The rate at which the universe is expanding, known as Hubble constantIt is one of the basic criteria for understanding the evolution of the universe and its ultimate fate. However, a persistent difference called the “Hubble potential” is observed between the value of the constant measured by a wide range of independent distance indices and its value expected from the glow of light. the great explosion.
Before Hubble’s launch in 1990, the expansion rate of the universe was so uncertain that astronomers were not sure whether the universe had been expanding for a long time or not. 10 billion or 20 billion years. This is because a faster expansion rate will lead to a younger age for the universe, and a slower expansion rate will lead to an older age for the universe.
Hubble has better wavelength resolution than any ground-based telescope because it is above the hazy effects of Earth’s atmosphere. As a result, individual Cepheid variable stars can be identified – which has given the most accurate distance measurements for more than a century because it is unusually bright – which is more than a hundred million light-years away and measures the time interval over which its brightness changes.
“but, We must also look at the Cepheids in the near-infrared part of the spectrum to see the light Which passes unscathed through the intervening dust. “Dust absorbs and scatters blue optical light, making distant objects appear faint and tricking us into thinking they are farther away than they are,” Adam Rees of Johns Hopkins University, who led the new study, explains in a statement. .
Unfortunately, Hubble’s view of red light is not as sharp as blue, so light from Cepheids mixes with other stars in its field of view.
“but, Sharp infrared vision is one of the James Webb Space Telescope’s superpowers. “Thanks to its large mirror and sensitive optics, it can easily separate Cepheid light from neighboring stars with little mixing,” Rees explains.
In the first year of Webb’s operations, observations of the Cepheids discovered by Hubble were combined in two steps along what is known as the cosmic distance ladder: a series of different ways of making distance measurements to increasingly larger objects.
Webb’s measurements significantly reduced the noise in Cepheid measurements due to the observatory’s precision. At wavelengths near infrared. Observations of more than 320 cepheid stars confirmed that previous Hubble Space Telescope measurements were accurate, although they were noisier.
“Webb’s measurements provide the strongest evidence to date that systematic errors in Hubble’s Cepheid photometry do not play a significant role in the current Hubble strain. As a result, the most interesting possibilities remain on the table, and the mystery of Hubble’s strain deepens.”
With information from Europa Press