Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. See Article History. Learn More in these related Britannica articles:. Atoms can exist only because there is an excess of electrons, protons, and neutrons in the everyday world, with no corresponding positrons, antiprotons, and antineutrons. In this step both particles disappear and are replaced by two annihilation photons, each with an energy of 0.
Annihilation photons are similar to gamma rays in their ability to penetrate large distances of matter without interacting. They may undergo Compton or photoelectric…. Separate storage rings are sometimes used, in particular if the electrons and positrons are to have different energies. After annihilation, however, the ratio of the number of remaining protons to photons would be….
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Uh Oh. There was a problem with your submission. Please try again later. Using its specialized instrumentation which can make detailed measurements of a thousand galaxies at a time, BOSS took on a huge challenge — mapping the location of more than a million galaxies.
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Although the BOSS research team presented its early galaxy maps and beginning BAO measurements a year ago, this new data covers twice as much territory and gives an even more accurate measurement — including those to nearby galaxies. As of the present, these new BOSS findings would seem to be consistent with what we consider to be form of dark energy — a constant found throughout the history of the Universe.
Schlegel compares this six-number model to a pane of glass, which is pinned in place by bolts that represent different measurements of the history of the Universe. This unusual group located in the constellation of Taurus includes a pulsar which is orbited by a pair of white dwarf stars. But this new millisecond pulsar is the first to be detected with two white dwarfs. This close knit association, coupled with the fact the trio of stars is far denser than the Sun create the perfect conditions to examine the true nature of gravity.
Not only did the research team tackle a formidable amount of data, but they also took on the challenge of modeling the system. Leading the study, Archibald created the system simulation which predicts its motions. This principle is an important aspect of the theory of General Relativity, and states that the effect of gravity on a body does not depend on the nature or internal structure of that body.
Need a refresher on the equivalence principle? Thanks to mirrors left on the lunar surface, laser ranging measurements have been studied for years and provide the strongest constraints on the validity of the equivalence principle. Here the experimental masses are the stars themselves, and their different masses and gravitational binding energies will serve to check whether they all fall towards each other according to the Strong Equivalence Principle, or not. For those of us who remain forever fascinated by astronomy, nothing could spark our imaginations more than a cosmic curiosity.
What makes this dual star system of interest? Try the fact that the pair revolve completely around each other in a brief 18 minutes. Like other astronomical anomalies, AM CVn became the forerunner of a new class of stellar objects. It is a white dwarf, a sun-like star which has exhausted its fuel and collapsed to around the size of Earth.
Yet it also has a white dwarf companion — a very compact orb which is delivering matter to its neighbor. AM Canum Venaticorum is not alone, however. There are similar systems where the stellar pairs complete their rotations in about an hour and even as rapidly as five minutes! Can you imagine the crackling amount of energy a system like this produces?! Even though we have been aware of systems like AM CVn for almost five decades, no one is quite sure how they originate. Now, through the use of X-ray and optical observations, astronomers are taking a look at newly evolved double stars systems which one day might become a dueling duo dwarf.
Heading their list are two binary systems, J and J John Observatory 1. The top panel shows the current state of the binary that contains one white dwarf on the right with about one-fifth the mass of the Sun and another much heavier and more compact white dwarf about five or more times as massive unlike Sun-like stars, heavier white dwarfs are smaller.
As the pair of white dwarf stars whip around each other, they are releasing gravitational waves which constrict the orbit. In time, the heavier, diminutive dwarf will begin stripping material from its lighter, larger companion as seen in the middle panel. This material consumption will continue for perhaps a million years, or until the collected matter reaches a critical mass and releases a thermonuclear explosion.
Another scenario is the thermonuclear explosion could annihilate the larger white dwarf completely in what astronomers call a Type Ia supernova. An event like this is well-known and gives a measurement in standard candles for cosmic distance. However, chances are better the explosion will happen on the surface of the star — an event known as. Ia supernovae. Ia supernovae events have been recorded in other galaxies, J and J are the first binary stars which have the potential to erupt in.
The X-ray observations were needed to rule out the possibility that J and J contained neutron stars. Are AM CVn systems riding the gravitational wave? There are only six of them: radon, helium, neon, krypton, xenon and the first molecules to be discovered in space — argon. They are all odorless, colorless, monatomic gases with very low chemical reactivity. By observing in longer wavelengths of light than can be detected by the human eye, the scientists gave credence to current theories of how argon occurs naturally. When it comes to a star, they are hot and ignite the visible spectrum.
