Guidance of the Milky Way watching
1. BackgroundStars don't exist alone. They are gravitationally bound, then make a massive group. We call such a massive
group of stars a "galaxy". A typical galaxy consists of about 200 billion stars. The Sun of our Solar System is one ofstars in the galaxy. For distinguishing from other galaxies, the galaxy in which we are is called "the Milky Way galaxy"or just "the Milky Way" or “Our Galaxy”. Historically, galaxies have been categorized according to their apparent
shape. The Milky Way galaxy is a typical Spiral galaxy, which is disk-shaped assemblages with dusty, curving arms. Thediameter of disk of the Milky Way galaxy is about 10 thousand (10,000) light-years (1 light-year is the distance that thelight travels in a vacuum in one year, equal to about 9.5 trillion kilometers).
The Solar System is located at a distance of about 28,000 light-years awayfrom the center of disk of the Milky Way galaxy. Beautiful Milky Way in thesky as shown in a below picture is a ﬁgure of the Milky Way galaxy with aedge on view (namely seeing the Milky Way galaxy from the side viewingangle).
Solar System↑

face onedge onSolar System

Summerin the
Northern
Hemisphere

Winter intheNorthern
Hemisphere
Images provided by
the National Astronomical Observatory of Japan

There are few stars.
Stars locate in the disk of our galaxy.
You can see many stars in this direction.
There are few stars.

Sun

Summer Earthin the
Northern
Hemisphere

Earth Winter intheNorthernHemisphere

At the beginning of 17th century, a telescope was developed in the Netherlands. An Italian astronomer Galileo
Galilei who understood telescope's structure made a telescope by himself, then observed the night sky with thetelescope. He found the facts: the Moon's surface is rugged, 4 satellites are revolving around Jupiter. He also found thatMilky Way is a place that stars concentrated.
In 19th century, we ﬁnally found the fact that we are in the Milky Way galaxy and that the Milky Way in the sky
is a ﬁgure seeing the disk of our Galaxy from the side way.

2. Purpose
The aim of this activity is, through observation of the Milky Way with a telescope, to notice the fact that theMilky Way is a place that stars concentrated. In addition, pay attention to the shape of the Milky Way, then imagine
that we are in the Milky Way.

3. Observation Tips
It is diﬃcult to see the Milky Way with naked-eyes in urban area because of light pollutions. It is better to avoid
even the Moonlight. However, if you watch the Milky Way with the telescope, you can understand that many stars arein the Milky Way. For making sure, it is better to observe two points: one is inside of the Milky Way and another one isfar away from the Milky Way.
When you decide the observing point in the sky through telescope, tighten the tripod to ﬁx the telescope at once.
Then, adjust telescope focus. It is advisable to have a practice session by using distant scenery in daytime.

4. Steps(a) Observation and sketch
For observation and sketch, you use the ﬁrst sheet.
There are two sketch columns: for a sketch of inside of
the Milky Way and for an away from the Milky Way.
Mark the observation points in star chart, like the image.
Magniﬁcations of the telescopes are as follows:
For Hoshi-no-Techou Inc. telescope kit,
the magniﬁcation is a 15 power(Focal length of the telescope is 273mm
and focal length of the eye piece is 18.2mm).
For ORBYS Inc. telescopes kit , it is a 35 power(Focal length of the telescope is 420mm
and focal length of the eye piece is 12mm).
(b) Write any ﬁndings and/or questions
Write anything you found out and/or question
from your observations in your sketch sheet
under the sketch column.

Images provided by Stellanavigator / AstroArts Inc.

(c) Check your understandings
There are 3 check points in the sheet.
(d) See the seasonal changes of the Milky Way in summer
and winterYou can compare two pictures on the work sheeof the post observation study.
(e) Estimate the shape of the Milky Way galaxy by investigating
the picture on the work sheet(e-1) Trace the edges of the Milky Way galaxy onthe picture.
Teacher may help children to notice bulging
galactic center.
(e-2) Think why the Milky Way has a seasonal change.
Teacher may explain the location of the Earthin the Milky Way galaxy.
Images provided by
the National Astronomical Observatory of Japan(f) Use the “Mitaka”, which is a software that show celestial objects in the universe, then explain the shape of theMilky Way and where we are in the Galaxy.
Teacher can download the “Mitaka” from the following URL. It is a free software.
http://4d2u.nao.ac.jp/html/program/mitaka/index̲E.html(g) Teachers lecture on the outside of the Milky Way galaxy
Teachers explain there are many galaxies distributed outside of our galaxy. The history how we know theoutside of the Milky Way galaxy step by step should be explained.
(f) Write down what is learned today, and what you want to know more.
Let's summarize your knowledge of the Milky Way, which you learned from observations with the telescope
and through a text book or the internet. Also, write down what you want to know more and what you can do further.

5.Notes
Caution must be given to children that "Never watch the Sun through the telescope!”