Sunday, April 30, 2006
For the most recent ephemeris, go to the Minor Planet Ephemeris Service and type
one designation per line, into the the input box. You can get the data formatted for your favorite planetarium software.
(and a Hat tip to Phil the Bad Astronomer for mentioning my humble blog)
No, fragments of 73P will NOT hit the earth.
In the wake of the mssive disintergration of some of 73P's fragments, a few people have been asking if some of the smaller chunks may hit Earth.
The answer is a resounding no!. The reason can be seen in the Hubble image in this post and the spectacular video page, where you can seen an animation of 73P-B breaking up over 3 days. Go now, my favorite is the medium quality MPEG). As you can see, while 73P-B produces a spectacular number of small fragments, mots of them remain cloase to the parent body. Several of them seem to evaporate completely over this 3 day time fame (eg the fragment bottom right).
The fragments that do survive are gravitationally bound, they will follow 73P's orbit around the Sun and won't hit us. Have a look at the Celestia image below to see the relative postions of the comet and Earth.
As you can see in the Celestia image (using the latest ephemeris), even at closest approach the fragments are quite some distance from Earth. At closest approach for spectacularly fragmenting 73P-B, the comet is 0.067 AU, about 26 times the distance from the Earth to the Moon. Now some of those fragments are travelling sideways, but to have any chance of hitting earth, they have to be traveling at around 8 kilometers per second in our direction, and you can see from the images they are drifing much more lazily than that.
Celestia simulation of 73P at time of fragment C's closest approach to Earth (click to enlarge).
Will we get a meteor shower from 73P? Over on the comets list Carl Hergenrother points out that 73P is the parent body of the Tau Herculid meteor shower, which only occasionally produces meteors. Recent studies suggests that there will be no enhancement of the Tau Herculids this year (if they can be seen at all).
There will be significant Tau Herculid activity in 2022, but this will be due to particles released in 1892. We will probably not enocounter the debris fro either the 1995 or 2006 breakups for quite a long time.
Saturday, April 29, 2006
Comet 73P in Celestia!
Friday, April 28, 2006
Dramatic images of 73P-G breakup!
73P-G has broken up dramatically, go to Carl Hergenrother's site and scroll to the bottom for amazing images. Hubble also has some great images, and details here. Fragment B is rapdily evolving and has had a large outburst (see this nice image) and here is a good animation of 73P-B. Fragment R is in outburst. Fragment C is still magnitude 7.9 and is doing fine.
This image shows the location of fragments B, C and G in Corona borealis (click to enlarge)
More Solar flares!
Sunspot group 875 has fired off a strong, M7.5 solar flare. Unfortunately the SOHO Lasco C2 and C3 cameras have no images from this time, so I have no idea if a CME was fired off or not. We'll have to wait a day or so to see if this flare is likely to produce aurora. Also drop into Sungazer for a video of yesterdays flare.
While you are at it, remember that there are currently no plans to replace the ACE spacecraft? Why not write in to ask for a new solar wind monitor.
Galapagos tortoise webcam!
But what about the ORFans
Thursday, April 27, 2006
Two new sun spot groups (875, 876) have rotated onto the face of the Sun. Early this morning there was a C class and M class solar flare from these spots. The flares did not appear to produce Earth-directed Coronal Mass Ejections, so they are unlikley to generate aurora, but these spots should be watched as futher flares may be very likely to produce aurora. Stuart has also noticed this, and reports on the astounding proposal to stop funding aurora alert service. At Spaceweather, they report that there is no plans to replace the ACE space craft, our early warning space weather satellite. Given that NASA is about to increase manned missions, the lack of an early warning craft is foolish in the extreme.
Wednesday, April 26, 2006
Comet 73P-B in outburst!
Comet 73P is still providing surprises. Yesterday Fragment 73P-B was reported to be in outburst again, with the Sun-forward sub-fragment being substantially brighter. The ESA's Very Large Telescope has also taken detailed images of 73P-B, showing more details of the fragments of the fragment (remember that Fragment B recently broke up). Recent amateur images of 73-P are here and here.
