-
2064 - How was our Solar System created? It all started with
a cloud of dust and gas coalescing around the Sun some 5 billion years
ago. After the rocky planets formed
there was a 300 million year bombardment of asteroids that brought water back
to Earth. Of the 3,700 exoplanets
discovered so far most are more than 17 Earth masses, about the size of
Neptune. Most are gas planets that
orbit close to their stars. But, some are
in life's habitable zone.
-
-
-
----------------------------- 2064 -
Exoplanets, is there life out there?
-
- On , April 16, 2018, the Transiting Exoplanet
Survey Satellite (TESS), was launched
from Cape Canaveral. NASA's new exoplanet hunter will train its sights on
nearer, brighter stars than its predecessors did. If TESS lives up to
scientists' predictions, it could energize our search for life in the cosmos.
-
- When the Kepler Space Telescope launched in
2009, scientists didn't know what fraction of stars hosted planets. Kepler is
what made us become aware that planets are as common as telephone poles. But, the stars that Kepler was staring at for
four years were all somewhere between 500 and 1,500 light-years away. TESS will survey the local neighborhood for
planets similar to Earth.
-
- TESS is designed to find planets orbiting
nearby stars spread across the sky. The satellite is not specifically intended to
look for planets that can support life, but it can find planets orbiting in the
habitable zone of smaller stars.
-
- TESS will find signals of planet candidates. A lot of follow-up work will go into determining
whether these candidates are truly planets, rather than binary stars, artifacts
in the data or something else.
-
- The amount of starlight a planet blocks tells
astronomers the planet's size, while the frequency with which the planet passes
in front of its star indicates the planet's orbital period. Scientists can determine the planet's mass by
using the Doppler effect to measure the wobble the planet induces on its star.
And mass divided by size equals density, so astronomers can determine whether they're
looking at a puffy ball of gas or a solid chunk of rock, or something in
between.
-
-
These new planet discoveries will be
close enough for other telescopes to peer inside the planets' atmospheres. When
a planet transits its star, some of the starlight passes through the planet's
atmosphere before reaching Earth. Different gases absorb different wavelengths
of light, and scientists can determine the composition of the planet's
atmosphere by analyzing the spectrum of this light using these more-powerful
observatories.
-
- Astronomers will be studying the starlight
that filters through exoplanet atmospheres, searching for signatures of
molecules that may be signs of life. Signatures
of life are byproducts that organisms might emit into the atmosphere. They will be looking for water vapor because
all life, as we know it, needs liquid water. And water vapor is a sign of
surface water.
After
water, oxygen would be fantastic. Oxygen is our best biosignature gas on Earth
-
- Many products of biology can also come from
geology, though. For instance, if scientists see methane alongside many other
hydrogen-rich gases, the source is likely not biological. However, finding
methane together with oxygen would be promising, because these gases would
react with each other and become something else if they weren't being
continually produced.
-
- The search for intelligent life is guided by
the Drake equation, a formula devised by astronomer Frank Drake to estimate the
likelihood of receiving signals from intelligent civilizations. The terms of
the equation begin with the number of stars in our galaxy and proceed to the
number of civilizations actively broadcasting their presence into space. Kepler
mostly firmed up the fraction of stars that have planets. The TESS mission will
enrich our understanding of how many planets could support life, and even the
fraction of those planets where life may actually occur , constraining the
equation further.
-
- Kepler
discovered over 3,700 planets in that small area of the sky. One discovery was TRAPPIST -1 star that had 7
planets , 5 orbiting in the habitable zone.
All 5 were mostly rock and some could be 5% liquid water. The Earth is only 0.02% water by mass.
-
-
This determination was made using the transit method where the light of
the host star dims as the planet orbits
passes between us and the star. The
planets were named TRAPPIST-1 a,b,c,d,e,... based on their orbit out from the
star.
-
-
TRAPPIST-1b and 1c are the two inner most planets and are likely rocky
cores surrounded by atmospheres much thicker than Earth's.
-
-
TRAPPIST - 1d is the lightest of the planets 30% the mass of the
Earth.
-
-
TRAPPIST -1e is the only planet in the system slightly denser than
Earth. It may have a denser iron
core. It does seem to have a thick
atmosphere, ocean, or ice layer. It is
mush rockier than the other planets and the most similar to Earth in size,
density, and the amount of radiation it receives from its star.
-
- TRAPPIST
1f and 1g and 1h might have frozen
surfaces. The liquid water may be 125
miles deep with 1,400 miles of ice below that.
That would be water halfway to the planet's center. They may have thin atmospheres but it is
unlikely to contain carbon dioxide.
-
-
The TRAPPIST - 1 system will be studied for a long time. These planets may be deemed habitable but
there is still much to learn about water, habitability and life on these strange
new worlds.
-
-
Water is the key. And, we are not
even sure of how Earth got it's water.
During the early solar system formation it is certain all the water for
the inner planets was evaporated away.
They were too hot to hold water.
So, the theory comes that much later comets, those rocky snowballs ,
delivered water as they came crashing into the inner planetary orbits. However, all the comets that we have been
able to analyze reveal a water fingerprint that is not the same a Earth's
water.
-
-
OK, maybe asteroids delivered the water?
In the asteroid belt the water is locked up in other minerals. Turns out that asteroids have enough water in
them to do the job in filling Earth's oceans.
Seems ridicules but we do not known 75% of Earth's composition even when
are standing on top of it. Theories are
a path to knowledge; they are not
knowledge by themselves.
-
-
Studying White dwarf stars might bring us the answers. These burnt out stars have pristine
atmospheres of hydrogen and helium. So,
if we detect nitrogen or carbon in the atmosphere we know something is falling
in to the star. Probing the outer layers
of White Dwarf stars reveals the guts of their latest meals, consumed in the
last 10,000 to 100,000 years earlier.
After 10 years of study water is found to be the most common ingredient
in the last meals of White Dwarfs. So,
might that not be the same for planets?
-
-
Water rich planets are frequent in other planetary systems. Even in our solar system water still exists
in the shadowed craters of Mercury. In
the oceans deep inside the moons of Saturn and Jupiter, and beneath the icy
surface of Pluto water is there.
-
-
Plants around stars received their water from comets or asteroids and
hold on to that water over their lifetimes.
If planets form in a habitable zone water will come. And, will life follow? God only knows. If it happened here it can happen elsewhere.
Maybe?
-
- May
4, 2018
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to
whomever is interested. ----
---
Some reviews are at:
--------------
http://jdetrick.blogspot.com -----
--
email feedback, corrections, request for copies or Index of all reviews
------------------------- Friday, May 4, 2018
--------------------------------
-----------------------------------------------------------------------------------------
No comments:
Post a Comment