Solar Observatories observe the demise of a bright Sungrazer and its many fragments!

On December 21st, both the Solar Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory Ahead (STEREO-A) observed the demise of a bright Sungrazing comet, presumably a Kreutz-group member! Moreover, the comet was accompanied by four small fragments, all which vanished along with this bright comet.

output_zJVm5eAnimation of the bright new Sungrazing comet, and its four tiny fragments (marked by the black lines)!  These were some the last images of these comets before their demise. Image credit: ESA/NASA SOHO/LASCO C2.

The bright comet was discovered in the publically available SOHO/LASCO C3 images on December 19th, by Polish amateur astronomer Szymon Liwo. At the time the discovery images were taken the comet was still very faint, but it quickly brightned over the next couple of days to become a magnificient object!

comet 20171219 discoveryExtract of one of the discovery SOHO/LASCO C3 images of the bright comet (circled). Notice the dense starfield of the Milky Way in the background! Image credit: ESA/NASA SOHO/LASCO C3.

Only several hours before the comet’s demise, Masanori Uchina (Japan) and Worachate Boonplod (Thailand) reported three faint surrounding fragments in SOHO/LASCO C3 and C2 images. The 4th one was reported by yours truly a day later, in SOHO/LASCO C2 images, after having spotted it in STEREO/SECCHI HI1-A frames. However, all fragments appeared best in the SOHO/LASCO C2 images (see animation above).

output_Dx83P8Animation of all 5 comets in STEREO/SECCHI HI1-A diff images. All the four faint fragments are marked by the red lines. One of them is only partially distinguishable from the bright comet. The first one to leave the Field-of-view was discovered in these images. Notice the intense solar outflow entering the FOV. Image credit: NASA/NRL STEREO/SECCHI HI1-A.

All five comets were visible in STEREO/SECCHI HI1-A images. Personally, I found some of them difficult to spot in those images, but they were definitely all there! The comet I reported was perhaps the most difficult to observe (as its clearly the faintest of them all). When I first found it in STEREO, I thought it was one of the previously known 3 fragments, until I noticed those were located elsewhere in these images! I wasn’t convinced by its appearance in STEREO, so I searched for it in SOHO/LASCO C2 images, where it definitely appeared. Hence I reported it in those images.

More than being used to recover all of the four fragments, the STEREO gave us a stunning view of the bright comet. In these images, not only did we observe a long tail (like in SOHO/LASCO), but the tail dynamics were very obvious (see animation below). This is caused by the interaction between the comet and the intense Solar wind.

2017_12_20_kreutz_HI1AAnimation of the bright comet as seen in STEREO’s HI1-A images. Notice how the Solar wind interacts with the comet’s tail, causing it to continuosly move! Notice how some of the fragments are also apparent in these images. Image credit: NASA/NRL STEREO/SECCHI HI1-A.

Like SOHO/LASCO C2, the STEREO/SECCHI CO2-A telescope also captured the comet’s very last moments. Below is an animation of the comet’s diesntigration as seen in these images. The small fragments were too faint to appear in these images.

output_pMOgXZAnimation of four COR2-A frames showing the demise of the bright comet. Image credit: NASA STEREO/SECCHI COR2-A.

The comets are most likely members of the Kreutz-group, a vast family of comets resulting from the continuous fragmentation of a bright sungrazing comet observed millenniums ago. These account for about 85% of all Sungrazing comets observed by SOHO. The family includes many “Great comets”, most notably C/1882 R1, C/1965 S1 (Ikeya-Seki) and C/2011 W3 (Lovejoy)!

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More unknown Nebulae discovered by amateurs online!

Using the publically available images online, such as the Digitalized Sky Survey (DSS) and the Pan-STARRS1 dataset, amateurs have continued to spot previously unknown nebulae that have yet to be catalogued! In this post, I feature Mo Object 2, Pre Object 3, Su Object 1 and Su Object 2. Most, if not all, of these objects are likely somewhat associated with Star forming regions. The nebulae were all found when hunting specifically for Planetary Nebula candidates.

newer nebulae amateursDSS2 and Pan-STARRS1 extracts of Mo Object 2, Pre Object 3, Su Object 1 and Su Object 2. Image credit: DSS2 Skymap.org and the Pan-STARRS1 Science Consortium.

Mo Object 2: A beautiful Reflection Nebula in Auriga, discovered by Sankalp Mohan (India) in the Mid-IR WISE images, in September. The nebula seems to be associated with a small and obscured star forming region.  The object is located within the Auriga Star forming region, rich in many such nebulae, as can be seen in the area surrounding IC 417, also a member of the Auriga Star forming region.

