Astronomers have obtained long-sought signals from some of the first stars in the universe, and determined that these pioneers only burned brightly in 654.38+0.8 billion years after the Big Bang.
For a long time, scientists have always suspected that dawn had already arrived in the universe before this; Theorists' models also predict many things. But so far, researchers have no evidence to support this view. Before this new study, the oldest stars can be traced back to 400 million years after BIGBANG. Zhu Judd Bowman, an astronomer at the School of Earth and Space Exploration of Arizona State University, said: Universe: The Big Bang only took 10 simple steps.
"This pushes our understanding of when and how stars form to the early days of the universe."
These very old stars are pioneers. Although they are composed of primitive hydrogen and helium, they started the continuous process of star birth and death, and finally injected heavy elements into the universe in hundreds of millions of years-rocky planets like the earth are composed of heavy elements.
"If you look at the origin of our universe," Bowman told Space Magazine, "the bottom of the ladder is the process of the first object forming and enriching the medium, which makes everything else possible."
In addition, the signals found by Bowman and his team are extremely strong. In fact, it is so strong that it implies that there may be an interaction between mysterious dark matter and "normal" matter that makes up stars, you and me, and everything we can see in the universe.
The sooner you screen the noise, the harder it is to use NASA's Hubble Space Telescope. First of all, there are fewer and fewer stars to find. Until 500 million years after the Big Bang, the universe was full of neutral hydrogen atoms, which were good at shading. The radiation from the first star will eventually split these atoms into their constituent elements, protons and electrons, producing a more transparent ionized plasma, but it will take some time. )
Therefore, Bowman and his colleagues adopted an indirect method to find the fingerprints that these early stars may have left on the cosmic background radiation (CMB), the ancient light left by BIGBANG. The idea is that ultraviolet radiation from stars will excite hydrogen atoms into different states, making them absorb CMB photons.
Theoretically, this drop in CMB signal should be detectable. Therefore, the research team built, calibrated and tested a radio antenna the size of a kitchen table, which they called "the experiment of detecting the global EoR (Re-ionization Age) characteristics (EDGES)", which was funded by the National Science Foundation (NSF).
EDGES Ground Radio Spectrometer of CSIRO murchison Radio Observatory in Western Australia. Then, they installed equipment at the murchison Radio Observatory (MRO) in Western Australia. MRO is located in a very quiet radio area and is maintained by the Commonwealth Scientific and Industrial Research Organization, Australia's national scientific institution.
The radio quiet aspect of the website is key, because the modeling work shows that Bowman and his colleagues are looking for signals that overlap with the dialing frequency of FM broadcasting. Researchers have to deal with all the background radio noise in the galaxy. "Amazing photos of our galaxy (gallery)"
"It is a huge technical challenge to carry out this kind of detection," Peter Kulczynski, project director of the National Science Foundation, who oversees the edge of funds, said in a statement that the noise source may be 65,438+00,000 times brighter than the signal. It's like trying to hear the hum of bird wings in a hurricane.
But the edge picked up this tiny flap and found the strongest tilt at the frequency of 78 MHz. Hydrogen will emit and absorb radiation with the wavelength equivalent to 1420 MHz, so the edge of the detected signal will be "red shifted"-the expansion of the universe will stretch it to a lower frequency. When these CMB photons are absorbed, the degree of this red shift tells the research team that the universe was born about 65.438+0.8 billion years later.
Bowman and his team reported these results in an online study in Nature today (February 28th).
Kuchinsky said that these researchers with small radio antennas in the desert have seen "farther distance than the most powerful space telescope, which opened a new window in the early universe".
Bowman said that the edge signal gradually disappeared in less than 1 100 million years, probably because X-rays emitted by supernovae, black holes and other objects significantly heated hydrogen atoms at this point.
It is the time axis of the universe, updated to show the time when the first star appeared (65.438+0.8 billion years after BIGBANG). (National Science Foundation, N.R. Fuller) The involvement of dark matter? ""The signal edge strength found is about twice as strong as the team expected. Bowman said that there are two possible explanations for this surprising intensity: one is that the early radio background is much stronger than scientists thought, and the other is that the hydrogen has obviously cooled down.
Bowman said that the research team prefers the second possibility because it is hard to imagine a process that can raise the radio background to the necessary level. It is also difficult to figure out what cools hydrogen, but there is a promising competitor: dark matter, a mysterious substance that accounts for 85% of the physical universe.
Dark matter neither absorbs nor emits light, so it cannot be directly seen (hence its name). Astronomers infer the existence of matter from its gravitational effect on "normal" matter, but they don't know what dark matter is. Most researchers believe that it is composed of undiscovered particles, axions and other hypothetical spots or weakly interacting large particles. "KDSP" and "KDSP" in a separate study in the same period of Nature Research by Rennan Barkana, an astrophysicist at Tel Aviv University, Israel, show that cold dark matter may absorb the energy in hydrogen and cool it. If this happens, "the mass of dark matter particles is no heavier than a few protons, which is far lower than the mass of weakly interacting massive particles usually predicted," Bakana wrote in his research.
If Bakana is right, Bowman and his team studied some strange physics and found important clues about the nature of dark matter. [Gallery: Dark Matter in the Universe]
"We are always looking for anything that can tell us more about what dark matter might be," Bowman said. If this is really confirmed and continues to be confirmed-the test is true and Lennon's hypothesis is true [and] the best explanation-then it is probably the first key to improve our understanding of the authenticity of dark matter.
The next step is to confirm the detection-this is the next step of early universe research, Bowman said. He and his team spent about two years verifying their findings and ruled out all possible alternative explanations. But to make this discovery rock solid, another research team needs to find this signal.
If so, astronomers can dig up more information, Bowman said. After all, now they know where to find it.
For example, he said, further research on sensitive radio telescope arrays should reveal more information about the nonstandard physics implied by signals and the nature of the first star in the universe.
At the same time, we also hope that we can