robin_astro

Novae can be unpredictable in their decline For example nova Cas 2020 has been rebrightening repeatedly for 4 months now but nova Del 2013 faded over 2 months (AAVSO data dates month/day) Cheers Robin

This is how it looked through the Star Analyser (20sec exposure, 2020-12-05). Nice bright Hydrogen Balmer emission lines Cheers Robin

Hi John, Nice Balmer emission. What date was this? (The lines other than H alpha can be quite difficult to see at the moment at the resolution of the Star Analyser compared with a few days ago but they should become more prominent again over the coming days as the spectrum evolves.) This series of amateur spectra taken for Nova Del 2013 shows an example of how the spectrum evolves but every nova is subtly different http://www.astrosurf.com/aras/novae/Nova2013Del.html There is a nice collection of amateur spectra building for this nova too http://www.astrosurf.com/aras/Aras_DataBase/Novae/2020_NovaPer2020.htm Cheers Robin

Great ! The lack of H alpha in the flare is interesting (to me at least, not really knowing anything about flares 😁) Cheers Robin

I don't know about the origin of the wow signal but there appears to be a repeating signal in this forum https://stargazerslounge.com/topic/366374-identified-possible-origin-of-the-wow-signal/

I look forward to the peer reviewed version of this paper. Apart from the implicit unsupported assumption that intelligent life would only be found on planets orbiting "sun-like stars", the search area is so wide that it is pretty much inevitable that you would find stars of every type including "sun-like stars" in the Gaia catalogue regardless of the direction you looked in. They might as well have said "sun-like stars found throughout the galaxy and stars of every type found as possible targets for the wow! signal" Robin

A couple of spectra, one about 6 days before maximum and one about 13 days after https://britastro.org/specdb/data_graph.php?obs_id=8176%2C8020&multi=yes&legend_pos=ne The spectrum has evolved quite a bit in that time but continues to give a good match to typical type Ia supernovae of the same age (using SNID the supernova identification program, black measured, red match) Robin

No. I think you are confusing the apparent movement of an object across the eyepiece due to the earth's rotation with change in the apparent position of nearby and distant objects with a change in observing location (parallax). You can demonstrate the difference with your finger held out in front of your face. If you focus on your finger and rotate your head so your finger moves across the field you will see the finger stays in the same position relative to objects in the distance. If you move your head from side to side though the finger moves relative to the distant object. The observed change in position of a fixed object with time from one side of the eyepiece is almost entirely due to a change in the viewing angle, not due to the effect of a change in viewing position (parallax). eg , if a planet is at the same position as a distant star at one side of the eyepiece, they will still be at the same position relative to each other when they get to the other side of the eyepiece field to a degree of precision you could possibly expect to measure, (ignoring any effect of the relative orbital motion of the earth and planet). In parallax measurements you change your viewing location significantly relative to the nearer object (eg from one side of earths orbit to the other) and then the relative position of nearby and distant objects does change. Robin

Hi Adam, I am the Robin that Andrew referred to. I am also the person who developed the Star Analyser. Option 2 with the grating between the lens and camera sensor will not work as the focal ratio is too low (I recommend using the calculator on the RSpec website which is based on my recommendations to the Star Analyser manufacturer, Paton Hawkley Education Ltd. https://www.rspec-astro.com/calculator/ If you use the calculator you will see that the minimum recommended focal ratio for the SA100 is f4 and for the SA200 f4.5 and the calculator gives a warning for lower focal ratios) You could use the grating with the lens in an objective grating configuration though with the grating on the front of the lens. here are some examples of this on my website http://www.threehillsobservatory.co.uk/astro/spectroscopy_11.htm http://www.threehillsobservatory.co.uk/astro/spectroscopy_17.htm Use the same calculator to calculate the focal length range which will allow the spectrum to fit in the field by putting the focal length of the lens in place of the grating to sensor distance (Ignore the other warnings as they apply to telescope applications) Option 1 might work ok but it depends on the distance between the grating and the camera sensor. Use the RSpec calculator to test this. It will tell you if there are problems (The SA200 is more commonly used in filter wheel applications as it can be used closer to the sensor and has a lower profile so fits in most filter wheels) If you need more information you are welcome to contact me direct via the email address on my website Cheers Robin

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

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

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

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

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

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

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

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

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

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 !)

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 !

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"

"....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

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

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

Hypernovae are thought to be particularly energetic supernovae formed by core collapse of massive stars so yes, potentially producing a black hole if the remaining core is massive enough to form a black hole rather than a neutron star (Note that it is suspected that not all stars that collapse into a black holes necessarily produce a supernova explosions though. I believe this is an area of study) The spectrum of hypernovae show them to be type Ic, similar to type II but the original star had lost all its hydrogen before the explosion (hydrogen is not seen in the spectrum). The lines in hypernovae spectra are much broader though because of the high velocity of the explosion so are characterised as type Ic BL. Here is an example of supernova which I classified as a type Ic BL. I don't know if it was powerful enough to count as a hypernova though. https://wis-tns.weizmann.ac.il/object/2017ixv Someone has kindly listed the known details of galactic supernova remnants here. Most are of unidentified type but there are some type Ic and some possible black holes. Not sure if any are hypernovae though https://en.wikipedia.org/wiki/List_of_supernova_remnants This article does identify a possible extra galactic hypernova remnant though in M101 https://imagine.gsfc.nasa.gov/news/20may99.html (Treat the explanation with caution though - it is over 20 years ago) Robin