May 21, 2023
Saturday, May 21, 2023
Tonight a very thin waxing crescent moon will be just above the western horizon at sunset. The following night, it will be to the lower right of Venus, close enough for both to just barely fit within the field of view of your binoculars. Before the sun sets, you can use the moon to pick out Venus against the blue sky with your binoculars. On May 24, a fatter waxing crescent moon will be to the left of Mars. They’ll be close enough together to fit within the same field of view of your binoculars. The moon will also be at the right edge of the Beehive Cluster in the middle of Cancer, so slew your binoculars a little left to take in that cluster. On May 26, the first quarter moon will be next to the brightest star of Leo, Regulus, at the end of the Sickle part of Leo. At the end of the month, Mars will have moved to the right edge of Virgo.
The Voyager 1 and 2 spacecraft continue to function gathering data in interstellar space (beyond the heliosphere where the sun’s magnetic pressure from the solar wind deflects interstellar cosmic rays). Voyager 1 is now over 160 times farther out than Earth is from the sun (or over 4 times farther out than is Pluto). It takes the radio signals from Voyager 1 slightly over 22 hours to travel between Voyager 1 and Earth. Voyager 2 is over 133 times farther out than Earth is from the sun and the radio signals take 18.5 hours to make the journey from Voyager 2 to Earth.
The Voyager spacecrafts have been traveling 46 years to get out to these distant points. They are the longest-lived NASA mission. The Voyager team figured out a new power management scheme to keep all five of the instruments functioning on Voyager 2 that are used to study interstellar space until 2026. After that, they’ll need to turn off the instruments, one-by-one, over the following several years as it runs out of power. The previous power management scheme would have required the sequential shut off to begin this year.
Both Voyagers are powered by radioisotope thermoelectric generators (RTGs for those who don’t want to say that mouthful) that generate electricity from the heat of the decay of plutonium. Because these spacecraft were designed to operate in deep space, they were not fitted with solar power arrays. Although the sun is still by far the brightest star visible to the Voyagers, the sunlight is much too diluted by the great distance to generate the power needed by the instruments.
Scientists continue to mine the Voyager data from their flybys of the planets long ago. One team re-analyzed the Voyager 2 data from its Uranus flyby in early 1986 (ancient history for most of my students) and determined that four of Uranus’ five large moons could have a liquid water layer below their icy surfaces. The liquid water layers in Ariel, Umbriel, Titania, and Oberon are much thinner, though, than what we’ve found in Europa and Enceladus—just 20 to 30 miles thick. The new models of the moons’ interiors will need to confirmed by the proposed Uranus Orbiter and Probe that will hopefully launch in the 2030s and reach Uranus by the mid-2040s.
A bit closer to home and much younger, the James Webb Space Telescope continues to wow astronomers with its super-sensitive infrared capabilities. One recent observation was of the young (and bright) star, Fomalhaut of the constellation Piscis Austrinus. Fomalhaut is just 25 light years away and it’s young enough to still have a disk of dust and gas surrounding it which should form planets in the future.
Webb’s keen eye was able to detect an inner belt of debris that is like the asteroid belt of our solar system (between Mars and Jupiter). The Hubble Space Telescope and other telescopes have been able to see the outer debris disk that is like Kuiper Belt of our solar system which resides just beyond the orbit of Neptune. Webb was also able to see a dust cloud within the outer debris ring that may be the result of the collision between two large asteroids. The dust cloud has noticeably changed over the years. When it was first detected by the Hubble Space Telescope back in 2004, it was much more compact and bright, so we thought it was an exoplanet. It was heralded as the first visible-light image of an exoplanet. However, it seemed to disappear several years later. If it is indeed a dust cloud from the collision of large asteroids, it would be the first time we’ve actually witnessed such a collision so near the time it happened.
I hope you’ll be able to experience a truly dark sky filled with thousands of stars this summer!
—
Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com
