Announcements of current events in Astronomy, published by Perth Observatory

"Night Sky" for February 12, 2010.


With no moon in the evenings now (new moon on Valentine’s Day), most interest is likely to centre on Mars and the International Space Station. You can see Mars any evening, looking like a bright reddish star low in the NE sky at nightfall. It culminates well up in the north around 11:15pm and sets in the WNW at about 4am.

The Space Station is more of a challenge: you have to get the time and the direction right. Check www.heavens-above.com for predictions. The best passes will be: Monday, S at 8:28:10pm and SE at 8:29:50; Tuesday, SSW at 8:49:55pm and well up in S at 8:51:40; Thursday 18th, SSW at 8:00:05pm, high up in SE at 8:02:50, E at 8:04:00 (these figures are for the metro area).

Saturn appears at the horizon in the east around 9:15pm. It culminates high up in the north around 3am – that’s the best time for viewing, if you’re very keen. Saturn’s rings are still pretty well side-on: it appears as an orb with a “handle” either side. The waxing crescent moon will be visible at dusk from next Wednesday the 17th: teachers, that’s when you can kickstart another round of moon “obs”.
posted by Greg at 6:33 AM

"Night Sky" for February 5, 2010.


As befits a planet that's just gone through opposition, Mars is up all night and culminates in the north around midnight. It dominates the NE sky at nightfall. About an hour before sunrise, the red planet is setting in the WNW. Although it’s not much of a target to view through a telescope – just a small, round, reddish thing – it’s the only planet that earthlings are likely to visit within the next generation or two. For that reason, lots of space probes have been sent there. In years gone by, most of them failed. Fortunately, the outcomes have been a lot better in recent times. The two NASA rovers, Spirit and Opportunity, are still “alive” after six years on the cold, dry, dusty Martian surface. They were never very sporty. After meandering a total of 7.7 km in the six years, Spirit is hopelessly bogged in soft sand. Half a world away, Opportunity is still mobile; it’s travelled all of 19 km. No chance of it going to the rescue! The waning Moon goes through last quarter (morning half moon) phase tonight.
posted by Greg at 8:21 PM

"Night Sky" for January 28, 2010.


Tomorrow's full moon will just be a normal full moon. Nothing blue about it. The label "blue moon" for the second full moon in a month is just a historical accident. Still, it coincides with perigee, when the Moon's near Earth. So, tomorrow evening, watch for the big Moon rising at about the same time as the Sun sets (7:20pm for Perth). If you like the idea of having two full moons in a month, this is a big year for you: it'll happen again in March.

Also tomorrow, Mars is at opposition and therefore pretty close and up all night. You'll find it low in the ENE at dusk, well up in the north around 12:30am, and going down in the WNW at dawn. With Jupiter now setting only about an hour after sunset, Mars has become the dominant evening planet.

The International Space Station will make a number of evening passes in the coming week. The best will be: tonight, starting low in the NNW at 8:10:35 and climbing to the right to be high in the NE at 8:13:20 before going down into the ESE at 8:16:10; and tomorrow, WNW at 8:34:00, well up in SW at 8:36:40, and SSE at 8:39:15. For more details check the satellite prediction website www.heavens-above.com .
posted by Greg at 8:28 PM

"Night Sky" for January 22, 2010.


The waxing moon dominates the evening viewing. First quarter's tomorrow. That’s the evening half moon. On Australia Day the phase will be about 80% - plenty to illuminate your evening activities, with or without fireworks. Jupiter's going down in the west in the early evening as Mars rises in the ENE. Mars will be at its closest next Wednesday night - where are the dumb emails saying it'll look as big as the full moon? Oh, yeah, they come around August - an idiot echo of the close approach by Mars in August 2003.To show how wide of the mark those stories are, here are the dates of Martian close approaches since August 2003: October 2005, December 2007, January 2010. Intervals of about 2 years 2 months. Mars has an eccentric orbit, and the very closest approaches happen at intervals of 15 to 17 years.
posted by Greg at 12:46 AM

Night Sky for December 25, 2009.

