[이광식의 천문학+] The speed of the “secret” of the expansion of the universe .. as discovered by the Hubble telescope

▲ Based on Hubble Space Telescope data, this set of images shows galaxies containing Cepheid variables and supernovae. These things help to find the exponent for the expansion of the universe. / NASA, European Space Agency, Adam Rees


Scientists have been able to obtain more accurate measurements of the expansion of the universe thanks to data collected by the Hubble Space Telescope over the past few decades.

A new analysis of data from the 32-year-old Hubble Space Telescope continues the long-running search for how fast and how fast the universe is expanding.

The number that astronomers use to measure the expansion of the universe is called the Hubble constant. Here, the term “Hubble” does not refer to the Hubble telescope, but rather to Edwin Hubble, the astronomer who first measured the expansion of the universe index in 1929.

However, it is difficult to determine the value of the Hubble constant with certainty when looking at other values ​​published by the various astronomical observatories observing different regions of the universe. The new study gives confidence that Hubble’s latest efforts, while different from other observatories, are accurate measurements of the expansion of the current universe.

The new study confirms previous estimates of the rate of expansion based on Hubble observations, which show an expansion of about 73 kilometers per megaparsec. A megaparsec is a measure of distance equivalent to one million parsecs, or 3.26 million light-years.

In a statement released on the 19th (local time), the National Aeronautics and Space Administration (NASA) quoted Nobel Prize winner and lead author on the research Adam Reese as saying in a statement: The unfortunate lottery. Chances are you could be wrong because that’s only one in a million.”

Reese is affiliated with the Space Telescope Science Institute (STScI), which directs Hubble and Johns Hopkins University in Baltimore, Maryland.

Ries and his colleagues were awarded the Nobel Prize in 2011 after Hubble and other observatories confirmed that the universe is expanding rapidly. Reiss described Hubble’s latest study as a “masterpiece”. Because it really gave the answer based on the entire history of the Hubble telescope, that is, 32 years of space research.

The Hubble data accurately recorded the observed expansion rate in a program called SH0ES (Supernova, H0, for the dark-energy equation of state). NASA said the data set is two times larger than previously measured samples and also includes more than 1,000 Hubble orbits. The new measurements are also eight times more accurate than Hubble’s performance predictions.

Efforts to measure how fast the universe is expanding usually focus on two distance markers. The first is Cepheid, a variable star that brightens and dims at a constant rate. Its usefulness has been known since its discovery in 1912 by deaf astronomer Henrietta Swan Lipt.

Cephalopods are useful for measuring the distance between the Milky Way and nearby galaxies. A Type 1a supernova is used to measure larger distances. Since this supernova has a constant luminosity (intrinsic brightness), calculating the apparent luminosity visible through the telescope can accurately estimate the distance to the object.

“The team used Hubble to measure 42 supernovae,” NASA said in the new study. “They appear to be exploding at a rate of about one per year, so Hubble recorded as many supernovae as possible to measure the expansion of the universe.”

However, despite these various efforts, the rate of expansion of the universe is still not completely constant. According to the new study, Hubble, as mentioned earlier, measures about 73 kilometers per megaparsec, but when observed in deep space, it slows down to about 67.5 kilometers per megaparsec.

Deep space observations are mainly based on measurements from the Planck spacecraft, which observed the cosmic microwave background radiation, the “echo” of the Big Bang that formed the universe. NASA has not been able to figure out why astronomers have the two different values, but some suggest they may need to reconsider the basic physics.

“I don’t really care about the rate of inflation specifically, but I want to use it to understand the universe,” says Reiss, who says it’s better to think about what the expansion rate of the universe means than to look at it. It’s an “accurate value for now,” he said in a NASA statement.

The James Webb Space Telescope is expected to make more measurements in the next 20 years. According to NASA, James Webb said that Cepheid and Type 1a supernovae “will be seen at greater distances and with greater precision than Hubble can.” It could improve the value of the expansion of the universe observed by the Hubble telescope more accurately.

The papers based on the research will be published in The Astrophysical Journal. A pre-printed version is available in the archive (arXiv.org).

Kwang Sik Lee, Science columnist joand999@naver.com

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