The Kraansvlak herd of bison or “wisent” have free run of quite a large area of the dunes & are monitored as part of a rewilding research project. Despite the old idea that they’re predominantly forest animals, they do very well in this setting.
Some of the bison are fitted with GPS collars & you can check this map to see where they are. I did that when I reached Zandvoort, saw that some were close to one of the bike paths that go through the park, so I went looking.
One of them was standing high on a dune close to the fence & I was thrilled, but before I could get my phone out, it saw me & wandered down behind the dune. I heard it mooching around in a little lake, but couldn’t see it. Then it & another emerged, so I grabbed a shot.
In the winter, it’s possible to walk through their fenced-off park, but between 1 March & 1 September, it’s closed off as they get territorial. They’re very big & can be dangerous. So I was lucky this evening that these were near the fence & bike path 👍
And to finish, here’s a little bit of video showing them slowly ambling off into the dunes. I’m not sure how large the full herd is: 20-30, I think, but it changes as they exchange bison with other projects around Europe.
p.s. This location is within a kilometre of the north end of the Zandvoort race track, so probably gets a noisy when petrolheads like @DrCaplin are there, as she was earlier today.
I thought of her when I saw a smashed up Ferrari road car being trucked away from the track 🤷♂️
• • •
Missing some Tweet in this thread? You can try to
force a refresh
The authors have ruled out the latter by suggesting that a star in our own galaxy would likely have moved a bit in the 3.5 years since its discovery.
Perhaps, but in a semi-random distribution of motions, not all stars move tangentially; some will move mostly radially.
That’s the problem with the detection of a single object – statistical arguments about the possibility of finding such & such an object right at a given spot are not always going to be kind to you. It depends on how many places you’ve looked for such objects as well.
A few hours from now, #JWST will make its Mid-Course Correction 2 (MCC-2) burn, injecting it into its operational orbit around the Sun-Earth L2 point, ~1.5 million kilometres away.
What, why, how, when?!
A thread.
1/
First, a reminder: #JWST was launched on #Ariane5#VA256 from Europe's spaceport in French Guiana on 25 December 2021. The #Ariane5 put it on a near-perfect trajectory towards L2 & two subsequent JWST Mid-Course Corrections have tweaked that.
2/
But why such a long journey to a place that's about four times further away from Earth than the Moon?
By contrast, the Hubble Space Telescope is in a low Earth orbit ~535km above the surface, making it accessible to several servicing missions over the past 31 years.
As the start of the last major #JWST deployment approaches, the starboard primary mirror wing, it's time for a thread about what that helps enable – excellent spatial resolution.
It's #SharpnessSaturday (yes, the hashtag symbol also denotes a "sharp" in music 🙂)
So what do we mean by "spatial resolution"?
It's a way of quantifying the sharpness of an image scene, the amount of detail visible at small scales, or at some rather fundamental level, how close two things can be in a scene & still be separated.
2/
For astronomers, that's often simplified to saying "how close can two stars of equal brightness be on the sky & still separable or resolvable?"
That's not to say the stars need actually be close in space, but just how they appear on the sky.
3/
And … as one third of you got right, the correct answer is “Glass” 🙂
Yes, even though the beryllium mirrors of #JWST are coated with a highly infrared reflective 100nm layer of gold, that in turn is coated with a thin layer of SiO2 (aka silica) to protect it from dings.
and thanks again to @apolitosb for posing the question. What we haven’t found out yet is how thick the SiO2 layer is – probably similar to the 100nm of gold, but more exactly … 🤷♂️
3/3
Today’s the day – #JWST starts spreading the wings around its eyes 👀
And yes, I know this joke would make more sense if this was a pit viper rather than a cobra, but they don’t have a deployable hood 🐍🤷♂️
1/
That is, cobras are members of the elapid family of snakes, whereas pit vipers, including rattlesnakes, are from the crotaline family.
And what pit vipers share with boas & pythons is an ability to sense the infrared, which cobras lack.
2/
Not with their eyes, but via specialised “pit organs” near their snout. These hold a thin membrane with many nerve endings & blood vessels: the former sense infrared light (aka heat) between 5 & 30 microns, & the latter cool the membrane to refresh it.