Yes, the light spectrum is different. A type 1a is the implosion of a white dwarf which means there is very little hydrogen in the spectrum as opposed to a type 2 supernova which has a lot of hydrogen in its spectrum.
The distant 1A suoernove would be moving away from the Earth at a huge speed. Because of Einstein's time dilation would this superova appear to be dimmer than if it were not moving in relation to the Earth? In other words, would the amount of radiation from the 1A supernova received on Earth be spread out over a longer time period because of the 1A supernova's time being slowed from the Earth's frame of reference. Should this time dilation effect also be taken into account, as well as the inverse square law, when calculating the brightness of a 1A supernova?
The brightness of the supernova would not be affected much by its recessional velocity (unless the recessional velocity was so extreme that the light would be pushed into the infrared). The light would simply be shifted in the spectrum.
@@MichelvanBiezen Thanks for your reply. I have recently watched a RUclips video which explained how the visible Universe boundaries are the place where the stars vanish from view because, as I undestand it, the stars are moving away faster than the speed of light. Time dlation at this point would be expanded to infinity. Wouldn't any type 1A supernovae at this point appear to be frozen in time? I believe that, although the red shift of local galaxies are on the flatest part of the time dilation curve making time dilation an insignificant effect, the most distant 1A supernovea are not as far away as the inverse square law suggests if time dilation is not taken into account. It would also mean that there has been insufficient time for the Universe to expand beyond the observable Universe from the Earth's frame of reference.
The boundary of the visible universe is the location where stars are so far away that the light has not had enough time to reach us since the light's travel time is larger than the age of the universe. We don't know how much farther the universe goes, but it is conceivable that far beyond the visible boundary, galaxies are traveling at speeds greater than the speed of light, not because the galaxies are moving, but space between us and those galaxies is expanding and due to the great distance the recessional speeds become enormous.
@@MichelvanBiezen Thanks for your help. Just one thing is left which I don't fully understand. Does this mean that we will never see the photons currently emitted from stars which are currently over 15 billion light years away, however long we wait, because these stars are moving very fast and space is still expanding? If these stars are not moving faster than light, why will we never see them (asssuming we can live forever of course)?
As time goes by, we will see more and more galaxies as the visible universe boundary continues to move farther and farther, but we can assume that some very far away galaxies may never become visible to us.
Regarding the calculation of the distance to the Type 1A Supernovae, is the equation used an application of the inverse square law where L=k/d^2, where k is some constant, in this case 10pc. If so, how do you know k=10pc as i thought the relation between luminosity and distance is L=F/4(Pi)d^2, implying 10pc=F/4(Pi) which cannot be true buy doing dimensional analysis.
For the second example the distance to the Type 1A Supernovae is 32 million light years away. What isn't stated is that 32 million years ago the Supernovae / Galaxy was 32 million light years away. Why is this distinction important? Modern cosmology theory combines the standard candle and red shift equations without factoring in time to conclude that the expansion of the universe is accelerating today. There is not enough data for this conclusion to be invalid. The Hubble Telescope discovered a Type 1 Supernovae 10 billion light years from Earth. All that can be said is that 10 billion years ago the expansion of the universe was accelerating. This faulty conclusion has led to theories of dark matter and dark energy ... Is science off somewhere in the weeds?
I understand. Your specific question provides one of many starting points for higher level questions. So much modern day science and theory sits upon a foundation of assumptions that should be questioned as you've done here.
Your answer was a bunch of jargon which held no comprehensive scientific knowledge, yes, the universe is expanding; But that isn't the reason we have come to the conclusion the dark matter exists.
Karen C. They tend to be used interchangeably but they are somewhat different Brightness refers to the visual brightness. Magnitude refers to the visual brightness in terms of the magnitude scale.
If we know the distance to the galaxy containing the type 1A supernova and then we measure the apparent brightness, we can calculate the absolute magnitude. We have videos on how that is done.
That is a good point. However, stars do not appear by themselves, especially large stars that will result in a supernova, as they require dense nebula, in order to form, and thus these type of stars only appear in galaxies. It is unlikely that you would see a a star behind a galaxy as the dust and gases from the galaxy would prevent you from seeing anything behind the galaxy.
The magnitude scale does not have units. It is a relative visual brightness scale where the relative brightness is calculated by 2.512^n where n = the difference in magnitudes.
Good video but they do not all have the same brightness, because brightness depends on distance. You mean luminosity. Also, being a bit more precise M=-19.3.
Cogent, information dense, easy to follow. Well done.
This helped a lot with a book I’m reading on Dark matter and Dark energy. Thank you.
Prof. Biezen, how would one know that it is a Type 1a supernova in the first place? Is it based on the spectrum?
Yes, the light spectrum is different. A type 1a is the implosion of a white dwarf which means there is very little hydrogen in the spectrum as opposed to a type 2 supernova which has a lot of hydrogen in its spectrum.
Hi prof.biezen. whats is the negetive sign stand for in SN brightness ? -19 suppose to be smallest number than +5..tq.
negative numbers mean that the object is brighter -2 is 2.5 times brighter than -1
You are an inspiration sir!
We appreciate your comment. Glad that our videos help to motivate.
