Starship Asterisk*

Chris Peterson wrote:

bystander wrote: 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.

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;

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

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.

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.

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....

Ann wrote:
I would, in fact, guess that NGC 4302 is indeed physically bigger than NGC 4298. Even though these galaxies might well be separated by 2 million light years or so, at a distance of ~55 million light-years that wouldn't affect the apparent size of them all that much. Indeed, such a separation could enhance the apparent difference in size, but I don't think it could create it from scratch if these two galaxies were indeed the same size. NGC 4302 does appear to have a more extensive disk. Also NGC 4302 appears yellower than NGC 4298. Yes, edge-on galaxies typically appear yellower than face-on ones, because the dust lane itself imparts reddening, but in the case of NGC 4302 it definitely has a yellow inner disk. Larger galaxies are expected to have produced a larger yellow population than smaller galaxies.

So I would think that NGC 4302 is bigger than NGC 4298, but I also think that these galaxies are separated by a sufficiently large distance that they don't cause much tidal stretching of each other's disks.

http://asterisk.apod.com/viewtopic.php?f=9&t=37102#p269784 wrote:
Since there is "little to no tidal stretching" it would seem reasonable to assume
that they are probably about 2 Mpc apart(; i.e., at 15.5 & 17.5 Mpc, respectively).

Ann wrote:

Chris Peterson wrote:

sytheblackwolfe wrote:The caption for the picture says that NGC 4298 is a "smaller companion" of NGC 4302, which I would assume means it lies at roughly the same distance of 55 million light-years. But if that's so, I'd expect to see a lot more interaction than just some tidal stretching of NGC 4298. Is it possible the distance estimate is incorrect for NGC 4298?

I would not assume "smaller" means physically smaller, but rather, apparently smaller.

Large astronomical distances are difficult to determine. The distance to these objects is only known to about a 20% error range. Either one could be one or two million light years farther away than the other and we'd have no clear way of telling that. In other words, they could easily be as far apart as the Milky Way and Andromeda, which have very little tidal interaction.

I would, in fact, guess that NGC 4302 is indeed physically bigger than NGC 4298.

Chris Peterson wrote:

sytheblackwolfe wrote:The caption for the picture says that NGC 4298 is a "smaller companion" of NGC 4302, which I would assume means it lies at roughly the same distance of 55 million light-years. But if that's so, I'd expect to see a lot more interaction than just some tidal stretching of NGC 4298. Is it possible the distance estimate is incorrect for NGC 4298?

I would not assume "smaller" means physically smaller, but rather, apparently smaller.

Large astronomical distances are difficult to determine. The distance to these objects is only known to about a 20% error range. Either one could be one or two million light years farther away than the other and we'd have no clear way of telling that. In other words, they could easily be as far apart as the Milky Way and Andromeda, which have very little tidal interaction.

Chris Peterson wrote:

Ann wrote:

Nitpicker wrote:Ann, click on the "Fast Facts" link at:
http://hubblesite.org/image/4019/gallery

Thanks, but the filter info there isn't very good, IMO:

The Hubble observations were taken between January 2 and January 22, 2017 with the Wide Field Camera 3 (WFC3) instrument in three visible light bands.

How so? Literally from that link,

Blue: F475W (B)
Green: F555W (V)
Red: F625W (r)

How much better can the information be?

BDanielMayfield wrote:
Is there a way to tell how far away from each other they are in the depth dimension? Since these two galaxies show little to no tidal stretching yet I'd surmise that they could really be much farther apart than they appear. Is there even any way to be sure which of these two is in front of the other?

• They are both part of the Virgo Cluster which is 2.2 Mpc in radius.
  
  Since there is "little to no tidal stretching" it would seem reasonable to assume
  that they are probably about 2 Mpc apart(; i.e., at 15.5 & 17.5 Mpc, respectively).

https://en.wikipedia.org/wiki/Virgo_Cluster wrote:
<<The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo. Comprising approximately 1300 (and possibly up to 2000) member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group is an outlying member. However, the Local Group experiences the mass of the Virgo Supercluster as the Virgocentric flow. It is estimated that the Virgo Cluster's mass is 1.2×10¹⁵M_☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc.

The cluster subtends a maximum arc of approximately 8 degrees centered in the constellation Virgo. Many of the member galaxies of the cluster are visible with a small telescope. Its brightest member is the elliptical galaxy Messier 49; however its most famous member is the also elliptical galaxy Messier 87, that unlike the former is located in the center of the cluster.>>

BDanielMayfield wrote:Is there a way to tell how far away from each other they are in the depth dimension? Since these two galaxies show little to no tidal stretching yet I'd surmise that they could really be much farther apart than they appear. Is there even any way to be sure which of these two is in front of the other?

RocketRon wrote:Very pretty.

How far apart might they be?

Ann wrote:Like RocketRon pointed out, there are few signs of interaction between NGC 4302 and 4298. Edge-on NGC 4302 looks completely undisturbed, but there are perhaps signs of some tidal stretchings of the disk of NGC 4298.

NCTom wrote:I echo the earlier question. How far apart are these guys? Visual alignment looks less than 100K light years. Such proximity might suggest more tidal interaction unless they have just arrived at this distance for the first time.

sytheblackwolfe wrote:The caption for the picture says that NGC 4298 is a "smaller companion" of NGC 4302, which I would assume means it lies at roughly the same distance of 55 million light-years. But if that's so, I'd expect to see a lot more interaction than just some tidal stretching of NGC 4298. Is it possible the distance estimate is incorrect for NGC 4298?

DLMartin wrote:Doesn't it matter that what is being observed happened 55 million years ago? Without subsequent data, what is the validity of present day conjecture?

Fred the Cat wrote:Speaking of pizzas are these thin crust or deep dish galaxies?

Ann wrote:

Nitpicker wrote:Ann, click on the "Fast Facts" link at:
http://hubblesite.org/image/4019/gallery

F475W (B), F555W (V), and F625W (r)

Thanks, but the filter info there isn't very good, IMO:

The Hubble observations were taken between January 2 and January 22, 2017 with the Wide Field Camera 3 (WFC3) instrument in three visible light bands.