Sunday, January 31, 2016

Comets & Asteroids - Summary for January 2016

This post introduces a new monthly column that will serve as a summary of the most important news about comets & asteroids and an overview of the comets  discovered (and recovered) throughout the month just ended. During the month of January 2016,  8 new comets were discovered, there were 2 recoveries and cometary activity has been reported for 2 previously discovered objects (earlier designated as asteroids). Moreover, observations of a secondary companion for comet P/2015 Y2 = P/2010 V1 (IKEYA-MURAKAMI) and the discovery of the binary nature of asteroid (2242) BALATON have been reported. "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here).

The dates below refer to the date of issuance of CBET (Central Bureau Electronic Telegram)  which reported the official news & designations. 

- Comet Discoveries

Jan 07  Discovery of C/2016 A1 (PANSTARRS)
Jan 07  Discovery of P/2016 A2 (CHRISTENSEN)
Jan 07  Discovery of C/2016 A3 (PANSTARRS)  
Jan 16  Discovery of C/2016 A5 (PANSTARRS)  
Jan 20  Discovery of C/2016 A6 (PANSTARRS)  
Jan 23  Discovery of P/2016 A7 (PANSTARRS)
Jan 23  Discovery of C/2016 B1 (NEOWISE)
Jan 29  Discovery of C/2016 A8 (LINEAR)

Comet C/2016 B1 (NEOWISE) - J. Masiero / Gemini Observatory / AURA

- Comet Recoveries 

Jan 03  Recovery of P/2010 V1 (IKEYA-MURAKAMI) as P/2015 Y2 + secondary component
Jan 11  Recovery of P/2001 F1 (NEAT) as P/2016 A4

- Cometary activity detected

Jan 10  Cometary activity detected in 2007 VA85 = P/2007 VA_85 (LINEAR)
Jan 29  Discovery of 2015 VL62 = 2015 YY6 = C/2015 VL62 (LEMMON-YEUNG-PANSTARRS)

Comet P/2015 Y2 (IKEYA-MURAKAMI) - Credit: LCOGT/Man-To Hui

- Asteroid news

Near-Earth Objects (NEOs) discovered in January 2016:  155

Jan 23  CBET 4243 reports that minor planet (2242) BALATON is a binary system with an orbital period of 12.96 +/- 0.01 hr.  

Dictionary of Minor Planet Names by Lutz D. Schmadel

by Ernesto Guido

Tuesday, December 8, 2015

New Comet: C/2015 X4 (ELENIN)

CBET nr. 4216, issued on 2015, December 08, announces the discovery of a comet (magnitude ~18.2) by L. Elenin on three CCD images obtained with a 0.4-m f/3 reflector at the ISON-NM observatory near Mayhill, NM, USA on Dec. 3.5 UT. The new comet has been designated C/2015 X4 (ELENIN)

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 20 unfiltered exposures, 120 seconds each, obtained remotely on 2015, December 03.9 from I89 (iTelescope network - Nerpio) through a 0.32-m f/8.0 astrograph + CCD, shows that this object is a comet with a compact coma nearly 8 arcsec in diameter elongated toward PA 290.

My confirmation image (click on it for a bigger version)

M.P.E.C. 2015-X105 assigns the following preliminary elliptical orbital elements to comet C/2015 X4: T 2015 Nov. 2.64; e= 0.81; Peri. =  176.15; q = 3.39;  Incl.= 29.49

by Ernesto Guido

Thursday, November 12, 2015

WT1190F to hit Earth's atmosphere on Nov. 13, 2015

An object (probably space junk) discovered on October 3, 2015 by the Catalina Sky Survey and designated WT1190F will enter the Earth's atmosphere on 13 November 2015, making it one of the very few space impacting object observed prior to atmospheric entry (see old posts about asteroids 2008 TC3 & 2014 AA).  

