Carbon Worlds Are Dry As Diamonds!
One of the biggest questions in the study of alien worlds--exoplanets that circle stars beyond our own Solar System--is whether or not they are habitable.
Astronomers try to spot potentially life-friendly worlds by first searching for those that dwell within the habitable zone around their parent stars--that fortunate "Goldilocks" region that is not too hot, not too cold, but just right, for water to exist in its life-sustaining liquid state.
However, just because an alien world orbits within this "Goldilocks" region around its star, does not automatically indicate that it is inhabited.
In October 2013, astronomers studying carbon worlds dwelling in the remote families of distant stars, found that such exoplanets are probably dry as bone and are, therefore, not likely environments to host life as we know it--even if they dwell in the "Goldilocks" region around their parent-stars.
Scientists have been hunting for planets circling remote stars beyond our Sun for centuries, and their ultimate discovery almost a generation ago is clearly one of humanity's most noteworthy achievements.
Many times during the 20th century, exhilarated astronomers announced what they thought was the historic discovery of the very first exoplanet, only to unhappily look on as other astronomers failed to confirm their "discoveries".
However, in 1992, a radio astronomer finally succeeded in spotting the very first batch of exoplanets orbiting a very dense, relatively tiny stellar corpse, haunting our Milky Way Galaxy.
Dr.
Alexander Wolszczan of Pennsylvania State University made his historic announcement after carefully observing radio emissions emanating from a compact millisecond pulsar situated approximately 1,300 light-years from our Solar System.
One light-year is the distance light can travel in a vacuum in one year--5,880,000,000,000 miles! The pulsar, PSR B1257 + 12, is a dense, small inhabitant of the Virgo constellation.
A pulsar is a relatively tiny sphere, approximately 12 to 20 miles in diameter, which is the collapsed remnant of what was once a heavy star.
Pulsars can be composed of as much as one billion tons of star-stuff, that has been literally squashed down to the size of Phoenix, Arizona.
A pulsar is, in fact, a wildly spinning neutron star--the sad relic of a massive star that has perished in a fiery supernova explosion.
These weird and exotic objects sport a density that is approximately equal to 1,000,000 times that of water.
PSR B1257 + 12 was determined to be the parent of a family of several true "oddballs"--strange, rocky exoplanets, devoid of atmospheres, relentlessly blasted by a perpetual shower of deadly radiation spewing out from their parent-pulsar.
Planet-hunters were surprised to find worlds in orbit around a pulsar.
In fact, a pulsar was one of the last places they expected to find planets.
However, scientists soon learned to expect the unexpected in their search for remote alien worlds.
Among the more than 800 confirmed exoplanet discoveries--as of this writing--many turned out to be so bizarre that astronomers never dreamed that such strange worlds could really exist.
Even though the pulsar planets were the first batch of alien worlds to be discovered, planet-hunters still sought the Holy Grail of planets in orbit around a main-sequence (hydrogen-burning), normal star, like our own Sun.
Triumph finally came back in 1995, when two Swiss astronomers, Dr.
Michel Mayor and Dr.
Didier Queloz of the Geneva Observatory made their announcement of the first convincing evidence of an alien world in orbit around a Sun-like star.
However, even though this newly discovered world circled a normal star, it was another "oddball.
" This is because it was immense like our own Solar System's gas-giant Jupiter--the largest planet in our Solar System--but hugged its parent-star in a tight orbit that took it a tiny fraction of the distance between Mercury and our Sun.
The parent-star of this enormous planet is dubbed 51 Pegasi, and its roasting offspring was suitably dubbed 51 Pegasi b--or 51 Peg b, for short.
51 Peg b turned out to be the very first exoplanet to be detected belonging to a completely new, and unexpected class of planetary objects termed hot Jupiters.
Hot Jupiters are gas-giant planets circling fast and close around their parent-stars.
Since those very first discoveries, planet-hunters have spotted planetary systems similar to our own Solar System, as well as increasingly smaller and smaller alien worlds.
In fact, planet-hunters have now succeeded in spotting planets that are Earth-like in size.
With decreasing size, planet-hunters thought that they would discover increasingly Earth-like alien worlds.
However, small worlds proved that they could be just as bizarre as their larger counterparts.
Although carbon is the primary building block of life on Earth, it is relatively scarce in our Solar System.
Our Sun is a carbon-poor star.
As a result, our own planet is primarily composed of silicates.
Stars that are far more carbon-rich than our Sun can produce worlds that are literally loaded with carbon--and, perhaps, even sport layers of diamond! But such planets may lack oceans of life-sustaining liquid water, according to NASA-funded theoretical research released in October 2013.
Dry As Diamonds! "The building blocks that went into making our oceans are the icy asteroids and comets," noted Dr.
Torrence Johnson of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, on October 7, 2013 at a meeting of the American Astronomical Society's (AAS) Division of Planetary Sciences held in Denver, Colorado.
Dr.
Johnson is a team member of several planetary science missions, and has spent decades studying the objects of our own Solar System.
