Celestia Forums

I just noticed that the MilkyWay representation is reversed !
The red-yellow squares on the picture below represents pulsars density. We can clearly see some parts of the galactic arms, and they look like reversed, compared to the MilkyWay template. Fridger ?

where does that map come from? Looks a bit interesting.

Though I'm not sure I can tell if they match any particular orientation of spiral arm...

That map comes from Selden, on my request (old addon but very secure stuff). I'm interested in Pulsars since a very long time ago. So Selden compiled a database of 1500 pulsars and can be found on his web site. It's simply the complete list of the pulsar database, from ATNF Pulsar Catalog v1.2 at http://www.atnf.csiro.au/research/pulsar/psrcat/

The pulsars distribution is a good indicator of the galactic shape.

Oh MY !

I simply reversed the MilkyWay.png template, and now the pulsars distribution match perfectly the template !! This is GREAT ! See the picture below :

Cham,

I actually know about the MilkyWay reversal since quite a while and
have announced it's fix elsewhere. We have designed it in correct
orientation, but at some stage of image manipulation it must have
gotten reversed /accidentally/.

http://www.celestiaproject.net/forum/viewtopic ... ight=milky

and my fix announcement

http://www.celestiaproject.net/forum/viewtopic.php?t=10329

The Milky way fits well because we accounted for ALL existing scientific
info about its arms in the custom template . The pulsar
cross-check IS interesting, though.

Bye Fridger

PS: Also each arm is identified and e.g. labelled in this (correctly
oriented image of our template) . Probably it would be good if I release
a corresponding "location" file!

Cham wrote:Oh MY !

I simply reversed the MilkyWay.png template, and now the pulsars distribution match perfectly the template !!

Yep, this is pretty cool...

Cham wrote:Oh MY !

I simply reversed the MilkyWay.png template, and now the pulsars distribution match perfectly the template !! This is GREAT !

Oh yeah, actually I can see the fit a lot better there too. Nice!

Wow . . . the pulsar map is cool! Nice work on that and the Milky Way template!

--Chris

I probably should think about updating the Addon. Hopefully more pulsars are included in the database now than when I first created it.

If you look closely, you'll notice that there are very few pulsars shown in the Perseus arm outward from the position of the Sun. I suspect that's an observational effect due to very few searches having been done in the direction opposite from the galactic center.

selden wrote:I probably should think about updating the Addon. Hopefully more pulsars are included in the database now than when I first created it.

If you look closely, you'll notice that there are very few pulsars shown in the Perseus arm outward from the position of the Sun. I suspect that's an observational effect due to very few searches having been done in the direction opposite from the galactic center.

Selden,

writing a PERL extraction script for the Pulsars would be very little work for me, given this well-organized catalog. I might add all sorts of interesting info as well.

The advantage is that PERL scripts serve as a handy human readable documentation of our data in the Celestia source distribution.

Bye Fridger

Fridger,

If you think the catalog of pulsars is an appropriate addition to Celestia, that'd be great!

The Addon includes CEL scripts that mark the pulsars with different colors depending on various characteristics. The picture Cham posted above shows marks that have their colors determined from the local density of pulsars: red = low density, yellow = medium, white = max, with a linear scale between them. Other scripts set colors determined by their periods and other characteristics that I've long since forgotten. Would you be able to include something like that?

selden wrote:Fridger,
If you think the catalog of pulsars is an appropriate
addition to Celestia, that'd be great!

The Addon includes CEL scripts that mark the pulsars
with different colors depending on various
characteristics. The picture Cham posted above shows
marks that have their colors determined from the local
density of pulsars: red = low density, yellow = medium,
white = max, with a linear scale between them. Other
scripts set colors determined by their periods and other
characteristics that I've long since forgotten. Would you
be able to include something like that?

Selden,

I just downloaded and checked your add-on against my
latest MilkyWay template, which is really impressive.

Here is my version:


Another interesting aspect is that there are many pulsars
to be found in arc-type arrangements much further out
than the rim of our template. This again matches
perfectly with this interesting paper (that you also know)


by E.S. Levine and friends,
http://arxiv.org/pdf/astro-ph/0605728

Here the outer spiral structure of the MilkyWay is
inferred from a map of the perturbed surface density of
neutral hydrogen! These data indicate that our Milkyway
is about a factor of two larger in size than what was
commonly thought.

I think we should update the catalog to the FULL present
set of pulsars and make a regular catalog for the
distribution. It's great stuff, indeed.

Since I would of course extract all relevant pulsar data
along with names and coordinates, we could always
discuss how they are best marked or displayed.

Bye Fridger

To give people an idea, I pulled out a composite image
ElChristou made this summer by combining the NASA
artist image with those new hydrogen data from Levine et
al. One can see how much larger the arms seem to
extend. We might play further with this and have a look
whether thepulsars at larger distances fit onto the
best-fitted arms in the hydrogen data!?

Bye Fridger

t00fri wrote:...These data indicate that our Milkyway
is about a factor of two larger in size than what was
commonly thought...

Yep, I'm still thinking we should update the size of the MW to match those datas...

ElChristou wrote:

t00fri wrote:...These data
indicate that our Milkyway is about a factor of two larger
in size than what was commonly thought...

Yep, I'm still thinking we should update the size of the
MW to match those datas...

ElChristou,

that's not all that simple:

Illustration:

almost every galaxy is about a factor of 2 bigger than it
looks like in a visual telescope. The reason is dark
matter that cannot be perceived visually.

In the same sense the present evidence for additional
MilkyWay arm structure via neutral hydrogen is visually
not apparent. So increasing the size correspondingly,
would violate our basic rule of the game that Celestia
pictures things essentially in visual light...

Of course my personal taste is way more general.
I would have long started to implement wavelength
"switches/filters". Then we could include those great
RGB colored infrared images of Titan, Saturn and many
other objects, for example.

Bye Fridger

t00fri wrote:

ElChristou wrote:

t00fri wrote:...These data
indicate that our Milkyway is about a factor of two larger
in size than what was commonly thought...

Yep, I'm still thinking we should update the size of the
MW to match those datas...

ElChristou,

that's not all that simple:

Illustration:

almost every galaxy is about a factor of 2 bigger than it
looks like in a visual telescope. The reason is dark
matter that cannot be perceived visually.

In the same sense the present evidence for additional
MilkyWay arm structure via neutral hydrogen is visually
not apparent. So increasing the size correspondingly,
would violate our basic rule of the game that Celestia
pictures things essentially in visual light...

Tx for the clarification!

t00fri wrote:Of course my personal taste is way more general.
I would have long started to implement wavelength
"switches/filters". Then we could include those great
RGB colored infrared images of Titan, Saturn and many
other objects, for example.

I completely agree of course...