RASC Calgary Centre - Current Astronomical Highlights by Don Hladiuk

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ASTRONOMICAL HIGHLIGHTS provides information about space science events for the upcoming month. The information here is a rough transcript of information covered on the popular CBC Radio One Calgary Eyeopener segment on 1010 AM and 99.1 FM usually on the first or second Monday of each month at 7:37 AM. Don is a life member of the Royal Astronomical Society of Canada and was twice President of the Calgary Centre. Since June 1984, Don has had a regular radio column on the Eyeopener describing monthly Astronomical Highlights to southern Albertans.

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ASTRONOMICAL HIGHLIGHTS September 2020

Broadcast Date September 7, 2020

Prime Time Planets

If you go out for an evening walk after sunset, you will notice two bright star-like objects in the southern sky. These two objects are the two largest planets in our solar system. Jupiter and Saturn.

Jupiter is the brighter of the two planets located in the constellation Sagittarius. Sagittarius sort of looks like a ‘Teapot’ and is situated just to the left of a dim path of light that arcs across the sky, our Milky Way galaxy. Jupiter is a gas giant and could hold over 1300 Earths and it takes 12 years to complete one orbit around the sun. Jupiter is over 670 million km away and the sunlight we see reflected from its cloud tops take over 37 minutes to reach us. Jupiter has around 79 moons but 4 can easily be seen from Earth with a small telescope. In fact, Galileo observed and documented these moons back in the early 1600s and this is why they are known as the Galilean moons. These 4 large moons are named Io, Ganymede, Europa and Callisto. Io has almost nonstop sulphur volcanism and Europa is believed to have an ocean beneath its icy crust that could support simple life. Ganymede is the largest moon and even has its own magnetic field.

Saturn is a little to the left of Jupiter and is noticeably dimmer. Saturn is also a gas giant and is known for its incredible ring system. It is also located in the constellation Sagittarius and takes 29 years to make one orbit around the sun. This beautiful world is over 1.38 billion km away and light takes over 1 hour and 16 minutes to reach us here on Earth. Saturn also has dozens of moons and its largest moon, Titan, even has an atmosphere that is denser than Earth’s. However, because Saturn and Titan are far from the sun, the surface temperatures are so cold (-1730C) that it rains methane and ethane. Titan appears to go through seasons and has lakes of liquid hydrocarbons during its rainy season. If you ever get the opportunity, look at Saturn through a small telescope and I promise you, you will not be disappointed.

Mark this day in your calendar – December 21. If the sky is clear, find a location with a clear southwestern horizon. Just after sunset look for bright Jupiter and only 6 arc minutes away will be Saturn. That is only about 11 Jupiter diameters away. With a high-power eyepiece, you will be able to see both planets in the same field of view with your telescope. According to the RASC, Observer’s Handbook, this close of a conjunction between Jupiter and Saturn has not occurred since 1623 (during the time of Galileo)! Hope for clear skies!

Mars rises about 10pm local time and is in the constellation Pisces. The Earth continues to catch up to the Red Planet as our orbit is on the inside track and we pass Mars every 26 months. As we close the distance between us and Mars, its apparent brightness increases dramatically. But don’t expect Mars to be a big as the Full Moon (internet folklore) as it is still over 70 million km away with a light travel time of about 4 minutes. Even through a large telescope it is not easy to see the polar caps and the characteristic light and dark markings. Mars is small, only about half the size of the Earth and it is still millions of km away. Earlier this summer three separate missions were launched to Mars. In February 2021 the three spacecraft will arrive culminating with the landing of the NASA Mars 2020 (Perseverance) rover with a small helicopter (Ingenuity) on February 18. One of the main goals of this robotic explorer is to answer one of the big questions, “Did life ever start on other planets?”.

If you get up early before sunrise and look to the eastern sky, you will see brilliant Venus. Venus rises around 3am local time and it is located in the constellation Gemini. This earth sized planet shines so bright because of its highly reflective cloudy atmosphere. Venus is only about 130 million km away with a light travel time of 7 minutes.

Largest Solid Rocket Motor in the World

Engineers have completed the first Flight Support Booster (FSB-1) test at Northrop Grumman’s facility in Promontory, Utah. The solid rocket booster is for NASA’s Space Launch System (SLS) rocket. The full-scale test with the booster lasted a little more than 2 minutes, the same amount of time the boosters fire to help send SLS to orbit. The 47 metre long motor burns 6 tons of solid propellent per second and the two boosters together will provide 75% of the thrust needed to lift the massive SLS rocket off the launch pad. Engineers will use data from the test to evaluate new materials and developments for SLS rockets that will power NASA’s Artemis lunar missions beyond Artemis III. Northrop Grumman, the lead SLS contractor for the boosters, have delivered an earlier version of the booster segments for Artemis I to NASA’s Kennedy Space Center in Florida, where they are being prepared for launch.

