Internet version [Naruhodo no Mori] Vol.46

by Yumiko Mori

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Vol. 46     July, 15th, 1999

Orihime and Hikoboshi stars

Home science experiments for mothers of elementary school children

Mom: "Look!  That blue-whitish star is Orihime star, which is also called Vega. The star belongs to Lyra constellation.
Nao's Mom: "Is that right? Then can you tell me where is Hikoboshi star?"
Tae's Mom: "Well, that star is located at lower right from Vega, but we can not see it because of clouds."
Nao's Mom: "That's disappointing!"

Nao's Mom: "Is it true Orihime and Hikoboshi meet once a year?"
Tae's Mom: "No, it doesn't happen. That happens only in that famous story."

In Japan we celebrate a holiday called 'Tanabata'. A romantic mythical story about Orihime and Hikoboshi is associated with this holiday. See http://www.coara.or.jp/~mieko/hoshi.htm for more detail.

Tae's Mom: "Look! That star is Deneb and belongs to Cygnus constellation. Because the constellation stars form a cross shape, they are also called the Northern Cross.
Deneb, Vega, and Altair form a big triangle in summer night. If we are far away from city lights, we would be able to see the Milky Way between Vega and Altair."
Nao's Mom: "I wish I could see it."
Tae's Mom: "Me too. How about going a trip to the countryside in this summer?"
Nao's Mom: "We can enjoy more if we know names of various stars and constellations."
Tae's Mom: "That's true."
Nao's Mom: "How do you know so many star names?"
Tae's Mom: "Well, I did a bit cheating. Just before coming here, I looked up the book."

Materials

A book on summer constellations or a star chart

A compass

Look at the Summer Triangle

1. Look toward the eastern sky at 9 pm on July 15th.
   (These date and time are meant to be for locations within Japan. Please find out yourself when is the best time to look at these stars on your location.)
   The best place to see stars is away from city lights.
   Find the brightest star with blue-whitish color in the eastern sky. That star is Vega.

2. Move right and lower direction from Vega. There you find Altair.

3. In the opposite side of Vega, you should be able to find Deneb. By connecting these three stars you can get a big triangle shape in the eastern sky.

Date and time when the summer triangle looks as shown. (These date and time are meant to be for locations within Japan.)

July 15th 9 PM

* At 11 PM the triangle rotates 30 degree from the east toward the zenith.

* One month later the triangle rotates 30 degree from the east toward the zenith.

• Your eyes eventually adapt to dark night sky. Children need several minutes, while adults need about 10 minutes to adapt.

• Orihime and Hikoboshi are 14 light years apart. It is impossible for them to meet within one day.

   In the Tanabata story, Orihime and Hikoboshi are allowed to meet only once a year. But even after Tanabata, you can still see Orihime and Hikoboshi stars. You will have no problem in finding these bright stars. Bring friends and show them where Orihime and Hikoboshi are located. You'll be able to impress your friends how knowledgeable you are. Since I learned the name of one star, I started to like to stare starry night sky. Why don't you enjoy watching stars?

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