APOD: Peculiar Galaxies of Arp 273 (2022 Feb 19)

[APOD Robot]

Peculiar Galaxies of Arp 273

Explanation: The spiky stars in the foreground of this backyard telescopic frame are well within our own Milky Way Galaxy. But the two eye-catching galaxies lie far beyond the Milky Way, at a distance of over 300 million light-years. Their distorted appearance is due to gravitational tides as the pair engage in close encounters. Cataloged as Arp 273 (also as UGC 1810), the galaxies do look peculiar, but interacting galaxies are now understood to be common in the universe. Nearby, the large spiral Andromeda Galaxy is known to be some 2 million light-years away and approaching the Milky Way. The peculiar galaxies of Arp 273 may offer an analog of their far future encounter. Repeated galaxy encounters on a cosmic timescale can ultimately result in a merger into a single galaxy of stars. From our perspective, the bright cores of the Arp 273 galaxies are separated by only a little over 100,000 light-years.

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[VictorBorun]

"the bright cores"
There are just two galactic cores, are not they?

[Ann]

"the bright cores"
There are just two galactic cores, are not they?

Click to view full size image

In the APOD, that yellow blob to the right of the core of the main galaxy (UGC 1810) sure looks like another core.

This Hubble Space Telescope image shows a group of interacting galaxies called Arp 273. Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

---

But you're right, it's not a core. The Hubble image above demonstrates that the orange light to the right of the core of UGC 1810 is just a foreground star with diffraction spikes.

Note the mini-spiral in the arm of UGC 1810 at upper right.

Ann

[XgeoX]

Hi,
Does anybody know if that beautiful bright golden star to the left in the photo is H14511?
Thanks!

Eric

[orin stepanek]

Probably a good prediction of what Sol and it's planetary system will
have to endure a few billion years from now. I can hardly wait!
Very beautiful Photo! Kudos to the photographer!

[E Fish]

"the bright cores"
There are just two galactic cores, are not they?
Arp 273.png

That is exactly what I was going to ask. I'm glad that it's already been asked and answered! That's a beautiful image today.

So in the two pictures that Ann provided, it seems obvious that the other blob was actually a foreground star. Does anyone know what was done differently with the processing to change its appearance so much in today's APOD?

[Case]

In the circle (top): Position of Arp 273 and HD 14511 on the sky.

---

Does anybody know if that beautiful bright golden star to the left in the photo is H14511?

HD 14511, yes. An 8.8 magnitude G5 star¹ at 444 parsec (1448 light-years) distance, as derived from Gaia data. (Previous estimates put it farther away.) [¹ thought to be a binary or multiple star system, but not visible as such in today’s image.]

[De58te]

Another APOD day and again I am confused by the explanation. It mainly describes the ARP 273 galaxies but it also says that nearby is the Andromeda galaxy. That must be the one in the top left corner because I don't see any other galaxies nearby. However it is said that the Andromeda is the most distant light that we can see with the naked eye. My question is if we can see the Andromeda galaxy by eye and yet the Arp 273 galaxies are at least 4 or 5 times larger than Andromeda in this photograph, then how come we can't see the Arp galaxies by naked eye?

[Ann]

Another APOD day and again I am confused by the explanation. It mainly describes the ARP 273 galaxies but it also says that nearby is the Andromeda galaxy. That must be the one in the top left corner because I don't see any other galaxies nearby. However it is said that the Andromeda is the most distant light that we can see with the naked eye. My question is if we can see the Andromeda galaxy by eye and yet the Arp 273 galaxies are at least 4 or 5 times larger than Andromeda in this photograph, then how come we can't see the Arp galaxies by naked eye?

The Andromeda galaxy is far, far closer and far, far brighter in the sky than Arp 273. You can see Andromeda with the naked eye, but absolutely not Arp 273.

Andromeda constellation with Andromeda galaxy (M31) and approximate
location of Arp 273. Photo: Jimmy Westlake.

