Announcements of current events in Astronomy, published by Perth Observatory

Night Sky for June 26, 2009

The waxing moon dominates the evening skies. Early in the moon’s cycle “earthshine” will enhance the view of the crescent moon. When there’s a small sun-earth-moon angle, reflected sunlight coming off the Earth’s reflective oceans and clouds will dimly illuminate the shadowed portion of the Moon’s near side. Near side? Yes – the side facing us. The Moon always turns the same face towards the Earth. It does one spin in the same time that it does one orbit, so the same face is always towards the Earth. That’s synchronous rotation for you. It’s common among most of the larger moons in the solar system.

First quarter, evening half moon phase, will occur on Monday. The next brightest object in the evenings is Jupiter, but you won’t see it until about 9:20pm when it rises just to the south of east. Jupiter’s at its highest elevation, aka culmination or meridian transit, around 3:45am when it’s pretty well overhead. Soon after, the brilliant Venus appears at the eastern horizon. By daybreak, Venus reigns supreme in the NE sky, with the relatively insignificant Mars close by. Jupiter stands out as the brightest object in the western sky at first light.
posted by Greg at 11:14 PM

Night Sky for June 19, 2009.

The big news this week is the winter solstice on Sunday: the shortest days, the longest nights, and the Sun being as far north as it can get. In the old European way of doing things, this solstice would mark the start of winter. For us down under, that is. Northern hemisphere people will be celebrating the summer solstice. Dancing naked at Stonehenge, maybe. At this time the Sun passes directly overhead at local noon for places along the Tropic of Cancer. Down here, it's only about 35 degrees high at local noon at the latitude of Perth, and the day length is about 10 hours.

The Moon's waning, with new moon occurring next Tuesday. Watch for the grouping of Venus, Mars and the waning crescent moon tomorrow (Saturday) morning. On Sunday morning around 6:15am the Moon will be lower, with the Pleiades above it and Mercury and Aldebaran to the right of it. To see that, you'll need a clear view low down in the ENE. At the same time, Jupiter's high up in the WNW.
posted by Greg at 6:32 AM

Night Sky for June 12, 2009.

There will be several good opportunities to see the International Space Station (ISS) in the evenings in the coming week. The following predictions are for the Perth area. You can get your own from www.heavens-above.com . Tonight: low in NNW at 6:39:00, very high in NE at 6:42:00, then disappearing into Earth’s shadow. Tomorrow: low in WNW at 7:04:20, SW at 7:06:35, and then into Earth’s shadow. Sunday, in twilight: low in NW at 5:53:50, almost overhead in NE at 5:56:45, low in SE at 5:59:30. Monday: low in WNW at 6:19:10, SW at 6:21:45, low in SSE at 6:23:50.

For the first time in its 10-year history, the ISS has a full crew of six astronauts: two Russians, one American, one Japanese, one Canadian and one Belgian. They represent the major space station partner countries. After 2010, when the American Space Shuttles are decommissioned, NASA will have to rely on the Russian Space Agency to transport its astronauts to and from the ISS. The estimated fare then will be US$51 million per astronaut. Suddenly a holiday at Rottnest doesn’t seem so expensive!

Saturn’s high in the NNW at nightfall and sets just to the north of west around 11:20pm. Jupiter rises just to the south of east at about 10:15pm, passes high overhead in the north around 4:40am, and is very high in the western sky at dawn. Venus comes up just to the north of east at around 3:45am and dominates the NE sky at daybreak, with Mars nearby. Mercury can be found low in the ENE at daybreak (say 6:15am). The waning moon goes through last quarter phase next Tuesday morning.
posted by Greg at 6:32 AM

Night Sky for June 5, 2009.

Have you got over the shock, or was it the delight, of the end of daylight saving? Many people here must be wishing for a bit more daylight. There’s only a few minutes’ difference between the day length now and the shortest day length on the 21st. The sun’s already as far north as it gets, from our earth-centred point of view. Check the angle of your solar panels. A lot of them are mounted too flat to be much use on a sunny (ish) winter’s day. Watch for the full moon rising on Sunday about half an hour before sunset, and on Monday about 20 minutes after sunset. The full phase actually occurs at 2:12am on Sunday.

If you’re very keen, you can see the International Space Station tomorrow morning: look W at 6:07:15am, NW at 6:08:15, and low in the NNE at 6:10:55. The next good appearance after that will be next Friday evening around 6:39pm in the northern sky. These predictions are for Perth and surrounds. You can get your own from
www.heavens-above.com .

