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From: Roger Nelson
To: All
Date: 2017-04-21 22:34:18
Subject: Close Approach Comets

Close Approach Comets
 
Comets are some of the most interesting objects in the solar system. Water
that filled the ancient oceans of Earth might have been delivered by
comets. And there is growing evidence that many comets (as well as some
primitive asteroids) contain molecules key to life. NASA has sent space
probes to travel hundreds of millions of miles to study these icy
interlopers from the outer solar system.
 
https://www.youtube.com/watch?v=j-Vz38ECJh0
 
Comets are balls of frozen gases, rock and dust that orbit the sun. Jets of
gas and dust from comets form long tails that can be seen from Earth when
they fly close enough to our planet.
 
In 2017 and 2018, three comets will pass near the Earth.
 
Their names are 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova,
and 46P/Wirtanen. Astronomers call them "41P", "45P",
and "46P", for short.
 
At closest approach on April 1, 41P was only 56 times farther from Earth
than the Moon. 45P was even closer at 31 lunar distances when it flew by on
February 11. And 46P approaches 30 lunar distances, on December 16, 2018.
 
Kelly Fast, Program Manager in the Near-Earth Object Observations Program
at NASA Headquarters says, "This provides a good opportunity to do
science without having to launch a spacecraft."
 
Telescopes around the world have been trained on the comets as they pass
by, studying their structure and chemical compositions.
 
For the general public, comet 45P was an easy target for small telescopes
when it passed closest to Earth in February, and 41P will be an easy
telescope target through May of 2017. But 46P will be the biggest
attraction. In December 2018, it could be visible to the naked eye from
dark sky sites.
 
Astronomer Tony Farnham of the University of Maryland says, "46P has a
small nucleus, but is known to be a `hyperactive' comet. It is probably
ejecting ice crystals from its surface, producing higher than normal
activity."
 
This hyperactivity may contribute to the naked-eye brightness of 46P. It
also makes the comet somewhat unpredictable with unexpected surges in
activity-and visibility-possible as it passes by.
 
These comets have been so close that amateur astronomers can help study
them, too. Farnham is assisting Nalin Samarasinha at the Planetary Science
Institute in Tuscon, Arizona with the organization of the "4*P Coma
Morphology Campaign" to coordinate the efforts of amateurs worldwide.
 
"Amateur astronomers can help us monitor these comets without
interruption," explains Farnham. "With observers distributed
around the world, we can get much better coverage, with fewer and shorter
breaks."
 
"We can then combine amateur observations with observations from
professional telescopes to study the structures in the comet's
atmosphere-or `coma.' If we use the amateur data in our studies, then they
get to be an author on any papers that result."
 
"A few years back, we used this same type of network for our studies
of comet ISON, and they proved very successful, with data from 23 different
groups around the world."
 
For more about objects in and around Earth's neighborhood, stay tuned to
science.nasa.gov.
 
 
Regards,
 
Roger

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