Nova Newsletter – Nov/Dec 2016

Our NOVA Newsletter, for Nov-Dec 2016, is available as hi-res or low-res pdf files.   An archive of older issues can be found on our Newsletter page.

Contents of Volume 2016, Issue 6, Nov-Dec:

  • A Summer Night Under Perseus’ Shower by Leigh Cummings and Elena Popovici
  • President’s Message by Suzanna Nagy
  • Target for Tonight: Alsatia Niner Seven One, Pt. 1 by Dan Collier
  • Cosmic Rays in the Classroom by Francesca Crema
  • The Library is Open for Business by Suzanna Nagy
  • Richmond Public Library Science Bash by Jeremy van den Driesen

Ceres Just Past Opposition

Ceres with Brights Spots in Occator Crater.
Ceres with bright spots within the Occator Crater. Image credit: NASA’s Dawn spacecraft on Feb. 9th from a distance of nearly 46,000 kilometres.

It is a good time to try to observe the dwarf planet Ceres as it is just past opposition and is located between the constellations Cetus and Pisces. The clear sky clocks don’t look favourable over the next few days but if the clouds part then take a look towards the south about 30 degrees above the horizon around midnight. If it remains cloudy read on to learn more about the Ceres.

Ceres is, by far, the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter. Like Pluto, Ceres was originally classified as a planet shortly after it was discovered in 1801 by Italian astronomer Giuseppe Piazzi. It was “demoted” to an asteroid (“star-like” object) by William Herschel in 1802, and was classified, along with Pluto, as a dwarf planet in 2006.

NASA’s Dawn spacecraft went into orbit around Ceres in March 2015. Images from Dawn, as it approached Ceres highlighted bright white spots, within the Occator Crater whose composition puzzled scientists. Recent studies of spectroscopy data sent back by Dawn have indicated the presence of ammonia-rich clays. This suggests that Ceres may have formed in the Kuiper belt, past Neptune, and migrated inward as ammonia-bearing salts have been detected in the outer solar system such in the geysers of Enceladus (a moon of Saturn). Other studies conclude that recent geologic activity was probably involved in the creation of the bright spots.

Mount Ahuna Mons
Ceres’ Mount Ahuna Mons, is seen in this simulated perspective view. The elevation has been exaggerated by a factor of two. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

In Sept 2016, NASA scientists released a paper in Science that claims that Ahuna Mons is the strongest evidence yet for the existence of ice volcanoes. Cryovolcanoes are similar to regular volcanoes except they spurt out a mixture of salt and water rather than lava. The ejected salty water freezes and creates an icy dome at the top, which, for the NASA scientists is one of the telltale signs that Ahuna Mons is a cryovolcano.

Ahuna Mons appears to be quite young. It likely formed in the last 200 million years or so. In contrast, Ceres probably formed about 4.6 billion years ago like the rest of the solar system.

The heating process that leads to this cryovolcanism is not clear – Ceres doesn’t experience tidal heating; its insides are not heated by another object’s powerful gravitational pull as Ceres never gets close enough to a giant planet. So Ceres is again similar to Pluto in that the energy driving cryovolcanism must come from the dwarf planet’s internal heat, likely the heat left over from its long-ago formation along with some contribution from radioactive decay.

Other interesting facts:

  • Ceres was the first object considered to be an asteroid.
  • Plumes of water vapour shooting up from Ceres’ surface were observed by the Herschel Space Telescope.
  • Ceres accounts for one-third of the mass in the asteroid belt yet it is still the smallest dwarf planet.
  • Ceres is the only dwarf planet with no moons.

 

Track of Ceres after midnight from Vancouver, BC, Oct 2016

Search for Micrometeorites when Cleaning Your Gutters

Micrometeorite Images
Image Credit: A display of nine of the most spectacular micrometeorites from Jon Larsen’s collection

It is a good time to clean out your rain gutters before the fall rains start in earnest and you can slip in some astronomy by checking the debris for meteorites.   

We are familiar with meteors or shooting stars that leave streaks of light as they burn up in Earth’s atmosphere but 5 to 300 tons of space dust and debris hit the Earth’s surface every day. Impacts of large meteorites are rare but micrometeorites, those that are smaller than a grain of rice (50 µm to 2 mm in diameter) are quite common.  A rough estimate is that one micrometeorite lands in any square meter per year so your roof might bear a number of micrometeorites.  