IC 417DSS2 image extract of IC 417, a vast emission nebula assoctiated with a massive star forming region. One can notice many surrounding reflection nebulae (blue nebulosity), similar to Mo Object 2. Image credit: DSS2 Skymap.org.

Pre Object 3: Accidental find when trying to recover Pre Object 2 in Pan-STARRS1 data. It was found by Trygve Prestgard (France) and appears to be a cometary globule. It was found only minutes after having first spotted Pre Object 2, in September, 2017.  This nebula is located in a area rich in active star formation, hence many cometary globules.

Pre object 2 and 3Pan-STARRS1 image extract showing Pre Object 3 (upper left) and Pre Object 2 (low right). Pre Object 3 was found in these images when trying to recover Pre Object 2. Image credit: Pan-STARRS1 Science Consrtium.

Su Object 1: This is a nice fan-shaped nebulosity in Auriga, appearing strongly in Optical Red images. The nebula was found by Guyou Sun (China) in October, 2017, using the DSS2 and Pan-STARRS1 images.

Su Object 2: Another find by Guyou Sun, this is an obvious nebulosity in Cassiopeia. The object is located in an area rich in star formation, with many other interesting nebula nearby. This includes reflection nebulae such as LBN 590 and emission nebula associated to HII regions such as NGC 7822.

LBN 590 and NGC 7822DSS2 image extracts of reflection nebula LBN 590 and star forming region NGC 7822. The latter is actually zoomed-in on a only a portion of the NGC 7822 region, known as the Elephant Trunks, which are vast pillars of star formation. Image credit: DSS2 Skymap.org.

The hunt for unknown nebulae online continues, available to anyone with an internet connection, spare time and lots of patience! Publically available data, even as old as 50 years, still hide many unknown nebulae wating to be discovered!

 

IC 4628 and the land of a thousand Planetary Nebulae!

IC 4628, also known as the Prawn Nebula, is a vast emission nebula in Scorpius. Its large apparent size and its brightness makes it a popular target among astrophotographers in the Southern Hemisphere. Despite having been known for well over a century, it’s only over the past decade (especially these last few years!) that astronomers realized that many small (stellar) Planetary Nebulae lie within its vicinity. Most having been found by amateur astronomers!

prawnAllWISE image extract of IC 4628 and some its neighbouring Planetary Nebulae.  Image credit: Aladin Lite.

Planetary Nebulae candidates DeGaPeKn 1 and 2 were discovered independently by Matthias Kronberger (Austria) and the APO team from France (made up of Thierry Demange, Richard Galli and Thomas Petit). Matthias found the nebulae in mid-IR data from WISE and from Halpha images of the MASH project. The APO team discovered them in their narrow-band SII-OIII-Halpha images of IC4628.

Pre 11 was discovered by Trygve Prestgard (France) in 2016 when re-inspecting the APO team’s narrow band images and the WISE data of the area. The nebula is partially obscured by the nebulosity of IC 4628, making it slightly more difficult to observe. The MASH images of the area were highly contaminated by IC 4628.

Mo 5 was discovered most recently by Sankalp Mohan (India) using the available WISE data. It’s optical brightness is similar to DeGaPeKn 1 and 2, but its Halpha emissions as seen in MASH images are less pronounced.

The two remaining nebulae were discovered by the MASH team a few years before the amateur finds.

Faint Sungrazer twins vanish together!

On November 25th, 2017 two faint sungrazing comets were seen plunging towards the Sun together. Like most small sungrazers, these did not survive their solar encounter. In fact, they most likely vanished before reaching perihelion! The comets were of unequal brightness; the fainter comet leading the brighter one by only half an hour!

twin comets 2017 11 25Strongly cropped and contrasted SOHO/LASCO C2 image extract showing both comets. The brighter one shows hints of a tail, while the faint leading fragment simply appears fuzzy. These are what most sungrazing comets look like in SOHO/LASCO. Image credit: ESA/NASA SOHO/LASCO C2.

Both comets were discovered by Worachate Boonplod (Thailand) via the Sungrazer Project. He found the brighter companion in SOHO/LASCO C3 images of 2017-11-24 (see below). 12 hours later he reported the fainter fragment in SOHO/LASCO C2 images. It’s possible, if not likely, that these fragments split from each other very recently, maybe only decades ago?

