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NGC 1569 NGC 1569

Optical wavelength image of NGC 1569

The same image, but with the scaling modified so as to reveal the galactic core(s).

Discovered on November 4, 1788 by William Herschel, NGC 1569 remains an active topic of study to this day. NGC 1569 is located in the constellation of Camelopardalis and lies at a distance of about 3.36+/-0.20 Mpc or 11.0+/-0.7 Mly. It is an irregular galaxy (classified as Irp+ III-IV), which means it is neither spiral, elliptical, nor anything in between. Indeed, by looking at the image one cannot make out any spiral arms, and its overall shape is far from elliptical. Aside from being irregular, NGC 1569 is also classified as a starburst galaxy. This means that it contains active areas of star formation.

So let's try to get a better of idea of just what NGC 1569 is. Examining the colors present, we see quite a bit of blue and red. The blue light comes from very hot, young stars, and the red likely comes from the dusty regions these stars were birthed in. As we can see, these colors paint a picture of active star formation. So far, this starburst galaxy is living up to its title. As a side note, the bright stars in the image are not associated with NGC 1569. Rather, they are stars within the Milky Way.

There also appear to be three bright regions in the center of the galaxy. Measuring the relative intensities of different colors along a line through these three bright regions can tell us more about them. The graph below shows these relative intensities. The right-most bright area, the dimmest of the three, appears to be dominated by red wavelength light. This could indicate thermal emission nebulae, which contain hot young stars. The left-most bright region also appears to be red, likely signifying similar characteristics to the right-most bright region. The middle region, the brightest, is dominated by blue light. This implies the presence of many hot young stars. As it turns out, these three bright regions are actually massive clusters of young hot stars. In the right-most region, the cluster is still partially obscured in the glowing red nebula it was birthed in.

Line Measurement

Line Measurement Graph

Now we will calculate the approximate size of NGC 1569. By measuring the intensity of light along a line (not the one shown above) through the longest part of the galaxy, I found that the galaxy's major axis spans about 125 pixels on my image. By the same process, I found the minor axis to be about 54 pixels. Since each pixel on my image corresponds to about 1.32 seconds of arc, the angular dimensions of NGC 1569 are about 165 x 71 arcsec or 2.75 x 1.2 arcmin. Given that it lies at a distance of about 11.0 million light years, this yields an approximate galactic size of 8800 x 3800 ly.

This infrared image of NGC 1569 shows the warm, star-nursery interior of the galaxy nicely, as well as its outer dusty regions. These massive dusty bubbles are the result of successive rounds of massive star formation and death. Astronomers estimate that it produces new stars at well over 100 times the rate that our Milky Way does, and it has been keeping up this pace for over 100 million years. Notice that the brightest parts of this infrared image surround the three bright star formation regions. Astronomers believe NGC 1569 owes its starburst nature to gravitational interactions with one of its closest neighbors, the spiral galaxy IC 342.

References:

Frommert, Hartmut. "NGC 1569." Local Galaxies. <http://spider.seds.org/spider/LG/n1569.html>

Grocholski et al. "A New Hubble Space Telescope Distance to NGC 1569: Starburst Properties and IC 342 Group Membership". Astrophysical Journal Letters. <http://adsabs.harvard.edu/abs/2008ApJ...686L..79G>

A. Aloisi. "Hubble Resolves Puzzle About Loner Starburst Galaxy". <https://www.nasa.gov/mission_pages/hubble/science/hst_img_20081120.html>

Constellation Guide <http://www.constellation-guide.com/wp-content/uploads/2011/02/>

Wikipedia, "NGC 1569".

Object NGC 1569
Right Ascension (J2000) 04:30:49.1
Declination (J2000) +64:50:53
Filters used B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B(300s x 10), V and R (120s x 11); C (60s x 11)
Image dimension 330x275 pixels; 7.26x6.05 arcminutes
Date/time observed March 2, 2017, 02:07 UT

Image Calibration

First the biases and the darks were averaged separately. The average bias and dark were used to calibrate the flats. The calibrated flats were then combined. The bias, dark, and flats were then used to calibrate the images before they were also averaged. The color image was saturated to 150%.

 

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