Skynotes: February 2024
Upcoming events
Final Mars flight of Ingenuity Helicopter
Ingenuity, that took the first powered flight on another planet on April 19, 2021, and carried out 72 aerial journeys as scout for NASA’s Perseverance Rover, has made its final descent after damage to at least one blade of its high-speed double rotors. Its extended mission far exceeded expectations, with Ingenuity flying much further than planned and totalling over two hours aloft in the thin Martian air.
See
NASA Announcement After Three Years on Mars, NASA’s Ingenuity Helicopter Mission Ends
NASA Video – The Legacy of Ingenuity
Neptune not so blue, and Uranus shows its seasons.
‘Ice giant’ colours updated
The original 1989 Voyager views of Neptune were enhanced for detail to show clouds and other features which gave it a rich blue look – an artificial exaggeration that has persisted. New re-processing of original Voyager data and studies using the Hubble Space Telescope and Very Large Array in Chile, confirms the planet is actually much closer in colour to Uranus. Both are a pale greenish-blue with Neptune only slightly more blue.
The difference between Neptune and Uranus is explained by haze layers and the amount of methane. Neptune’s less hazy atmosphere allows sunlight to penetrate further allowing more red light to be absorbed by methane hence a slightly bluer shade compared to Uranus.
Uranus and its seasonal changes
Credit: Patrick Irwin/University of Oxford.
The above animation sequence of seasons for Uranus is derived from observations made by the Lowell Observatory and covers the period from 1900 - 2068 (two Uranian years). The left hand is a human eye view, while the right has been adjusted to reveal subtle details in the atmosphere. The planet’s tilted rotation axis causes one pole and hemisphere to face the sun for half its orbit. As a result, at these times of solstice Uranus take on a slightly greener tinge (than during equinoxes) as the sunward hemisphere receives more solar radiation. This is believed to explain the planet’s subtly changing colour as the concentration of methane crystals in its atmosphere varies depending on the season.
It is also thought that methane concentration in the polar region is less then equatorial areas with less red absorption and therefore a greener look, with a possible methane ice haze that forms over the sunward pole.
Simulations of Uranus and Neptune
Not only do these giant planets have interesting and dynamic atmospheres, both also have complex rotation axes and magnetic fields, especially Uranus. In these two diagrams, the yellow arrow points to the Sun, the short blue arrow marks the rotation axis, and cyan the magnetic axis. For both planets their rotation and magnetic axes do not align, and their magnetic fields are offset internally. These pictures give only a rough idea but the full animations (see links below) reveal full impression as the planets rotate.
The simulations (from which these stills are taken) are by Tom Bridgman and the NASA Scientific Visualization Studio and can be viewed or downloaded at Uranus and Neptune. You can also explore those for Earth, Jupiter and Saturn for comparison.
See
Oxford University – New images reveal what Neptune and Uranus really look like
Melbourne Sun times
| Date | Rise | Set | Day length | Solar noon* |
|---|---|---|---|---|
| Thursday 1st | 6:32am | 8:33pm | 14:00 hours | 1:33pm |
| Sunday 11th | 6:44am | 8:23pm | 13:39 hours | 1:34pm |
| Wednesday 21st | 6:55am | 8:11pm | 13:16 hours | 1:33pm |
| Thursday 29th | 7:03am | 8:01pm | 12:57 hours | 1:32pm |
*When the sun is at its highest, crossing the meridian or local longitude.
Moon phases
| Phase | Date |
|---|---|
| Third Quarter | Saturday 3rd |
| New Moon | Saturday 10th |
| First Quarter | Saturday 17th |
| Full Moon | Saturday 24th |
Moon distances
Lunar apogee (furthest from Earth) is on Monday 26th at 406,312 km.
Lunar perigee (closest to Earth) is on Sunday 11th at 358,088 km.
Visible Planets
Mercury is soon to disappear behind the Sun and is not visible this month.
