Posts from the ‘Stars’ Category
Tell ya what … today is just going to be home to a time-lapse trifecta, okay? Especially with all the Jonah Lehrer stress from earlier. I think we all need a chill-out moment.
NASA’s first images from Mercury and Gemini came this morning, then a gorgeous tour through the night skies as seen from the ISS. Now Knate Myers (who did the ISS video) has just posted this tour through the stars and sights of New Mexico.
Because of its low population density and minimal light pollution, New Mexico is a skywatcher’s paradise. Much of this video was shot at the Very Large Array, a field of radio telescopes in the middle of the state. Close to 6,000 photos went into this collection, and every one of them is a work of art. I especially like the part about halfway through where he turns off the rotation tracking equipment that follows the stars’ paths during the long exposures, and we get to see the trails extend across the heavens in concentric arcs.
HD, full scrizzle, have a great evening y’all!
Some beautiful time-lapse to start off your morning. Take the time to just relax and enjoy at least one of these videos.
From one of last week’s Astronomy Picture Of the Day:
Early morning dog walkers got a visual treat last week as bright stars and planets appeared to line up. Pictured above, easily visible from left to right, were the Pleiades open star cluster, Jupiter, Venus, and the “Follower” star Aldebaran, all seen before a starry background. The image was taken from the Atacama desert in western South America. The glow of the rising Sun can be seen over the eastern horizon. Jupiter and Venus will continue to dazzle pre-dawn strollers all over planet Earth for the rest of the month, although even now the morning planets are seen projected away from the line connecting their distant stellar sky mates.
While I was unfortunately unable to see this in person, I happened to go to the planetarium the other day and was shown this configuration by James Albury, co-host of PBS’s Star Gazers. It was all the fun of seeing it without the rolling out of bed at 5am!
10) Every star you see in the night sky is bigger and brighter than our Sun
Of the 5,000 or so stars brighter than magnitude 6, only a handful of very faint stars are approximately the same size and brightness of our Sun and the rest are all bigger and brighter. Of the 500 or so that are brighter than 4th magnitude (which includes essentially every star visible to the unaided eye from a urban location), all are intrinsically bigger and brighter than our Sun, many by a large percentage. Of the brightest 50 stars visible to the human eye from Earth, the least intrinsically bright is Alpha Centauri, which is still more than 1.5 times more luminous than our Sun, and cannot be easily seen from most of the Northern Hemisphere.
9) You can’t see millions of stars on a dark night
Despite what you may hear in TV commercials, poems and songs, you cannot see a million stars … anywhere. There simply are not enough close enough and bright enough. On a really exceptional night, with no Moon and far from any source of lights, a person with very good eyesight may be able to see 2000-2500 stars at any one time. (Counting even this small number still would be difficult.). So the next time you hear someone claim to have seen a million stars in the sky, just appreciate it as artistic license or exuberant exaggeration – because it isn’t true!
8) Red hot and cool ice blue – NOT!
We are accustomed to referring to things that are red as hot and those that are blue as cool. This is not entirely unreasonable, since a red, glowing fireplace poker is hot and ice, especially in glaciers and polar regions, can have a bluish cast. But we say that only because our everyday experience is limited. In fact, heated objects change color as their temperature changes, and red represents the lowest temperature at which a heated object can glow in visible light. As it gets hotter, the color changes to white and ultimately to blue. So the red stars you see in the sky are the “coolest” (least hot), and the blue stars are the hottest!
7) Stars are black bodies
A black body is an object that absorbs 100 percent of all electromagnetic radiation (that is, light, radio waves and so on) that falls on it. A common image here is that of a brick oven with the interior painted black and the only opening a small window. All light that shines through the window is absorbed by the interior of the oven and none is reflected outside the oven. It is a perfect absorber. As it turns out, this definition of being perfect absorbers suits stars very well! However, this just says that a blackbody absorbs all the radiant energy that hits it, but does not forbid it from re-emitting the energy. In the case of a star, it absorbs all radiation that falls on it, but it also radiates back into space much more than it absorbs. Thus a star is a black body that glows with great brilliance! (An even more perfect black body is a black hole, but of course, it appears truly black, and radiates no light.)
6) There are no green stars
Although there are scattered claims for stars that appear green, including Beta Librae (Zuben Eschamali), most observers do not see green in any stars except as an optical effect from their telescopes, or else an idiosyncratic quirk of personal vision and contrast. Stars emit a spectrum (“rainbow”) of colors, including green, but the human eye-brain connection mixes the colors together in a manner that rarely if ever comes out green. One color can dominate the radiation, but within the range of wavelengths and intensities found in stars, greens get mixed with other colors, and the star appears white. For stars, the general colors are, from lower to higher temperatures, red, orange, yellow, white and blue. So as far as the human eye can tell, there are no green stars.
