In this month: March 2022

5th March 1616

On this day in 1616 the Roman Catholic Church adds "" (On the Revolutions of the Heavenly Spheres) by Nicolaus Copernicus to its list of banned books 73 years after it was first published.

Published just before Copernicus’ death in 1543.

The book proposed that the Earth and other planets orbit the Sun. Ironically, Copernicus dedicated the book to the pope, and at the time of its publication there was not much controversy within the Catholic Church. However, by 1616 Galileo was publishing his findings which supported the Copernican theory. Following Galileo's trial by the Roman Inquisition, Copernicus' book was banned and remained on the list of prohibited books for more than 200 years until 1835 when the ban was finally lifted.

21st March 1684

Italian astronomer Giovanni Cassini has a very successful viewing night discovering two moons of Saturn – Tethys and Dione - using a large aerial telescope set up in the grounds of Paris Observatory.

Tethys is Saturn's fifth largest moon and orbits 295,000 kilometres from Saturn. It has two overpowering features, a giant impact crater, Odysseus Crater, 400 kilometres in diameter, nearly two-fifths the size of Tethys itself, and a great valley, Ithaca Chasma, 100 kilometres wide, 3 to 5 kilometres deep, and 2,000 kilometres long, which runs roughly from the north pole to the south pole.

The name comes from the Greek goddess Tethys, the daughter of Uranus and Gaia and wife to Oceanus.

Dione is a small moon orbiting Saturn at a distance of 377,400 kilometres, roughly the same distance that the Moon orbits around the Earth and just like the Moon, Dione is tidally locked with its parent body always keeping one side towards Saturn. Dione has a heavily cratered terrain with craters as large as 100 kilometres across.

The name comes from the Greek goddess Dione.

This discovery made them the last two of four moons discovered by Cassini (the other two were Iapetus and Rhea). He called his moons the Sidera Lodoicea — the Stars of Louis — after King Louis XIV.

Image Left: Saturn and two of its moons, Tethys (above) and Dione, were photographed by Voyager 1 on November 3, 1980, from 13 million kilometers (8 million miles). Courtesy JPL.

13th March 2013

The Atacama Large Millimetre/Sub Millimetre Array or ALMA Telescope in northern Chile officially goes online. The inauguration ceremony was held in Chile’s high desert at an altitude of 5,000 metres. The ALMA Telescope is able to expand its antennas to a maximum distance of 15 kilometres of separation between any two antennas in the array making it the equivalent of a 15 kilometre wide single telescope dish.

At 5,000 kilometres the oxygen is so thin at this height that technicians are not allowed to work on site for more than six hours at a time and must keep oxygen with them at all times. To save themselves from oxygen deprivation during their observing runs astronomers undertake observations at a base site further down the mountain. However, ALMA’s height above sea level, which is above 40% of the Earth’s atmosphere, and the aridity of the surrounding Atacama desert, are what makes it so powerful.

Image: This view shows several of the ALMA antennas and the central regions of the Milky Way above. In this wide field view, the zodiacal light is seen upper right and at lower left Mars is seen. Saturn is a bit higher in the sky towards the centre of the image. The image was taken during the ESO Ultra HD (UHD) Expedition.