Pluto may have 10 more undiscovered moons

pluto

Pluto’s orbit may host a formation of 10 or more tiny undiscovered moons, which would each measure just 1 to 3 kilometres across, astronomers say.

This preliminary finding could make life even more difficult for the team planning NASA’s New Horizons mission, which is slated to take the first-ever up-close look at the Pluto system in July 2015.

After Pluto’s fifth known moon, a small satellite known as P5, was discovered last year, officials said they may need to redraw the spacecraft’s path to avoid such obstacles.

In the new study, astronomers led by Scott Kenyon of the Harvard-Smithsonian Center for Astrophysics used computer simulations that treat smaller particles statistically.

Once objects get above a certain size, roughly 1 km across, then the programme renders them individually – and this is when the satellites pop up.

It’s hard to say how many there are, the researchers said, as it’s difficult to simulate collisions among these tiny satellites. There could be anywhere from one to more than 10 objects lurking beyond Hydra’s orbit.

While the team can simulate these satellites, they said it’s unlikely they could be spotted, if they exist, from Earth.

The brightness of the potential objects dance with the edge of the Hubble Space Telescope’s capabilities, Kenyon said, and they are likely beyond the reach of even the most sensitive ground-based telescopes, such as the Keck Observatory in Hawaii.

New Horizons might be able to spot smaller satellites before it gets there, but Kenyon said he wasn’t sure when the objects would appear big enough for the spacecraft to detect.

The satellites would be “easily visible” during the spacecraft’s closest approach to Pluto in 2015, researchers said.

The study was submitted for publication in The Astronomical Journal.

http://www.phenomenica.com/2013/03/pluto-may-have-10-more-undiscovered-moons.html

Closest Single Star Like Our Sun May Have Habitable Planet

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An international team of astronomers led by the University of Hertfordshire has discovered that Tau Ceti, one of the closest and most Sun-like stars, may host five planets — with one in the star’s habitable zone.

At a distance of twelve light years and visible with the naked eye in the evening sky, Tau Ceti is the closest single star that has the same spectral classification as our Sun. Its five planets are estimated to have masses between two and six times the mass of Earth — making it the lowest-mass planetary system yet detected. One of the planets lies in the habitable zone of the star and has a mass around five times that of Earth, making it the smallest planet found to be orbiting in the habitable zone of any Sun-like star.

The international team of astronomers, from the UK, Chile, the USA, and Australia, combined more than six-thousand observations from three different instruments and intensively modelled the data. Using new techniques, the team has found a method to detect signals half the size previously thought possible. This greatly improves the sensitivity of searches for small planets and suggests that Tau Ceti is not a lone star but has a planetary system.

Mikko Tuomi, from the University of Hertfordshire and the first author of the paper, said: “We pioneered new data modelling techniques by adding artificial signals to the data and testing our recovery of the signals with a variety of different approaches. This significantly improved our noise modelling techniques and increased our ability to find low mass planets.”

“We chose Tau Ceti for this noise modelling study because we had thought it contained no signals. And as it is so bright and similar to our Sun it is an ideal benchmark system to test out our methods for the detection of small planets,” commented Hugh Jones from the University of Hertfordshire.

James Jenkins, Universidad de Chile and Visiting Fellow at the University of Hertfordshire, explained: “Tau Ceti is one of our nearest cosmic neighbours and so bright that we may be able to study the atmospheres of these planets in the not too distant future. Planetary systems found around nearby stars close to our Sun indicate that these systems are common in our Milky Way galaxy.”

Over 800 planets have been discovered orbiting other worlds, but planets in orbit around the nearest Sun-like stars are particularly valuable. Steve Vogt from University of California Santa Cruz said: “This discovery is in keeping with our emerging view that virtually every star has planets, and that the galaxy must have many such potentially habitable Earth-sized planets. They are everywhere, even right next door! We are now beginning to understand that Nature seems to overwhelmingly prefer systems that have a multiple planets with orbits of less than one hundred days. This is quite unlike our own solar system where there is nothing with an orbit inside that of Mercury. So our solar system is, in some sense, a bit of a freak and not the most typical kind of system that Nature cooks up.”

