midtskogen wrote:

Source of the post Space grafitti is here

Yeah. :/   Know of any figures for how bright the flares from it actually are?  I see passes are already predictable on Heavens-Above, but no estimate for brightness.

Watsisname wrote:

Source of the post Know of any figures for how bright the flares from it actually are?

I don't know, but we can do a quick estimate.  Judging from the picture, each surface seems to have an area similar to a circle with a radius of ~12 cm.  Let's assume a distance of 200 km, that gives an apparent size of 0.000068755 degrees.  The Sun's apparent size is 0.5 degrees, so the diameters differ by a factor of 0.00013751 and hence the area by a factor of 0.000000018909.  If we assume perfect reflection, that translates into a magnitude difference of 20.7, so at 200 km distance the upper value for the brightness comes out as -6.

Good calculation!  -6th magnitude would pretty darn bright.  Iridiums can get brighter, but with this spinning and made up entirely of reflecting surfaces, it will sparkle with every (sun illuminated) pass.

The orbit is currently 288x518 km. Higher than I thought it'd be.  Brightest possible magnitude is -5 at 300km, or -4th at 500km.  The orbit will degrade over time, first mostly by decreasing the apoapsis until it's roughly circularized, then spiral downward until it finally burns up.  Apparently they expect this to take about 9 months...

The spin will probably make it difficult to predict the flashes.  Also, reflections will swipe over multiple locations due to its many faces.  This thing is really designed to be annoying.

9 months sounds too little if only drag will bring it down from 288-518 km.  But I don't know.

Luckily, satellites are moving too slow to be mistaken as meteors.  Meteors may come head on and have very low apparent speed, but this is very rare.  So satellites are not a big issue for out meteor detection.  In Norway one only has to look at the dark sky for a couple of minutes in order to see a satellite.  In Svalbard one can look at the sky at any moment and usually see a satellite straight away, sometimes multiple.  There are many satellites in polar orbit.  It's getting crowdy up there.

It kind of remind me of this.

The Martian rover Opportunity finally got around to taking a selfie. With its microscope! After 15 Earth years (including travel time) and 5000 Martian days we get to see it again. Surprisingly it hasn't been tagged with graffiti.

Apparently Cassini got pictures of ringshine on Saturn not long before the end of its mission.
https://www.nasa.gov/image-feature/jpl/ ... l-frontier

I found something interesting. Andromeda younger than earth?

https://www.youtube.com/watch?v=AfphA8oVsvg

Something else.

https://www.eurekalert.org/pub_releases/2018-02/uota-nrr022318.php

Starlight Glimmer wrote:

Source of the post I found something interesting. Andromeda younger than earth?

The study he's citing suggests that it was produced in a merger in the last few billion years.  So yeah, in the sense of being the product of a collision of previously existing galaxies, we could call it fairly young.  But in terms of the constituent stellar populations, it is much older.

I didn't know that. Pretty cool if you ask me!

That's amazing. 2 billion years ago is nothing. There was life on Earth, Eukaryotes were appearing for the fisrt time, and in the sky there were two galaxies merging. Since it's going to take 5-6 billion years for andromeda to traverse the 2 million light years beetwen us I immagine that 2 billion years means that this spectacle was ocurring not much farther away. The angular diameter of the merger in Earth's sky had to be almost the same as now

It would be interesting to know if one of the streams of the ejected stars from that merger points close to the Milky Way. Maybe we are going to be visited by Andromeda's stars much earlier than the actual collision between our galaxies.

These stars should have pass us already. To escape the Andromeda galaxy they would have to move about 500 kilometers per second.
That would move these stars about 3.3 million kilometers lightyears in two billion years.

I think you mean lightyears, not kilometers.

Of course.  Thank you.