% the mass of the sun.

所以是极其微小的恒星。

So tiny tiny tiny stars.

我总是觉得这些红矮星的过程非常有趣，因为它们没有辐射层，对吧？

And I always find the process of these these red dwarf stars really fascinating because they're you know, they have no radiative zone, right?

它们完全是对流层，整个星体都在翻腾其物质，因此寿命非常长。

It's all convective zone and the whole thing is just churning its material and they actually last a really long time.

它们能持续进行恒星核聚变。

They can keep the stellar fusion going.

对，这就是红矮星，没错。

And and so this is the red dwarfs Yeah.

我们正在讨论的就是这些红矮星。

That we're So these are red dwarfs that we're talking about.

它们是完全对流的。

They're fully convective.

就像你的 lava lamp 一样，你看到那些液滴上升到表面，然后又全部流回底部。

So just like with your lava lamp, you see the blobs going to the surface and then going all the way back down to the bottom.

在红矮星中，核心发生核聚变，热物质上升到表面并完全循环。

In red dwarfs you have the same process going on where there's nuclear fusion going on in the core but then the hot material rises up to the surface fully circulating.

所以当红矮星最终耗尽氢聚变过程时，它几乎用尽了所有可以被利用的物质。

So when a red dwarf finally finishes the hydrogen process, it's pretty much used up everything that can be used up in

太阳。

the sun.

但这些小恒星会持续存在，你知道，它们能持续数万亿年。

But it'll last, you know, those small ones, they're gonna last trillions of years.

是的。

Yeah.

这些是我们星系中寿命最长的天体。

These are the longest lived things in our galaxy.

是的，完全正确。

Yeah, totally.

所以，好吧。

So okay.

所以，这就是我们设定界限的地方。

So so that's sort of where we set our limits.

因此，任何超过太阳质量百分之七点五的天体都算是恒星，而上限大约是太阳质量的100倍。

And so anything above seven and a half percent of the sun, you've got star, and there's really no, I guess, a 100 times the mass of the sun.

你知道，这个范围挺大的。

You know, that's a big a big range.

但显然，你会看到氢气团在比这百分之七点五更小的质量下聚集在一起。

So but obviously, you know, you're end up with clumps of hydrogen coming together at smaller amounts than this seven and a half this times the seven and a half percent of the sun.

那我们把这些叫什么呢？

So what do we call these?

这些就是你开始进入褐矮星范畴的地方。

Those are where you start to get into the brown dwarf stars.

这些天体我们不仅根据它们的形成方式来定义，还根据它们核心是否能短暂地、但并不成功地维持核聚变过程来界定。

The these are objects that well, we define them not just by how they form, but also by how they sort of kind of, but then not very successfully for very long do have a fusion process in their core.

对于褐矮星来说，它们的质量是木星质量的13到80到85倍。

So with brown dwarf stars, the these are objects these are objects that are 13 to well, 80 to 85 times the mass of Jupiter.

在这一临界点上，它们能够短暂地在核心中燃烧氚和氘。

And at that cutoff, they're able to very briefly burn tritium and deuterium in their course.

这些是氢的重同位素，其中心含有额外的中子。

These are heavy forms of hydrogen that have extra neutrons in their centers.

这些额外的氢，也就是重氢，是从哪里来的呢？

Where do those come from, that that extra hydrogen, the the heavy forms of hydrogen?

这只是宇宙中的一种组成成分。

The it's just one of the components of the universe.

你观察宇宙，就会发现重氢的存在。

You look around the universe, you're going to find heavy hydrogen.

哦，我明白了。

Oh, I see.

所以，在一大团氢中，会有一部分含有这些重元素。

And so there's like a certain percentage of just a blob of hydrogen that's gonna have those those heavy elements in.

好的。

Okay.

就像水一样，有重水，我们在海洋中也能找到重水。

So just like water, there's heavy water and we find heavy water in the ocean.

这就是我们海洋的一部分，其中一些H₂O分子中的氢原子被氘原子取代了，而不是普通的氢。

It's just part of our ocean where some of the h two o formed with a deuterium atom in it instead of just straight old hydrogen.

