Greetings from Palmia Observatory
Well, now that we have some clearer skies we can look at the sun and see that more sunspots have come into view. So, get out and take a look now that the sun is starting to wake up.
|More spots on the sun, 600 mm, 1/2000 sec, DSLR (Source: Palmia Observatory)|
There are other bright objects in the sky for those of you looking up. How is your collection of lunar phase measurements coming along? This crescent moon is the 16th image of the group of images taken as part of our very own study, where we hope to make phase measurements over one lunar month. My preliminary measurement shows the moon at about 26% of a full moon. More about the final results in the upcoming blog post. It is getting a little more inconvenient to make these measurements now that the best shooting is early morning.
|Crescent moon, 300 mm, 1/500 sec, DSLR, 5:13 am (Source: Palmia Observatory)|
So, we are just waiting for the next opportunity to photograph the moon, but in the meantime, we saw this interesting article in an October 31 issue of Astrobites by Briley Lewis, who posed the question, "Who Can See Earth Transit?" We get used to hearing about all of the exoplanets discovered by seeing their transit across their sun, but have you ever wondered what other extraterrestrials making observations from their own star might just happen to notice the Earth making a transit across the Sun. Briley was reporting on a paper by L. Kaltenegger and J. Pepper, who looked for all nearby stars from which any observer there would be able to see the Earth as a transiting exoplanet orbiting the sun.
They looked at the conditions for Earth to be seen as a transiting exoplanet and found the distant stars would have to be arranged in a narrow band pretty much lined up with the plane of the solar system. The distance from the star to the Earth would also have to be close enough so that the observers from that nearby star could see the Earth transit if they were using the equivalent sensitivity of current exoplanet searches.
|Conditions for the Earth to be seen as a transiting exoplanet (Source: Kaltenegger & Pepper, arXiV:2010.09766)|
So, how many stars are there that are close enough and are located with alignment near the orbital plane of our solar system? Well it turns out that there are about 1000 stars that are within a 100 parsecs of Earth that fit the necessary requirements for making a transit observation of Earth. Most of those stars are small red M dwarf stars. Check out some of the data below or for more details look up the original paper. Anyway, thanks for alerting us to that study, Briley!
|Identifying stars in the Earth Transit Zone (Source: Kaltenegger & Pepper, arXiV:2010.09766)|
In other astronomy news, there was some interesting discussion regarding the proposed sources of Fast Radio Bursts (FRB) in the November 5 issue of Nature. Bing Zhang, University of Nevada, discusses the status of the search for the physical mechanisms associated with FRBs. Remember that FRBs are short, in the millisecond range, of received radio signals that were first discovered in 2007. The chart below compares FRBs with another type of discovery of short bursts, this time in the gamma ray region, called Gamma Ray Bursts (GRB). The GRBs were discovered first and their sources came down to both massive star core collapse and mergers of neutron stars. It seems that the repeating nature of both GRBs and FRBs is thought to be associated with a pulsing magnetic field of magnetars.
|Comparison of GRB and FRB fields (Source: B. Zhang, Nature, 5 Nov 2020)|
The surprising thing about FRBs is that they now have been discovered to be repeating type phenomena. This means that whatever is going on, it does not have to be a one time event. The FRBs are observed in all directions and most of which are outside of our own Milky Way galaxy. The article goes on to explain the two leading theories about the generation of FRBs. Mostly it seems that the source is a magnetar, a special type of neutron star with a very high magnetic field. Check out the two leading mechanisms shown in the diagram below. The observed repeating nature of FRBs is key to understanding what is going on. More details are included in the referenced article.
My understanding is that there are still two models being evaluated to explain FRBs. The two approaches are outlined in the following figure from the Nature article.
|Accounting for the repeating nature of FRBs (Source: B. Zhang, Nature, 5 Nov 2020)|
Also for all of you physicist wannabes out there who were wondering about quantum gravity and how the reconciliation between general relativity and quantum mechanics was coming along. This interesting paper Giampiero Exposito at the INFN in Italy looked at 16 different attempts. The paper came out in 2011, but it is probably current enough for now. So there is a lot of work going on, not just in string theory, but other approaches are under review too. So, there are a lot of areas for study for physicist wannabes, even though most of these approaches are way too difficult for me still. We also comment that physicists are so inventive and creative that they produce all sorts of possible theories to connect GR with QM. Which one of these approaches is your favorite, i.e. where are you spending your free time?
|Sixteen potential candidates (Source: G. Exposito, "An Introduction to Quantum Gravity", 2011)|
Finally, thank you all for your kind words of support on the passing of Astronomer Assistant Danny. It is hard to see him go and your support helped.
Until next time, here from our burrow, stay safe, as we recover more of our freedom,