This week’s astro-challenge may test your skills as a “visual athlete;” a close visual conjunction of the planet Saturn and the galaxy NGC 4073. This unique event comes to us via the computations of reader Ed Kotapish. On the evening of July 25th, both planet and galaxy will be in a 1 degree field of view. The challenge is twofold; Saturn sits at magnitude +1.1, while NGC 4073 is about 10,000 times fainter at magnitude +11.4. Add into the mix a Moon just a day from Full, and you’ve got a definite challenge… telescopes of 6” inches aperture or larger need only apply. For success, I would place the Moon behind a building or structure when selecting your observing site. Attempt to acquire the galaxy first; an occulting bar eyepiece or placing brilliant Saturn just outside of the field of view will help in this endeavor. Then bring them both in, using not more than x40 to x80 magnification. Finally, don’t forget to contemplate what you’re seeing; Saturn lies a mere average 60 light minutes distant, while NGC 4073 lies hundreds of millions of light years away! On a personal note, Saturn is now in the bowl of Virgo, a galaxy rich area of the sky, almost exactly where it was 29 years ago, when I first got into astronomy! I wonder what I’ll be doing 29 years from now when I’m 70…. Thanks, Ed!
This weeks’ Astroterm of the Week is Dynamical Friction. This action plays a key role in the development of cD-type galaxies such as NGC 4073. A giant elliptical such as NGC 4073 will draw in smaller galaxies and gas and dust as it moves through a galaxy cluster. This also acts to drag on the larger galaxy, gradually causing it to work its way into the core of the galaxy cluster. The galaxy may then consume other members of the cluster, increasing in size or fuelling additional star formation. NGC 4073 controls one such galaxy grouping designated, MKW-04 also known as WBL 378. NGC 4073 stands as the brightest member of this grouping, a fine target for large telescopes about 1.5’ x 2.5’ arc minutes in size. Good luck, and do let us know if you are successful!