Date post: | 13-Apr-2017 |
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M61 DIMENSION AND
BRIGHTNESS
Eduarda Leal
INDEX M61 Image scale Bulge Width Height Ratio Brightness References
M61M61 was discovered by Barnabus Oriani on May 5, 1779 when following the comet of that year, 6 days before Charles Messier's discovery, who had seen it on the same day as Oriani but mistaken it for the comet, until he realized that it did not move.It is classified as a spiral galaxy of type SABbc, is 52,5 million light-years away from the Milky Way and is located in the constellation of Virgo (Virgin).
With the program SalsaJ we can analyse and measure images.In the M61 Image Info we can find the CCDSCALE: 0,3 arcsec/pixel
Image width = 2008 pixels
Real distance = 2008 x 0,3 = 602 arcsec
Image scale = 2008 / 602 = 3,336 pixels/arcsec
Image scale = 3,336 x 60 = 200 pixels/arcmin
IMAGE SCALE
We can calculate the image scale in kly/pixel with this equation:scale in kly = scale in arcmin / (distance from Earth in Mly x 0.3)
CCDSCALE = 0,3 / 60 = 0,005 arcmin/pixelDistance from Earth = 52,5 Mly
Image scale = 0,005 / (52,5 x 0,3) = 3,2 x 10-4 kly/pixel
IMAGE SCALE
To measure the bulge, we started zooming the image to have more accuracy and traced a line along the bulge.
Bulge = 22,856 arcsec
Bulge = 22,856 / 60 = 0,381 arcmin
Bulge* = 0,381 x 52,5 x 0,3 = 6,0 kly = 6 000 light-years
* size in kly = size in arcmin x distance from Earth in Mly x 0.3
BULGE
To measure the M61 width, we traced a line along the galaxy.
Width = 322,887 arcsec
Width = 322,887 / 60 = 5,381 arcmin
width* = 5,381 x 52,5 x 0,3 = 84,751 kly = 84 751 light-years
Real width = 5,8 arcmin (Wikipedia)
Real width* = 5,8 x 52,5 x 0,3 = 91,4 kly = 91 400 light-years
* size in kly = size in arcmin x distance from Earth in Mly x 0.3
WIDTH
To measure the M61 height, we traced a line along the galaxy.
Height = 327,387 arcsec
Height = 327,387 / 60 = 5,456 arcmin
Height* = 5,456 x 52,5 x 0,3 = 85,939 kly = 85 939 light-years
Real height = 6,5 arcmin (Wikipedia)
Real height* = 6,5 x 52,5 x 0,3 = 102,4 kly = 102 400 light-years
* size in kly = size in arcmin x distance from Earth in Mly x 0.3
HEIGHT
RATIORatio width / height = 322,887 / 327,387 = 0,99
The ratio is near 1, so the galaxy is almost round.
BRIGHTNESSWe made a line along the galaxy to measure the brightness.Then we analyse the light in that line and SalsaJ plot a graph of light intensity vs distance (arcsec).The brightness is more intense in the center of the galaxy and the bulge is very bright.
REFERENCES http://resources.faulkes-telescope.com/course/view.php?id=65 http://lcogt.net/observations/ogg/2m0a/11593/ http://en.wikipedia.org/wiki/Messier_61 http://upload.wikimedia.org/wikipedia/commons/a/a4/Charles_Messier.jpg http://www.euhou.net/index.php/salsaj-software-mainmenu-9