Galactic centre (APOD 2009/11/11)

[Axel]

I don't understand the relationship between North and East in the "complementary annotated image." Is it just an ordinary optical inversion? I thought these things were corrected as a matter of course.

[neufer]

<<Of course, a telescope's magnification and light gathering ability creates
only an image of what a human could see if visiting these places.>>

Of course, what a "naked ape" might see visiting by these places might well prove to be
a poor substitute for what telescopes can already detect over a broad spectral range.

[Qev]

If you're standing facing north, and look down at the ground, north is at the 'top' of your field of view, and east is to your right. Now if you look straight up at the sky (still facing north), north is now at the 'bottom' of your field of view, with east still to your right. If you wanted to correct to have north at the 'top' again, you'd have to rotate 180 degrees, which would put east to your left. So in photos of the sky, since we put north (typically) at the top, east and west end up seeming reversed, no inversion necessary.

Er... I hope I said that right. < <

[Chris Peterson]

I don't understand the relationship between North and East in the "complementary annotated image." Is it just an ordinary optical inversion? I thought these things were corrected as a matter of course.

The cardinal directions used on the sky are aligned with those on Earth. But on Earth, we see them on the outside of a sphere, whereas on the sky we are seeing them projected on the inside of a sphere. So from our viewpoint, the directions on the sky (above us) are mirrored from those on the Earth (below us).

An image of the sky that is not mirrored or inverted by the optics will have north up, east left (or possibly a rotation of that). That's how star maps are drawn, as well, since you use them while looking up. Lie on your back with your head to the north, and you'll notice that east is to your left.

[zbvhs]

To reach the Galactic Center we're going to need much more than rockets. If Prof. Einstein is correct, however, we will probably not get much further than Jupiter.

[Chris Peterson]

To reach the Galactic Center we're going to need much more than rockets. If Prof. Einstein is correct, however, we will probably not get much further than Jupiter.

Rockets will do the job. It just takes a while. But that's true for any propulsion technology. (The reality is that we're not going to ever visit the center of the galaxy.)

But there's no reason we can't completely explore our own system, and reach some of the nearer stars. That doesn't require any sort of extraordinary advancement in technology, nor does it require lengths of time that are unreasonable.

[Martin]

Great image! What type of star appear green?

Does the little bubble type object to the right of Sagittarius A. have a name?

[peter_from_nyc]

This is what I wanted: an annotated version of the photo.
Thanks!
I requested it a few months ago in Sep2009:

I'm about 60 years old, and with 2 MIT degrees. I love reading APOD every day.

But sometimes, I can NOT figure out what you guys are pointing at.

Is there some way, even a wikipedia type way, that someone can annotate the stars?

E.g. with the "The Center of Globular Cluster Omega Centauri " of 2009 September 14
someone could point to the red stars, the blue stars, the binary stars.

Yeah I can see the difference between red and blue. But wouldn't it be cool (pun intended) to circle the binary stars? Or number them?

This is a bit conceited, but here it goes: if I can't tell the difference, there are probably thousands of people who can't.

Peter

http://asterisk.apod.com/vie ... =9&t=17353

[neufer]

To reach the Galactic Center we're going to need much more than rockets. If Prof. Einstein is correct, however, we will probably not get much further than Jupiter.

Rockets will do the job. It just takes a while. But that's true for any propulsion technology. (The reality is that we're not going to ever visit the center of the galaxy.) But there's no reason we can't completely explore our own system, and reach some of the nearer stars. That doesn't require any sort of extraordinary advancement in technology, nor does it require lengths of time that are unreasonable.

http://www.youtube.com/watch?v=PdgHvuCEWnE
http://www.youtube.com/watch?v=wtIpcwLjRs4

Disney's Mars & Beyond:
http://www.youtube.com/watch?v=1r99XcaYDjg
http://www.youtube.com/watch?v=MxQVaHbqvTI
http://www.youtube.com/watch?v=x7RYYVm2o9s
http://www.youtube.com/watch?v=RChnjIKWges
http://www.youtube.com/watch?v=d76fiWRobU4
http://www.youtube.com/watch?v=FRCQ2Cu3bSE

[Osmo]

Close to the centre of the picture in the left bottom quadrant there is interesting "Saturn-like" object. The picture must be zoomed strongly to find this. What is it?

