Jason Nishiyama @evilscientistca@octodon.social
Teacher, astronomer, political scientist and father.
M78 is a reflection nebula, that is we see it because light is being reflected off the nebula from a nearby star. This is the cause of it looking blue as the blue light is selectively scattered back to us while the red light mostly goes through and we don't see it.
Frosty telescope after a night of work.
https://octodon.social/media/YehWoZ7HV1f43IMxi5g
It's a good thing I'm imaging the last filter. I've run out of hot chocolate...
Also sort of hot off the telescope (processing takes time...) the reflection nebula M78. 0.2m f3.9 Newtonian telescope. LRGB image. 5 minutes each R, G, and B. 8 minutes L. https://octodon.social/media/8nRGNYWakrGnCt5f95M
Now NGC 2022 with the [SII] filter. The brackets mean that this is a "forbidden" line, that is one that only happens if the singly ionized sulphur is in near-vacuum.
Still observing NGC 2022, now with H-Alpha filter.
Now NGC 2022, B filter.
Still on NGC 2022, now filter R.
Collecting data on target NGC 2022. Current filter: G
The planet Uranus hot off the telescope. RGB image, 3 seconds each filter. 0.2m f3.9 Newtonian telescope with 2.5x barlow lens. https://octodon.social/media/jO_dMn3iqEQtESZmmvw
Feels so good when you finally get the math to work.
So our 24 hour day is merely the average time it takes for the Sun to go from the meridian to the meridian, hence mean solar time.
This is different from the time it takes for the Earth to make one rotation on its axis which is 23 hours, 56 minutes and 4 seconds, the sidereal day.
What we call a day is the time it takes the Sun to be on the meridian till it's there again the next day (meridian to meridian) is 24 hours. Except it's not. 24 hours is the average time for this to happen.
As the Earth moves in its orbit it speeds up and slows down. This changes the amount of time it takes for the Sun to return to the meridian. This can change nearly 15 minutes either faster or slower than a clock will time the period depending on where in the Earth's orbit it is.
To be honest 1 January never really feels like a new year to me unlike the 1st of September.
One could also measure a year from perihelion to perihelion (closest approach of the Sun by the Earth in it's orbit). As this too precesses the length of this anomalistic year is 365.259635 days.
Happy new year everyone!
The year we use is the tropical year. This is measured from equinox to equinox and is 365.24219 days in length. Contrast this to our Gregorian calendar year which averages out to 365.2425 days.
The actual time it takes to make one orbit of the Sun is the sidereal year as measured from fixed star to fixed star. This is 365.2526363 days. This difference is due to the precession of the equinoxes.
In honour of the icy temperatures, ices in space. Comets are made up basically of ices (water, methane, etc.) and rocks. Their tail forms as they near the Sun and the ices melt and are blown back by the solar wind and radiation pressure. https://octodon.social/media/L6JkntBblGPmh6ti_NQ
This Herbig-Haro objects are jets of nebulosity associated with a newly formed star such as in this Hubble image. https://octodon.social/media/juPx7_B_Fa3-IBiw3kQ
Earth’s axis of rotation is tilted about 23 degrees from perpendicular to the plane of its orbit, giving us our seasons. Uranus’ poles are tilted nearly 98 degrees so it is rotating on its side. Imagine the seasons there!
The thing to remember for those of us currently under a mass of arctic air, the Earth is actually closer to the Sun at this time of year than in July when we are the farthest from the Sun.
