Jason Nishiyama @evilscientistca@octodon.social
Teacher, astronomer, political scientist and father.
Kinematic studies suggest that M57, the Ring Nebula, is actually barrel shaped and that we're looking down one end. https://octodon.social/media/l7avkBa0ZM9QykQ9tHg
The distance unit parsec is defined as a parallax of one arc second measured over a base of 1 astronomical unit. 1 parsec is 3.26 light years.
Planetary nebulae are important contributors to Galactic chemical enrichment. Upwards of 50% of the carbon added to the Galaxy come from these objects.
M31 is the closest large galaxy to ours that looks like our Galaxy. It will collide with our Galaxy in about 4.5 billion years.
The Horsehead nebula is a dark nebula in the constellation of Orion. We see it because of glowing gas behind it. In this image blue is [OIII] light , green H alpha, and red [SII].
Our star the Sun is a middle aged star. It has been around for about 5 billion years and has about another 5 billion years left in it. https://octodon.social/media/P45eVKBrV2zz98Tefk8
Elements heavier than iron can't be made in stars. It takes the energy of supernova explosions to make heavier metals. To paraphrase Carl Sagan, all the gold in our banks and uranium in our weapons was forged in the death of stars. https://octodon.social/media/PoktWH6xVdZJd9V9OPk
All of the gas giant planets in our solar system have ring systems. Only Saturn's are spectacular enough to be visible through binoculars or a small telescope. https://octodon.social/media/OZG-4bCCOginA2dP1YY
Between about 0.01% and 1% of the mass of a planetary nebula is dust. This dust is detected by using infrared telescopes. https://octodon.social/media/hj6hDKs-7sFeekU1BPo
The amount of metal in stars (that is the stuff that isn’t H or He) generally decreases the further the star is from the core of our Galaxy.
Stars are divided into various populations depending on how much metal (elements heavier than helium) they have. Population I stars like the Sun have the most metal. Pop. II stars have lower amounts of metal. The very first stars would be the hypothetical Pop. III with no metal.
Polyaromatic hydrocarbons are a form of organic molecule that have been found in objects in space such as planetary nebulae. Such molecules may have been the precursor of the organic molecules that formed life on Earth.
There is dust in interstellar space. We need to account for this when making measurements as it not only dims the light, but reddens it by scattering more of the blue light.
Messier 56 is a globular cluster in the constellation Lyra. It's about 33kly away and like most globular clusters has low metallicity, that is has lower amounts of elements heavier than helium. This suggests it is made up of very old stars. https://octodon.social/media/fuOl3bdiqrJpyVTiq2w
../If it's in bracket notation one has to find the solar abundance in yet another paper. This is often in log+12 notation so has to be converted to the abundance ratio. Then take the reported abundance in bracket notation one can then work backwards to find out the actual abundance.
I've the urge to create yet another way of reporting abundance that requires the use of all of the above plus some other random numbers just to make things interesting.
../Yet another method is sometimes called "bracket notation". The abundance is reported as [A/B] where [A/B]=log(A/B for object)-log(A/B for the Sun). This again provides numbers that don't need to be reported with scientific notation.
The fun begins when your publication is using the abundance ratio A/B. Some references use mass fraction, some log+12. The real fun begins if they us bracket notation. ../
../However if the elements are H or He they can be reported as a mass fraction reported as X, Y, and Z where X= mass of H/total mass; Y=mass of He/total mass and Z=mass of everything else/total mass.
Another way is log+12 notation. As most abundance ratios are quite small compared to H, a common comparator, scientific notation is often needed. Log+12 prevents this by having the ratio be=log(A/B)+12 which is usually a positive number between -1 and 10. ../
It's amazing that in astronomy/astrophysics we have several ways of communicating the exact same piece of information requiring the researcher to have to constantly convert between the various methods.
For example, elemental abundance (the amount an element in an object).
As measured this is usually presented as a ratio of element A to element B as we can measure the brightness of both lines and the abundance ratio is proportional thus:abundance=A/B and can be reported as such. ../
Because they take matter that was created in the centre of the star that has been dredged up by convection, planetary nebulae are important sources of galactic element enrichment for lighter elements such as He, C, O, and N. https://octodon.social/media/FtEHSBlX_bnS2tDZJoM
Though we generally say stars the mass of the Sun and larger turn into planetary nebulae at the end of their lives, the exact cut-off point isn't well understood and is in the range of ~1.0-1.2 solar masses. So the Sun may or may not become a planetary nebula. https://octodon.social/media/P5qqPVyaiHj8GCUyGm8
