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Chris Dolan
programmer, cyclist, gamer, former astronomer
programmer, cyclist, gamer, former astronomer

Chris's posts

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This candidate Google Doodle was created by a 7th grader here in Madison, at Wright Middle School. Vote!

more info:

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I agree with the sentiments of +John Bowdre. I believe science is at its best when its humble and when scientists are excited to acknowledge past theories were wrong.

This very short article points out that a leading theory for Mars' liquid-water past -- heating due to a thick CO2 greenhouse effect -- is contradicted by surprising lack of carbonate rock in Curiosity's searches.

So, what instead caused Mars to be warm enough for liquid water in its ancient history? Far from my expertise, I don't know. But I'll certainly keep my eye open for alternative theories.

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This vanadium dioxide discovery has such cool (ha!) implications, especially because it's properties seem tuneable by mixing with other materials. Imagine transparent window glass that's thermally conductive above 65F and thermally insulating below.

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I agree with this. Vera Rubin should have gotten the prize before her death.
It’s been 53 years since a woman won the Nobel Prize in physics. What’s the holdup?
This is your annual reminder that it's been an embarrassingly long time since the Nobel Prize in Physics was awarded to a woman. Only two women have ever won the prize: Marie Curie in 1903 and Maria Goeppert-Mayer in 1963. One of the most puzzling snubs is Vera Rubin, whose work measuring galactic rotation speeds convinced scientists that most of the matter in the universe comes in the form of dark matter.

Rubin and her colleague Kent Ford did their research in the 1960s and 1970s. For comparison, the three scientists who discovered dark energy, another major component of the universe, snagged a Nobel 13 years after their pivotal work. There are plenty of other accomplished women physicists who so far have been passed over for the prize, including Lene Hau, Helen Quinn, and Mildred Dresselhaus.

Interesting reading via The Washington Post

#physics   #nobelprize   #history   #womeninstem  

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Excellent scale comparison of the biggest sub-planet bodies in our solar system
Ladies and gentlemen, the not-planets of our solar system:

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Brilliant! So simple in retrospect! Anything 240 km/sec slower than us (in the direction of our motion in the milky way) would not be orbiting but would instead be falling. So of course there's no stars at that speed
"Using a novel method and data from the Gaia space telescope, astronomers from the University of Toronto have estimated that the speed of the Sun as it orbits the centre of the Milky Way Galaxy is approximately 240 kilometres per second.

In turn, they have used that result to calculate that the Sun is approximately 7.9 kiloparsecs from the Galaxy's centre—or almost twenty-six thousand light-years.

Using data from the Gaia space telescope and the RAdial Velocity Experiment (RAVE) survey, Jason Hunt and his colleagues determined the velocities of over 200,000 stars relative to the Sun. Hunt is a Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics, University of Toronto.

The collaborators found an unsurprising distribution of relative velocities: there were stars moving slower, faster and at the same rate as the Sun.

But they also found a shortage of stars with a Galactic orbital velocity of approximately 240 kilometres per second slower than the Sun's. The astronomers concluded that the missing stars had been stars with zero angular momentum; i.e. they had not been circling the Galaxy like the Sun and the other stars in the Milky Way Galaxy;

"Stars with very close to zero angular momentum would have plunged towards the Galactic centre where they would be strongly affected by the extreme gravitational forces present there," says Hunt. "This would scatter them into chaotic orbits taking them far above the Galactic plane and away from the Solar neighbourhood."

"By measuring the velocity with which nearby stars rotate around our Galaxy with respect to the Sun," says Hunt, "we can observe a lack of stars with a specific negative relative velocity. And because we know this dip corresponds to 0 km/sec, it tells us, in turn, how fast we are moving."

Hunt and his colleagues then combined this finding with the proper motion of the supermassive blackhole known as Sagittarius A* ("A-star") that lies at the centre of the Galaxy to calculate the 7.9 kiloparsec distance.

Proper motion is the motion of an object across the sky relative to distant background objects. They calculated the distance in the same way a cartographer triangulates the distance to a terrestrial landmark by observing it from two different positions a known distance apart.

The result was published in Astrophysical Journal Letters in December 2017."

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More cool work by my friend Chip Kobulnicky. Bow shock nebulae happen when outflow from a star (stellar winds usually) collide with the surrounding gas. If the star is moving in a particular direction, the wind-gas collision is stronger in the direction of motion, like the bow wave of a boat. Arcs like these can have other explanations (like asymmetric flows or non-uniform ambient gas) but most are likely "runaway" stars that are moving unusually fast.

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This animation is so exciting! It's a 6-year timelapse of planets orbiting around another star. The star at the center is mostly-blocked by a mask to keep it's brightness from washing out the picture.

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So cool! The image raster used double-floats per pixel, but the grayscale output only needed ~5 integer bits per pixel. So the author used the less-significant bits to hide another image. And another beneath that. And another. And so on. The less-significant images were truncated away when rendered.

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