We have an evening half moon for Christmas this year – first quarter’s today. Last Christmas there was no evening moon; it was 2 days before new moon. In 2010 Christmas will be 3 days before last quarter. This shows the difficulty of using a lunar calendar. Christmas is, at its grass roots, the recognition of the northern hemisphere’s winter solstice. It’s an important seasonal milestone. Ordering your life by the lunar cycles, the way that people did in ancient times, makes it hard to keep track of the seasons. The period from new moon to new moon, or from full moon to full moon, is 29.53 days. It doesn’t relate in any straightforward way to the length of the year.

Jupiter’s the dominant planet. It stands out well up in the west at dusk, and goes down just to the south of west at about 10pm. Mars appears on the horizon in the ENE at about 10:30pm and is prominent quite high up in the northern sky at daybreak. Saturn rises in the east just after midnight and is in the NE sky at first light, well to the right of the much brighter Mars. The New Year festivities will be lit by the full moon this year, and with it there’ll be a little, partial lunar eclipse (mid-eclipse 3:20am Jan. 1).
posted by Greg at 6:26 PM

Night Sky for December 18, 2009.

This evening the waxing crescent moon should be easily visible at nightfall, with Mercury just to the left of it at 8:20pm or so. Mercury’s setting at around 8:45pm now, in the WSW. As the week goes on the crescent moon will fatten, reaching first quarter on the 24th-25th: a half moon at Christmas.

Jupiter continues to be the brightest starlike object in the evenings, standing high in the western sky at dusk and setting just to the south of west around 10:30pm. If you remember Venus doing its fine Star of Bethlehem impression last Christmas, you may wonder where it’s gone. Being a planet – planet means wanderer – Venus won’t be found in the same place from one year to the next. The rise/set tables in the new Astronomy Almanac show that it won’t even be easily visible again until mid-April.

Mars rises in the ENE around 11pm and is prominent in the northern sky at daybreak. Saturn appears low in the east at about 1am and is well up in the NE at first light. The summer solstice occurs next Tuesday, the 22nd: longest daytime, and shortest night. Check the predictions on www.heavens-above.com for evening views of the Space Station this week.
posted by Greg at 6:30 AM

G'day. I'm back online. Christmas is fast approaching, and the New Year 2010. Crumbs, how did the blogging slip so badly? We've been pretty flat out in the International Year of Astronomy, and it looks like a busy summer season coming up. If you want to book for a viewing night, check the Activities Calendar and book at least a month ahead. As the following article says, the Astronomy Almanac 2010 is here. Better hurry to get your copy for Christmas. Phone 9293-8255.

Regards, Greg.


Night Sky for December 11, 2009.

For the astro-nut in your family, the good news this week is that the Perth Observatory’s Astronomy Almanac 2010 is on the streets. Solstices, equinoxes, direction of sunrise/sunset, moon phases, rise/set times of sun, moon and planets, it’s all there. Among the listed phenomena are “meteor showers”, a description that can be misleading. Rarely will meteors put on a celestial firework show. This month’s major meteor “shower” is the Geminids, debris from the strange object 3200 Phaeton. Phaeton is believed to be the dead heart of a comet, travelling on a very elliptical orbit that goes out to its aphelion in the asteroid belt and back in to its perihelion well inside of Mercury’s orbit. Gaze towards Gemini which is rising in the NE around 10:30pm, due north around 2am, and NNW at daybreak. Peak activity is expected on Sunday, Monday and Tuesday mornings. Good luck.

The waning crescent moon is the dominant morning object. New moon’s next Wednesday. Jupiter’s the brightest evening object – it’s high in the western sky at dusk, and sets just to the south of west around 11pm. Mercury’s low down in the WSW in evening twilight, setting around 8:30pm. Mars is visible low in the ENE at midnight.

((Night Sky is an article appearing weekly in the West Australian newspaper, in the Today section on Fridays.))
posted by Greg at 5:41 PM

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