APOD: NGC 5643: Nearby Spiral Galaxy from... (2020 Oct 05)

[APOD Robot]

NGC 5643: Nearby Spiral Galaxy from Hubble

Explanation: What's happening at the center of spiral galaxy NGC 5643? A swirling disk of stars and gas, NGC 5643's appearance is dominated by blue spiral arms and brown dust, as shown in the featured image taken by the Hubble Space Telescope. The core of this active galaxy glows brightly in radio waves and X-rays where twin jets have been found. An unusual central glow makes NGC 5643 one of the closest examples of the Seyfert class of galaxies, where vast amounts of glowing gas are thought to be falling into a central massive black hole. NGC 5643, is a relatively close 55 million light years away, spans about 100 thousand light years across, and can be seen with a small telescope towards the constellation of the Wolf (Lupus).

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[Ann]

The caption of this APOD appears to be totally mixed up!

APOD Robot wrote:
A swirling disk of stars and gas, NGC 5643's appearance is dominated by blue spiral arms and brown dust, as shown in the featured image taken by the Hubble Space Telescope. The core of this active galaxy glows brightly in radio waves and X-rays where twin jets have been found. An unusual central glow makes M106 one of the closest examples of the Seyfert class of galaxies, where vast amounts of glowing gas are thought to be falling into a central massive black hole.

NGC 5643. Photo: ESA/Hubble & NASA, A. Riess et al.; Acknowledgement: Mahdi Zamani

---

M106. Image Credit: X-ray - NASA / CXC / Caltech / P.Ogle et al.
Optical - NASA/STScI, IR - NASA/JPL-Caltech, Radio - NSF/NRAO/VLA

NGC 5643 and M106 are two different galaxies! They are not the same at all!

Ann

[XgeoX]

I don’t believe it is mistaken it refers to m106 as being “ one of the closest examples of the Seyfert class of galaxies”. It then refers to ngc5643 as being “ a relatively close 55 million light years away” Seyfert class of galaxy and it is about twice as far.
Clumsy writing but it is definitely referring to two different objects.

[Ann]

I don’t believe it is mistaken it refers to m106 as being “ one of the closest examples of the Seyfert class of galaxies”. It then refers to ngc5643 as being “ a relatively close 55 million light years away” Seyfert class of galaxy and it is about twice as far.
Clumsy writing but it is definitely referring to two different objects.

All right, XgeoX. In that case, I suggest a different wording of the caption, maybe something like this:

What's happening at the center of spiral galaxy NGC 5643? A swirling disk of stars and gas, NGC 5643's appearance is dominated by blue spiral arms and brown dust, as shown in the featured image taken by the Hubble Space Telescope. The core of this active galaxy glows brightly in radio waves and X-rays where twin jets have been found. Because of this activity in its center, NGC 5643 has been classified as a Seyfert galaxy. A more well-known example of a Seyfert galaxy is M106, whose relatively nearby location makes it one of the closest examples of this class of galaxies.

Ann

[orin stepanek]

Nice Photo from Hubble!

[RJN]

NGC 5643 and M106 are two different galaxies! They are not the same at all!

Yes, my bad. I did not mean to reference M106 like that. Thanks for catching that and alerting us! It has now been fixed on the main NASA APOD. I apologize for the oversight.
- RJN

[BaldEagle]

The foreground bright blue stars are well explained elsewhere, but I've got a question about the background to them. There is a blue haze behind them.
Is that misty blue haze made up of other stars in that galaxy?
Thanks for answering this newbe's question.

[DL MARTIN]

First, Ann thanks for clarifying things. Second, One can always learn from mistakes. By searching Seyfert galaxies, I learned stuff I didn't know but I'm still not gainng on Chris Peterson.

[TheZuke!]

It looks like to me that the core of galaxy has tipped edgewise to us.

[Phobos1]

Where the diffraction spikes on foreground stars enhanced on this image? They look really strong when compared to this Hubble photo of NGC 5643 at Wikipedia: https://upload.wikimedia.org/wikipedia/ ... C_5643.png

[bystander]

Where the diffraction spikes on foreground stars enhanced on this image? They look really strong when compared to this Hubble photo of NGC 5643 at Wikipedia: https://upload.wikimedia.org/wikipedia/ ... C_5643.png

I believe it's the same image data, just different processing. The one on wiki is geckzilla's. The APOD is from ESA/Hubble.

