Wednesday, September 26, 2018

Comets & Asteroids - Summary for August 2018

During the month of August 2018, 4 new comets were discovered, cometary activity was detected for 1 previously discovered object (earlier designated as asteroids) and there  were 2 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

Aug 17 Discovery of C/2018 O1 (ATLAS)     (CBET 4543)
Aug 19 Discovery of P/2018 P3 (PANSTARRS) (CBET 4548)
Aug 19 Discovery of P/2018 P4 (PANSTARRS) (CBET 4549)
Aug 19 Discovery of C/2018 P5 (PANSTARRS) (CBET 4550)

- Cometary activity detected

Aug 14 Cometary activity detected in 2018 KJ3 = C/2018 KJ3 (LEMMON)

- Comet Recoveries

Aug 13  Recovery of P/2010 A1 (HILL) as P/2018 P1 (CBET 4538)
Aug 13  Recovery of P/2001 T3 (NEAT) as P/2018 P2 (CBET 4539)

- Other news

Aug 07  Asteroid (162173) Ryugu imaged on August 07, 2018 from a distance of about 1 km by @haya2e_jaxa - For more info see  #astronomy #asteroids

Credit: JAXA

Aug 10 S. S. Sheppard, Carnegie Institution for Science, reports the discovery of a satellite to the trans-Neptunian object 2013 FY27.  The satellite was detected about 0".17 at a position angle of 135 degrees from the primary in four 545-s images taken with the WFPC3/UVIS instrument with the Hubble Space Telescope during 2018 Jan. 15.058-15.104 UT.  The satellite is about 3 magnitudes fainter than the primary in the F350LP filter.  The projected separation of the satellite is about 9800 km from the primary (CBET 4537)

Aug 17 M. S. P. Kelley and D. Bodewits, University of Maryland; and Q.-Z. Ye, Infrared Processing and Analysis Center, California Institute of Technology, on behalf of the Zwicky Transient Facility (ZTF) Solar System Working Group, report an outburst of comet 64P/Swift-Gehrels in ZTF images taken with the Oschin 1.2-m Schmidt telescope at Palomar. The post-outburst brightness (7"-radius aperture) is r' = 13.88 +/- 0.02, indicating an outburst strength of at least 2.7 mag (CBET 4544)

Aug 20 A Better Look At Asteroid 216 Kleopatra (based on the findings described in the article entitled A revised shape model of asteroid (216) Kleopatra, recently published in the journal Icarus).

Credit: Shepard et al.

Aug 22 Has Anyone Found a Lost Comet?! (based on the papaer "Finding Long Lost Lexell's Comet: The Fate of the First Discovered Near-Earth Object")

Aug 28 NASA's New Horizons spacecraft has made its first detection of its next flyby target, the Kuiper Belt object 2014 MU69 nicknamed Ultima Thule, more than four months ahead of its New Year's 2019 close encounter.  


by Ernesto Guido

Thursday, August 30, 2018

Comets & Asteroids - Summary for June & July 2018

During the 2-month period June through July 2018, 7 new comets were discovered, cometary activity was detected for 1 previously discovered object (earlier designated as asteroids) and there  was 1 comet recovery. "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 09 Discovery of P/2018 L1 (PANSTARRS) (CBET 4521)
Jun 09 Discovery of C/2018 L2 (ATLAS)          (CBET 4522)
Jun 22 Discovery of P/2018 L4 (PANSTARRS) (CBET 4527)
Jul 02 Discovery of P/2018 L5 (LEONARD)     (CBET 4528)
Jul 02 Discovery of C/2018 M1 (CATALINA)   (CBET 4529)
Jul 07 Discovery of C/2018 N1 (NEOWISE)     (CBET 4532)
Jul 16 Discovery of C/2018 N2 (ASASSN)        (CBET 4534)

- Cometary activity detected

Jun 11 Cometary activity detected in 2018 EN4 = C/2018 EN4 (NEOWISE)

- Comet Recoveries

Jun 14  Recovery of P/2005 R1 (NEAT) as P/2018 L3 (CBET 4526)

- Other news

Jun 01 A New Impact Crater – Mars Reconnaissance Orbiter (MRO) keeps finding new impact sites on Mars. This one occurred within the dense secondary crater field of Corinto Crater.