The challenge is separating the micrometeorites from the other terrestrial debris and using a good magnet to pull out nickel and iron laden rocks is the key. An easy way to collect them is to place some strong magnets in a plastic bag and hang it near the outlet of the rain gutters. The magnet collects the nickel- and iron-laden micrometeorites, plus other magnetic debris,  as the rain washes them off the roof. The next step is to use a microscope to separate the good stuff: micrometeorites are spherical and have a glass coating formed as they heat up when passing through the Earth’s atmosphere.  

Micrometeorites and Debris Magnified
Image credit: Wayne Schmidt – The actual width of the area covered in this image is 1/8th inch

There is a good chance that some of the “micrometeorites” you’ll identify are actually formed in terrestrial processes that put particles with the appearance of micrometeorites into the air, such as volcanic eruptions or burning coal. Jon Larsen’s Project Stardust Facebook page has detailed tips on correctly identifying the micrometeorites. Hundreds of fascinating images of micrometeorites are included in his book “In Search of Stardust“.

Building An Inexpensive Artificial Star

Good collimation is important for getting the best performance from a telescope. I recently installed Bob’s Knobs on my Celestron SCT to help with collimation – mostly to reduce the risk of damaging the corrector lens when fumbling at night with a screwdriver. Unfortunately, installing the knobs put the telescope way out of collimation – it wasn’t just a minor mis-alignment, in-focus stars were comet shaped and the out-of-focus stars appeared as crescents rather than the desired donut pattern. I spent a couple of hours, over two nights, trying to improve the collimation to no avail but some Google searches and building an incredibly simple artificial star helped.

Flashlight with aluminum foil
An Inexpensive Artificial Star from a bike light and aluminum foil.

An artificial star is a small point of light that is used for collimation or optics testing. With an artificial star, collimation can be done during the day and doesn’t require clear skies or good seeing conditions. Artificial stars are available commercially from $25 USD but a precision artificial star is not required for rough collimation so I “built” one for free using a bike light and aluminium foil.

I started by poking four small holes in a piece of aluminium foil with a sewing needle while varying the pressure to produce holes of different sizes. The foil was then wrapped around a bright MEC bike light and secured with a rubber band.

startest_collimation_in_tweaked
The donut pattern on a out-of-focus real star after tweaking collimation.

I set up the telescope on its mount in my yard and aimed it at the artificial star which was placed on on barrel about 20 meters away. The second largest hole produced the best image when viewed through the telescope so I put a bit of tape over the other holes to block them out then followed these instructions to restore rough collimation in about ½ hour. A few minutes of tweaking at night produced a much improved view and the expected donut pattern on an out-of-focus star.

Perseid Meteor Shower Peak – 2016

This year’s Perseid meteor shower is expected to peak late on Thursday Aug 11 or in the early morning on Friday Aug 12.  Under good dark-sky conditions, you can expect to see 40 to 80 meteors per hours.  Be patient, the Perseids do not create a blizzard of streaksthrough the sky:  60 meteors an hour means an average of just one per minute, and that includes many faint ones.   From locations in the Lower Mainland with moderate light pollution, you are more likely to see one meteor every two or three minutes.

There is often a good show of meteors several days after the peak so the Perseid Meteor Shower Watch event on Saturday at Aldergrove Region Park is great chance to the shower.

PersiedsShower_Chart

Ten Perseid Meteor Facts:

  1. The Perseid Meteor shower has been observed for over 1000 years.  In 33 AD,  a Chinese skywatcher reported that “more than 100 meteors flew thither in the morning” but when the shower first occurred is unknown.
  2. The Perseid meteors are caused by the Earth passing through the debris trail left by Comet Swift-Tuttle which orbits the sun once every 133 years.
  3. The meteors are the pieces of debris,  usually no bigger than a grain of sand, that enter the Earth’s atmosphere.
  4. More meteors are expected this year because the Earth will be moving through a thicker clump of debris from Swift-Tuttle, created partly from the influence of Jupiter’s gravity.
  5. The Perseid meteors strike the atmosphere at a high velocity, about 60 kilometers per second, which tends to produce bright meteors and an unusual number of super-bright meteors, called fireballs.
  6. The Perseid meteors appear to come from the same place: the constellation Perseus, also called the “radiant.” Perseus is found in the northeastern part of the sky.
  7. Light from the moon will interfere somewhat this year but the moon sets at 12:53 AM on August 12.
  8. Observers have photographed Perseids striking the moon.
  9. People have claimed to hear sounds associated with meteor: hissing, sizzling, or pops.  Scientists have recently proposed that that very frequency radio waves created by meteors could vibrate metal objects on the ground.
  10. An astronaut on the International Space Station, Ron Garan, watched the Perseid meteors from space by looking down at the Earth.

Perseid meteor viewed from the ISS