Helium escaping from hot gas giants Many gas giant exoplanets orbit so close to their host star that they are heated to high temperatures, causing atmospheric gases to escape. Gas giant atmospheres are mostly hydrogen and helium, which are difficult to observe. Two papers have now observed escaping helium in the near-infrared (see the Perspective by Brogi). Allart et al. observed helium in a Neptune-mass exoplanet and performed detailed simulations of its atmosphere, which put constraints on the escape rate. Nortmann et al. found that helium is escaping a Saturn-mass planet, trailing behind it in its orbit. They combined this with observations of several other exoplanets to show that atmospheres are being lost more quickly by exoplanets that are more strongly heated. Science, this issue p. 1384, p. 1388; see also p. 1360 Observations of helium show that the atmosphere of a hot Saturn-mass exoplanet is escaping and trailing behind the planet. Hot gas giant exoplanets can lose part of their atmosphere due to strong stellar irradiation, and these losses can affect their physical and chemical evolution. Studies of atmospheric escape from exoplanets have mostly relied on space-based observations of the hydrogen Lyman-α line in the far ultraviolet region, which is strongly affected by interstellar absorption. Using ground-based high-resolution spectroscopy, we detected excess absorption in the helium triplet at 1083 nanometers during the transit of the Saturn-mass exoplanet WASP-69b, at a signal-to-noise ratio of 18. We measured line blueshifts of several kilometers per second and posttransit absorption, which we interpret as the escape of part of the atmosphere trailing behind the planet in comet-like form.

中文翻译：

---

土星质量系外行星 WASP-69b 中扩展氦气的地面探测

氦气从热气态巨行星中逸出 许多气态巨行星系外行星的轨道距离它们的主恒星如此之近，以至于它们被加热到高温，从而导致大气气体逸出。气态巨行星大气主要是氢气和氦气，很难观测到。现在有两篇论文观察到了近红外中逸出的氦（见 Brogi 的观点）。阿拉特等人。在海王星质量的系外行星中观察到氦气，并对其大气进行了详细的模拟，这对逃逸率施加了限制。诺特曼等人。发现氦正在逃离土星质量的行星，在其轨道上落后于它。他们将此与对其他几颗系外行星的观察相结合，表明大气被更强烈加热的系外行星以更快的速度消失。科学，这个问题 p。1384 页。第1388章 另见第。对氦气的 1360 次观测表明，一颗热的土星质量的系外行星的大气正在逃逸并拖到行星后面。由于强烈的恒星辐射，热气巨行星可能会失去部分大气层，这些损失会影响它们的物理和化学演化。对系外行星大气逃逸的研究主要依赖于对远紫外区氢 Lyman-α 谱线的天基观测，该谱线受星际吸收的影响很大。使用基于地面的高分辨率光谱，我们在土星质量系外行星 WASP-69b 凌日期间以 18 的信噪比检测到氦三重态在 1083 纳米处的过量吸收。我们测量了几个线蓝移公里/秒和运输后吸收，