[neufer]

<<Tardigrades (commonly known as water bears or moss piglets) are microscopic, water-dwelling, segmented animals with eight legs. Tardigrades were first described by Johann August Ephraim Goeze in 1773 (kleiner Wasserbär = little water bear). The name Tardigrada means "slow walker" and was given by Lazzaro Spallanzani in 1777. The name water bear comes from the way they walk, reminiscent of a bear's gait. The biggest adults may reach a body length of 1.5 mm, the smallest below 0.1 mm.

More than 1000 species of tardigrades have been described. Tardigrades occur over the entire world, from the high Himalayas (above 6,000 m), to the deep sea (below 4,000 m) and from the polar regions to the equator. The most convenient place to find tardigrades is on lichens and mosses. Other environments are dunes, beaches, soil, and marine or freshwater sediments, where they may occur quite frequently (up to 25,000 animals per litre). Tardigrades often can be found by soaking a piece of moss in spring water.

Tardigrades are polyextremophiles; scientists have reported their existence in hot springs, on top of the Himalayas, under layers of solid ice and in ocean sediments. Some can survive temperatures of -273°C, close to absolute zero, temperatures as high as 151 °C (303 °F), 1,000 times more radiation than other animals such as humans, more than a century without water, and even the vacuum of space.

In September 2007, tardigrades were taken into low Earth orbit on the FOTON-M3 mission and for 10 days were exposed to the vacuum of space. After they were returned to Earth, it was discovered that many of them survived and laid eggs that hatched normally, making these the only animals shown to be able to survive the vacuum of space.>>

[kjardine]

Close to the centre of the picture in the left bottom quadrant there is interesting "Saturn-like" object. The picture must be zoomed strongly to find this. What is it?

Hi Osmo,

I've also wondered that. This object is visible in this Hubble infrared image, which is where I first spotted it myself a few months ago.

A SIMBAD search around the location brings up this rather long list of possibilities.

My guess from the look of it is that this is a large dust disk surrounding a star that may be much closer than the galactic centre but happens to be in that direction. But I'm not sure!

Cheers,
Kevin

Kevin Jardine
Galaxy Map
http://galaxymap.org

[Axel]

Thanks to Qev and Chris for their responses to my OP. Now this is the way I see it. If there is a reference plane parallel to the image plane and located between us (i.e. the image on our screens) and the galactic centre, and if a person floating near the galactic centre is looking towards us with his or her body parallel to the reference N-S line and with head pointing north, then that person's "east" will be on his/her right-hand side, which to us will be the left-hand side. So far so good. But more questions arise in my mind. Why, in order to understand the direction pointers on this image, must I assume (a) that some presumed observer at the image object location is not facing the same way I am, and/or (b) that the reference plane on which the directions NESW are "inscribed", as it were, is not simply my reference plane (with east on the right) translated to the image object location?

This must have been debated before but I truly am puzzled. I hope this doesn't come across as trolling.

[apodman]

I hope this doesn't come across as trolling.

Don't worry. You have to drink the special water to become a troll. Only individuals with true troll potential ever find the fountain.

It takes repeated angling of the neck and sweeping of the arms while viewing or imagining the sky to get the hang of the orientation and motions of what's above. It takes practice to look at an unlabeled sky and see grid lines.

[Chris Peterson]

Now this is the way I see it. If there is a reference plane parallel to the image plane and located between us (i.e. the image on our screens) and the galactic centre, and if a person floating near the galactic centre is looking towards us with his or her body parallel to the reference N-S line and with head pointing north, then that person's "east" will be on his/her right-hand side, which to us will be the left-hand side.

I think you are asking for trouble in two ways here: by talking about "planes", and by changing the position of the observer. The position of an object on the sky is described by 2D spherical coordinates. It is a necessarily geocentric (or heliocentric) coordinate system. And a planar image is actually a projection, and only approximates the actual object when the FOV is small- just like maps of the Earth's surface. It is pretty meaningless to try and assign what we would call "east" to what an observer would see from some other location in the galaxy.

Although the spherical coordinate system used for the sky is related to the Earth's coordinate system (their poles lie on the same line), you might do better forgetting about Earth completely and just picturing a spherical grid on the sky, with coordinates measured in declination (equivalent to latitude on the Earth) measured from +90° at the north celestial pole, to 0° at the celestial equator, to -90° at the south celestial pole, and in right ascension (equivalent to longitude on Earth), with a fixed, arbitrary zero (equivalent to longitude 0° on Earth at a specific time) and increasing through 360° clockwise around the north celestial pole. "East" is the direction that right ascension increases, and isn't necessarily the same everywhere in an image. If you take a picture of the sky around the North Star, for instance, "east" is clockwise: typically to the left below Polaris and to the right above it.

