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I would like to echo Roger’s message by encouraging would-be observers to go to the website and register your observatory as a future participant mentioning in the ‘Comments’ box that you are an amateur astronomer and that you are joining the BAA Exoplanet Division’s initiative to support the ExoClock Project.
We just need some clear skies now – Haven’t seen a properly clear night since last November!
Thanks David for highlight this close approach.
The apparition is on the list of favourable NEO approaches to the Earth in the 2019 BAA Handbook. It is especially easy to observe from the UK as the object is within a few degrees of the opposition point at a Declination of +13 deg when at its brightest (Oct 27). As such it is visible every evening between now and the end of the month, with it as bright as 12th magnitude from Oct 25 – Oct 28, before it finally heads off to southerly declinations and becomes inaccessible from here in the UK.
As many of us cannot attend the actual meeting, it is good to be able to see people’s presentations as a pdf. Mark Bailey’s looks to have been something of a tour de force – an excellent and comprehensive piece of work on his part.
Good point Stuart.
Since Bennu is located between 0.9 AU and 1.4 AU from the Sun, it is in a relatively harsh environment exposed to the solar wind and measuring only about 500m across it has an extremely low gravity. So since it is likely to be billions of years old, there is a lot of time for any dust between the loose assemblage of boulders to be lost. As to the mechanism for this, electrostatic charging is a good one, as you suggest.
One thing to note when looking at the boulders is that they are not like terrestrial rocks since they are very black (4.6% albedo) but more especially the bulk density of Bennu is only 1.26+/-0.07 g/cc. So as there are a lot of voids between the boulders, their density will be roughly 1.8 g/cc on average. This value is similar to the lightest meteorites (certain carbonaceous chondrites have a density of about 2.1 g/cc). My guess is that many of the boulders comprise some sort of porous carbon material mixed with silicaceous grains.
Next year, a sample is scheduled to be taken and the scientists are looking for areas on its exterior where fine-grain material is present and where they can avoid boulders. They have found 4 possibilities:
https://www.space.com/asteroid-bennu-landing-site-options-nasa-osiris-rex.html
Apologies – you are correct – the density of individual pebbles should be about equal to the Bulk Density divided by the Packing Density. So if the Packing density is 0.7 then the actual density of the pebbles would be 1.26/0.7 = 1.80.
Not good to rush from one thing to another on my part. And one should read what one has written before posting! Sorry for that – I will edit the above and put it right.
In fact, my earlier post talked about the angular nature of the pebbles/boulders and the lack of dust particles, and I speculated that one reason is that this could be that the material formed in a relatively high-temperature environment and that it could be rich in carbon including elemental carbon. So having a true density of 1.8 (not 1.0) and being very dark would fit with that scenario.
Mark – I did a search for a suitable asteroid candidate but only came up with 321 Florentina 15th magnitude P=2.87 h Ampl.=0.31-0.52 mag. So there would be a minimum every 1.5 hours or so.
This doesn’t really become accessible until late September / early October. It reaches opposition in December at mag 13.8.
Richard
(3200) Phaeton is one of those asteroid-comet transition objects, so is particularly interesting. I see the article you refer to was the subject of a presentation by Teddy Kareta at the AAS Division of Planetary Sciences meeting last October. I have been corresponding with Teddy on another topic in recent months and am hoping to be a joint author on his latest paper.
Concerning Phaeton, Alex Pratt has recently drawn our attention to a successful occultation campaign to measure its shape. A couple of weeks ago the object underwent a stellar occultation as seen from the USA and we now know that its silhouette measures 5.7 x 4.7 km. See:
http://iota.jhuapl.edu/20190729PhaethonAug09.ppt
It is also on a target list of objects to be visited by the DESTINY+ space probe due to launch in 2022.
The material looks to be very coarse and rather angular in shape.
Not much evidence of fine dust.
My take on this, David, is that the assemblage formed by gravitational attraction from debris whilst at relatively high, refractory temperatures – quite unlike a comet precursor. I wonder how rich it is in carbon and is any of it in nearly pure elemental form?
