An example of a cosmic-ray extensive air shower recorded by the Subaru Telescope. The highlighted tracks, which are mostly aligned in similar directions, show the shower particles induced from a high-energy cosmic ray. Credit: NAOJ/Hyper Suprime-Cam (HSC) Collaboration
Cosmic rays are a fascinating and potentially hazardous phenomenon. These high-energy particles typically consist of protons that have been stripped of their electrons and accelerated to nearly the speed of light. When these rays collide with Earth’s atmosphere, an enormous amount of secondary particles known as an “air shower” results. Ordinarily, these showers are a source of frustration for astronomers since they leave “tracks” on telescope images that obscure the celestial objects (asteroids, stars, galaxies, exoplanets, etc.) being observed.
However, a research team from the National Astronomical Observatory of Japan (NAOJ) and Osaka Metropolitan University has found a new application for these energetic particles. Using a novel method, they could observe these extensive cosmic-ray air showers with unprecedented precision. The key to their method is the Subaru Prime Focus Camera (Suprime-Cam) mounted on the Subaru Telescope atop the Mauna Kea volcano in Hawaii. This method and the team’s findings could provide a new method for studying the Universe’s most energetic particles.
An artist's illustration of the Universe's first stars, called Population 3 stars. Pop 3 stars would have been much more massive than most stars today, and would have burned hot and blue. Their lifetimes would've been much shorter than stars like our Sun. Credit: Wikimedia Commons
Until recently, astronomers could not observe the first stars and galaxies that formed in the Universe. This occurred during what is known as the “Cosmic Dark Ages,” a period that took place between 380,000 and 1 billion years after the Big Bang. Thanks to next-generation instruments like the James Webb Space Telescope (JWST), improved methods and software, and updates to existing observatories, astronomers are finally piercing the veil of this era and getting a look at how the Universe as we know it began.
This includes new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, which obtained images of a stellar nursery inside a galaxy roughly 13.2 billion light-years away in the constellation Eridanus. This galaxy has a redshift value of more than 8.3, corresponding to when the Universe was less than 1 billion years old. The images discerned the sites of star formation and possible star death inside a nebula (MACS0416_Y1) located within this galaxy. This represents a major milestone for astronomy as this is the farthest distance such structures have been observed in our Universe.
Artist's impression of ice age Earth at glacial maximum. Credit: Wikipedia Commons/Ittiz
Earth experiences seasonal changes because of how its axis is tilted (23.43° relative to the Sun’s equator), causing one hemisphere to always be tilted towards the Sun (and the other away) for different parts of the year. However, because of gravitational interactions between the Earth, Sun, Moon, and other planets of the Solar System, Earth has experienced changes in its orientation (obliquity) over the course of eons. This has led to significant changes in Earth’s climate, particularly the recession and expansion of ice sheets due to significant variations in the distribution of sunlight and seasonal changes.
These warming and cooling periods are known as interglacial and glacial periods (“ice ages”). Another interesting change is how the glacial-interglacial cycle has become slower with time. While scientists have long suspected that astronomical forces are responsible, they have only recently been able to test this theory. In a recent study, a team of Japanese researchers reproduced the cycle of glacial periods during the early Pleistocene Epoch (1.6 to 1.2 million years ago) using an improved computer model that confirmed astronomical forces were responsible.
Artist’s Impression of the “Tadpole” Molecular Cloud and the black hole at the gravitational center of its orbit. Credit: Keio University
In the 1930s, astrophysicists theorized that at the end of their life cycle, particularly massive stars would collapse, leaving behind remnants of infinite mass and density. As a proposed resolution to Einstein’s field equations (for his Theory of General Relativity), these objects came to be known as “black holes” because nothing (even light) could escape them. By the 1960s, astronomers began to infer the existence of these objects based on the observable effects they have on neighboring objects and their surrounding environment.
Despite improvements in instruments and interferometry (which led to the first images of M87 and Sagittarius A*), the study of black holes still relies on indirect methods. In a recent study, a team of Japanese researchers identified an unusual cloud of gas that appears to have been elongated by a massive, compact object that it orbits. Since there are no massive stars in its vicinity, they theorize that the cloud (nicknamed the “Tadpole” because of its shape) orbits a black hole roughly 27,000 light-years away in the constellation Sagittarius.
Japanese astronomers have captured images of an astonishing 1800 supernovae. 58 of these supernovae are the scientifically-important Type 1a supernovae located 8 billion light years away. Type 1a supernovae are known as ‘standard candles’ in astronomy.
Researchers at the CSIRO have managed to pinpoint the location of an FRB for the first time, yielding valuable information about our universe. Credit: csiro.au
In July of 2012, researchers at the CERN laboratory made history when they announced the discovery of the Higgs Boson. Though its existence had been hypothesized for over half a century, confirming its existence was a major boon for scientists. In discovering this one particle, the researchers were also able to confirm the Standard Model of particle physics. Much the same is true of our current cosmological model.