Credit: NASA/JPL/University of Arizona

Jun 02 Small Asteroid 2018 LA (aka ZLAF9B2) IMPACTED Earth on 02 June 2018 

Credit: (CREDIT: Mt. Lemmon Survey - CSS).

Credit: Kokotanekova et al

Jun 09 CBET 4523 & CBET 4536 (Jul 20) report that the following minor planets are binaries systems: (15745) YULIYA & (4666) DIETZ

Jun 12 New paper on Arxiv by Masiero et al.: "Small and Nearby NEOs Observed by NEOWISE During the First Three Years of Survey: Physical Properties".

Jun 14 JAXA Hayabusa2 spacecraft starts sending images of asteroid (162173) Ryugu. Below you can see some images taken from a distance of 700km on June 14, 2018 and from a distance of about 6km on July 20, 2018.

Credit: JAXA

Credit: Jaxa

Jun 26 An asteroid impact triggered an avalanche on Mars as imaged by HiRISE camera on the Mars Reconnaissance Orbiter.

Credit: NASA/JPL/University of Arizona

Jun 27 New results indicate interstellar nomad `Oumuamua is a comet. The first interstellar object discovered in the Solar System, is moving away from the Sun faster than expected.

Credit: Micheli et al.

Jul 13 Radar images of the binary asteroid 2017 YE5 via @AreciboRadar & Green Bank Observatory on June 25 show it consists of two separate objects in orbit around each other that are roughly the same size.

Credit: Arecibo/GBO/NSF/NASA/JPL-Caltech

Jul 17 Jupiter has 10 more moons we didn't know about — and they're weird. The planet now has 79 known moons, including a tiny oddball on a collision course with its neighbours.

Jul 20 Comet C/2017 S3 (PANSTARRS) imaged by Michael Jaeger on July 20, 2018 @ Jauerling, Austria.

Credit: M. Jaeger

by Ernesto Guido

Monday, July 16, 2018

New Comet: C/2018 N2 (ASASSN)

MPEC 2018-O01, issued on 2018, July 16,  announces the discovery of a comet (magnitude ~16.1) in the course of the "All-Sky Automated Survey for Supernovae" (ASASSN) program, in images taken 2018 July 7-11 with the 14-cm "Cassius" survey telescope at Cerro Tololo. The new comet has been designated C/2018 N2 (ASASSN)

I performed follow-up measurements of this object, while it was still on the PCCP webpage. Stacking of 10 unfiltered exposures, 60 seconds each, obtained remotely on 2018, July 15.7 from Q62 (iTelescope network) through a 0.43-m f/6.8 astrograph + CCD, shows that this object is a comet with a diffuse coma about 15 arcsec in diameter.

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

For a different elaboration of this image please click here.

M.P.E.C. 2018-O01 assigns the following preliminary parabolic orbital elements to comet C/2018 N2: T 2019 Oct. 4.09; e= 1.0; Peri. =  23.85; q = 3.00;  Incl.= 78.31

This is the second comet discovered by ASASSN Survey (more info about their first comet are here).

by Ernesto Guido

Sunday, June 3, 2018

Small Asteroid 2018 LA impacted Earth on 02 June

M.P.E.C. 2018-L04 issued on 2018 June 3 at 16:15 UT reports the discovery of the asteroid 2018 LA (discovery magnitude 18.2) by Mt. Lemmon Survey (MPC code G96 - Observer R. A. Kowalski) on images taken on June 02.3 with a 1.5-m reflector + 10K CCD. 2018 LA is a small Apollo asteroid with an estimated size of 1.7 m - 5.2 m (based on the object's absolute magnitude H=30.6).

As reported on this MPEC:  

"This object no longer exists (in its original form), following its entry into the Earth's atmosphere on 2018 June 2.  A news item on the event is in preparation by JPL's Center for Near-Earth Object Studies.  The orbit below, based on only the given astrometric observations, indicates that the object reached 50-km height above the Earth's surface around 16:51 UTC over southern Africa". 

