TONIGHT'S SKY                               Southern Hemisphere  

July Highlights 2020

Moon phases

PHASE DATE
First Quarter Sunday 5th
Third Quarter Monday 13th
New Moon Tuesday 21st
First Quarter Monday 27th

This month's Moon apogee (furthest from Earth) is on Monday 13th at 404,199 km and perigee (closest to Earth) is on Saturday 25th at 368,361 km.

Planets

Mercury is not visible this month as it is entirely a daytime object.

Venus rises around 4:30am and fades in eastern daylight by 7am.

Earth, which has an elliptical orbit around the Sun, reaches aphelion (furthest from the Sun) on Saturday 4th at 152.1million km. This is 5 million km more than perihelion (closest to Sun) which was on 3rd January. The Greek prefix 'apo' means far, 'peri' means near or close, and 'helios' refers to the Sun. Our planet's orbit is gravitationally influenced by the Sun and the other planets, but most of all by the nearby moon. It shifts from almost circular to elliptical over 100,000 years and the dates for closest and furthest distance from the Sun vary each year by as much as two days.

Mars rises around midnight and will be lost in the north east by dawn.

Jupiter is easily visible all night across the northern sky. At mid-month it rises at 6pm and sets at 7am.

Saturn follows Jupiter in the north, rising mid-July at 6:30pm and setting in the pre-dawn light.

Meteors

July has no strong showers but in the latter half of July there are some minor showers. Watch around Aquarius and Capricornus and best time is after midnight. July's main meteor shower is Southern Delta Aquarids peaking on the 28th.

Stars and constellations

The Southern Cross (Crux) is high in the south while the bright stars Canopus and Achernar are found low to the southern horizon.

Scorpius is high in the south east with its curving tail just above 'the teapot' or bow and arrow of the centaur archer Sagittarius.

Low in the west is the brightest star visible at night, Sirius, and its associated constellation Canis Major (Greater Dog).

In the north is the inverted question mark of Leo the Lion.

In some Aboriginal traditions the Southern Cross is Bunya the possum sitting high in a tree only coming out at night and always on the lookout for danger, and the brightest star is Warepil or Bunjil the wedge-tailed eagle, chief of the law givers and an important figure right across Victoria.

Explore First Peoples' astronomy, night sky stories, current research, people, and publications on the Australian Indigenous Astronomy website.

International Space Station

ISS orbits every 90 minutes at an average distance of 400 km appearing like a bright star moving slowly across the night sky. For predictions go to the Heavens-Above website.

On this day

1st 1770, closest pass to Earth of any known comet: Comet Lexell at 2.2 million km (roughly 5.5 times the moon's distance).

4th 1054, Chinese and other astronomers witnessed the supernova explosion that produced the Crab Nebula 6500 light years away.

4th 2005, Comet Tempel 1 is crashed landed on by Deep Impact probe (USA) to analyse its composition.

4th 1868, birth of Henrietta Swan Leavitt who established the luminosity-period relationship of Cepheid variable stars allowing Edwin Hubble to show 'nebulae' were other galaxies beyond our own.

5th 1687, Isaac Newton's Mathematical Principles of Natural Philosophy was published laying the groundwork for much of modern science.

7th 1959, Venus' diameter and atmosphere was determined when it occulted the star Regulus in Leo.

8th 2011, the space shuttle Atlantis (USA) was launched on the final mission for the shuttle program.

10th 1962, first communications satellite, Telsar, was launched.

11th 1979, Skylab 1 (USA) was destroyed during re-entry over Western Australia scattering debris over a wide area.

14th 1965, Mariner 4 (USA) made the first controlled flyby of Mars and returned the first close-up images of the planet.

16th 1746, Giuseppe Piazzi, discoverer of dwarf planet Ceres in the asteroid belt, was born.

16th 1969, Apollo 11 (USA) launches to moon for the first lunar landing 5 days later.

16th 1994, Jupiter is stuck by over twenty fragments of Comet Shoemaker-Levy 9.

20th 1969, Apollo 11 (USA) Moon landing when Lunar Excursion Module 'Eagle' touched down in the Sea of Tranquility.

21st 1969, first humans set foot on another world. At 12:39pm AEST Neil Armstrong became the first person to step onto the Moon followed 20 minutes later by Buzz Aldrin, while the third Apollo astronaut, Michael Collins, remained in the Command Service Module 'Columbia' in lunar orbit. Armstrong and Aldrin were on the moon for 21hrs 36min.

22nd 1784, first use of parallax and hence calculation of the distance to a star by Friedrich Bessel.

23rd 1995, Alan Hale and Thomas Bopp discover comet now named after them.

23rd 1928, Vera Rubin born - famous for analysing rotation rates of galaxies.

24th 1969, first lunar landing mission, Apollo 11, ends with Command Module splashdown in the Pacific Ocean.

30th 1971, first Lunar Rover used on the moon in Apollo 15 Mission.

29th 2005, dwarf planets, Eris and Makemake, are announced leading to Pluto becoming a dwarf planets as well.