12192"Rogue Planets May Help Seed Microbial Life in the Universe"
- Oct 10, 2013Interesting post from the Daily GalaxyChris
Sent: 10/10/2013 6:08:47 P.M. Eastern Daylight Time
Subj: The Daily Galaxy: News from Planet Earth & Beyond
Posted: 10 Oct 2013 07:40 AM PDT
There may be 100,000 times more wandering “nomad planets” in the Milky Way than stars, and some may carry bacterial life, according to a new study by researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). A nomadic object may be an icy body akin to an object found in the outer solar system, a more rocky material akin to asteroid, or even a gas giant similar in composition to the most massive solar system planets and exoplanets. If observations confirm the estimate, this new class of celestial objects will affect current theories of planet formation and could change our understanding of the origin and abundance of life."If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist," said Louis Strigari, leader of the team that reported the result in a paper submitted to the Monthly Notices of the Royal Astronomical Society. Although nomad planets don't bask in the warmth of a star, they may generate heat through internal radioactive decay and tectonic activity.
Searches over the past two decades have identified more than 500 planets outside our solar system, almost all of which orbit stars. Last year, researchers detected about a dozen nomad planets, using a technique called gravitational microlensing, which looks for stars whose light is momentarily refocused by the gravity of passing planets.
The research produced evidence that roughly two nomads exist for every typical, so-called main-sequence star in our galaxy. The new study estimates that nomads may be up to 50,000 times more common than that.To arrive at what Strigari himself called "an astronomical number," the KIPAC team took into account the known gravitational pull of the Milky Way galaxy, the amount of matter available to make such objects and how that matter might divide itself up into objects ranging from the size of Pluto to larger than Jupiter.
Not an easy task, considering no one is quite sure how these bodies form. According to Strigari, some were probably ejected from solar systems, but research indicates that not all of them could have formed in that fashion.
"To paraphrase Dorothy from The Wizard of Oz, if correct, this extrapolation implies that we are not in Kansas anymore, and in fact we never were in Kansas," said Alan Boss of the Carnegie Institution for Science, author of The Crowded Universe: The Search for Living Planets, who was not involved in the research. "The universe is riddled with unseen planetary-mass objects that we are just now able to detect."
A good count, especially of the smaller objects, will have to wait for the next generation of big survey telescopes, especially the space-based Wide-Field Infrared Survey Telescope and the ground-based Large Synoptic Survey Telescope, both set to begin operation in the early 2020s.A confirmation of the estimate could lend credence to another possibility mentioned in the paper – that as nomad planets roam their starry pastures, collisions could scatter their microbial flocks to seed life elsewhere.
"Few areas of science have excited as much popular and professional interest in recent times as the prevalence of life in the universe," said co-author and KIPAC Director Roger Blandford. "What is wonderful is that we can now start to address this question quantitatively by seeking more of these erstwhile planets and asteroids wandering through interstellar space, and then speculate about hitchhiking bugs."
If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” said Louis Strigari, leader of the team that reported the result in a paper submitted to theMonthly Notices of the Royal Astronomical Society.
In 2010, researchers detected about a dozen nomad planets, using a technique called gravitational microlensing. A confirmation of the estimate could lend credence to another possibility mentioned in the paper — that as nomad planets roam their starry pastures, collisions could scatter their microbial flocks to seed life elsewhere.
The image above is an artistic rendition of a nomad object wandering the interstellar medium (intentionally blurry to represent uncertainty about whether it has an atmosphere).
The Daily Galaxy via Stanford University
Image credit: . Greg Stewart/SLAC National Accelerator Laboratory
Posted: 10 Oct 2013 07:30 AM PDT
An international team of astronomers has discovered an exotic young planet that is not orbiting a star. This free-floating planet, dubbed PSO J318.5-22, is just 80 light-years away from Earth and has a mass only six times that of Jupiter. The planet formed a mere 12 million years ago—a newborn in planet lifetimes. The orphan planet was discovered during a search for the failed stars known as brown dwarfs. The planet is extremely cold and faint, about 100 billion times fainter in optical light than the planet Venus. Most of its energy is emitted at infrared wavelengths.It was identified from its faint and unique heat signature by the Pan-STARRS 1 (PS1) wide-field survey telescope on Haleakala, Maui. Follow-up observations using other telescopes in Hawaii show that it has properties similar to those of gas-giant planets found orbiting around young stars. And yet PSO J318.5-22 is all by itself, without a host star.
"We have never before seen an object free-floating in space that that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting out there all alone,” explained team leader Dr. Michael Liu of the Institute for Astronomy at the University of Hawaii at Manoa. “I had often wondered if such solitary objects exist, and now we know they do.”
During the past decade, extrasolar planets have been discovered at an incredible pace, with about a thousand found by indirect methods such as wobbling or dimming of their host stars induced by the planet. However, only a handful of planets have been directly imaged, all of which are around young stars (less than 200 million years old). PSO J318.5-22 is one of the lowest-mass free-floating objects known, perhaps the very lowest. But its most unique aspect is its similar mass, color, and energy output to directly imaged planets.
