Wednesday, October 11, 2017

New Close Approach by Asteroid 2012 TC4

Asteroid 2012 TC4 was discovered by F51 Pan-STARRS 1, Haleakala on images taken on 2012, Oct. 04.4 with a 1.8-m Ritchey-Chretien + CCD. Just eight days after its discovery, on 2012 Oct. 12, this object passed at about 0.25 LD from Earth

After exactly 5 years, 2012 TC4 will have a new close approach with our planet that will provide astronomers with a valuable opportunity to learn more about its orbit and composition and to test the network of observatories and scientists who work with planetary defense. This asteroid was not observed since the week it was discovered in October 2012 and it has been recovered by astronomers using one of the European Southern Observatory's 8.2-meter telescopes at the Very Large Telescope (VLT) on July 27, 2017 at an apparent magnitude of 26.8 (making it the faintest Near Earth Asteroid so far measured).

Credit: ESO/ESA NEOCC/Hainaut (ESO), Micheli (ESA) & Koschny (ESA)

2012 TC4 has an estimated size of 12 m - 27 m (H=26.7) and it will have a close approach with Earth at about 0.13 LD (Lunar Distances = ~384,000 kilometers) or 0.00034 AU (1 AU = ~150 million kilometers) at 0542 UT on 12 Oct. 2017 and it will reach the peak magnitude ~13. (For comparison, the asteroid that hit Earth’s atmosphere near Chelyabinsk, Russia, in February 2013 was roughly 20 meters across). The rapid rotation and lightcurve amplitude (rotation period of 0.2038 hours with a brightness variation of 0.93 magnitude) suggest that the 2012 TC4 is an elongated, monolithic body (a rubble pile would have spun itself apart). Non-principal axis rotation suggests that it probably has a complex (non-ellipsoidal) shape. 2012 TC4 should be detectable at Goldstone from about Oct. 9 - 16, but not at the moment of closest approach, when it will be too far south for Goldstone to track.

Below you can see my image (single 120-second exposure) of 2012 TC4 obtained on 2017, Oct. 11.35, few hours before its close approach. At the moment of the shot, the asteroid was of magnitude ~15.9 and moving at ~24"/min. The asteroid is trailed in the image due to its fast speed. Click on the image below to see a bigger version. (North is up, East is to the left). 



The short animation below is showing the movement of 2012 TC4 (two consecutive 120-second exposure). Click on the thumbnail below to see the animation (North is up, East is to the left).



Thanks to the new observations following its 2017 recovery, it became clear that new orbit solution precludes a possible impact in 2050: "2012 TC4 would miss the keyhole that would lead to an impact with Earth in 2050. This plot shows the b-plane—the asymptotic location of TC4 relative to the Earth before the Earth's gravity starts bending the trajectory of TC4. The b-plane intersections for progressive orbit solutions is shown by the ellipses (dashed lines show 1-σ uncertainties, solid lines show 3-σ uncertainties), while the red dots show the b-plane coordinates that lead to an impact in 2050. Starting with the Sept 28 solution, the 3-σ uncertainites fall well clear of the red dots, indicating that the asteroid will miss the Earth in 2050. Future impacts beyond that date have not been ruled out."

Credit: The 2012 TC4 Observing Campaign


by Ernesto Guido

Tuesday, September 12, 2017

Comets & Asteroids - Summary for June 2017

During the month of June 2017, 6 new comets were discovered and there were 4 comet  recoveries. "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here). See below for the "Other news" section.

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

- Comet Discoveries

Jun 01 Discovery of P/2017 K3 (GASPAROVIC)
Jun 01 Discovery of C/2017 K4 (ATLAS)
Jun 01 Discovery of C/2017 K5 (PANSTARRS)
Jun 01 Discovery of C/2017 K6 (JACQUES)
Jun 23 Discovery of C/2017 M3 (PANSTARRS)
Jun 23 Discovery of C/2017 M4 (ATLAS)

Comet C/2017 K4 (ATLAS) - E. Guido

- Comet Recoveries

Jun 06  Recovery of P/2000 S1 (SKIFF) as P/2017 L1
Jun 06  Recovery of P/2009 S2 (McNAUGHT) as P/2017 M1
Jun 06  Recovery of P/2010 A2 (LINEAR) as P/2017 B5
Jun 06  Recovery of P/2004 T1 (LINEAR-NEAT) as P/2017 M2


Comet P/2009 S2 (McNAUGHT) - Guido & Sostero


- Other news

Jun 5 CBET 4401 reports that minor planet (9972) MINORUODA is a binary system with an orbital period of 22.89 +/- 0.01 hr.  The primary shows a period of 3.4221 +/- 0.0002 hr and has a lightcurve amplitude of 0.11 mag at solar phases 10-14 degrees, suggesting a nearly spheroidal shape.  Mutual eclipse/occultation events that are 0.06- to 0.13-magnitude deep indicate a lower limit on the secondary-to-primary mean-diameter ratio of 0.24.