Faint sugrazing comets like these represent the majority of comets observed by the SOHO/LASCO coronagraph. Most of these are detected by highly dedicated amateur astronomers via the Sungrazer Project, who spend countless hours scanning the latest SOHO/LASCO images in search for these objects.

soho twin 2017 11 25Image extract of one of the discovery SOHO/LASCO C3 image of the brighter component. The fainter leading fragment is too faint to be readibly visible in this image. Image credit: ESA/NASA SOHO/LASCO C3.

The two comets are most likely a members of the Kreutz-group, a vast family of comets resulting from the fragmentation of a bright sungrazing comet observed millenniums ago. These two comets clearly indicate the fragmentation among Kreutz-group comets is still an ongoing process!

The 2017 return of 96P/Machholz, what did we see?

On October 27th, 2017 comet 96P/Machholz reached its 6th Perihelion passage since it’s discovery in 1986. At the time Don Machholz discovered this comet it had already passed perihelion. 96P/Machholz is a rather unusual comet, in the case of its composition (reltaively low in C2, C3 and Cyanogen) and unusual orbit for a short periodic comet (very inclinated and eccentric).

In this (unusually long) post I will go into some depth regarding the inbound journey and  perihelion passage of 96P/Machholz as seen by the Solar and Heliospheric Observatory (SOHO), Solar TErrestrial RElations Observatory Ahead (STEREO-A) and by  some ground-based observations.

Nota bene: This is an updated version of a Blog post published on this website during the beginning of November.

Ground-based Observations

Before perihelion, the comet was only visible from the Southern-Hempisphere, quickly moving North and rapidly brightening. The comet wasn’t observable for very long, as it stayed extremely faint until about a month before perihelion.  Soon, by mid-October, it entered daylight as seen from Earth.

96P Machholz mattiazzoComet 96P/Machholz imaged by on October 2nd with C11 at f/6.3 + QHY 163m ccd. The comet was estimated to be about mag +15 in this image. (c) Michael Mattiazzo.

Michael Mattiazzo’s (Australia) magnitude measurments from October 8th to October 16th are listed below. Also, on October 2nd he estimated the comet to be about +15 mag. Rob Kauffman (Australia) estimated it to be around +13 mag on October 10th, well in accordance well Michael’s measurments.

Photometric and astronomic measurments of 96P/Machholz by Michael Mattiazzo. Notice the rapid brightening of this object as it rapidly moves towards perihelion.

Date/time UT    Coordinates (J2000.0)   Mag

2017 10 08.41448 13 40 26.50 -44 35 56.9 13.6 N
2017 10 09.42241 13 39 50.58 -43 43 17.8 13.0 N
2017 10 14.41992 13 36 19.45 -38 40 51.7 12.1 N
2017 10 15.41653 13 35 30.95 -37 24 39.3 11.2 N
2017 10 16.41198 13 34 41.12 -36 06 42.9 10.7 N

 

SOHO/SWAN Observations

Days later the comet was already close to +11 mag, and was hence detectable in SOHO’s  SWAN images. In these images it was possible to follow up on the brightening, as the object had passed within the Daylight zone as seen from Earth.  By late October the comet passed behind the “Sun-Occulted zone”, meant to block out the intense Ultraviolet sunlight from saturating the SWAN images.

96P Machholz swanSOHO/SWAN image extracts showing 96P/Machholz brightening as it was approaching the Sun (behind the blacked-out zone). Image credit: ESA/NASA/LATMOS SOHO/SWAN

STEREO HI1-A Observations

At about the same time the comet was passing behind the occulter in SWAN images, on October 23rd, it entered the FOV of the STEREO/SECCHI HI1-A imager. In these images the comet was bright. It was also showing a long (several degrees, and growing) prominent tail. Consequently, by the time the comet had left the FOV on October 24th, the tail was still visible after many hours. Furthermore, one could clearly see the impact of the Solar wind on the comet’s tail, causing it to appear discontinous and curvy.

96P Machholz hi1aComet 96P/Machholz entering STEREO’s HI1-A FOV (October 23rd) and the comet on October 25th when it had already left the FOV. Notice how the tail still persists almost a day after the comet left the FOV! Furthermore, notice the tail’s discontinous and curvy nature, caused by its interaction with the Solar Wind. Image credit: NASA STEREO/SECCHI HI1-A.

SOHO/LASCO observations

On october 25th, only a couple of days before perihelion, the comet entered the SOHO LASCO C3 images. Based on these images the comet appeared close to mag +2. It kept at about this brightness during its passage in SOHO/LASCO. The comet left the SOHO/LASCO C3 FOV on October 29th. In these images it was possible to distinguish two tails.