那么，这些物质是会坠入恒星内部并聚集在一起，还是只是其中有一部分能够……

And so does this stuff like fall inside the the star and clump together or is it just a a percentage of it that's able it's

它只是其中的一小部分，关键在于它很容易被利用。

able to It's just a percentage of it that it's easy that it's easy for it to use is the key.

当氢缺少那些额外的中子时，它几乎不像含有额外中子的较重形式那样容易燃烧。

Hydrogen doesn't burn when it's missing those extra neutrons nearly as easily as the the heavier forms with the extra neutrons in it.

因此，物理学使得这些恒星更容易燃烧重氢，却无法轻易燃烧缺少这些额外中子的普通氢。

So physics simply lets these stars more readily burn and then doesn't allow it to burn hydrogen that is missing these extra neutrons.

不幸的是，较重的氢同位素要稀少得多。

And unfortunately, the heavier forms of hydrogen are much more rare.

所以因为它们稀少，也就是说，整个天体中由这种物质构成的部分只占很小的比例。

And so because it's rare, I mean, it's only a small percentage of of the overall object that's made up from this stuff.

那么，它能产生多少能量、多少热量、能做多少事呢？

So so how much energy, how much heat, how much how much can it do?

总之，它只能燃烧几亿年。

Well, at at the end of the day, it it's able to burn only for a few 100 million years.

所以你有一个完全对流的小恒星，根据它的大小不同，在某些情况下，它甚至能燃烧一些锂，因为锂很容易燃烧。

And so you have this fully convective little star that depending on just how big it is, in some cases they can actually burn some lithium as well because lithium burns very easily.

但这种燃烧只持续几亿年，一旦结束，就彻底结束了。

But it's it's only for a few 100 million years and once they're done, they're done.

那它们能有多热呢？

And and how hot do they get?

最令人惊叹的是，这些恒星在正常观测状态下，表面温度在某些情况下几乎和人体体温一样。

That's the really kind of awesome thing is these things are are, during their their normal observed state, in some cases, basically human body temperature on their surface.

真的吗？

Really?

是的。

Yeah.

所以我们正在研究的恒星，通常温度低于一千开尔文。

So so we're looking at stars that in general are under a thousand degrees Kelvin.

对。

Right.

但越往里走，温度就越高。

But but way hotter it the deeper you go.

对。

Right.

也许吧。

Maybe

木星更热。

Jupiter is hotter.

对吧？

Right?

对。

Right.

对。

Right.

不。

No.

完全正确。

Totally true.

但事实上，它们的表面确实如此。

But but the fact that on their surface Yeah.

它们的温度能达到人体温度。

They they get to be human temperature.

而试图弄清楚如何处理这些情况，迫使我们拓展了对恒星的看法。

And and trying to figure out what to do to these forced us to expand the way we look at stars.

我们通常有O、B、A、F、G这些类型，按温度从高到低排列。

We we normally have the o's of the hottest b a f g.

所以我们是那种普通的G型恒星。

So we're we're one of those normal g type stars.

K、M、M型星是红矮星。

K m m are red dwarfs.

当我们开始增加新类型时，他们不得不添加L型星，这类恒星开始出现氢化物带。

Well, as as we started adding new types they they had to add an l class which are stars that start to have hydride bands in them.

它们开始出现碱金属带。

They start to have alkaline metal bands in them.

然后他们不得不进一步添加T型星。

They then had to go on to add t class stars.

这些是我们在恒星大气中开始观测到一氧化碳的恒星。

These are stars where we actually start to see carbon monoxide in the atmospheres of the stars.

并且这一分类一直延伸到，目前有少数我们称为Y型星的恒星。

And it goes all the way out to, there's a handful of what we call y type stars.

这些是我们在其中开始观测到氨吸收线的恒星。

And these are stars where we start seeing things like absorption lines from ammonia.

这实际上创造了一个更礼貌但更令人不安的助记符来理解这一切，因为‘亲我’。

And this actually made a much more polite and disturbing, mnemonic for how we think of all of this because kiss me.

是的。

Yeah.

这是我们熟悉的那种。

Is the normal one that we're used to.

