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Arthur Maltson
Attended University of Toronto
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Arthur Maltson

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That's going to be exciting!
 
Seven key facts about our Cassini spacecraft's Wednesday flyby through a plume of icy spray of Saturn's moon Enceladus: http://go.nasa.gov/1P1qVoO #NASABeyond
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Good tips
 
Step #1: Learn from a pro. Our senior photographer gives tips on how to capture the best images of this weekend’s #SuperBloodMoon. Start learning: http://go.nasa.gov/1LTYlRr
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Using Lasers to Un-twinkle the Stars

If you’ve ever looked up in the night sky you’ve seen the twinkling of the stars. This twinkle is not due to the stars themselves, but to the turbulent motion of the Earth’s atmosphere. As starlight enters our atmosphere, the variations in density in turbulent air cause the light wave fronts to distort. This wobbly behavior is why stars appear to twinkle. While twinkling makes stars pretty to look at, it also blurs astronomical images, making it difficult to observe things in fine detail. Fortunately we have a technique that can basically un-twinkle the stars, known as adaptive optics.

The basic idea of adaptive optics is to continually adjust the focus of your mirror to compensate for the effects of the atmosphere. As the atmosphere distorts your image, you distort the focus in the opposite way to keep things in focus. The main way this is done is by using a tip-tilt mirror to realign the image, or if the mirror is segmented (as many modern large telescopes are), adjust each segment to correct for the distortion. If you’ve ever used noise-canceling headphones, you’ve experienced a similar process with sound. The difference is that the headphones create inverted sound waves to cancel background noise.

Of course for this process to work you have to be able to distinguish between distortion caused by the air and any real variance in what you are observing. This is where the laser comes in. It turns out that about 100 kilometers above the Earth’s surface there are small amounts of sodium in the air. By using a finely tuned sodium laser you can excite these atoms so that they glow. Since the laser focuses on a tiny patch of sky, the glowing sodium looks like a star, and since 100 km is higher than most of the Earth’s atmosphere, the distortion of the sodium’s glow is about the same as the distortion of star light.

This gives the adaptive optics a point of reference. By keeping your artificial star in focus you can keep your image in focus. With adaptive optics and a simulated star ground-based telescopes can obtain images that rival those of a space telescope. Without adaptive optics, large ground-based telescopes would be limited by the atmosphere. As we build ever larger telescopes, such as the Thirty Meter Telescope under construction in Hawaii, advanced adaptive optics are a necessity.

Adaptive optics doesn’t solve all the problems with ground-based astronomy. For example, our atmosphere absorbs several wavelengths of light, and the only way to observe those wavelengths is through space-based observatories. But adaptive optics has allowed us to push the limits of ground-based astronomy much further than we once imagined.
While twinkling makes stars pretty to look at, it also blurs astronomical images. But we have a way to un-twinkle the stars, known as adaptive optics.
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Twenty years ago was the first confirmation of a planet orbiting a star outside our solar system. This discovery launched a whole new field in astronomical research. Today, there are more than 1,800 confirmed planets outside our solar system. Details: http://go.nasa.gov/1Ud87Eu #NASABeyond
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Pluto has sent a love note back to Earth via our New Horizons spacecraft, which has traveled more than 9 years and 3+ billion miles. This is the last and most detailed image of Pluto sent to Earth before the moment of closest approach, which was at 7:49 a.m. EDT today. Images from the #PlutoFlyby will be processed and released on Wednesday, July 15. More to come! 
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Arthur Maltson

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I always wondered if there a way to opt out of the religious text, apparently there is.
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I was just wondering this today.
 
Why Does Autumn Begin On Different Days?

Today is the first day of Autumn (or the first day of Spring for those in the southern hemisphere). This year it happens to fall on September 23, but that date can vary from the 21st to the 24th. So why doesn’t Autumn begin on the same day every year?

It all has to do with our swiftly tilting planet. The marking of Fall traditionally comes with the equinox, when the Sun’s path through the sky takes it from rising due East to setting due West. Since our seasons are caused by the tilt of Earth’s axis relative to its orbital plane, the equinox roughly marks the transition from longer periods of daylight to shorter ones or vice versa. The Earth’s axis remains fairly constant relative to the stars as it orbits the Sun, so its orientation relative to Sun changes over a year. So it would seem that the Autumnal Equinox should begin on the same day every year.

But the problem is that a solar year isn’t an exact number of days. Typically we consider 365 days to be a year, but a solar year is actually 365.2421897 days long. So a typical calendar year is a bit shorter than a solar year, and leap years are a bit longer. Because of this mismatch we’ve had to modify and refine our calendars over the centuries.

Since we can’t align a solar year with an integer number of days, there will always be a bit of drift between our calendar days and the day of the equinoxes and solstices. But even if a solar year happened to be exactly 365 days, over the centuries the marking of the seasons would still drift relative to the calendar year. While the Earth’s axis is fairly constant relative to the stars, it isn’t exactly constant. Over time the Earth’s axis precesses due to gravitational interactions with the Sun and Moon, causing Earth to wobble a bit like a top. Over geologic time scales the seasons can shift significantly.

So enjoy your first day of Autumn. The next one will occur on September 22, 2016.
This year Autumn begins on September 23, but that date can vary from the 21st to the 24th. So why doesn't Autumn begin on the same day every year?
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Great visual
 
Pluto images: before and after (Hubble vs New Horizons)
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If only they went quiet...
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Have him in circles
129 people
Kate Malt's profile photo
Mike Wilkes's profile photo
Fred Fiene's profile photo
Egan Done's profile photo
Etienne Neveu's profile photo
Sorin Aghinitei's profile photo
Виктор Каленский's profile photo
Ksenia Vanin's profile photo
Olivier Turpin's profile photo
Education
  • University of Toronto
    2007
Work
Occupation
Software Developer
Employment
  • Software Developer, present
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