Venus remains visible low in the east early in the morning rising around 4.30am before being washed out by dawn light.
Mars will be faint but visible by mid-month in the early morning. It will rise in the east from 4.40am shortly after Venus before it too fades in the morning light.
Jupiter continues to be seen in the north-west from 8.30pm in the evening twilight before setting by 11.30pm.
Saturn, too close to the sun, is no longer visible at night and is soon to move to conjunction behind the Sun.
Meteors
The alpha-centaurids and beta-centaurids are active from 2nd to 25th peaking on the 8th. They are different but it is difficult to distinguish between them. Occurring low in the south near the Two Pointers, they are not strong showers but often have fireballs and persistent trails. 25 per hour can occur but six per hour has been more usual.
See
Stars and constellations
In the east
High in the sky is Sirius, the brightest star at night and the principal star in Canis Major (Greater Dog). This is one of Orion’s two hunting dogs which is why Sirius is also referred to as The Dog Star. Directly below Sirius is the star Procyon which marks the location of Canis Minor, Orion’s smaller dog.
Many cultures have recognised the first evening appearance of Sirius as marking a special time during the year for religious, agricultural or other reasons. It sits 8.6 light years away making it the fifth nearest system to us and its energy output reflects a name appropriately derived from the Greek seirios, meaning glowing or scorching.
Sirius is, however, a binary system. Sirius A is twice the mass of our sun, almost 17 times as large and 25 times as luminous. Small faint Sirius B, however, is a white dwarf about the size and mass as the Earth and is the remnant core of a star that was once similar to our sun. Sirius A and B orbit their mutual centre of mass every 50 years.
In the north-west
Directly north lies Orion, the hunter, seen in the southern hemisphere upside down. The famous three stars of his belt are Mintaka, Alnilam and Alnitak.
From his belt and going upper right is a line of stars which forms his scabbard, in the centre of which is the beautiful Orion Nebula, a vast stellar nursery 1500 light years from us. Upper left in Orion is the blue-white supergiant star Rigel (one of his feet) and lower right is the red supergiant Betelgeuse (one of his shoulders).
Orion’s three belt stars also mark the base of the southern hemisphere’s Saucepan asterism.
To the north-west is the open star cluster the Hyades 153 light years away and forms the inverted V of the head of Taurus, the bull. The red-giant star Aldebaran at its lower right corner is much closer to us at 65 light years.
To the left is the Pleiades, a close cluster of young blue stars 430 light years from us. These stars are formed together and are generally bound together under their mutual gravitational attraction, although over millions of years it is expected the cluster will disperse. Also known as The Seven Sisters and for many cultures across the world they represent a group of women.
In the south-east to south-west
The Southern Cross and the Two Pointers, (Alpha & Beta Centauri) are low in the south-east. In the south-west are the two small nearby galaxies, the Magellanic Clouds, named in honour of 16th century explorer Ferdinand Magellan who embarked on the first circumnavigation of the globe. They look like faint fuzzy patches but are best seen away from city lights. The earliest known physical depictions of them are in petroglyphs in South America.
Arcing across the night sky, and slowly wheeling as the Earth rotates during the night to the east, is the majestic Milky Way - billions of distant stars of our galaxy.
In visible light our view of the galaxy is largely restricted to our local spiral arm which is one of several that sit in the disc of the galaxy. We are looking ‘edge on’ into the flat disc of billions of stars. By contrast, the two darker sides of the night sky a view out of the galactic plane. In those directions we seen far fewer stars for a few thousand light years before intergalactic space begins.
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.
Some bright passes are below for the Melbourne region. On Saturday 12th it will pass overhead in the early morning and again in the evening giving two chances to spot it in one day!