Jun 13 CBET 4403 provide the following update by Jenniskens & Lyytinen on expected meteor activity from long-period comet C/2015 D4, now that an improved comet orbit is available (cf. CBET 4127).  Based on an orbit for C/2015 D4 calculated by G. V. Williams from 43 observations spanning 2015 Feb. 23-Oct. 15 (cf. MPEC 2015-U54), the position of the one-revolution dust trail was calculated for the period 1996-2070.  Results show that the dust trail will be in the earth's path on 2017 July 29d00h22m UT (solar longitude 125.858 deg), when the earth passes the center of the trail at a relative distance of only r - Delta = +0.0006 AU; the earth will thus pass inside the comet's orbit at a time when the comet has just passed perihelion, both favorable circumstances for detecting meteors.  Meteors are expected from geocentric R.A. = 79 deg, Decl. = -32 deg, with geocentric velocity 45.9 km/s.


Jun 20 Images of asteroid 6 Hebe taken using SPHERE instrument on ESO ’s Very Large Telescope and related research paper http://bit.ly/2tnC9hR


Credit: ESO/M. Marsset 

Jun 21 New paper on Arxiv by C. Snodgrass et al.: "X-shooter search for outgassing from Main Belt Comet P/2012 T1 (Pan-STARRS)". 

Jun 22 New paper on Arxiv by D. Nesvorny et al.: "Origin and Evolution of Short-Period Comets". In the panel below, extracted from the paper, the orbital distribution of known SPCs. The thin lines show the division between between ECs and NICs (panel b; TJ = 2).

Credit: Nesvorny et al.

Jun 24 CBET 4409 reports that comet C/2015 ER61 (PANSTARRS)  has evidently experienced a splitting: a companion fragment (denoted 'B') was reported by E. Bryssinck (Kruibeke, Belgium) from CCD images taken by F.-J.Hambsch (Mol, Belgium) and himself on June 13, 15, and 16 remotely with a 0.4-m f/6.8 reflector (both unfiltered and with a Bessel R filter) at the private "ROAD Observatory" located at San Pedro de Atacama, Chile; Bryssinck noticed a change over a couple of days in the shape of the nuclear condensation, followed by the appearance of a possible nuclear fragment inside the coma and tail.  On June 13.41 UT, seven exposures show a very faint fragment located 12".3 from the main nuclear condensation in p.a. 243 degrees with a diameter of 8" (magnitude R = 16.5 in an aperture of diameter 5".4).  Seven images taken on June 15.42 show the very faint fragment 13".0 from the main condensation in the same direction and with magnitude R = 16.6 in the same-sized aperture.  Nine images taken on June 16.41 show component B at size 8".8 (with R = 16.6 in a 5".4 aperture) and located 13".4 from component A in p.a. 248 deg.  Component B is difficult to see due its small distance from component A and to its location within the tail.

Credit: ROAD Observatory - Hambsch & Bryssinck

by Ernesto Guido

Friday, August 4, 2017

Comets & Asteroids - Summary for May 2017

During the month of May 2017, 2 new comets were discovered and cometary activity was detected for 1 previously discovered object (earlier designated as an asteroid).  "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here). See below for the "Other news" section.

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

- Comet Discoveries

May 24 Discovery of C/2017 K1 (PANSTARRS)
May 24 Discovery of C/2017 K2 (PANSTARRS)

- Cometary activity detected

May 28 Cometary activity detected in 2016 WM_48 = P/2016 WM_48 (LEMMON)


- Other news 

May 02 H. H. Hsieh reports on CBET 4388 that r'-band observations taken on Apr. 26 and 29 with the Gemini South Observatory (seven 100-s exposures per night; queue observer J. Chavez) show that comet 259P (cf. IAUC 8969; CBET 3115), which has been previously identified as an active minor planet and main-asteroid-belt comet candidate, is currently active. According to CBET 4388: "Including its previously observed active apparition in 2008 (IAUC 8969), these observations mark the second time that comet 259P has been seen to be active.  The fact that 259P exhibits regularly repeated periods of activity, interspersed with periods of quiescence, is a strong indicator that its activity is driven by the sublimation of volatile material, consistent with its initial identification as an ice-bearing main-asteroid-belt comet."