When you look at an annotated image like the one under discussion, don't try too hard (or at all) to relate the directions to your local horizon on Earth. The "north" arrow is just telling you the direction that declination increases, and the "east" arrow is telling you the direction that right ascension increases.

[Martin]

Great image! What type of star appear green?

Does the little bubble type object to the right of Sagittarius A. have a name?

[kjardine]

Hi Martin,

This is a false colour image using X-ray and infrared data that our eyes can not see.

The green stars are X-ray sources emitting in the 3-5 keV energy range.

I don't see a "little bubble type object to the right of Sagittarius A".

You can see Sagittarius A here. If you look at the black box at the bottom of that page, you can get a read out of galactic coordinates. What are the coordinates for the "little bubble type object" you mention?

Kevin

Kevin Jardine
Galaxy Map
http://galaxymap.org

[SittingDownMan]

Re: Galactic centre (APOD 2009/11/11)
by kjardine on Fri Nov 13, 2009 6:33 am
Hi Martin,

This is a false colour image using X-ray and infrared data that our eyes can not see.

The green stars are X-ray sources emitting in the 3-5 keV energy range.

I don't see a "little bubble type object to the right of Sagittarius A".

You can see Sagittarius A here. If you look at the black box at the bottom of that page, you can get a read out of galactic coordinates. What are the coordinates for the "little bubble type object" you mention?

Kevin

Kevin Jardine
Galaxy Map
http://galaxymap.org

Hey, thanks, that is well cool.
I suspect the OP is talking about 0.0961 by -0.0502 which looks like either a distant galaxy or a dusty cloud.
Or maybe an oncoming barely-sub-planet-sized warship of the Galactic Overlord's Fleet.
On the APOD picture, there's a star in the lower left with a smoke ring, to the right of that is a triangle of red
blobbies, just to the right and up a bit of the rightmost red blobby is the thing that looks like Saturn as seen
through Mr. Galilei's early scope.
On the cool Hubbley/Spitzer map thingy it looks even more saturnian.
SDM :>

[Martin]

Here is a close up from the Apod image. Scroll to right.

Close up of Sagittarius A

Object.jpg (100.41 KiB) Viewed 8938 times

There are many facinating objects to view in this APOD image but this one seemed different.

[SittingDownMan]

Here is a close up from the Apod image.

Object.jpg

Oh. Sorry.
That looks very like a flaw. An image artifact. Dust on the lens.
It doesn't look real.
'Course I could be mistaken.
SDM.

[SittingDownMan]

Here is a close up from the Apod image.

The attachment Object.jpg is no longer available

Oh. Sorry.
That looks very like a flaw. An image artifact. Dust on the lens.
It doesn't look real.
'Course I could be mistaken.
SDM.

This is what I thought Martin was talking about.
Sorry for the poor quality, I only have MSPaint to work with.

crop1.JPG (82.37 KiB) Viewed 8913 times

[kjardine]

Here is a close up from the Apod image. Scroll to right.

I've now put this NASA composite image in the Milky Way Explorer, and you can see the object/artifact mentioned by Martin here.

This is a bit of a puzzle because this composite image is supposedly constructed from three previously released NASA images. However, the fuzzy object Martin mentions does not appear on either the original Spitzer or Chandra images and is completely outside the boundary of the original Hubble image.

So where did it come from? Spooky.

Cheers,
Kevin

Kevin Jardine
Galaxy Map
http://galaxymap.org

[Martin]

Thank you for responding to my question. What is it? Perhaps, after more people have viewed it someone will know what it is.

http://asterisk.apod.com/vie ... 27#p112127

[Martin]

Does anyone know?

http://asterisk.apod.com/vie ... 27#p112127

[kjardine]

Martin, I haven't given up on this yet.

Your fuzzy object is also visible here:

http://hubblesite.org/gallery/album/pr2009002b

so we know that the data was collected by Hubble's NICMOS instrument. It is definitely not visible in the Spitzer or Chandra data. It doesn't look like an artifact to me. I think that it might be a real object visible in near-infrared and am trying to get more accurate coordinates.

UPDATE: Looks like this is an artifact after all, as explained in my next post.

Kevin

Kevin Jardine
Galaxy Map
http://galaxymap.org