Explanation: How big is our Sun compared to other stars? In dramatic and popular videos featured on YouTube, the relative sizes of planets, stars, and even the universe are shown from smallest to largest. The featured video begins with Earth's Moon and progresses through increasingly larger moons and planets in our Solar System. Soon, the Sun is shown and compared to many of the brighter stars in our neighborhood of the Milky Way Galaxy. Finally, star sizes are shown in comparison with the Milky Way Galaxy, galaxies across the observable universe, and speculatively, regions of a potentially greatermultiverse. Note that the true sizes of most stars outside of the Sun and Betelgeuse are not known by direct observation, but rather inferred by measurements of their perceived brightness, temperature, and distance. Although an inspiring learning tool that is mostly accurate, APOD readers are encouraged to complete the learning experience -- and possibly help make future versions more accurate -- by pointing out slight inaccuracies in the video.
It would be useful to add the distance from the Sun to Earth in light minutes, to Pluto in light hours, and to the nearest star when passing the 4 Light Year mark.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 5:09 am
by Ann
What does "Vit Drite" mean?
Ann
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 5:34 am
by bystander
Scale: How Far is Far?
Click to play embedded YouTube video.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 5:45 am
by Steve Basten
Would an Inconsistency be that the video shows the known universe to be 90 Billion Light Years across?. This seems a little off considering we believe the universe to be 13.7 Billion Years old, with a maximum speed of travel being light itself. The universe of course could be bigger but the known observable Universe cannot be anywhere near 90 billion light years if all we can observe is 13.7 Billion Light years in all directions around us?
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 5:53 am
by florid_snow
Ann wrote: ↑Tue Jun 12, 2018 5:09 am
What does "Vit Drite" mean?
Ann
From a quick google search, I think its Albanian for "light year". To be honest, I didn't even know that Albanian was a language, but I learned a little context from this very nice wikipedia page https://en.wikipedia.org/wiki/Indo-Euro ... anTree.svg
But the main reason I wanted to comment here was because of the statement at the end of the video: "Importance always means one thing in relation to another. There is no such thing as importance alone." Understanding this to be true has been consequential for my life, as well as being an honest description of something we can learn from the scale and rules of the universe, I think. Motion only makes sense defined relative to some other reference frame. The sun is big to us, but small next to Rigel. And that thing that happened last year might seem really embarrassing to you, but nobody actually cares that much. What a universe. I love you all, fellow humans and other consciousnesses that might be reading this in the future.
P.S. I'll let someone else answer Steve Basten's question, I just saw it get posted. I think the answer is that due to accelerated expansion, matter that emitted light towards us 13 billion years ago is now 90 billion light years away.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 6:02 am
by bcj_sf_nm@yahoo.com
I was under the impression that there is a large proportion of galaxies that are globular. Most of the ones in your image seem to be disks.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 6:08 am
by florid_snow
Here's my own follow up question to Steve Basten's. What is space, that it stretches so much that two objects within view of each other eventually appear to disappear? I only just barely understand special relativity (I think). How can space itself be expanding (on its own), if distance itself can only be defined in reference frames that include more things than just empty space?
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 7:36 am
by Guest
I feel like you're not even trying anymore..
There was time when APOD had some awesome photos, awesome information.. and now you post duplicates, some random amateur photos that have minimal to do with astronomy or some old YT videos..
This is sad..
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 8:27 am
by The other Guest
Oh, Guest, come on! APOD still posts excellent photos an information. I look at it every day. Maybe you have learned so much over the years that you changed your perspective. And please don't disrespect amateur photos! Scroll back to the early days of APOD - amateurs deliver comparable photos today. That's what I call awesome.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 8:52 am
by zarnivop
The most troubling missing feature in the video is false image for red supergiants. Red supergiants are not spheres! They do not have any defined shape, sending limbs and then absorb them back.