May 18 Hubble Spots Moon Around "2007 OR10", Third Largest Dwarf Planet in the Kuiper Belt. The team's results appeared in The Astrophysical Journal Letters: "2007 OR10 is currently the third largest known dwarf planet in the trans-Neptunian region, with an effective radiometric diameter of ∼1535 km. It has a slow rotation period of ∼45 hr that was suspected to be caused by tidal interactions with a satellite undetected at that time. Here, we report on the discovery of a likely moon of 2007 OR10, identified on archival Hubble Space Telescope WFC3/UVIS system images."

Credits: NASA, ESA, C. Kiss (Konkoly Observatory), and J. Stansberry (STScI)

May 24 CBET 4394 reports that minor planet (190166) 2005 UP156 is a fully-synchronous binary system with an orbital/rotational period of 40.542 +/- 0.008 hr.  The V magnitude was 16.0 on May 4, brightening to 15.2 on May 23.  The out-of-eclipse lightcurve shows an amplitude of about 0.5 magnitude with eclipse attenuations of about 0.6 mag.  The deeper event lasts about 2.8 hours.  The effective secondary-to-primary diameter ratio is estimated to be 0.8 +/- 0.1. 

May 26 A possible impact flash on #Jupiter was imaged by on May 26 by S. Pedranghelu with at least 2 independent confirmations. More info on see our blog post here

Credit: T. Riessler 

May 29 RIP Dr. Michael Francis A'Hearn (1940 - 2017). PI for the NASA Deep Impact; he introduced Afρ parameter for comets.

Credit: M. Mendelsohn

by Ernesto Guido

Tuesday, July 25, 2017

New Comet: C/2017 O1

CBET nr. 4414, issued on 2017, July 24, announces the discovery of a comet (magnitude ~15.3) in the course of the "All-Sky Automated Survey for Supernovae" (ASASSN) program, from images taken with the 14-cm "Cassius" survey telescope at Cerro Tololo on July 19.32 UT. The new comet has been designated C/2017 O1. 

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 60 seconds each, obtained remotely on 2017, July 23.7 from Q62 (iTelescope network) through 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 coma about 3 arcmins in diameter

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



Below you can see the discovery image by ASASSN survey

Credit: ASASSN


M.P.E.C. 2017-O45 assigns the following preliminary parabolic orbital elements to comet C/2017 O1: T 2017 Oct. 14.3; e= 1.0; Peri. =  20.29; q = 1.51;  Incl.= 39.75

Below you can see a graph generated using the software Orbitas and showing the predicted magnitude for this comet (click on the image for a bigger version). Visual estimates have the comet at mag. ~10 on July 24, 2017. Syuichi Nakano, Sumoto, Japan, notes on CBET 4414 that this comet could reach total visual magnitude 7 during September-November. A word of caution: as always with comets, the future magnitudes reported here are only indicative.



by Ernesto Guido 

Wednesday, June 28, 2017

Comets & Asteroids - Summary for April 2017

During the month of April 2017, 7 new comets were discovered. "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here). See below for the "Other news" section.

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

- Comet Discoveries

Apr 02 Discovery of C/2017 D5 (PANSTARRS)
Apr 02 Discovery of C/2017 E5 (LEMMON)
Apr 02 Discovery of C/2017 F1 (LEMMON)
Apr 06 Discovery of C/2017 F2 (PANSTARRS)
Apr 06 Discovery of P/2017 G1 (PANSTARRS)
Apr 21 Discovery of P/2017 G2 (PANSTARRS)
Apr 21 Discovery of C/2017 G3 (PANSTARRS)

- Other news 

Apr 04 More #Rosetta #OpenAccess papers in special issue of Monthly Notices of the Royal Astronomical Society.

Apr 06 New extreme TNO, 2013 SY99, from @OSSOSurvey: a=730±40 au, q=50.0 au, i=4.2°, e=0.93, H=6.8. 