The Andromeda galaxy and Arp 273 are both located in constellation Andromeda, but they are not close together in the sky. You can see the location of the Andromeda galaxy in Jimmy Westlake's photo. The white "X" marks the approximate spot where you find Arp 273.

Ann

[Ann]

"the bright cores"
There are just two galactic cores, are not they?
Arp 273.png

That is exactly what I was going to ask. I'm glad that it's already been asked and answered! That's a beautiful image today.

So in the two pictures that Ann provided, it seems obvious that the other blob was actually a foreground star. Does anyone know what was done differently with the processing to change its appearance so much in today's APOD?

This is not the sort of question you should ask me, but I'm sure that Arp 273 in today's APOD was not photographed by the Hubble telescope. Either an amateur telescope was used, or else a relatively small professional one. Therefore, the great difference between the Hubble image of Arp 273 and Jason Guenzel's image has less to do with the processing of the image and more to do with the data acquisition.

Ann

[Thirteen]

"the bright cores"
There are just two galactic cores, are not they?
Arp 273.png

That is exactly what I was going to ask. I'm glad that it's already been asked and answered! That's a beautiful image today.

So in the two pictures that Ann provided, it seems obvious that the other blob was actually a foreground star. Does anyone know what was done differently with the processing to change its appearance so much in today's APOD?

Original photographer here!

First, thanks so much to the APOD team for the consideration and feature. I'll try to address some of the questions regarding my image. First, in regards to the star that's been confused with another galactic core, the reason it looks so much different than the Hubble image is that this was shot with my rather modest 8" Celestron EdgeHD telescope. The combination of smaller optics and turbulent suburban skies conspires to blur the stars significantly. Though the results can't really compare to Hubble, I did have excellent (by my standards) conditions when photographing this, allowing me to extract impressive details (again by my standards). I hope you enjoyed it as much as I did.

If you want to read my original description and details about the gear, you can find it here...
https://www.instagram.com/p/CZ-YkhsJQWE ... _copy_link

[Thirteen]

Another APOD day and again I am confused by the explanation. It mainly describes the ARP 273 galaxies but it also says that nearby is the Andromeda galaxy. That must be the one in the top left corner because I don't see any other galaxies nearby. However it is said that the Andromeda is the most distant light that we can see with the naked eye. My question is if we can see the Andromeda galaxy by eye and yet the Arp 273 galaxies are at least 4 or 5 times larger than Andromeda in this photograph, then how come we can't see the Arp galaxies by naked eye?

The Andromeda Galaxy is not in this frame, in fact it is enormous in our skies compared to this pair. The APOD image is cropped down to about 10% of my original frame shot at almost 1500mm of focal length. It would take me over 20 panels of mosaic coverage to frame the Andromeda Galaxy!

[E Fish]

Original photographer here!

First, thanks so much to the APOD team for the consideration and feature. I'll try to address some of the questions regarding my image. First, in regards to the star that's been confused with another galactic core, the reason it looks so much different than the Hubble image is that this was shot with my rather modest 8" Celestron EdgeHD telescope. The combination of smaller optics and turbulent suburban skies conspires to blur the stars significantly. Though the results can't really compare to Hubble, I did have excellent (by my standards) conditions when photographing this, allowing me to extract impressive details (again by my standards). I hope you enjoyed it as much as I did.

If you want to read my original description and details about the gear, you can find it here...
https://www.instagram.com/p/CZ-YkhsJQWE ... _copy_link

Thanks so much for the explanation! I knew it wasn't a Hubble image, but you had excellent details in your image and it definitely is beautiful. The reason I was wondering was because there were other stars with diffraction spikes in your image but that one didn't have them which was why it was harder to determine its nature.

[Chris Peterson]

Original photographer here!

