m61 dimension and brightness
TRANSCRIPT
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 60 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/pixel
Distance 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 width, we started zooming the imageto have more accuracy and traced a line along the bulge.
Bulge width = 23 arcsec
Bulge width = 23 / 60 == 0,4 arcmin
Bulge width* = = 0,38 x 52,5 x 0,3 = 6,3 kly
* size in kly = size in arcmin x distance from Earth in Mly x 0.3
BULGE WIDTH
To measure the M61 width, we traced a line along the galaxy.
M61 width = 323 arcsec
M61 width = 323 / 60 == 5,4 arcmin
Real width = 5,8 arcmin
(Wikipedia)
M61 width* = = 5,4 x 52,5 x 0,3 = 85 kly
* size in kly = size in arcmin x distance from Earth in Mly x 0.3
M61 WIDTH
To measure the M61 height, we traced a line along the galaxy.
M61 height = 327 arcsec
M61 height = 327 / 60 == 5,5 arcmin
Real height = 6,5 arcmin
(Wikipedia)
M61 height* = = 5,5 x 52,5 x 0,3 = 86,6 kly
* size in kly = size in arcmin x distance from Earth in Mly x 0.3
M61 HEIGHT
M61 RATIO
Ratio width / height = 323 / 327 = 0,99
The ratio is near 1, so the galaxy is almost round.
M61 BRIGHTNESS
We 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