StarWatch: Moravian University Astronomy

StarWatch for the greater Lehigh Valley

MAY 2026

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1550 MAY 3, 2026: Olber's Paradox: The eighth of sixteen children, Heinrich Olbers (1758-1840) was a physician by training (1780), but a skywatcher by heart. After 1820 he retired from medicine and devoted himself strictly to astronomical pursuits. He was the discoverer of five comets; the most famous was 13P/Olbers discovered in 1815, last returning to the sun in 2024, passing Earth as a 7.4 magnitude object. Olbers also recovered in 1802, Ceres, the first asteroid discovered by Giuseppe Piazzi in 1801. Then Olbers went on to find both the second minor planet, Pallas, in 1802, and the fourth asteroid, Vesta, in 1804. However, Olbers is most famous for the contradiction he postulated in 1826, known as Olbers' Paradox, which asked why the nighttime sky was not ablaze with light. * He surmised that in a static universe containing an infinite number of stars spread homogeneously across the heavens, every position in the sky should be occupied by a star. According to this model, the nighttime sky should be incandescent, not dark as we view it. A similar analogy might be the scene created in a dense forest where every line of sight parallel to the ground eventually converges on the trunk of a tree. * Our universe is not static or infinite, nor homogeneous in stellar distribution, but should the heavens not have some of the characteristics about which Olbers predicted, and be much brighter than it is actually observed? The answer is still no! * A minor contributor to a darker universe is starlight that is obscured by dust. Also in a huge accelerating system like ours, approximately 54 billion light years across, the energy from younger stars may simply not have reached us yet. The speed of light (186,282 miles per second) is fast by our standards of motion and a constant in space, but the time required for light traveling across the universe makes that speed seem more like the movements of a snail. * So what causes our universe to appear dark? It is the expanding-accelerating universe. This same expansion causes the electromagnetic waves emitted by stars to stretch or redden as they move away from us. The amount of redshift in a galaxy has been used for nearly a century to determine the size of our universe. Visible light is shifted into invisible infrared light, but then higher energy, invisible ultraviolet energy, is shifted into the visible. However, there is no gain here. * It is estimated that coolest luminaries, K and M-type hydrogen burning stars, make up about 90 percent of the luminaries in the sky. Their predominant energy production is in the invisible infrared (heat) portion of the electromagnetic spectrum and very little in the ultraviolet, about 0.00014 percent of the sun's UV production which is also very low compared to Sol's visible signature. M-type stars do flare in the ultraviolet, but in total, the redshift actually makes these very common, cooler stars appear dimmer in the light human eyes receive. Another way to look at this concept is to understand the relationship between wavelength and energy, as described by the German physicist, Max Planck. The longer the distance between wave crests, the redder the light becomes, and the less energy that specific wavelengths possess. So the redshift drains the entire amount of energy coming to us, causing the star or galaxy to become less luminous than it would be if we lived in a static universe. This is the predominant reason why the sky is dark. * By tapping here, you'll see a recent image from Australia that I took looking near the heart of our Milky Way Galaxy. It highlights Ptolemy's Cluster (M7) near the center, almost completely obscured by the background haze of millions of stars. The reddening effect of dust is also present on the left side of the image. At the far left, dust created by countless supernova events over the history of the Milky Way virtually prevents any light from escaping. Ad Astra!

MAY 10, 2026: The Automated Telescope Revolution

1552 MAY 17, 2026:

1553 MAY 24, 2026:

[May Star Map]

[May Moon Phase Calendar]