From Red Dot: “Is there life around the nearest stars?

Red Dots

13th June 2017
Avi Loeb


Is there extra-terrestrial life just outside the solar system? The recent discovery of Proxima b [1], a habitable Earth-mass planet next to the nearest star, opened a unique opportunity in the search for extra-terrestrial life.

Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

It is much easier to study nearby habitats for life, either by remote sensing of the feeble radiation signals from biologically-produced molecules (e.g. oxygen) or by sending spacecrafts that will image the planet’s surface or collect samples from its atmosphere through a close encounter. The Breakthrough Starshot initiative, announced in April 2016 (and whose advisory committee I chair) aims to send lightweight (gram scale) probes to the nearest stars at a fifth of the speed of light, so as to inform us of nearby life-hosting environments within our generation. To properly select the Starshot targets, we would like to know which nearby stars host habitable planets like Proxima b. The treasure of data expected from the Red Dots campaign will be invaluable for guiding and motivating the Starshot project.

Artistic’s conception showing the Starshot project concept. A laser beam propels a light sail towards a nearby exoplanet such as Proxima b. The sail carries on its center a lightweight probe with several measuring instruments. Starshot will start soon the first five-year phase of technology demonstration at a funding level of $100M, provided by the entrepreneur and physicist Yuri Milner (Credit: Breakthrough Starshot).

The chemistry of life as we know it requires liquid water, but being at the right distance from the host star for a comfortable temperature on the planet’s surface, is not a sufficient condition. The planet also needs to have an atmosphere. In the absence of an external atmospheric pressure, the warming of water ice transforms it into directly into gas phase rather than liquid. The warning sign is just next door: Mars has a tenth of the Earth’s mass and lost its atmosphere. Does Proxima b have an atmosphere? If so, the atmosphere and any surface ocean it sustains, will moderate the temperature contrast between its permanent day and night sides. In collaboration with Laura Kreidberg, we showed [2] that the James Webb Space Telescope, scheduled for launch in October 2018, will be able to distinguish between the temperature contrast expected if Proxima b is bare rock compared to the case where its climate is moderated by an atmosphere.

NASA/ESA/CSA Webb Telescope annotated

Proxima Centauri is a red dwarf star with 12% of the mass of the Sun. Another dwarf star, TRAPPIST-1, with 8% of the solar mass, was discovered recently [3],[4] to host 3 habitable planets out of a total of 7 and if life forms in one of the three it will likely spread to the others [5].

The TRAPPIST-1 star, an ultracool dwarf, is orbited by seven Earth-size planets (NASA).

ESO Belgian robotic Trappist National Telescope at Cerro La Silla, Chile interior

ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile

Such dwarf stars have a lifetime that is up to a thousand times longer than the Sun. Hence, they provide excellent prospects for life in the distant future, a trillion years from now, long after the Sun will die and turn into an Earth-size cold remnant, known as a white dwarf. I therefore advise my wealthy friends to buy real estate on Proxima b, since its value is likely to go up dramatically in the future. But this also raises an important scientific question: is life most likely to emerge at the present cosmic time near a star like the Sun? By studying the habitability of the Universe throughout cosmic history from the birth of the first stars 30 million years after the Big Bang to the death of the last stars in ten trillion years, I concluded [6],[7] that unless habitability around low mass stars is suppressed, life is most likely to exist near dwarf stars like Proxima or TRAPPIST-1 ten trillion years from now. This highlights the importance of searching for life around these nearby red dwarf stars, namely the Red Dots campaign. Finding bio-signatures in the atmospheres of transiting Earth-mass planets around such stars will determine whether present-day life is indeed premature or typical from a cosmic perspective.

References [no links provided]:

Anglada-Escudé G. et al. “A Terrestrial Candidate in a Temperate Orbit Around Proxima Centauri”, Nature, 536, 437 (2016).
Kreidberg, L. & Loeb, A. “Prospects for Characterising the Atmosphere of Proxima b”, ApJ, 832, L12 (2016).
Gillon, M. et al. “Temperate Earth-Sized Planets Transiting a Nearby Ultracool Dwarf Star”, Nature, 533, 221 (2016).
Gillon, M, et al. “Seven temperate terretrial planets around the nearby ultracool dwarf star TRAPPIST-1”, Nature, 542, 456–460
Lingam, M., & Loeb, A. “Enhanced Interplanetary Panspermia in the TRAPPIST-1 System”, PNAS, in press (2017); arXiv: 1703.00878.
Loeb, A., Batista, R. A., & Sloan, D. “Relative Likelihood for Life as a Function of Cosmic Time”, JCAP, 8, 40 (2016). “
Loeb, A. “On the Habitability of Our Universe”, chapter for the book “Consolidation of Fine Tuning”, edited by R. Davies, J. Silk and D. Sloan (Oxford University, 2017); arXiv:1606.0892

See the full article here .

It seems to me that the author should have made mention of the Breakthrough Listen Project, a modest initiative using ground based telescopic assets.

Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

GBO radio telescope, Green Bank, West Virginia, USA


CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

Not to mention also missing

Breakthrough Starshot Initiative Observatories

ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

SPACEOBS, the San Pedro de Atacama Celestial Explorations Observatory is located at 2450m above sea level, north of the Atacama Desert, in Chile, near to the village of San Pedro de Atacama and close to the border with Bolivia and Argentina

SNO Sierra Nevada Observatory is a high elevation observatory 2900m above the sea level located in the Sierra Nevada mountain range in Granada Spain and operated maintained and supplied by IAC

Teide Observatory in Tenerife Spain, home of two 40 cm LCO telescopes

Observatori Astronòmic del Montsec (OAdM), located in the town of Sant Esteve de la Sarga (Pallars Jussà), 1,570 meters on the sea level

Bayfordbury Observatory,approximately 6 miles from the main campus of the University of Hertfordshire

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Stem Education Coalition

Red dots is a project to attempt detection of the nearest terrestrial planets to the Sun. Terrestrial planets in temperate orbits around nearby red dwarf stars can be more easily detected using Doppler spectroscopy, hence the name of the project.