First Friday Astronomy

This is a reprint of a blog post originally run Jun 2022.
Gravitational lensing of distant galaxies observed by Hubble. From https://www.nasa.gov/content/discoveries-highlights-shining-a-light-on-dark-matter.

Although our current understanding of gravity, the theory of general relativity, arose only one hundred years ago, scientists were speculating about exotic gravitational effects going back to before the word “scientist” even existed. Today, astronomers employ gravity in a variety of ways to study the cosmos, to look for planets outside our solar system and even to weigh some of the largest celestial bodies in existence. These measurements have shed light on some of the darkest of astronomical mysteries.

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From https://webbtelescope.org/resource-gallery/articles. (This is a slightly updated reprint of an article originally run Nov 2021.)

An artist’s concept of the Webb Space Telescope. From https://solarsystem.nasa.gov/missions/james-webb-space-telescope/in-depth/.

NASA’s James Webb Space Telescope (JWST), scheduled to launch on December 18, will primarily use its spectrographs – specialized instruments that capture and spread out light like a rainbow – to study exoplanets. By analyzing this data, known as spectra, researchers will be able to measure exoplanets’ compositions and chemistries. Spectra will help refine what we know about any exoplanet Webb observes, including massive gas giants, mid-sized ice giants, and smaller rocky exoplanets (some of which could be similar to Earth). In a few cases, JWST will deliver images of exoplanets to reveal more about them.

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The roar of the Death Star exploding would have been impossible to hear at a distance since sound can’t travel in space.

Even though sound cannot propagate through the vacuum of space, that doesn’t mean we don’t know what space sounds like. Audio recordings have provided a wealth of information for space scientists almost since the beginning of the space era. Because of their simple and robust operation, microphones have been included on many past and recent space missions, on which they have recorded wind sounds and dust sounds. They will even accompany NASA’s return mission to Saturn’s moon Titan in the 2030s. Audio recordings allow us to reach far across space but also back and forth through time, and probably the last, soulful vestiges of human civilization will persist in the form of audio long after we’re gone.

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HST image of the AGN at the center of Messier 87, spewing a jet of plasma, 5000 light years long. From https://en.wikipedia.org/wiki/Messier_87.

Hidden within the depths of a distant galaxy, a luminous behemoth lurks. As it greedily devours whole star systems, the leviathan unlooses a blistering spurt of flame light years long and crackling so loudly it can be heard across the Universe. Astronomers first discovered these cosmic monsters, called active galactic nuclei or AGN, during World War II. Even though they are some of the brightest objects in the Universe, clouds of dust and gas within their host galaxies obscure their machinations. Understanding the evolution of galaxies and the formation of planetary systems requires unveiling these cosmic monsters, and computer simulations coupled with JWST observations are helping unveil these cosmic monsters.

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The Large Magellanic Cloud, a satellite galaxy of the Milky Way. From Wikipedia.

On a clear night in central Idaho, you can see the sweep of our own Milky Way galaxy split the velvet sky. Although we now know the observable Universe spans 13 billion light years, in the 1920s, astronomers didn’t even know how big the Milky Way was. In fact, many astronomers believed our galaxy comprised the entire universe and that what we now know as different galaxies were just strange nebulae within the Milky Way. The story of how astronomers finally took the true measure of the Universe as a result of the the tireless efforts of a human computer.

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Night sky within the Central Idaho Dark Sky Reserve. Taken from https://www.ioes.ucla.edu/project/tracking-light-pollution-in-the-central-idaho-dark-sky-reserve/.

The dramatic growth of the Treasure Valley impacts more than just commute times. The glare from our shining cities also obscures the night sky. And, like other forms of pollution, light pollution respects no municipal boundaries. Treasure Valley’s bright lights and big cities are starting to affect the night skies in the nearby Central Idaho Dark Reserve (CIDSR). Here are some of the details of our local light pollution and ways we can help mitigate its effects.

Much of the information here comes from this report written by the students from the UCLA Institute of the Environment and Sustainability.

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The Zodiacal light, a feature that requires unusually dark skies.

(This post previously ran in 2021 May but has been updated.)

Summer is the prime stargazing season. Venture out under the crystal Moon to watch Scorpius chase Orion from the sky. But if you stay within Boise’s city limits, you may find it harder to see some of your favorites. As Boise grows, so too does its footprint in the sky. However, there are many places in Idaho largely unmarred by the glare of municipal growth.

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In 1986, superstars Lionel Richie and Michael Jackson won a Grammy for “Best Song of the Year” for “We are the World“, a single recorded to support the African charity USA for Africa (https://usaforafrica.org/) to provide food and relief aid to starving people in Africa, specifically Ethiopia where a famine raged. With sales in excess of 20 million copies, it is the eighth-bestselling physical single of all time, and it immediately generated 60 million dollars.

But 1986 also marked the 300th anniversary of one of the most popular science books of all time, Conversations on the Plurality of Worlds. And a NASA mission just over the horizon may turn the sci-fi conversations about alien life from this classic pop-sci book into science fact.

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