“As we stare the night sky, it is worth contemplating that there may well be more planets out there than there are stars … some fraction of which may well be habitable,” remarked Chris Tinney from the University of New South Wales.

Journal Reference:

1.M. Tuomi, H. R. A. Jones, J. S. Jenkins, C. G. Tinney, R. P. Butler, S. S. Vogt, J. R. Barnes, R. A. Wittenmyer, S. O’Toole, J. Horner, J. Bailey, B. D. Carter, D. J. Wright, G. S. Salter, D. Pinfield. Signals embedded in the radial velocity noise. Periodic variations in the tau Ceti velocities. Astronomy & Astrophysics, 2012; DOI: 10.1051/0004-6361/201220509

http://www.sciencedaily.com/releases/2012/12/121219084102.htm

Orphan alien planet without a parent star discovered nearby

Astronomers have discovered a potential “rogue” alien planet wandering alone just 100 light-years from Earth, suggesting that such starless worlds may be extremely common across the galaxy.

The free-floating object, called CFBDSIR2149, is likely a gas giant planet four to seven times more massive than Jupiter, scientists say in a new study unveiled today (Nov. 14). The planet cruises unbound through space relatively close to Earth (in astronomical terms; the Milky Way galaxy is 100,000 light-years wide), perhaps after being booted from its own solar system.

“If this little object is a planet that has been ejected from its native system, it conjures up the striking image of orphaned worlds, drifting in the emptiness of space,” study leader Philippe Delorme, of the Institute of Planetology and Astrophysics of Grenoble in France, said in a statement.

Delorme and his team detected CFBDSIR2149’s infrared signature using the Canada-France-Hawaii Telescope, then examined the body’s properties with the European Southern Observatory’s Very Large Telescope in Chile. [Video: Rogue Planet Has No Parent Star]

The newfound object appears to be among a stream of young stars called the AB Doradus moving group, the closest such stream to our own solar system.

Scientists think the AB Doradus stars all formed together between 50 million and 120 million years ago. If CFBDSIR2149 is indeed associated with the group — and researchers cite a nearly 90 percent probability — then the object is similarly young.

And if the discovery team is right about CFBDSIR2149’s age, the body is likely a planet, with an average temperature of 806 degrees Fahrenheit (430 degrees Celsius), researchers said.

There’s still a slight chance that CFBDSIR2149 is a brown dwarf — a strange object that’s larger than a planet but too small to trigger the internal nuclear fusion reactions required to become a full-fledged star. Additional observations should help decide the matter.

“We need new observations to confirm that this object belongs to the AB Doradus moving group,” Delorme told SPACE.com via email. “With a good distance measurement and a more accurate proper motion, we will be able to increase (or decrease) the probability that it is indeed a planet.”

The new study was published today in the journal Astronomy & Astrophysics.

The discovery of a starless alien planet would not be shocking, at least not anymore. In the last year or so, astronomers have spotted a number of such orphan worlds — so many, in fact, that some scientists think parentless planets are the rule rather than the exception.

One 2011 study, for example, estimated that rogue worlds outnumber “normal” planets with obvious host stars by at least 50 percent throughout the Milky Way. If that’s the case, the galaxy that includes Earth probably also hosts billions of orphan planets.

And gas giants may be in the minority among these solitary wanderers, researchers say.

“We now know that such massive planets are rare and that Neptunes or Earth-mass planets are much more common,” Delorme said. “We also know that massive objects are more difficult to eject [from solar systems] than light ones. If you follow the rationale, you deduce that ejected exo-Neptunes and ejected exo-Earths should be much more common than objects like CFBDSIR2149.”

It’s exciting to have a starless planet so close to Earth, researchers say. Future telescopes should be able to learn a great deal about CFBDSIR2149, since they won’t have to contend with the overwhelming glare of a nearby host star.

“This object is a really easy-to-study prototype of the ‘normal’ giant planets we hope to discover and study with the upcoming generation of direct-imaging instruments,” Delorme said. “It will help to improve our forecast of these objects’ luminosity and hence help us discover them ―and, once discovered, it will help us understand the physics of their atmospheres.”

http://www.livescience.com/24772-rogue-alien-planet-discovery.html