Below you can see the discovery images of 2018 LA (also known by it provisional NEOCP designation ZLAF9B2). The asteroid is the streak just at center of the image, surrounded by the purple circle.

(CREDIT: Mt. Lemmon Survey - CSS).

Below you can see the a map of the possible impact region made by Bill Gray (click on the image for a bigger version). The corresponding impact times and locations are listed here.

Credit: Bill Gray

The yellow circle and X in Botswana mark the lat/lon from the AMS reports (see below).  According to Bill: "The object came in at about altitude 16 degrees above the horizon, at azimuth 98 degrees (a little south of due east). The magenta dots on the plot are again for impact on an airless planet; the actual impact ought to be quite a bit to the east. Which matches the impact reports nicely" and "The magenta impact points run from the Atlantic most of the way through northern Namibia, which is just south of Angola. Shifted eastward after allowing for the fact that the object was presumably seen in the upper atmosphere, they'd move into Botswana."

To date American Meteor Society (AMS) received 8 reports possibly related to entry into the Earth's atmosphere of 2018 LA about a fireball seen over South-East District, Gauteng, North West and Northern Cape on Saturday, June 2nd 2018 around 16:45 UT. In particular one of the reports by Barend Swanepoel contains a video showing the fireball as seen from between Ottosdal and Hartebeesfontein North West South Africa. (another video related to this event and submitted to AMS is visible here ; see also this CCTV camera record from Kuruma Radiators, note that in this video camera time is about 26 minutes behind).

According to Peter Brown: "Strong infrasound detection of a bolide at station I47 in South Africa today at 1730 UT. Origin time between 1645-17 UT over Botswana. Yield 0.3-0.5 kT, corresponding to 2m diameter asteroid".

Credit: P. Brown

This is only the third time in history that an impacting object is observed prior to atmospheric entry. The first time it happened was with asteroid 2008 TC3, the second was with asteroid 2014 AA. Curiously all these 3 events have been discovered by Richard A. Kowalski & Catalina Sky Survey (Richard is also the founder of MPML Minor Planet Mailing List celebrating this year its 20th anniversary). Another space impacting object discovered prior to its to atmospheric entry was WT1190F but it is thought to have been a space debris, possibly  the translunar injection module of Lunar Prospector. For more info about 2008 TC3 and 2014 AA see also:

UPDATE - July 06, 2018

On Saturday, June 23, 2018, after five days of walking and scouring around a team of experts from Botswana, South Africa, Finland and the United States of America recovered a fresh-looking 18-g meteorite in Botswana's Central Kalahari Game Reserve (CKGR). The meteorite is one of the fragments of asteroid 2018 LA which collided with Earth on June 2, 2018 and turned into a meteor fireball that detonated over Botswana a few seconds after entering the atmosphere.

Credit: Peter Jenniskens

This is the third time in history that an asteroid inbound to hit Earth was detected early and only the second time that fragments were recovered. After disruption, the asteroid fragments were blown by the wind while falling down, scattering over a wide area. Calculations of the landing area were done independently by a US-based group headed by Peter Jenniskens, a subject expert of the NASA-sponsored SETI Institute in California, as well as Esko Lyytinen and Jarmo Moilanen of the Finnish Fireball Network (FFN).

Credit: Peter Jenniskens

by Ernesto Guido

Thursday, May 31, 2018

Comets & Asteroids - Summary for April & May 2018

During the 2-month period April through May 2018, 2 new comets were discovered, cometary activity was detected for 2 previously discovered objects (earlier designated as asteroids) and there  was 1 comet recovery. "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 26  Discovery of P/2018 H2 (PANSTARRS)
May 31 Discovery of C/2018 K1 (Weiland)

- Cometary activity detected

Apr 17 Cometary activity detected in A/2018 F4 = C/2018 F4 (PANSTARRS) *
Apr 20 Cometary activity detected in 2018 EF9 = C/2018 EF9 (Lemmon)

* This object initially received the unusual designation A/2018 F4 by G. V. Williams on MPEC 2018-F139 because of the hyperbolic orbit.

