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Cosmic Challenge: Quasar 3C 273

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Cosmic Challenge:
Quasar 3C 273



May 2022




Phil Harrington



This month's suggested aperture range:

Giant Binoculars (≥ 70mm)


3- to 5-inch (76-127mm)









3C 273


12h 29.1m

+02° 03.2'





Whenever my neighbor (I'll call him "Joe") sees me at one of my telescopes, he'll come over and ask "so, how far can you see with that thing?" Every time! You've also probably met someone like Joe. Well, unless you have a double-digit telescope, your answer should probably be "2.4 billion light years."


That's the distance to 3C 273, the sky's brightest quasi-stellar radio source, or quasar for short, and the first of its type to be detected when it was discovered in the late 1950s. The unusual designation indicates that it's the 273rd entry in the Third Cambridge Catalog of Radio Sources, which was compiled with the historic radio telescope at Jodrell Bank, England, first published in 1959. A few years later, after the optical component of 3C 273 was confirmed, Maarten Schmidt became the first to recognize that the relatively simple hydrogen line in the object's spectrum implied a redshift of 0.16, placing it at an unheard of distance. (To learn more about the fascinating early history of quasars, I recommend reading The Discovery of Quasars by K. I. Kellermann of the National Radio Astronomy Observatory in Charlottesville, VA.)



Above: Evening star map. Credit: Map adapted from Star Watch by Phil Harrington.

Above: Finder chart for this month's Cosmic Challenge

Credit: Chart adapted from Cosmic Challenge: The Ultimate Observing List for Amateurs by Phil Harrington.
Click on the chart to open a printable PDF version.


Like many other quasars, 3C 273 looks like just another dim, slightly bluish star. Looks can be deceiving. Given its tremendous distance, its total light output is an incredible 2 trillion times that of our Sun. Consider this. If it was located 30 light-years from Earth, roughly the distance to Arcturus, it would shine as bright as the Sun in the sky. What's even more amazing is that this enormous power source takes up a volume of space no larger than our solar system! But they are not just bright in terms of visible light. Quasars emit astonishing amounts of energy at all wavelengths across the electromagnetic spectrum.


Today, thanks in large part to the Hubble Space Telescope, astronomers have a better handle on the true nature of quasars. First, all quasars lie billions of light years away. That means when we look their way, we are looking back billions of years in time. This makes quasars great tools for learning what the early universe was like. Although they look like stars, astronomers know that they lie in the centers of young, very active galaxies that are still undergoing formation. 3C 273, for instance, is in the heart of a giant elliptical galaxy.


Above: This Hubble Space Telescope images shows the distinctive jet of material shooting out from the quasar. The jet is estimated to measure some 200 000 light-years in length. Photo credit: ESA/Hubble & NASA

Below: HST used a coronagraph to block the quasar's intense light, making it possible to detect the host galaxy. Photo credit: NASA, A. Martel (JHU), H. Ford (JHU), M. Clampin (STScI), G. Hartig (STScI), G. Illingworth (UCO/Lick Observatory), the ACS Science Team and ESA


While quasars were plentiful in the early universe, they are nowhere to be found in closer galaxies. Instead, we see supermassive black holes and, in some cases, galaxies with active galactic nuclei (such as Seyfert galaxies, like M77). This leads astronomers to conclude that most galaxies, at least the more massive ones, may have gone through a "quasar phase" early in their formation. A quasar's power comes from super-supermassive black holes, with masses ranging up to tens of billions of solar masses, surrounded by accretion disks of gas and dust. As a quasar's host galaxy evolved, most of the available gas and dust outside of the quasar/black hole's event horizon slowly evolved into stars, calming the supermassive black hole's feeding frenzy.


The trick to seeing 3C 273 through small telescopes is to wait for the best nights, when the air is dry and the sky is crystal clear. Even then, picking it out from all of the other, equally dim stars can be a challenge. To try your luck, aim your telescope toward the naked-eye star Eta (η) Virginis and then, with your lowest power, widest field eyepiece in place, nudge about 1½° northeastward to the reddish star SS Virginis, which itself fluctuates between magnitudes 6.0 and 9.6. From here, head about 1¼° due north to 7th-magnitude SAO 119392.  The quasar lies ¾° directly east of this last star, right next to a 13th-magnitude star that some could confuse for 3C 273 itself.  The quasar's blue color, however, will help set it apart from any stellar neighbors, as should the "mini Cassiopeia" asterism shown on the chart.



Above: 3C273 as portrayed through the author's 8-inch (20cm) telescope.


Like many quasars, 3C 273 is known to vary in brightness. Although it usually shines at magnitude 12.8, it has brightened by as much as a full magnitude in the past. But it can also slip a little unexpectedly, slowly dimming to magnitude 13.2 or so before returning to normal brightness.


So, to my buddy Joe, my answer is still 3C 273, and I'm sticking with it!


Good luck with this month's challenge! And be sure to post your results in this column's discussion forum.


Remember that half of the fun is the thrill of the chase.  Game on!

About the Author:

Phil Harrington writes the monthly Binocular Universe column in Astronomy magazine and is the author of 9 books on astronomy, including Cosmic Challenge: The Ultimate Observing List for Amateurs.  Visit www.philharrington.net to learn more.