The distant 1A suoernove would be moving away from the Earth at a huge speed. Because of Einstein's time dilation would this superova appear to be dimmer than if it were not moving in relation to the Earth? In other words, would the amount of radiation from the 1A supernova received on Earth be spread out over a longer time period because of the 1A supernova's time being slowed from the Earth's frame of reference. Should this time dilation effect also be taken into account, as well as the inverse square law, when calculating the brightness of a 1A supernova?
The brightness of the supernova would not be affected much by its recessional velocity (unless the recessional velocity was so extreme that the light would be pushed into the infrared). The light would simply be shifted in the spectrum.
@@MichelvanBiezen Thanks for your reply. I have recently watched a RUclips video which explained how the visible Universe boundaries are the place where the stars vanish from view because, as I undestand it, the stars are moving away faster than the speed of light. Time dlation at this point would be expanded to infinity. Wouldn't any type 1A supernovae at this point appear to be frozen in time? I believe that, although the red shift of local galaxies are on the flatest part of the time dilation curve making time dilation an insignificant effect, the most distant 1A supernovea are not as far away as the inverse square law suggests if time dilation is not taken into account. It would also mean that there has been insufficient time for the Universe to expand beyond the observable Universe from the Earth's frame of reference.
The boundary of the visible universe is the location where stars are so far away that the light has not had enough time to reach us since the light's travel time is larger than the age of the universe. We don't know how much farther the universe goes, but it is conceivable that far beyond the visible boundary, galaxies are traveling at speeds greater than the speed of light, not because the galaxies are moving, but space between us and those galaxies is expanding and due to the great distance the recessional speeds become enormous.
@@MichelvanBiezen Thanks for your help. Just one thing is left which I don't fully understand. Does this mean that we will never see the photons currently emitted from stars which are currently over 15 billion light years away, however long we wait, because these stars are moving very fast and space is still expanding? If these stars are not moving faster than light, why will we never see them (asssuming we can live forever of course)?
As time goes by, we will see more and more galaxies as the visible universe boundary continues to move farther and farther, but we can assume that some very far away galaxies may never become visible to us.
Brilliant and simple method!
Thank you. Glad you enjoyed it. 🙂
Regarding the calculation of the distance to the Type 1A Supernovae, is the equation used an application of the inverse square law where L=k/d^2, where k is some constant, in this case 10pc. If so, how do you know k=10pc as i thought the relation between luminosity and distance is L=F/4(Pi)d^2, implying 10pc=F/4(Pi) which cannot be true buy doing dimensional analysis.
We are using the principle that the intensity is proportional to the inverse of the distance squared.
For the second example the distance to the Type 1A Supernovae is 32 million light years away. What isn't stated is that 32 million years ago the Supernovae / Galaxy was 32 million light years away. Why is this distinction important? Modern cosmology theory combines the standard candle and red shift equations without factoring in time to conclude that the expansion of the universe is accelerating today. There is not enough data for this conclusion to be invalid. The Hubble Telescope discovered a Type 1 Supernovae 10 billion light years from Earth. All that can be said is that 10 billion years ago the expansion of the universe was accelerating. This faulty conclusion has led to theories of dark matter and dark energy ... Is science off somewhere in the weeds?
this has no relevance to my question
I understand. Your specific question provides one of many starting points for higher level questions. So much modern day science and theory sits upon a foundation of assumptions that should be questioned as you've done here.
Your answer was a bunch of jargon which held no comprehensive scientific knowledge, yes, the universe is expanding; But that isn't the reason we have come to the conclusion the dark matter exists.
Excuse me, but are there Chapter 21-24 in this Astronomy 101 course (as listed on ilectureonline.com)? Thanks
We are working on those playlist now. We plan to publish those within the next 4 to 6 weeks.
@@MichelvanBiezen Thanks, it's great to know!
Are absolute magnitude and absolute brightness interchangeable terms?
Karen C.
They tend to be used interchangeably but they are somewhat different
Brightness refers to the visual brightness.
Magnitude refers to the visual brightness in terms of the magnitude scale.
Michel van Biezen Thank you! Really appreciate your videos!
How do we calculate the absolute magnitude as -19
If we know the distance to the galaxy containing the type 1A supernova and then we measure the apparent brightness, we can calculate the absolute magnitude. We have videos on how that is done.
Whenever I hear a guy using parsecs ... I expect the bow tie.
+CusterFlux Bowties are cool.
From a safe distance only … just like supernovas.
+CusterFlux Well I think of the Kessel run.
I once did the Kessel run in under 12 Parsecs - - - @@fluets5658
How can anyone be sure that that supernova is embedded in that galaxy? It could just as well be in front or behind the galaxy.
That is a good point. However, stars do not appear by themselves, especially large stars that will result in a supernova, as they require dense nebula, in order to form, and thus these type of stars only appear in galaxies. It is unlikely that you would see a a star behind a galaxy as the dust and gases from the galaxy would prevent you from seeing anything behind the galaxy.
@@MichelvanBiezen thx for clearing that up. Never seen anyone adressing those stuff when they talk about using the supernovas as measurmentpoint lol.
What are the units
The magnitude scale does not have units. It is a relative visual brightness scale where the relative brightness is calculated by 2.512^n where n = the difference in magnitudes.
What about black holes?
+Franco Battagliero Eh?
Good video but they do not all have the same brightness, because brightness depends on distance. You mean luminosity. Also, being a bit more precise M=-19.3.