3C 273: Quasars are Easy

Q: How powerful is your telescope?

A: It’s powerful enough that even with this light pollution I can see things 2.5 billion light years away, or nearly a fifth of the way back to the Big Bang.

3C 273 was the first quasar identified and it is bright enough to be seen in many amateur telescopes. Because quasars are star-like (the term quasar was coined as an abbreviation for quasi-stellar radio sources), they show up well in washed-out skies if you use magnification to darken the background. At magnitude 12.8, under typical urban/suburban light pollution 3C 273 should be visible in 8 inch (200 mm) telescopes on nights with good transparency, but it can be very challenging for 6 inch (150 mm) telescopes on all but the most transparent nights.

At 2.44 giga light years (750 megaparsecs or 1.5 x 1022 miles), 3C 273 is hands-down the farthest object brighter than 13th magnitude. While it looks no different than an ordinary star, just think how long that light took to get to you: the photons hitting your eye started their journey during the Proterozoic eon, just before Earth’s first major ice age (the Makganyene ice age), and about the time that the first generations of photosynthetic life forms triggered the Oxygen Catastrophe. Way cool!

Now, the challenge to observing 3C 273 is finding it….

3C 273 is located in Virgo just south of the Virgo Cluster. Like the Virgo Cluster, 3C 273 is best observed in the spring. You’ll find 3C 273 marked on Sky & Telescope’s Pocket Sky Atlas as well as various other common star atlases, but those atlases aren’t detailed enough to enable you to find 3C 273. The best way to find 3C 273 is to use the AAVSO star charts. You can generate the charts you need at different scales and resolutions by using the AAVSO Variable Star Plotter. It’s a great tool, so I encourage you to learn how to use it by generating your own 3C 273 charts.

However, to make life easy, I have pre-generated the AAVSO charts at “standard” scales A, B, C, D, and E, all oriented with north at the top and east on the left (the AAVSO tool allows you to generate any scale you want with whichever orientation you prefer). I’ve added some star labels to the first 3 charts to help you get oriented relative to the major stars in Virgo and also across the scale changes between the charts. The numeric labels on some of the stars indicate the visual magnitudes of those stars (as is standard on AAVSO charts decimals are omitted, so “103” means magnitude “10.3”). The scale changes across the remaining charts are much more intuitive: just pay attention to the magnitude 11.9 star to the west-southwest of 3C 273 and the magnitude 10.3 star to its southeast.

I find it easiest use an 8x50 finder-scope to navigate from η (eta) Virginis to “Star #1”, and then use a wide-field eyepiece to navigate from "Star #1" until I have located the 10.3 and 11.9 magnitude stars. If 3C 273 isn’t directly visible at this point (it usually is with my 10 inch Dob), I just substitute a higher power eyepiece and 3C 273 invariably pops into view.

So the next time you have a good night in the spring, take the time to find 3C 273 and enjoy traveling back in time a few billion years. And let me know how it goes.

If you have a larger telescope (10 inch aperture or better), there are a few more quasars that you can spot, although they are a lot more challenging than 3C 273, especially when observing through washed-out skies. But that’s a story for another day.



More quasars

As promised, I've published a follow-up story, A Fist Full of Quasars, (with apologies to Clint Eastwood) about three other quasers that you can see even from urban areas with washed-out skies. Good hunting!