universe solar system

1. TP 1: The Earth, the Universe, the Solar System
Abilities and attitudes
1. Identify the expressions in the text by highlighting them: star, solar system,
planet, galaxy.
Then give a definition and example of each.
2. To express astronomical distances, we use a unit of length: the light year. It
measures the distance L traveled by light at a speed c of 300,000 km/s for 1 year
(t).
Ccalculate the number of km corresponding to 1 light year
3. What question did scientists likely ask themselves when they discovered
exoplanets like Gliese 581 c?
4. Propose an approach that would guide research.
understand a text; extract useful
information;
communicate in appropriate scientific
language
regain knowledge (physics and
mathematics)
Practice a scientific approach
NASA would have discovered another planet Earth teeming with life
It's now official. The Earth is not the only habitable planet in the universe, its 'cousin' Kepler-452b has a sun identical to ours and is in orbit
around its star at the same distance as the Earth from the his.
In all civilizations, Man has always been
intrigued both by his own origin and that of life:
is life a universal phenomenon or is it unique on
Earth?
The idea that intelligent life can exist elsewhere
than on Earth is not new: it goes back to the
Ionian philosopher *, Anaximander of Miletus,
who affirmed the plurality of inhabited worlds.
(* school of philosophy which undertook a vast
investigation into nature in the 6th and 7th
centuries BC)
We thought since the 1980s that we were alone
around the Sun and that Earth was most likely
the only place in the solar system that harbors
life...
But the sun is not the only star in the Milky
Way...
The closest star to the Sun is 4 light years away
and the Milky Way is not the only galaxy in the
Universe (the closest is more than 5 billion light
years away.)
Are the other stars in our galaxy surrounded by
planets, do other inhabited lands exist?
The scientific progress necessary to gather
information on this subject is being
accomplished before our eyes...
Using the HARPES spectrograph on ESO's 3-6-
m telescope, astronomers discovered in 2007 the
most Earth-like planet outside our Solar System
to date, an exoplanet with a radius of only 50 %
larger than Earth. This exoplanet orbits the red
dwarf Gliese 581, a star located 20.5 light years
away in the constellation Libra.
L = c .t

2. Everything seems to go in the direction that this new Earth is (or was, unfortunately,) crowded with life, the next step will be to detect artificial signals coming
from this world. The fact is that this exoplanet's sun is 1.5 billion years older than ours and the planet's oceans can potentially evaporate into space. This same
fate will be reserved for the Earth in several billion years.
The fact is that it was the first habitable planet similar to Earth that was discovered.
Eureka!”, Archimedes would have shouted, if he were part of the team of astronomers who have just taken a crucial step in the quest for a “habitable” twin Earth.
These scientists, led by a NASA astronomer and whose work was published this Thursday in the American journal “Science”, discovered thanks to the American
Kepler space telescope the first planet of a size comparable to Earth and on which the Water could exist in a liquid state, making life possible. If it is ruled out for
humans to “live” there one day – this exoplanet is still located 4.6 million billion kilometers from our Sun – this discovery reinforces the probability of finding sister
planets of the Earth in our galaxy, the Milky Way.
“What makes this discovery particularly interesting is the fact that this planet called Kepler-186f is of Earth size in orbit around a so-called dwarf star, smaller and
cooler than the sun, in the temperate zone where the water can be liquid,” says Elisa Quintana, an astronomer from the SETI Institute at NASA’s Ames Research
Center, who led this research. “This is the first Earth-sized exoplanet found in the habitable zone of another star,” she insists.
The “habitable” zone
Kepler-186f is located in a star system 490 light years from the Sun (one light year is 9.46 trillion kilometers) with five planets orbiting a “sun”. But while its four
“sisters” are too close to this sun, only Kepler-186f is in the so-called habitable zone, the one where life as we know it and which depends on the presence of
water, has the greatest probability to develop there. It orbits its star in 130 days and receives a third of the light energy that Earth gets from the sun.
Being in the habitable zone, however, is not enough to accommodate life. Of the nearly 1,800 exoplanets detected over the last 20 years, around twenty are
orbiting their star in the habitable zone. But these planets are significantly larger than Earth and therefore it is difficult, given their size, to determine whether they
are gaseous or rocky.
The perfect size?
The planet Kepler-186f has a radius 1.1 times that of Earth. According to theoretical models of planetary formation, planets with a radius less than 1.5 times that
of Earth are unlikely to accumulate a thick atmosphere like the giant gas planets of our solar system. Kepler -186f thus enters the category of rocky planets in our
solar system such as Earth, Mars or Venus.
“Given the small size of this exoplanet, there is a high probability that it is rocky and has an atmosphere. If this atmosphere offers good conditions, water can exist
in a liquid state on the surface,” explains Emeline Bolmont, a researcher at the University of Bordeaux who participated in this advance. She emphasizes that these

3. conclusions are based on extrapolations because “to be sure that it is rocky we would need to have the mass of the planet which is not possible with current
instruments”.
An “important step” in the quest for a second land
For Fred Adams, professor of physics and astronomy at the University of Michigan, “this is an important step in the quest to discover an exoplanet identical to
Earth.” In other words, the objective of the Kepler mission.
“Future NASA missions such as the James Webb space telescope (which will succeed Hubble in 2018 and will be more powerful, editor’s note), will be able to
discover the closest rocky exoplanets and determine their composition as well as the nature of their atmosphere,” he said. said Paul Hertz, director of the space
agency's astrophysics division, during a press conference.
At the end of 2013, astronomers estimated that billions of Earth-sized planets orbiting stars similar to the Sun in our galaxy would be potentially habitable. The
researchers based themselves on data from the first three years of observation by Kepler launched in 2009 to examine more than 100,000 stars resembling our
Sun located in the constellations Cygnus and Lyra.