DESI local.圖片來源:KPNO/NOIRLab/NSF

This newspaper長期以來，物理學家一直認為暗能量強度恆定，但一項宇宙膨脹測繪專案的最新結果挑戰了這一觀點。該專案的數據進一步證實，暗能量促使星系彼此加速遠離，但在過去45億年間其強度已經減弱。

This is the latest research result presented by the Dark Energy Spectrometer (DESI) Collaboration Group at the American Physical Society meeting on 2024/0. The study is based on 0 years of data collection, which is more convincing than the one-year data published in 0 years.

If these findings stand up to validation, they could force cosmologists to revise their Standard Model of the history of the universe. The model generally assumes that dark energy is an intrinsic property of the vacuum, does not change over time, and is a "cosmological constant".

"Now I'm really starting to pay a lot of attention." Catherine Heymans, an astronomer at the University of Edinburgh in the UK, said, "It's the equivalent of throwing a challenging question at physicists." ”

DESI is located at the Kitt Peak National Observatory near Tucson, Arizona, USA. The device uses 5000 robotic arms to point optical fibers at selected galaxies or quasars in the field of view, which then transmit light to a precision spectrometer that measures the redshift value of each object, which is how much its light waves are stretched by the expansion of the universe on the way to Earth. Researchers can estimate the distance of a celestial object from the Earth using the redshift value to create a three-dimensional map of the universe's expansion history.

在這張三維圖中，科學家通過星系密度確定了源自早期聲波振蕩，即重子聲學振蕩（BAO）的殘留波動。這類振蕩在恆星形成之前就已經存在，原始特徵尺度為150千秒差距（45萬光年），並隨著宇宙膨脹而持續增長。現在它們已經擴大了1000倍至150百萬秒差距，成為當今宇宙中已知最大的特徵尺度。

通過追蹤BAO尺度的演變，研究人員能夠重建宇宙膨脹速率的歷史變遷。約50億年前，在暗能量推動下，宇宙膨脹由減速轉為加速。直到去年，所有宇宙學數據均符合暗能量作為宇宙學常數的假設，這意味著宇宙應該持續加速膨脹。

但DESI的最新分析表明，當前宇宙膨脹加速程度較過去有所減弱，這與暗能量作為宇宙學常數的假設不符。相反，數據顯示，暗能量密度（單位空間內的暗能量含量）較45億年前已下降了約10%。

此次分析包括逾3000萬個星系與類星體的紅移數據，覆蓋宇宙110億年的歷史。儘管DESI數據的統計能力尚不足以完全否定暗能量的宇宙學常數屬性，但DESI成員、英國朴茨茅斯大學的Seshadri Nadathur預計，一旦DESI積累了7年數據並完成調查，這一宇宙常數將成為歷史。

The launch of the Euclid Space Telescope in 8 and the upcoming 0-meter Vera Rubin Observatory in Chile will further complement the relevant cosmic history data.(Li Muzi)