I know my title for this image is bold. It is my hope you will find the idea somewhat original and surprising. I have been wanting to make this image for several decades, and it is only in the last handful of years that I think it has been possible in a compelling way. This object is nearly as famous as the Orion Nebula or the Andromeda Galaxy because it is the closest of its type — and it is a true astrophysical wonder. That is why I feel passionately that it deserved a ground-based amateur reference image that captures the essence of the object.

A quick summary of what this image captures:

This is the first "complete" image of this object showing all features — colors and details — from a ground-based telescope, and most importantly showing the host galaxy.
This is the closest quasar, at a whopping 2.4 billion light years away, and shows us what the Universe looked like at an earlier time.
This object is 10,000 times brighter than a typical supernova — and has been continuously so for billions of years.
It has a relativistic jet screaming out of the quasar and its host galaxy. The length of the jet is approximately the same as the diameter of our own galaxy.

Space-based Reference

The HST image remains the best high-resolution image of this object. As you can see, it is still a challenging object to interpret, and my hope is that my image helps clarify the story.

📷 3C273_HST_1.jpgI used a similar — though greatly simplified — technique to reveal the host galaxy as the one astronomers used in the HST image. The PSF (the quasar's star-like light) is subtracted to reveal the host galaxy and inner structure.

An Intro to Quasar 3C273:

The name comes from the fact that it was the 273rd radio source detected in the Third Cambridge Catalogue of Radio Sources (3C), published in 1959. Quasars are galaxies with extremely bright central nuclei. They are so bright that the nucleus outshines the host galaxy by orders of magnitude. To be clear, there IS a galaxy here, as there is for all quasars. All of this energy output is driven by a massive central black hole that, in this particular case, is also directing a jet of relativistic gas away from the galaxy. This jet spans roughly 200,000 light years, approximately the diameter of our own galaxy.

The optical counterpart of the radio source was quickly identified, and the image below, taken with the Palomar 200-inch Hale Telescope, is the first photograph of it. You can clearly see the quasi-stellar object and its jet. But this is no nearby object. Based on its redshift, this quasar is more than 2 billion light years away — and even more remarkably, it is the nearest one to us. This is an important idea. There are essentially no other objects like this in the local Universe, which means this kind of object belongs to a prior epoch in cosmic history. There were more frequent galaxy collisions and large quantities of infalling mass were feeding tremendous black holes. When we look at 3C273, we are seeing a picture of that earlier time.

📷 200in_Palomar_1963.jpgYou can clearly see the “quasi-stellar” object and its jet. But this is no nearby object. Based on its red-shift this Quasar is more than 2 billion light years away and even more amazing- it is the nearest one to us. This is an important idea. There really are no other objects like this in the local Universe. That means this kind of object is really from a prior epoch of the development of our Universe at a time when more galaxy collisions occurred with large quantities of mass which made tremendous black holes. So we are getting a picture of an earlier time when we look at this.

Here is a fact I find so astounding that it deserves to be repeated every time this quasar is discussed. This object has… and you really need to sit down for this… an absolute magnitude of −26.7. That is the same apparent brightness as the Sun. However, this object would appear as bright as the Sun from 30 light years away. By comparison, the Sun would appear as a 5th magnitude star at that same distance, giving it an absolute magnitude of +5. A typical supernova explosion reaches an absolute magnitude of around −17. That means this quasar is 10,000 times brighter than a supernova — and has been continuously so for billions of years.

I hope you will forgive me when I say that this object is so incredibly special that it is a crime there are not more images of it.

The Challenge

Now that I have described what it is, the challenge becomes capturing as much of this object as possible which is the "essence" I referred to earlier. This object presents several distinct features worth capturing. First and foremost there is a giant elliptical galaxy subtending around 29 arcseconds. It may show color and perhaps even some detail, which is within reach of long focal length telescopes. Then there is the jet and detecting it at all is genuinely rewarding though any color or detail would be a bonus. And finally there is the quasar itself, which has a definite blue color due to the temperature and energy of the gas in that region.

The problem is that those 29 arcseconds of galaxy are almost entirely engulfed by the blurred PSF of the quasi-stellar point source. Essentially we have a bright, blobby star at the center, and as with any object where a bright star dominates, we want to minimize it in some way without artificially altering the underlying information.

Below is the stacked luminance image without any additional processing. This is the typical view of this object. I had an additional piece of bad luck: the jet lies almost exactly along one of the diffraction spikes of the quasar. Even so, you can already see hints of the elliptical host galaxy.

📷 3C273_Lum_original.jpgThe PSF Subtraction

The idea I have had for years was to do what you now see in the final image. I selected a field star of similar magnitude within the frame and subtracted it from the quasar. This removes the bulk of the quasar's light along with its diffraction spikes, leaving the host galaxy I have always wanted to see clearly.

To use this star effectively I needed to take several steps:

Apply BXT with "Correct Only." This regularizes the stars in the field and removes optical aberrations, resulting in a cleaner PSF subtraction. It would not make sense to apply full BXT deconvolution before subtracting, as that would introduce artifacts.
Align the subtraction star precisely to the quasar using PixInsight's Dynamic Alignment.
Subtract the local sky background from the subtraction star using PixelMath: $T - med($T).
Clone stamp any background galaxies near the subtraction star that might otherwise contaminate the result.

After subtraction, the host galaxy and jet are clearly visible. The quasar has been largely removed and the diffraction spikes are gone, revealing what I believe is the real story of this object.

In the picture below I circle the star I used:

📷 chosen_field_star.jpgValidating the Result

You might reasonably ask: how do we know this glow is not simply an artifact of the subtraction process? To test this, I applied the same subtraction star to a field star of comparable brightness located to the right of the quasar. If the subtraction were causing spurious structure, we would expect to see similar artifacts around that star as well. I hope you agree that while the subtraction is not perfectly clean, it does not produce anything resembling the extended glow surrounding the quasar. I am therefore very confident the result is genuine.

Below is an image of the background subtracted and cleaned star I used:

📷 subtraction_star.jpgNow I can show you the subtracted image:

📷 3C273_Lum_subtracted.jpgThis image captures something the HST images of this object do not, in the sense that those observations concentrate on the central region rather than the full extent of the host galaxy.

If you look closely at the center of the subtracted image you can see a stellar residual and a possible ring-like feature. I am not confident about the reality of that ring. We are working at the sub-arcsecond regime, where confidence should drop accordingly. When BXT was subsequently applied it regularized this region into a more stellar appearance, which I allowed. In the final image I reintroduced a portion of the quasar's brightness to communicate its presence without overwhelming the surrounding detail.

📷 3C273_test_star_subtracted.jpgThe above image shows my test of subtracting my control star from the field star to the right of the quasar. No halo is found.

Below is lightly sharpened BXT image. The “ring” feature is now not really evident.

📷 3C273_Lum_BXT.jpgColor

For the RGB image the same subtraction approach was applied, with the additional constraint of needing a field star of similar brightness that was not strongly colored. The star I chose satisfied this well. After subtraction the blueness of the quasar was strong and saturated since this object is significantly bluer than the nearly white control star.

As for the color of the host galaxy, I would place my confidence at around 75%. The galaxy is genuinely faint and some of its light is inevitably subtracted away. The somewhat reddish appearance is likely due in part to the dramatic cosmological redshift at which we observe it. The jet is detectably bluer than the galaxy. BXT helped reveal the segmented nature of the jet, and if you look carefully you can see hints of the small perpendicular features visible so clearly in the HST image.

Am I on the right track toward making this the most complete ground-based image of the most famous quasar in the sky?