Starship Asterisk*

M46 Plus Two

Explanation: Galactic or open star clusters are young. These swarms of stars are born together near the plane of the Milky Way, but their numbers steadily dwindle as cluster members are ejected by galactic tides and gravitational interactions. In fact, this bright open cluster, known as M46, is around 300 million years young. It still contains a few hundred stars within a span of 30 light-years or so. Located about 5,000 light-years away toward the constellation Puppis, M46 also seems to contain contradictions to its youthful status. In this pretty starscape, the colorful, circular patch above and right of the center of M46 is the planetary nebula NGC 2438. Fainter still, a second planetary nebula, PK231+4.1, is identified by the box at the right and enlarged in the inset. Planetary nebulae are a brief, final phase in the life of a sun-like star a billion years old or more, whose central reservoir of hydrogen fuel has been exhausted. NGC 2438 is estimated to be only 3,000 light-years distant, though, and moves at a different speed than M46 cluster members. Along with its fainter cohort, planetary nebula NGC 2438 is likely only by chance appearing near our line-of-sight to the young stars of M46.

<< Previous APOD

This Day in APOD

Next APOD >>

[/b]

That's a wonderful picture! I love it!

I have to wonder, though, how old a cluster has to be for one of its members to turn into a planetary nebula. Yes, certainly it will take several billion years before a star like the Sun sheds its outer layers and lights them up from within with its blisteringly hot dead core. But what about stars that are a lot more massive than the Sun, but not massive enough to explode as supernovas? Surely they will turn into planetary nebulas and white dwarfs much sooner than the Sun. Is 300 million years really not enough?

Ann

Is it possible to see those sapphire jewels in 3-d by imaging in opposite seasons? That would be amazing. Sometimes when I'm looking through an eyepiece it almost seems to have depth, so even he slightest hint of it would be something.

Nomination of the name...."The Eye Nebula".....click the link, and see other pics down the page...

Also...not really a member, as the comment says...2.9kly vs 5.4 for the cluster....so age may not be a factor to the cluster.

:---(===) *

daddyo wrote:Is it possible to see those sapphire jewels in 3-d by imaging in opposite seasons? That would be amazing. Sometimes when I'm looking through an eyepiece it almost seems to have depth, so even he slightest hint of it would be something.

Although these stars are, in a sense, in our "neighboring", nonetheless
they are much much much too far for any annual parallax to be discernible !

The APOD's caption provides us with all the data we need : do your
own calculation by yourself, determine the parallax (i.e : viewed from that star cluster, what angle does the sun's orbit sustend, being ~300 million kilometres or ~16 minutes of light's time ?) It is elementary and easy geometry and I'm sure you will
learn more by working out the numbers by yourself, as you should have done before even posing a question)...

Good day and starry nights !

--
Czerno

daddyo wrote:Is it possible to see those sapphire jewels in 3-d by imaging in opposite seasons? That would be amazing. Sometimes when I'm looking through an eyepiece it almost seems to have depth, so even he slightest hint of it would be something.

Extract from Wikipedea (Stellar Parallax)

In 1989 the satellite Hipparcos was launched primarily for obtaining parallaxes and proper motions of nearby stars, increasing the reach of the method tenfold. Even so, Hipparcos is only able to measure parallax angles for stars up to about 1,600 light-years away, a little more than one percent of the diameter of the Milky Way Galaxy. The European Space Agency's Gaia mission, launched 19 December 2013, will be able to measure parallax angles to an accuracy of 10 microarcseconds, thus mapping nearby stars (and potentially planets) up to a distance of tens of thousands of light-years from Earth. A use of the Hubble telescope WFC3 now has the potential of a precision of 20 to 40 microarcseconds, enabling reliable distance measurements up to 5,000 parsecs (20,000 ly).

Also...

The motion of the Sun through space provides a longer baseline that will increase the accuracy of parallax measurements, known as secular parallax. For stars in the Milky Way disk, this corresponds to a mean baseline of 4 A.U. per year, while for halo stars the baseline is 40 A.U. per year. After several decades, the baseline can be orders of magnitude greater than the Earth–Sun baseline used for traditional parallax. However, secular parallax introduces a higher level of uncertainty because the relative velocity of other stars is an additional unknown. When applied to samples of multiple stars, the uncertainty can be reduced; the precision is inversely proportional to the square root of the sample size.

So what you are suggesting may be possible within some margin of error. If the data is available, it would make for an interesting project.

