I foolishly let my sink overflow (well, to be sure, a beaker fell into the drain and blocked it when I was running the water)*, so I must now clean up a big mess. But we have one good wildlife (or rather astronomy) photo today, from reader Tim Anderson in Oz. His notes are indented:
This image shows a set of emission and reflection nebulae embedded in the Sagittarius constellation (the objects are formally known as IC 6559, 4685, 1274 and 1275). The dark “river” running between the two bright stars to the left is an absorption nebula known as B303.
Imaged with a Skywatcher 254mm F4 Newtonian telescope, an ASI071MC Pro camera on an EQ8 mount. The image comprises ninety 90-second frames stacked and post-processed to taste.
Click to enlarge:
*Lesson: never leave running water unattended.
Beautiful Tim. Are those the naturally-occurring colors?
The answer isn’t simple.
Human colour vision is very brightness dependent. If you’ve got a big enough light bucket, you can get enough light into your eye to see bright colours, but you do need a big light bucket. Probably upwards of 350mm for this scene (the only time I’ve had access to such telescopes, they were fully rigged for CCDs and a range of filters ; and Sagittarius wasn’t in the sky at the time).
If you wait until the winter coming, you can compare the colours of the stars Betelgeuse and Rigel at opposite corners of the constellation of Orion with the naked eye. Near the mid-point of the line between the two is the popular object known as the Horsehead Nebula, but you’ll need a fairly good telescope and seeing to see that one.
That said, most astronomical images are made by “stacking” several exposures made through different filters, each of which passes a band of light wavelengths. The photographer then chooses which colours to assign to the different images before stacking. Many of the filters are chosen to correspond to particular chemically interesting components of the star, or a molecular cloud. Ionised oxygen and ionised hydrogen are popular choices for green and red respectively, with a high (frequency) pass for the blue end. There is science to be done from the filtered images, but the stacking process convolves the data to the point that you can’t easily re-extract the data, which is why imagery in scientific astronomical publications is generally presented as monochrome images with the filter details attached.
Ace. Imagine travelling through this, er, spacescape.
The reality is that it is so large and diffuse that if you were inside it you’d hardly notice.
(Contrary to what happens in Star Trek when they fly the Enterprise inside a nebula!)
I remember reading about the ‘collision’ that’s coming up, between our galaxy and the Andromeda galaxy, and it was striking to learn that the likelihood of any stars or planets from the two galaxies ever colliding is basically zero. The two galaxies will just pass through one another.
Of course the gravitational influence of their constituent parts is a different thing altogether: that will cause chaos. But actual, physical collisions are extremely unlikely.
It gives you a hint of just how stupefyingly empty space is, and of the mind-boggling distances between each star, even in a galaxy.
“… the likelihood of any stars or planets from the two galaxies ever colliding is basically zero. The two galaxies will just pass through one another.”
Yes, the stars will not collide, but the gas and dust component of the galaxies does collide, so the result can be separation of the stars from the gas/dust.
On the average, the likelihood of two stars colliding in a galactic collision is low, but in more compact objects the likelihood increases. In particular (though there are other examples), the objects known as globular clusters frequently have abnormally bright, blue stars (the so-called “blue stragglers“) which are generally accepted to be the result of star mergers in the relatively recent past. Globular clusters are useful probes, as they are relatively small and compact, so their stars can be treated as being at the same distance, and their photometric brightness can be taken directly as proportional to their absolute luminosity, so you can construct a Hertzsprung-Russell diagram directly from two or three filtered images. In such diagrams, the “blue stragglers” stand out.
There are other theories to account for the blue stragglers, but the merger origin is considerably the leader.
… or small fires.
Gorgeous pic.
I love this. It’s so beautiful.
I used to have a wonderful book(I can’t remember what it was called as I foolishly gave it to my dad) that was a collection of photography of nature that gradually progressed from the quantum scale to the relativistic scale…from electron microscopy all the way up to the Hubble deep-field shot.
I used to spend hours staring at the extreme stuff that starts and ends the book, trying to get my mind to really accept what I was looking at, but I never quite managed it.
What a lot of stuff ! And, to think that this was all put together by an immaterial deity is absolutely crazy! And we let them get away with perpetuating this Great Lie. GROG
Omg, the number of times I’ve done that! Sorry for your misfortune:(
The “B” series of astronomical objects is a list of “dark nebulae” – cool clouds visible against an illuminated background – compiled by E. E. Barnard in the early years of last century and published in early 1919 (I noticed no celebration in the astronomical community about that ; bit surprising that). Unsurprisingly, the bright star clouds and emission nebulae of the galactic centre (Sagittarius) form a good backdrop for seeing such things. Otherwise, it’s the old “black cat in a coal cellar at midnight problem. They’re not all in that part of the sky though – the much-photographed “Horsehead Nebula” is at number 33 on this hit parade.
Barnard also discovered the star with the highest proper motion (movement on the plane of the sky) now known as “Barnard’s Star“, unless it has been demolished recently for a hyperspace bypass.
The left of the image has a misty look. Probably gas and dust reflecting local stars. On the left though you can see some pure black areas that seem to go on for ever and for ever. But, as we well know, the Hubble Deep Space images revealed yet more galaxies beyond and beyond.
Thanks Tim, I love astronomy photos. They’re mesmerizing.
+!