This object will re-enter Earth's atmosphere in a few hours, around 06:20 UT on 13 November 2015 about 100 km off the southern coast of Sri Lanka (at 11:50am local time). It is quite small, probably about one or two meters across and so it is expected that most or all of WT1190F will burn up in the atmosphere before impacting, but will be possibly visible as a bright daytime fireball. 

Click on the images below to see the impact location. The magenta blob off the south coast of Sri Lanka is the nominally predicted impact area. According to Bill Gray: "nominally predicted impact area is the area within which we'd expect it to hit, assuming the object doesn't move in unexpected ways. Small objects such as this are pushed around a bit by sunlight. So I won't be surprised if it lands a couple of kilometers outside the predicted region". 

Credit: Bill Gray

Credit: Bill Gray

After collecting more observations and unearthing 2012 and 2013 obs from telescope archives, it has been possible to conclude that WT1190F is most probably a piece of discarded space junk. In fact WT1190 interacts with solar radiation pressure in a way that suggests it has low density (space junk is a lot lighter than a rock. It's so light that even sunlight can exert a very gentle push on it). Moreover it is in a very unusual and elongated orbit (eccentricity 0.96) taking it to within one Earth radius of the surface of the Earth at perigee but 1.65 Lunar Distances at apogee. It could be a spent rocket stage or panelling shed by a recent Moon mission. It is also possible that the debris dates back decades, perhaps even to the Apollo era.  Below a plot of the last three orbits of WT1190F. The small red circle is the earth. The big green circle is the orbit of the moon, just to give some scale to the chart (click on it for a bigger version).

Credit: Bill Gray

For more detailed info about the nature, size & history of this object please check the webpage maintained by Bill Gray at Project Pluto.

Astrometry obtained just before impact will help to pin down the trajectory and the impact location. So, I performed follow-up measurements of this object, about 22 hours before it entering Earth's atmosphere. Below you can see the image showing WT1190F at magnitude ~18.5, stacking of 30 unfiltered exposures, 30-sec each, obtained remotely on 2015, November 12.4 from H06 (iTelescope network - New Mexico) through a 0.43-m f/6.8 astrograph + CCD + f/4.5 focal reducer. Click on the image below for a bigger version. 

Below a short animation (spanning about 10 minutes) made out of my follow-up images. The first frame was obtained at 08:17UT while the second frame was obtained at 08:27UT of Nov, 12, 2015. (WT1190F is the star-like object at the centre while stars are trailed because the images were stacked on WT1190F motion)

UPDATE - November 13, 2015

First images of WT1190F reentry are available!! Images obtained by a team of researchers under the consortium "Rapid Response to a next TC3 asteroid impact". They were observing the event from an airborne sponsored by United Arab Emirates Space Agency & the International Astronomical Center (IAC) in Abu Dhabi.





See also the video below prepared by the expedition team, with photos of the re-entry and  of the cameras & instruments used on the airborne to follow the event: 

by Ernesto Guido

Thursday, November 5, 2015

New Comet: C/2015 V2 (JOHNSON)

CBET nr. 4161, issued on 2015, November 05, announces the discovery of a comet (magnitude ~17.1) by J. A. Johnson on CCD images obtained with the Catalina Sky Survey's 0.68-m Schmidt telescope on Nov. 3.5 UT. The new comet has been designated C/2015 V2 (JOHNSON).

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 12 unfiltered exposures, 120 seconds each, obtained remotely on 2015, November 04.4 from H06 (iTelescope network - New Mexico) through a 0.43-m f/6.8 astrograph + CCD + f/4.5 focal reducer, shows that this object is a comet: compact coma nearly 10 arcsec in diameter elongated toward PA 230.

