March 2016: Skies Over Crestone

Filed under: Skies over Crestone |

by Kim Malville

The month of March has two eclipses, a total solar eclipse in Indonesia on March 8-9 and a partial lunar eclipse, two weeks later, on March 23. The lunar eclipse, which will not be dramatic, will be at its deepest at 5:45am. You should be able so sense that the moon looks a little strange, but nothing more. Jupiter rises around sunset and dominates the sky throughout the night. Mars rises about midnight and Saturn follows about an hour later. Venus rises in light of dawn at the start of the month.

March 8: Jupiter is in opposition to the sun in the constellation of Leo, below and to the left of Regulus.

March 13: The dread “spring forward” of daylight savings time starts at 2am.

March 19: It’s an early equinox this year. The sun crosses the celestial equator at 10:30pm MDT.

The Great Chasm of Charon

We can’t stay away from Pluto. Let’s face it, Pluto is a fascinating dwarf, or rather double dwarf. Pluto has five moons, of which Charon is the largest. It is almost as large as Pluto itself, and hence it has been called a double dwarf planet. They are so close to each other that they are gravitationally locked together, each keeping the same face to the other. Thus, if you are on the moonless side of Pluto, you will never see its largest moon. All of its moons were probably formed by a modest collision early in the life of the solar system. That collision was not sufficient to produce high temperatures that would have evaporated its water, unlike our own moon which was produced in a hot collision that vaporized all of its water.

A recent analysis of images taken by the New Horizons spacecraft indicates that Pluto’s major moon, Charon, had an ancient ocean below its surface, which froze over time. The ocean was covered by a thick layer of ice, which initially protected the warmer interior. That frozen surface of water ice now has a temperature of -364° Fahrenheit, only 100° above absolute zero (-459.67°F). Today Charon has deep ridges, valleys and an immense chasm, deeper and longer than the Grand Canyon.  This subsurface ocean was kept warm when Charon was young by heat provided by the decay of radioactive elements, as well as Charon’s own internal heat of formation. As Charon cooled over time, this ocean froze and expanded (as water is wont to do when it freezes), lifting the outermost layers of the moon, ripping them apart to produce a surface looking very different from the crater-pocked dry skin of Earth’s moon (which never had such an ocean).

The ridges and chasms that formed on Charon are some of the longest and deepest found in the solar system. The rift known as Serenity Chasma (in the middle of the figure) is 1,100 miles in length and 4.5 miles deep. By contrast, Earth’s Grand Canyon is tiny, a mere 277 miles long and only one mile deep.

The discovery of gravity waves

When Einstein announced his theory in 1915, he rewrote the rules for space and time that had prevailed for more than 200 years. Newton had imagined a static and fixed framework of space and time. Instead, matter and energy distort the geometry of the universe in the way a heavy sleeper causes a mattress to sag. Consider yourself sharing an innerspring mattress with someone who tosses and turns, keeping you awake with bounces and shakes. That’s the same experience as when lines of space and time are jiggled by massive disturbances, causing ripples of gravity, known as gravitational waves.

The first version of the device that has detected gravity waves, known as LIGO, started in 2000 and ran for 10 years with two huge detectors: one in Hanford, WA, the other in Livingston, LA. The $272 million project was the most expensive ever funded by the National Science Foundation.

LIGO’s antennas are L-shaped, with perpendicular arms 2.5 miles long. Inside each arm, cocooned in layers of steel and concrete, runs the world’s largest a vacuum chamber a couple of feet wide. At the end of each arm are mirrors hanging by glass threads, isolated from the scratching of the crustal plates of the earth, the rumble of trucks, cars, and bicycles, and waves crashing on distant shores.

Thus protected, the lasers in LIGO can detect changes in the length of one of those arms as small as one ten-thousandth the diameter of a proton as a gravitational wave sweeps past the earth. Even with such extreme sensitivity, only the most massive and violent events out there would be loud enough to make the detectors ring. LIGO was designed to catch collisions of neutron stars and black holes. However, nobody knew for sure if black holes existed in pairs or how often they might collide.

On Sept. 14, the system had barely finished being calibrated and was in what is called an engineering run at 4am when a loud signal came through at the Livingston site. Seven milliseconds later, the signal hit the Hanford site. LIGO scientists later determined that the likelihood of such signals landing simultaneously by pure chance was vanishingly small. It had to be the scream of colliding black holes. One of the black holes was 36 times more massive than our sun, the other 29. For better or for worse, these spinning black holes were at a safe distance from us, 1.3 billion light years away. As they approached the end, moving at half the speed of light, they were circling each other 250 times a second. These strange objects reached within 130 miles of each other before colliding and coalescing. The result was a single black hole with the mass of 62 suns. In addition to the scream of the black holes, you can imagine the sigh of relief by the National Science Foundation. Their great scientific gamble paid off!

Lost in this collision were the masses of three suns, which were converted into gravitational waves. For a tenth of a second that energy (in the form of gravity waves) was brighter than all of the stars in all of the galaxies in the universe. The universe is so vast, it has taken 1.3 billion years for those waves, traveling at the speed of light, to reach Earth. The LIGO mirrors moved only four one-thousandths of the diameter of a proton, but it was enough to be detected by those marvelous LIGO machines. One take-away from this is that gravity waves are weaker than bouncing bed springs. The other is, don’t share your bed with a spinning black hole.

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