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
June 6
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The casual observer
June brings us into winter and the season of Makuru. This typically means it is the time of cooler weather, so we might finally start to see some of that soon.
Scorpius has firmly established itself in the eastern sky during the evenings. You can enjoy an evening stargaze by starting at the Southern Cross, making your way through the confusing mess of Centaurus, over the faint Lupus to arrive at the distinctive curve of Scorpius. Or is it Maui’s fishhook? The great thing about making patterns with the stars is you can make whatever you want. The night sky belongs to everybody, to nobody, and to you.
Image: A nice collection of constellations in the southeast during June. Credit: Stellarium
Image: The scorpion and the fishhook. Same sky, different interpretations. Credit: Stellarium
June 21 brings us to the Solstice. It seems like the good weather only just got here, but this is the shortest day of the year, or more correctly, this day has the least amount of daylight for people living in the southern hemisphere. From here on out there will be more daylight hours per day until the summer solstice in December.
Viewed from space, Earth’s day-night line is at its highest tilt relative to the equator, presenting maximum daylight to the northern hemisphere and minimum to the southern.
Image: Earth viewed from space on the day of the June solstice. Credit: NASA images and animation by Robert Simmon, using data ©2010 EUMETSAT.
If you carefully juggle the numbers and use a generous definition of ‘daylight’, you can actually show that at 9pm in the evening (AWST) for most of June, about 99% of the world’s population experiences daylight. Australia is in the 1% of the population that doesn’t.
June 30 appears in the astronomy calendar as World Asteroid Day, a day dedicated to raising awareness of the risks and opportunities presented by asteroids. Now seems like as good a time as any to read up on the DART mission, even if only for the google doodle. Or if you’re really feeling brave you can check which asteroids currently present the greatest threat to Earth.
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 |
| 5 Jun 6:37 AM | 10° above SW | 60° | 10° above NNE | -3.6 | 6 min |
| 6 Jun 5:50 AM | 33° above SSW | 63° | 10° above NNE | -3.7 | 2.5 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 close to Mars
June 3
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World Oceans Day at Scitech
June 8
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Moon near Antares
June 20
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Winter Solstice
June 21
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World Asteroid Day
June 30
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Saturn, Moon, Mars and Jupiter close together in the morning sky
June 30
Planets to look for
Jupiter makes its reappearance from behind the Sun, visible in the eastern sky in the morning from about 6:30 onwards, rising earlier as the month progresses. Jupiter’s bright magnitude of around -2 will make it easy to tell apart from Mars and Saturn, also visible in the eastern morning sky but considerably dimmer at around magnitude 1. This parade of planets is joined by the Moon in the late month for a nice arrangement.
Image: Saturn, the Moon, Mars and Jupiter on the morning of June 29. Credit: Stellarium
Mercury makes an appearance in the evening sky in the last week of the month after 6pm and stays around this position into July. Venus is not really visible this month as it passes behind the Sun but will return with a vengeance in July.
Constellation of the month
Hydra the Water Snake
Hydra is the largest constellation in the night sky, covering a whopping 3.16% of the sky. It is long and narrow, stretching more than a quarter of the way across the sky (or half of the sky from your viewpoint on the ground), but only a few degrees wide. Despite its size it is quite faint, with the brightest star being the magnitude 2 Alphard, a red giant star located about 180 light years away.
Image: Hydra in the night sky, with the Southern Cross for reference. Credit: Stellarium
Hydra is often recounted in the story of the labours of Hercules. Every time he cut off a head of the beast, two more would grow to take its place. Another story relates to the nearby constellations of Corvus, the crow, and Crater, the cup. The god Apollo instructed the crow to use the cup to fetch him water, but the crow got distracted snacking on fruit. To explain its lateness, the crow snatched a snake from a nearby stream and told Apollo it had been waylaid by fighting the snake. Apollo saw through the deception and cast them into the sky in a rage.
Inside the borders of Hydra lies the interesting object NGC 3314 – two spiral galaxies on a line of sight from us, appearing to be overlapped, but in reality separated by millions of light years.
Image: Two line of sight galaxies make up NGC 3314. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama)
The constellation is also home to the “Ghost of Jupiter Nebula”, a planetary nebula about 5000 lightyears away. Despite their name, planetary nebulae have nothing to do with planets, and are actually the dying remnants of low mass stars. They form when these stars cease fusion in their core and throw off their outer layers, exposing a white dwarf star that ionises the ejected layers, causing them to glow. Their (usually) round shape gives them a vaguely similar appearance through a telescope to planets. This particular one was thought to look so much like a planet it earned the nickname Ghost of Jupiter.
Image: The Ghost of Jupiter Nebula. Credit: NASA, ESA, Bruce Balick and Jason Alexander (University of Washington), Arsen Hajian (U.S. Naval Observatory), Yervant Terzian (Cornell University), Mario Perinotto (University of Florence), Patrizio Patriarchi (Arcetri Observatory), and Reginald Dufour (Rice University); Processing by Gladys Kober (NASA/Catholic University of America)
Object for the small telescope
M83 – The Southern Pinwheel Galaxy
Located about 15 million light years away and shining at about magnitude 7.5, Messier 83 is a spiral galaxy somewhat similar in appearance to what we think the Milky Way looks like. The prominent bar and spiral formation stand out clearly, giving it a stong resemblance to the Pinwheel Galaxy from where it gets its name. Oh it’s is also the namesake for the band too.
Image: The galaxy M83. Credit: ESO
Space Tourism and Surfing Sunlight
On May 19, Blue Origin re-entered (hah!) the spaceflight world with the first crewed launch of their New Shepard rocket since August 2022. The oddly shaped rocket is designed to take up to 6 space tourists on a 10-minute straight-up-and-down-again-flight just over 100km in altitude.
Video: The New Shepard takes flight with 6 tourists onboard. Skip to 1:22:00 for launch. Credit: Blue Origin
Interestingly, one of the passengers onboard was Ed Dwight, a test pilot selected by John F Kennedy to enter the Aerospace Reseach Pilot School but was later not selected for the NASA Astronaut Corps, so this was his chance to finally get to space.
The New Shepard rocket was grounded in September 2022 when an uncrewed flight carrying science experiments exploded shortly after liftoff. Interestingly it was determined that a modification made to one part of the rocket engine to help keep it from overheating had unintentionally caused another part of it to overheat and melt.
Meanwhile, NASA is getting ready to surf sunlight with their Advanced Composite Solar Sail System (ACS3 System). Much the same way a sailboat uses fabric to catch wind and sail across water, this mission is a technology demonstration to use a large sheet of highly reflective material to catch sunlight and use it for propulsion of a spacecraft.
Video: Explanation of the solar sail concept. Credit: NASA Ames Research Center
The concept works because each photon of sunlight has a tiny amount of momentum that is transferred to the spacecraft when it hits the sail. The microwave-sized spacecraft was launched on April 23 and is undergoing commissioning before NASA attempts to unfurl the sail.
This is not the first spacecraft to fly with a solar sail, but the purpose of the mission is to test new deployment methods and composite materials, materials that are flexible enough to fold compactly for launch but can then be unfurled when in space.
Image: The fully deployed sail is about 9m on a side. Humans for scale. Credit: NASA
Solar sails are appealing because of their indefinite lifespan as far as generating thrust is concerned. The miniscule thrust provided by sunlight would not be useful for sudden dramatic manoeuvres but can act over long periods of time to accelerate craft to great speeds. For this reason, they are popular theoretical tools for discussions of interplanetary and even interstellar voyages.
