Discovering Interactive and Active Galaxies, 25 November 2013!Opening question: !1.Why are quasars red shifted? !A.Because everything is moving away from everything in the cosmos. Most a.of the galaxies astronomers see are red shifted, not just quasars. Quasars are brighter than most of those galaxies, so they were the first ones noticed.!This lecture is a narrative describing one way that scientists figure out how 2.nature works. !Each kind of active galaxy was discovered before the category "active galaxy" 3.existed. !In the 1940s, galactic astronomers discovered Seyfert Galaxies. !A.These active galaxies were named after their discoverer Carl Seyfert, an a.astronomer at the University of Michigan.!He noticed some galaxies that didn't look like other Hubble tuning 1.fork subtypes because they had blue, unusually bright nuclei. !He used Mount Wilson to catalog spiral galaxies at the same time A.and for the same reasons as Walter Baade(last lecture). !He could not think of a reason for this, other than that there was a 2.density of stars. !He published a list of these galaxies in an astrophysical journal. !3.Over the following years, more of these galaxies were discovered, A.but no one understood them. !In the 1920s, variable star astronomers discovered BL Lacertae. !B.Variable star astronomers monitor the brightening and dimming of a.variable stars.!Amateur astronomers can contribute to science through this field 1.since it does not require an advanced degree. !You only need to know how to make an observation in the right A.way. !Because of this, variable astronomers have widely ranging technical B.skill and equipment (fancy to basic).!Variable star observations are assembled by organizations like the 2.AAVSO (American Association of Varaible Star Observers). !Stars that have variability over a couple hours or days are A.monitored around the clock. Those that vary by months or years are checked monthly or yearly. !Stars that do odd things are only watched when they are a.expected to be most odd. !Each variable star astronomer is assigned a few stars. !B.Every variable star is being watched by 3-4 people in different C.weather systems all over the country. !Even if it is too foggy to see the star in one area, the other a.astronomers will be able to see it.!Every five years or so, the brightness data of irregular variable stars D.are graphed to see if there is a long term trend.!Sometimes a trend reveals itself, and an irregular variable star a.can be reclassified. !In the 1920s, an irregular variable star was discovered in the b.constellation Lacertae the lizard. !It was called BL Lacertae based on the formula of the cataloging 1.system for naming those stars. !Its name tells you it was somewhere between the tenth and fiftieth A.variable star to be discovered in Lacertae. !People watched it for a years, but never found any regularity to its 2.brightening and dimming. Because of this, it was labeled an irregular variable star.!You cannot do science with phenomena that are not regular– A.randomness cannot be expressed with a mathematical equation. "!In the 1970s, a new 4 meter wide telescope at a National 3.Observatory in Arizona revealed that BL Lacerte was a galaxy rather than a variable star. !All astronomers can apply for time on the telescopes of these A.national observatories. !This is opposed to private observatories like Lick and Keck, a.which are only available to astronomers who are a part of the organizations that own them (like the UC system). !A group of variable star astronomers applied for time on this B.telescope to take the spectra of irregular variables. !This would hopefully reveal what the stars were doing, since a.luminosity over time information was not helpful for them. !This work was assigned to grad students earning phds in stellar b.astronomy. !The grad students were able to understand these variable stars c.to different degrees using spectroscopy, but they did not understand BL Lacertae at all. ! BL Lacertae's spectrum was faint and fuzzy, with only 1.suggestions of absorption lines. These lines weren't near anylines the grad student's recognized. !The spectrum resembled that of a Seyfert Galaxy. !A.After the spectrum of BL Lacerte was retaken to ensure that they C.the grad students taken the spectrum of Seyfert Galaxy by accident, it was reclassified as a galaxy.!The grad students were doing their phds on variable stars, so a.they no longer had to attempt to explain BL Lacertae. They were relieved. !Though BL Lacertae was definitely a galaxy, no one understood how it 4.could vary its brightness in a month or shine so brightly from so far away. !Something that varies in a month cannot be more than 1 light A.month wide. !If an object is bigger than a light month, the signal on the object a.that tells the object to change its luminosity will need longer than a month to take effect. !This seemed impossible because galaxies are usually a lot bigger b.than 1 light month. !The nuclei of galaxies are usually hundreds of lightyears wide. !1.If the object was as far away as astronomers thought, it had to be B.putting out a stupendous amount of light to be seen from earth. !A star with so much energy in such a small space should C.theoretically explode. !This remained a puzzle to astronomers for another decade. !a.In the 1950s, radio astronomers discovered quasars. !C.Radio astronomers are entirely different people from optical a.astronomers. !Radio astronomy was invented in the 1920-30s by Karl Janksy and 1.Grote Reber. Until the early 1940s, these were the only two radio astronomer.!Janksy was an employee of Bell Laboratories whose goal was to A.reduce static on long distance radio.!Some of this static was from the galaxy, so could not be reduced a.by AT and T. !Both of these people were electronic engineers rather than B.astronomers (though Reber was an amateur astronomer). !Reber found some interesting things in the sky, but regular a.optical astronomers could not understand his results. !Radar technology developed in WWII lead to the foundation of radio 2.astronomy. !Radar was used to detect Luftwaffe bombers before they reached A.allied countries. !There was an extremely high priority on developing radar at this a.time. !Technicians at this time detected that the sun was broadcasting b.radio waves, but they could not pay it much mind during a war. !Once the war was over, the electronic engineers who used radar B.technology could pay attention on the