See also MPEC 2018-H21: "This object, originally announced as A/2018 F4, is being redesignated as a comet.  K. Sarneczky, Konkoly Observatory, reports that five stacked 120-s unfiltered CCD images taken on Apr. 9.9 UT with the 0.60-m Schmidt telescope at Piszkesteto, Hungary, show a broad fan-shaped coma of diameter nearly 6", elongated toward the east.  R. Weryk (University of Hawaii) reports that images taken with the 3.6-m CFHT on Mauna Kea on Apr. 13.39 UT show that the object has a FWHM of 2".4 (larger than the 1".4 FWHM for nearby stars) and a broad, short tail towards the east".

- Comet Recoveries

Apr 18  Recovery of P/2011 CR42 (CATALINA) as P/2018 H1

- Other news

Apr 16 New paper on Arxiv by Jewitt et al.: "The Nucleus of Active Asteroid 311P/(2013 P5) PANSTARRS".

Credits: Jewitt et al.

Apr 23 New paper on Arxiv by Nesvorny et al.: "Bi-lobed Shape of Comet 67P from a Collapsed Binary".

Apr 24 Dust, stars, and cosmic rays swirling around Comet 67P, captured by the @ESA_Rosetta probe (processing by @landru79)

Credit: Esa Rosetta

Apr 25 Gaia Data Release 2: Observations of solar system objects. The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of solar system objects (SSOs) since the beginning of its operations. Gaia Data Release 2 (DR2) contains the observations of a selected sample of 14,099 SSOs.  The published Gaia data set in data release 2 only contains a selected sample of asteroids, as the observations of many more have already been collected, and will become available in future releases. By the end of the mission there will most probably be more than 300.000, and the accurate positions, 100s times better than in the past, will disclosing new possibility of investigation. The pictures below show a colorful plot of the orbits of the asteroids in Gaia’s second data release (coloured according to perihelion distance), between the Sun and Jupiter. As usual in scaled plots, the Solar System appears crowded and individual lines merge in the region of the Main Belt, between Mars and Jupiter, where most asteroids concentrate. In reality, of course, these asteroid trajectories are millions of km apart.

Credit: Credit: ESA/Gaia/DPAC, P. Tanga

May 07 Silicon Valley Astronomy Lecture: Rubble Piles in the Sky | @michael_w_busch reviews the near-Earth population, programs to track and characterize near-Earth asteroids, and current efforts to address the danger of asteroid impacts. Watch it here on Youtube

May 09 ESO Press Release: Exiled Asteroid Discovered in Outer Reaches of Solar System - ESO telescopes find first confirmed carbon-rich asteroid in Kuiper Belt: "An international team of astronomers has used ESO telescopes to investigate a relic of the primordial Solar System. The team found that the unusual Kuiper Belt Object 2004 EW95 is a carbon-rich asteroid, the first of its kind to be confirmed in the cold outer reaches of the Solar System. This curious object likely formed in the asteroid belt between Mars and Jupiter and has been flung billions of kilometres from its origin to its current home in the Kuiper Belt."

May 11 OSSOS Survey, the complete data release is now published!  Eight hundred and forty precisely defined orbits, with a survey simulator calibrating their detection efficiency. Article by Michele Bannister for @ConversationUK: "How @OSSOSurvey discovered 840 minor planets beyond Neptune – and what they can tell us"

Credit: OSSOS Survey

May 15 New paper on Arxiv by Fern├índez et al.: "Dynamical evolution and end states of active and inactive Centaurs". 

Credit: Fernández et al.

May 21 New paper on Nature Astronomy by Shi et al..: "Coma morphology of comet 67P controlled by insolation over irregular nucleus". Shi et al. study the activity of comet #67P using #Rosetta images, finding that diffuse activity is controlled by sunlight and it can be focused by the roughness of the nucleus' surface to create the nice coma shapes.

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; Nature Astronomy

Credit: Hsieh et al.

