Bakersfield Night Sky - October 21, 2018

Bakersfield Night Sky - October 21, 2018
by Nick Strobel

Tickets are on sale for “Dynamic Earth” and “Black Holes” that will be shown at the William M Thomas Planetarium with the new upgraded SciDome system. “Dynamic Earth” shows on November 1 and “Black Holes” shows on November 15. The new system puts up sixteen times the number of pixels onto the dome, so it will be a much sharper image. Both shows will begin with a tour of the night sky using the Goto Chronos.

The Japanese Aerospace Exploration Agency's (JAXA) Hayabusa2 mission to the small asteroid Ryugu continues its string of successes with the deployment of the MASCOT lander developed in Germany and France (“MASCOT” stands for “Mobile Asteroid Surface Scout”). There are great pictures showing the cube-shaped lander leaving the Hayabusa2 spacecraft and descending to the surface on the Hayabusa2 website.

The MASCOT used a mechanical swing arm to maneuver itself to just the right orientation for its four scientific instruments to do their burst of measurements before the battery ran out after 17 hours. That 17 hours was an hour longer than expected from the battery and the data collected on the gravitational and magnetic fields and chemical composition will keep scientists busy for months (at least). Because Ryugu rotates once every 7 hours 36 minutes, the MASCOT data collection lasted three days and two nights on the asteroid.

At the end of this month, the Hayabusa2 spacecraft itself will execute the first of three planned touchdowns on the asteroid to collect samples from the surface for eventual return to Earth. The third touchdown collection will be from a crater generated by an explosive impactor brought by Hayabusa2, so that we can get samples of subsurface material.

This past week nearly 200 Mars scientists gathered for the final Mars 2020 landing site workshop. Various teams have been poring over high-resolution images and remote-sensing data of three possible sites. All three sites have clear evidence of running water in the past and soil types that would have preserved signs of microbial life if it ever existed on Mars. One possible site is the Columbia Hills in Gusev Crater that was explored by the Mars Exploration Rover Spirit in the early 2000s. Another site is Jezero Crater which has a fossil river delta with layers of carbonate material. The final site is Northeast Syrtis that had mineral springs and also formed layers of carbonates. On Earth, the same type of carbonate layers are often home to microbial colonies, including stromatolites.

Further out in the solar system, it looks like Voyager 2 will finally join its sister craft, Voyager 1, in interstellar space within the next few months. This boundary of the solar system is determined by the strength of the sun's magnetic field compared to the interstellar magnetic field. The Sun produces a magnetic bubble around itself that keeps out the high-energy charged particles (plasma) produced by other stars as they live and die (including supernovae). Inside of that bubble lies all of the planets and dwarf planets. The Sun's magnetic field is carried outward by the solar wind, charged particles from the Sun flying outward, away from the Sun at a million or so miles per hour. Eventually, the pressure outward by the solar wind is matched by the interstellar pressure. At about 11 billion miles from the sun, Voyager 2 is seeing an increase in cosmic rays, so we know Voyager 2 is reaching the boundary. At that distance it takes about 16.5 hours for Voyager 2's radio signal to travel to Earth.

Another boundary of the solar system is determined by the strength of the sun's gravitational field compared to other stars. That boundary is MUCH farther out than the magnetic bubble boundary—about 12 trillion miles from the sun, or a thousand times farther out than where the two Voyager spacecraft are now. Voyager 1's radio signal takes about 20 hours to reach us. At the gravitational boundary, a radio signal would take two YEARS to reach us but the Voyager will run out of power long before they get to that distance.

Compared to interstellar distances, the Voyager spacecraft are actually quite close. If you scale the solar system so that Pluto's orbit fits within a quarter coin, then Voyager 1 is about 1.8 quarters from the sun, Voyager 2 is about 1.5 quarters from the sun, the closest star to the sun is about 82 meters away (a meter is one big step). Go to the Voyager homepage to see the current status of the two spacecraft.

In the supermassive black hole research front, a research team led by Stephane d'Ascoli and Manuela Campanelli released a video of the supercomputer simulation showing what two merging supermassive black holes (with millions to billions of times the mass of the sun) would look like from various angles. The simulation shows how the ultraviolet and X-ray light from the disks of hot gas surrounding each black hole would be warped as it passes through the intensely warped spacetime around the black holes. The most dramatic effect is seen if we see the system edge-on, so one black hole passes in front of the other.

Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website