Eternal shadows inside of Shackleton Crater on the lunar south pole.

Eternal shadows inside of Shackleton Crater on the lunar south pole.NASA

by Kim Malville

At the beginning of July, Jupiter will be the planet that dominates the southwestern sky in the evening, setting about 1am. Saturn will be at its highest at midnight and, off to the east, Venus will rise about two and a half hours before the sun.

July 1: In the southwest, the first quarter moon forms a large triangle with Jupiter and Spica. Perhaps you remember the guide: following the curve of the Big Dipper arc down to Arcturus (in the constellation of Bootes) and spike down to Spica (the brightest star in the constellation of Virgo).

July 3: On this hot day in the northern hemisphere, the earth reaches its greatest distance from the sun at 152,092,505 kilometers.

July 3-7: Early risers may get a view of Venus just below the Pleiades in the east.

July 6: Saturn appears about six lunar diameters below the moon.

July 9: Full moon

July 16: Last quarter moon

July 23: Dark moon

July 24: Look to the west some 30 minutes after sunset. The very slender young crescent moon may be visible just above the horizon and above it to the left you may be able to spot Mercury.

July 28: The moon will be about 6 lunar diameters above Jupiter.

July 30: First quarter moon

Gravity waves from two black holes.

Gravity waves from two black courtesy of LIGO team

Clanging Space-Time

The third well-documented detection of gravitational waves was announced this year on June 1. This is the most distant detection yet of the violent merging of two massive black holes, lying nearly 3 billion light years away from us. These detections by the LIGO (Laster Interferometer Gravitational Wave Observatory) are tours de force of both observation and theory. Not only are the effects tiny, but the ability of theoretical physicists to interpret them are truly extraordinary. These ripples in space and time changed the length of a 4-km LIGO arm by a ten thousandth of the width of a proton, equivalent to changing the distance to the nearest star outside the solar system by the width of one human hair’s width. Two black holes, far more massive than our sun, whirled around each other, spinning faster and faster, reaching speeds of more than half the speed of light. When they merged a burst of energy was generated, spreading out into the universe like ripples in our cosmic pond. When they reached Earth in January they were detected as tiny vibrations in the arms of LIGO in Louisiana and Washington state. The two black holes were 31.2 and 19.4 solar masses. The resulting single black hole had a mass of 48.7 solar masses. That means that within a very slim fraction of a second an object nearly twice the mass of the sun was destroyed and converted into energy.

The first and second detections of merging black holes were located about 1.3 billion and 1.4 billion light-years away, making this the farthest yet. The collision in the first detection produced a new black hole of 62 solar masses, and the second 21 solar masses. The presence of such huge black holes is shocking and very puzzling. In the past, it seemed that a black hole could be created by the explosion of a single star, a super nova, which should have a mass more than perhaps 7 times that of the sun.  How they got so massive is a great puzzle. Furthermore, the thought of huge dark black holes wandering through our galaxy gobbling up stars and planets that come near can be truly disconcerting for those who like worry about such things.

LIGO is currently in the middle of an observation run that began last November and will continue through this summer. Its next run is scheduled to begin in late 2018 and will have enhanced sensitivity, which could reveal more collisions between black holes or collisions between black holes and neutron stars. With even more sensitivity, LIGO-like detectors might be able to detect the collisions of primordial black holes, possibly abundant chunks of matter that formed in the early universe that may have less mass than the sun. There also may be exotic black holes made of dark matter. In addition, most galaxies have vast black holes in their centers containing millions of solar masses. If, as the result of a collision of galaxies, these huge objects were to merge, the universe would be lit up with gravitational energy.

Artist’s conception of tumbling black holes.

Artist’s conception of tumbling black holes.MIT

Water for thirsty astronauts

Shackleton is an impact crater that lies only a few miles from the south pole of the Moon. The peaks along the crater’s rim are exposed to almost continual sunlight, while the interior is perpetually in shadow (a Crater of eternal darkness). The low-temperature interior of this crater functions as a cold trap that may capture and freeze volatiles shed during comet impacts on the Moon. Measurements by the Lunar Prospector spacecraft showed higher-than-normal amounts of hydrogen within the crater, which may indicate the presence of water ice. The crater is named after my favorite Antarctic explorer, Ernest Shackleton, who got close to but never reached the south pole of the earth.

The walls of the crater keep its interior in perpetual darkness. Because the peaks of the crater are so close to the pole, they are almost continually illuminated by sunlight. Thus, we have peaks of eternal light surrounding a pit of eternal darkness. As scary as that may sound, these peaks are perfect for solar panels, providing nearly continuous power to a future lunar base.

NASA has identified the rim of Shackleton as a potential candidate for a lunar outpost, projected to run by 2020 and continuously staffed by a crew by 2024. The location would allow self-sustainability for lunar residents, with sunlight on the south pole providing energy for solar panels. The floor of the crater could be mined for water, as well as hydrogen for fuel. Potatoes could be grown, and science fiction could become science fact!