Out home galaxy, the Milky Way, is not static, is not dying. It is a “living and breathing” entity, gobbling up nearby stars, galaxies and inter-stellar material for dinner and burping gases into interstellar space. New stars are still being formed as new and previously ejected material enters the Milky Way.
New Stellar Streams confirm 'Melting Pot' history of our Galaxy
A report published at www.noao.edu/… states — “Much like the waves of migration that brought diverse groups of people to the United States, our own Galaxy is thought to have been enriched by stars from other galaxies in discrete migration events. When a small neighboring galaxy ventures close to the Milky Way, the gravitational pull of the Milky Way draws out tendrils of stars from the neighboring galaxy, which trail behind it in a stream.”
It is a polite way of saying that the Milky Way is slurping up stars from neighboring galaxies.
Earlier this week, scientists on the Dark Energy Survey (DES) announced the public release of their first three years of data. This first major release of data from the Survey includes information on about 400 million astronomical objects, including distant galaxies billions of light-years away as well as stars in our own galaxy. news.fnal.gov/...
Eleven new stellar streams were discovered in this new data; these streams contain stars and material being drawn out from nearby dwarf galaxies. These streams provide new evidence for this picture of the Milky Way growing in size by munching at small galaxies.
The Dark Energy Camera (DECam), the primary observation tool of the Dark Energy Survey, is one of the most powerful digital imaging devices in existence. It was built and tested at UChicago-affiliated Fermilab, and is mounted on the National Science Foundation’s 4-meter Blanco telescope in Chile. It uses an array of 62 2048×4096 pixel ultra-sensitive CCDs totaling 520 megapixels, with a 2.2 degree diameter field of view. Each DECam image is a gigabyte in size. The ~400 images generated every night are processed on large computing clusters at NCSA and at Fermilab. arxiv.org/...
The Naming of the Streams
For a few lucky groups in Chile and Australia, this discovery meant an extraordinary opportunity: getting to name an object in space. www.symmetrymagazine.org/…
Previously discovered stellar streams were often named after constellations in the sky near their location, which soon became unwieldy. They decided to use a different tack this time and use names of terrestrial origin.
One set of the newly discovered stellar streams, located in the sky near the Indus constellation, were named after Indian rivers - Indus, Jhelum, Chenab and Ravi.
In Chile, DES worked with students in the nearby town of Vicuña to select words from the native Quechua and Aymara cultures that were related to water, such as the Aymara name Aliqa Una, meaning Quiet Water, and two Quechua names, Palca, meaning Crossing Rivers, and Willka Yaku, or Sacred Water. Two Spanish names for local rivers near Vicuña - Elqui and Turbio, rounded out the set.
In Australia, names of Aboriginal origin were presented to a group of about 100 adults at the Sydney Royal Botanic Gardens and 40 preschoolers; the winning names were Wambelong, meaning Crazy Water in the Gamilaraay language, and Turranburra, the Dharug name for the Lane Cove River.
Swarm of Hydrogen Clouds flying away from the Center of our Galaxy
While our galaxy is digesting its smaller neighbors, a team of astronomers has discovered more than 100 energetic hydrogen clouds racing away from the center of the Milky Way into intergalactic space.
The heart of our galaxy harbors a massive black hole, Sagittarius A*, containing the mass of about 4 million Suns; in this region, new stars are born, old stars explode and black holes eject jet-streams. These energetic processes have generated a powerful cosmic “wind” that has blown two enormous “Fermi” bubbles above and below the disk of the Milky Way, filled with gas at tens-of-millions of degrees.
The clouds, observed using National Science Foundation’s Green Bank Telescope (GBT), at higher resolution than ever before, seem to have widely varying velocities. According to the research team, that includes Jay Lockman, Naomi McClure-Griffiths and and Enrico DiTeodoro, the most likely explanation is that they’re traveling within a cone of material that is expanding upward and away from the galactic center, so material at the front edge of the cone is coming toward us and the back part is moving away. greenbankobservatory.org/…
The exact sources of these cosmic burps is still unknown but the processes that create them have been known for a while; detection of these faint sparse clouds has been difficult until now.
The 100m diameter Green Bank Telescope, used in this study and located in Green Bank, West Virginia, is the world’s largest fully steerable radio telescope. The distinction of the largest (non-steerable) radio telescope belongs to the newly built 500m Chinese FAST telescope.
Fermi bubbles are gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center and may be the remnant of a past eruption from the black hole Sgr A* at the center of our galaxy. Sgr A* is currently relatively quiet. www.nasa.gov/…
Here is video from 2010 on Fermi bubbles -
Swarm of Gas Clouds flying into our Galaxy
In addition to these two forms of ingestions and ejections, previous research has shown that massive interstellar clouds of gas (aka high-velocity clouds HVCs) are hurtling towards the Milky Way, feeding our hungry galaxy and causing new star formation. Some of these clouds are part of previously ejected material that are gravitating back into the Milky Way.
Research reported in Aug 2011, shows that without the replenishment from recycled gas and infalling extragalactic material, stars would have stopped forming in the Milky Way a long time ago. arxiv.org/...
The Smith Cloud is an example of a giant (sulfurous) cloud that was ejected from the Milky Way, but it boomeranged and now is headed back towards us at nearly 1.1 million km per hour. The cloud is expected to plow into the Milky Way’s disk in about 30 million years. Astronomers believe it will ignite a spectacular burst of star formation, perhaps providing enough gas to make 2 million suns. Astronomers, using the Hubble Space Telescope, found that the Smith Cloud is as rich in sulfur as the Milky Way’s outer disk, implying that the cloud originated from the Milky Way. www.nasa.gov/…
The Milky Way
The Milky Way, our home galaxy, has a diameter between 100,000 and 180,000 light-years. It is estimated to contain 100–400 billion stars. There are probably at least 100 billion planets in the Milky Way.
The observable universe is estimated to contain 2 trillion galaxies. www.nasa.gov/...
The animation below depicts the collision between our Milky Way galaxy and the nearby Andromeda galaxy. Hubble observations indicate that the two galaxies, pulled together by their mutual gravity, will crash together in about 4 billion years and merge over the next few billion years to form a single galaxy. The galaxy product of the collision has been nicknamed Milkomeda or Milkdromeda.
Scientists predict a 12% chance that the Solar System will be ejected from the new galaxy. Scientists say that such an event would have no adverse effect on the system and the chances of any sort of disturbance to the Sun or planets themselves may be remote. That’s comforting.
However, our Sun itself is going to expand and get much brighter in the next few billion years. Within a billion years, its luminosity will rise enough to evaporate oceans and end life on Earth. In 5 billion years, the Sun will turn into a red giant and will grow so large that it will engulf Mercury, Venus, and probably Earth. Earth will become uninhabitable long before the galactic collision. So, we better “evolve" and find ourselves a new home before these cosmic events occur ;)
Black Holes
So what is a black hole, one of which resides at the center of our galaxy and plays an important role in some of these stories? There is strong evidence that a supermassive back hole resides at the center of every galaxy. It is estimated that there are millions of black holes in each galaxy outside its center. The documentary “Black Hole Apocalypse” that premiered on PBS on Jan 10 does a commendable job of explaining these enigmatic celestial objects. For additional info, please take a look at these earlier diaries —
Epilogue
How excited are you about discovering and understanding the mysteries of the Universe? How about the children in your extended family? Are they inspired to learn about science and work towards careers in physics and astronomy?