Quasars used to calculate the rate of expansion of the Universe
The question of how fast the Universe is expanding has puzzled astronomers for nearly a century. Over the years, various theories have emerged on the subject. It seems that scientists from California have come closer to solving this riddle by using a completely new way of measuring the.
The speed of the Universe’s expansion is the subject of heated debate in the scientific community. The entire spor refers to the Hubble constant’a – figures, ktora relates distance to the redshift of galaxies, i.e. their escape velocity. This is the value by which light was stretched during the subrolives on Earth through the expanding Universe.
Without accurate knowledge of Hubble's constant, astronomers cannot accurately determine the size of theoin distant galaxies, the age of the Universe or the history of cosmic expansion. But thanks to a pioneering way to measure the speed of space expansion, the compositeoł guided by astronomersow from the University of California – Los Angeles (UCLA) took a step toward ending this debate. In doing so, the researchers enlisted the help of the SDSS quasar J1206 + 4332.
So far, estimates for the Hubble constant'a range from 67 to 73 kilometersow per second per megaparsec, which means that two points in space 1 megaparsec (3.26 million light-years) away from each other at a speed of 67 to 73 kilometersow per second.
Most methods of obtaining the Hubble constant'a have two components: the distance to the source of theothe light source and the redshift of the light sourceolight source. Looking for the source of theolight source, from whichorego in their calculations has not yet been used by other researchers, led by Simon Birrer and his cooThe goal is to determine the Hubble constantociliated towards the quasarow, fountains of radiation, ktore power giant black holes. For their study, the researchers chose one specific subset of theor quasaroin – those whoohe light was curved by the gravity of the galaxies between the quasars and Earth. This gives astronomers the opportunity to observe dwoch imageoIn the same quasar.
The light from these twooch imageow reached Earth rotion by different paths. When the brightness of the quasar fluctuates, the two images flash one after the other, not at the same time. OpoThe time delay between the two flickering images, along with information about the gravitational field of the galaxy between us and the quasar, can be used to trace the path of light and determine the distance from Earth to the quasar and that galaxy. Knowing the redshift of the quasar and the galaxy, scientists were able to estimate how fast the Universe is expanding.
Researchers at UCLA had already used the technique to study non dwoch imagesoin the same quasar, and the four – four images of the quasar appear wokoł galaxies in the foreground. However, such images are rare. Much more common are quasars with subojn image. They can be observed about five times more often.
To demonstrate this technique, the researchers examined the sub-ojnie imaged quasar known as SDSS J1206 + 4332. They took data for the study from the Hubble Space Telescope'a, Gemini Observatory and W.M. Keck and the COSMOGRAIL (Cosmological Monitoring of Gravitational Lenses) network, whichoThe goal is to determine the Hubble constant'a.
Scientists have been taking pictures of quasars every day for several years to accurately measure opoThe time delay between images. Then, to get the best possible estimate of the Hubble's constant, they combined these data with data collected in the H0liCOW project of three earlyorially imaged quasars.
– The beauty of this measurement is that it is highly complementary and independent of the others, said Tommaso Treu, professor of physics and astronomy at UCLA, and cooauthor of the publication.
Based on their research, the scientists determined an estimate of the Hubble's constant of about 72.5 kilometersow per second per megaparsec, which is consistent with what other scientists have found in studies using as a key measurement of distance from supernovae – exploding stars in distant galaxies. However, both estimates are about 8 percent higher than those based on a faint glow called the microwave background radiation, whichore a relic from 380,000 years after the Big Bang, when light first moved freely through space.
– If there is a viable rothe difference between these values, it means that the Universe is a bit more complicated,” said Treu. On the other hand, he added, it can happen that one measurement – or all three – are wrong.
Scientists are now looking for new quasarsow to improve the precision of their measurement of the Hubble constant'a. Treu acknowledged that one of the most important lessons from the new research is that the subojnie imaged quasars give scientists many more useful sources ofolight sources to calculate the Hubble constant'a. For now, however, the compositeoł directed by scientistsow from UCLA is focusing its research on forty quadruple-imaged quasars because of their potential to provide even more useful information than that whichore can be obtained from subojnie imaged quasarow.
Sourceobackground: University of California – Los Angeles, fot. NASA Hubble Space Telescope/ Tommaso Treu/ UCLA/ Birrer et al.