of dwarf galaxies are typically billions of light years away, so these occurred
billions of years ago. However, some of these galaxies analyzed in the new
study are relatively close, only 166 million light years away, which means that
the process now observed in these has been in quite recent; speaking cosmically:
only 166 million years ago.
Astronomers have known for decades that these dwarf galaxies are
pulling each other. The classic spiral forms have been stretched considerably,
casting long strips of gas and dust. The brightest object in the image obtained
by the Hubble Space Telescope actually corresponds to two
colliding galaxies. The whole system shines down markedly, due to the massive
and stormy birth of many stars. These births are triggered by the compression of
hydrogen gas exerted by close encounters between galaxies. Under these
conditions, hydrogen is more easily concentrated in clumps from which stars are
The Hubble observations have added important insights into the history of
this group interaction, allowing astronomers to determine when the meeting
began, and predict the future merger.The researcher have found the oldest stars
in a few
globular clusters and old dating back some ten billion years ago. Therefore, the
system is long, and has not yet resulted in a large elliptical galaxy.
Most other dwarf galaxies as they already went through this phase of
interactions during billions of years ago. Instead, these nearby galaxies are
grouped closely for the first time. This meeting has been under way for a few
hundred million years at most, a blink in cosmic history. This is an extremely
rare local example of what was a fairly common event in the archaic and distant
The astronomer Sarah Gallagher of the University of Western Ontario, is
the principal investigator of the study.
In an attempt to solve the problem of “Lost Dwarf galaxies”, two astronomers used the WM Keck Observatory to study a population of galaxies darker and lighter mass than all existing ones. Each composed by a 99 percent of dark matter. The results suggest that the problem of the Lost Dwarf galaxies is not as severe as previously thought, and may have been fully resolved.“It appears that the galaxies which are very small and extremely difficult to perceive- exist in abundance than we thought,” said Marla Geha, co-author of the study and researcher at the Hertzberg Institute of Astrophysics in Canada. “IfÂ you had asked me last year whether these small galaxies are much darker, I would have said no. I’m surprised that so many have now been discovered tiny galaxies dominated by dark matter.”
The riddle of the Lost Dwarf galaxies comes from a prediction model of the “Cold Dark Matter” which explains the growth and evolution of the universe. He predicts that large galaxies like the Milky Way should be surrounded by a swarm of no less than several hundreds of galaxies, although much smaller, known as “dwarf galaxies.”Other researchers also explained why a few tiny galaxies around the Milky Way are too rich in dark matter, the invisible stuff that makes up most of the matter in the universe. The key idea behind this seems to be the presence of bigger, brighter galaxies next door. Simulations indicate that million-degree coronas around these larger galaxies could have took away much of the visible gas in their young neighbors while leaving the dark material behind. Many scientists believe that all galaxies large and small should have started out the sameâ€”as a ball of dark matter with a disk of visible matter in the center. But some small galaxies, which we termed as â€œLost Dwarf Galaxiesâ€,contain roughly 100 times more dark matter per star than the Milky Way and are a million times less luminous. They also tend to cluster around bigger galaxies such as our own. In Â some new simulations of galaxy formation, Â it is revealed that, 10 billion years ago, the darkest of today’s â€œDwarf Galaxiesâ€ (such as Draco, Ursa Minor and Andromeda IX) were forming around big galaxies from the same mix of visible gas and dark matter, much like planets would form around a star. But they happened to get pulled into orbit around the central galaxy earlier than their counterparts. Once there, according to these recent simulations, shocks from the central galaxy’s gravity, and pressure from the hot corona around it, combined to knock loose most of the smaller galaxies’ shimmering gas. Ultraviolet radiation, which dominated the universe at the time, would have heated these small onesâ€™ visible gas, leaving it weakly attracted to the little galaxies and thus easy to scrape away.
The researchers might have done a good job of simulating all of the relevant physics and setting the orbits of the dwarfs; but they made the case that the Milky Way has very likely stripped the gas (and the ‘life’) out of many of the dwarf
galaxies we see around us.
Josh Simon (California Institute of Technology) and Geha used the Keck II telescope 10 meters with the DEIMOS spectrograph to conduct follow-up studies of eight new dwarf galaxies discovered recently. The results allowed the duo to calculate precisely the total mass of each galaxy.
To their surprise, each system was among the smallest so far measured, 10,000 times smaller than the Milky Way. So scientists now know that dwarf galaxies can be even smaller than what was estimated as possible.
The formations of galaxies are so small that it is not an easy phenomenon to explain from the theoretical point of view. It is unclear how the stars could form in galaxies so small. Measurements were made of 814 stars in the eight dwarf galaxies in the WM Keck Observatory. It was found that those stars are moving much more slowly than any other known galaxy (about 4 to 7 kilometers per second). For reference, the Sun orbits the center of the Milky Way at an approximate speed of 220 kilometers per second.
