Astronomy (Methodology > Division Astrobiology)

Most astronomy-related astrobiological research falls into the category of extrasolar planet (exoplanet) detection, the hypothesis being that if life arose on Earth then it could also arise on other planets with similar characteristics. To that end, a number of instruments designed to detect 'Earth-like' exoplanets are under development, most notably NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin programs.[27] Additionally, NASA plans to launch the Kepler mission in 2008, and the French Space Agency has already launched the COROT space mission.[28][29] There have also been several less ambitious ground-based efforts are also underway (see exoplanet).

The goal of these missions is not only to detect Earth-sized planets but also to directly detect light from the planet so that it may be studied spectroscopically. By examining planetary spectra it will be possible to determine the basic composition of an extrasolar planet's atmosphere and/or surface; given this knowledge, it may be possible to assess the likelihood of life being found on that planet. A NASA research group, the Virtual Planet Laboratory[1] (VPL), is using computer modelling to generate a wide variety of 'virtual' planets to see what they would look like if viewed by TPF or Darwin. It is hoped that once these missions come online, their spectra can be cross-checked with these 'virtual' planetary spectra for features that might indicate the presence of life. The photometry (astronomy) temporal variability of extrasolar planets may also provide clues to their surface and atmospheric properties. One mission was planned to the Jupiter moon, Europa, before recent cuts by NASA. This mission would have searched for life in the ocean of this moon.

An estimate for the number of planets with (intelligent) extraterrestrial life can be gleaned from the Drake equation, essentially an equation expressing the probability of intelligent life as the product of factors such as the fraction of planets that might be habitable and the fraction of planets on which life might arise:[30]

N = R^{*} ~ \times ~ f_{p} ~ \times ~ n_{e} ~ \times ~ f_{l} ~ \times ~ f_{i} ~ \times ~ f_{c} ~ \times ~ L

However, whilst the rationale behind the equation is sound, it is unlikely that the equation will be constrained to reasonable error limits any time soon. The first term, Number of Stars, is generally constrained within a few orders of magnitude. The second and third terms, Stars with Planets and Planets with Habitable Conditions, are being evaluated for the Sun's neighbourhood. Another associated topic is the Fermi paradox, which suggests that if intelligent life is common in the universe then there should be obvious signs of it. This is the purpose of projects like SETI, which tries to detect signs of radio transmissions from intelligent extraterrestrial civilizations.

Another active research area in astrobiology is solar system formation. It has been suggested that the peculiarities of our solar system (for example, the presence of Jupiter as a protective 'shield' or the planetary collision which created the Moon) may have greatly increased the probability of intelligent life arising on our planet.[31][32] No firm conclusions have been reached so far.

Major questions in astronomy

Although the scientific discipline of astronomy has made tremendous strides in understanding the nature of the universe and its contents, there remain some important unanswered questions. Answers to these may require the construction of new ground- and space-based instruments, and possibly new developments in theoretical and experimental physics.

* What is the origin of the stellar mass spectrum? That is, why do astronomers observe the same distribution of stellar masses—the initial mass function—apparently regardless of the initial conditions?[51] A deeper understanding of the formation of stars and planets is needed.
* Is there other life in the Universe? Especially, is there other intelligent life? If so, what is the explanation for the Fermi paradox? The existence of life elsewhere has important scientific and philosophical implications.[52][53]
* What is the nature of dark matter and dark energy? These dominate the evolution and fate of the cosmos, yet we are still uncertain about their true natures.[54]
* Why did the universe come to be? Why, for example, are the physical constants so finely tuned that they permit the existence of life? Could they be the result of cosmological natural selection? What caused the cosmic inflation that produced our homogeneous universe?[55]
* What will be the ultimate fate of the universe?[56]