For decades, scientists been going by the theory that the Universe consists of about 70% dark energy, 25% dark matter and 5% “luminous matter” – i.e. the matter we can see. But even when all the visible matter is added up, there is a discrepancy where much of it is still considered “missing”. But thanks to the efforts of a team from the Commonwealth Scientific and Industrial Research Organization (CSIRO), scientists now know that we have it right.
This began on April 18th, 2015, when the CSIRO’s Parkes Observatory in Australia detected a fast radio burst (FRB) coming from space. An international alert was immediately issued, and within a few hours, telescopes all around the world were looking for the signal. The CSIRO team began tracking it as well with the Australian Telescope Compact Array (ATCA) located at the Paul Wild Observatory (north of Parkes).
Image showing the field of view of the Parkes radio telescope (left) and zoom-ins on the area where the signal came from (left). Credit: D. Kaplan (UWM), E. F. Keane (SKAO).
With the help of the National Astronomical Observatory of Japan’s (NAOJ) Subaru telescope in Hawaii, they were able to pinpoint where the signal was coming from. As the CSIRO team described in a paper submitted to Nature, they identified the source, which was an elliptical galaxy located 6 billion light years from Earth.
This was an historic accomplishment, since pinpointing the source of FRBs have never before been possible. Not only do the signals last mere milliseconds, but they are also subject to dispersion – i.e. a delay caused by how much material they pass through. And while FRBs have been detected in the past, the teams tracking them have only been able to obtain measurements of the dispersion, but never the signal’s redshift.
Redshift occurs as a result of an object moving away at relativistic speeds (a portion of the speed of light). For decades, scientists have been using it to determine how fast other galaxies are moving away from our own, and hence the rate of expansion of the Universe. Relying on optical data obtained by the Subaru telescope, the CSIRO team was able to obtain both the dispersion and the redshift data from this signal.
As stated in their paper, this information yielded a “direct measurement of the cosmic density of ionized baryons in the intergalactic medium”. Or, as Dr. Simon Johnston – of the CSIRO’s Astronomy and Space Science division and the co-author of the study – explains, the team was not only to locate the source of the signal, but also obtain measurements which confirmed the distribution of matter in the Universe.
“Until now, the dispersion measure is all we had,” he said. “By also having a distance we can now measure how dense the material is between the point of origin and Earth, and compare that with the current model of the distribution of matter in the Universe. Essentially this lets us weigh the Universe, or at least the normal matter it contains.”
Dr. Evan Keane of the SKA Organization, and lead author on the paper, was similarly enthused about the team’s discovery. “[W]e have found the missing matter,” he said. “It’s the first time a fast radio burst has been used to conduct a cosmological measurement.”
As already noted, FRB signals are quite rare, and only 16 have been detected in the past. Most of these were found by sifting through data months or years after the signal was detected, by which time it would be impossible for any follow-up observations. To address this, Dr. Keane and his team developed a system to detect FRBs and immediately alert other telescopes, so that the source could be pinpointed.
Artists impression of the SKA-mid dishes in Africa shows how they may eventually look when completed. Credit: skatelescope.org
It is known as the Square Kilometer Array (SKA), an international effort led by the SKA Organization to build the world’s largest radio telescope. Combining extreme sensitivity, resolution and a wide field of view, the SKA is expected to trace many FRBs to their host galaxies. In so doing, it is hoped the array will provide more measurements confirming the distribution of matter in the Universe, as well as more information on dark energy.
In the end, these and other discoveries by the SKA could have far-reaching consequences. Knowing the distribution of matter in the universe, and improving our understanding of dark matter (and perhaps even dark energy) could go a long way towards developing a Theory Of Everything (TOE). And knowing how all the fundamental forces of our universe interact will go a long way to finally knowing with certainty how it came to be.
These are exciting time indeed. With every step, we are peeling back the layers of our universe!
Spectacular photo of Comet ISON taken Nov. 15 from Charleston, Rhode Island, USA showing the recent outburst. Click to enlarge. Credit: Scott MacNeill
Comet ISON — that bright comet last year that broke up around Thanksgiving weekend — included two forms of nitrogen in its icy body, according to newly released observations from the Subaru Telescope.
Of the two types found, the discovery of isotope 15NH2 was the first time it’s ever been seen in a comet. Further, the observations from the Japanese team of astronomers show “there were two distinct reservoirs of nitrogen [in] the massive, dense cloud … from which our Solar System may have formed and evolved,” stated the National Astronomical Observatory of Japan.
Besides being pretty objects to look at, comets are considered valuable astronomical objects because they’re a sort of time capsule of conditions early in the universe. The “fresh” comets are believed to come from a vast area of icy bodies called the Oort Cloud, a spot that has been relatively untouched since the solar system formed about 4.6 billion years ago. Spying elements inside of comets can give clues as to what was present in our neighborhood when the sun and planets were just coming to be.
“Ammonia (NH3) is a particularly important molecule, because it is the most abundant nitrogen-bearing volatile (a substance that vaporizes) in cometary ice and one of the simplest molecules in an amino group (–NH2) closely related to life. This means that these different forms of nitrogen could link the components of interstellar space to life on Earth as we know it,” NAOJ stated.
You can read more details about the finding at the NAOJ website, or in Astrophysical Journal Letters.
