Meraviglia o terrore?

In Italian only

Source: www.focus.it

Meraviglia o terrore? Quale delle due per la nuova scienza che progetta di costruire macchine delle dimensioni di una molecola, o più piccole, capaci di gareggiare con gli atomi? Macchine, e non per modo di dire: hanno motori, computer di bordo e strumenti per "fare qualcosa" (anche dentro di noi!). Tutto proporzionato, è naturale, e tutto in violazione alle comuni leggi della fisica: la gravità, la forza di van der Waals (attrazione intermolecolare), la seconda legge della termodinamica (il calore fluisce da un corpo caldo a uno freddo), la tensione superficiale... contano poco o nulla per un robot grande un atomo. È ANCORA FUTURO Il primo a sognare macchine così, nel 1959, è stato Richard Feynman (Nobel per la fisica 1965), quando ancora non esistevano né la parola "nanotecnologia" né gli strumenti per assemblare nanostrutture, come il microscopio a forza atomica (1986), uno dei principali attrezzi per l'osservazione e la manipolazione della materia in scala nanometrica (vedi "La scienza incontra l'arte"). A che punto siamo oggi? Per le idee rappresentate in queste pagine dai disegni di tre artisti è ancora piena fantascienza. Sono però "mondi possibili" e la nostra domanda è, di nuovo, sogno o incubo? Che cosa ne pensi? I MANGIA-LIPIDI Non c'è tempo da perdere: quest'arteria è ingombra di placche di grasso! Da smaltire, prima che succeda qualcosa di peggio. Una flotta di nanorobot rimuove il materiale lipidico e lo digerisce direttamente sul posto.

(© Tim Fonseca)

[Elisabetta Intini, 15 maggio 2008]

Team led by a Bulgarian, finds largest exoplanet yet

The planet has a large radius but a low density.

Source: www.bbc.co.uk

An international team of astronomers has discovered the largest known planet orbiting another star.

The "transiting" planet - meaning one that passes in front of its parent star as seen from Earth - is about 70% larger than Jupiter.

But the gas giant has a much lower mass than Jupiter - the biggest planet in our Solar System - making it of extremely low density.

The new exoplanet, called TrES-4, is located in the constellation of Hercules and was discovered by a team working on the Transatlantic Exoplanet Survey (TrES). It is mostly made up of hydrogen.

TrES-4 circles the star GSC02620-00648, which lies about 1,435 light-years away from Earth. Being only about seven million km (4.5 million miles) from its parent star, the planet is also very hot, about 1,327C (1,600 K; 2,300F).

"TrES-4 is the largest known exoplanet," said lead author Georgi Mandushev, from the Lowell Observatory in Flagstaff, US.

Surprising size

It is so big, in fact, that its size is difficult to explain using current theories about superheated giant planets.

"We continue to be surprised by how relatively large these giant planets can be," says Francis O'Donovan, a graduate student in astronomy at the California Institute of Technology (Caltech) which operates one of the TrES telescopes.

"But if we can explain the sizes of these bloated planets in their harsh environments, it may help us better understand our own Solar System planets and their formation."

Its density of 0.2 grams per cubic centimetre is so low that the planet would, in theory, float on water.

By definition, a transiting planet passes directly between the Earth and the star, blocking some of the star's light and causing a slight drop in its brightness.
"TrES-4 blocks off about 1% of the light of the star as it passes in front of it," said Dr Mandushev.

"With our telescopes and observing techniques, we can measure this tiny drop in the star's brightness and deduce the presence of a planet there."

Planet TrES-4 makes a complete revolution around its parent star every 3.55 days, so a year on this planet is shorter than a week on Earth.

The TrES is a network of three 10cm telescopes in Arizona, California and the Canary Islands.
In order to accurately measure the size of the TrES-4 planet, astronomers used the 0.8m telescope at the Lowell Observatory in Arizona, the 1.2m telescope at the Whipple Observatory, also in Arizona, and the 10m Keck telescope in Hawaii.

New 'super-Earth' found in space

Mass: Five times Earth's mass
Orbit: 13 days
Temperature: 0C - 40C
Distance: 20.5 light years
Constellation: Libra

The new planet is not much bigger than the Earth

Source: www.bbc.co.uk

Astronomers have found the most Earth-like planet outside our Solar System to date, a world which could have water running on its surface.

The planet orbits the faint star Gliese 581, which is 20.5 light-years away in the constellation Libra.
Scientists made the discovery using the Eso 3.6m Telescope in Chile.
They say the benign temperatures on the planet mean any water there could exist in liquid form, and this raises the chances it could also harbour life.
"We have estimated that the mean temperature of this 'super-Earth' lies between 0 and 40 degrees Celsius, and water would thus be liquid," explained Stephane Udry of the Geneva Observatory, lead author of the scientific paper reporting the result.

"Moreover, its radius should be only 1.5 times the Earth's radius, and models predict that the planet should be either rocky - like our Earth - or covered with oceans."
Xavier Delfosse, a member of the team from Grenoble University, added: "Liquid water is critical to life as we know it."
He believes the planet may now become a very important target for future space missions dedicated to the search for extra-terrestrial life.
These missions will put telescopes in space that can discern the tell-tale light "signatures" that might be associated with biological processes.
The observatories would seek to identify trace atmospheric gases such as methane, and even markers for chlorophyll, the pigment in Earth plants that plays a critical role in photosynthesis.

'Indirect' detection
The exoplanet - as astronomers call planets around a star other than the Sun - is the smallest yet found, and completes a full orbit of its parent star in just 13 days.

Indeed, it is 14 times closer to its star than the Earth is to our Sun.
However, given that the host star is smaller and colder than the Sun - and thus less luminous - the planet nevertheless lies in the "habitable zone", the region around a star where water could be liquid.
Gliese 581 C was identified at the European Southern Observatory (Eso) facility at La Silla in the Atacama Desert.
To make their discovery, researchers used a very sensitive instrument that can measure tiny changes in the velocity of a star as it experiences the gravitational tug of a nearby planet.
Astronomers are stuck with such indirect methods of detection because current telescope technology struggles to image very distant and faint objects - especially when they orbit close to the glare of a star.
The Gliese 581 system has now yielded three planets: the new super-Earth, a 15 Earth-mass planet orbiting even closer to the parent star, and an eight Earth-mass planet that lies further out.

The latest discovery has created tremendous excitement among scientists.
Of the more than 200 exoplanets so far discovered, a great many are Jupiter-like gas giants that experience blazing temperatures because they orbit close to hot stars.
The Gliese 581 super-Earth is in what scientists call the "Goldilocks Zone" where temperatures "are just right" for life to have a chance to exist.

Commenting on the discovery, Alison Boyle, the curator of astronomy at London's Science Museum, said: "Of all the planets we've found around other stars, this is the one that looks as though it might have the right ingredients for life.
"It's 20 light-years away and so we won't be going there anytime soon, but with new kinds of propulsion technology that could change in the future. And obviously we'll be training some powerful telescopes on it to see what we can see," she told BBC News.
"'Is there life anywhere else?' is a fundamental question we all ask."
Professor Glenn White at the Rutherford Appleton Laboratory is helping to develop the European Space Agency's Darwin mission, which will scan the nearby Universe, looking for signs of life on Earth-like planets. He said: "This is an important step in the search for true Earth-like exoplanets.
"As the methods become more and more refined, astronomers are narrowing in on the ultimate goal - the detection of a true Earth-like planet elsewhere.

"Obviously this newly discovered planet and its companions in the Gliese 581 system will become prominent targets for missions like Esa's Darwin and Nasa's Terrestrial planet Finder when they fly in about a decade."