Well the weather and clouds have been great if you are studying meteorology, but for astronomers here in OC, whether day or night, the skies have not been our friends. So, in the meantime, we can report on some upcoming star parties, symposiums, physics colloquiums, observatories, our upcoming total solar eclipse event in Chile and targets of interest while in the southern hemisphere.
If you are interested in doing some "sciencey" type astronomical observations then be sure to attend the upcoming Society for Astronomical Sciences (SAS) symposium in Ontario, CA, on May 30 - June 1. I have been to this symposium several times in the past and always find it very interesting. Serious amateurs report their own journey into spectroscopy, interferometry, exoplanets and light curves for variable stars and discuss collaborations with the professional astronomers. The symposium is very low cost in comparison to other professional conferences and you can check out the details at: www.socastrosci.org and you can meet up again with former OCA Secretary, Bob Buchheim, who is an author and leading SAS organizer.
Also if you want to take in some dark skies and still be quite close to the creature comforts found close by, then check out the upcoming Star Party in Julian, CA. on June 8. We have always enjoyed being in the old mining town of Julian and enjoyed the dark skies and friendly atmosphere, but unfortunately can't attend this year. Check our the details in the flyer posted below or check in with Julian Astronomer Doug and Associates at Curiosity Peak Observatory in Julian. Thanks for keeping us upto date, Doug!
|Star Party in Julian, CA (Source: Julian Dark Sky Network)|
Now back to the indoors activities. First up is the UCI Physics Colloquium where Professor Jedidah Isler, Dartmouth College, spoke on "Using High-Cadence, Multiwavelength Observations to Understand the Disk-Jet Connection in Blazars."
|Professor Jedidah Isler, Dartmouth College, leads UCI Colloquium on Blazars (Source: Palmia Observatory)|
So what is a Blazar? To me, a blazar is really just the same thing that we used to call quasars, but that the jet is almost aligned with our line of sight so its luminosity is very bright. In fact for jets, with material being ejected at almost the speed of light, and the jet aimed to within just a few degrees of our line of sight, the luminosity of the jet as observed here can be hundreds of times brighter because of he effects of relativistic effects. In the slide below you can see the conceptual structure of a blazar as a central black hole being fed material from an accretion disk and the energy of all of this infalling material results in powerful jets being produced and ejected perpendicular to the accretion disk. The infalling material approaches the speed of light and gigantic amounts of energy can be released. As radiation from the jets passes through clouds of gas in orbit around the black hole, there are regions of narrow line radio emission and broad line regions of radio emission.
|Professor Isler explains the current understanding and structure of blazars (Source: Palmia Observatory)|
There are many different regions around the central black hole and they each emit radiation that covers a very wide frequency range. One of the interesting findings is that the luminosity varies and is correlated over the wide frequency range. The bumps and peaks in the frequency spectrum tell us much about what is going on in the various regions of the blazar. For instance, we don't see much of a black body or thermal spectrum so it seems that most of the astrophysical processes going on there are mostly non-thermal, such as synchrotron emission.
|Jedidah Isler explains the wide blazar spectrum from radio to gamma rays (Source: Palmia Observatory)|
As the amount of material available to fall into the black hole from the accretion disk varies with time and circumstance, the variation in the observed light curve correlates with those events. The color diagram plot below (taken from one of Professor Isler's online publications) shows the variation, over a long period from observations made 2008 to 2015, in the color of the radiation. The variation is plotted with respect to the magnitude in the J band and you can follow the variation in the color coded trends according to the Julian Dates of the observations. So you can see that the variation follows a trend line for some years and then changes in color trend in one direction or another direction over many years. Some interesting physics, maybe just following material availability to fall out of the accretion disk into the black hole, but interesting nonetheless. Thanks for explaining some of the observations and details, Professor Jedidah Isler!
|Color variability in blazar 3C279 from 2008 to 2015 (Source: J. Isler, et al, 1706.09891v1, 29 Jun 2017)|
As interesting as the blazar discussion was, I was also interested in some of the observatories that contributed to the study and followed up with my own individual search. Of course, the Fermi LAT provided gamma ray observations, but two land based observatories were mentioned. First up was the SMARTS Consortium (Small and Moderate Aperture Research Telescope System) which has four telescopes located on Cerro Tololo, Chile. Hmm, while we are in Chile for the total solar eclipse, it would be nice, but not likely, if we could swing by and see this group of telescopes too!
|Some SMARTS domes on Cerro Tololo, Chile (Source: SMARTS Consortium)|
One of the other observatories that contributed data to the blazar study was the SALT (South African Large Telescope) located also in the southern hemisphere in South Africa. The SALT is a large segmented mirror telescope made up of 91 1-meter mirrors for a total aperture of 11 meters in diameter.
|South African Large Telescope (Source: SALT)|
The internal design of the telescope is shown below. The 91 mirror segments need to be aligned after re-aluminizing the mirrors, which needs to be done periodically, and an external tower provides the alignment capability. You can also see that the telescope design does not allow for any change in elevation, which makes it an unusual design. Apparently, just the rotation of the Earth is enough to gain a pretty wide view of the sky.
|Internal structure of SALT with mirror segment alignment tower also shown (Source: SALT)|
Finally, we come to the last part of this blog and summarize some lessons learned regarding our upcoming journey to Chile for the total eclipse of the sun in July. Our lessons learned and identification of desired optical targets, most of which are naked eye or DSLR visible, located in the southern hemisphere in include:
- Experience and view and photograph the total solar eclipse on July 2
- View and photograph the Milky Way from the southern hemisphere
- View and photograph the Large and Small Magellanic Clouds
- View and photograph Alpha Centauri (the closest off stars)
- View and photograph the Eta Carinae Nebula
- View and photograph the Southern Cross constellation
- Identify where the south celestial pole (SCP) is located in the sky (Polaris is not going to help!)
- If you intend to use a tracking mount, ensure that it will track properly in the southern hemisphere
Anybody have any other targets not to miss while visiting in the southern hemisphere?
The Sky Safari Pro screenshots below show the predicted locations of Alpha Centauri and Eta Carinae as seen from near Santiago, Chile.
|Sky Safari Pro screenshot showing sky location of Alpha Centauri in Santiago, Chile (Source: Palmia Observatory)|
It will be neat to finally be able to see Eta Carinae. Especially, after reading about it for years and hearing that if the thing eventually really blows up that the radiation received here on Earth could be vey catastrophic! Hmm, would it be best if it blows while we are there to see it or would it be better to have the Earth in between us and the radiation? Probably not a good time for the whole Earth if it did blow!
Finally, even though we are pretty much assured that we will not take a tracking mount to the southern hemisphere, it is still an interesting question about how to align a mount there and what do you use to find the South Celestial Pole (SCP)? One approach discovered after an internet search is the one using an offset from the Southern Cross Constellation. You can see the approach illustrated in the webpage screenshot below.
|Using the Southern Cross as one approach to locating the South Celestial Pole (opticscentral.com.au0|
Finally, as a first pass at answering the question if the lightweight Sky-Watcher tracking mount, which we kind of think we will not take with us, would actually track ok in the southern hemisphere. I hadn't really thought about this issue until our Chilean eclipse tour organizer and travel agent, Mark, from AClassicTour.com, alerted us to the need to verify our mounts would work. Thanks for that alert, Mark!
Well, one can verify that the iPhone app to control the mount does allow you to select latitudes both north and south of the equator, so it seems that maybe the tracking algorithm is good to go? Anybody with more feedback on this issue?
|The Sky-Watcher iPhone app at least lets you select a southern hemisphere location (Source: Palmia Observatory)|
Until next time,