As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet’s atmosphere, causing the planet to seem bigger; plotting the planet’s observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet’s atmosphere. Chemical species composed of light elements—such as hydrogen, oxygen, carbon, sodium and potassium—have in this way been detected in the atmospheres of several hot giant exoplanets, but molecules composed of heavier elements have thus far proved elusive. Nonetheless, it has been predicted that metal oxides such as titanium oxide (TiO) and vanadium oxide occur in the observable regions of the very hottest exoplanetary atmospheres, causing thermal inversions on the dayside. Here we report the detection of TiO in the atmosphere of the hot-Jupiter planet WASP-19b. Our combined spectrum, with its wide spectral coverage, reveals the presence of TiO (to a confidence level of 7.7σ), a strongly scattering haze (7.4σ) and sodium (3.4σ), and confirms the presence of water (7.9σ) in the atmosphere.

中文翻译：

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在热木星的大气中检测氧化钛

当系外行星穿过其主恒星时，来自恒星的一些光被行星大气中的原子和分子吸收，导致行星看起来更大；将观测到的行星大小绘制为光波长的函数会产生透射光谱。测量传输光谱中的微小变化，连同大气建模，然后为系外行星大气的特性提供线索。由轻元素组成的化学物种——如氢、氧、碳、钠和钾——已经在几个炽热的系外行星的大气中被检测到，但迄今为止，由较重元素组成的分子仍然难以捉摸。尽管如此，据预测，在最热的系外行星大气的可观测区域中会出现氧化钛 (TiO) 和氧化钒等金属氧化物，从而导致日侧的热反转。在这里，我们报告了在热木星 WASP-19b 的大气中检测到二氧化钛。我们的组合光谱具有广泛的光谱覆盖范围，揭示了二氧化钛的存在（置信水平为 7.7σ）、强烈散射的雾度（7.4σ）和钠（3.4σ），并证实了水的存在（7.9σ）在大气中。