Bakersfield Night Sky - July 1, 2017
Bakersfield Night Sky - July 1, 2017
By Nick Strobel
Tonight is the free public star party hosted by the Kern Astronomical Society at Panorama Park near where Linden Avenue meets Panorama Drive. The telescopes will be pointed at Jupiter, Saturn, moon, globular clusters, open clusters, and bright nebulae. Observations begin shortly after sunset and go until 10 PM.
On Monday afternoon, July 3, 2017, the earth will reach is farthest distance from the sun. We'll be 94,505,901 miles from the sun—3.3% farther than the closest distance in January. However, we're in the middle of summer because the sun can get so high in the sky and it is above the horizon for a long time. For a number of things in astronomy, the angle of something is more important than its distance.
NASA recently released its final catalog of exoplanets from the original mission of the Kepler when it was focused on a single patch of sky in the Cygnus constellation. With this final catalog the tally of exoplanet candidates found by Kepler in its primary mission is 4034 and the number of confirmed exoplanets is 2335. Of this set, 30 near-Earth size exoplanets are in their star's habitable zone and another 20 are still listed as “candidates” that haven't been verified.
In previous catalogs only a small proportion of the near-Earth size habitable zone exoplanets were orbiting stars like the sun. That's because it is easier to spot small worlds around much cooler stars than the sun. In this final catalog, the Kepler team added an additional seven candidate near-Earth size habitable zone exoplanets that orbit stars more like the sun. Eleven other small candidate exoplanets around cooler stars were also added. The chart of near-Earth size habitable zone exoplanets now looks more evenly distributed for all types of stars.
With previous catalogs it was clear that smaller planets are more easily made than big planets like Saturn and Jupiter. It was also clear that our solar system is unusual in that we don't have a planet that is of a size between Earth and Neptune. Exoplanets in this intermediate size range are either “super-Earths” or “mini-Neptunes”. Super-Earths are those that are primarily rock-iron worlds while mini-Neptunes have a much greater proportion of lighter hydrogen compounds—water, ammonia, methane—and hydrogen and helium.
Another research group headed by Benjamin Fulton, a graduate student at the University of Hawaii at Manoa, might have found the dividing line between super-Earths and mini-Neptunes. If the exoplanet is less than about 1.75 times the size of Earth, it is a super-Earth. If it is above two times the size of Earth, the forming exoplanet has enough mass to pull in enough hydrogen and helium from its surrounding environment nebulae to become something like Neptune.
Fulton's group has sharply defined the upper size for a habitable world. Worlds larger than two times the size of Earth will either have no surface or the surface is under an extremely deep atmosphere with such a crushingly high pressure (far more than that found at the deepest point of the Marianas Trench on Earth) that no life we know of could exist.
Kepler continues its search for exoplanets in the second phase called “K2”. In this phase Kepler looks at patches of the sky distributed along the plane of sky aligned with Earth's orbit. It looks at these patches for about 80 days at a time. It has found 148 confirmed exoplanets and another 520 that have yet to be confirmed in the K2 mission.
The numbers I've quoted are those found by Kepler. Although the Kepler space telescope has found the largest number of exoplanets of any search team, there are plenty of others that have been found—3497 confirmed exoplanets as of the time I'm writing this. See the Exoplanet Archive at exoplanetarchive.ipac.caltech.edu for this list. This archive is more restrictive than the Extrasolar Planets Encyclopedia at exoplanet.eu because the Exoplanet Archive lists just the objects less than 30 Jupiter masses with orbital and physical properties in publicly-available peer-reviewed publications. Regardless of whether one is picky or a bit more lenient, there are a lot of worlds to study!
In our solar system we're still trying to find Planet Nine—a proposed super-Earth with ten times Earth's mass orbiting on average 700 times farther from the sun than Earth does. There's some controversy in the research community about whether or not the assumptions used in the statistical analysis of the computer simulations of thousands of orbits done by Konstantin Batygin and Michael Brown are valid. Controversies like this do happen in research and it's actually healthy in science. Our computer simulations are only as good as the assumptions and physics knowledge going into the coding of the computer programs. The statistical case for Planet Nine is still strong enough to warrant spending time on huge telescopes like the 8.2-meter Suburu Telescope on Mauna Kea looking for it.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
—
Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com