First, thanks so much to the APOD team for the consideration and feature. I'll try to address some of the questions regarding my image. First, in regards to the star that's been confused with another galactic core, the reason it looks so much different than the Hubble image is that this was shot with my rather modest 8" Celestron EdgeHD telescope. The combination of smaller optics and turbulent suburban skies conspires to blur the stars significantly. Though the results can't really compare to Hubble, I did have excellent (by my standards) conditions when photographing this, allowing me to extract impressive details (again by my standards). I hope you enjoyed it as much as I did.

If you want to read my original description and details about the gear, you can find it here...
https://www.instagram.com/p/CZ-YkhsJQWE ... _copy_link

Thanks so much for the explanation! I knew it wasn't a Hubble image, but you had excellent details in your image and it definitely is beautiful. The reason I was wondering was because there were other stars with diffraction spikes in your image but that one didn't have them which was why it was harder to determine its nature.

It looks to me like the diffraction spikes were added for aesthetic reasons, and are not in the actual data.

[VictorBorun]

Note the mini-spiral in the arm of UGC 1810 at upper right.

Seems embedded or piercing all right!
If we rotate Hubble's pic by 8.5° counter-clockwise as to make the North direct to the observer and then stretch a little,
we can see the central planar part of UGC 1810 (unlike the whole 3D rose button made tidally) as perfectly round.
And the third galaxy, a spiral dwarf, is clearly meddling with an arm.

What I don't get is why they say that the stem of the flower-like composition, UGC 1813, is the one that actually passed through the larger one.
If the space were empty there would be no way to tell which one is standing still and which one is passing.
Now there may be some ram pressure for some galaxies to make the difference, but is there any for Arp 273 flower-like system?

[johnnydeep]

Original photographer here!

First, thanks so much to the APOD team for the consideration and feature. I'll try to address some of the questions regarding my image. First, in regards to the star that's been confused with another galactic core, the reason it looks so much different than the Hubble image is that this was shot with my rather modest 8" Celestron EdgeHD telescope. The combination of smaller optics and turbulent suburban skies conspires to blur the stars significantly. Though the results can't really compare to Hubble, I did have excellent (by my standards) conditions when photographing this, allowing me to extract impressive details (again by my standards). I hope you enjoyed it as much as I did.

If you want to read my original description and details about the gear, you can find it here...
https://www.instagram.com/p/CZ-YkhsJQWE ... _copy_link

Thanks so much for the explanation! I knew it wasn't a Hubble image, but you had excellent details in your image and it definitely is beautiful. The reason I was wondering was because there were other stars with diffraction spikes in your image but that one didn't have them which was why it was harder to determine its nature.

It looks to me like the diffraction spikes were added for aesthetic reasons, and are not in the actual data.

How did you surmise that? Is the raw unprocessed photo available (I couldn't find it after a little searching), or is is just that only those two much brighter stars show diffraction spikes, and no other stars have any sign of them?

[Chris Peterson]

Thanks so much for the explanation! I knew it wasn't a Hubble image, but you had excellent details in your image and it definitely is beautiful. The reason I was wondering was because there were other stars with diffraction spikes in your image but that one didn't have them which was why it was harder to determine its nature.

It looks to me like the diffraction spikes were added for aesthetic reasons, and are not in the actual data.

How did you surmise that? Is the raw unprocessed photo available (I couldn't find it after a little searching), or is is just that only those two much brighter stars show diffraction spikes, and no other stars have any sign of them?

Two reasons. First, they don't look like real diffraction spikes, which are not so uniform either in intensity or color. Second, the instrument that was used to collect the data does not have a spider mounted secondary to produce spikes.

[johnnydeep]

It looks to me like the diffraction spikes were added for aesthetic reasons, and are not in the actual data.

How did you surmise that? Is the raw unprocessed photo available (I couldn't find it after a little searching), or is is just that only those two much brighter stars show diffraction spikes, and no other stars have any sign of them?

Two reasons. First, they don't look like real diffraction spikes, which are not so uniform either in intensity or color. Second, the instrument that was used to collect the data does not have a spider mounted secondary to produce spikes.