Best would be to recreate the animation, with changing, animated skin for all gasqice giants, stars, and the ever-changing form for red supergiants.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 9:01 am
by freddiecosmic
Has anyone else noticed that the Moon is reversed at the opening - why does this always keep happening in astro videos? It can be reversed in images through telescopes because of optics but this supposed to be a view of it as seen in the sky. I find this perpetuated mistake very annoying!
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 10:16 am
by Ann
freddiecosmic wrote: ↑Tue Jun 12, 2018 9:01 am
Has anyone else noticed that the Moon is reversed at the opening - why does this always keep happening in astro videos? It can be reversed in images through telescopes because of optics but this supposed to be a view of it as seen in the sky. I find this perpetuated mistake very annoying!
I noticed it!
Whenever I look at the full Moon these days, I see the Lady in the Moon. But we always see her left cheek, never her right cheek, in the same way that we never see the the far side of the Moon. (Guess her right cheek really is on the far side of the Moon, or else she must have mislaid it.)
I was about to say that we never see the backside of the Moon, because that is what we say in Swedish - månens baksida - but - oh, never mind!
And I was about to post a picture of somebody's backside, with or without (the) Moon(ing), but I decided against that, too. I'm not going to give you that much cheek.
Ann
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 11:11 am
by orin stepanek
I liked today's APOD! It showed an attempt to understand today's universe and show off it's size! There is no actual way to explore the realms of space except through science and imagination! Great job!
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 12:03 pm
by The first Guest
The other Guest wrote: ↑Tue Jun 12, 2018 8:27 am
Oh, Guest, come on! APOD still posts excellent photos an information. I look at it every day. Maybe you have learned so much over the years that you changed your perspective.
I agree, but the situation is rare. We get once a week a good photo and other times it looks like they had not spend time to give us something, so they used some random stuff...
The other Guest wrote: ↑Tue Jun 12, 2018 8:27 am
And please don't disrespect amateur photos! Scroll back to the early days of APOD - amateurs deliver comparable photos today. That's what I call awesome.
I don't, some of them are really good. Most of them are not, but some are..
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 12:46 pm
by ralphem
Nice, inspiring video of cosmic sizes, supported by one the lovely Vangelis sound track used in Carl Sagan’s Cosmos series. One must wonder, however, about the accuracy of the images and data when the very first image, of our Moon, is shown BACKWARDS. If everyone in the production of the video never caught this, then there is the suspicion that the team is not totally familiar with our cosmos. I’m being picky, yes, but accuracy counts, especially in science. Flip the moon shot and reissue it as revised.
Steve Basten wrote: ↑Tue Jun 12, 2018 5:45 am
Would an Inconsistency be that the video shows the known universe to be 90 Billion Light Years across?. This seems a little off considering we believe the universe to be 13.7 Billion Years old, with a maximum speed of travel being light itself. The universe of course could be bigger but the known observable Universe cannot be anywhere near 90 billion light years if all we can observe is 13.7 Billion Light years in all directions around us?
The crude structure at the edge of the known universe is basically the crude structure of the 372±14 kyr old cosmic microwave background radiation (CMBR).
The assumption is that that CMBR structure has evolved, cooled and expanded to a 13,700,000 kyr old shell with a current diameter of around 90 billion light years.
Inside that 90 billion light year wide shell are other expanding shells that we are able to view at more recent stages of their development.
Because of the dark energy acceleration of the universe there are many expanding outer shells that we will never be able to observe as "having matured to an age of 13,700,000 kyr."
The known universe is 13,700,000 kyr old and 90 light years wide but all we have (or will ever have) are mostly baby pictures.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 1:34 pm
by Guest
All good stuff. The fireflies at the beginning gave an interesting hint of the stunning kaleidoscope of life on earth, 8.7 million species (give or take 1.3 million)... & then all members of all species on the earth... & then zooming out...!! The jawdropping extraterrestrial tapestry surely provokes one to consider the old chestnut of 'alien' life forms out there. Life must be everywhere but please don't ask me to prove it!!