Phil Harrington's Cosmic Challenge is copyright 2022 by Philip S. Harrington.  All rights reserved.  No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder.


  • John O'Hara, Sasa, warddl and 5 others like this


I've seen 273 years ago thru my 8" Cassegrain. I think it's the farthest object you can see in a backyard scope!! Thanks for posting!!

    • PhilH, John O'Hara and mdrumm like this
I’ve seen it only on an image I took with my 8” SCT and ASI178MC camera. It was definitely a bluish shade. Since I know Phil’s emphasis is on visual and not Astro, I will see if we get a clear enough sky to try it with my aged and not-so-good eyes. It should be a fun challenge!
    • John O'Hara and lwbehney like this

3C 273 is my favorite quasar and I even started a thread on it a while ago. I plan to revisit it with my C11 and maybe boost it with a 2.5x Tele Vue Powermate, hoping to see some jets. Probably wishful thinking about the jets, but doesn't hurt to try. 

    • John O'Hara and MikeHC8 like this
David Knisely
May 18 2022 04:25 PM

I may have some doubt that most people with modest aperture telescopes will visually see much in the way of color in 3C-273, so using its "color" in the eyepiece to help track it down might not be a great idea.  At around magnitude 12.8 to 13.0, many people would probably need something in the 10 to 14 inch aperture range to notice any easily distinguishable hue at that low level of brightness.  Even then, the color index of 3C-273 is +0.21 which is comparable to a late A-class star like 3rd magnitude Talitha (Iota UMa), or magnitude 2.5 Alpha Cephei, and those stars visually are more white than bluish.  I may have to try to image it sometime to see what my old DSLR shows, but visually (at least to me), 3C-273 appears pretty much colorless. 

    • John O'Hara, lwbehney and Eclipsed like this



This is a good challenge and also a very informative article about quasars in general and this one in particular.  I observed 3C 273 in April of 2018 using my C14, but I needed a very detailed chart to identify the star field.  As in your article, I starhopped from eta Vir to the NE.  I did not note any color to the quasar.  I made this eyepiece sketch.


Attached Image: 3C273_2018.04.21.composite.v1.JPG

    • PhilH, John O'Hara, lwbehney and 1 other like this
Thank you Phil for all the awesome stuff you do for astronomy.. 👍👍🍺
    • Dave Mitsky, PhilH, John O'Hara and 1 other like this
Dave Mitsky
May 28 2022 12:54 PM

I was able to log 3C 273 with my 101mm f/5.4 Tele Vue refractor in May of 2005 from Cherry Springs State Park in Potter County, Pennsylvania. I caught glimpses of the brightest quasar at 44x (12.4mm Meade Super Plössl) with averted vision. A distinctive stellar pattern lies slightly to the northeast of the quasar.

Information on and additional finder charts for 3C 273 can be found at the following URLs:




https://www.lsw.uni-...s/1226 023.html


I've observed a number of far fainter and more distant quasars using much larger apertures. 

There are lists of other quasars visible using amateur telescopes at these URLs:





    • John O'Hara likes this

I have seen 3C273 in 2012 in 100mm refractor (ED100/900) and 80mm refractor (AS80/1200). In ED100 I could clearly see at 176x quasar and the nearby 12.6 and 12.7 mag stars. I think I was detecting in short moments another nearby star of 13.5 mag.


In 80mm, the quasar was more difficult. It was already visible at 96x. More clear view was at 150x, I could see again not only quasar but as well the two nearby stars. The quasar was a little bit more easy to see than the stars so it was probably slightly brighter. It required strong concentrated effort to see the quasar.


BTW, the most distant target I saw so far was CTA-102. During the 2016/2017 burst, I was able to glimpse it through 50mm aperture.

Thank you Phil for all the awesome stuff you do for astronomy..

Thanks, Herschel. That's kind of you to say! smile.gif

A great observing challenge. I have even shared it with a friend.

It's probably the most distant thing any of us will see in a lifetime.

Thank You 

Dave Mitsky
Jul 24 2022 01:43 PM

Here's a screencap from Stellarium showing 3C 273's location.

Attached Thumbnails

  • Attached Image: 3C 273 Stellarium Wide.JPG
Dave Mitsky
Jul 24 2022 01:45 PM

The star to the lower left of 3C 273 in this close-up view has a magnitude of 10.25.

Attached Thumbnails

  • Attached Image: 3C 273 Stellarium.JPG

I stumbled into it with my 11 inch SCT in Bortle 3ish skies last year.  I was astounded to find it as it is also known by other names, an NGC , I think, and noticed in my Sky Safari control program that it was also designated 3C273 which I recalled was a very special Quasar.  I was astounded to read that it was 2.4 ish Billion LY away ! 


PS The astronomer who found the first Quasar died last year, I forget his name.

Apr 16 2023 08:56 AM

His name was Maarten Schmidt-- he was the first to realize that their spectra were enormously red-shifted, implying that they were at very large distances from us.

The NY Times ran a good obituary about him at the time. https://www.nytimes....ce=articleShare

Had the pleasure on Saturday of seeing it in a 20" Obsession in Bortle 5 skies. Looked like a dim star at mag 13 but was still profound that this is probably the farthest object that can be seen with a amateur scope. 

    • lwbehney likes this

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