66 AUSTRALIAN SKY & TELESCOPE November | December 2017
SKETCH: HOWARD BANICH;ATLAS OF PECULIAR GALAXIES: HALTON ARP/ NASA / IPAC EXTRAGALACTIC DATABASE (NED) / CALTECH / CARNEGIE OBSERVATORIESArp’sAtlas of Peculiar Galaxies
so neatly into the 1.2-m scope’s high-power view? To begin,
16Psc,Arp284and2333+019representoneofthedeepest
depthsoffieldavailabletoamateurobservers.Thestar16Psc
liesinourMilkyWaygalaxy,about101light-yearsdistant.
Thatdoesn’tseemsofaraway.
Butasnotedabove,thetwogalaxiesofArp284areabout
100millionlight-yearsaway,whilethequasar’slighthas
takenabout10billionyearstogethere.Thesenumbersare
muchmoredifficulttorelateto,solookingateventsonEarth
whenthesephotonsstartedtheirjourneyhelpsgivethem
some perspective.
WorldWarIwasraging101yearsago.AlbertEinstein’s
theoryofgeneralrelativityhadbeenpublishedforonlyayear
and was as yet unproven.The Cretaceous Period was in full swing 100 million
years ago; the first flowering plants made their appearance.
Dinosaurs were leaving their tracks on the muddy shorelines
of Earth’s lakes and seas.
The Earth didn’t exist 10 billion years ago, and its Sun
wouldn’t form for another 5 billion years or so. Everything
that makes up the Solar System today was part of some now-
extinct star, the interstellar medium, or a mixture of both.
Okay, that’s incredible.
Now consider that in the photons’ frame of reference,
time and distance have both become something outside the
human experience. At light speed, time slows to a stop and
distance contracts to zero — something I didn’t recall while at
the eyepiece. So in the photons’ frame of reference, they were
emitted by the quasar at the same instant they were absorbed
by the retina in my left eye. No time and no distance.
This is equally true for the photons coming from Arp 284,
16 Psc, or any light source for that matter. Goodness.
As if this isn’t mind-bending enough, the universe was
expanding during the 10-billion-year light-travel time. When
the photons I saw left their source, the quasar was only 5.8
billion light-years from Earth. Now, redshift tells the story of
the expanding space those photons have crossed: For a
z = 1.871 object, that space has enlarged by almost a factor of
three. I’m not sure if that’s more or less crazy than a timeless,
distance-less photon traveling for 10 billion years.
All this is as unintuitive as it gets, and although it’s an
accurate description of reality, I really don’t understand how
it works. Nonetheless, I’ll never get tired thinking about it,
especially when ageless photons entice me to try.◗American astronomer Halton Arp focused on both galaxy
formation and quasars during his career, using his research
in these areas to argue against the Big Bang theory. Although
his rejection of the Big Bang remains controversial, hisAtlas
of Peculiar Galaxies, produced in part to support his ideas,
remains one of the best catalogues of interacting galaxies.
Arp began gathering the photos that would serve as
the basis for his atlas in 1962. Using earlier, similar lists
compiled by Swiss astronomer Fritz Zwicky and Russian
astronomer Boris Vorontsov-Vel’yaminov as a starting
point, Arp sifted through images captured with the
1.2-metre (48-inch) Schmidt telescope and the 5-metre
(200-inch) Hale telescope, both at Palomar Observatory. He
eventually selected 338 images of galaxies with unusual, or
‘peculiar,’ shapes and sorted them into four groups based
on each galaxy’s deviation from a classic spiral form.- The AtlasofPeculiarGalaxiesis available online at
https://is.gd/ArpCatalog.
SWOW!!! A view of a quasar 2333+019 warrants three exclamation
marks in anybody’s observing log. The author’s sketch of Arp 284 shows
the 18th-magnitude quasar as viewed through Jimi Lowrey’s 1.2-metre
telescope at 609× and 812×. South is up.DEEP DISCOVERY