Announcements of current events in Astronomy, published by Perth Observatory

NIGHT SKY REPORT FOR THE WEEK STARTING MAY 28, 2001.


The moon's waxing - remember, if you can see it at nightfall, it's waxing! Crescent moon tonight and tomorrow; first quarter Wednesday (50% at 6:09am). Then waxing gibbous phases leading to full moon on Wednesday next week. The star above and to the left of the moon tomorrow evening will be Regulus (Alpha Leonis), the brightest star in Leo. The star above the moon on Saturday evening will be Spica (Alpha Virginis), the brightest star in Virgo.

Jupiter's all but gone now, setting in the twilight in the west-northwest at about 6pm. Mercury can still be easily seen low in the west-northwest at dusk, but it's starting to set earlier and earlier now - about 6:30pm tonight, and 6:20pm by the weekend. Mars rises in the east-southeast about 6:25pm and is then the brightest (and the reddest!) starlike object visible until Venus appears in the east at about 3:30am. Venus is now at its earliest rising for the year. At daybreak Venus dominates the north-eastern sky, and Mars is prominent at about the same altitude in the west.

High in the south at nightfall is the small, kite-shaped Southern Cross. Just to the left and down a bit are the two bright Pointers, Alpha and Beta Centauri. The Outer Pointer, Alpha Centauri, is the nearest star we can see at night. It's actually a double star, easily revealed by small telescopes: two suns, orbiting about the mid-point between them. 80 years per orbit. The orbit is not circular, but elliptical, and the distance between the two stars varies from 11 to 35 AU. One AU (astronomical unit) is the average Earth - Sun distance, approx. 150 million km.

Information provided by Perth Observatory, Walnut Road, Bickley. Ph 9293-8255, fax 9293-8109. E-mail perthobs@iinet.net.au. Website www.wa.gov.au/perthobs. Guided tours 2pm Sundays.


posted by Greg at 12:07 AM

ISS - International Space Station

The ISS will be visible over WA from Friday evening

Date Time Direction Altitude Heading
May 25 1807 SSE 11 E
May 26 1845 SSE 35 E
May 27 1747 SE 18 E
May 27 1923 WNW 29 NW
May 28 1825 SE 84 NE
May 29 1903 NW 16 NE
May 30 1804 NW 42 NE

Best passage is May 28 when the ISS will be almost
overhead and VERY bright.

For information on the ISS try spaceflight.nasa.gov
posted by Peter at 4:19 PM

NIGHT SKY REPORT FOR THE WEEK STARTING MAY 21, 2001.


Did you get to see the waning crescent moon low in the eastern sky at daybreak, this morning and yesterday morning? It's fun to observe the turn-around in the phase, backward-C to forward-C, morning to evening, for a couple of days on either side of new moon. New moon (no moon) will be on Wednesday: phase zero at 10:46am. From Thursday on, you can do a nice convenient fortnight of evening "moon obs". The waxing crescent phases will lead on to first quarter, evening half-moon, on Wednesday of next week.

Jupiter can be seen low in the west-northwest at dusk (say 6:10 to 6:15pm) at the start of the week, but by the weekend it's going to be lost in the twilight. Try spotting it just below and to the right of the crescent moon at about 6pm on Thursday. Mercury is now at its furthest distance (22°) east of the sun - you'll find it low down in the north-western sky at dusk. Mars rises in the east-southeast about 7pm, and is the brightest starlike object until Venus shows up in the early morning. Venus rises in the east about 3:40am and stands out as the spectacular "morning star" in the north-eastern sky at dawn. By that time, Mars is across in the west.

Venus has been scanned this year by a pair of huge radio-telescopes acting in unison. The 305m Arecibo dish in Puerto Rico, and the new 100m Green Bank Telescope (GBT) in West Virginia used a radar technique to resolve details as small as 1km across on the surface of Venus. Radar is needed to penetrate the planet's acid cloud and murky carbon dioxide atmosphere.
posted by Peter at 6:11 AM

NIGHT SKY REPORT FOR THE WEEK STARTING MAY 14, 2001.