Even though we can see nebulae in visible light, what shows is the product of hot, excited gases, not the cold and dusty regions.
They map the dust in far-infrared with their spectroscopic observations. In this instance, the researchers were somewhat astounded when they found some very unusual data which required time to fully understand. The speed at which they can spin comes out at very specific, quantized, frequencies, which we can detect in the form of infrared light with our telescope.
According to the news release, elements can exist in varying forms known as isotopes. These have different numbers of neutrons in the atomic nuclei. When it comes to properties, isotopes can be somewhat alike to each other, but they have different masses. Because of this, the rotational speed is dependent on which isotopes are present in a molecule.
The only argon isotope which could spin like that was argon! In this case it just jumped out of our spectra. Is this instance of argon in a supernova remnant natural? You bet. Even though the discovery was the first of its kind, it is doubtless not the last time it will be detected. Now astronomers can solidify their theories of how argon forms. Current predictions allow for argon and no argon to also be part of supernova structure. However, here on Earth, argon is a dominant isotope, one which is created through the radioactive decay of potassium in rocks.
Noble gas research will continue to be a focus of scientists at UCL. As an amazing coincidence, argon, along with other noble gases, was discovered at UCL by William Ramsay at the end of the 19th century! I wonder what he would have thought had he known just how very far those discoveries would take us? Encompassing 1, maps of molecular clouds, this new research has found these building blocks of future suns to be encased in a sort of molecular hydrogen mist.
This ethereal mixture appears to be far denser than speculated and is found throughout the galactic disc. Stars form in the molecular clouds housed within all galaxies. These formations are vast areas of hydrogen molecules with masses which total from a thousand to several million times that of the Sun. When an area of the cloud folds under the weight of its own gravity, it collapses. Pressure and temperature rise and nuclear fusion begins.
A star is born. This exciting new research is changing the way astronomers think about starbirth regions. The picture that is emerging is quite different from what astronomers thought these clouds should be like. Not only does the enveloping gas play a critical part in star formation, but galaxy structure does as well. One galactic feature in particular is key — spiral arm structure.
They sweep slowly around the core area like hands on a clock and are more populated with stars than the remainder of the galactic disk.
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On the contrary, interactions between clouds, fog, and overall galactic structure appear to hold the key to whether or not a cloud will form new stars. Clouds feeling this reduced pressure are unlikely to form new stars. A study that needed such extensive observation time, and required both an interferometer to discern vital details and our 30 m antenna to put those details into a larger context, would not have been possible at any other observatory.
Next, we need to check that what we have found also applies to other galaxies. For our next steps, we hope to profit from both the extension NOEMA of the compound telescope on the Plateau de Bure and from the newly opened compound telescope ALMA in Chile, which will allow in-depth studies of more distant spiral galaxies. The survey has found that some nine billion years ago galaxies were capable of producing new stars in a fashion as orderly as game of checkers. Despite their young cosmological age, the galaxies show signs containing high amounts of dust enriched by heavier elements — a mature state.
Their research goals are to enlighten the scales of cosmic time in relationship with the environment, formation and evolution of massive galactic structures. When studying individual galaxies, they may be able to tell if their rate of growth can be attributed to large-scale environments. Information of this type can clarify what factors the early Universe structure may have contributed to the current form of local galaxies.
One of the data sets the team is focusing on is using the FMOS on the Subaru Telescope to chart out the distribution of more than a thousand galaxies which formed over nine billion years ago — a time when the Universe was hitting its star-formation peak. Why choose spectroscopy? This advanced fiber optics technology speaks for itself, collecting light over an area of sky equal in size to that of the Moon. The FMOS focuses on the near-infrared, filtering out unwanted emissions caused by warm temperatures and can acquire spectra from galaxies simultaneously with a wide field of coverage of 30 arc minutes at prime-focus.
By employing such a wide field of view, astronomers can squeeze in a wide range of objects in their local environments. This enables researchers to maximize information on star-forming regions, cluster formation, and cosmology. It is currently the most powerful instrument we have to study the large numbers of objects needed to understand galaxies of all sizes, shapes and masses — from the largest ellipticals to the smallest dwarfs.