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 2:24 pm
by Fritz Stumpges
One thing I also find fascinating is that this video's notion of size in reference to larger is equally applicable to the smallness realm. I also find it interesting that we seem to experience our existence in approximately the middle; coincidence? or just that we are equally limited in our comprehension in both directions!
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 2:27 pm
by BDanielMayfield
I thought it was excellent for the most part, providing much more than the title lead me to expect, which was just stars. The way the Sun was, um, well, I hate to say it, but dwarfed by the progression of giants and supergiants almost makes me want to recant my often repeated gripe about main sequence stars like the Sun and larger being called dwarfs. So it shifted my perception. Well done!
A suggestion for improvement would be to add more stars. A neutron star, a white dwarf and stars of each class up the MS would help it to be more balanced and informative, I think.
Bruce
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 2:34 pm
by Chris Peterson
neufer wrote: ↑Tue Jun 12, 2018 12:52 pm
The crude structure at the edge of the knownobservable universe is basically the crude structure of the 372±14 kyr old cosmic microwave background radiation (CMBR).
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 2:38 pm
by Chris Peterson
Steve Basten wrote: ↑Tue Jun 12, 2018 5:45 am
Would an Inconsistency be that the video shows the known universe to be 90 Billion Light Years across?. This seems a little off considering we believe the universe to be 13.7 Billion Years old, with a maximum speed of travel being light itself. The universe of course could be bigger but the known observable Universe cannot be anywhere near 90 billion light years if all we can observe is 13.7 Billion Light years in all directions around us?
The error isn't in the size; the observable universe is indeed about 90 billion light years in diameter. The error is in supposing that you could ever be positioned such that you could view a spherical structure that looks like what the video shows for the CMB. We can never get outside the Universe, and no matter how far we zoom out, we will always observe the same thing around us. We never get closer to the CMB; it always lies 13.7 billion light travel years away from our observation point.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 2:54 pm
by anon
As an addition to the excellent point made that the observer is always at the centre of their own observable universe: if we take the Earth's POV and indeed travel beyond the boundaries of our visible universe, we have not travelled outside of the universe. The visible universe is much smaller than the full universe is predicted to be. So as much as I like the ending with the multiverse, the vital point of observable universe =/= universe has not been communicated.
Concur with previous posters that the title is somewhat misleading, suggesting it is entirely stellar based and the lack of variety in the galaxies. As pretty as spiral galaxies are, I feel sad for the elliptical ones.
To end on a positive note: I loved the inclusion of the roughly Saturn-sized star found recently and I learnt a bit more about the comparative sizes. Awesome video and hope my comments are useful.
Re: APOD: Star Size Comparison 2 (2018 Jun 12)
Posted: Tue Jun 12, 2018 3:09 pm
by BDanielMayfield
BDanielMayfield wrote: ↑Tue Jun 12, 2018 2:27 pmA suggestion for improvement would be to add more stars. A neutron star, a white dwarf and stars of each class up the MS would help it to be more balanced and informative, I think.
After rewatching the video I noticed the two smaller than our Moon solar system objects that where included to the left. A short further leftward jog down the distance scale to a city sized neutron star would be nice. White Dwarf stars might bracket Venus and Earth perhaps?
Then also, the caption on "the smallest possible star" needs to be corrected to 'the smallest Red Dwarf'.
BDanielMayfield wrote: ↑Tue Jun 12, 2018 2:27 pmA suggestion for improvement would be to add more stars. A neutron star, a white dwarf and stars of each class up the MS would help it to be more balanced and informative, I think.
After rewatching the video I noticed the two smaller than our Moon solar system objects that where included to the left. A short further leftward jog down the distance scale to a city sized neutron star would be nice. White Dwarf stars might bracket Venus and Earth perhaps?
Then also, the caption on "the smallest possible star" needs to be corrected to 'the smallest Red Dwarf'.
Bruce
Perhaps "The smallest possible core hydrogen-fusing star"?
Star Size Comparison 2
