And by friends, I’m referring to the Friends of the Lansing Community Library (FotLCL for short), a nonprofit organization that is member supported and advocates, fundraises and provides critical support for my local library, the Lansing Community Library (LCL for short). Their mission, which you can choose to accept as well, is to support LCL in providing free and equal access to information for all citizens through donations of time, talent and resources.
This week I want to discuss “What might cause the closer of two identical stars to appear dimmer than the farther one?”
Apparent Magnitude: A measurement of the brightness of stars without regard to their distance from Earth.
- The scale in use today starts with the star Vega and an apparent magnitude of 0.0
- Objects brighter than Vega are assigned negative numbers. For example. Sirius, the night’s brightest star, has an apparent magnitude of -1.44
- The scale was extended to include the dimmest stars visible through binoculars and telescopes. For example, a pair of binoculars can see stars with an apparent magnitude of +10
Ignoring distance for a moment, all other things being equal, the closer of two identical stars will appear brighter (have a smaller apparent magnitude) to us than the more distant star. When we account for the difference in distance, we use either or two measurements: absolute magnitude and luminosity.
Absolute Magnitude: The brightness a star would have at a distance of ten parsecs (10 pc) or 32.6 ly. Continue reading
Posted in Astronomy, Constellations, Mathematics, Science, Sirius, Stars, STEM, Ursa Major, Vega
Tagged absolute magnitude, apparent magnitude, astronomy, inverse-square law, luminosity, parallax, Stars
A friend and work colleague of mine who also happens to be a photographer started posting snapshots in her Facebook feed last week. The challenge was to take a photo a day from your life with no people featured in them and provide no explanation. Oh, and they must be black and white photos.
This intrigued me as my first camera back in the early or mid 70s had been a small inexpensive fixed lens camera that used small rolls of black and white film. My dad had a dark room at home but I don’t think we ever developed film that I shot in my camera, at least not until I was much older and part of the yearbook staff in high school.
I decided to revisit my youth and took up the challenge. I also happened to be on vacation this week so I had plenty of time to think of what sites in and around my home would lend themselves to good black and white photography.
Here’s the seven I posted daily on my Twitter and Facebook feed:
And here are all the photos I took in the last week that I used as the pool of photos to choose from:
Posted in 2D, Art, Autumn, Digital, Dogs, Family, Photography, Rottweilers, Seasons
Tagged amateur photography, autumn, Rottweilers
I’ve reached the halfway point through my Introduction to Astronomy class. This week marks the eighth week of fifteen, sixteen if you count the first week where we just spent time getting to know each other and exploring the textbook and getting the lab software, Starry Night, installed and licensed. Last week, we reached the outer limits in the Kuiper Belt and Oort Cloud of our solar system where only comets and Voyagers I and II have ventured. Now we’ve snapped back to study our closest star, Sol, or more commonly just the Sun. My topic for discussion responds to the following question:
Why is the solar cycle said to have a period of 22 years, even though the sunspot cycle is only 11 years long?
Some surface features on our active Sun vary periodically in an eleven year cycle. The Sun’s magnetic fields which cause the surface changes vary over a twenty-two year cycle. The relatively cool and slightly darker regions, commonly called sunspots, are produced by local concentrations of the Sun’s magnetic field piercing the photosphere. The latitude and number of sunspots on average vary during the same eleven year cycle. But the hemisphere where the Sun’s north magnetic pole anchors during one eleven year cycle will have south magnetic poles during the next. Because it takes a full twenty-two years for the magnetic poles to return to their original orientation astronomers refer to the entire solar cycle. The magnetic dynamo model posits that many transient features of the solar cycle are caused by the effect of differential rotation and convection on the Sun’s magnetic field. The Sun’s differential rotation (different speeds at different latitudes) causes its magnetic field to become increasingly stretched like a rubber band. The bands can’t break so they periodically untangle themselves with the help of trapped gases which leak out (sunspot) and gradually settle back under the photosphere, when the sunspot disappears. The most recent reversal of the Sun’s magnetic field occurred in 2013. We are currently at the tale end of Solar Cycle 24. (Comins, 2015, p. 272-83)
My topic for discussion this week will attempt to answer the question:
Why do astronomers believe that the debris that creates many isolated meteors comes from asteroids, whereas the debris that creates meteor showers is related to comets?
But first, I want to share two things that serendipitously fell from my Twitter feed (@mossjon) today. Today’s APOD (Astronomy Picture of the Day @apod) featured the unusual mountain on Ceres (Comins, 2015, p. 239).
What created this unusual mountain? Ahuna Mons is the largest mountain on the largest known asteroid in our Solar System, Ceres, which orbits our Sun in the main asteroid belt between Mars and Jupiter. Ahuna Mons, though, is like nothing that humanity has ever seen before. For one thing, its slopes are garnished not with old craters but young vertical streaks. One hypothesis holds that Ahuna Mons is an ice volcano that formed shortly after a large impact on the opposite side of the dwarf planet loosened up the terrain through focused seismic waves. The bright streaks may be high in reflective salt, and therefore similar to other recently surfaced material such as visible in Ceres’ famous bright spots. The featured double-height digital image was constructed from surface maps taken of Ceres last year by the robotic Dawn mission. (“APOD: 2017 October 9 – Unusual Mountain Ahuna Mons on Asteroid Ceres,” 2017)
The second thing that immediately caught my eye today was an episode of Astronomy Magazine‘s “The Real Reality Show” entitled “How an Asteroid Killed Off the Dinosaurs” covered late in Chapter 8 of our textbook (Comins, 2015, p. 263-4) and which also bonked me on the head via my Twitter feed:
(“Real Reality Show: How an Asteroid Killed Off the Dinosaurs | Astronomy.com,” 2015)
But enough from our sponsors. On with the real show and convincing Chicken Little that the sky is indeed not falling.
In this week’s discussion topic, I attempt to answer the question “Why are Uranus and Neptune distinctly bluer than Jupiter and Saturn?”
On Uranus and Neptune, the methane absorbs red, orange and yellow light, reflecting back the blue. In contrast, Jupiter and Saturn have only minor trace amounts of methane and quite a bit more hydrogen and ammonia.
This view of Uranus was recorded by Voyager 2 on Jan 25, 1986, as the spacecraft left the planet behind and set forth on the cruise to Neptune Even at this extreme angle, Uranus retains the pale blue-green color seen by ground-based astronomers and recorded by Voyager during its historic encounter. This color results from the presence of methane in Uranus’ atmosphere; the gas absorbs red wavelengths of light, leaving the predominant hue seen here. Image Credit: NASA/JPL
Posted in Astronomy, Neptune, Science, Solar System, STEM, Uranus
Tagged astronomy, atmosphere, ice giants, methane, Neptune, planets, solar system, Uranus
On the basis of lunar rocks brought back by the astronauts, explain why the maria are dark-colored, but the lunar highlands are light-colored?
Regions of both the near side and far side of the Moon not covered by mare basalt are called highlands. The highlands consist of the ancient lunar surface rock, anorthosite, and materials thrown out during the creation of the impact basins. (“Lunar Rocks | National Air and Space Museum,” n.d.)
The anorthosite rock highlands are brighter than the maria basalts. Pulverized by meteoric action, both the basalts of the maria and the anorthosite of the highlands are covered by a blanket of powdered rock, also known as regolith. Continue reading