My confirmation image (click on it for a bigger version)

M.P.E.C. 2015-V44 assigns the following preliminary parabolic orbital elements to comet C/2015 V2: T 2017 Feb. 14.70; e= 1.0; Peri. =  188.19; q = 0.93;  Incl.= 41.14

Below you can see a graph generated using the software Orbitas and showing the C/2015 V2 predicted magnitude (in red) versus its elongation from the Sun. Click on the image for a bigger version. (A word of caution: as always with comets, the future magnitudes reported here are only indicative and based on a very preliminary orbit).

by Ernesto Guido

Monday, October 26, 2015

Close Approach of Asteroid 2015 TB145

The asteroid 2015 TB145 was discovered  (at ~ magnitude +20) on 2015, October 10 by  Pan-STARRS I survey (MPC code F51) with a 1.8-m Ritchey-Chretien + CCD. 

Asteroid 2015 TB145 has an estimated size of 290 m - 650 m (based on the object's absolute magnitude H=19.8) and it will have a close approach with Earth at about 1.3 LD (Lunar Distances = ~384,000 kilometers) or 0.0033 AU (1 AU = ~150 million kilometers) on 2015, October 31 at 17:01UT. This asteroid will reach the peak magnitude about +10 between on October 31. Radio astronomers will try to  observe it as the radar signal-to-noise ratios will be very strong "so this should be one of the best radar targets of the year.  We hope to obtain images with a range resolution as high as 2 m/pixel using DSS-13 to transmit and Green Bank (and possibly Arecibo) to receive. The flyby presents a truly outstanding scientific opportunity to study the physical properties of this object."

Moreover 2015 TB145 is in an extremely eccentric (~0.86) and high inclination (~40 deg) orbit.  It has a Tisserand parameter of 2.937 hinting that it may be cometary in nature. If so, then this would be the first time that the Goldstone radar has imaged a comet from such a close distance. The encounter velocity is 35 km/s, which is unusually high.  

The graphic below depicts the orbit of asteroid 2015 TB145 (click on the image for a bigger version). 

Credit: (NASA/JPL - Caltech)

The graphic below depicts the passage of asteroid 2015 TB145 past Earth on October 31, 2015 (click on the image for a bigger version). 

Credit: P. Chodas (NASA/JPL - Caltech)

This flyby of 2015 TB145 will be the closest by any known space rock this large until asteroid (137108) 1999 AN10 (absolute magnitude H=17.9) flies past Earth in 2027 within one lunar distance. On April 2017, another asteroid "2014 JO25" (absolute magnitude H=18.1) will pass at about 4.8 LD from Earth. 

I performed some follow-up measurements of this object on 2015, October 26.5, remotely from the Q62 iTelescope network (Siding Spring, Australia) through a 0.50-m f/6.8 astrograph + CCD + focal reducer). Below you can see our image taken with the asteroid at about magnitude +16 and moving at ~ 0.78 "/min (full moon was only 48 degree away from the asteroid). At the moment of its close approach on Oct 31, around 17UT, 2015 TB145 will move at ~ 880 "/min (or about  14.7 deg/hour). Click on the image below to see a bigger version. (North is up, East is to the left).

The chart below shows the path of asteroid 2015 TB145 as it sweeps past Earth at 35 km per second. "During this 20-hour-long period the asteroid's magnitude varies from 10.1 to 12.2, and its proximity to Earth will create a parallax shift of ½° or more. So you won't be able to point your telescope based on this track; instead, you will need to consult another source (for example the MPC website) to generate positions specific to your location" (click on the image for a bigger version). 

UPDATE - November 02, 2015

The radar images from Arecibo indicate the object is spherical in shape and approximately 600 meters (2,000 feet) in diameter and completes a rotation about once every five hours.

Credits: NAIC-Arecibo/NSF

The animated GIF above was generated using radar data collected by the National Science Foundation's 305-meter (1,000-foot) Arecibo Observatory in Puerto Rico. The six radar images used in the animation were taken on Oct. 30, 2015, and the image resolution is 7.5 meters (25 feet) per pixel.

Radar images obtained at the Arecibo Observatory appear to rotate clockwise, which is noticeable by the movement of bright features. “The bright and dark features are indication of surface irregularities. For example, the central dark feature may be a large circular depression, possibly an impact crater”, commented Dr. James Richardson, USRA Scientist in the Planetary Radar Group. 