Moonless evenings now: last quarter moon tomorrow (50% phase at 6:11pm). Last quarter is the half-moon that rises around midnight - the morning half-moon. Thereafter, waning crescent phases lead on to new moon (no moon) on Wednesday next week. Big, bright Jupiter is still visible at nightfall, low down in the west-northwest, but by the end of the week it will be setting in twilight. Mercury is visible also, low down and just to the right of Jupiter at dusk. Early in the week, Jupiter is higher than and sets later than Mercury.
By Friday, the two planets will be setting at the same time. After that, Mercury will be higher than Jupiter and set later.

Mars rises in the east-southeast about 7:30pm, and is then visible for the rest of the night. It passes high overhead at about 2:30am, and is quite high in the western sky at dawn. Brilliant Venus rises in the east about 3:40am, and dominates the north-eastern sky at dawn. Venus and the waning crescent moon will make a fine sight together on Sunday morning.

Three separate astronomical experiments based in Antarctica - the ground-based Degree Angular Scale Interferometer (DASI) and the balloon-borne BOOMERANG and MAXIMA - are measuring the low-level cosmic background radiation that remains throughout the Universe as a result of the Big Bang. Their data jointly support the propositions that the Universe will continue to expand indefinitely, and that the amount of "normal" matter, consisting of protons and neutrons, makes up only about 5% of the total mass-energy balance. Seems like the cosmos is very different from what most of us might have imagined.


posted by Peter at 10:36 PM

NIGHT SKY REPORT FOR THE WEEK STARTING MAY 7, 2001.


It's full moon tonight (100% at 9:52pm), and, if the weather gods are agreeable, it should be a beauty. The moon will rise just a few minutes after sunset, coming up in the evening twilight - a fine view in binoculars and spotting scopes. Jupiter's still the brightest starlike object at nightfall: it's low in the west-northwest at dusk, and sets about 7pm. Mars rises in the east-southeast about 8pm, commanding attention by virtue of its brightness and its reddish colour. It culminates high overhead about 3am, and is high in the west by daybreak. Venus appears in the east about 3:45am, startlingly bright, and dominates the north-eastern sky at dawn. It's the last "star" to fade as daylight comes.

From time to time, we at the Observatory are asked "Where's Pioneer 10 (or 11)?", or "Where's Voyager 1 (or 2)?", or "Which spacecraft is furthest from the sun?". There are four spacecraft on escape trajectories, leaving the solar neighbourhood for ever: Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2. Pioneer 10 was the furthest until February 1998 when Voyager 1, which is faster, attained a greater distance. Each of the probes visited Jupiter, and P11, V1 and V2 also visited Saturn, before sailing on out into the void.

The present distances of the four craft are V1: 81.0 AU, P10: 77.7 AU, V2: 63.9 AU, P11: 59.2 AU. (One AU, or astronomical unit, is the distance from Earth to Sun: approximately 150 million km.) This means V1 and P10 are both about twice as far out from the Sun as the distance of Pluto's orbit - but they're heading in opposite directions.


posted by Peter at 6:37 PM

ANOTHER COMET BREAKUP !!
The following is from an IAU Circular of May 1

COMET C/2001 A2 (LINEAR)
C. W. Hergenrother, M. Chamberlain, and Y. Chamberlain, Lunar
and Planetary Laboratory, University of Arizona, report that 60-s
R-band images of C/2001 A2 taken on Apr. 30.12 UT with the Catalina
1.54-m reflector show a double nucleus. The two components are
nearly equal in brightness and 3".5 apart and aligned precisely on
an east-west line. Both components are highly condensed.
Observations (with the same telescope) on Apr. 24.14 show only a
single nucleus.
Visual m_1 estimates: Apr. 20.93 UT, 7.2 (J. G. de S. Aguiar,
Campinas, Brazil, 11x80 binoculars); 21.46, 7.4 (M. Mattiazzo,
Wallaroo, S. Australia, 7x50 binoculars); 23.16, 6.7 (C. S. Morris,
Fillmore, CA, 20x80 binoculars); 25.35, 6.4 (S. T. Rae, Whakatane,
New Zealand, 8x21 binoculars); 27.48, 6.4 (A. Pearce, Nedlands, W.
Australia, 8x40 binoculars); 29.95, 6.3 (W. Souza, Sao Paulo,
Brazil, 11x80 binoculars); 30.49, 6.3 (Pearce).

This comet is in Orion, so is setting early in the evening. For further information, see

http://www.space.com/scienceastronomy/solarsystem/comet_breakup_010503.html


posted by Peter at 6:07 PM