Tag: exoplanets

Ariel’s Search For Extraterrestrial Life

Article by Giovanni Mussini                                 November 30, 2020                                      (oxfordstudent.com)

• The European Ariel space telescope (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) has been given the go-ahead for launch in 2029. Intended to map the atmospheres and chemical environments of distant exoplanets, the Ariel spacecraft’s search range will target hundreds of planets in the hotter Goldilocks zones in order to build a standard model of atmospheres based on the attributes of its host star and planetary environments.

• Different atmospheric components imprint distinctive patterns on the starlight beaming through. While not conducive to life itself, planets having an “atmospheric cauldron” that can circulate freely allows Ariel to capture more representative spectral signatures to create a standard model.

• The presence of unique ‘biosignatures’ arise due to the unique self-organizing properties of life. But at the same time, anomalies are unlikely to be spectacular or self-evident. Take Venus for example. Venus is a planetary inferno bathed in sulphuric acid rains, with a mean surface temperature high enough to melt lead. The biosignature of phosphine – a chemical created by living organisms – was detected in the cooler high-altitude Venusian clouds. But it is uncertain whether the presence of phosphine is due to biological activity, exotic abiotic chemistries, or a blip in the data.

• Time and again, attempts to map molecular pathways to life from simple organics have failed. Promising places – such as deep-sea hydrothermal vents – have proven an unlikely starting point for biology. The necessary interdependence of proteins, membranes, and nucleic acids may require simultaneous assembly, rather than in a stepwise fashion. Across the cosmos, the least unlikely places for spontaneous life to occur might be mineral-rich ephemeral pools bombarded by UV radiation. This is bad news for life. Temperate gas giants, oceanic super-Earths, and promising icy moons would all be ruled out. Perhaps biology really needs a planet like ours to get started: rocky, temperate, and tectonically active, with emerging landmasses. Places like these probably do exist, dotting the spiral arms of our galaxy.

• If the history of the Earth is any guide, evolution may rise to the challenges of alien worlds where there is living material to work from in the first place. Even on Venus, where balmy oceans existed as recently as 700 million years ago, life may have escaped the planet’s descent into a greenhouse nightmare by migrating to the higher atmosphere. As robotic emissaries and telescopic eyes return troves of data on far-flung worlds, sensational discoveries may come. But we are probably in for a long wait.

 

After years in the pipeline, the Ariel space telescope has been given the go-ahead for launch in 2029. This spacecraft is the brainchild of a cooperative European endeavour to map the atmospheres and chemical environments of far-flung worlds. If all goes well, Ariel will bring planetary science out of the solar system, and into uncharted territory. However, alien hunters may have to keep their enthusiasm in check – for now.

Ariel will peer at a range of exoplanets, but its focus will be on worlds baked by their home stars at over 320 ºC. By all measures, these are extremely unlikely abodes for life. Even so, the detection technique available to Ariel makes them attractive targets.

The telescope will search for faint chemical fingerprints as planets transit in front of their star. By only soaking up particular wavelengths, different atmospheric components imprint distinctive patterns on the starlight beaming through. The closer a planet is to its star, the more frequent the transits and the opportunities to carry out observations. Another perk of closely orbiting hellish worlds is that they wear their atmospheric makeup on their sleeve. Whereas gases may sink or coalesce into clouds on cooler planets, in an atmospheric cauldron they can circulate freely, allowing Ariel to capture more representative spectral signatures.

Ariel’s predecessors had to split their focus between probing exoplanetary atmospheres and other tasks. Instead, the ESA spacecraft will be solely dedicated to this endeavour, broadening the search to an unprecedented number of targets – hundreds of them. This is a cause for excitement. By gathering data en masse, Ariel will build towards something that has been sorely lacking in the quest for living worlds: a standard model of how atmospheres arise based on their host star and planetary environments. Understanding what is in line with this model, and what is not, may help scientists home in on genuine anomalies.

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Inside The Search For Another Habitable Planet Within 100 Light Years Of Earth

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Article by Jamie Carter                             November 25, 2019                               (forbes.com)

• The Habitable Exoplanet Hunting Project is a global attempt to discover potentially habitable exoplanets within 100 light years, involving a network of over 25 amateur astronomy observatories around the globe. It will focus on ten stars within 100 light years of Earth, all of which have confirmed transiting exoplanets within the so-called “habitable zone”.

