Astrostatistics

I begin to have a crush on Astrostatistics and Astrophysics since I came to SAMSI. Coincidently it has program on Statistical, Mathematical and Computational Methods for Astronomy (ASTRO) in 2016-2017.  The world towards the universe was first time opened for me during the conversation with some of the scholars (especially Dr. Hyungsuk Tak) in this field I met in SAMSI. 

I officially joined this community in a somehow dramatic way. In JSM2018 in Vancouver this summer, Dr. Jessi Cisewski invited me to their ASA Astrostatistics Interest Group and so luckily I was involved in their annual Business Meeting in JSM (middle picture below. I'm not in the picture as I left earlier to give my presentation).  I met many brilliant people in the meeting and then I determined to be part of this group. Later I also joined Astrostatistics and Astroinformatics Portal (ASAIP) and  International Astrostatistics Association (IAA). Now I'm the event editor of  IAA.

I’m starting to read Feigelson & Babu’s Modern Statistical Methods for Astronomy this Christmas and hope to finish it before Spring break in March, 2019. This book covers the fundamental statistics theories and methodologies in application on Astronomy. It also aims to help astronomers perceive megadatas from celestial objects via modern statistical analysis and interpret cosmic phenomena in advanced statistical language. It is the bible for Astrostatistics! I take notes and record them in my blog  for myself better understanding this fantastic field.


Voyager 2

THE CONTINUING JOURNEY OF VOYAGER 1 & 2     [Source: NASA]

For the second time in history, a human-made object has reached the space between the stars. NASA's Voyager 2 probe now has exited the heliosphere - the protective bubble of particles and magnetic fields created by the Sun.  

Comparing data from different instruments aboard the trailblazing spacecraft, mission scientists determined the probe crossed the outer edge of the heliosphere on Nov. 5, 2018. This boundary, called the heliopause, is where the tenuous, hot solar wind meets the cold, dense interstellar medium. Its twin, Voyager 1, crossed this boundary in 2012, but Voyager 2 carries a working instrument that will provide first-of-its-kind observations of the nature of this gateway into interstellar space.    

Voyager 2 launched in 1977, 16 days before Voyager 1, and both have traveled well beyond their original destinations. The spacecraft were built to last five years and conduct close-up studies of Jupiter and Saturn. However, as the mission continued, additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible. As the spacecraft flew across the solar system, remote-control reprogramming was used to endow the Voyagers with greater capabilities than they possessed when they left Earth. Their two-planet mission became a four-planet mission. Their five-year lifespans have stretched to 41 years, making Voyager 2 NASA's longest running mission.

[Source: NASA/JPL-Caltech]

At the end of 2018, the cosmic ray subsystem aboard NASA's Voyager 2 spacecraft provided evidence that Voyager 2 had left the heliosphere. There were steep drops in the rate of heliospheric particles that hit the instrument's radiation detector, and significant increases in the rate of cosmic rays. 

While the probes have left the heliosphere, Voyager 1 and Voyager 2 have not yet left the solar system, and won't be leaving anytime soon. The boundary of the solar system is considered to be beyond the outer edge of the Oort Cloud, a collection of small objects that are still under the influence of the Sun's gravity. The width of the Oort Cloud is not known precisely, but it is estimated to begin at about 1,000 astronomical units (AU) from the Sun and to extend to about 100,000 AU. One AU is the distance from the Sun to Earth. It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.

[Source: NASA/JPL-Caltech]

An annotated illustration of the interstellar medium     [Source: Charles Carter/Keck Institute for Space Studies]

 


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