By Dr. S.A. Mohan Krishna, Amateur Astronomer
Mars, the most celebrated and debated planet, is impeccably detectable with the unaided eye. The features of Mars are encomiastic and have been explored in great detail by the Viking Space Mission.
Mars reaches “opposition” on Oct. 13 and so it has its best conspicuousness for a few months. The specialty of this astronomical happening is that, Mars, the red planet, becomes more striking. On that day, the planet will be closer to earth. Throughout the night, Mars is discernible and more resplendent. Presently, Mars is noticeable in the south-eastern direction at 8 pm.
‘Opposition’ is the astronomical occurrence when a planet farther from the Sun than Earth appears opposite the Sun. This implies, Sun-Earth-planet is in a straight line. This is when the planet is about as close as it can get to Earth, so it is biggest and brightest. Rightfully, this is the best time to observe a planet.
Conveniently, the planet rises when Sun sets and is up all night, setting when Sun rises. An object is at Opposition when the Sun is on one side of the Earth and the object is directly on the opposite side. The result is that the object is fully illuminated by the Sun and appears disk-like. Whenever there is a Full Moon, the Moon is on one side of the Earth and the Sun is on the opposite side.
Autumn 2020 will see the best Opposition of Mars for many years to come. Mars Oppositions occur every 2 years and 2 months (or to be precise, every 779.94 days) and in 2020, Mars Opposition falls on Oct. 13.
From general perspective on our spinning world, Mars rises in the east just as Sun sets in the west. Then, after staying up in the sky the entire night, Mars sets in the west just as the Sun rises in the east. Every 15 or 17 years, Opposition occurs within a few weeks of Mars’ perihelion (the point in its orbit when it is closest to the Sun).
This year, the planet will be much brighter and bigger compared to the previous Opposition with magnitude -2.3. The distance between the planets Earth and Mars at Opposition varies from 56 million kilometres at perihelion (closest point to the Sun) to 101 million kilometres at aphelion (farthest point from the Sun). Also, the apparent magnitude at Opposition varies from -2.9 to -1.4.
The 2003 Opposition was the closest approach in almost 60,000 years! Mars’ orbit is more elliptical than Earth’s, so the difference between perihelion and aphelion is greater. Over the past centuries, Mars’ orbit has been getting more and more elongated, carrying the planet even nearer to the Sun at perihelion and even farther away at aphelion. The red planet came within 34.6 million miles (55.7 million km) of Earth, closer than at any time in over nearly 60,000 years! So future perihelic Oppositions will bring Earth and Mars even closer. 2003 record will stand until August 28, 2287!
At this October’s Opposition, Mars’ southern hemisphere will be tilted towards Earth. When it comes to observing around Opposition, telescopes will show us obscure and light regions on Mars’ disc. These ‘albedo’ features are distinguishable because of variations in reflectivity. The lighter regions normally represent desert areas, while the darker regions are exposed rock. In addition, the planet’s polar caps shine bright. The South Polar Cap (SPC) should govern our view, but as it’s well into the southern summer, this will have shrunk to a fraction of its full size, the residual ice cap faintly offset from the planet’s axis of rotation.
Binoculars will not reveal much more Martian feature than we notice, the planet appearing as a small, bright, salmon pink disc against a background star field. With a telescope, the changes to Mars’ appearance in the run up to Opposition become very palpable. The planet’s largest apparent size occurs when it is closest to Earth and this typically occurs a few days adrift of the Opposition date. It’s not exceptional to see a pink fuzzy splotch at first, but give yourself time to settle into the view and you’ll gradually see more.
From Mysuru, this planet can be noticed from 7 pm to 5.30 am and can be seen in the south-eastern direction.