Bright asteroid flyby

[Whitters]

Early next week, a large asteroid named 2004 BL86 will fly past the Earth-Moon system.  There's no danger of a collision, but NASA radars will be monitoring the mountain-sized space rock as it passes by only 745,000 miles away. Amateur astronomers can watch the flyby, too. Glowing like a 9th magnitude star, 2004 BL86 will be an easy target for backyard telescopes on the night of closest approach, Jan. 26-27.  Check http://spaceweather.com for observing tips and more information.

[Rick]

[BAA-ebulletin 00836] 2004 BL86 - An unusually bright close-approaching asteroid
(c) 2014 British Astronomical Association    http://www.britastro.org/

On the night of January 26/27, asteroid 2004 BL86 will make a close pass of the Earth becoming, for a short time, the brightest natural near-Earth object (NEO) that we know of (other than the Moon) over the next 12 years. The object will be very favourably placed for observation, especially for observers based in the UK and Europe.

BACKGROUND:
This potentially hazardous asteroid (PHA) is quite large, some 0.4-1.0 km across, and so will appear as bright as 9th magnitude when it passes the Earth at the safe distance of 1.2 million kilometres. Although it orbits the Sun every 1.84 years ranging between 0.90 AU and 2.11 AU, the forthcoming event marks its closest geocentric approach for several centuries when it will pass almost 3 lunar-distances away on January 26 at 16:20 UT. This close approach is especially unusual (for a PHA) in that it will continue to brighten by more than a factor of 2 after closest approach whilst it moves towards opposition, reaching the remarkably low phase angle of 1.1 degrees, and attaining a V magnitude of 9.0 on Tuesday, January 27 between 03:40-05:10 UT, during which time interval its apparent speed will have slowed to ~2"/sec.

Please note that its visibility as seen from Europe and North America is very favourable, and so you will not have to wait up until the early hours to spot it since (seen from the UK) the 9th magnitude object will rise and become readily visible soon after 19:00 UT. Its motion should be very obvious as seen through a small telescope (10-cm aperture or larger instrument) when it heads northwards leaving the constellation of Hydra and entering Cancer at around 23:10 UT on the 26th.

CHARTS:
Charts showing the object's track across the sky for the night of January 26/27 (for UK-based observers) have been prepared by Steve Harvey, Director of our Computing Section.
For Jan 26.5-27.0, the chart is at:
http://britastro.org/computing/ch/357439_2004_BL86_2015Jan26Jan26.html
Likewise for Jan 27.0-27.5, Steve's chart is here:
http://britastro.org/computing/ch/357439_2004_BL86_2015Jan27Jan27.html

OBSERVING HINTS:
At its brightest, large binoculars should reveal the interloper as it slowly migrates across the field of view. Between 05:05-05:45 UT on the 27th, the asteroid glides past the western (following) edge of the Beehive star cluster (Messier 44) as seen from southern England. Parallax will significantly affect its apparent position as seen by observers elsewhere. So if you wish to obtain exact celestial coordinates for your location, these can be downloaded from the Minor Planet & Comet Ephemeris Service:
http://www.minorplanetcenter.net/iau/MPEph/MPEph.html
You will need to enter your latitude and longitude (or observatory code - in uppercase - at or near your location) using the online form together with the time (in UT) when you are planning to observe. Using large telescopes with small fields of view, you might consider pointing the scope at a point in the sky where the asteroid is due to pass say 5 or 10 minutes later. You will hen be able to monitor the object coming into view and traversing your field before disappearing at the opposite edge of the frame.

REPORTING:
Updates as to the nature of this object and links to charts, together with observations by members, will be posted on the Asteroids and Remote Planets Section homepage: http://britastro.org/asteroids/
Watch out for brightness fluctuations as it spins on its axis: that's if 2004 BL86 turns out to be rather elongated in shape, or indeed if it happens to be a binary system. It is also worth observing with different filters to see whether its colour changes as it spins, or even spectroscopically to classify its type. Astrometry made from observatories assigned an IAU code should be reported to the Minor Planet Center in the usual way. Images and photometry will be collated by myself as section director - arps [at] britastro.org

Good luck to all weather-wise.

Richard Miles
Director, Asteroids and Remote Planets Section
British Astronomical Association

2015 January 22

[Kenny]

Did anyone catch the asteroid last night?

I set my DSLR for an hour of photos every 5 mins from 12:05am to try and catch movement between shots. It was just too faint. I found mag 8 - 9 stars in shot but nothing over mag 9. Also took my 8" dob out for an hour around 1:45am to try and find it manually. Again, no luck and cloud rolled in just before 3am.

[Miriam]

We found the asteroid (Jeff did actually!). Watched it for 5 minutes up to 11:30 pm as it moved down in the field of view to form a quadrilateral with three faintish stars.   

[Kenny]

Well done. Trust Jeff .

I knew I should have invested the extra time to set up the HEQ5 with my Newt and "goto" the nearest star but it was so much easier/quicker to plonk my Dob on the ground and search manually. My Dob isn't very good at finding objects (I always blame the tools). D'oh!

[Rick]

News reports split out and moved to this thread in "In the Media".

[mickw]

..............and is featured in today's APOD

http://apod.nasa.gov/apod/ap150129.html