Sunday, April 23, 2006
The ISS, Venus, Mercury and the Moon (25th-27th April)
The next few days will be busy ones. On the morning of the 25th (Tuesday, ANZAC day) Venus and the Moon will be close together. For Adeladieans, on this morning the ISS will pass close to Mercury at 6:13 am ACST, at magnitude 2.3 the ISS will be hard to spot, but interesting none the less. Later that night, Callisto will be at maximum distance from Jupiter, and theoretically visible to the unaided eye (see here for spotting details). On the morning of the 26th (Wedensday) the Moon will be close to Mercury. On the morning of the 27th (Thursday) The ISS will pass between Venus and Mercury in most states. Adelaide 5:23 am, Brisbane 4:20 am, Melbourne 5:52, Sydney 5:52, and Hobart 5:56 am. More up to date predictions (the path of the ISS can change substantially over time), and specific predictions for your location can be found in my flares section on Southern Skywatch.
Comet 73P-B breaks up!
Fragment 73P-B has split into two fragments, as seen in these lovely images here, here and here. This image give probaly the first good view of the split nuclei, with intensity traces. Recent reports also suggest that fragment G may have split in two as well.
Both fragments C and B are easily viewable in binoculars (if the clouds ever clear) and small telescopes. Fragment C (the lower one in the image above) is now magnitude 7.9 (ignore the magnitudes in the image, the comets have been evolving to rapidly for the MPC data) Fragment B is something like 8.5-8.9. G is around magnitude 15. Fragments B and C, being close to the stars of Corona borealis, are very easy to find at the moment (providing you aren't clouded out). Looking north-east, locate bright orange Arcturus (the organge star in the image above) then look down and to the right to a curved spray of stars, Corona borelais, the comets will be embeded in this diadem.
A fantastic montage of this area showing fragments B, C and G is located here (small version, very hard to see G in this one) and here (large version). For the most recent ephemeris, go to the Minor Planet Ephemeris Service and type
one designation per line, into the the input box.
No Lyrids for Me
Hughie has been playing with me. We will have beautiful clear afternoons with the sky the purest blue, then shortly after sunset, the clouds will come over and persist unil mid morning. Lulled by this seemingly immutable pattern, I didn't get up early this morning to see if I could pick up any Lyrid lunar impacts. So when I did wander out in the early morn, the sky was celar and sparkly.
I had to rush out and set my telescope up in a hurry, but I was able to get some nice pictures of the Moon and Venus in very stable air, unlike the last two times when the images jumped all over the place (and its been about a wekk since I was bale to do any imaging at all). Unfortunately, this was well into twilight and not too far from dawn, so no Lyrid impacts were going to be seen, and good contrast Lunar images hard to obtain. But you can still see the lava rilles quite clearly despite this.
Friday, April 21, 2006
This year you have a cahnce to see Lunar meteor impacts yourself. On the morning of April 22 the Lyrid meteor shower crossed the Moon. While the lyrid shower is pretty dismal from the Southern Hemisphere, the Moon will be in an excellent position for us to see meteor impacts. See this Space Weather article giving full details of the event. Also see this NASA article as well.
Thursday, April 20, 2006
More on comet 73B
Wednesday, April 19, 2006
Where is 73P now?
Tuesday, April 18, 2006
Venus and Mercury
Sunday, April 16, 2006
Venus and Uranus close together (17-20 April)
Although Uranus is bright enough to be (just) visible to the naked eye, Finding it can be quite difficult. Over the next few days we have a very bright signpost, Venus. Between Monday 17 April to Thursday 20 April Venus will be within binocular distance of Uranus. The Spotter map above (click it to get a full scale view) shows that most nights Venus is just above Uranus (the circle is the field of view of 10x50 binoculars). Uranus is the second brigthest object close to Venus (all except Lambda Aquarii and a star near the bottom are less than magnitude 6, while Uranus is magnitude 5.9). On the 17th Venus is also just 9' from Lambda Aquarii (the red star in the field just below Venus in the image above). See if you can see them separate with the unaided eye. On the 18th and the 19th Venus and Uranus will be within wide field telescopic eyepices. Venus will look like a half Moon, and Uranus should be (just) a visible disk.