现在我们增加了L、T和Y型，所以变成了哦，别再烦我，亲我吧，晚点再说。

Now we've added an l and a t and a y, so it's become oh be a fine guy kiss me later.

谢谢。

Thank you.

对。

Right.

那么，这些棕矮星中，有些仍在持续消耗和燃烧这些较重的氢元素，而另一些则已经耗尽了燃料，这两者之间有区别吗？

So then is there a I mean, there this distinction between these brown dwarves that are actively consuming and burning this, you know, these heavier forms of hydrogen and the ones that have run out of fuel?

天文学家会对它们做出某种区分吗？

Do astronomers make some kind of distinction between them?

没有。

No.

而且说实话，我不确定我们是否在任何地方观测到过能明确指出某个天体目前正在发生核反应的情况。

And and I honestly don't know if we've observed it anywhere that we can specifically say this one is currently undergoing nuclear reactions.

这些在我们目前的观测数据集中是极其罕见的天体。

The these are extremely rare objects in our current observational datasets.

我无法告诉你它们在天空中究竟有多罕见或不罕见。

I I can't tell you how rare or not rare they are in the sky.

但因为我们才刚开始观测到它们，我们只有这么少的数据点，而且它们燃烧的时间如此短暂，以至于在我们仅有的几百次观测中捕捉到一个正在燃烧的天体是极其困难的。

But because we're only starting to absorb them, we only have so many data points and they burn for such a short period of time that trying to catch one in our few 100 observations is actively burning.

我不知道从统计学上来说，我们是否已经能确信应该已经观测到过这种情况。

I don't know statistically we can say we should have done that with certainty yet.

但这是否属于一种情况：当它达到一定温度后，就会需要非常漫长的时间才能冷却下来？

But is it one of those situations where it gets to its temperature and then it just takes a really long time to cool down?

我的意思是，我知道我们常说恒星会演变成白矮星，然后白矮星最终会变成黑矮星，但这个过程需要数十亿甚至数万亿年，这些恒星才能达到宇宙背景温度。

I mean, I know that we talk about stars that turn into white dwarves and then the white dwarves will eventually turn into black dwarves, but that process is gonna take billions and trillions of years for these stars to reach the background temperature of the universe.

因此理论上

And so in theory

归根结底，这些天体根本不会变得那么热。

And at the end of the day, these these these just don't get that hot.

它们就是不会变得那么热。

They they just don't get that hot.

但它们仍然在很长一段时间内持续冷却。

But they're still cooling down over long periods of time.

它们确实会冷却，但并不是像白矮星那样冷却的方式。

They they are, but it's it's not the same way you think of of white dwarfs cooling off.

对于白矮星来说，它们最初温度高达数万开尔文。

With a white dwarf, you're starting off with something that's tens of thousands of degrees Kelvin.

当它们冷却到几百开尔文，变成我们所说的黑矮星时，这是一个巨大的变化。

And and so when they cool off to a few 100 degrees Kelvin and become what we call black dwarfs, that's a massive change.

这些天体一开始温度大约在一千开尔文左右，然后冷却到几百开尔文。

These guys start off around a thousand degrees Kelvin and cool off to a few 100 degrees Kelvin.

因此，当你观察这样的情况时，情况就非常不同了。

And so when you're looking at something like that, it's a very different situation.

这些恒星的运作方式与我们通常所想的完全不同。

And and these these are just they're stars that don't work in the ways that we think of.

其中最小的像木星一样依靠正常的气体压力支撑，而最大的则像白矮星一样依靠电子简并压力支撑。

The smallest of them just like Jupiter are are supported through normal gas pressure but the largest of them are supported just like white dwarfs through electron degeneracy pressure.

所以这里有一种非常小、密度相当高，但还没达到白矮星密度的天体。

So here you have something extremely small, fairly dense but not white dwarf dense.

它们的半径都集中在相同半径的10%到15%范围内。

All of them were are within 10 to 15% of the same radius.

拿木星来说，你往木星上添加物质，它并不会变大。

So take Jupiter and you add stuff to Jupiter and it doesn't get bigger.

是的。

Yeah.

它只是变得更致密。

It just gets denser.