FSB-1 firing at the Promontory, Utah, facility’s Test Area. Photo Credit: Northrop Grumman

Mystery Solved: Bright Areas on Ceres Come from Salty Water Below (NASA News Release)

Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter and the only dwarf planet located in the inner solar system. It was the first member of the asteroid belt to be discovered when Giuseppe Piazzi spotted it in 1801. And when the NASA spacecraft called Dawn arrived in 2015, Ceres became the first dwarf planet to receive a visit from a spacecraft.

Ceres makes up almost a third of the asteroid belt's total mass, but it is still far smaller than Earth's Moon. Ceres is heavily cratered with large amounts of ice underground.

Called an asteroid for many years, Ceres is so much bigger and so different from its rocky neighbors that scientists classified it as a dwarf planet in 2006. Even though Ceres comprises 25 percent of the asteroid belt's total mass, tiny Pluto is still 14 times more massive.

Ceres is named for the Roman goddess of corn and harvests. The word cereal comes from the same name.

NASA's Dawn spacecraft gave scientists extraordinary close-up views of the dwarf planet Ceres, which lies in the main asteroid belt between Mars and Jupiter. By the time the mission ended in October 2018, the orbiter had dipped to less than 22 miles (35 kilometers) above the surface, revealing crisp details of the mysterious bright regions Ceres had become known for.

Scientists had figured out that the bright areas were deposits made mostly of sodium carbonate – a compound of sodium, carbon, and oxygen. They likely came from liquid that percolated up to the surface and evaporated, leaving behind a highly reflective salt crust. But what they hadn't yet determined was where that liquid came from.

This simulated perspective view from NASA's Dawn mission shows the bright areas of Occator Crater, which contains the brightest area on Ceres, Cerealia Facula in the center and Vinalia Faculae to the side. This simulated perspective view shows Occator Crater, measuring 57 miles (92 kilometers) across and 2.5 miles (4 kilometers) deep, which contains the brightest area on Ceres. This region has been the subject of intense interest since Dawn's approach to the dwarf planet in early 2015. This view, which faces north, was made using images from Dawn's low-altitude mapping orbit, 240 miles (385 kilometers) above Ceres. Dawn's close-up view reveals a dome in a smooth-walled pit in the bright center of the crater. Numerous linear features and fractures crisscross the top and flanks of this dome. Prominent fractures also surround the dome and run through smaller, bright regions found within the crater. The central dome area is called Cerealia Facula and the dimmer bright areas are called Vinalia Faculae. A second simulated perspective view, facing south, is also available (Figure 1). Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of Dawn mission participants, visit http://dawn.jpl.nasa.gov/mission. For more information about the Dawn mission, visit http://dawn.jpl.nasa.gov. Photo Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

By analyzing data collected near the end of the mission, Dawn scientists have concluded that the liquid came from a deep reservoir of brine, or salt-enriched water. By studying Ceres' gravity, scientists learned more about the dwarf planet's internal structure and were able to determine that the brine reservoir is about 25 miles (40 kilometers) deep and hundreds of miles wide.

Ceres doesn't benefit from internal heating generated by gravitational interactions with a large planet, as is the case for some of the icy moons of the outer solar system. But the new research, which focuses on Ceres' 57-mile-wide (92- kilometer-wide) Occator Crater – home to the most extensive bright areas – confirms that Ceres is a water-rich world like these other icy bodies.

The findings, which also reveal the extent of geologic activity in Occator Crater, appear in a special collection of papers published by Nature Astronomy, Nature Geoscience, and Nature Communications on Aug. 10, 2020.

"Dawn accomplished far more than we hoped when it embarked on its extraordinary extraterrestrial expedition," said Mission Director Marc Rayman of NASA's Jet Propulsion Laboratory in Southern California. "These exciting new discoveries from the end of its long and productive mission are a wonderful tribute to this remarkable interplanetary explorer."

Solving the Bright Mystery

Long before Dawn arrived at Ceres in 2015, scientists had noticed diffuse bright regions with telescopes, but their nature was unknown. From its close orbit, Dawn captured images of two distinct, highly reflective areas within Occator Crater, which were subsequently named Cerealia Facula and Vinalia Faculae. ("Faculae" means bright areas.)

Scientists knew that micrometeorites frequently pelt the surface of Ceres, roughing it up and leaving debris. Over time, that sort of action should darken these bright areas. So their brightness indicates that they likely are young. Trying to understand the source of the areas, and how the material could be so new, was a main focus of Dawn's final extended mission, from 2017 to 2018.

The research not only confirmed that the bright regions are young – some less than 2 million years old; it also found that the geologic activity driving these deposits could be ongoing. This conclusion depended on scientists making a key discovery: salt compounds (sodium chloride chemically bound with water and ammonium chloride) concentrated in Cerealia Facula.

On Ceres' surface, salts bearing water quickly dehydrate, within hundreds of years. But Dawn's measurements show they still have water, so the fluids must have reached the surface very recently. This is evidence both for the presence of liquid below the region of Occator Crater and ongoing transfer of material from the deep interior to the surface.

The scientists found two main pathways that allow liquids to reach the surface. "For the large deposit at Cerealia Facula, the bulk of the salts were supplied from a slushy area just beneath the surface that was melted by the heat of the impact that formed the crater about 20 million years ago," said Dawn Principal Investigator Carol Raymond. "The impact heat subsided after a few million years; however, the impact also created large fractures that could reach the deep, long-lived reservoir, allowing brine to continue percolating to the surface."