May 28 New paper on Arxiv by J. Agarwal & M. Mommert: "Nucleus of active asteroid 358P/Pan-STARRS (P/2012 T1)". 

by Ernesto Guido

Friday, April 27, 2018

Comets & Asteroids - Summary Jan through Mar 2018

During the 3-month period January through March 2018, 12 new comets were discovered, cometary activity was detected for 3 previously discovered object (earlier designated as an asteroid) and there  were 2 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

Jan 11 Discovery of P/2017 Y3 (LEONARD)
Jan 11 Discovery of C/2018 A1 (PANSTARRS)
Jan 17 Discovery of C/2018 A3 (ATLAS)
Jan 17 Discovery of P/2018 A4 (PANSTARRS)
Jan 17 Discovery of P/2018 A5 (PANSTARRS)
Jan 24 Discovery of C/2018 A6 (GIBBS)

Feb 07 Discovery of C/2018 B1 (LEMMON)
Feb 11 Discovery of P/2018 C1 (LEMMON-READ)

Mar 16 Discovery of C/2018 E1 (ATLAS)
Mar 16 Discovery of C/2018 E2 (BARROS)
Mar 19 Discovery of C/2018 F1 (GRAUER)
Mar 28 Discovery of C/2018 F3 (JOHNSON)

- Cometary activity detected

Jan 08 Cometary activity detected in 2017 AB_5 = C/2017 AB_5 (PANSTARRS)
Feb 27 Cometary activity detected in 2011 WG_113 = P/2017 U6
Mar 28 Cometary activity detected in A/2018 C2 = C/2018 C2 (Lemmon) *

* The prefix for  this object is being changed from A/ to C/, following the receipt of the following message from M. Micheli: "We obtained two 60-secondr-fi ltered exposures of A/2018 C2 using the Canada-France-Hawaii Telescope on2018 March 22.6 UT. The queue observer was David Woodworth.  The object iscometary, displaying a broad faint tail of about 10" toward the West. The comais only marginally extended, with a FWHM of 0.9" compared to 0.8" of nearbystars." (ref. M.P.E.C. 2018-F136).

- Comet Recoveries

Jan 17  Recovery of P/2013 CU_129 (PANSTARRS) as P/2018 A2
Mar 22  Recovery of P/2005 JN (SPACEWATCH) as P/2018 F2

- Other news

Jan 5  RIP Thomas J. Bopp (1949-2018), co-discoverer of comet Hale-Bopp in 1995 (with Alan Hale).

Jan 24 Radar images of near-Earth asteroid 2018 AJ  by @AreciboRadar show an elongated body, about 60m x 120m with a considerable brightness variations as it rotates every 45 minutes.

Credit Arecibo/NASA/NSF

Feb 02 New paper on Arxiv by Kim et al.: "Orbital Alignment of Main-Belt Comets". 

Feb 05 RIP Yoshihide Kozai (1928 - 2018), Japanese astronomer specialising in celestial mechanics. He is best known for discovering, simultaneously with Michael Lidov, the Kozai mechanism, for which he received the Imperial Prize of the Japan Academy in 1979.

Feb 08 3.79 billion miles from Earth, New Horizons snapped these images of a pair of Kuiper Belt objects, making them the farthest images ever taken by a spacecraft

"These December 2017 false-color images of KBOs 2012 HZ84 (left) and 2012 HE85 are, for now, the farthest from Earth ever captured by a spacecraft. They're also the closest-ever images of Kuiper Belt objects".


Feb 09 Image & Animation of @SpaceX "2018-017A" a.k.a. #Starman #TeslaRoadster #FalconHeavy #astronomy #spacex. Click on the thumbnails below for a bigger version.

Feb 13 Recent radar images of near-Earth asteroid (505657) 2014 SR339 from @NAICobservatory show a lumpy, elongated body at least 1.5 km long and rotating once every 8 to 9 hours.

Credit Arecibo/NASA/NSF

Feb 21 Radar images of asteroid (3752) Camillo on Feb. 21, 2018 via @AreciboRadar & @NAICobservatory: "Optical observations suggested an elongated body with a slow rotation, but radar reveals an unexpectedly angular, double-lobed shape seen in very few near-Earth asteroids".