Saturday, April 15, 2006
Morning Venus and Mecury
Venus (bright dot near centre top) and Mercury (dimmer dot just above roof line), glow in the predawn eastern sky.
A Movable Feast
Once, on a radio interview, I was asked how to calculate the date of Easter. Embarrassingly, I had no idea at the time (other than it was the first Sunday after a particular full Moon). If you want to calculate the date of Easter yourself, here is a good page from the Astronomical Society of South Australia on calculating Easter (you can do it with a pocket calculator). This BBC site gives you computer code to do it, and finally this site calculates it for you (and all the sites give fascinating historical details of calculating Easter).
Thursday, April 13, 2006
Dan Brown isn't in danger yet
And do drop by The Pandas Thumb for my latest essay.
Is 73P-B disintergrating?
It's going to be one of those days.
Wednesday, April 12, 2006
Occultation of Spica (early morning April 14)
The Moon will occult the bright star Spica (alpha Virginis, magnitude 1) on the early morning of April 14 (April 13 in India). This will be visible from Northern Australia (NT, Northern WA and North QLD), Papua New Guinea, Indonesia, South East Asia and India. Representative local times are given in the at the Southern Skywatch Occultation section (sorry, tables don't seem to work properly in Blogger). The IOTA Spica Occultation page gives a lot more cites, but in Universal time, so you have to do the conversions yourself.
The full moon will make viewing the dissapearance and reapearance of Spica hard to see with the unaided eye. This occultation is best viewed with binoculars or a small telescope. In locations outside the occulation track, Spica and the Moon will appear evry close togeher, and will be interesting to look at.
Tuesday, April 11, 2006
anniversary of the beginning of manned space flight. On April 12 1961, 45 years ago, Yuri Gagarin was launched into space, the first human to travel beyond our fragile world. This is also the 25th anniversary of STS-1, the first Space Shuttle flight, with John Young and Robert Crippen.
What will you do for Yuri's Nlight? I'm going to have a loook for the ISS, and tell my kids about Yuri Gagarin and his flight. If you are more adventurous, you can go to a Yuri's Night Party. There is one in Adelaide (see the party link for contact details), and one in Sydney at the PowerHouse Museum (see party link for contact details, not on the PowerHouse site). If you can't go, why not have a mini-party at your place?
Venus Express has made it!
Monday, April 10, 2006
Venus Express arrives on Tuedsday
Latest on Comet 73P Schwassmann-Wachmann
Fragment B continues in outburst, and despite some fears that it might disintergrate completely, it appears to be hanging on in there. Fragement B is still brighter than C (just) and at magnitudes 9.0 and 9.1 repectively, they are brighter than ephemeris predictions. Currently overwhelmed by the Moons light, by the time the Moon wanes they should be easily visible in 10x50 binoculars. More fragments keep being found, as well, this is one exciting comet!
A nice shot showing C, B and G fragments all together is here.
Some nice individual shots of fragments B, C, G and R is here. As well, here is an image of fragment M.
Sunday, April 09, 2006
Aurora Happening NOW!!! (10:30 pm AEST)
We are having another (mostly unexpected) aurora. aurora have been reported in Tasmania a few moments ago, and the solar wind magnetic field went southwards sharply just now. If you are in New Zealand, Tasmania or Southern Victoria, go outside and look southwards NOW (allow some moments for your eyes to adjust to the dark). Pale green glows, with some sheets and rays should be seen in Tasmania.
Speaking of the Moon
A Moon Mosaic
Finally the clouds parted and I was able to get some shots. ALthough not for long. I manged to get this sequence and make a partial mosaic in the Gimp (the Guide to Gimp for Astrophotography is still coming) before the clouds rolled in as I was imaging. The quality isn't good because of this (messing up the exposures as well). My Venus phase campaign has suffered a bit of a set back, no images for 14 days due to cloud and rain, but I got one this morning. Tonight was clear, cold and cloud free, and I was hoping to make a full mosaic, but even after equilibrating my telescope for over an hour, the seeing was terrible. Oh well, better luck next lunation.
