Astronomy
Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe. Astronomy is one of the oldest sciences.
Astronomers of early civilizations performed methodical observations of the night sky, and astronomical artifacts have been found from much earlier periods.
However, the invention of the telescope was required before astronomy was able to develop into a modern science.
Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, and even, at one time, astrology, but professional astronomy is nowadays often considered to be identical with astrophysics.
Since the 20th century, the field of professional astronomy split into observational and theoretical branches.
Observational astronomy is focused on acquiring and analyzing data, mainly using basic principles of physics.
Theoretical astronomy is oriented towards the development of computer or analytical models to describe astronomical objects and phenomena.
The two fields complement each other, with theoretical astronomy seeking to explain the observational results, and observations being used to confirm theoretical results. Amateur astronomers have contributed to many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena. The most frequently studied star is the Sun, a typical main-sequence dwarf star of stellar class G2 V, and about 4.6 Gyr in age.
The Sun is not considered a variable star, but it does undergo periodic changes in activity known as the sunspot cycle.
The study of stars and stellar evolution is fundamental to our understanding of the universe.
The astrophysics of stars has been determined through observation and theoretical understanding; and from computer simulations of the interior. Star formation occurs in dense regions of dust and gas, known as giant molecular clouds.
When destabilized, cloud fragments can collapse under the influence of gravity, to form a protostar.
A sufficiently dense, and hot, core region will trigger nuclear fusion, thus creating a main-sequence star. Almost all elements heavier than hydrogen and helium were created inside the cores of stars.
How The First Stars In The Universe Came Into Existence
The first primordial stars began as tiny seeds that grew rapidly into stars one hundred times the mass of our own Sun. Seen here in this artist's impression, swirling clouds of hydrogen and helium gasses are illuminated by the first starlight to shine in the Universe. In the lower portion of the artwork, a supernova explodes, ejecting heavier elements that will someday be incorporated into new stars and planets. (Credit: Image courtesy of David A. Aguilar (CfA) via Science/AAAS)
ScienceDaily (Aug. 1, 2008) — Researchers believe that our universe began with the Big Bang about 13 billion years ago, and that soon after that event, matter began to form as small dust grains and gases.
How the first stars formed from this dust and gas has been a burning question for years, but a state-of-the-art computer simulation now offers the most detailed picture yet of how these first stars in the universe came into existence, researchers say.
The composition of the early universe was quite different from that of today, and the physics that governed the early universe were also somewhat simpler. Dr. Naoki Yoshida and colleagues in Japan and the U.S. incorporated these conditions of the early universe, sometimes referred to as the "cosmic dark ages," to simulate the formation of an astronomical object that would eventually shine its light into this darkness.
The result is a detailed description of the formation of a protostar -- the early stage of a massive primordial star of our universe -- and the researchers' computer simulation, which has been called a "cosmic Rosetta Stone," sets the bar for further investigation into the star formation process. The question of how the first stars evolved is so important because their formations and eventual explosions provided the seeds for subsequent stars to come into being.
According to their simulation, gravity acted on minute density variations in matter, gases, and the mysterious "dark matter" of the universe after the Big Bang in order to form this early stage of a star -- a protostar with a mass of just one percent of our sun. The simulation reveals how pre-stellar gases would have actually evolved under the simpler physics of the early universe to form this protostar. Dr. Yoshida's simulation also shows that the protostar would likely evolve into a massive star capable of synthesizing heavy elements, not just in later generations of stars, but soon after the Big Bang.
"This general picture of star formation, and the ability to compare how stellar objects form in different time periods and regions of the universe, will eventually allow investigation into the origins of life and planets," said Lars Hernquist, a Professor of Astronomy at Harvard University and a co-author of this latest report. "The abundance of elements in the universe has increased as stars have accumulated," he says, "and the formation and destruction of stars continues to spread these elements further across the universe. So when you think about it, all of the elements in our bodies originally formed from nuclear reactions in the centers of stars, long ago."
Their simulation of the birth of a protostar in the early universe signifies a key step toward the ambitious goal of piecing together the formation of an entire primordial star and of predicting the mass and properties of these first stars of the universe. More powerful computers, more physical data, and an even larger range will be needed for further calculations and simulations, but these researchers hope to eventually extend this simulation to the point of nuclear reaction initiation -- when a stellar object becomes a true star.