Yes – I visited here when Joan G. owned the place. It would be a suitable site for sure.
La Palma is relatively easy to get to from the UK and a good holiday destination too.
What a great suggestion, Andrew!
The kit you describe would be very effective operating in remote telescope-mode.
The ODK 16 is a very multipurpose scope and you look to have focussing sorted out: stability of focus is an important factor in remote operation.
Am sure there are several BAA members who would be seriously interested in your proposal – I can’t speak for the Association but would be happy to discuss with you and others offline.
Clear skies,
Richard Miles
The previous evening to the Xanthippe event was nice and clear so I did a practice run doing things like finding the star and taking a picture of the field on the screen using my iPhone so I knew exactly which star was which. I also found out that the OccuRec software for recording the video was playing up and so I sort of found a way around that issue well ahead of time. Am still on a learning curve as to how to set up to avoid disappointment but hopefully we’ll have many more similar opportunities to go after in the future. But a practice run beforehand is a great idea.
(P.S. For the Titan/28 Sgr occultation in 1989, we were able to do a dry-run at the same clock time as the real event the next day – it made all the difference then too!)
Exoplanets are the new Holy Grail for the professional community, so the BAA has now taken the subject on board. In 2017 ARPS had two meetings on Exoplanets in conjunction with the VSS. 2019 should see a lot of new stuff – Expect an ARPS meeting that year. And in 2020, Exoplanets will be the subject of attention at the Saturday afternoon session of the Winchester Weekend meet.
Gary,
Not sure if you are registered with your own members’ webpage. It would be good to have it posted on the Members’ Pages.
Cheers, Richard
Yes, Gary – our witnessing a dwarf nova becoming a classical nova is unprecedented. And I see Robin’s spectrum shown on the ARAS Spectroscopy Forum:
http://www.spectro-aras.com/forum/viewtopic.php?f=5&t=2015
was of particularly high quality (given plenty of photons from a 6th magnitude source) and managed to report ahead of the professionals. Robin’s contribution was duly acknowledged by Wagner et al. in ATEL #11588:
http://www.astronomerstelegram.org/?read=11588
My request is – Can someone put a short news note out on the BAA frontpage so as to alert the membership, etc.?
Richard
Ian – I see the manual states:
Using the included NexRemote software you can control your NexStar telescope with a computer via the RS-232 port located on the computerized hand control and using the RS-232 cable . For information about using NexRemote to control your telescope, refer to the help files located on the disk. In addition to NexRemote, the telescope can be controlled using other popular astronomy software programs.
And Megastar is compatible with the following scopes:
- Meade LX2000, AstroPhysics GTO, Celestron NexStar 5/8/GT/GPS, Sky Commander, NGC-MAX, Sky Wizard, Sky Vector, Advanced AstroMaster, BBox, MicroGuider III, Mel Bartels and RXDesign ServoCAT.
So it should definitely work. Make sure you use the correct driver for the scope and it looks like it all works via ASCOM.
Unfortunately another of his remarks adapted from Wikipedia says:
On appointment as Astronomer Royal, Woolley reiterated his long-held view that “space travel is utter bilge”. Speaking to Time magazine in 1956, Woolley noted:
“It’s utter bilge. I don’t think anybody will ever put up enough money to do such a thing . . . What good would it do us? If we spent the same amount of money on preparing first-class astronomical equipment we would learn much more about the universe . . . It is all rather rot”.
Woolley’s protestations came just one year prior to the launch of Sputnik 1.
So the proverbial pinch of salt needs to be invoked when it comes to taking certain of his comments seriously.
Thanks Denis for keeping us informed on this naming. I had a distant memory that several other names had been considered for Eros (1898 DQ), the first near-Earth asteroid discovered. Eros remained quite a special object up until Pluto was found, in that only three other NEAs were discovered during the intervening 32 years, one of which (719 Albert) was subsequently lost for all of that time.