By modeling the ingredients of the rich stew that cooks up carbon-based planetary systems, Dr.
Johnson and his team determined that they are devoid of icy water reservoirs thought to supply planets, such as our own, with life-sustaining oceans of liquid water.
"If we keep track of these building blocks, we find that planets around carbon-rich stars come up dry," Dr.
Johnson added.
Dr.
Johnson and his colleagues suggest that the extra carbon that exists in developing planetary systems around distant stars would snare the oxygen, therefore preventing it from forming water.
"It is ironic that if carbon, the main element of life, becomes too abundant, it will steal away the oxygen that would have made water, the solvent essential to life as we know it," commented Dr.
Jonathan Lunine in an October 26, 2013 JPL Press Release.
Dr.
Lunine, of Cornell University in Ithaca, New York, is a collaborator on the research.
Even if an exoplanet is spotted in the habitable zone around its parent-star--where oceans of life-sustaining liquid water could theoretically exist--there still may not be enough water available to keep its surface sufficiently wet to support life.
Dr.
Johnson and his colleagues addressed this issue with planetary models that were based on measurements of our own Sun's carbon-to-oxygen ratio.
Our Star--like other stars--inherited its supply of elements both from the Big Bang and earlier generations of nuclear-fusing stars.
These atomic elements include hydrogen, helium, nitrogen, silicon, carbon, and oxygen.
"Our Universe has its own top 10 list of elements," Dr.
Johnson went on to comment, referring to the 10 most abundant atomic elements in the Cosmos.
The new planetary models were able to predict the amount of water--frozen up as ice--that existed in our ancient Solar System, billions of years ago.
The models were also able to determine how this primordial ice, at long last, made its way to Earth, to eventually become the life-sustaining oceans of our fortunate world.
Comets, as well as the parent bodies of asteroids, are believed to be the primary water-carriers in our early Solar System--although different planetary scientists debate their contributions.
Either way, the ancient water-bearing objects are thought to have started on their long journey very far beyond our Earth, past the boundary termed the snow line, before showering down upon our planet, depositing precious water deep in our primordial Earth and on its surface.
However, when the planetary scientists applied their models to carbon-rich stars, the water vanished.
"There's no snow beyond the snow line," Dr.
Johnson said at the October 2013 AAS meeting.
"All rocky planets aren't created equal.
So-called diamond planets the size of Earth, if they exist, will look totally alien to us: lifeless, ocean-less desert worlds," Dr.
Lunine commented in the October 26, 2013 JPL Press Release.
The results of the computer models supporting these conclusions were published in The Astrophysical Journal in 2012.
Astronomers try to spot potentially life-friendly worlds by first searching for those that dwell within the habitable zone around their parent stars--that fortunate "Goldilocks" region that is not too hot, not too cold, but just right, for water to exist in its life-sustaining liquid state.
However, just because an alien world orbits within this "Goldilocks" region around its star, does not automatically indicate that it is inhabited.
In October 2013, astronomers studying carbon worlds dwelling in the remote families of distant stars, found that such exoplanets are probably dry as bone and are, therefore, not likely environments to host life as we know it--even if they dwell in the "Goldilocks" region around their parent-stars.
Scientists have been hunting for planets circling remote stars beyond our Sun for centuries, and their ultimate discovery almost a generation ago is clearly one of humanity's most noteworthy achievements.
Many times during the 20th century, exhilarated astronomers announced what they thought was the historic discovery of the very first exoplanet, only to unhappily look on as other astronomers failed to confirm their "discoveries".
However, in 1992, a radio astronomer finally succeeded in spotting the very first batch of exoplanets orbiting a very dense, relatively tiny stellar corpse, haunting our Milky Way Galaxy.
Dr.
Alexander Wolszczan of Pennsylvania State University made his historic announcement after carefully observing radio emissions emanating from a compact millisecond pulsar situated approximately 1,300 light-years from our Solar System.
One light-year is the distance light can travel in a vacuum in one year--5,880,000,000,000 miles! The pulsar, PSR B1257 + 12, is a dense, small inhabitant of the Virgo constellation.
A pulsar is a relatively tiny sphere, approximately 12 to 20 miles in diameter, which is the collapsed remnant of what was once a heavy star.
Pulsars can be composed of as much as one billion tons of star-stuff, that has been literally squashed down to the size of Phoenix, Arizona.
A pulsar is, in fact, a wildly spinning neutron star--the sad relic of a massive star that has perished in a fiery supernova explosion.
These weird and exotic objects sport a density that is approximately equal to 1,000,000 times that of water.
PSR B1257 + 12 was determined to be the parent of a family of several true "oddballs"--strange, rocky exoplanets, devoid of atmospheres, relentlessly blasted by a perpetual shower of deadly radiation spewing out from their parent-pulsar.
Planet-hunters were surprised to find worlds in orbit around a pulsar.
In fact, a pulsar was one of the last places they expected to find planets.
However, scientists soon learned to expect the unexpected in their search for remote alien worlds.