Credit: Michele Bannister


Apr 14 Closest images ever taken of Saturn's moon, Atlas, imaged on April 12, 2017, by @CassiniSaturn

Credit: NASA/JPL-Caltech/Space Science Institute

Apr 18 New paper on Arxiv by Julio A. Fernández et al.: "Physical and dynamical properties of the anomalous comet 249P/LINEAR"

Apr 20 Radar images of 2014 JO25 from @NAICobservatory reveal shadows, possible boulders, and more on this 650+ m (twice as big as previously estimated) asteroid rotating in ~4.5 hours: "Arecibo radar observations revealed the asteroid to have a lumpy, two-lobed shape very reminiscent of Comet 67P/Churyumov–Gerasimenko recently visited by the European Space Agency's Rosetta mission."

Credit: Arecibo Obs./NASA/NSF


Apr 29 CBET 4387 reports that minor planet (2881) is a binary system with an orbital period of 20.42 +/- 0.01 hr.  Mutual eclipse/occultation events that are 0.09- to 0.15-magnitude deep indicate a secondary-to-primary mean-diameter ratio of 0.29 +/- 0.02. 


by Ernesto Guido

Sunday, June 4, 2017

New Comet: C/2017 K4 (ATLAS)

CBET nr. 4397, issued on 2017, June 01, announces the discovery of a comet (magnitude ~17) by the "Asteroid Terrestrial-impact Last Alert System" (ATLAS) Team on CCD exposures taken on May 26.5 with the ATLAS 0.5-m f/2.0 Schmidt telescope at Haleakala. The new comet has been designated C/2017 K4 (ATLAS)

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 120 seconds each, obtained remotely on 2017, May 29.4 from Q62 (iTelescope network) through 0.43-m f/6.8 reflector + CCD, shows that this object is a comet with a diffuse coma nearly 10 arcsec in diameter

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



Discovery animation by ATLAS Survey

Credit: The ATLAS Project

M.P.E.C. 2017-L04 assigns the following preliminary parabolic orbital elements to comet C/2017 K4 (ATLAS): T 2018 Jan. 13.3; e= 1.0; Peri. =  20.42; q = 2.54;  Incl.= 17.19

by Ernesto Guido

Wednesday, May 31, 2017

New Impact Flash on Jupiter

On May 26, 2017 (between 19:24.6 and 19:26.2 Universal Time) a new possible impact flash on Jupiter was imaged by Sauveur Pedranghelu, a French amateur astronomer from Corsica. According to a preliminar analysis by Marc Delcroix (who runs a Jovian impact flashes detection project) this flash, detected in the North polar area of Jupiter, seems shorter than the others (~0.7s vs 1-2s) and displayed two brightness peaks. (click on the images below for a bigger version).




The image by Pedranghelu was then posted online as a call for observations of Jupiter obtained in the same time interval to exclude the possibility that the flare might have been caused by an artefact or flashing satellite. Few hours after the posting, two other observers from Germany (Andre Fleckstein & Thomas Riessler) confirmed independently from one another the finding with their own images. 





Below you can see an animation made by Thomas Riessler using his Jupiter observations showing the impact flash on Jupiter. (click on it for a bigger version). The impact area imaged in the hours after the reported flash showed NO remnants of the impact.


Credit: T. Riessler 

This is not the first time that we have seen something slam into Jupiter, beginning with a fireball recorded by Voyager 1 as it flew past in 1979 (see image below) and the famous impact of Comet Shoemaker-Levy 9 in 1994. 


March 5, 1979 - Fireball in Jupiter's Atmosphere by Voyager 1
Credit: Cook & Duxbury

In this blog we reported about all the recent cases starting from the event of July 19, 2009 (a scar left on Jupiter by an unseen impact observed by Anthony Wesley), of June 03, 2010 (impact flash observed by Anthony Wesley and Christopher Go), of August 20, 2010 (impact flash observed by Masayuki Tachikawa & Aoki Kazuo), of September 10, 2012 (impact flash observed  by Dan Petersen and George Hall), of March 17, 2016 (impact flash observed by Gerrit Kernbauer and John McKeon).

The role of planet Jupiter as a shield protecting Earth from getting hit by such objects is still controversial and it has been discussed in depth in a series of articles by Jonathan Horner and Barrie Jones (Jupiter - friend or foe?).

by Ernesto Guido