"Dr. Yoshida has taken the study of primordial star formation to a new level with this simulation, but it still gets us only to the halfway point towards our final goal. It is like laying the foundation of a skyscraper," said Volker Bromm, Assistant Professor of Astronomy at the University of Texas, Austin and the author of a companion article. "We must continue our studies in this area to understand how the initially tiny protostar grows, layer by layer, to eventually form a massive star. But here, the physics become much more complicated and even more computational resources are needed."
Astronomers Witness a Star Being Born
Astronomers caught a glimpse of a future star just as it is being born out of the surrounding gas and dust, in a star-forming region similar to the one pictured above. (Credit: NASA, ESA)
ScienceDaily (June 18, 2010) — Astronomers have glimpsed what could be the youngest known star at the very moment it is being born. Not yet fully developed into a true star, the object is in the earliest stages of star formation and has just begun pulling in matter from a surrounding envelope of gas and dust, according to a new study that appears in the current issue of the Astrophysical Journal.
The study's authors -- who include astronomers from Yale University, the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Astronomy in Germany -- found the object using the Submillimeter Array in Hawaii and the Spitzer Space Telescope. Known as L1448-IRS2E, it's located in the Perseus star-forming region, about 800 light years away within our Milky Way galaxy.
Stars form out of large, cold, dense regions of gas and dust called molecular clouds, which exist throughout the galaxy. Astronomers think L1448-IRS2E is in between the prestellar phase, when a particularly dense region of a molecular cloud first begins to clump together, and the protostar phase, when gravity has pulled enough material together to form a dense, hot core out of the surrounding envelope.
"It's very difficult to detect objects in this phase of star formation, because they are very short-lived and they emit very little light," said Xuepeng Chen, a postdoctoral associate at Yale and lead author of the paper. The team detected the faint light emitted by the dust surrounding the object.
Most protostars are between one to 10 times as luminous as the Sun, with large dust envelopes that glow at infrared wavelengths. Because L1448-IRS2E is less than one tenth as luminous as the Sun, the team believes the object is too dim to be considered a true protostar. Yet they also discovered that the object is ejecting streams of high-velocity gas from its center, confirming that some sort of preliminary mass has already formed and the object has developed beyond the prestellar phase. This kind of outflow is seen in protostars (as a result of the magnetic field surrounding the forming star), but has not been seen at such an early stage until now.
The team hopes to use the new Herchel space telescope, launched last May, to look for more of these objects caught between the earliest stages of star formation so they can better understand how stars grow and evolve. "Stars are defined by their mass, but we still don't know at what stage of the formation process a star acquires most of its mass," said Héctor Arce, assistant professor of astronomy at Yale and an author of the paper. "This is one of the big questions driving our work."
Other authors of the paper include Qizhou Zhang and Tyler Bourke of the Harvard-Smithsonian Center for Astrophysics; and Ralf Launhardt, Markus Schmalzl and Thomas Henning of the Max Planck Institute for Astronomy.
Posted by Lydia on August 29th, 2010

“… as large as the full moon … closest to Earth since (insert date) … will not be able to view again until the year (insert year) …”
The astronomy community has advised readers since 2004 of this erroneous post, yet every year it comes around again to fool readers into thinking Mars will be as bright as the Moon.
I can think of one positive thing about this silly falsity: it gets people outside at night to see if it is true.
My questions to the public:
1. Don’t you think that if an object in the sky was “as bright as the full Moon” you would be able to see it in the daytime as well as at night?
2. If there was an object as bright as this headed toward us, wouldn’t you be hugging your loved ones and asking forgiveness of those you may have wronged?
Let’s explore a few facts about Mars in reference to its proximity to our home planet.
Mars’s orbit brings it close to earth every two years. This year, however, is not one of them.
In 2003, Mars was 35 million miles (56 million kilometres) away from Earth, which was its closest in 60,000 years. It was 85 times brighter in comparison
as viewed through a telescope, yet a far cry from “full Moon” brightness. Mars’s orbit brings it this close to us
every 15 to 17 years and astronomers and those with telescopes get all warm and excited and send out notices for public viewing of this phenomena which is referred to as
perihelic opposition. To the unaided eye, however, Mars appeared as a reddish hued star in the night sky and if you hadn’t known about it, the event would have gone unnoticed. In October 2005, Mars made another close approach and again in December 2007, albeit not as spectacular astronomically speaking, as the 2003 observing opportunity which we will have the chance to experience again in 2018.
Next year we will surely see the reappearance of the Mars hoax email. Now that you know the facts, please delete it, yet feel free to roam outside and enjoy our night sky at any time during the year.