NASAのインスタグラム(nasagoddard) - 4月27日 10時46分

The universe is getting bigger every second. The space between galaxies is stretching, like dough rising in the oven. But how fast is the universe expanding? As Hubble and other telescopes seek to answer this question, they have run into an intriguing difference between what scientists predict and what they observe.

This is a ground-based telescope's view of the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The inset image, taken by the Hubble Space Telescope, reveals one of many star clusters scattered throughout the dwarf galaxy. The cluster members include a special class of pulsating star called a Cepheid variable, which brightens and dims at a predictable rate that corresponds to its intrinsic brightness. Once astronomers determine that value, they can measure the light from these stars to calculate an accurate distance to the galaxy. When the new Hubble observations are correlated with an independent distance measurement technique to the Large Magellanic Cloud (using straightforward trigonometry), the researchers were able to strengthen the foundation of the so-called "cosmic distance ladder." This "fine-tuning" has significantly improved the accuracy of the rate at which the universe is expanding, called the Hubble constant.

Credit: NASA, ESA, A. Riess (STScI/JHU) and Palomar Digitized Sky Survey

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