Morning
Thursday 8th 5:30am to 5:37am, South-West to East-North-East
Evening
Sunday 11th 9:20pm to 9:07pm, North-West to South-East
Thursday 29th 9:02pm to 9:07pm, South-West to North-East
Heavens Above gives predictions for visible passes of space stations and major satellites, live sky views and 3D visualisations. Be sure to first enter your location under ‘Configuration’.
On this day
1st 2003, the Space Shuttle Columbia (USA) disintegrated on re-entry killing all seven astronauts and halting the shuttle program for over two years.
1st 1970, US astronomer Vera Rubin finds evidence of ‘dark matter’ by studying motion of stars and galaxy rotation not consistent with Newton’s laws.
3rd 1996, Luna 9 (USSR) made first soft-landing on moon and sent first panoramic images from the Ocean of Storms.
4th 1976, Lunar Orbiter 3 (USA) launches to the moon to select Apollo landing sites.
5th 1963, Dutch astronomer Maarten Schmidt discovers quasars (quasi-stellar radio sources).
7th 1979, Pluto moves inside Neptune’s orbit for the first time since its 1930 discovery.
8th 1969, the Allende meteorite, the largest carbonaceous meteorite found, lands near the village of Allende, Mexico.
9th 1986, first module of Mir space station (USSR) is launched into Earth orbit.
9th 1986, last visit of Comet Halley met by flotilla of probes (notably ESA’s Giotto) with comet’s next return due mid-2061.
9th 1473, birth of Nicholas Copernicus, famous for his sun-centred theory in On the Revolutions of the Celestial Spheres (1543) which triggered the Copernican Revolution.
9th 1975, Soyuz 17 (USSR) returns to earth setting Soviet record of 29 days in space.
11th 2003, first measurements using WMAP (Wilkinson Microwave Anisotropy Probe) data to reveal relic Big Bang temperature as a variation across the universe.
12th 1947, 100 tonne iron meteorite falls in Sikhote Alin, southeast Russia. Largest in recorded history, brighter than the sun, with deafening sound and a smoke trail lasting several hours.
12th 1961, Venera 1 probe (USSR) launched to Venus by Soviet Union.
12th 2001, NEAR Shoemaker (USA) is first probe to land on an asteroid - 433 Eros.
13th 2004, discovery of ‘largest diamond’, white star BPM 37093, is announced.
14th 1990, Voyager 1 (USA) takes famous ‘pale blue dot’ picture of Earth as it looks back while speeding out of solar system.
15th 1564, birth of astronomer, physicist and engineer Galileo Galilei in Pisa, Italy. Supported heliocentric solar system, and studied motion, telescopes, moons of Jupiter, rings of Saturn, phases of Venus, Sun spots, and features of the moon.
15th 2013, 20meter Chelyabinsk meteor explodes 30km over Southern Urals, Russia, travelling at 60,000kph with shock wave damaging buildings and causing many injuries due to flying glass.
16th 1771, Charles Messier’s catalogue of 100 deep space objects.
17th 1965, Ranger 8 (USA) probe launched to image the moon in aid of Apollo landings.
18th 1930, Clyde Tombaugh (USA) discovers Pluto using a blink comparator in a systematic search for the supposed ‘Planet X’ beyond Neptune.
20th 1962, first American astronaut into orbit, John Glenn, in Mercury Friendship 7 in three orbits lasting almost 5 hours.
22nd 1632, Galileo publishes Dialogue Concerning the Two Chief World Systems which compared solar system models and led to conflict with and censure by the Catholic Church.
23rd 1987, SN1987A, closest and brightest supernova since 1054 observed in Large Magellanic Cloud 168,000 light years away. Visible to naked eye for months.
24th 1968, post-graduate student Jocelyn Bell (Northern Ireland) discovers first pulsars.
26th 1966, first Saturn 1B rocket launch, which led to Saturn V Apollo missions.
27th 1942, JS Hey (UK) discovered radio emissions coming from the Sun.
28th 1997, first evidence for gamma ray bursts (GRB) as extra-galactic energy sources.