- 2107 -
Planets outside our own. - There are 300,000,000,000 stars in our
galaxy. There are
2 trillion galaxies in the Observable Universe. So, that is 200,000,000,000,000,000.
( 2 * 10^17 stars). Half of these stars have at least one planet.
-
-
-
------------------ 2107
- Planets
outside our own
-
- Our Solar
System has 8 planets. When I was in high
school we had 9 planets. Pluto got
demoted to a dwarf planet. This happened
because astronomers discovered planet size asteroids larger than Pluto further
from the Sun. These outliers were named
dwarf planets so Pluto had to be included.
In fact the largest asteroid orbiting between Mars and Jupiter named
Ceres also became a dwarf planet.
-
- We no sooner
got our own solar system redefined when we discovered other solar systems
outside our own. The first was a pulsar
discovered in 1992. This rotating
neutron star crested a beam of radiation that swept across Earth like a light
house beam. The radio frequency of the
beam shifted in wavelength in a cycle of repeating period. The conclusion was that a planet , or
planets, were orbiting this star causing it to wobble back and forth as the
planet circles.
-
- Our Sun does
the same thing as our planets orbit it.
The biggest contributor being massive Jupiter.
-
- Then in 1995
a planet , or planets, were discovered orbiting a star called 51Pegasi. This was a normal, main sequence star similar
to our Sun. This planet was half the
mass of Jupiter and completed each orbit in 4 days.
-
- Over the next
decade thousands of exoplanets, as they are called, have been discovered. The discoveries used two methods to confirm
the star had orbiting planets. The first
was the "radial velocity method".
This uses the Doppler shift in frequency of light as the star's motion repeated
back and forth as it was pulled by the
orbiting planet. The planets are
invisible to our telescopes, but, their presence is learned by their effect on
their host star.
-
- In 1999 the
second method of planet discovery used the detectable slight dip in the star's
light as the planet passed in front of the star, called the "transit method". This method only works when the plane of
orbit lines up with Earth's line of sight.
-
- To date,
2018, there have been thousands of discoveries and 1,284 of these have been "confirmed"
as orbiting planets. Confirmation requires
multiple measurements of multiple orbits before astronomers can say for sure
that is a planet.
-
- Beginning in
1999 the detection of the first spectrum of light passing through the planet's atmosphere
became possible. This allowed elements
to be identified, sodium being the first element found. Scores of exoplanets have had spectra of
their atmospheres analyzed. Brightness
and size and atmosphere compositions have allowed astronomers to select those targets that are most earthlike.
-
- In 2009 the Kepler Space Telescope was launched to
add to the exoplanet study. Kepler's
telescope stared at tens of thousands of stars all at once, watching for transits that dimmed
their starlight as the planet passed in its orbit. Thousands of these planet candidates were
discovered. Long term studies are needed
for each candidate are required before a confirmations can be made.
-
- Planet
temperatures are measured. Their mass calculated. Chemical compositions are measured. All to better understand how solar systems
come to be and how they evolve. We now
know that tiny planets around small stars are common place.
-
- Back to our
closest star, Proxima Centura, seven temperate, rocky planets have been
identified and three of these are in the habitable zone of orbits. The total number of diverse planets is
confounding, and amazing, generating much more to learn.
-
- OTHER REVIEWS
AVAILABLE TO LEARN ABOUT
EXOPLANETS:
-
- 2064
- Of the 3,700 exoplanets
discovered 17 are earth masses about the size of Neptune. We can determine the planet's mass using the
Doppler effect on the planet's star.
Planets can receive their water from comets and asteroids over their
lifetimes in habitable zones. Water rich
planets and moons are frequent in other planetary systems.
-
- 2043 - Evidence
is that planetary systems are highly chaotic.
The chaos erases all the evidence of how they were formed. As the technology and techniques improve more
and smaller planets will be discovered.
Astronomically speaking there is total diversity in the universe.
-
- 2036. - Is
there life on other planets? Studying
150,000 stars astronomers
have found over 4,000 exoplanets.
-
- 2030.
- New data on Cepheid Variable stars in
our Milky Way Galaxy find them 10 times further away. New calculations for an expanding universe
are that the expansion rate is 50,000 miles per hour for every lightyears
distance.
-
- The Hubble Constant is a measurement of how fast the
Universe is expanding. For every star there is a 50% chance there is at least
one planet orbiting it. If we discover a planet with a large amount of oxygen
in its atmosphere there must be living organisms living there.
- 1912.
- Our nearest star system ,
Proxima Centura , has at least 2 planets in orbit. One in the habitable zone,
Exoplanet Proxima b. It is only 25 trillion miles away. The star Proxima has at
least one planet in orbit that could likely have liquid water on its surface.
-
- 1874 -
Exoplanets have moons and they may even be more habitable? 4,000 planets discovered so far but who knows
how many moons? Jupiter’s has 67 moons
and two of them could support life because liquid water is below their surface.
-
This same Review has an appendix listing
five more reviews about Europa, three reviews about Enceladus, and five reviews
about Titan.
-
- 1833.
- Exoplanets are starting to review
their secrets.
-
- 1669. - How many
planets are there? How we do the math to
determine the mass of each planet.
-
-
There are 300,000,000,000 stars in our galaxy.
-
There are 2 trillion galaxies in the Observable Universe.
-
So, that is 200,000,000,000,000,000.
( 2 * 10^17 stars )
-
Half of these stars have at least one planet.
-
-
Think about it!
-
- September 28,
2018
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--------------------- Friday, September 28,
2018 -------------------------
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