The characterization of the atmospheres of habitable-zone Earth-mass exoplanets that transit across main-sequence stars, let alone the detection of bio-markers in their atmospheres, will be challenging even with future facilities. It has been noted that white dwarfs (WDs) have long-lived habitable zones and that a large fraction of WDs may host planets. We point out that during a transit of an Earth-mass planet across a WD, the planet's atmospheric transmission spectrum obtains a much higher contrast over the stellar background compared to a main-sequence host, because of the small surface area of the WD. The most prominent bio-marker in the present-day terrestrial atmosphere, molecular oxygen, is readily detectable in a WD transit via its A-band absorption at \~0.76 micron. A potentially life-sustaining Earth-like planet transiting a WD can be found by assembling a suitable sample of \~500 WDs and then surveying them for transits using small telescopes. If and when such a transiting case is found, the O\_2 absorption in the planetary atmospheric transmission spectrum would be detectable with the James Webb Space Telescope (JWST) in about 5 hours of total exposure time, integrated over 160 2-minute transits. Characterization of the planet atmosphere using other tracers such as water vapour and CO\_2 will be considerably easier. We demonstrate this future discovery space by simulating a possible transmission spectrum that would be obtained with JWST.
%0 Journal Article
%1 Loeb2013
%A Loeb, Abraham
%A Maoz, Dan
%D 2013
%K 2013 astrobiology detection habitability planets rocky
%N January
%P 5
%T Detecting bio-markers in habitable-zone earths transiting white dwarfs
%U http://arxiv.org/abs/1301.4994
%V 000
%X The characterization of the atmospheres of habitable-zone Earth-mass exoplanets that transit across main-sequence stars, let alone the detection of bio-markers in their atmospheres, will be challenging even with future facilities. It has been noted that white dwarfs (WDs) have long-lived habitable zones and that a large fraction of WDs may host planets. We point out that during a transit of an Earth-mass planet across a WD, the planet's atmospheric transmission spectrum obtains a much higher contrast over the stellar background compared to a main-sequence host, because of the small surface area of the WD. The most prominent bio-marker in the present-day terrestrial atmosphere, molecular oxygen, is readily detectable in a WD transit via its A-band absorption at \~0.76 micron. A potentially life-sustaining Earth-like planet transiting a WD can be found by assembling a suitable sample of \~500 WDs and then surveying them for transits using small telescopes. If and when such a transiting case is found, the O\_2 absorption in the planetary atmospheric transmission spectrum would be detectable with the James Webb Space Telescope (JWST) in about 5 hours of total exposure time, integrated over 160 2-minute transits. Characterization of the planet atmosphere using other tracers such as water vapour and CO\_2 will be considerably easier. We demonstrate this future discovery space by simulating a possible transmission spectrum that would be obtained with JWST.
@article{Loeb2013,
abstract = {The characterization of the atmospheres of habitable-zone Earth-mass exoplanets that transit across main-sequence stars, let alone the detection of bio-markers in their atmospheres, will be challenging even with future facilities. It has been noted that white dwarfs (WDs) have long-lived habitable zones and that a large fraction of WDs may host planets. We point out that during a transit of an Earth-mass planet across a WD, the planet's atmospheric transmission spectrum obtains a much higher contrast over the stellar background compared to a main-sequence host, because of the small surface area of the WD. The most prominent bio-marker in the present-day terrestrial atmosphere, molecular oxygen, is readily detectable in a WD transit via its A-band absorption at \~{}0.76 micron. A potentially life-sustaining Earth-like planet transiting a WD can be found by assembling a suitable sample of \~{}500 WDs and then surveying them for transits using small telescopes. If and when such a transiting case is found, the O\_2 absorption in the planetary atmospheric transmission spectrum would be detectable with the James Webb Space Telescope (JWST) in about 5 hours of total exposure time, integrated over 160 2-minute transits. Characterization of the planet atmosphere using other tracers such as water vapour and CO\_2 will be considerably easier. We demonstrate this future discovery space by simulating a possible transmission spectrum that would be obtained with JWST.},
added-at = {2013-08-04T00:21:42.000+0200},
archiveprefix = {arXiv},
arxivid = {1301.4994},
author = {Loeb, Abraham and Maoz, Dan},
biburl = {https://www.bibsonomy.org/bibtex/2e3ba4cecefae4a28e48f901ece088a66/danielcarrera},
eprint = {1301.4994},
file = {:home/daniel/Downloads/1301.4994v1.pdf:pdf},
interhash = {7244757da8e8db8069b4cca0c98f41d5},
intrahash = {e3ba4cecefae4a28e48f901ece088a66},
keywords = {2013 astrobiology detection habitability planets rocky},
month = jan,
number = {January},
pages = 5,
timestamp = {2013-08-04T21:03:32.000+0200},
title = {{Detecting bio-markers in habitable-zone earths transiting white dwarfs}},
url = {http://arxiv.org/abs/1301.4994},
volume = 000,
year = 2013
}