“Planets found by direct imaging are incredibly hard to study, since they are right next to their much brighter host stars. PSO J318.5-22 is not orbiting a star so it will be much easier for us to study. It is going to provide a wonderful view into the inner workings of gas-giant planets like Jupiter shortly after their birth,” said Dr. Niall Deacon of the Max Planck Institute for Astronomy in Germany and a co-author of the study.
Due to their relatively cool temperatures, brown dwarfs are very faint and have very red colors. To circumvent these difficulties, Liu and his colleagues have been mining the data from the PS1 telescope. PS1 is scanning the sky every night with a camera sensitive enough to detect the faint heat signatures of brown dwarfs. PSO J318.5-22 stood out as an oddball, redder than even the reddest known brown dwarfs.
Multicolor image from the Pan-STARRS1 telescope of the free-floating planet PSO J318.5-22, in the constellation of Capricornus. The image is 125 arcseconds on a side. Credit: N. Metcalfe & Pan-STARRS 1 Science Consortium.
“We often describe looking for rare celestial objects as akin to searching for a needle in a haystack. So we decided to search the biggest haystack that exists in astronomy, the dataset from PS1,” said Dr. Eugene Magnier of the Institute for Astronomy at the University of Hawaii at Manoa and a co-author of the study. Dr. Magnier leads the data processing team for PS1, which produces the equivalent of 60,000 iPhone photos every night. The total dataset to date is about 4,000 Terabytes, bigger than the sum of the digital version of all the movies ever made, all books ever published, and all the music albums ever released.
The team followed up the PS1 discovery with multiple telescopes on the summit of Mauna Kea on the island of Hawaii. Infrared spectra taken with the NASA Infrared Telescope Facility and the Gemini North Telescope showed that PSO J318.5-22 was not a brown dwarf, based on signatures in its infrared light that are best explained by it being young and low-mass.
The team concluded that PSO J318.5-22 belongs to a collection of young stars called the Beta Pictoris moving group that formed about 12 million years ago. In fact, the eponymous star of the group, Beta Pictoris, has a young gas-giant planet in orbit around it. PSO J318.5-22 is even lower in mass than the Beta Pictoris planet and probably formed in a different fashion.
A recent study, "Nomads of the Galaxy," proposed an upper limit to the number of nomad planets that might exist in the galaxy: 100,000 for every star. And because the Milky Way is estimated to have 200 to 400 billion stars, that could put the number of nomad planets in the quadrillions.
If this proposal is correct, it could be that nomad planets play a dynamic role in the universe. In particular, if life can exist without the warmth of a nearby sun, it raises the possibility that, along with sustaining life, nomad planets could be transporting it as well. While just an idea, it's one that becomes more intriguing when considering not only the number of nomad planets, but the behavior of galaxies.
"In the 20th century, many eminent scientists have entertained the speculation that life propagated either in a directed, random or malicious way throughout the galaxy," said Roger D. Blandford, A co-author of the recent study and director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and the SLAC National Accelerator Laboratory.
"One thing that I think modern astronomy might add to that is clear evidence that many galaxies collide and spray material out into intergalactic space. So life can propagate between galaxies too, in principle."
I'm really curious about the exchange of planets between solar systems," said Louis E. Strigari, lead author of the study and research associate at KIPAC and the SLAC, " How often does it happen, and how far can a nomad planet travel? How many trips around our galaxy does it make? I think these are brand new, basic questions. And I think that's an exciting place to be."
"If you imagine the Earth as it is today becoming a nomad planet... life on Earth is not going to cease," said Dimitar D. Sasselov, Professor of Astronomy at Harvard University and the Harvard-Smithsonian Center for Astrophysics, and the Director of the Harvard Origins of Life Initiative. "That we know. It's not even speculation at this point. ...[Scientists] already have identified a large number of microbes and even two types of nematodes that survive entirely on the heat that comes from inside the Earth."
The image at the top of the page is an artistic rendition of a nomad object wandering the interstellar medium. The object is intentionally blurry to represent uncertainty about whether or not it has an atmosphere. A nomadic object may be an icy body akin to an object found in the outer Solar System, a more rocky material akin to asteroid, or even a gas giant similar in composition to the most massive Solar System planets and exoplanets.
The discovery paper of PSO J318.5-22 is being published by Astrophysical Journal Letters and is available at http://arxiv.org/abs/1310.0457. The other key authors of the paper are Katelyn Allers (Bucknell University), Trent Dupuy (Harvard-Smithsonian Center for Astrophysics), and Michael Kotson and Kimberly Aller (University of Hawaii at Manoa).
Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Mauna Kea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii.
The Daily Galaxy via Institute for Astronomy, Monthly Notices of the Royal Astronomical Society and The Kavli Foundation.
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