Draco Dwarf Galaxy

[symmetal]

Continuing my Dwarf Galaxy collection here's the Draco Dwarf Spheroidal Galaxy. Five hours total LRGB using FLT98 and ASI6200. Processed in Startools and PS.

It's a satellite galaxy of the Milky Way, 260 ly distance, discovered in 1954. Some interesting facts are that the vast majority of its stars are variables, and it's the most dark matter dominated object known, (in 2007), so is a key object for the study of dark matter. It's also dust free, containing insignificant amounts of interstellar matter.

Click to view them full size. 🙂

Given a heavy stretch there is some IFN visible.

Alan

[wimvb]

On 07/06/2022 at 01:02, symmetal said:

It's a satellite galaxy of the Milky Way, 260 ly distance, discovered in 1954

Very nice!

Only 260 ly distant would be well within the Milky Way. 260 Kly according to Wikipedia.

[Len1257]

Despite the guide circle I'm still not sure which is the target?

Just an observation but I just compared my RC8 / ASI071 field of view to your FLT98 / ASI6200 and it looks as though you are making it very difficult for yourself? Looks as though you would get a much better field of view for this subject with your LX200GPS unless the wide field is what you are after? 

[symmetal]

11 hours ago, wimvb said:

Very nice!

Only 260 ly distant would be well within the Milky Way. 260 Kly according to Wikipedia.

Oops. Your right Wim. Forgot the k 

7 hours ago, Len1257 said:

Despite the guide circle I'm still not sure which is the target?

Just an observation but I just compared my RC8 / ASI071 field of view to your FLT98 / ASI6200 and it looks as though you are making it very difficult for yourself? Looks as though you would get a much better field of view for this subject with your LX200GPS unless the wide field is what you are after? 

The FLT98 and ASI6200 images at 1.2"/pixel so gives fairly detailed images near the limit of seeing, and due to the full frame sensor has a wide FOV of 2.3 degrees. I can crop just the object in question which I've done below for you, 🙂 though I find the wide field views show many extra little galaxies and features, so I've posted the full images. I've found that not all images show full size when clicked on, so I usually right click the image and select show in new window, which does allow the full size image to be viewed.

Dwarf galaxies are very faint objects so are not easy to see, which is one of the reasons I've imaged them, being a bit different to the usual deep sky images imaged, and get overlooked. 😊 They need fairly long image durations, and plenty of them, to reveal the faint galaxy stars and a single sub will show nothing of it. The LX200 is on a fork mount and so isn't really suitable for long exposures. I just use it for planetary.

Here's a full size crop of the Draco Dwarf from the full size image. It's the rough cluster of faint stars in the centre 'behind' the Milky Way stars in the foreground. Like all the local dwarf galaxies they are not very spectacular and have no 'wow' factor, but are interesting in their own right. If I stretch the image too much the stars lose their colours and even longer integration will show more of the stars.

Draco Dwarf Galaxy (full size crop)

Alan

[wimvb]

14 hours ago, Len1257 said:

Despite the guide circle I'm still not sure which is the target?

Just an observation but I just compared my RC8 / ASI071 field of view to your FLT98 / ASI6200 and it looks as though you are making it very difficult for yourself? Looks as though you would get a much better field of view for this subject with your LX200GPS unless the wide field is what you are after? 

The galaxy is so faint and difficult to see because individual stars are visible. It's like identifying certain trees in a forest. You actually need a moderate focal length to be able to see the galaxy, or you won't see it for all the stars. The third (overstretched) image shows the dwarf best. Hunting ultra faint dwarf galaxies is all about stretching your gears performance and your abilities to the limit (no pun intended).

[Len1257]

Thanks for the help and explanation. I really had no idea what I was looking for. From the stretched image it seems to be visually like a open cluster. I was looking for something more traditionally 'galaxy' shaped! 

[wimvb]

5 hours ago, Len1257 said:

traditionally 'galaxy' shaped! 

Ultrafaint dwarf galaxies are seldom photogenic, but they have a fascinating physics history. These galaxies can form in the wake of galaxy mergers or galaxy collisions. And because they are so sparse and faint, they require patience and persistence from the observer.

[symmetal]

5 hours ago, Len1257 said:

Thanks for the help and explanation. I really had no idea what I was looking for. From the stretched image it seems to be visually like a open cluster. I was looking for something more traditionally 'galaxy' shaped! 

Dwarf spheroidal galaxies are similar to globular clusters in that they are both roughly spherical in shape and consist of old stars which are gravitationally bound. The dwarf galaxies have stars which are more spread out, and the galaxies are around 1000 to 2000 light years in diameter while globular clusters are around 100 light years across. The light output from dwarf galaxies is spread over a larger area so appear much dimmer, and they are also significantly further away than the globular clusters we can see.

Globular clusters we can see exist within the Milky Way galaxy, while the dwarf galaxies are outside the Milky Way. As they are separate from the Milky Way they are classed as galaxies in their own right.

Most dwarf galaxies that we see are orbiting the Milky Way or the Andromeda Galaxy. As they contain far fewer stars and are much smaller than their 'parent' galaxies they are classed as dwarf galaxies.  Hopefully they are not 'offended' by this classification. 😊

By contrast, open clusters consist of new stars which formed from the same mass of source material but are not gravitationally bound, so have drifted apart throughout their lives forming irregular shapes of stars. Open clusters tend to exist in the outer spiral arms of the Milky Way.

Alan