Jupiter’s almost an evening planet now. It rises just to the south of east around 10:45pm and passes high overhead around 5am. At daybreak, say 6am, Jupiter’s overhead in the west and Venus stands out in the north-eastern sky with Mars below it and Mercury well below and to the right, just clear of the horizon.
posted by Greg at 8:08 AM

Night Sky for May 29, 2009.

The waxing moon dominates the evening starscape. First quarter (50%) phase occurs on Sunday night, when Saturn will be located to the north of the moon. People often make the mistake of relating a celestial object’s position to that of the moon, then thinking the object has moved when it’s not so near the moon the next day. The moon’s the moving target! It’s near us, and orbiting around the planet we’re on.

Jupiter’s moving into the evening sky, rising now just to the south of east around 11:15pm. Brilliant Venus rises just to the north of east around 3:40am. At daybreak, around 6am, Venus is like a beacon high in the NE with Mars beneath it, while Jupiter’s directly overhead. Venus and Mars will converge in coming weeks.

If you’re up early, enjoying the views of the bright morning planets, check www.heavens-above.com for predictions of Space Station appearances (don’t omit the hyphen!). See also www.spaceweather.com where it’s reported that the Space Station’s recently enlarged solar panels occasionally produce sudden big “flares” of reflected sunlight, many times brighter than Venus. These are similar to the “Iridium flares” that have been seen for more than 10 years now from the dozens of Iridium communications satellites. The difference is that the Iridium flares are more or less predictable; those from the Space Station aren’t.
posted by Greg at 7:26 AM

Night Sky for May 22, 2009.

With new moon tomorrow, night skies are good and dark – if you’re lucky enough to be away from any source of artificial light. This is the time of year when the Observatory starts its winter programme of gravitational microlensing, seeking for stars with planets. The technique relies upon pairs of stars coming into line, as observed from Earth. When two stars are in exactly the same line of sight, the gravitational field of the nearer one can bend and concentrate the light of the more distant one. The nearer star is acting as a “gravitational lens”.

Obviously it’s best to employ this method in an area where there are lots of stars. Where better than the middle of the Milky Way? Scorpius and Sagittarius span the middle of the Galaxy, and the Scorpion is rising at dusk now, with the Archer following a couple of hours later. They’re up all night. If you’re in a dark enough place to see the Milky Way, that milky glow is actually the combined light of untold millions of stars so far away that you can’t see them as individual points of light. The word galaxy comes from the Greek for milk. Our galaxy contains an estimated two hundred billion stars.

The most inspiring planet views now are for early risers and shift workers. At daybreak, say 5:45 to 6am, Venus stands out like a beacon in the ENE with the rather insignificant Mars beneath it. Seeing Mars like this should dispel any mistaken ideas that people may have about Mars being spectacular this year (it’s never spectacular). Also at daybreak, Jupiter’s high overhead. For evening skywatchers, the waxing crescent moon will be the main attraction from Monday on.
posted by Greg at 7:26 AM

Night Sky for May 8, 2009.

Tomorrow's full moon will be rising in the ESE as the Sun is setting in the WNW – they'll be pretty well diametrically opposite. That's as it should be: as the direction of sunset moves north with the approach of winter, the direction of the full moon's rising goes south. The brightest stars visible at nightfall are Sirius high up in the west, Canopus just as high in the SW, and Alpha Centauri well up in the SE.

Saturn, the only evening planet, is nowhere near as bright – you'll find it high in the NE sky at dusk. Saturn passes due north around 8:10pm and sets in the west at about 1:45am. Bright Jupiter comes up in the ESE at about 12:30am and is very high in the NE sky at daybreak. Brilliant Venus, a treat for early risers, comes up in the east at about 4:10am and stands out in the ENE at daybreak, with the much fainter Mars below and a bit to the right of it.

NASA's hoping to launch Space Shuttle Atlantis on Monday to carry out the last servicing mission to the Hubble Space Telescope. HST has been on its own since the last servicing mission 7 years ago, and it'll be entirely on its own after this last big upgrade. The aging space shuttles will only be scheduled for 8 or 9 more flights after this, all of them to the International Space Station. The shuttles are to be retired next year.
posted by Greg at 12:52 AM

Night Sky for May 1, 2009.