5) The Sun is a green star
That being said, the Sun is a “green” star, or more specifically, a green-blue star, whose peak wavelength lies clearly in the transition area on the spectrum between blue and green. This is not just an idle fact, but is important because the temperature of a star is related to the color of its most predominate wavelength of emission. (Whew!) In the Sun’s case, the surface temperature is about 5,800 K, or 500 nanometers, a green-blue. However, as indicated above, when the human eye factors in the other colors around it, the Sun’s apparent color comes out a white or even a yellowish white.
4) The Sun is a “dwarf” star
We are accustomed to think of the Sun as a “normal” star, and in many respects, it is. But did you know that it is a “dwarf” star? You may have heard of a “white dwarf,” but that is not a regular star at all, but the corpse of a dead star. Technically, as far as “normal” stars go (that is, astronomical objects that produce their own energy through sustained and stable hydrogen fusion), there are only “dwarfs,” “giants” and “supergiants.” The giants and supergiants represent the terminal (old age) stages of stars, but the vast majority of stars, those in the long, mature stage of evolution (Main Sequence) are all called “dwarfs.” There is quite a bit of range in size here, but they are all much smaller than the giants and supergiants. So technically, the Sun is a dwarf star, sometimes called “Yellow Dwarf” in contradiction to the entry above!
3) Stars don’t twinkle
Stars appear to twinkle (“scintillate”), especially when they are near the horizon. One star, Sirius, twinkles, sparkles and flashes so much some times that people actually report it as a UFO. But in fact, the twinkling is not a property of the stars, but of Earth’s turbulent atmosphere. As the light from a star passes through the atmosphere, especially when the star appears near the horizon, it must pass through many layers of often rapidly differing density. This has the effect of deflecting the light slightly as it were a ball in a pinball machine. The light eventually gets to your eyes, but every deflection causes it to change slightly in color and intensity. The result is “twinkling.” Above the Earth’s atmosphere, stars do not twinkle.
2) You can see 20 quadrillion miles, at least
On a good night, you can see about 19,000,000,000,000,000 miles, easily. That’s 19 quadrillion miles, the approximate distance to the bright star Deneb in Cygnus. which is prominent in the evening skies of Fall and Winter. Deneb is bright enough to be seen virtually anywhere in the Northern hemisphere, and in fact from almost anywhere in the inhabited world. There is another star, Eta Carina, that is a little more than twice as far away, or about 44 quadrillion miles. But Eta Carina is faint, and not well placed for observers in most of the Northern hemisphere. Those are stars, but both the Andromeda Galaxy and the Triangulum Galaxy are also visible under certain conditions, and are roughly 15 and 18 quintillion miles away! (One quintillion is 10^18!)
1) Black holes don’t “suck”
Many writers frequently describe black holes as “sucking” in everything around them. And it is a common worry among the ill-informed that the so-far hypothetical “mini” black holes that may be produced by the Large Hadron Collider would suck in everything around them in an ever increasing vortex that would consume the Earth! “Say it ain’t so, Joe!” Well, I am not Shoeless Joe Jackson, but it ain’t so. In the case of the LHC, it isn’t true for a number of reasons, but black holes in general do not “suck.”
This not just a semantic distinction, but one of process and consequence as well. The word “suck” via suction, as in the way vacuum cleaners work, is not how black holes attract matter. In a vacuum cleaner, the fan produces a partial vacuum (really, just a slightly lower pressure) at the floor end of the vacuum, and regular air pressure outside, being greater, pushes the air into it, carrying along loose dirt and dust.
In the case of black holes, there is no suction involved. Instead, matter is pulled into the black hole by a very strong gravitational attraction. In one way of visualizing it, it really is a bit like falling into a hole, but not like being hoovered into it. Gravity is a fundamental force of Nature, and all matter has it. When something is pulled into a black hole, the process is more like being pulled into like a fish being reeled in by an angler, rather than being pushed along like a rafter inexorably being dragged over a waterfall.
The difference may seem trivial, but from a physical standpoint it is fundamental.
So black holes don’t suck, but they are very cool. Actually, they are cold. Very, very cold. But that’s a story for another time.
Streaks of psychedelic colors show the passage of cities below the International Space Station (ISS), airglow in Earth’s atmosphere and the circling motion of stars in this stunning new image from Expedition 31 Flight Engineer Don Pettit.
Pettit created the image by combining 18 long-exposure digital images taken with a camera mounted inside the ISS on March 16, 2012. Because of the limitations of digital imaging sensors, multiple exposures are needed to get such an image.
A beautiful picture. Just driving through space, we are.
Another Friday Time Lapse: Under the Namibian Sky
Fridays are good for many things. One of those is treating myself to a taste of my ongoing addiction: Bad-ass time-lapse films of stars and nature.
Here’s one courtesy of Phil Plait. It’s a long one, too, so get comfy … maybe make some popcorn? As he points out, the southern hemisphere locale it’s filmed in provides some unique sights for us northerners. And best of all? The video is annotated with labels of major constellations and starry sights!!
HD, full screen, you know we do.
(via Bad Astronomy)
Who doesn’t like slow-mo starscapes? Commence the popcorn!