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WhatWWhatWhhaatt areaarearree CosmicCCosmicCoossmmiicc Rays?!RRays?!Raayyss??!!

By Hayanon Translated by Y. Noda and Y. Kamide Supervised by Y. Muraki ᵶᵶᵋᵰᵿᶗᶑᵘᴾᴾᵱᶇᶀᶊᶇᶌᶅᶑᴾᶍᶄᴾᵡᶍᶑᶋᶇᶁᴾᵰᵿᶗᶑᵋᵰᵿᶗᶑᵘᵘᴾᴾᵱᶇᶀᶊᶊᶇᶌᶅᶑᴾᶍᶄᴾᵡᶍᶑᶋᶇᶁᴾᵰᵿᶗᶑ

Have you ever had an X-ray examination Scientists identified three types at the hospital? In 1896, a German of : positively-charged alpha physicist, W. C. Röntgen, astonished people particles, negatively-charged beta particles, with an image of bones captured through and uncharged gamma rays. In 1903, M. the use of X-rays. He had just discovered Curie along with her husband, P. Curie, and the new type of rays emitted by a discharge Becquerel, won the Nobel prize in physics. device. He named them X-rays. Because Furthermore, M. Curie was awarded the of their high penetration ability, they are Nobel prize in chemistry in 1911. able to pass through flesh. Soon after, it Certain types of radiation including was found that excessive use of X-rays can X-rays are now used for many medical cause harm to bodies. purposes including examining inside the In that same year, a French scientist, body, treating , and more. Radiation, A. H. Becquerel, found that a uranium however, could be harmful unless the compound also gave off mysterious rays. amount of radiation exposure is strictly To his surprise, they could penetrate controlled. wrapping paper and a photographic The work with radium by M. Curie later film generating an image of the uranium led to the breakthrough discovery of compound. The uranium rays had similar the radiation coming from . These characteristics as those of X-rays, but were cosmic rays were discovered by an Austrian determined to be different from them. physicist, V. F. Hess. Although cosmic The emission of rays was also found rays have high-penetration ability, they in thorium by G. C. Schmidt in Germany do not affect because the ‛s and M. Curie in France in 1898. The term makes them harmless. “radioactivity” was given to this mysterious Outside the atmosphere, however, phenomenon. M. Curie made the spectacular cosmic rays become a threat to ! discovery of radium. Radium began to be They have to be protected from the used for radiation research because of its harmful effects. intense radiation. It was found to be a Now, what are cosmic rays? In this few tens of thousands times stronger than booklet, you will find the answer with the uranium. help of your friends Mol and Mirubo.

ᲶSources: , Earth - NASA; Crab Nebula - Hale ; Jets from , Active Galactic Nucleus - National Radio ; Remnant - ISAS/JAXAᲸ TinyTiny mysteriousmysterious particlesparticles aarere comingcoming allall thethe wayway tthroughhrough spacespace toto EEarth.arth.

TheyThey areare cosmiccosmic rayrays!s!

Hooray, What are you I got it! looking at, Mirubo? Robotic dog, Mirubo. Cosmic rays!

Mol, science- loving girl.

1 Cosmic rays?? No way! I am a That sounds exciting! beginning space Are we going to pilot. Space this travel is a little time? too advanced.

rrr whiwhirrrrrrr

I am glad you asked. OK, then A particle is very tiny. what are It is 1 trillionth of cosmic rays? 1 millimeter.

he-h They are too small to e- be visible to mere hhe- Oh, he is e- eyes, Mol. hhe- making fun Of course I can see e- of me again! he with my super- he duper eyes.

giggle

That's not Here come How fair, Mirubo!! frustrating! cosmic rays! And here I too want too. to see cosmic hum rays. clap! hum ! sh yoicks! a Gn Now, I will go to ask Sensei.

2 Sensei, I need your You want to help! see cosmic rays? Yes, by all means.

The cosmic ray Let‛s try an experiment particles are with a cloud chamber. even smaller It can be a cosmic A cloud than viruses ... with our ray detector. chamber??? and cannot naked eyes, but be seen ... I have an idea. nk- cli clank

The materials needed are , dry ice, a beaker, absorbent cotton, and plastic wrap.

Wowie! Plastic Wrap I knew you could do it.

First, soak the absorbent cotton with ethanol and place it over the mouth of the beaker. Cover the top with plastic wrap and ...... tightly seal using a rubber band. Place the beaker on the dry ice to cool it down. CAUTION: Dry ice must be handled with care. Do not touch it directly. 3 Darken the room and shine a flashlight on the vapor cloud in the Wow! beaker. Observe the cloud carefully, then There is you will see ... a flash!!

sparks Ummmm park ...?

Yipes! That was the track What made of a cosmic ray, which passed through that flash?! the beaker.

o- Creation of a cloud Whoopee! woo-wo chamber was the original I saw a hoohoo idea of a Scottish cosmic ray ... physicist C. T. R. Wilson, who was awarded the Nobel Prize in 1927. I mean its track. The design is simple and well- v signs! constructed.