Active Geology: Recent and Unusual

In our solar system, icy geologic activity happens mainly on icy moons, where it is driven by their gravitational interactions with their planets. But that's not the case with the movement of brines to the surface of Ceres, suggesting that other large ice-rich bodies that are not moons could also be active.

Some evidence of recent liquids in Occator Crater comes from the bright deposits, but other clues come from an assortment of interesting conical hills reminiscent of Earth's pingos – small ice mountains in polar regions formed by frozen pressurized groundwater. Such features have been spotted on Mars, but the discovery of them on Ceres marks the first time they've been observed on a dwarf planet.

On a larger scale, scientists were able to map the density of Ceres' crust structure as a function of depth – a first for an ice- rich planetary body. Using gravity measurements, they found Ceres' crustal density increases significantly with depth, way beyond the simple effect of pressure. Researchers inferred that at the same time Ceres' reservoir is freezing, salt and mud are incorporating into the lower part of the crust.

Dawn is the only spacecraft ever to orbit two extraterrestrial destinations – Ceres and the giant asteroid Vesta – thanks to its efficient ion propulsion system. When Dawn used the last of a key fuel, hydrazine, for a system that controls its orientation, it was neither able to point to Earth for communications nor to point its solar arrays at the Sun to produce electrical power. Because Ceres was found to have organic materials on its surface and liquid below the surface, planetary protection rules required Dawn to be placed in a long-duration orbit that will prevent it from impacting the dwarf planet.

What’s Up in the September Sky

Planets

Jupiter now rises well before sunset and is in the constellation Sagittarius Saturn also rises well before sunset and is also in the constellation Sagittarius Mars is becoming more prominent in the late evening sky in the constellation Pisces Venus is the brilliant star-like object located low in the east before sunrise and is situated in Gemini

Artificial Satellites

The International Space Station (ISS) will be visible over Alberta skies in the early morning sky for the first half of September before it transitions to evening passes later this month. Look for a bright, slow moving star-like object generally moving in a west to east direction. For future dates and times for ISS passes and SpaceX Starlink clusters/trains over Alberta, go to this website and enter your location (important to change your location to the closest city near your location): https://heavens-above.com/

Northern Lights

September is a good month to observe the Northern Lights. The nights are becoming longer and our star is slowly becoming more active as it enters solar cycle #25 (the 25th cycle since detailed sunspot records started being archived in 1755). Smart phone Apps like Aurora Pro will provide a forecast if conditions are favourable for aurora to be visible from your location.

Dates to Remember

September 1: A small 30 metre asteroid passed only 115,200 km away from the earth (between earth and moon) September 2: Northrup Grumman tested a 5 segment solid rocket motor at Promontory, Utah September 3: SpaceX launched another batch of Starlink satellites from Cape Canaveral, Florida September 5: After sunset look for the waning gibbous moon near Mars September 11: Neptune at opposition (closest to the Earth in 2020) September 14: Waning crescent moon near Venus in the eastern morning sky September 17: Free Public Library Web event:

A 2 hour internet on-line "Zoom" webinar via the Calgary Public Library https://calgarylibrary.ca/events-and-programs/programs/an-evening-with-david-levy/

Speaker: David Levy - famous, award winning Canadian astronomer, co-discoverer of Comet Shoemaker-Levy 9 in 1993 which notoriously crashed into Jupiter the next year.

Topic: "A Nightwatchman's Journey: The Road Not Taken. A look back at the life of David Levy, how he developed an interest in astronomy and the night sky, and where it has led him over the decades. "

September 22: Autumnal Equinox occurs 7:31am MDT September 24: Moon is near Jupiter September 25: Moon is near Saturn September 25: Equal day and night for 510 Latitude (Calgary)

Follow Don on Twitter at: https://twitter.com/astrogeo

For more astronomy info go to: The Calgary RASC website

September 2020 Sky Chart Set for September 15 – 22:00 MDT

Sky Chart courtesy of Heavens-Above.com

Don will be back in October

Previous Astronomical Highlights:

• August 2020 • July_2020 • June_2020 • May 2020 • April 2020 • March 2020 • February 2020 • January 2020 • December 2019 • November 2019 • October 2019 • September 2019

Other Sources of Current Sky Information:

• Monthly Star Charts for the Calgary Area • Calgary RASC Monthly Events Calendar • Calgary Weather - from Environment Canada • Heavens-Above Main Page (for Calgary) - ISS passes, Iridium Flares and Satellites visible from Calgary • Dark Sky - generate a monthly calendar of Moon phases, Sunset/Sunrise, Moonset/Moonrise, hours of darkness etc. • Sky News - the Canadian astronomy magazine. • Astronomy Magazine • Sky and Telescope Magazine • Skymaps.com - download and print a monthly Evening Sky Map and Calendar • Astronomy Picture of the Day • Comets currently visible • SkyHound - Current Observing Information • NASA JPL Space Calendar