Among the more than 800 confirmed exoplanet discoveries--as of this writing--many turned out to be so bizarre that astronomers never dreamed that such strange worlds could really exist.
Even though the pulsar planets were the first batch of alien worlds to be discovered, planet-hunters still sought the Holy Grail of planets in orbit around a main-sequence (hydrogen-burning), normal star, like our own Sun.
Triumph finally came back in 1995, when two Swiss astronomers, Dr.
Michel Mayor and Dr.
Didier Queloz of the Geneva Observatory made their announcement of the first convincing evidence of an alien world in orbit around a Sun-like star.
However, even though this newly discovered world circled a normal star, it was another "oddball.
" This is because it was immense like our own Solar System's gas-giant Jupiter--the largest planet in our Solar System--but hugged its parent-star in a tight orbit that took it a tiny fraction of the distance between Mercury and our Sun.
The parent-star of this enormous planet is dubbed 51 Pegasi, and its roasting offspring was suitably dubbed 51 Pegasi b--or 51 Peg b, for short.
51 Peg b turned out to be the very first exoplanet to be detected belonging to a completely new, and unexpected class of planetary objects termed hot Jupiters.
Hot Jupiters are gas-giant planets circling fast and close around their parent-stars.
Since those very first discoveries, planet-hunters have spotted planetary systems similar to our own Solar System, as well as increasingly smaller and smaller alien worlds.
In fact, planet-hunters have now succeeded in spotting planets that are Earth-like in size.
With decreasing size, planet-hunters thought that they would discover increasingly Earth-like alien worlds.
However, small worlds proved that they could be just as bizarre as their larger counterparts.
Although carbon is the primary building block of life on Earth, it is relatively scarce in our Solar System.
Our Sun is a carbon-poor star.
As a result, our own planet is primarily composed of silicates.
Stars that are far more carbon-rich than our Sun can produce worlds that are literally loaded with carbon--and, perhaps, even sport layers of diamond! But such planets may lack oceans of life-sustaining liquid water, according to NASA-funded theoretical research released in October 2013.
Dry As Diamonds! "The building blocks that went into making our oceans are the icy asteroids and comets," noted Dr.
Torrence Johnson of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, on October 7, 2013 at a meeting of the American Astronomical Society's (AAS) Division of Planetary Sciences held in Denver, Colorado.
Dr.
Johnson is a team member of several planetary science missions, and has spent decades studying the objects of our own Solar System.
By modeling the ingredients of the rich stew that cooks up carbon-based planetary systems, Dr.
Johnson and his team determined that they are devoid of icy water reservoirs thought to supply planets, such as our own, with life-sustaining oceans of liquid water.
"If we keep track of these building blocks, we find that planets around carbon-rich stars come up dry," Dr.
Johnson added.
Dr.
Johnson and his colleagues suggest that the extra carbon that exists in developing planetary systems around distant stars would snare the oxygen, therefore preventing it from forming water.
"It is ironic that if carbon, the main element of life, becomes too abundant, it will steal away the oxygen that would have made water, the solvent essential to life as we know it," commented Dr.
Jonathan Lunine in an October 26, 2013 JPL Press Release.
Dr.
Lunine, of Cornell University in Ithaca, New York, is a collaborator on the research.
Even if an exoplanet is spotted in the habitable zone around its parent-star--where oceans of life-sustaining liquid water could theoretically exist--there still may not be enough water available to keep its surface sufficiently wet to support life.
Dr.
Johnson and his colleagues addressed this issue with planetary models that were based on measurements of our own Sun's carbon-to-oxygen ratio.
Our Star--like other stars--inherited its supply of elements both from the Big Bang and earlier generations of nuclear-fusing stars.
These atomic elements include hydrogen, helium, nitrogen, silicon, carbon, and oxygen.
"Our Universe has its own top 10 list of elements," Dr.
Johnson went on to comment, referring to the 10 most abundant atomic elements in the Cosmos.
The new planetary models were able to predict the amount of water--frozen up as ice--that existed in our ancient Solar System, billions of years ago.
The models were also able to determine how this primordial ice, at long last, made its way to Earth, to eventually become the life-sustaining oceans of our fortunate world.
Comets, as well as the parent bodies of asteroids, are believed to be the primary water-carriers in our early Solar System--although different planetary scientists debate their contributions.
Either way, the ancient water-bearing objects are thought to have started on their long journey very far beyond our Earth, past the boundary termed the snow line, before showering down upon our planet, depositing precious water deep in our primordial Earth and on its surface.
However, when the planetary scientists applied their models to carbon-rich stars, the water vanished.
"There's no snow beyond the snow line," Dr.
Johnson said at the October 2013 AAS meeting.
"All rocky planets aren't created equal.
So-called diamond planets the size of Earth, if they exist, will look totally alien to us: lifeless, ocean-less desert worlds," Dr.
Lunine commented in the October 26, 2013 JPL Press Release.
The results of the computer models supporting these conclusions were published in The Astrophysical Journal in 2012.
