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Re: APOD: NGC 4302 and NGC 4298 (2017 Apr 21)
Posted: Sat Apr 22, 2017 2:00 am
by Ann
heehaw wrote:The late Alan Sandage of cosmology fame was at Johns Hopkins briefly about the time he published his
https://www.amazon.com/Hubble-Atlas-Gal ... 0872796299
Please don't buy this Atlas: it is incredibly antique, with black-and-white photos of galaxies. How things have changed!
Alan engaged in a HUGE battle over the value of the Hubble parameter: Alan argued for (hold your breath) 42, while De Vaucouleurs argued for 100. There was an historic debate in DC, not between those two, who despised each other, but between stand-ins (for De Vaucouleurs, my Masters thesis advisor, Sidney van den Bergh, and for Alan, Gustav Tamman). It was a draw (I was there). Of course the current value is about half way between the two, but slightly closer to Alan's value I guess. I was enjoying drinks at a table in Italy when Alan invited Gus to join him in California....
I bought those books! And I couldn't agree more with your assessment! There are at least two volumes, huge, heavy and terrifically unwieldy, with large, blurry, black and white photos. Those books and photos must have been great at their time, but now the're fit for the scrapheap, I'm sorry.
NGC 4302... NGC 4298... M94... M33... NGC 891... M81 - oh, too small... M82...
And they must make a lot of smoke when they burn.
Ann
Re: APOD: NGC 4302 and NGC 4298 (2017 Apr 21)
Posted: Sat Apr 22, 2017 11:54 am
by DavidLeodis
The "Virgo Galaxy Cluster" link
https://apod.nasa.gov/apod/ap150804.html brings up the APOD of August 4 2015. Clicking on that image (at least when online) brings up a very useful annotated version on which NGC 4302 and NGC 4298 can be found labelled in the lower right quadrant of the image.
Re: APOD: NGC 4302 and NGC 4298 (2017 Apr 21)
Posted: Sat Apr 22, 2017 1:29 pm
by Chris Peterson
De58te wrote:I Googled NGC 4302 and NGC 4298 and the first hit that wasn't this Apod page or a youtube page that zoomed in on the Hubble Image, was the Deep Sky Object Search. According to them the distance of NGC 4302 is 53 M light years, and the distance of NGC 4298 is 52 M light years. So NGC 4298 is 1 M light years in front of 4302 and therefore closer to us making it truly smaller than its companion.
I wouldn't place much value on those distances. The range given in the literature is much wider, and these values are on the extreme low side of most estimates. One million light years is much smaller than the error bars on the measurements.
Re: APOD: NGC 4302 and NGC 4298 (2017 Apr 21)
Posted: Sat Apr 22, 2017 2:28 pm
by bystander
De58te wrote:.
So NGC 4298 is 1 M light years in front of 4302 and therefore closer to us making it truly smaller than its companion.
The
ESA Hubble post on this image places the distance between the galaxies at ~ 7000 light years which makes the lack of significant visible interaction between them truly amazing.
http://asterisk.apod.com/viewtopic.php?t=37094
Re: APOD: NGC 4302 and NGC 4298 (2017 Apr 21)
Posted: Sat Apr 22, 2017 2:52 pm
by Chris Peterson
bystander wrote:De58te wrote:.
So NGC 4298 is 1 M light years in front of 4302 and therefore closer to us making it truly smaller than its companion.
The
ESA Hubble post on this image places the distance between the galaxies at ~ 7000 light years which makes the lack of significant visible interaction between them truly amazing.
http://asterisk.apod.com/viewtopic.php?t=37094
I'd certainly like to know how they came to that conclusion.
Re: APOD: NGC 4302 and NGC 4298 (2017 Apr 21)
Posted: Sat Apr 22, 2017 4:33 pm
by bystander
Chris Peterson wrote:
I'd certainly like to know how they came to that conclusion.
Ok, perhaps I read that a bit hurriedly. They may be referring to the angular separation, only.
ESA Hubble wrote:
At their closest points, the galaxies are separated from each other in projection by only around 7000 light-years. Given this very close arrangement, astronomers are intrigued by the galaxies’ apparent lack of any significant gravitational interaction;
