. .

Planets in the habitable zone around most stars, calculate researchers
by Staff Writers
Copenhagen, Denmark (SPX) Mar 22, 2015
 The illustration shows the habitable zone for different types of stars. The distance to the habitable zone is dependent on how big and bright the star is. The green area is the habitable zone, where liquid water can exist on a planet's surface. The red area is too hot for liquid water on the planetary surface and the blue area is too cold for liquid water on the planetary surface. Image courtesy NASA, Kepler. For a larger version of this image please go here.

Astronomers have discovered thousands of exoplanets in our galaxy, the Milky Way, using the Kepler satellite and many of them have multiple planets orbiting the host star. By analysing these planetary systems, researchers from the Australian National University and the Niels Bohr Institute in Copenhagen have calculated the probability for the number of stars in the Milky Way that might have planets in the habitable zone.

The calculations show that billions of the stars in the Milky Way will have one to three planets in the habitable zone, where there is the potential for liquid water and where life could exist. The results are published in the scientific journal, Monthly Notices of the Royal Astronomical Society.

Using NASA's Kepler satellite, astronomers have found about 1,000 planets around stars in the Milky Way and they have also found about 3,000 other potential planets. Many of the stars have planetary systems with 2-6 planets, but the stars could very well have more planets than those observable with the Kepler satellite, which is best suited for finding large planets that orbit relatively close to their stars.

Planets that orbit close to their stars would be too scorching hot to have life, so to find out if such planetary systems might also have planets in the habitable zone with the potential for liquid water and life, a group of researchers from the Australian National University and the Niels Bohr Institute at the University of Copenhagen made calculations based on a new version of a 250-year-old method called the Titius-Bode law.

Calculating planetary positions
The Titius-Bode law was formulated around 1770 and correctly calculated the position of Uranus before it was even discovered. The law states that there is a certain ratio between the orbital periods of planets in a solar system. So the ratio between the orbital period of the first and second planet is the same as the ratio between the second and the third planet and so on.

Therefore, if you knew how long it takes for some of the planets to orbit around the Sun/star, you can calculate how long it takes for the other planets to orbit and can thus calculate their position in the planetary system. You can also calculate if a planet is 'missing' in the sequence.

"We decided to use this method to calculate the potential planetary positions in 151 planetary systems, where the Kepler satellite had found between 3 and 6 planets. In 124 of the planetary systems, the Titius-Bode law fit with the position of the planets.

Using T-B's law we tried to predict where there could be more planets further out in the planetary systems. But we only made calculations for planets where there is a good chance that you can see them with the Kepler satellite," explains Steffen Kjaer Jacobsen, PhD student in the research group Astrophysics and Planetary Science at the Niels Bohr Institute at the University of Copenhagen.

In 27 of the 151 planetary systems, the planets that had been observed did not fit the T-B law at first glance. They then tried to place planets into the 'pattern' for where planets should be located. Then they added the planets that seemed to be missing between the already known planets and also added one extra planet in the system beyond the outermost known planet. In this way, they predicted a total of 228 planets in the 151 planetary systems.

"We then made a priority list with 77 planets in 40 planetary systems to focus on because they have a high probability of making a transit, so you can see them with Kepler. We have encouraged other researchers to look for these. If they are found, it is an indication that the theory stands up," explains Steffen Kjaer Jacobsen.

Planets in the habitable zone
Planets that orbit very close around a star are too scorching hot to have liquid water and life and planets that are far from the star would be too deep-frozen, but the intermediate habitable zone, where there is the potential for liquid water and life, is not a fixed distance. The habitable zone for a planetary system will be different from star to star, depending on how big and bright the star is.

The researchers evaluated the number of planets in the habitable zone based on the extra planets that were added to the 151 planetary systems according to the Titius-Bode law. The result was 1-3 planets in the habitable zone for each planetary system.

