Evolution of Mid–IR Excess Around Sun–like Stars:ABSTRACT
Constraints on Models of Terrestrial Planet Formation
M.R. Meyer, J.M. Carpenter, E.E. Mamajek, L.A. Hillenbrand, D. Hollenbach, A.
Moro–Martin, J.S. Kim, M.D. Silverstone, J. Najita, D.C. Hines, I. Pascucci, J.R.
Stauffer, J. Bouwman, & D.E. Backman
We report observations from the Spitzer Space Telescope (SST) regarding the frequency of 24 μm excess emission toward sun-like stars. Our unbiased sample is comprised of 309 stars with masses 0.7-2.2 M⊙ and ages from <3>3 Gyr that lack excess emission at wavelengths 8 μm. We identify 30 stars that exhibit clear evidence of excess emission from the observed 24/8μm flux ratio. The implied 24 μm excesses of these candidate debris disk systems range from 13 % (the minimum detectable) to more than 100% compared to the expected photospheric emission. The frequency of systems with evidence for dust debris emitting at 24 μm ranges from 8.5–19 % at ages greater than 300 Myr to greater than 4 % for older stars. The results suggest that many, perhaps most, sun-like stars might form terrestrial planets.
The researchers looked at 309 sun-like stars, grouped them by age, and then used the Spitzer infrared space telescope to look for dust around them. The dust glows in the infrared spectrum from the heat of the local star, and the temperature of the glow is proportional to the distance from the star.
About 10% of the stars in the Milky Way are like our Sun. If just 10% of them have rocky planets, as this study indicates, there may be a billion planets like Earth orbiting stars in our galaxy alone! Lower mass stars can form planetary systems too, of course, and there are a whole lot more of them then stars like ours. So there may be several billion terrestrial planets in the galaxy and there are hundreds of billions of galaxies in the Universe.
Read the rest of the paper at http://arxiv.org/pdf/0712.1057