Credit Arecibo/NASA/NSF

Mar 05 New paper on Arxiv by Ariel Graykowski & David Jewitt: "Colors and Shapes of the Irregular Planetary Satellites".

Credit Graykowski & Jewitt

Mar 07 Radar images of asteroid "2017 VR12" on March 06, 2018 via @AreciboRadar & @NAICobservatory: "The asteroid is clearly elongated, yet angular, with about 100 to  160 meters visible as it rotates once every 1.4 hours".

Credit Arecibo/NASA/NSF

Mar 14 New paper on Arxiv by Reddy et al.: "Surface Composition of (99942) Apophis".

Credit: Reddy et al.

by Ernesto Guido

Friday, March 23, 2018

Bright Transient in Carina

Following the posting on the ATel #11454 about the discovery by All Sky Automated Survey for SuperNovae survey (ASAS-SN) of a new transient source, possibly a classical nova, near the Galactic plane in Carina (ASAS-SN Designation: ASASSN-18fv) I performed some follow-up of this object through a 0.43-m f/6.8 astrograph + CCD from MPC Code Q62 (iTelescope Observatory, Siding Spring).

On images taken on March 23.4, 2018 I can confirm the presence of an optical counterpart with R-filtered CCD magnitude +5.7 at coordinates:

R.A. = 10 36 15.42, Decl.= -59 35 53.7

(equinox 2000.0; UCAC-4 catalogue reference stars).

Below you can see my confirmation image (single 20-sec exposure through a 0.43-m f/6.8 astrograph + CCD), click on it for a bigger version:

While below you can see a wide-field color image (90 second exposures) I obtained on March 23.4, 2018 through a Takahashi SKY90 Apochromatic Refractor f5/6 + Color CCD. In the image ASASSN-18fv is visible at the centre of the field together with part of the Carina Nebula (click on it for a bigger version):

This transient was discovered using data from the quadruple 14-cm "Cassius" telescope in CTIO, Chile of ASAS-SN survey on images obtained on UT 2018-03-20.32 at V<10 2018-03-16.32="" also="" asas-sn="" asassn-18fv="" at="" detected="" detection="" no="" on="" possibly="" saturated="" starting="" ut="" v="">17.0) of this object in subtracted images taken on UT 2018-03-15.34 and before by the same survey. No previous outbursts or variability are detected at the position of ASASSN-18fv since ASAS-SN started observing this location in February 2016. 

According to Atel #11467 pre-discovery images have been identified on images obtained by Evryscope-South, an array of 6-cm telescopes continuously monitoring 8000 square degrees of sky at 2-minute cadence from CTIO, Chile. The transient is not detected at UT 2018-03-16.0316 with an upper-limit of 11.9 +/- 0.1 mag (g'). Beginning at UT 2018-03-16.227, they detected a new source at 10.21 +/- 0.05 mag (g'). (click on the images below for a bigger version).

Credit: Evryscope
Credit: Evryscope

An animation showing a comparison between my confirmation image and the archive POSS2/UKSTU Red plate (1991-02-10). Click on it for a bigger version:

Spectroscopy by  P. Luckas (see ATel #11460) seems to indicate that ASASSN-18fv is a classical nova brightening and in the optically thick (Fe curtain) phase. 

But according to L. Izzo et al. (ATel #11468): "The lack of a strong blue continuum, that is however typical of classical nova outburst, and the low expansion velocities suggest a possible different nature for this object. The presence of many narrow absorptions also suggests a similarity with other peculiar explosions, like the luminous red variable V4332 Sgr (Martini et al. 1999), the possible luminous red novae V838 Mon and V1309 Sco (Tylenda et al. 2011, Mason et al. 2010) or the 'helium-flash' explosion observed in the Sakurai object (Duerbeck and Benetti 1996)". Doubts about the nova nature of this object were expressed also by J. Strader et al. (ATel #11456)

So further spectroscopic observations are important to clarify the nature of this very interesting transient.

by Ernesto Guido