• The exoplanet known as Kepler 442b, which orbits a K-type star and could be even more habitable than Earth. M-type stars, or ‘red dwarfs’, are small, cool stars that are impossible to see with the naked eye, but they are by far the most common type of star in our region of the Milky Way. G, K and M-type stars are “the stars that are most likely to host exoplanets with water on their surface because they don’t flare,” says Alberto Caballero, an amateur astronomer at The Exoplanets Channel and the coordinator of the ‘Habitable Exoplanet Hunting Project’. “If a star flares, it can damage the atmosphere of the exoplanets.”

• The ideal exoplanet is a dense and rocky “super Earth” planet, almost seven times bigger than Earth, called LHS 1140 b, orbiting within the habitable zone of the red dwarf star LHS 1140 about 40 light years distant in the constellation of Cetus. Three other prime candidates would be:
Proxima Centauri b – an exoplanet orbiting an M-type red dwarf star 4.24 light years away in the constellation of Centauri;
Tau Ceti e – an exoplanet orbiting an M-type red dwarf star 11.9 light years away in the constellation of Cetus;
Teegarden b -an exoplanet orbiting an M-type red dwarf star 12 light years away in the constellation of Aries.

• Tau Ceti e is a “super Earth” exoplanet almost four times the mass of Earth. It is so massive that you can see Ceti in the constellation Cetus with the naked eye, level with Orion’s Belt in the northern hemisphere.

• The Project has been careful to ignore stars that have Jupiter-sized gas giant exoplanets in their habitable zones unless the star is so big that it may not adversely affect other exoplanets in the star’s orbit. “We’re trying to monitor the stars 24/7 for about two months,” says Caballero, “so it’s easier for us if we focus on M-type stars because any exoplanets would have really short orbital periods. But the most ideal ones are K-type stars.”

• NASA’s orbiting space telescope, the Transiting Exoplanet Survey Satellite or ‘TESS’ has already found 29 confirmed exoplanets. Caballero says, “So far (TESS has) not detected any potentially inhabited planets, but it’s only just starting on the northern hemisphere.” In the long term, Caballero thinks that studying an exoplanet’s ‘biosignature’ from its light spectrum with better instruments will yield the most potentially habitable exoplanets. Says Caballero, “[I]t’s all about having better technology.”

[Editor’s Note]  The Habitable Hunting Project might need to strike Proxima b off of their list. In March 2018, the Cerro Tololo Inter-American Observatory in the Chilean Andes, reported that the red dwarf star, Proxima Centauri, fired off a powerful “superflare” which could be seen from the Earth. (see Space.com article here) It briefly boosted the star’s brightness by a factor of 68. The astronomy team noted that “life would struggle to survive in the areas of Proxima b exposed to these flares.”

 

The search for extraterrestrial life is easily the most profound question in modern astronomy, but it’s hampered by a lack of both technology and time.

Is life possible beyond the solar system? If we’re ever to find out, we must study and categorise the stars to answer this one, simple question: if we had a spaceship we could send to the nearest Earth-like planet, which one would we send it to?

            Alberto Caballero

When astronomers find exoplanets, they put them on a list marked “potentially habitable” or else use them as clues that habitable exoplanets may lurk in their star system. Most of them are exceptionally far away. So far we’ve found three close exoplanets that orbit within a star’s so-called “habitable zone” where liquid water could exist on its surface.

If astronomers had to choose a planet in another star system to send a spaceship, these three would be prime candidates:

• Proxima Centauri b: an exoplanet orbiting an M-type red dwarf star 4.24 light years away in the constellation of Centauri.

• Tau Ceti e: an exoplanet orbiting an M-type red dwarf star 11.9 light years away in the constellation of Cetus.

• Teegarden b: an exoplanet orbiting an M-type red dwarf star 12 light years away in the constellation of Aries.

Where will we most likely find others? Though the vast majority of star systems remain unexplored, we know of plenty that contain planets not in the star’s habitable zone. These star systems are surely the best places to look.

Cue the Habitable Exoplanet Hunting Project, a global attempt attempt to discover potentially habitable exoplanets within 100 light years, and involving over 25 observatories.

What is the Habitable Exoplanet Hunting Project?

It’s a network of amateur astronomy observatories around the globe—from the U.S. and Uzbekistan to South Africa and Australia—that is studying 10 stars within 100 light years for signs of new, as yet unfound exoplanets. All of the stars that will be studied already have confirmed transiting exoplanets outside the so-called “habitable zone”. “We’ve chosen observatories in deserts or high regions or mountains because weather is always the main problem with projects like this,” says Alberto Caballero, an amateur astronomer at The Exoplanets Channel and the coordinator of the Habitable Exoplanet Hunting Project. “But we will need to find more observatories in the southern hemisphere.”