Ah, yes, the scope was apparently a Celestron EdgeHD CGE 8" f/10 Aplanatic Schmidt-Cassegrain, and S-C scopes have the secondary mirror mounted in the middle of the front glass!

Click to view full size image

[ Hey - have svg images always worked here? I seem to remember them not displaying as images a while back. ]

[Ann]

Note the mini-spiral in the arm of UGC 1810 at upper right.

Seems embedded or piercing all right!
If we rotate Hubble's pic by 8.5° counter-clockwise as to make the North direct to the observer and then stretch a little,
we can see the central planar part of UGC 1810 (unlike the whole 3D rose button made tidally) as perfectly round.
And the third galaxy, a spiral dwarf, is clearly meddling with an arm.
Arp 273..jpg

What I don't get is why they say that the stem of the flower-like composition, UGC 1813, is the one that actually passed through the larger one.
If the space were empty there would be no way to tell which one is standing still and which one is passing.
Now there may be some ram pressure for some galaxies to make the difference, but is there any for Arp 273 flower-like system?

See that big gap between the larger galaxy's inner and outer arms? It makes sense to me that something may have passed through that gap to widen it.

My guess is that this is what astronomers think.

Ann

[neufer]

See that big gap between the larger galaxy's inner and outer arms? It makes sense to me that something may have passed through that gap to widen it. My guess is that this is what astronomers think.

My guess is that most astronomers think that these relatively undisturbed galaxies are simply passing by each other... although at a close enough distance that their outer edges are pulled out of their initial central planes by tidal interaction.

Peculiar Galaxies of Arp 273

Explanation: Their distorted appearance is due to gravitational tides as the pair engage in close encounters. The peculiar galaxies of Arp 273 may offer an analog of their far future encounter.

<<Close Encounters of the Second Kind: A UFO event in which a physical effect is alleged; this can be interference in the functioning of a vehicle or electronic device, animals reacting, a physiological effect such as paralysis or heat and discomfort in the witness, or some physical trace like impressions in the ground, scorched or otherwise affected vegetation, or a chemical trace.>>

[Chris Peterson]

See that big gap between the larger galaxy's inner and outer arms? It makes sense to me that something may have passed through that gap to widen it. My guess is that this is what astronomers think.

My guess is that most astronomers think that these relatively undisturbed galaxies are simply passing by each other... although at a close enough distance that their outer edges are pulled out of their initial central planes by tidal interaction.

That's what I'd think. If one had passed between the core and an arm of the other the entire thing would be one big mess, like the Tadpoles or Mice.

[VictorBorun]

See that big gap between the larger galaxy's inner and outer arms? It makes sense to me that something may have passed through that gap to widen it. My guess is that this is what astronomers think.

My guess is that most astronomers think that these relatively undisturbed galaxies are simply passing by each other... although at a close enough distance that their outer edges are pulled out of their initial central planes by tidal interaction.

That's what I'd think. If one had passed between the core and an arm of the other the entire thing would be one big mess, like the Tadpoles or Mice.

so much of a flower for Valentine Day

Judging by the visibility of brown and even orange dust backlighted by the core of the "rose button" galaxy in Hubble's pic we can tell that the "rose button" planar central part is seen at such angle that the lower part of the ellipsis is in fact the further part of the disk.
So the outer arm that got pulled from the plane of the disk down in the pic is the farthest from us.
So the "flower stem" galaxy is even further away from us

[XgeoX]

In the circle (top): Position of Arp 273 and HD 14511 on the sky.

---

Does anybody know if that beautiful bright golden star to the left in the photo is H14511?

HD 14511, yes. An 8.8 magnitude G5 star¹ at 444 parsec (1448 light-years) distance, as derived from Gaia data. (Previous estimates put it farther away.) [¹ thought to be a binary or multiple star system, but not visible as such in today’s image.]

Thank You Case!
It’s nice to know so I can calibrate what Sky Safari is showing me.

Eric