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robin_astro

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About robin_astro

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  1. Possibly but to alter a post without any obvious sign of editing and then attempt to gaslight someone who called it out is not acceptable in my view. I have added a comment to my original post to clarify what happened Robin
  2. The headline and screen grab used in the youtube thumbnail displayed in the post is generated by the youtuber and can be edited at any time, as can the video. You might not agree with what has been changed but it will still appear in your posts under your name. This is why it is not a good idea to embed anything from a site you do not control unless you trust it 100%. Robin
  3. The youtube screen grab and the current headline that says "Japanese mission that may have proved panspermia" Is not the original. Each time I looked it had been changed. This is at least the 3rd version
  4. The headline and linked video the top of this page has been changed several times during the life of this thread, (The problem with hot Iinking) I dont know who changed it or why (possibly as a result of my criticism.) but the original headline clearly stated that "panspermia had been proved" as I said in my first post. Robin
  5. Hi Nigella, If you use the prism line up the marks on the grating and prism (You can test the correct alignment by looking through the combination with the zero order on the left and rotating the prism until the zero order and spectrum move as far as possible to the left. ) you can add the prism before or after the grating, fix it in the right orientation using the locking ring or a bit of plumbers ptfe tape wrapped round the thread By adding the prism the dispersion becomes the combination of diffraction from the grating and refraction from the prism so you need to use a non linear fit for wavelength calibration using several Balmer lines instead of the simple 2 point calibration you can use without the prism Cheers Robin
  6. The archetype Cepheid variable delta Cephei for example (~900 light years away) has a parallax of 3.77 mas so the distance uncertainty from Gaia would be 0.04/3.77 = ~1% . If we found a Cepheid with the same period as Delta Cephei in another Galaxy we would know it has the same luminosity so by measuring its apparent brightness we can work out how far it (and hence the Galaxy) is Robin
  7. The parallax of objects outside our Galaxy is too small to measure. There are many Cepheids in our Galaxy close enough to accurately measure the distance to using parallax though. (The Gaia uncertainty of 0.04 mas is only a small percentage of distance for nearby objects). These are used to establish the luminosity/period relationship. You can then measure the periods and apparent brightness of Cepheids in nearby galaxies. From this you can calculate how far away they are and step up another rung on the distance ladder Robin
  8. So the most distant object that could be measured to an accuracy of say 20% is 5000 parsec. (0.2 mas) We then need to know what objects exist that are luminous enough to appear mag 14 at that distance You can use the distance modulus equation https://astro.unl.edu/naap/distance/distance_modulus.html to estimate the absolute magnitude (ie the luminosity) of an object with a brightness of mag 14 at 5kpc and compare it to the luminosity of the sun for example Cheers Robin
  9. The biggest problem might be extracting the data from the interference from all the satellite constellation passes Reading the SATCON1 report into how Starlink and other satellite constellations are going to impact astronomy, it is not clear how it is going to be able to do some of the jobs it was built for https://aas.org/sites/default/files/2020-08/SATCON1-Report.pdf
  10. It will be interesting to see how bright it is now. The mag 13.7 figure is a month old though. Odd Trondal measured it at 13.9 on 2020-09-02 so it was around maximum a few weeks ago and has probably faded quite a bit by now. Interestingly this is an all amateur supernova, having been discovered by the Chinese XOSS team and classified as a Ia by Italian Claudio Balcon. (The XOSS team asked if I could classify it so I was following it waiting for it clear some trees to get a spectrum but Claudio beat me to it !)
  11. The universe does not care about my view of our origins (and neither should you as you have no idea who I am, what my views on the subject are or if I have any knowledge of the subject) The same is true of our youtuber though so I made a point of following up the source publications, which should be included in any scientific presentation. The story often turns out, as here to be very different but equally interesting. For example the actual story behind the spurious mars seismometer signal (caused by a small thermally induced deformation in the top <1mm thick layer of the Martian surface) is that it could perhaps be used to improve the accuracy of our predictions of the orbit of Phobos which is important for future missions. Who would have though it !
  12. Yes let's do this where we can read what the professional scientists actually found rather than following these clickbait headlines https://www.frontiersin.org/articles/10.3389/fmicb.2020.02050/full https://ethz.ch/en/news-and-events/eth-news/news/2020/09/surprise-on-mars.html ie the experiment did not "prove panspermia" and nothing "strange happens on mars during an eclipse"
  13. "....survived for 3 years... proof of panspermia And this week's award for sensationalist extrapolation goes to... ! Without the original references these sort of presentations are useless. I highly doubt that the scientists involved made the claims he is promoting here in either of these presentations EDIT 2020-10-15: the quote "....survived for 3 years... proof of panspermia" was a direct quote from the headline on the embedded video at the time I posted my reply. This has been changed several times by the youtuber since then, possibly as a result of my comments, I don't know. It is a good example of why nobody should embed content from a website they do not control or trust 100% or comment on posts containing embedded content since this can be changed without any indication it has been edited
  14. The emission is caused by resonant scattering of sunlight off sodium atoms when in direct sunlight. With the sun above (or just below) the horizon, the bright sunlight (scattered off lower levels of the atmosphere) dominates the sky spectrum so the sodium D lines appear in absorption. After the sun sets as seen from the ground, the higher layers of the atmosphere are still illuminated by the sun so we see the emission from the sodium atoms. Cheers Robin
  15. Not a book but I find Michael Richmond's lecture notes good as they link observations and astrophysics in a concise but rigorous way. This one is relevant here http://spiff.rit.edu/classes/phys230/phys230.html particularly 12, 16-23 Cheers Robin
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