Sky & Telescope

@SkyandTelescope

The Essential Guide to Astronomy | We provide the world's leading compendium of information about the science and hobby of astronomy.

Cambridge, Mass.
Vrijeme pridruživanja: ožujak 2009.

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  1. The shadow cast by a protoplanetary disk takes the shape of a bat — and over time, flaps like one, too, yielding clues to the planet-forming material in the disk. Click the link to see the video.

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  2. 2. velj

    The sky's biggest asterism (informal star pattern) is the Winter Hexagon, filling the sky toward the east and south these evenings. Wave high to the Moon shining near Aldebaran Monday night. The Pleiades are farther on the Moon's opposite side.

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  3. 31. sij

    Orion small compared to his neighbors. The biggest of these is Eridanus the River to his right. Fornax the Furnace, to Eridanus's lower right, is as big as Orion! Lepus isn't much smaller than he is. How many of these constellations can you spot tonight?

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  4. 31. sij

    Astronomers have used observations of a tight white dwarf-neutron star pair to confirm an aspect of Einstein's general theory of relativity.

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  5. 30. sij

    NASA’s premier eye on the infrared sky is shutting down on January 30th, after operating more than three times longer than designed.

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  6. 30. sij

    The Daniel K. Inouye Solar Telescope has taken its first image of the Sun, a detailed view of our star's boiling gases that far surpasses what was possible before. Science operations are set to begin later this year.

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  7. 30. sij

    Fresh, new sights animate the night as Betelgeuse continues to fade.

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  8. 29. sij

    Check out NASA's amazing 3D models including the supernova remnant of Tycho in VR .

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  9. 29. sij

    Concerns about the night sky remain as the fourth batch of Starlink satellites — and the second one to be launched within the span of a month — takes flight.

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  10. 27. sij

    Clouds of star-forming gas trace a long, mysterious ripple through the Milky Way, upending our picture of the Sun's neighborhood.

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  11. proslijedio/la je Tweet
    27. sij

    10/10 If you want to learn more, check out the webpage below. It contains lots of examples of atmospheric optical phenomena. My favourite part is how haloes would look like in other planets due to ice crystals of different shapes and compositions.

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  12. proslijedio/la je Tweet
    27. sij

    9/ Facets at 120º are special, because when the light beam hits the second facet it bounces back into the crystal. It’s like when you’re underwater in a swimming pool very close to the surface: you can’t see the outside, just reflections of what's under the water.

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  13. proslijedio/la je Tweet
    27. sij

    8/ This isn’t the only halo created by hexagonal ice crystals. The facets that are perpendicular to each other create a 46º halo, twice as large as the 22º one. But since light is more spread out, this halo is much harder to see; it’s fainter and has softer edges.

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  14. proslijedio/la je Tweet
    27. sij

    7/ Speaking of rainbows: did you notice that the inner part of the halo in my original image is somewhat red? That’s because ice crystals don’t bend red light as much as blue light, so the red halo is slightly smaller than at other colors.

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  15. proslijedio/la je Tweet
    27. sij

    6/ Same thing with rainbows: when you see one, you’re the only person in the world seeing that particular rainbow! Haloes and rainbows aren’t real images but virtual ones: they aren’t located at any specific distance. There’s not a pot of gold at the end of the rainbow, sorry!

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  16. proslijedio/la je Tweet
    27. sij

    5/ To be clear: crystals inside and outside the halo also refract light rays at 22º. You just don’t see them because they don’t travel in your direction. But they’ll reach someone else! Two observers side by side will see two different haloes.

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  17. proslijedio/la je Tweet
    27. sij

    4/ When light from the Sun / Moon go through a myriad of small ice crystals, most beams emerge at 22º, and you’ll thus see a bright ring of this size. The inside of the halo is dark because beams can’t be refracted at less than 22º.

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  18. proslijedio/la je Tweet
    27. sij

    3/ The red curve shows the deviation angle for any incident angle. There’s a minimum deviation angle at 22º: beams can’t be refracted at smaller angles. This minimum angle is also the most probable one: if you shoot beams at random angles, they’ll most likely come out at 22º.

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  19. proslijedio/la je Tweet
    27. sij

    2/ These haloes are created by hexagonal ice crystals in the atmosphere. Incident light rays are refracted twice as they go through two faces of the crystals at 60º with each other. The beam then emerges at a certain deviation angle relative to the incident beam.

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  20. proslijedio/la je Tweet
    27. sij

    1/ Every once in a while clouds pay us an unwelcome visit at Paranal. This can ruin our observations, but on the other hand we can enjoy amazing Moon halos like this one I saw in November. Do you want to learn how these haloes form? Thread!

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