继续添加物质，它支撑自身的方式就会从气体压力转变为电子简并压力。

Keep adding stuff and it changes how it supports itself from gas pressure to electron degeneracy pressure.

它们在整个范围内温度变化并不大。

Their their temperature doesn't vary that much across the entire range.

这些天体的行为方式与我们通常对恒星的认知不同，因为它们不是普通的恒星。

The these things just don't behave in the way that we're normally used to thinking of stars because they aren't normal stars.

它们是一种奇特的过渡天体。

They are this weird transition object.

好的。

Okay.

所以我想接下来问的问题是，天文学家使用什么方法来发现这些天体呢？

So I guess the question that I wanted to ask next then is is what is the method that astronomers use to find these objects?

因为它们并不明亮，也不会在夜空中发光，他们是怎么找到它们的？

Because they're not bright, they're not shining in the night sky, How do they find them?

红外线。

Infrared.

而且不仅仅是它们不够明亮。

And and it's it's not just that they're not bright.

并不是它们不够亮，而是它们并没有在有用的波长上发出光。

It's that they're not bright, and they're not really giving off light in useful wavelengths.

用普通望远镜探测到非常非常暗的蓝色或红色天体是完全可能的。

It it's perfectly possible to detect a very, very faint blue object, red object with normal telescope.

没什么大不了的。

No big deal.

它们很暗。

They're faint.

它们很烦人。

They're annoying.

我们能做到。

We can do it.

现在，褐矮星带来了完全不同的挑战，因为它们的光几乎全部集中在普通光学望远镜难以观测的波长上。

Now now brown dwarfs pose an entirely new challenge because they're so extraordinarily red that the bulk of their light is given off in wavelengths that aren't readily observed with your normal optical telescope.

因此，你必须进入地球大气层之上，开始使用像WISE望远镜这样的设备。

So you have to get above the earth's atmosphere and you have to start using things like the WISE telescope.

这是被使用过的一种仪器。

That's one of the instruments that's been used.

它们是通过地面观测发现的，斯隆数字巡天项目在发现它们方面做了大量工作。

They are found ground based, Sloan Digital Sky Survey has done a lot of work finding them.

但发现它们最简单的方法是从红外波段开始观测。

But the easiest way to find them is to start looking in the IR.

你在寻找这些天体时遇到的另一个问题是，它们喜欢靠近明亮的恒星。

The other problem that you run into in trying to find these suckers is they like to cuddle up next to nice bright stars.

因此，你现在必须使用所谓的日冕仪，也就是在天空中的恒星图像前放置一个遮挡盘，挡住它的光，然后查看是否有微弱的天体靠近这颗明亮的恒星。

And so now you have to start doing things like using what are called coronagraphs which is where you essentially put a disc in front of your stellar disc on the sky, block out its light and then look to see if there's anything faint near that bright star.

所以，为了寻找双星系统中的褐矮星，不得不对天空中每一颗明亮的恒星都使用日冕仪，这变得相当繁琐。

So it gets kind of tedious to have to use a chronograph to look at every bright star in the sky to try and find brown dwarfs that are in binary systems.

更容易发现的是那些孤立的褐矮星。

It's the isolated ones that are easier to find.

对。

Right.

所以关键是，如果你遇到恒星与一颗更亮的恒星组成双星系统的情况，这就能帮你确定去哪里找，因为它们实在太难观测了。

So the point being that if, you know, you're gonna get a situation where the star is in a binary companion with a brighter star, this gives you a way to to know where to look because they're so hard they're so hard to see.

我知道人们也在这些恒星育婴区寻找它们。

And I know that people also were looking for them just in these stellar nursery.

对吧？

Right?

他们在寻找那些更亮恒星可能存在的区域。

They're looking for places where brighter stars are likely to be.

对。

Right.

所以因为你要

So because you

可能会找到

might find

我们在所有寻找普通恒星的地方都会寻找它们，但它们很难被发现。

We look for them all the places we look for normal stars, but they're annoying to find.

你真的必须在红外和近红外波段进行观测。

You really have to be looking in the IR and the near IR.

是的。

Yeah.

