Our Milky Way Galaxy spiral becomes a hazy band of light as viewed in the bright, dim night-time sky on Earth. This dazzling band of nebulous light, extending from horizon to horizon, is created by a collection of fiery stars which can not be individually seen by the unassisted human eye. Our 4.56 billion-year-old Sun is one of the billions of those bright stars doing their beautiful, happy dance in this wonderful World which is our birthplace.
Our Star is located in the far suburbs of our Milky Way, in one of its whirling spiraling arms. But, the star birth’s ancient history, which occurred deep within the heart of our Galaxy, has remained a mystery of many years. Astronomers at the Max Planck Institute-Gesellschaft in Germany published their results in December 2019 indicating that there were two strong bursts of development in the middle of our Milky Way that contributed to the formation of stars.
The latest findings suggest that star-birth occurred about eight billion years ago in the center of our galaxy. Yet the findings still indicate the second cycle of stellar formation happened around a billion years ago. Earlier, several observers had speculated that the stars inhabiting the comparatively small central disk of our Milky Way had been continually raised. This situation will stimulate new scientific research which will clarify the nature and properties of the bar-shaped structure inside the disk of our Galaxy.
According to the new observations, over 90 percent of the disk stars formed at least eight billion years ago during the first round of star-birth. However, the second cycle of stellar-birth, which was responsible for the creation of around 5 percent of the disk planets, happened even later — only around one billion years ago during a fairly brief period of time. There was a long period of celestial peace and calm between the two episodes of extreme planetary conception when barely any brilliant new baby stars were raised.
The stars observed in this study populate our Galaxy’s dense, disc-shaped region, called the nuclear disk. This disk encircles the innermost cluster of stars of the Milky Way and its central, resident black supermassive hole, dubbed Sagittarius A* (pronounced Sagittarius-a-star). The central black hole of our Galaxy is a relatively light-weight, at least as far as supermassive black holes go — and weighs in as much as millions of times solar-mass, as opposed to the billions of times solar-mass sported by many of its bizarre nature.
With their observations of two intense star-birth episodes, the astronomers suggested a revision of part of the mysterious ancient history of our Galaxy. Many astronomers have assumed over the past millions of years that the stars that populate the heart of our Milky Way have been born gradually. However, the new findings suggest a different timeline could exist. If so, a variety of other celestial events may have implications for this.
Also especially important is the current scenario because it sheds fresh light on Sagitarrius A* development. Gas floating into our Galaxy’s mysterious heart results in star-birth as well as an increase in the heavy mass of our resident supermassive black hole. This newly proposed revision of the star-formation history of our Milky Way suggests that Sagittarius A* probably achieved most of its present mass before eight billion years ago.
A Brief History Of Our Galaxy
Our starlit, barred-spiral Milky Way is just one of several billion other galaxies inhabiting the observable Universe. Before 1920, scientists believed our World was unique — and the entire Cosmos was.
Our Milky Way has an incredible distance varying from 150,000 to 200,000 light-years, and it is believed to be home to 100-200 billion stars — as well as over 100 billion planets. Our Solar System is situated at a radius of around 27,000 light-years from the Galactic Core, on the inner side of the Orion Chain, and is one of the spiral-shaped clusters of gas and dust that makes our Milky Way appear like a twirling giant starlit pin-wheel in the vastness of Spacetime. Within 10,000 light-years, the fiery, brilliant stars form a bulge and one or more bars which radiate from the bulge.
Brilliant stars and clouds of gas, located at wide distances from the heart of our Galaxy, all circle at about 220 km per second. This constant speed of rotation contradicts the laws of Keplerian dynamics and indicates that our telescopes are invisible to about 90 percent of the mass of our Galaxy — and that it does not emit or absorb electromagnetic radiation. This invisible, ghostly material has been called dark matter, and exotic non-atomic particles are thought to be composed of it. The mysterious dark matter plays the important role of the gravitational “glue” that holds galaxies together, and its existence explains why objects rotate all around the Galactic center at varying distances at a constant speed and thus defy Keplerian dynamics.
Our Milky Way as a whole climbs through Spacetime at a speed of about 600 kilometers per second as regards extragalactic reference frames. The most ancient stars inhabiting our Galaxy are almost as old as the Universe itself, which is 13.8 billion years old, and thus probably formed shortly after the cosmological dark ages following the Big Bang. Before the birth of the first generation of stars, the cosmological dark ages refer to a very antique era.
When we use the word “Milky Way” we just apply to the band of sparkling light that we see in our sky at night extending from horizon to horizon. The dark areas within this nebulous and gently luminous band, like the Great Rift and the Coalsack, are in fact regions where interstellar dust blocks the light emanating from distant stars. The portion of the night sky that is blocked by our Planet is considered the Field of Avoidance.
