Optical versus x-ray image
http://chandra.harvard.edu/xray_astro/discover.html
http://chandra.harvard.edu/xray_astro/clues.html
http://chandra.harvard.edu/xray_sources/sco/sco.html
(sun)
Have you ever looked up at the sky and wondered how far the stars are from Earth? Which stars are closer
to us and how can we tell? Does the brightness of the star mean that the star is closer to us? Can we even
answer these questions? If we can, how do we know what we know?
Let’s find out! Go to the section on coordinate systems.
It’s the year 2006, and the amazing astrophysicists at NASA have done it again. They have made the once
science fiction movie a reality. No more day dreaming about flying with Hans in space. We have our own
ship and it is a million times better than the Millenium Falcon. The only problem is that not many people
know their way around space yet. How will we ever learn how to travel in space if we haven’t the faintest
idea where the objects are in relation to each other? Luckily, the ingenious scientists had developed a
system to relate the objects in space to each other. Let’s take the course on coordinate systems so we can
get flying in outer space!
Some of you may be asking what exactly are coordinate systems? Believe me, most of you probably know
more that you think. We use coordinate systems all the time on Earth. We can graph equations on the x-y
coordinate system, we can read a map and determine how to get to our final destination, and we are all
familiar with the latitude and longitude lines that we drawn on maps of the Earth. But how do we map the
universe?
For more information on coordinate systems click on the picture below to access a website designed by
Peter H. Dana The Geographer's Craft Project, Department of Geography, The University of Colorado at
Boulder. http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html
Add picture http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html
That’s right, we use coordinate systems! Click on the map of the universe to learn more.
http://chandra.harvard.edu/photo/map/ (picture to click on)
http://chandra.harvard.edu/xray_astro/navigation.html (website to link to)
Choose all of the possible answers.
The galactic plane is analogous to the
a.) Prime Meridian
b.) Equator
c.) Tropic of Capricorn
d.) Tropic of Cancer
How is the coordinate system used for the universe more complicated than the coordinate system used for
the Earth? (Hint: Think about the space the Earth occupies).
Can you think of a disadvantage of plotting the universe on a map like the one above?
Okay, so now we know how we can map the objects in space on a map. But how can we determine how far
the objects are from Earth? We just have to interpret the map.
Look at the pictures below. Take note of the galactic coordinates.
(I attached the picture because I didn’t know if they would all fit).
So now you are thinking, “Okay, I know about galactic coordinates, I can determine how far objects are in
the sky, but what if I want to get somewhere in space? How do I find the galactic coordinates?” Don’t
worry, determining the galactic coordinates is as easy as obtaining directions on MapQuest. Unfortuantely,
you will have to determine the best route to get to your destination. Hey, I never said being a pioneer was
easy. But don’t worry you shouldn’t run into too many meteors.
First, load the Chandra image that you are interested in and the analysis software into Ds9.
Next go to the “WCS” option on the toolbar. Scroll down and choose “Galactic”.
Next, go the “Analysis” option on the toolbar and choose “Display Coordinate Grid”.
When you click on “Display Coordinate Grid,” gridlines should appear that are similar to the image below.
When you move the mouse to the red line the galactic coordinates (l, b) will appear.
You have just found the galactic coordinates. Now it is time for the interpretation.
Helpful websites
http://cse.ssl.berkeley.edu/chips_epo/coordinates2.html
http://scienceworld.wolfram.com/astronomy/EquatorialCoordinates.html
Given equatorial coordinates (declination) and (right ascension), the galactic coordinates (b, l), can be
computed from the formulas
The first system was defined in 1932 using optical observations of the Milky Way Galaxy. The new system
was defined in 1958 in terms of 21 cm observations of HI (Sullivan 1984, p. 140).
Declination
The celestial coordinate of an object corresponding to latitude projected on the sky.
Declination is measured from -90° (projected south pole) to projected north pole), with
corresponding to the celestial equator
Right Ascension
The azimuthal angle at which the hour circle of a celestial object is located. The rotation
axis taken as the direction of the celestial pole. Right ascension is usually measured in
units of time (hours, minutes, and seconds), with one hour of time approximately equal to
15° of arc (360°/24 hours=15°/hour). Because the time for the Earth to complete a
rotation relative to the "fixed" stars is slightly shorter than the time to complete a rotation
relative to the Sun (a sidereal day is 23 h 56 m 4.1 s, whereas a solar day is 24 hours), one
hour of right ascension is actually equal to 360°/23.9344...hours= /h. The zero point of
right ascension is the first point in Aries, just as the zero point for longitude on the Earth
is the prime meridian.