Saturday, April 08, 2006
Blue Ringed Planet.
Blue rings are generally associated with poisonous octopi, but Uranus's faint outer ring, discovered last year, turns out to be blue. Saturn also has a blue ring (the only other planet with a blue ring), associated with the small moon Enceladus, while Uranus's blue moon is associate with the orbit of the small moon Mab. The blue colour is probably due to the small size of the particles scattering light. The blue ring around Saturn is probably due to Enceladus's water gysers. How Mab genereates its ring is unknown at present.
The One That Got Away
Also, I had forgotten about the Moon with Callisto. The Moons light made it difficult to see Callisto in binoculars, let alone with the unaided eye (sigh). On the 17th the nearly Full Moon will be not far from Jupiter, but there is a short time window at 8:00 pm where Callisto may be visible. The 25th looks like our best bet this month.
That takes me back. When I was young, Woomera was one of the few rocket launch sites in the world. For a brief while, Australia was a space-race nation, launching the Black Arrow, Skylark and the Blue Streak missiles (oddly, the Woomera Pad site doesn't list the Bue Streak, even though they were launched there). I had dreams of working in space, and in a (now embarrassing) rush of youthful enthusiasm, a mate and I wrote to Woomera asking for funds to develop Cavorite for spacetravel (well, what did we know, HG Wells sounded authoritative). They never replied, but my dream of space flight persisted.
Time passed, Britain and Australia lost interest in rockets, and the Woomera facility was largely moth balled. We did have a very successful sub-orbital upper atmosphere rocketry program and and X-ray astronomy program, but that finally finished, and now the Woomera launch site is mostly silent (except for the occasional ScramJet flight).
When Stuart came over, I dragged him off the to aviation museum down the road, which had a display of rockets and paraphernalia from Woomera. It was a mild day (for Adelaide, which means our eyes weren't actually boiling in our sockets) and we managed to walk for the Train Museum Carpark (which I had mistakenly parked in under the impression it was right next to the aviation museum) to the aviation museum without getting heatstroke. I rushed in to show Stuart the display…
And it wasn't there. The Museum had moved last year, and they hadn't unpacked most of the Woomera stuff yet. There were a couple of unlabeled launching bodies, and what appeared to be a satellite motor, but that was it. The staff were helpful as they could be, but weren't space enthusiasts, they had no idea when the display would be restored, or what the launching bodies were, or where the thruster came from.
Don't get me wrong, the aviation museum is fascinating, but I had specifically taken Stuart out in heatstroke conditions to see the rockets that his dish at Jodrell used to monitor, so not having them there was disappointing. Later we peered through the chain-link fence at the back of the museum at a Blue Streak hulk, partly buried under bits of a flying doctors plane. It was a bit sad.
Now Andy Thomas wants the Government to spend $150 million to set up a commercial launch and space tourism center. Shooting the wealthy into the edge of space in a glorified glider wasn't what I imagined when I wrote to Woomera all those years ago, I had in mind a more gleaming Gernsbackian spaceprot where I would fly to Mars to study lichens, or explore the steaming Jungles of Venus, but it would be great to see it used again, and Australia join the space capable nations.
Friday, April 07, 2006
Iridium Flares, Saturday 8 April
While waiting to see Callisto, people in Adelaide, Hobart, Melbourne, Brisbane and Perth (Sydney misses out for some reason) will see a nice bright Iridium Flare (magnitudes -7, -6, -2, 0 and -8 respectively, for comparison, Venus is magnitude -4.6 at the moment and Jupiter -2.4). The satellite track is shown in the picture. The Flare maximum brightness is at 19:34 in Adelaide, 19:25 in Hobart, 19:36 in Melbourne and Perth and 19:12 in Brisbane. In all cases the flare should appear in roughly the middle of Sextans, just above Leo. If you want to check your own location, see my flare section at Southern Skywatch.