Czerno o wrote:...as you should have done before even posing a question

There are no bad questions, but there are bad answers. All knowledge starts with the simple premiss "I don't know", and then we ask someone who knows more than we do. It is hard enough to get kids/adults away from their iPods & smart phones and actually start thinking for themselves. It doesn't help when they are made to feel stupid when they try. Just my opinion.

Why do many of your starfield shots look like they've been shot thru a starburst filter? Because they have??? I would think most people would like to see the real image, not a doctored one.

Guest wrote:

...as you should have done before even posing a question

There are no bad questions, but there are bad answers. All knowledge starts with the simple premiss "I don't know", and then we ask someone who knows more than we do. It is hard enough to get kids/adults away from their iPods & smart phones and actually start thinking for themselves. It doesn't help when they are made to feel stupid when they try. Just my opinion.

It was none of my intention to make anybody feel stupid, on the contrary,
by hinting simple "back of an envelope" type calculations by which they could gain some more intelligence of the problem by themselves I was hoping to help them feel more intelligent, not more stupid ! Try to exploit the ressources of one's human intellect first, then ask for confirmation; not the reverse, lazy way which the internetz have made all too easy.

This also just my opinion, and not meant to imply the OP in particular was lazy or anything, and I apologize if you -or they- felt otherwise.

Furthermore thank you, Guest! for those updated references to the limit resolutions soon to be attainable of parallax measurements. Truly amazing, thinking few years back when I was young accurate estimation of annual parallactic shifts under 0.1 arcsec would've been considered sorcery, not science.

Peter Bradford wrote:Why do many of your starfield shots look like they've been shot thru a starburst filter? Because they have??? ....

No

http://en.wikipedia.org/wiki/Diffraction_spike wrote:Diffraction spikes are lines radiating from bright light sources in reflecting telescope images. They are artifacts caused by light diffracting around the support vanes of the secondary mirror.

Peter Bradford wrote:Why do many of your starfield shots look like they've been shot thru a starburst filter? Because they have??? I would think most people would like to see the real image, not a doctored one.

Reflecting telescopes have structures in the light path that produce spikes around bright stars. Usually we see four spikes, but occasionally six or eight. And other scopes with non-round apertures also produce spikes (e.g. camera lenses with vane irises). Those are the spikes you see in most astronomical images.

Occasionally an imager makes the (usually unfortunate, IMO) choice to actually add spikes to the bright stars during image editing. That appears to be the case in today's image, where the spikes rather bizarrely show the star color, and not normal diffraction patterns.

Astrophotographers can be very competitive, with each trying to achieve a smoother, more colorful, deeper image. It becomes less about astronomy and more about achieving an optimal aesthetic. Diffraction spikes can be beautiful and reveal the very nature of light itself. The point spread function of a particular instrument is like a fingerprint left by the light as it makes its way to the detector. I think it's a shame that so many people feel that human intervention is required to augment the beauty of nature itself by adding fake diffraction spikes. I think they're distracting. Apparently most people like them, though. I guess I can't fault them. It's only recently in my life that I even understand enough to realize what they are.

The title reminds me of song lyrics by the band TooL. 46 and 2 just ahead of you...

What is the ruddy rocky-looking sphere intermingled with the stars in the close-up? It looks like nothing else in the photo.

zendae wrote:What is the ruddy rocky-looking sphere intermingled with the stars in the close-up? It looks like nothing else in the photo.

It is the OTHER planetary Nebula...

:---[===] *

Absolutely fantastic image, the star colours are really vivid and the highlight of this particular image. I know of the smaller planetary nebula as M1-18 and very rarely use Perek Kohoutek (PK) designations for planetary nebulae.

Deep Ha exposures show an impressive double halo around NGC 2438 as well as revealing a third nebula in the region, the protoplanetary nebula OH 231.8 +4.2 better known as the Rotten Egg Nebula or the Calabash Nebula. This image by Adam Block shows everything in remarkable detail.

The only other major double halo is the one around the Ring Nebula but a few others have been discovered in the past 15 years. Some of these include the lesser known NGC 2867, IC 2165, Cn 1-5 and PB 4.

Also below are some of my favourite amateur images of PN haloes:

1. Dumbbell Nebula (M27) by Fabian Neyer and Robert Pölzl
2. Ring Nebula (M57) by Capella Observatory
3. Owl Nebula (M97) by Jason Jennings
4. Ghost of Jupiter Nebula (NGC 3242) by Wolfgang Promper
5. Saturn Nebula (NGC 7009) by CHART32
6. Helix Nebula (NGC 7293) by Capella Observatory
7. HDW 2 by Don Goldman
8. IC 5148 by Don Goldman
9. Hen 2-111 by Don Goldman
10. Abell 66 by Don Goldman