你知道，未来五年内詹姆斯·韦伯太空望远镜就要发射了。

Now, you know, we've got the James Webb Space Telescope coming out in the next five years.

它能帮助我们搜寻褐矮星吗？

Will that be able to help join the search for for brown dwarfs?

我认为用如此强大的望远镜去巡天寻找新的褐矮星，会是一种奇怪的用途。

I I think that that would be a a strange use of such a powerful telescope to use it to survey for new brown dwarfs.

但它能做的，也是我预期它会做的事，是成像，不仅针对褐矮星，还包括巨大的类木行星。

But what it can do and what I expect it will be doing is imaging not just brown dwarfs but also giant Jupiters.

我们现在已经开始能够单独观测一些系外行星了。

We're we're now at the point that we're starting to be able to individually look at some extra solar planets.

斯皮策望远镜已经在少数案例中做到了这一点，它们也以这种方式观测过一些褐矮星，对已发现的天体进行个体化的有意义研究。

Spitzer's done this in a few cases and they they've also looked at a few brown dwarfs this way and do individualized meaningful studies of things that are already discovered.

要首先巡天并 catalog 天空中的天体，然后进行详细跟进并理解这些天体的真实性质，确实需要一系列不同类型的望远镜。

It it really takes a whole family of different types of telescopes to first survey the sky and catalog what's there and then follow-up in detail and understand what those objects really are.

对。

Right.

所以它可能不适合用于巡天，但绝对是进行后续观测的绝佳工具，没错。

And so it might not be the the tool for surveying, but it's definitely be the tool for doing follow-up Yeah.

我的意思是，这将是一台巨大的望远镜。

I mean, it's an it's gonna be an enormous telescope.

哈勃望远镜大约是1.6米，而这是6.5米的望远镜。

Hubble is, like, 1.6 meters, and this is 6.5 meter telescope.

没错。

It's just Right.

它非常庞大。

It's enormous.

对。

Right.

但这说得通。

But that makes sense.

用它来观测它们可能是在浪费它的时间。

You might be a waste of its of its time to be surveying for them.

对。

Right.

所以你实际上引出了这一点。

So now you actually sort of led into this.

对吧？

Right?

我们目前面临这种情况。

We've got this situation.

我们有这些褐矮星，也就是失败恒星的高端，但其实这是一个连续谱。

We've got these these brown dwarfs, the the high end of the of the failed star, but it's really a spectrum.

从氢聚在一起到完全不聚，你都会遇到某种情况。

Wherever you get hydrogen clumping together all the way down to nothing, you know, you're gonna have this you're gonna have some situation.

那么我们反过来谈。

So so let's go the other way.

当我们变得越来越小、质量越来越低时，我想‘小’这个说法并不准确。

And as we get smaller and smaller and smaller, less mass I guess smaller is not a good way to put it.

对吧？

Right?

因为正如你所说，它们的大小基本上保持不变。

Because as you said, they they kinda stay the same size.

对。

Right.

它们只是变得更致密。

They just get more more dense.

那么在低端，这种情况是如何发生的呢？

So how does how does that work on the on the lower end?

在低端，事情就开始变得复杂了，人们也开始争论，因为我们根本无法把探针插入这些系外行星或褐矮星内部，去弄清楚它们是否曾经发生过核聚变。

Well, on the lower end, this this is where things start to get messy and people start to argue because we can't basically stick a probe inside of one of these extra solar planets or brown dwarfs and try and figure out, well, did it ever do any burning?

所以我们开始观察大气中是否存在锂。

So so what we start doing is looking is there lithium in the atmosphere.

如果大气中有锂，那就意味着它没有燃烧锂。

If there's lithium in the atmosphere, it means it didn't burn lithium.

因此，这至少为系统提供了一个约束条件。

So that at least puts one level of constraint on the system.

好的。

Okay.

当我们继续往下分析时，人们就开始争论了。

And and as we go down, people just start arguing.

我们知道，低于10倍质量的不是行星。

So we know that below 10 masses, not a planet.

我们非常确定，高于13倍质量的就是一颗失败的恒星，曾经发生过某种短暂的核聚变。

We're pretty sure above 13 masses is a failed star, did have some sort of temporary nuclear burning.

