Question

section 1 stars continued
does distance change a stars brightness?
if you look at a row of street lights, do all of the lights
look the same? the nearest lights look brightest, and the
farthest ones look dimmest.
take a look

1. identify circle the

dimmest light in the picture.
put a box around the
brightest light.

1. explain the street lights

are all equally bright. why do
they appear different?
the closer a light is, the brighter it looks.
the brightness of a star as we see it from earth is
the stars apparent magnitude. a bright star can look
very dim if it is very far away from earth. a dim star can
appear bright if it is closer to earth.
a stars absolute magnitude is the actual brightness
of the star. if all stars were the same distance away, their
absolute magnitudes would equal their apparent magni-
tudes. for example, the suns absolute magnitude is
+4.8, but because it is close to earth, its apparent
magnitude is -26.8.
math focus

1. calculate what is the

distance in kilometers from
earth to a star that is 30 light
years away?
how do scientists measure distance to a star?
the distance between earth and the stars is too large to
be measured in miles or kilometers. instead, scientists use a
unit called a light - year, which is the distance that light can
ravel in one year. one light year equals 9.46 trillion kilome-
ters. how can scientists measure such a large distance?
as earth revolves around the sun, stars close to earth
seem to move, but far - off stars do not. this is called
parallax. scientists use parallax and math to find the
distance between earth and stars. to understand parallax,
think about riding in a car past a large mountain. as you
drive past the mountain, it seems to move. however, the
mountain is not actually moving. it is your motion compared
to the mountain that makes the mountain seem to move.

Explanation:

Step1: Identify the conversion factor

1 light - year = 9.46 trillion kilometers = 9.46×10^{12} kilometers

Step2: Calculate the distance

The star is 30 light - years away. So the distance d = 30×9.46×10^{12} kilometers
d = 283.8×10^{12} kilometers = 2.838×10^{14} kilometers

Answer:

2.838×10^{14} kilometers