[geckzilla]

Where the diffraction spikes on foreground stars enhanced on this image? They look really strong when compared to this Hubble photo of NGC 5643 at Wikipedia: https://upload.wikimedia.org/wikipedia/ ... C_5643.png

Just new and multiple sets of data used. The telescope nearly always points at a different angle when viewing objects at separate "visits" (each time it looks at an object is called a visit) and the result is diffraction spikes at all different angles.

[orin stepanek]

I think it"s a Red Star!

[Ann]

NGC5643_HubbleZamani_960.jpg

I think it"s a Red Star!

I'd say it's a galaxy.

Background galaxy in NGC 5643.

NGC 1532 and 1531. Photo: Gemini Observatory.

---

Compare the elongated reddish shape in NGC 5643 with the appearance of large edge-on spiral galaxy NGC 1532. You can see that both the reddish object in NGC 5643 and NGC 1532 have small bright central points of light surrounded by small bright elongated shapes. In the case of NGC 1532, the inner objects are the nucleus and the inner bulge. In my opinion, the central bright and elongated area of the red object in NGC 5643 is also a galactic nucleus and inner bulge.

Below the inner bulge of NGC 1532, we can see two prominent dust lanes. Note that we can see clear hints of similar dust lanes in the red object in NGC 5643.

Note that there is a whitish object near the red object in NGC 5643. The white object also looks like a galaxy. But if that is what it is, why are the two galaxies such different colors?

I'd say that the red object (make that the red galaxy) is heavily reddened by dust in NGC 5643. Note that there appear to be thick foreground dust lanes in the general area of the red galaxy, but there appears to be no dust at all in front of the white galaxy.

The red galaxy may also be self-reddened by its own dust. It does appear to be dusty, whereas the white galaxy may be mostly dust-free.

Ann

[ta152h0]

I didn't know there was a Wolf constellation? Is there a Kathy constellation nearby? I know there's wolf-rayett stars. pass the ice cold one

[BillBixby]

First, Ann thanks for clarifying things. Second, One can always learn from mistakes. By searching Seyfert galaxies, I learned stuff I didn't know but I'm still not gaining on Chris Peterson.

We likely will not see anyone cross the finish line. Rather than a dash, this is a relay race. The first to notice and think about the heavens passed the baton of knowledge on to another and others. They, to still others. Chris is running to pass the baton to his students, you and us. Neffer is running in another lane with his baton and at the same time egging on and also encouraging Chris. Geekzilla is in yet another lane of the relay event. Lots if lanes with lots of runners and the lead keeps changing. I feel lucky to be able to watch this event or these events on APOD.

[orin stepanek]

NGC5643_HubbleZamani_960.jpg

I think it"s a Red Star!

I'd say it's a galaxy.

Background galaxy NGC 5643.png

Background galaxy in NGC 5643.

NGC 1532 and 1531. Photo: Gemini Observatory.

---

Compare the elongated reddish shape in NGC 5643 with the appearance of large edge-on spiral galaxy NGC 1532. You can see that both the reddish object in NGC 5643 and NGC 1532 have small bright central points of light surrounded by small bright elongated shapes. In the case of NGC 1532, the inner objects are the nucleus and the inner bulge. In my opinion, the central bright and elongated area of the red object in NGC 5643 is also a galactic nucleus and inner bulge.

Below the inner bulge of NGC 1532, we can see two prominent dust lanes. Note that we can see clear hints of similar dust lanes in the red object in NGC 5643.

Note that there is a whitish object near the red object in NGC 5643. The white object also looks like a galaxy. But if that is what it is, why are the two galaxies such different colors?

I'd say that the red object (make that the red galaxy) is heavily reddened by dust in NGC 5643. Note that there appear to be thick foreground dust lanes in the general area of the red galaxy, but there appears to be no dust at all in front of the white galaxy.

The red galaxy may also be self-reddened by its own dust. It does appear to be dusty, whereas the white galaxy may be mostly dust-free.

Ann

Thanks Ann; I was thinking Star because I think red galaxies are {IMO) rare; and looked like a pretty dusty area! I was aware of the white Galaxy but didn't Question it! I really like today's APOD; Pretty neat!

