Deuterium Abundance

The stability of deuterium is one of the "windows of creation" that are critical in the standard "big bang" model. But deuterium tends to fuse quickly to form helium, so the abundance of deuterium in the present universe is a sensitive probe into the processes that occurred in the early universe. Deuterium, which contains one proton and one neutron, was created a few minutes after the Big Bang. Its presence today in the local universe serves as a tracer for star creation and galaxy building throughout the eons. This is because any deuterium in stars tends to be quickly fused into helium. So nearly all the deuterium seen today is "pure," having never been burned by stars. Knowing how much deuterium was created in the Big Bang and how much still exists today allows scientists to estimate how much gas has been used to create stars.

氘的稳定性是标准“大爆炸”模型中至关重要的“创造之窗”之一。但氘倾向于迅速融合形成氦，因此现今宇宙中氘的丰度是早期宇宙过程中关键事件的敏感探测器。氘由一个质子和一个中子组成，是在大爆炸后几分钟内形成的。它在当今局部宇宙中的存在可以作为恒星形成和星系构建的示踪剂。这是因为任何存在于恒星中的氘都倾向于迅速融合成氦。因此，今天所见的几乎所有的氘都是“纯净的”，从未被恒星燃烧过。了解大爆炸时创造了多少氘以及如今仍存在多少氘，使科学家能够估算出多少气体被用来形成恒星。

Some light has been shed on the behavior of deuterium by observations from the Far Ultraviolet Spectroscopic Explorer (FUSE).

有关氘的行为，通过远紫外光谱探测器（FUSE）的观测已提供了些光。

This is a false-color image of the star AE Aurigae (bright source of light slightly off center of image) embedded in a region of space containing smoke-like filaments of carbon-rich dust grains, a common phenomenon. Such dust might be hiding deuterium, an isotope of hydrogen, and hindering astronomers' efforts to study star and galaxy formation. The FUSE satellite has surveyed the local deuterium concentration in the galaxy and found far more than expected. It may be that the hot star vaporized some of the deuterium from dust grains where it was "hiding".

这张假彩色图像显示了恒星AE Aurigae（图像中心稍偏的明亮源），它嵌入了一个含有碳丰富尘埃颗粒的空间区域，这些尘埃颗粒呈现出烟雾状的丝状结构，这是一种常见现象。这种尘埃可能隐藏着氘，一种氢的同位素，阻碍了天文学家对恒星和星系形成的研究所需的观测。FUSE卫星对银河系中的氘浓度进行了调查，并发现其浓度远高于预期。也许这颗炽热的恒星已经使一些原本隐藏在尘埃颗粒中的氘蒸发掉了。

Deuterium's spectral fingerprint in the ultraviolet allows it to be distinguished from the normal isotope of hydrogen by FUSE's spectrometer. Primordial deuterium concentrations of about 27 parts per million hydrogen atoms have been estimated by various non-FUSE studies. Recently NASA's Wilkinson Microwave Anisotropy Probe confirmed this approximation. But measurements in our galactic neighborhood have shown large variations in the measured deuterium. FUSE detected levels of 15 ppm in our neighborhood and as low as 5 ppm in some other locations. The peak levels of deuterium measured by FUSE in our galaxy were about 23 ppm, which still needs explanation in comparison to the modeled 27 ppm, but models for how the lower concentrations where produced have been proposed.

氘在紫外区的光谱特征使其能够通过FUSE光谱仪与普通氢同位素区分开来。各种非FUSE研究估计原始氘的浓度约为每百万个氢原子27个。最近，NASA的威尔金森微波各向同性探測器确认了这一近似值。但本星系邻域的测量结果却显示出氘浓度的显著变化。FUSE在本星系邻域测得的氘浓度为15 ppm，而在某些其他地点则低至5 ppm。FUSE在银河系中测到的氘最高浓度约为23 ppm，尽管这一数值仍需解释，因为它与模型预测的27 ppm相比仍有差距，但关于如何产生较低浓度的模型已提出。

In 2003, Bruce Draine of Princeton University, a team member on the new FUSE study, developed computer models that showed how deuterium, compared to hydrogen, might preferentially bind to interstellar dust grains, changing from an easily detectable gaseous form to an unobservable solid form. The new FUSE data strongly support this theory. In regions that remain undisturbed for long periods, such as the "local bubble" around our sun a few hundred light-years across, deuterium atoms systematically leave the gas phase and replace normal hydrogen atoms in dust grains. FUSE cannot detect this non-gaseous form, which explains the low detection level of 15 parts per million hydrogen atoms in our neighborhood and values as low as 5 parts per million elsewhere. When a region is disturbed by a supernova or hot stars, dust grains are vaporized, releasing deuterium atoms back into a gas phase. FUSE detects high deuterium levels in such regions.

2003年，普林斯顿大学的布鲁斯·德拉因，也是新FUSE研究团队的一员，开发了计算机模型，显示氘相比氢可能更倾向于吸附到星际尘埃颗粒上，从容易检测的气态形式转变为不可观测的固态形式。新的FUSE数据强烈支持这一理论。在长时间未受干扰的区域，例如以我们的太阳为中心的“本地气泡”，直径几百光年，氘原子系统性地从气态转变为尘埃颗粒中的普通氢原子。FUSE无法检测这种非气态形式，这解释了在我们附近氢原子的检测水平仅为每百万分之一，而在其他地方则低至每百万分之五。当一个区域因超新星或高温恒星而受到扰动时，尘埃颗粒会被气化，释放出氘原子回到气态中。FUSE在这样的区域检测到较高的氘水平。

"The peak galactic detection levels are likely close to the real total deuterium abundance in the Milky Way, with the rest of it in hiding, not destroyed," said Warren Moos of Johns Hopkins University in Baltimore, FUSE Principal Investigator and co-author on the report in the August 20, 2006 issue of The Astrophysical Journal.

沃伦·穆斯（Warren Moos）是约翰霍普金斯大学巴尔的摩分校的教授，也是FUSE项目的首席调查员及2006年8月20日《天体物理期刊》上报告的合著者。他指出，银河系的峰值探测水平可能接近银河系中实际存在的氘的总量，其余的氘则隐藏在暗处，而非被摧毁。

If the peak levels are 23 parts per million, this implies that either significantly less material has been converted to helium and heavier elements in stars or that much more primordial gas has rained down onto our galaxy over its lifetime than had been thought. In either case, our models of the chemical evolution of the Milky Way galaxy will have to be revised significantly to explain this new result, said George Sonneborn of NASA Goddard Space Flight Center in Greenbelt, Md., co-author and mission project scientist.

如果峰值水平为23百万分之一，这表明要么在恒星中显著较少的物质转化为氦和更重的元素，要么在银河系存在这么久以来，从原始气体中降落到银河系的气体远比人们 previously thought 的要多。无论哪种情况，我们的银河系化学演化模型都必须大幅修订，以解释这一新结果，”NASA戈达德空间飞行中心位于马里兰州格林贝尔特的乔治·索内博恩说道，他是该研究的共同作者和任务项目科学家。