Introduction and Monthly Reminders
The first few days of October started off rainy and cold over northern Utah. As we eased into the first week, the rain subsided, and the temperatures gradually warmed, leading to a clear and warm weekend for stargazers. The second week was expected to be the same, with the rain and clouds coming in at the end of the seven-day period. Unfortunately, for those in northern Utah, this was the case. Fortunately for those in parts of central and southern Utah, the clouds stayed away or were at least scattered enough for eclipse watchers to enjoy the eclipse. The group I was with was part of the fortunate observers, and we could view the entire eclipse. I was able to take some images with my phone through my binoculars, which will be shared at a later date.
Observers will still have the chance to enjoy the Orionid Meteor Shower that peaks on the 21st. There will also be many conjunctions between the Moon and planets in our solar system, including Saturn on the 24th, Neptune on the 25th, and Jupiter and Uranus on the 29th. Venus will reach its greatest western elongation on the 23rd. Interested observers should enjoy the night sky and use their astronomy gear at least one last time this month before the cold and snow settle in.
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| Mercury |
The solar system tour will continue with Mercury, the smallest and closest planet to the Sun. In fact, Ganymede, the largest moon of Jupiter, and Titan, the largest moon orbiting Saturn, are larger than Mercury. The Earth's own moon is only slightly smaller than this tiny planet.
Mercury formed about 4.6 billion years ago with the Sun and other planets in our solar system. Like Venus, Earth, and Mars, Mercury has an inner core, a mantle layer, and an outer crust. The core of Mercury is about 85% the diameter of the entire planet. For comparison, a nickel is about 87% the size of a quarter, so if a nickel is placed on a quarter, that's about the size of the inner core of Mercury. The core of this planet is metallic, believed to be partly molten or liquid. Mercury is the second densest planet in the solar system, the Earth being the most dense.
The surface of Mercury looks similar to that of the Moon, with thousands of impact craters covering its exterior. If a human were standing on the planet's surface, it would appear greyish-brown. Mercury can be found between 29 and 43 million miles from the Sun, depending on where the planet is in orbit. It completes one orbit of the Sun in only 88 Earth days. However, Mercury spins slowly about its axis and completes one revolution in 59 Earth days. The innermost planet was named Mercury after the swift Roman messenger god. Due to the Earth's position in the solar system, only Mercury and Venus can be seen passing in front of the Sun, known as a transit. The next transit of Mercury occurs on 13 November 2032.
Mercury experiences an extreme range of temperatures due to not having an atmosphere to hold onto the heat from the Sun at night. Daytime temperatures can reach approximately 800° F (430° C) and drop to -290° F (180° C) at night. Even with these hot temperatures, Mercury is not the hottest planet in the solar system. That title belongs to Venus. Due to these low temperatures, Mercury may contain water ice in areas that do not receive sunlight, such as deep craters or canyons.
Mercury is one of the most challenging planets to view from Earth because of its proximity to the Sun and its low albedo. The albedo of an object is the ability of it to reflect light. Mercury has an albedo of 0.12, while Venus, the brightest planet in the sky, has an albedo of 0.75. An observer typically has only 30 minutes before it sinks below the western horizon after sunset or about the same amount of time before the Sun's brightness overpowers the glow from this tiny planet.
There have only been three missions to Mercury. The first was Mariner 10, which was launched in 1973 by NASA. This spacecraft imaged nearly 50% of the surface of the planet. The first mission ended in March 1975 when contact with the Mariner 10 spacecraft was lost. The next mission, Messenger, also launched by NASA, came over 30 years later in 2004. Messenger was the first spacecraft to orbit Mercury. Messenger crashed into the surface of Mercury at the end of its mission in 2015. BepiColombo, the third mission to Mercury, launched in October 2018. This is an international mission with two spacecraft provided by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). These two crafts are scheduled to enter the orbit of Mercury in 2025. The ESA's mission is to study the planet's surface and interior, while JAXA's mission is to study the magnetic field. BepiColombo should give us new and exciting images and information about Mercury.
Check back at the beginning of November for my next Monthly Night Sky Report.
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| Now get outside and look up! |
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