[heehaw]

Aw, you seen one Galaxy, you seenem all. Just angular momentum doing its thing. BORING!

[Chris Peterson]

Thanks Ann; I was thinking Star because I think red galaxies are {IMO) rare; and looked like a pretty dusty area! I was aware of the white Galaxy but didn't Question it! 8-) I really like today's APOD; Pretty neat! 8-)

I wouldn't take the colors too seriously. This is still constructed from data ranging from blue to IR. And given the position of the red galaxy, it's likely the light has had its shorter wavelengths attenuated by dust.

[orin stepanek]

Thanks Ann; I was thinking Star because I think red galaxies are {IMO) rare; and looked like a pretty dusty area! I was aware of the white Galaxy but didn't Question it! I really like today's APOD; Pretty neat!

I wouldn't take the colors too seriously. This is still constructed from data ranging from blue to IR. And given the position of the red galaxy, it's likely the light has had its shorter wavelengths attenuated by dust.

[rj rl]

I have a question: in galaxy pictures with this kind of resolution, can we see their globular clusters and if so, how do I tell one from a dimmer foreground star from our galaxy?

[Ann]

Thanks Ann; I was thinking Star because I think red galaxies are {IMO) rare; and looked like a pretty dusty area! I was aware of the white Galaxy but didn't Question it! I really like today's APOD; Pretty neat!

Absolutely right, Orin, you can say that red galaxies don't exist! But they can look right for two reasons.

1) Galaxies can look red because there is a lot of dust in front of them, so we see them through a curtain of dust. The dust in front of it filters away the short wavelengths of light (i.e., violet, blue, green) that were emitted by that galaxy, making it look yellow, orange or even red. (Or it may in fact become invisible in optical light, because if there is enough dust in front of the galaxy, not even the galaxy's reddest light can penetrate the dust.)

2) Galaxies can look red because they are very far away, and the light they emitted has literally been "stretched" by the expansion of the Universe. If the galaxy itself looked "white", all the light that the galaxy emitted has been stretched to longer, redder colors. Because as you know, longer wavelengths are redder and shorter wavelengths are bluer. Again, if the galaxy is sufficiently far away, it becomes invisible in optical light, because even its bluest light becomes stretched to infrared wavelengths.

(Amazingly though, some distant background galaxies look blue. Such galaxies are chock full of intensely hot massive stars, which emit copious amounts of far-ultraviolet light. When the light of these galaxies reaches the Earth, the far ultraviolet light has been redshifted to optical violet, blue and green. However, if these starbursting galaxies are sufficiently far away, their light too will be stretched first to red and then to invisible infrared light.)

Dust-reddened dwarf galaxy IC 10. It is reddened by dust in the Milky Way, because we see it behind a lot of stars and dust in Cassiopeia. Photo: Mark Hanson.

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Redshifted background galaxies behind the Tadpole Galaxy. The background
galaxies look red because their light has been "stretched" by the expansion of
the Universe. Photo: NASA, H. Ford (JHU), G. Illingworth (USCS/LO),
M. Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

So red galaxies don't exist, but they can look red anyway!

Ann

[geckzilla]

I have a question: in galaxy pictures with this kind of resolution, can we see their globular clusters and if so, how do I tell one from a dimmer foreground star from our galaxy?

You can see them, and they look a lot softer than a MW star and lack diffraction spikes. They'll usually be lumpy, too. It's easier to differentiate them if the processing is less contrasty. There's one at the very top edge almost right in the center. It looks a little bit yellowish.

[Phobos1]

....
Just new and multiple sets of data used. The telescope nearly always points at a different angle when viewing objects at separate "visits" (each time it looks at an object is called a visit) and the result is diffraction spikes at all different angles.

It had me wondering just how many vanes they had holding up the secondary on Hubble. -Turns out to be four. Through here: https://astronomy.stackexchange.com/que ... ultiple-di

[rj rl]

I have a question: in galaxy pictures with this kind of resolution, can we see their globular clusters and if so, how do I tell one from a dimmer foreground star from our galaxy?

You can see them, and they look a lot softer than a MW star and lack diffraction spikes. They'll usually be lumpy, too. It's easier to differentiate them if the processing is less contrasty. There's one at the very top edge almost right in the center. It looks a little bit yellowish.

I guess I see it, but I'd never pick it up myself