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Dr. James O'Donoghue Profile picture
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20 Dec, 5 tweets, 2 min read
TOMORROW Jupiter and Saturn will be at their closest separation in the sky since 1623 at 0.1° apart. Here's an animation showing exactly how close that is relative to a familiar object, the Moon! (Moon ONLY added to illustrate the scale) #GreatConjunction2020
You DO NOT want a configuration of the solar system in which the giant planets go infront of our Moon. Here's the video in 1080p:
Here's a previous video which tracks them closely. You can see moons too, although might to turn screen brightness up or use the youtube version
Here's a new version in which the camera and Moon are held fixed, so you can see the proper motion of the planets

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Dr. James O'Donoghue Profile picture
20 Dec
The moment Jupiter and Saturn are closest in the sky on 21 Dec 2020

Los Angeles: 09:43
New York: 12:43
Rio de Janeiro: 14:43
London/UTC: 17:43
Paris/CET: 18:43
Istanbul: 20:43
Dubai: 21:43
New Delhi: 23:13
Tokyo: 02:43 (22 Dec)
Sydney: 04:43 (22 Dec)
(+/- minutes; see thread)
+/- minutes because the size of the Earth, and its rotation, means different places will have a *very slightly* different line of sight at Jupiter and Saturn. E.g. London sees the gap close at 17:43, while Auckland, New Zealand sees it on 17:39 (UTC). London times were used above
It is probably why you don't see many folks being exact, or why you might see different values out there. Details can be a pain, I'd have liked to just quote a time for everyone, but they are interesting
Read 4 tweets
Dr. James O'Donoghue Profile picture
19 Dec
On 21 December Jupiter and Saturn will be at their closest separation in the sky since 1623, at just 0.1° apart! In this new to-scale animation I follow the mid-point between them in the sky #GreatConjunction2020
Feel free to use this video wherever, no need to ask permission. On twitter it's 720p (and less, when it buffers). Here on youtube it's 1080p:
Here's one with a familiar scale added...
Read 4 tweets
Dr. James O'Donoghue Profile picture
3 Oct
Here's what it looks like when one galaxy passes right through another. The galaxy on the right has an expanding ring of stars (like a shockwave), while the other has been stretched out! And do forgive the low resolution of the image, these are 500 million light years away.
When the left galaxy passed through, the right galaxy would have been attracted to its own center due to the extra gravitational pull. After collisiding, the ring of material then expanded back out, likely because it still has orbital velocity and can escape its new, weak center
As with most galaxy collisions, the probably of a star-on-star collision is low, but I can imagine a lot of disturbed rocks flying around. Any advanced civilizations in the these galaxies probably have excellent astronomy funding
Read 5 tweets
Dr. James O'Donoghue Profile picture
30 Sep
PSA: @ScienceWithJen is very likely a fake account. They used several accounts in just 2020, claiming to work at spaceX (until their account was reported & closed). Jobs claimed just in 2020: aerospace/engineering/flight ops, but all with an astrophysics masters degree.
I suspected this in 2019 and since then numerous new examples of fakery keep coming in: people have DM'd to tell me about it from large space agencies. In the last week they moved over to a new account once again, and anyone asking Qs to them about it gets blocked
They've been getting away with it for a long time by deleting all their previous tweets, making new accounts, but perhaps most importantly, blocking people who ask qustions. They have zero online presence at any agency they claimed to work in, it would be so easy to prove they do
Read 6 tweets
Dr. James O'Donoghue Profile picture
24 Sep
I have an science/art video idea but I don't have time to make, so I'll share it here if someone else is interested:

What if we had a video sequence that displayed 180 galaxies one after another, similar to below (cred: edd.ifa.hawaii.edu/inclination/in…), but in 1° inclination increments Image
If a galaxy astronomer out there knows of a good table/database of galaxies which can be sorted by inclination, that would be a great first step: please let me know and I'll link it in this thread. I had a look around and didn't see much like that
Perfect! Galaxy expert @styrofoamplates just lent his expertise, that was fast!

Here's how to access the database that can sort galaxies by inclination (I suppose next step would be to find the galaxy images based on their names and download them, etc!)
Read 7 tweets
Dr. James O'Donoghue Profile picture
22 Sep
It's Equinox in 1 hour! 22 Sep 2020, 13:30 UTC. Today everywhere has an almost** equal day and night length of 12 hours, while sunlight is at max intensity on the equator. Earth has seasons because of its axial tilt, which leads to day/night length changes throughout the year
**At equinox daylight always lasts OVER 12 hours, for everyone! But why?
1) Sunrise/set time is based on the edge of the Sun, not the middle.
2) Atmospheric refraction means light bounces around the Earth and shows up earlier than sunrise AND later than sunset
Both mean more 🌞! Image
Here are the southern hemisphere season names and values for 45° south latitude

And, if you want to find out what time equinox is for your location:
timeanddate.com/worldclock/fix…
Read 5 tweets

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