January 2025
The Sky Tonight - January 2025
January continues the season of Birak, and the hot weather isn’t going anywhere anytime soon. The night sky presents a parade …
ExploreNew Moon
July 6
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The casual observer
July continues the season of Makuru, keeping the cold weather going. This is the best time of year to simply go outside and look up. During winter, the Milky Way stretches across the sky making for brilliant viewing if you can get to a darker area. The further you can get from light polluted skies, the better.
Image: The Milky Way in full glory overhead during winter.
Credit: Stellarium
The bright central regions of the galaxy are illuminated by tens of billions of stars. So many stars in fact, that our eyes can’t resolve individual points, and instead the whole thing just blurs together, looking like someone has been splashing milk all over the sky.
Earth reaches aphelion on Jul 5, its furthest distance from the Sun. While this occurs in the middle of the southern hemisphere winter, this is not what makes the weather cold. The changing weather of the seasons is all because of the tilt of Earth’s axis. At the moment the southern hemisphere is tilted away from the Sun, making it winter for us. That aphelion occurs at this time is just a coincidence, remember it’s summer up north!
Image: The tilt of Earth creates seasons
Credit: Przemyslaw Idzkiewicz CC BY-SA 4.0
If all goes well, we might see the much-anticipated launch of the Ariane 6 rocket on July 9, hopefully marking a return of the European Space Agency to spaceflight capabilities.
Venus makes a welcome return to the evening sky after having been lost in the glare of the Sun for the past couple of months.
ISS sightings from Perth
The International Space Station passes overhead multiple times a day. Most of these passes are too faint to see but a couple of notable sightings* are:
| Date, time | Appears | Max Height | Disappears | Magnitude | Duration |
| 3 Jul 6:30 PM | 10° above SSW | 34° | 30° above ESE | -3.0 | 4.5 min |
| 5 Jul 6:30 PM | 10° above SW | 65° | 10° above NE | -3.4 | 6.5 min |
Table: Times and dates to spot the ISS from Perth
Source: Heavens above, Spot the Station
*Note: These predictions are only accurate a few days in advance. Check the sources linked for more precise predictions on the day of your observations.
Dates of interest
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Moon, Mars and Jupiter close in the morning sky
July 3
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Earth at Aphelion
July 5
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Possible first launch of the Ariane 6
July 9
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55th anniversary of the first step on the Moon
July 21
Planets to look for
Mercury is hovering above the western horizon for about an hour after sunset all month. If you look at it at the same time every day you should see it moving higher in the sky each day until reaching a maximum height above the horizon in the last week of the month and turning back toward the horizon again as it goes along its rapid orbit of the Sun.
Venus joins the western sky in the latter half of the month, appearing below Mercury and distinctly brighter. This is really just a warmup of days to come, as Venus will dominate the western sky for about the next 8 months, firmly demonstrating its nickname as the ‘evening star’.
Image: Mercury and Venus above the western horizon in the late month.
Credit: Stellarium
The best time to see Jupiter and Mars is about 6am every day of the month, located in the eastern sky before sunrise. Uranus is there as well if you’re keen to get the telescope out. They are joined by the Moon on July 2 and 3. Jupiter’s proximity to Aldebaran in Taurus, as well as the presence of the Pleiades, makes for a nice display.
Image: Mars, Jupiter, Aldebaran, the Moon and Pleiades on July 3.
Credit: Stellarium
Saturn is rising about 10pm this month and is joined by the Waning Gibbous Moon on Jul 24.
Constellation of the month
Corvus the Crow
Corvus is a small constellation in the southern sky about two handspans directly north of the Southern Cross. The constellation stands out amongst an otherwise dim area of the night sky as a distinct quadrilateral of four stars with a couple more bright stars on either side, making the constellation very easy to spot in the southwestern sky during July evenings.
For this reason, it has appeared in various mythologies, with stories interpreting it variously as a chariot, a tortoise, and most commonly a bird, as the prominent asterism resembles a bird with outstretched wings.
One story has the crow being sent by Apollo to fetch a cup of water. The bird got distracted and, realising it would displease Apollo to be so late, snatched up a snake as an excuse for being delayed in bringing water. Apollo percieved the deception and in a fury cast the crow into the sky along with the snake and the cup, which became the constellations of Hydra and Crater.