96P Machholz C3Composite image extract showing comet 96P/Machholz’s at different times when transiting the SOHO/LASCO C3 FOV. Image credit: ESA/NASA SOHO/LASCO C3

Between October 27th and 29th, amateurs reported three faint fragments leading the comet in SOHO/LASCO C3 images. Two of them correspond to 96P/Machholz-B and 96P/Machholz-C, discovered during the comet’s passage in SOHO/LASCO in 2012. The third fragment is a new discovery. The comet’s were solely observed by SOHO, not even STEREO/SECCHI images could detect them.

thumbnail_fragments.jpgSOHO/LASCO C3 (long-exposure) extract showing 96P/machholz and its three faint leading fragments. Two of them correspond to 96P/Machholz-B and C, discovered in 2012. The third one is a previously unknown fragment. Image credit: ESA/NASA/NRL Karl Battams.

Fragmentation events are nothing new to this comet. In fact, it’s likely that the precursors of the Marsden and Kracht-I comet groups were chunks that broke off from 96P/Machholz somewhere around 1000 years ago.

marsden group comet in c2An example of a bright Marsden group comet as seen in a SOHO/LASCO C2 image extract. This comet is possibly a piece of a much a larger chunk that broke off from 96P/Machholz a millenium ago. Image credit: ESA/NASA SOHO/LASCO C2.

 

STEREO COR-A Observations

On October 26th comet Machholz entered the STEREO/SECCHI COR2 FOV. In these images the comet was a prominent object. At its best it appeared to be around mag +2 and showed a long and prominent tail. The comet left the FOV on October 28th.

96P Machholz COR2STEREO COR2-A image extracts showing Comet 96P/Machholz before perihelion and after. Notice the prominent nature of this object in these images. Image credit: NASA STEREO/SECCHI COR2-A.

The comet also rapidly transited the COR1-A FOV on October 27th, near perihelion. Unfortunately the comet was hardly detectable in these images, as the it was practically on the other side of the Sun as seen from STEREO-A.

96P Machholz COR1STEREO COR1-A image extract showing 96P/Machholz. In these images the comet was hardly detectable, this image is perhaps one of the better COR1-A images of it. Image credit: NASA STEREO/SECCHI COR1-A.

Outbound

According to Alan Hale (USA), the comet is expected to stay unobservable from the ground until about February 2018, when the comet will start entering the night sky again. By then unfortunately the comet will have become very faint. Luckily, until then, the SOHO/SWAN images has a good view of the comet. The comet reappeared in SWAN during the beginning of November, appearing bright but fading, while heading Eastward.

96P machholz swan post perihelionSOHO/SWAN image extract of 96P/Machholz only days after it reappeared from behind the occulter. Despite the low resolution of the images, a faint tail is still apparent. Image credit: ESA/NASA/LATMOS SOHO/SWAN.

 

Acknowledgements

I wish to thank Charles Bell, Alan Hale, Michael Mattiazzo and Ian Musgrave for the information they provided to help write (and correct) this post!

Today was the demise of a relatively bright Sungrazing comet!

Today, the Solar and Heliospheric Observatory (SOHO) witnessed the death of a relatively bright Sungrazing comet. Despite this being the case of all ~3400 comets discovered by SOHO, only a small fraction of these were as bright as this one!

bright comet octoberAn image extract showing the comet only hours before it vanished. The comet had already started to fade several hours before this image was taken. Image credit: ESA/NASA SOHO/LASCO C2.

The comet was discovered on 2017-10-13 by amateur astronomers Hanjie Tan (China) and Worachate Boonplod (Thailand) in the real time SOHO/LASCO images online. When it first found, the comet was still very faint, but it brightenened nicely as it kept approaching the Sun. Around 2017-10-13 20:00 UT the comet started rapidly fading.

soho lasco discovery image rel br cometOne of the comet’s discovery images. Image credit: ESA/NASA SOHO/LASCO C3

The comet appears to be a member of the Kreutz-group. These account for about 85% of all Sungrazing comets observed by SOHO. The family includes many “Great comets”, most notably C/1882 R1, C/1965 S1 (Ikeya-Seki) and C/2011 W3 (Lovejoy)!

Previous Planetary Nebula candidate is now a confirmed Galaxy!

In August and September 2017, a team of French astronomers found that one previously classified Planetary Nebula candidate was in fact a Galaxy, most likely a Seyfert Galaxy! The object is named Pre 24, and was discovered by yours truly in August 2016 using the online Digitalized Sky Survey plates.

Pre 24 discovery imageEnhanced discovery image of Pre 24. Notice the arc-like morphology of the object, similar to many Planetary Nebulae. Image credit: Digitalized Sky Survey (DSS) Aladin Lite.