在中间这个范围内，存在着一些紧贴恒星的奇特天体，我们称之为褐矮星，它们的质量大约是木星的10倍。

In that middle range, you have these weird objects snuggled up against stars that we call brown dwarfs, but they're at the 10 Jupiter mass level.

人们认为，这可能是某种质量损失或其他情况造成的。

And it's thought that there is either some sort of mass loss or something else happened.

因此，对于这些天体该如何命名还不清楚。

And and so it's unclear what to call some of these objects.

它们是失败的恒星吗？

Are they failed stars?

它们是膨胀的行星吗？

Are they bloated planets?

我认为，在这个定义上仍需要大量研究，我们需要更好的模型。

And and that's one where I think a lot of work on the definition still needs to happen and we need better models.

而且，部分标准在于它是否围绕恒星运行？

And I mean part of it is like is it orbiting a star?

但我想这正是区别所在。

But I guess that's the distinction.

对吧？

Right?

双星。

Binary.

是的。

Yeah.

它是伴星，还是围绕恒星运行的行星？

Is it a binary companion or is it a planet going around a star?

如果我们没有观测到它的形成过程，也没有看到它所属的原行星盘，我们就无法知道这个我们正在观测的天体究竟是像行星那样通过吸积过程形成的，还是像恒星那样通过坍缩过程形成的。

And and if we didn't watch it form and and we don't see a protoplanetary disk that it's part of, we we have no way of knowing did did this object that we're looking at form via an accretion process like a planet or through a collapse process like a star.

你之前提到过，像木星这样的天体，如果你给木星增加质量，比如让两个木星碰撞在一起，你并不会得到一个大得多的天体。

And now you mentioned sort of earlier on that that things like Jupiter, for example, if you added mass to Jupiter, added you know, you collided two Jupiters together, you wouldn't necessarily get a much larger object.

对吧？

Right?

不对。

No.

你会得到一个大小几乎完全相同的天体，误差在百分之几以内。

You get an object the exact same size, more or less, within a few percent.

这正是其中一件令人惊叹的事情。

That's one of the kind of awesome things.

这是一个特殊情况，密度持续增加，而压力与引力的平衡使得半径从大约木星大小一直到接近80倍木星质量、但仍不足以成为恒星的天体，都保持非常相似。

It it's one of those cases where the density just keeps going up and the way the pressure and gravity balance, the radius stays very similar as you go from roughly Jupiter sized all the way up to one of these, well, 80 Jupiter mass not quite yet a star objects.

哇。

Wow.

是的。

Yeah.

这真的非常了不起。

It it's really kind of awesome.

这完全是物理规律以这种方式达到平衡的结果。

It's it's it's physics just balances out this way.

如果你能观察一颗褐矮星，你会看到什么？

Now if you could look at one like a brown dwarf, what would you see?

你会看到一个呈品红色的天体，其表面有对流细胞。

You'd see a magenta object that has convective cells on the surface.

当你通过一个优质的氢阿尔法滤光镜观察太阳，并充分放大时，可以看到其表面这些沸腾的细胞结构。

So when when you look at the sun through a really good hydrogen alpha filter and you magnify it sufficiently, can see these boiling cells on its surface.

实际上，褐矮星表面也有对流细胞在驱动。

Actually have convective cells driving brown dwarfs as well.

‘棕色’这个名称其实是个误称，因为棕色通常不是通过加色光过程产生的颜色。

And and brown is really a a misnomer that brown isn't something you get through additive light processes generally.

相反，它们呈现出一种深深的品红色。

Rather, they're this deep deep magenta.

我不太想这么说，但它们的颜色基本上和我现在的头发颜色一样。

I hate to say this, but they're basically the color of my hair currently is.

但没错，它们是品红色的天体，而‘棕色’这个词更容易说和拼写。

But, yeah, they're magenta objects and brown is just much easier to say and spell.

所以是一种偏红的颜色，对吧？

So sort of a reddy Yeah.

一种偏红的颜色，但更深、更暗，类似于红矮星的光谱范围？

A reddy color, but with big so like on the spectrum of a red dwarf, but deeper red, darker red?