Thursday, April 06, 2006
Unaided eye Callisto Saturday April 8
It was a discussion with a Velikovsky supporter that alerted me to the fact that the Jovian Moons are potentially visible to the naked eye. As you may know, Velikosky claimed that Venus was originally a "comet" ejected from Jupiter. He also claimed that the myth of Minerva springing from Jupiter/Zeus's forehead was based on visual observation of Venus "erupting" from Jupiter, accompanied by bright lighting bolts from Venus to Jupiter.
Unfortunately, they would have never seen it. All of Jupiter's Moons are bright enough to see with the unaided eye (Ganymeade, the brightest is mag 4.6). Although Callisto at Magnitude 5.7 is just above the limit, and you would need dark skies to see it. Yet you can see none of them (unless you follow the instructions below). Part of this is distance, and the other part is brightness.
The human eye can generally distinguish objects 4' (arc seconds) apart (people with excellent vision can see objects 1-2' apart), although more practically this limit is more like 8-25' depending on age and how good your eyesight is. Io and Europa never get much more than 2' and 3' away from Jupiter respectively, so most people would never be able to see them. Ganymeade and Callisto get to about 5' and 10' respectively at Jupiter's closest approach, and could theoretically be seen, but the brightness of Jupiter overwhelms their light.
Venus would be quite a bit brighter than the Jovian Moons at Jupiter's distance, but still substantially less than Jupiter. A Venus sized object at the distance of Jupiter could possibly be seen at the 8' limit. This would be long after any eruption and "lightning bolts" had happened. So rather than seeing Venus dramatically erupt from Jupiter, exchanging lightning bolts with it, a keen-eyed shepherd might have seen a moderately bright star creep slowly away from Jupiter over several hours/days, provided that Jupiter was at closest approach and Venus was ejected at right-angles to the shepherd's line of sight (otherwise they may not have noticed it for days). Casual observers would never have noticed. Hardly the stuff of legend.
But there is a way to see Callisto without either telescope or binoculars. Like seeing Venus in Daylight, you need to block out the light of Jupiter. This works best when Callisto is at its furthest from Jupiter (and when Jupiter is reasonably close to Earth, so the apparent separation is largest). You will also need dark skies of course, so if you are not in the country, you might like to plan a nighttime trip to the country. The night of April 8 is the first good opportunity we have to see Callisto (there are about 6 others in the next two months, 17 and 25 April and 3 May and 11 May are probably the best).
You will need to be able to see Jupiter (here is the location map for Jupiter), and to have a large object like a wall or roof to block out Jupiter’s light. Because Jupiter is rising straight up, Jupiter's Moons are above it, so you need something that blocks Jupiter from below (like a roof line) rather from the side (until around 1.00 am, when Jupiter levels out). The image above shows how Jupiter will look in binoculars at 10:00 am. With Callisto above and to the left a bit of Jupiter, slowly move so that Jupiter is just covered by the obscuring object, and Callisto should be just visible as a faint star just above the obscuring object. You may need to check the appearance of Jupiter and it's Moons in binoculars, to be sure of what you are seeing.
It will be a challenge, but it should be an interesting challenge.
An unexpected aurora
Wednesday, April 05, 2006
The Angry Astronomer
Comet 73P/Schwassmann-Wachmann hijinks!
Fragment B is still in outburst mode, and is now about as bright as Fragment C (the supposedly brightest fragment). But at magnitude 9.5 this is out of the reach of binocular views yet. A nice fragment B animation is here.
More and more fragments are being described, there are 19 offical fragments, and probably more to come. No more news of the staus of the apparent G split. For amateurs with binoculars or modest instruments, fragments B, C and G are the ones to watch, and we may see some interesting sights in the coming weeks.
Tuesday, April 04, 2006
Comet 73P/Schwassmann-Wachmann's dim future
And not a drop to drink!
Some nice sunspots.
April Southern Skywatch finally up
Monday, April 03, 2006
Comet 73P/Schwassmann-Wachmann is coming!
Sunday, April 02, 2006
Saturday, April 01, 2006
That's not a Moon!
So not much sleep last night, and another Birthday to go to tonight, but I've got some more astro information and stories coming soon.