Related papers: Are we visible to advanced alien civilizations?
Civilization cannot sustain an exponential growth for long time even when neglecting numerous laws of physics! In this paper, we examine what are fundamental obstacles to long term survival of a civilization and its possibility to colonize…
The forthcoming space missions, able to detect Earth-like planets by the transit method, will a fortiori also be able to detect the transit of artificial planet-size objects. Multiple artificial objects would produce lightcurves easily…
Supernovae in distant galaxies that are gravitationally lensed by foreground galaxy clusters make excellent cosmological candles for measuring quantities like the density of the Universe in its various components and the Hubble constant.…
At large redshifts, a cluster or group may be too distant for the galaxies within the cluster to be detected individually. However, the light from these ``undetected'' galaxies still modulates the surface brightness of the background sky.…
The Drake equation has been used many times to estimate the number of observable civilizations in the Galaxy. However, the uncertainty of the outcome is so great that any individual result is of limited use, as predictions can range from a…
The universe should be dark at energies exceeding $\sim 5\times 10^{19}$ eV. This simple but solid prediction of our best known particle physics is not confirmed by observations, that seem to suggest a quite different picture. Numerous…
For centuries, astronomers have discussed the possibility of inhabited worlds - from Herschel's 18th-century observations suggesting Mars may host life, to the systematic search for technosignatures that began in the 1960s using radio…
The challenge for optical detection of terrestial planet is the 25 magnitude brightness contrast between the planet and its host star. This paper introduces a new pupil design that produces a very dark null along its symmetry axis. By…
We report on a survey devoted for the search of exo-planets around young and nearby stars carried out with NACO at the VLT. The detection limit for 28 among the best available targets vs. the angular separation from the star is presented.…
We briefly review the beginnings of HI astronomy, proceed to an assessment of our current capabilities in this area, and continue by considering what will be necessary to push back the frontier to cosmological distances. We then consider…
During the last few years, considerable effort has been directed towards large-scale (>> $1 Billion US) missions to detect and characterize earth-like planets around nearby stars, such as the Terrestrial Planet Finder Interferometer (TPF-I)…
How long a technological civilization remains active, and what determines whether it collapses or persists, is a central question for both projecting humanity's future and assessing the prevalence of detectable intelligence in the galaxy.…
High-energy astrophysical events that cause galaxy-scale extinctions have been proposed as a way to explain or mollify the Fermi Paradox, by making the universe at earlier times more dangerous for evolving life, and reducing its present-day…
Over the past decade, radio detection of cosmic rays has matured from small-scale prototype experiments to installations spanning several km$^2$ with more than a hundred antennas. The physics of the radio signal is well understood and…
The limitations of current technology do not allow one to foresee the expansion of the humankind beyond our planet for at least a few decades. Furthermore, the laws of physics, as for as they are known, preclude any form of traveling beyond…
We significantly constrain the sky position, distance, and mass of a possible additional, distant planet in the solar system by examining its influence on the distance between Earth and the Cassini Spacecraft. Our preferred region is…
By providing sensitive sub-arcsecond images and integral field spectroscopy in the 25 - 400 micron wavelength range, a far-IR interferometer will revolutionize our understanding of planetary system formation, reveal otherwise-undetectable…
We ask if Earth-like planets (terrestrial mass and habitable-zone orbit) can be detected in multi-planet systems, using astrometric and radial velocity observations. We report here the preliminary results of double-blind calculations…
For centuries, humanity wondered if there were other worlds like ours in the Universe. For about a quarter of a century, we have known that planetary systems exist around other stars, and more than 3800 exoplanetary systems have been…
In the present paper we consider the Type-2.x and Type-3.x extraterrestrial von-Neumann probes and study the problem of their detectability by the world's largest radio telescope: the Five-hundred-meter Aperture Spherical Radio Telescope…