Out of the 151 planetary systems, they now made an additional check on 31 planetary systems where they had already found planets in the habitable zone or where only a single extra planet was needed to meet the requirements.

"In these 31 planetary systems that were close to the habitable zone, our calculations showed that there was an average of two planets in the habitable zone. According to the statistics and the indications we have, a good share of the planets in the habitable zone will be solid planets where there might be liquid water and where life could exist," explains Steffen Kjaer Jacobsen.

If you then take the calculations further out into space, it would mean that just in our galaxy, the Milky Way, there could be billions of stars with planets in the habitable zone, where there could be liquid water and where life could exist.

He explains that what they now want to do is encourage other researchers to look at the Kepler data again for the 40 planetary systems that they have predicted should be well placed to be observed with the Kepler satellite.

Understanding Titius-Bode's law
The Titius-Bode law is a loose rule for planetary orbital periods and their distance from the Sun. The law was proposed in 1766 by J.D. Titius and was described mathematically by J.E. Bode in 1772.

The law shows a relationship between the distance of the planets from the Sun based on a simple series of numbers: 0, 3, 6, 12, 24, 48, 96, 192, 384. Apart from the first two, the numbers are simply a doubling of the previous number. Then you add 4 to each number and divide it by 10 = 0,4 / 0,7 / 1,0 / 1,6 / 2,8 / 5,2 / 10,0 / 19,6 / 38,8. This gives a planetary system with stable orbits.

 Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution. SpaceDaily Contributor \$5 Billed Once credit card or paypal SpaceDaily Monthly Supporter \$5 Billed Monthly paypal only

 .

Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth

 Tweet

Los Angeles CA (SPX) Mar 23, 2015
Just like the Pharaoh Cheops, who ruled the ancient Old Kingdom of Egypt, ESA's CHaracterising ExOPlanet Satellite (CHEOPS) could be someday ruling in the field of exoplanet hunting. It will be the first mission dedicated to search for transits by means of ultrahigh precision photometry on bright stars already known to host planets. "CHEOPS looks at stars that are already known to host planets a ... read more

 Extent of Moon's giant volcanic eruption is revealed Yutu Changes Everything We Thought We Knew About Our Moon Extent of moon's giant volcanic eruption is revealed NASA's LRO Spacecraft Finds March 17, 2013 Impact Crater and More Mars One's CEO Bas Lansdorp answers questions about mission feasibility Could Water Have Carved Channels On Mars Half A Million Years Ago? MARSDROP Microprobes Could Expand Spacecraft Mission Capabilities NASA Spacecraft Detects Aurora and Mysterious Dust Cloud around Mars Small Staff has Big Impact Showing How NASA Can Engage Students TED Prize winner wishes for archive of human wisdom The Science Of The Start-Up From cancer-battling bacteria to life on Mars at TED China completes second test on new carrier rocket's power system China's Yutu rover reveals Moon's "complex" geological history China's Space Laboratory Still Cloaked China has ability but no plan for manned lunar mission: expert One-Year Crew Set for Launch to Space Station Russia, US May Sign New Deal to Send Astronauts to ISS Lockheed Martin reveals new method for resupplying space station Testing astronauts' lungs in Space Station airlock Arianespace selected by Airbus to launch EDRS-C Satellite US to Scrap Delta IV Launch Vehicle in Favor of Russian-Made Rocket Proton launches Express AM-7 satellite for Russian Government DoD Works to Build Competition Into Space Launches Our Solar System May Have Once Harbored Super-Earths SOFIA Finds Missing Link Between Supernovae and Planet Formation ESA's CHEOPS Satellite: The Pharaoh of Exoplanet Hunting Some habitable exoplanets could experience wildly unpredictable climates Japan military eyes recruits with cutesy smartphone game USMC orders targeting system from Elbit Systems America Intelsat EpicNG Completes Major Milestone on the Road to 2016 Launch Want to snag a satellite? Try a net

 The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.