The International Space Station (ISS) is visible in the evenings during the coming week. Oftentimes it's visible in the early mornings, too, but I only describe the evening appearances because that's when the most people are able to watch. My predictions are taken from the website www.heavens-above.com , and the following figures are for the Perth area. If you're more than, say, 100km from the city you ought to get your own predictions. Also, it's best to check “Heavens Above” for an update on the day of observation. The best opportunities should be as follows.

Sunday: low in SSW at 6:29:10pm, well up in SE at 6:31:35, and disappearing into the Earth's shadow in ESE at 6:32:15. Monday (best): low in SW at 6:54:50pm, overhead in NW at 6:57:45, and disappearing high up in NNE at 6:58:20. Wednesday (in twilight): low in SW at 6:11:40pm, very high in NW at 6:14:40, low in NE at 6:17:30.

Meteor buffs will be gazing eastwards in the pre-dawn hours this week, hoping for a show from the Eta Aquarids meteors. These celestial fireworks are debris from Comet Halley – gritty bits of comet stuff that burn up as they come at high speed into the atmosphere. Maximum activity is on the 5th. Also visible before daybreak are the brightest planets: Venus in the ENE and Jupiter away high up in the NE. The waxing Moon will be at first quarter tomorrow, and full moon's on the 9th.
posted by Greg at 5:48 PM

Night Sky for April 24, 2009.

We’re in the middle of International Dark Sky Week, April 20 – 26. It’s an initiative of the International Dark-Sky Association (IDA) which started 21 years ago in Arizona, USA. IDA’s goal is to get people thinking about the impacts on our planet and ourselves of using too much light, hence too much non-renewable fuel, to illuminate our homes, our towns and our workplaces. Why banish the night? It’s well known that being in a never-dark environment is bad for our health and messes up the lives of many other creatures. As well, we’re squandering lots of energy that could be saved and put to better use.

Arizona is not only the home of the IDA, it’s also the home of Lowell Observatory. Lowell is the sister observatory of our own Perth Observatory. In 1970 Lowell sent us the telescope that’s been our main instrument for three decades. Even better: they’ve offered us a bigger one. Stay tuned.

New moon’s tomorrow, Anzac Day. No moon: a time that astronomers love because there’s no moonlight to hinder the viewing of faint objects. If you can’t see the stars very well where you are, have a think about about it. Check out the IDA website www.darksky.org/mc/page.do . A clear view of the night sky is our heritage: we should protect it, for ourselves and for generations to come.

The waxing crescent moon will be visible at nightfall from Monday on. Saturn’s the only evening planet: it’s in the NE sky at dusk, due north around 9pm, and setting in the west about 2:30am. Bright Jupiter comes up in the ESE at about 1:15am and is high in the eastern sky at dawn. Brilliant Venus rises in the east just after 4am. At daybreak it dominates the eastern horizon, with the fainter Mars in close attendance.
posted by Greg at 5:47 PM

G'day! Sorry, I've been remiss in not posting updates here regularly. The Night Sky report from which these entries are drawn has until now been available on the weather page on Mondays in the West Australian newspaper. That's changed: from now on it's going to be in the Today section of Friday's paper, with the Fishing section. Boy, that makes a change!


Night Sky for April 17, 2009.

Evenings are dark now, with the Moon on the wane. A good time for viewing faint objects, like the famous Orion Nebula (M-42): see illustration. Last quarter, the morning half moon phase, occurs tonight: moonrise will be just before midnight. From tomorrow night until next Friday the 24th, the waning crescent moon will be visible in the morning skies. On Sunday night the Moon and Jupiter will rise within about 10 minutes of each other: Jupiter first, then the Moon (note: that's about 1:45am Monday).

Saturn's the only planet visible at dusk, and it will be for a couple of months yet. You'll find it in the NE sky at dusk, due north at about 9:45pm, and setting in the west around 3:15am. There are 3 morning planets: Jupiter, Mars and Venus. Bright Jupiter rises in the ESE at about 1:40am and is well up in the east at daybreak. Mars rises in the east at about 4:20am. Brilliant Venus rises soon after Mars, starting a planetary shuffle that will go on from now until July: a morning spectacle especially for early risers. Mars and Venus will seem to be near each other, conducting a slow pas de deux, for the next couple of months. It's just a line-of-sight effect. Their approximate distances now are: Venus 52 million km, Mars 319 million km. That's reason enough for Mars to look so dim alongside Venus.
posted by Greg at 10:03 PM