Scientists observing asteroid 2015 TB145 with NASA's Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, have determined that the celestial object is more than likely a dead comet that has shed its volatiles after numerous passes around the sun. Indeed researchers now estimate that its surface reflects only about 6% of the sunlight that strikes it (most comets have a reflectivity in the range of 3% to 5%, but asteroids are usually considerably higher, around 15% to 20%).

UPDATE - November 03, 2015

Below the new radar animation of asteroid 2015 TB145 obtained by the radar team of Arecibo Observatory on Nov 1, 2015.

Credits: Arecibo Obs/NASA/NSF

by Ernesto Guido

Thursday, October 1, 2015


Following the posting on the Central Bureau's Transient Object Confirmation Page about a possible Nova in Sgr (TOCP Designation: PNV J18033275-2816054) we performed some follow-up of this object remotely through a 0.43-m f/6.8 astrograph + CCD) of  iTelescope network (MPC Code  Q62 - Siding Spring).

On our images taken on September 28.4, 2015 we can confirm the presence of an optical counterpart with R-CCD magnitude 9.5 at coordinates:

R.A. = 18 03 32.77, Decl.= -28 16 05.3

(equinox 2000.0; UCAC4 catalogue reference stars).

Our annotated confirmation image. Click on it for a bigger version:
An animation showing a comparison between my confirmation image and the archive POSS1 Blue plate (1958-04-18). Click here or on the thumbnail below for a bigger version:

PNV J18033275-2816054 photo PNV_Sgr - T17 Q62 - 28 Settembre 2015_zps44qnohhw.gif

According to CBET nr. 4145, issued on 2015, September 30, , PNV J18033275-2816054 is now NOVA SAGITTARII 2015 No. 3. This nova has been discovered K. Itagaki (Teppo-cho,Yamagata, Japan) on an unfiltered CCD frame taken on Sept. 27.429 UT using a 180-mm-focal-length camera lens.

A spectrogram (resolution about 500 at H-beta) taken of PNV J18033275-2816054 by M. Fujii (Kurashiki, Okayama, Japan) with a 0.4-m telescope on Sept. 27.487 UT shows Balmer emission lines, with the H-beta line having a P-Cyg profile that indicates an expansion velocity of about 1100 km/s.  Emission lines of Fe II (37), (42), and (49) also have P-Cyg profiles.  The Na D absorption is remarkable. (see image below).

Credit: M. Fujii

by Ernesto Guido

Wednesday, September 2, 2015

New Comet: P/2015 Q2 (PIMENTEL)

CBET nr. 4140, issued on 2015, September 02, announces the discovery of a comet (magnitude ~18.5) by Eduardo Pimentel on Aug. 24.2 UT with a 0.45-m f/2.9 reflector of the SONEAR Observatory at Oliveira. Follow-up observations to confirm the object were obtained by C. Jacques, E. Pimentel, and J. Barros with the same telescope on Aug. 27.3 and31.3. The new comet has been designated P/2015 Q2 (PIMENTEL).

We performed follow-up measurements of this object, while it was still on the neocp. Stacking of 30 unfiltered exposures, 30 seconds each, obtained remotely on 2015, August 31.7 from Q62 (iTelescope network - Siding Spring) through a 0.50-m f/6.8 astrograph + CCD + f/4.5 focal reducer, shows that this object is a comet with a  sharp central condensation surrounded by diffuse irregular coma 5" in diameter and a tail about 10" in PA 315

Our confirmation image (click on it for a bigger version)

M.P.E.C. 2015-R02 assigns the following preliminary elliptical orbital elements to comet P/2015 Q2: T 2015 Sept. 10.23; e= 0.76; Peri. =  244.36; q = 1.82;  Incl.= 146.18

by Ernesto Guido & Nick Howes