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1. What are the spectral classes of stars that have the following maximum light wavelengths?

You will need to refer to the H-R Diagram!

(a) 3 x 10-5 cm (b) 1.5 x 10-5 cm (c) 5.5 x 10-5 cm (d) 1.25 x 10-4 cm

2. In what region of the electromagnetic spectrum would objects with the following temperatures be best observed by a scientist's experiment?

(a) .001 K (b) 800 K (c) 15,000 K (d) 1,750,000 K

Suggested Extension:

Are there really objects in space that have a temperature of 0.001 K? What are you detecting at that temperature?

Bigger than a Breadbox?

The Universe is a very big place and it contains some very big objects. In many images scientists create from data, it is difficult to understand the actual sizes of the objects. In this activity, we want to understand the extent (or size) of some supernova remnants. We will do this by applying a simple physics equation.

In physics, we know that velocity = distance traveled / time it takes to travel that distance.

v=d/t or d=vt

For this activity, we know that the distance (d) traveled is equivalent to the distance from the initial or central star of the supernova remnant, to the edge of the outer material of the remnant. In addition, we know the velocity (v) at which the material of each remnant is expanding outward, and understand that as the remnant gets older the velocity slowly decreases. Lastly, we know how long ago (t) the initial star blew up in a supernova explosion.

Use this information, and the following data to determine the biggest supernova remnant among those listed below. Be careful with the dimensional analysis!


Cygnus Expansion Velocity = 1,450 km/sec Age = 20,000 years

Crab Expansion Velocity = 1,500 km/sec Age = 943 years

Tycho Expansion Velocity = 5,200 km/sec Age = 425 years

SN1006 Expansion Velocity = 3,000 km/sec Age = 990 years

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Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

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