Astronomers look to Corvus to see the Antenna galaxies. This well-known target for telescopes is a pair of galaxies currently colliding.
Image: Tidal forces in the interacting galaxies draw material out between them, creating the resemblance to an insect antenna.
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgment: B. Whitmore (Space Telescope Science Institute) and James Long (ESA/Hubble)
When galaxies collide, the stars themselves don’t actually strike each other. Rather the galaxies pass through one another and gravity simultaneously tears them apart and brings them together. What does collide are the clouds of gas inside each galaxy, which then collapse and undergo furious star formation in a period called a starburst phase. This is on display in the Antenna galaxies which are alight with the brilliant blues of the star-forming regions and the profound pinks of ionised hydrogen gas. Galaxies in a starburst phase can form new stars at a rate dozens of times higher than regular galaxies.
Astronomers often draw similarities to the Antenna galaxies and the eventual merger of the Milky Way and Andromeda galaxies in several billion years.
Object for the small telescope
The Stargate Asterism
The Stargate is an asterism of six stars in the constellation of Corvus resembling two nested triangles, and so named for its apparent resemblance to a portal device from the namesake television series. While appearing close together, the stars are unrelated to each other, each separated by dozens of light years.
Image: The nested triangles of the Stargate Asterism, centre.
Credit: Mark Johnston, CC BY-SA 4.0
Chang’e 6 and Ariane 6 – Success and anticipation.
China’s Chang’e 6 Moon robot has successfully completed a sample return mission from the far side of the Moon. The mission launched on May 3, entered lunar orbit on May 8 and consisted of an orbiter, a lander and a tiny rover called Jinchan. On June 1 the lander detached from the orbiter and successfully touched down on the surface of the Moon, collected about 2kg of rock and soil samples, and then launched them back off the Moon to rendezvous again with the orbiter. Finally, the orbiter returned the samples to Earth where they re-entered on June 25 and are currently being unpacked and studied before they will eventually be distributed to international partners.
Image: Chang’e 6 on the lunar surface, photographed by the Jinchan rover.
Credit: CNSA
This is the first time rock samples have been collected from the far side of the moon and is interesting because while the near side of the moon shows extensive lava flows, the far side is cratered, relatively uniform and considerably less explored.
The lander touched down near the lunar south pole in Apollo Crater, a 540km wide crater nested inside an even larger, 2500km diameter crater called the South Pole-Aitken Basin. Scientists are hoping the samples collected may reveal clues to how the basin formed and what composition remains in the soil.
Image: The South Pole-Aitken Basin, showing the Apollo Crater and the Chang’e 6 landing site, left, and a zoom of Apollo Crater, right.
Credit: The University of Hong Kong
Meanwhile, if all goes well, the European Space Agency (ESA) will be launching the Ariane 6 rocket on its maiden flight on Jul 9. The Ariane family of rockets has been in flight since 1979 and has evolved through various iterations, and now it’s time for version 6.
Image: Ariane 6 on the pad in Kourou, French Guiana, South America.
Credit: ESA
The rocket is a medium to heavy lift vehicle, capable of launching about 20 tonnes of cargo to low Earth orbit, which makes it comparable to the Falcon 9 or the Vulcan Centaur. This first flight will be carrying 11 small satellites and experiments as a test of the vehicle’s performance.
A lot hinges on the success of this test flight. The ESA has two families of launch vehicles, the Ariane family for medium and heavy lift, and the Vega family for smaller launches. In July 2022 they rolled the newest Vega upgrade called the Vega C. Unfortunately, in December the same year, Vega C failed on its second flight (rocket speak for: it blew up mid-flight after melting its own engine), grounding the rocket family which hasn’t flown since.
Video: Failed flight of Vega C
Credit: Arianespace
Meanwhile the Ariane 5 retired as planned in July 2023. The final nail in the coffin was the breakdown of relations between the ESA and Russia after the latter’s invasion of Ukraine, resulting in the cancelling of launch services between the two parties. Previously, it was not uncommon to launch ESA payloads on Russian rockets.
The result is that the ESA hasn’t had launch capabilities for a year now, during which time it has built up a backlog of more than 20 launches already booked and paid for, many of which are for Amazon’s Kuiper fleet, a competitor to SpaceX’s Starlink. All eyes are on the Ariane 6 when it takes flight on July 9.