Our Milky Way has low surface brightness and can be significantly reduced in visibility due to background light flowing from light pollution or moonlight. Our Galaxy is hard to see from well-lit suburbs, but when seen from remote areas while the Earth’s Moon is below the horizon it shows up very well. Indeed, due to this background light, a third of the human population can not see the Milky Way from their homes.
Our Galaxy is the Local Group’s second-largest galaxy. The biggest is the significantly bigger galaxies with the ring, called Andromeda. Many small companion galaxies, such as the amorphous Large and Small Magellanic Clouds, also surround our Milky Way. Our Galaxy and its satellites as a member of the Local Group form part of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster.
Two Brilliant Blasts Of Baby Star-Birth
One billion years ago, the intense, but short-lived, episode of baby star birth is thought to be one of the most energetic events in the history of our Galaxy. In a period of only a few million years, hundreds of thousands of freshly created huge stars potentially erupted as supernovae.
Astronomers will continue to study an important feature of our Milky Way because of these new observations. Our Galaxy is a spiral that is barred. This means it sports an elongated region, calculated to be between 2,000 and 15,000 light-years in length, binding the inner ends of its two main spiral arms together. It is estimated that these galactic bar structures are quite efficient when funneling gas into the central region of a galaxy. This would bring about the birth of fiery new baby stars.
Astronomers are expected to come up with new theories to describe the silent billions of years in the nuclear Interstellar disk that were sterile from baby star formation. During those many peaceful years, gas was evidently not drenched in sufficient quantities into the Galactic center to form new stars. On December 16, 2019, Max Planck (MPIA) Press Release, Dr. Francisco Nogueras Lara, the lead author of the paper explaining this work, stated that “Either the Galactic Bar has come into existence only recently, or these bars are not as effective for funneling gas as is widely thought. In the latter case, some event — like a close encounter with a dwarf galaxy — must have triggered the gas flow toward the Galactic center about a billion years ago. “Dr. Lara was formerly at Astrofisica de Andalucia and is currently a post-doctoral researcher at MPIA.
This proposed reconstruction of the nuclear Galactic disk history is based upon certain known star formation properties. Stars can only “live” for a given span of time on the hydrogen-burning main sequence. For starters, our nearly 5 billion-year-old Sun has a 10 billion-year “life” cycle and is still in mid-life. A single star’s period of “existence” is dependent upon its mass and chemical composition.
Whenever a large number of stars are born at the same time — which is common in the Cosmos — astronomers can observe the ensemble, plot stellar brightness against the reddishness of color, and go on to determine how long ago the stellar siblings were born. One stellar-age indicator is called the red clump. The red clump stars have begun to fuse helium in their core — which means they have already fused their necessary hydrogen supply into helium. Astronomers can deduce the age of that group of stars by determining the average brightness of stars in that clump.
There is, indeed, a ‘pick’ Both those methods allow different stars to be observed by astronomers. Which poses quite a challenge for the central regions of our Galaxy. This is because the Galactic center is hidden behind enormous clouds of darkening dust when observed from Earth, thus requiring infrared observations in order to peer through these blanketing dust clouds.
Those studies are also bound to observe too many stars in the center of our Milky Way. The Galactic disk is very dense, packed in a cube with a side-length of one light-year, between a thousand and one hundred thousand stars. When astronomers observe very dense star fields of this type, the telescope image will overlap with those stellar disks. It is extremely difficult to separate such fields into single stars — but necessary if an observer wants to reconstruct the Galactic center’s formation history.
Taking all of these challenges into account, Dr. Rainer Schodel (Instituto de Astrofisica de Andalucia, PI of the Galactic Nucleus Survey), Dr. Nadine Neumayer of MPIA, and their colleagues began to plan how to deal with the problem. The astronomers knew they had to find the best instrument for this demanding mission. As Dr. Neumayer explained in the MPIA Press Release of December 16, 2019, “We wanted a near-infrared instrument with a wide field of view, capable of detecting the central area of the Milky Way that is in the Southern Sky.” The HAWK of the European Southern Observatory (ESO) proved to be an excellent resource for them to use for their survey. HAWK is a Very Large Telescope (VLT) Infrared Camera at the ESO Paranal Observatory in Chile.
In their study of the Galactic Nucleus, the astronomers studied the central area of our Milky Way using HAWK-1 in 16 hours. In doing so, they managed to collect more than three million stars with precise photometry. Using a special technique called holographic imaging, astronomers could distinguish between stars that were only 0.2 seconds apart from each other. With this high degree of precision, when viewed from a distance of more than 8 kilometers, it is possible to distinguish two separate pennies. In the resulting color-magnitude diagram a pair of distinctly noticeable red clumps enabled astronomers to reconstruct the creation background of the Galactic nuclear disk.
The astronomers are now researching the effect of dust (extinction and reddening) on their observations. Bringing the influence of dust into consideration will help us allow reconstructions of the past of the central regions of our Milky Way much more reliable in the future.