4 As many as 140 What are cosmic cosmic ray particles Ugh, is rays all about? fall onto your desk that true?! per second. I can see clearly.

There are two types of cosmic rays: solar cosmic rays and galactic cosmic rays.

Solar cosmic rays come to Earth a few hours after being formed. On the other hand, galactic cosmic rays are formed in the area of a supernova ...

... and travel for more than 10 million years to reach Earth.

They hit the Earth at nearly the .

5 I know! We can see more tracks of cosmic rays if we try the experiment outside, can‛t we?

It does not make a difference. They pass through Oops, is Cosmic rays get ground, cement, and that so?! into a building. I haven‛t even our bodies. noticed it.

You have kshould that ! now n

I remember that No need to worry. They are not harmful cosmic rays are to as long as we radiation. are on Earth.

Really?! What a relief.

Don‛t scare me.

6 What do cosmic Primary cosmic rays consist of? rays, the cosmic What particles rays coming from outer space, are do they have? P mostly .

primary cosmic rays They collide with the Earth‛s atmosphere and pion decay into secondary gamma cosmic rays. ray secondary cosmic rays

muon

I have got it! Cosmic rays on the Earth‛s are tiny particles produced by energetic protons.

7 Let‛s take a familiar Exactly. They are tiny example, a fluorescent but have exceedingly How high light commonly seen at high energy! is that? school and home, ...... to compare its energy to that of cosmic ray particles.

Inside a fluorescent tube, atoms in a high-energy state The energy is return to the ground state equal to 2 by emitting the extra energy electron volts in the form of light. (eV).

Now, an individual cosmic ray particle has ... the energy of... 1 billion eV!!!

Aiiieee!! Wait! I have never heard Why doesn‛t If we were of these anyone care hit by those dangerous about them? particles, ... particles.

... we would ! get a huge shock!

8 Cosmic rays do have high energy, but their number is small. Considering the size of Earth, the cosmic ray particles reaching Earth are too few to affect us.

It is just like thinking Then, cosmic rays are only one raindrop really powerless! could solve the I expected that they You are shortage. could do something with their energy! right, Mol. Oh, I see... This is surely huff teeny-weeny.

They come all They can be the way here ignored. They and are not are uninvited useful at all? guests to our Earth!

That‛s not fun!

9 Do not jump to Huh, how could conclusions. they be?! They are helpful in many ways.

By taking Muons in cosmic advantage of their rays can penetrate , we are about 1 km into able to research rocks. ...

... the inside of the Egyptian pyramids and the status of volcanic magma.

Cosmic rays also enable us to study below the surface of and the to search for water!

That is amazing! I have never thought of such ideas.

10 I hope cosmic That sounds like we rays will be used are going to decode for many more messages sent from purposes in the outer space. future ...

... along with Messages from progress in space ... cosmic ray That is exciting! research itself.

stoked! zingz I am surely going to in catch and embrace cosmic rays. g You are messengers from the ! zingzing zingzing

Ah, if only you could, Mol. They are passing through your body.

11 ⁉⁚⁓⁦‒⁓⁤⁗‒‵⁡⁥ ⁛⁕‒⁄⁓⁥‱–

I am excited to learn about cosmic Harrumph! I am well-designed. rays. First of all, how high is the energy of cosmic rays? You are lucky, Mirubo. Sensei, would you tell me how they can search The energy of cosmic rays is over for water on Mars and the Moon 1,000 times higher than that of other through cosmic rays? types of natural background radiation. Sometimes it becomes 10 trillion times Cosmic rays can penetrate 40 cm higher for ultra-high-energy cosmic deep into the surface of Mars and rays. the Moon, and reach ice that may be lying beneath the . Cosmic rays Wow, what gives them such high would be reflected by nuclei, energy? just like billiard balls. We then have to measure the reflected rays via Good question, Mol. Cosmic rays . obtain energy through repeated When the rays that are reflected collisions with other particles. by hydrogen increase, we are able to pinpoint an area which could have Where do they come from? water.

The Sun, distant , and How about ? Water (H2O) distant outside ours are their is made up of oxygen (O) and hydrogen birthplaces. (H2). How do you know that there is Cosmic rays are produced in solar oxygen? flares and from explosions. That is a good question. To prove Are they visible? How about color, the presence of water, for example, shape, and smell? drilling should be conducted at the lunar pole where the level of the I can see them, but do not know reflected cosmic rays is high. the color and smell. At least they carry no savory aroma of roasted meat. Does the Earth emit cosmic rays like the Sun does? Could I find the Cosmic rays are very small answer if I went to the Moon? particles and cannot be seen even with a microscope. They have no color or Radiation from rocks on the Earth smell. There is a device called a cloud is so weak that it is absorbed in the chamber to make cosmic rays visible! atmosphere. They are coming from space Meanwhile, low-energy gamma at nearly the speed of light and rays and X-rays emitted from showering onto Earth. and thunderstorms could be measured from the Moon because they are Do they hit the Moon and Mars, released high in the thin atmosphere. too? Their energy is too low to be called cosmic rays, and could be named Definitely. Mars has a thin “Earth rays,” instead. atmosphere, and so it is believed that only half as many cosmic rays reach Earth rays?! How nice!! Mars as compared to the Moon. Cosmic rays are a great threat I will try to make my to humans travelling in space, but I more powerful so I can go to the Moon believe it is not for you, Mirubo. and see “Earth rays” with my own eyes!!