One implication of these results is the possibility of several hundred completely dark galaxies right here in the cosmic neighborhood of the Milky Way, which are not discovered yet. The next challenge for astronomers is to find a way to detect its presence. In the meantime, space is still the best place to detect the effects of dark matter and narrow down the constraints on what sort of particles dark matter might be. The newfound dwarf companions to the Milky Way are now presenting a rare opportunity to learn details about how dark matter behaves on a relatively small scale very close to home.
The current most favored theory is that it is some sort of particle that interacts only extremely rarely with normal matter in any other way than tugging its gravity. Physicists hope to settle the question in the next few years by possibly creating dark matter particles in the worldâ€™s largest particle accelerator, the Large Hadron Collider (LHC), a particle physics laboratory in Geneva.
There might be several ways to look at larger-scale distribution of dark matter. Already hundreds of models are in existence to look at the overall distribution of dark matter in the universe, which help to make sense of the structure of the universe in the largest scale. But the predictions of those models can be quite different for smaller scales.
The massif is divided into five channels that separate the Mediterranean climate zones in the north of the arid zone of the Sahara Desert to the south. Three of these channels are located in Morocco: High Atlas (covered with snow and visible in the lower left corner), the Middle Atlas (which appears as two spots of snow on the north-east of the High Atlas) and the Anti-Atlas (not visible here but located in the south-west of the High Atlas).
The High Atlas has the highest peaks in North Africa, including Mount Toubkal, which exceeds 4000 m altitude. Despite high temperatures of summer, these peaks remain snow cover for most of the year.
The Tellien Atlas and Saharan Atlas in Algeria are located (visible to the east of the Upper and Middle Atlas). The Atlas Tellien stretches along the Mediterranean coast and receives substantial rainfall which he was sheltering many fertile valleys. It extends to Tunisia (not shown here).
South AlgÃ©rien, below the Saharan Atlas (south of the Atlas Tellien) does so receives no precipitation and is part of the Sahara desert (which covers the lower part of the image).
Other elements are also visible in the image, including the Mediterranean Sea (top right) and the Atlantic Ocean (left), connected by the Straits of Gibraltar and the southern tip of Spain ( in the upper left).
This image was taken on 30 January 2009 by the camera Meris (Medium Resolution Imaging Spectrometer) Envisat working in full resolution mode, which allows to distinguish details of 300 m to the ground.
In Space with a Little HOBO
Astronauts working in spacesuits to build the Space Station may get even colder than the suit designers imagined. Measuring the effects of extremely low temperatures on astronauts was the first step in making a better space suit. (more…)
High school physics and chemistry teacher David Byrum has always been an innovator, so when online courses came to his attention, he took advantage of this new learning format. Winner of the Arizona Presidential Award for Excellence in Science Education (1988) and a National Science Teacher’s Association National Exemplar award for his chemistry course (1984), Byrum takes his work seriously. For Byrum, distance leaning was the only way to take special-interest graduate-level courses that helped him (more…)
Chemistry is a course that explores the properties of substances and the changes that substances undergo. The student will investigate the following:
Â· Atomic Structure Â· Â· Matter and Energy Â· Â· Interactions of Matter Â· Â· Properties of Solutions ” including Acids and BasesÂ· (more…)
Introduction/Purpose: I wanted to know if I could make magnetism.
Hypothesis/Questions: Is it possible to create magnetism using man-made materials? If iron-bearing metal is subject to an electric current, then magnetism will be produced.
Materials: a 6-volt battery, 10 feet of wire, a metal rod, a switch, and paper clips
Procedure: I went to Home Depot and I bought the materials. When I got home I got I got the materials out. I made the project in less than a day.
Results/Conclusion: The experiment shows that the hypothesis is true: When iron-bearing metal is subject to an electric current, then magnetism will be produced. It seems logical that the stronger the electric current, the stronger the magnetic force.
This image radar due to satellite Envisat shows the eastern part of ‘Ellesmere Island (left), the most northern Canadian islands and portions of the northwest coast of Greenland (right), the largest island the world. (more…)
Posted on 20. Jan, 2010 by in Earth Sciences
Earth in the
Welcome to Issue #1
As a long-time admirer of The Universe in the Classroom, a publication of the
Astronomical Society of the Pacific, I feel especially privileged to welcome you to this first issue of The Earth in the Classroom.
We hope to contribute to the Earth sciences in the same way that The Universe in the Classroom has contributed to astronomy. Our goal is to help you stay up-to-date on some of the most fascinating topics on Earth, under the ground and in our planet’s atmosphere.
The first thing I found out as I was running some
simulations is that if the simulation speed is too high, the program calculates the orbits extremely inaccurately as is visible in this picture (top) of the (more…)