The team consisted of  Pierre Dubreuil ,Olivier Garde, Pascal Le Dû and Alain Lopez. Their mission was to confirm Planetary Nebula candidates via spectroscopy. Among eleven objects studied, seven were confirmed as true Planetary Nebulae, while the remaining four were found to be other objects. Among the latter were two galaxies.

Despite Pre 24 having been initially classified as a Planetary Nebula candidate, there were already hints of the object being a galaxy. This was especially supported by Pan-STARRS1 data when it was made publically available in late 2016. However, it was difficult to be sure, as the object had a morphology and an Infrared signal similar to many Planetary Nebulae. Only the the recently obtained spectra by the French team could confirm its galactic nature. Furthermore, their study revealed the galaxy to be about ~192 million Light years distant!

I’m greatful to Pierre Dubreuil ,Olivier Garde, Pascal Le Dû and Alain Lopez for choosing to study this object, and all the work they put in to confirming the nature of it. Further study of Pre 24 is expected to take place in the future.

 

Reference:

O. Garde, P. Le Dû, P. Dubreuil, A. Lopez (2017) Mission Confirmation de candidates nébuleuses planétaires.

 

New bright sungrazing comet gets vaporized by the Sun!

From September 26-27th, the Solar and Heliospheric Observatory (SOHO) observed a previously unseen Sungrazing comet make a deadly plunge! The comet was discovered by amateur astronomer Worachate Boonplod (Thailand) in the online SOHO/LASCO images.

bright soho comet 20170927A LASCO C2 image extract of the new Sungrazing comet only hours before its demise. Image credit: ESA/NASA SOHO/LASCO C2.

The SOHO spacecraft observes “faint” Sungrazing comets on a daily basis, but only rarely does it observe comets as bright as this one. In average, only a few (at most) such comets are observed yearly!

The comet is most likely a member of the Kreutz-group, a vast family of comets resulting from the continuous fragmentation of a bright sungrazing comet observed millenniums ago. These account for about 85% of all Sungrazing comets observed by SOHO. The family includes many “Great comets”, most notably C/1882 R1, C/1965 S1 (Ikeya-Seki) and C/2011 W3 (Lovejoy)!

New Nebulae discovered by amateurs in online survey images!

Using the publically available DSS2, SDSS and WISE images online, amateur astronomers have been able to find more unknown Galactic Nebulae, including  several Planetary Nebula candidates. Despite the discoveries not yet being official, they have recieved informal designations after their discoverers.

New nebulae pre obj 2 Mo 4 Tan 4 Mo object 1

DSS2, SDSS, Pan-STARRS1 and UKST/Halpha images of the newly discovered nebulae Mo Object 1, Mo 4, Pre Object 2 and Tan 4. Image credit: Wikisky, the SuperCosmos Sky survy and the Pan-STARRS1 Science Consortium.

Alot of the newly found nebulae are likely to be cometary globules, which is notably the case of Mo Object 1, Mo 4 and Pre Object 2. Mo 4 however has some of characteristics that one would expect from a Planetary Nebula, hence its distinct designation. These nebulae were discovered by Sankalp Mohan (India) and Trygve Prestgard (France).

Tan 4 was discovered by Hanjie Tan (China) in Infrared images from the WISE survey, and appears best in the UKST/Halpha images. It’s an elongated nebulosity with an Infrared signal much like that of a planetary nebula, hence it has been classified as a possible Planetary Nebula.

New discovery of an old eruption: Romanov V1

Recently this year, amateur astronomer Filipo Romanov discovered a previously unknown [possible] Dwarf Nova in images taken decades ago! The eruption was “caught” in a couple of old survey images from 1958, and is visible nowhere else.

Romanov V1Cataclysmic variable star Romanov V1 in its discovery image from 1958, in comparison to a later survey image from 1992. Image credit: Digitalized Sky Survey (DSS)

Romanov V1 appeared as a +13 mag star during the 1958 eruption, but during its “ordinary” state it’s fainter than +20 mag. The object hasn’t been observed undergoing an eruption ever since.

Romanov V1 is not the only Cataclysmic Variable to have been found in decades old survey imagery, but it’s one of the brightest examples, known so far! Other fainter examples include DDE 36 and USNO-B1.0 0886-0475568 (see below).

DDE 36 and USNO-B1.0 0886-0475568 UG

Colored DSS2 images showing Dwarf Novae DDE 36 and USNO-B1.0 0886-0475568, each undergoing an eruption. The Blue color is an artefact, not the true color of these stars. Image credit: DSS2 Aladin Lite.