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Nobel Prize in Physics Awarded for Research on Exoplanets and the Structure of the Universe

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Article by Sarah Kaplan                 October 8, 2019                 (washingtonpost.com)

• On October 8th, the Nobel Prize in physics was awarded jointly to James Peebles of Princeton University who theorized the existence of ‘dark matter’ and ‘dark energy’ to explain what makes up the 95 percent of the universe that we do not yet understand, and Michel Mayor along with Didier Queloz of the University of Geneva who in 1995 discovered the first extra-solar ‘exoplanet’ orbiting around a sun-like star.

• When astronomers stumbled upon a cosmic radiation that suffuses throughout space, fifty years ago, it provided a road map of the history of the universe since the “Big Bang”. In short, in one-millionth of a second, “lumps” of matter were created which would evolve into galaxies.

• Crediting the research of his contemporary Soviet astronomers in the 1960s, Peebles theorized that something must exist – an invisible force – that drives the expansion of the universe while holding the galaxies together. Yet everything ever detected by a scientific instrument and everything that has yet to be found makes up only 5 percent of the universe. Thus dark matter/dark energy was born to fill the void. However some argue that it was Carnegie Institution astronomer Vera Rubin who proved the existence of dark matter but was never credited with an award.

• Mayor and Queloz are credited with finding the first exoplanet outside of our solar system in 1995. They did this by measuring the wobble in a distant star by the shifts in light it emitted. From this they could determine the size and distance of a companion planet, both orbiting a common center of mass. The planet they found, dubbed 51 Pegasi b, is large, gaseous and hot like Jupiter, but is so close to its star that it takes just four days to complete an orbit. Queloz was a graduate student working with Mayor, a Professor Emeritus.

• “New science is very rarely done by just one person … and there were a lot people who made important contributions before and since then,” said Johanna Teske, an exoplanet astronomer at Carnegie Observatories. But Mayor and Queloz’s discovery “was really a turning point for the field.” Once the method was devised, astronomers across the globe were looking for the telltale wobble of a planet-hosting sun. Over 4,000 exoplanets have been found to date.

• Nobel Committee member Ulf Danielsson noted that ‘somewhere in the vast and inscrutable universe, on one of those strange and distant worlds, it’s possible that some other form of life exists’. “Our view of our place in the universe will never be the same again.” It might take years, or centuries, or even millennia, Danielsson said. But he holds out hope that one day humanity will find evidence that we are not alone.

 

A cosmologist who revealed that the universe was made mostly of invisible matter and energy, and two scientists who detected the first planet orbiting an alien star, were jointly awarded the 2019 Nobel Prize in physics Tuesday.

                  Michel Mayor

By studying the earliest moments after the birth of the universe, James Peebles of Princeton University developed a theoretical framework for the evolution of the cosmos that led to the understanding of dark energy and dark matter — substances that can’t be observed by any scientific instruments but nonetheless make up 95 percent of the universe.

              Didier Queloz

Fellow laureates Michel Mayor and Didier Queloz of the University of Geneva revolutionized astronomy, the Nobel Committee said, when in 1995 they announced the discovery of a large, gaseous world circling a star 50 light-years from our sun — the first extrasolar planet found around a sun-like star. In the decades since, scientists have detected thousands more of these exoplanets, and astronomers now think our universe contains more planets than stars.

“This year’s Nobel laureates in physics have painted a picture of a universe far stranger and more wonderful than we ever could have imagined,” Ulf Danielsson, a Nobel Committee member, said at a news conference Tuesday. “Our view of our place in the universe will never be the same again.”

               James Peebles

For almost a century, scientists have theorized that the universe began with a big bang, growing from a hot, dense particle soup into the current collection of dust, stars and galaxies flung across a vast and still-expanding space. Fifty years ago, a pair of radio astronomers stumbled upon the signature of those earliest days of expansion: the cosmic microwave background, a faint form of radiation that suffuses the entire sky.

This radiation is a “gold mine” for physicists, the Nobel Committee said. By analyzing tiny variations in this ancient afterglow, scientists can peer back in time to understand how the universe evolved. Peebles studied the temperature of the cosmic microwave background to understand the matter that was created in the big bang.

“It was, conceptually, a door-opening event,” said observational cosmologist Sandra Faber, a staff member at University of California Observatories. “It showed that known laws of physics could explain the universe when it was only 100 seconds old. Isn’t that amazing?”

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