12 6JG*KIJGT9G)QVJG/QTG9G.GCTP6JG*KIJGT9G)QVJG/QTG9G.GCTP

Measurements of cosmic rays are difficult it is for humans to be in this thin usually made on high mountains. Do you air. know why? It is because the Earth is However, thin air becomes surrounded by an atmosphere. advantageous for observing cosmic rays, A French scientist B. made because they collide in the atmosphere important discoveries about air . and are absorbed. A change of 200 g/cm2 The unit for , in atmospheric weight changes the hectopascal, came from his name. One concentration of cosmic radiation as much hectopascal is equal to 100 pascal. You as 10 times. In other words, comparing an may have heard a weather forecaster on observatory on Mt. Chacaltaya with the TV saying that the typhoon‛s atmospheric one on Mt. Norikura, observational pressure is, say, 910 hectopascal. That is equipment at the former could be 10 a very strong typhoon. The atmospheric times smaller than that at the latter. pressure at the center of the typhoon is Furthermore, the former is able to obtain 10% lower than the normal pressure. more accurate data when the same Atmospheric pressure becomes even equipment is used. lower at the top of high mountains. For Do you understand why the higher we example, our Solar Neutron Telescope on go, the more we are able to learn about Mt. Norikura is located at 2,770 meters cosmic rays? above sea level, where the air pressure becomes 25% lower than that at sea level. On the top of Mt. Fuji, it lowers to 60%. The Chacaltaya Observatory in Bolivia is located at 5,250 meters above sea level. The air there is half as thick as at sea level. If you have ever seen a video of mountain climbers attempting to climb Mt. Everest, you can easily imagine how

Solar Neutron Telescope on Mt. Norikura.

Chacaltaya Observatory ᲶCourtesy of the -Japan Emulsion Chamber Group, Chacaltaya ObservatoryᲸ CAWSCAWSESES:A: A SCOSCOCOST EP Pro Programm20 20200404-202008 Climate and Weather of the Sun-Earth System (CAWSES) Solar Influence on Climate CAWSES is an international program sponsored by SCOSTEP (Scientific Committee on Solar-Terrestrial Physics) and has been established with the aim of significantly : Science and enhancing our understanding of the and Applications its impacts on life and society. The main functions of CAWSES are to help coordinate international activities in Atmospheric Coupling Processes observations, modeling and theory crucial to achieving this understanding, to involve scientists in both developed and developing countries, and to provide educational opportunities for students at all levels. The CAWSES office is located at Space Climatology Boston University, Boston, MA, USA. The four science Themes of CAWSES are shown in the figure. http://www.bu.edu/cawses/ http://www.ngdc.noaa.gov/stp/SCOSTEP/scostep.html

Solar-Terrestrial Environment Laboratory (STEL), Nagoya University STEL is operated under an inter-university cooperative system in Japan. Its purpose is to promote “research on the structure and dynamics of the solar-terrestrial system,” in collaboration with a number of universities and institutions both in Japan and abroad. The Laboratory consists of four research Divisions: Atmospheric Environment, Ionospheric and Magnetospheric Environment, Heliospheric Environment, and Integrated Studies. The Geospace Research Center is also affiliated to the Laboratory to coordinate and promote joint research projects. At its seven Observatories/Stations, ground-based observations of various physical and chemical entities are conducted nationwide. http://www.stelab.nagoya-u.ac.jp/

ƸǍƷǜHayanon Kodomo no Kagaku (Science Graduated from the Department of Physics of for Kids) Ryukyu University, Hayanon, a writer and Kodomo no Kagaku, published by the cartoonist, has contributed a number of serials Seibundo Shinkosha Publishing Co., Ltd. is a in popular magazines on the basis of her strong monthly magazine for juniors. Since the background in science and computer games. inaugural issue in 1924, the magazine has Her consistent writing style, expressing a love continuously promoted science education by for science, is well accepted. providing various facets of science, from http://www.hayanon.jp/ scientific phenomena in everyday life to cutting edge research topics. ޓ http://www.seibundo.net/

“What are Cosmic Rays?!” is published with cooperation of “Kodomo no Kagaku.” Mol, Mirubo, and Sensei thank Lisa Kihn and Joe Allen for their help in preparing the English version of our story.

Produced by the Solar-Terrestrial Environment Laboratory, Nagoya University and the Scientific Committee on Solar-Terrestrial Physics in conjunction with the CAWSES program. July 2006 All rights reserved.