Wednesday, April 7, 2021

V6595 SAGITTARII = NOVA SAGITTARII 2021 No. 2

Following the posting on the Central Bureau's Transient Object Confirmation Page about a possible Nova in Sgr (TOCP Designation: PNV J17581670-2914490) we performed some follow-up of this object through a TEL 0.6-m f/6.5 astrograph + CCD located in the El Sauce Observatory in Chile and operated by Telescope Live network (MPC Code X02).

This transient has been discovered by Andrew Pearce at 8.4 mag (unfiltered) on 2021-04-04.825 UT using a Canon 1100D DSLR camera with a 100mm f/2.8 lens.  Total exposure time was 20 seconds (2 x 10s images stacked). Rob McNaught reported non-detection on 2021-04-02.776 UT (unfiltered limiting mag 11.0).

On images taken on April 06.40, 2021 we can confirm the presence of an optical counterpart with B-filtered CCD magnitude +8.955 (R-filtered & V-filtered images were saturated in 5-second exposures) at coordinates:

R.A. = 17 58 16.08, Decl.= -29 14 56.4

(equinox 2000.0; Gaia DR2 catalogue reference stars for the astrometry).


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



An animation showing a comparison between my image and the archive POSS1 plate (1996-09-12). Made with TYCHO software by D. Parrott. Click on it for a bigger version.





According to ATel #14513,  K. Taguchi et al. obtained a spectrum of this transient on 2021-04-05.828 UT using the fiber-fed integral field spectrograph mounted on the 3.8-m Seimei telescope at Okayama Observatory of Kyoto University. Their spectrum shows Balmer lines, Fe II lines, and the Na I D line. According to their spectrum and the brightness, they conclude that this object is a classical nova (with a spectrum similar to those of the slow nova V1280 Sco in the early stage).

Below is part of the discovery image by A. Pearce showing the nova. The bright stars to the top right are gamma 1 and 2 Sgr.  South is to the top and east to the right. (Click on it for a bigger version)


Credit: A. Pearce


This nova has been designated N Sgr 2021 No. 2 (with permanent GCVS designation V6595 Sgr).


by Ernesto Guido, Adriano Valvasori, Marco Rocchetto

New Comet C/2019 U5 (PANSTARRS)

CBET 4953 & MPEC 2021-G80, issued on 2021, April 07, announce that an apparently asteroidal object (magnitude ~21.0) discovered on CCD images obtained with the F51 Pan-STARRS 1 survey's 1.8m Ritchey-Chretien on 2019, October 22.22 and designated A/2019 U5 (cf. MPEC 2019-V10) has been found to show cometary appearance by other CCD observers over the past half year. The new comet has been designated C/2019 U5 (PANSTARRS).

Stacking of 20 unfiltered exposures, 120 seconds each, obtained remotely on 2021, April 02.1 from Z08 (Telescope Live, Oria) through a 0.7 m f/8 Ritchey Chretien + CCD, shows that this object is a comet with a compact coma about 15" arcsec in diameter (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott)


MPEC 2021-G80, assigns the following orbital elements to comet C/2019 U5 (PANSTARRS): T 2023 Mar. 30.3; e= 1.0003; Peri. =  181.58; q = 3.62 ;  Incl.= 113.51


Credit: MPC


by Ernesto Guido

Friday, March 26, 2021

New Comet C/2020 F7 (Lemmon)

CBET 4949 & MPEC 2021-F110, issued on 2021, March 25, announce that an apparently asteroidal object (magnitude ~21.0) discovered on CCD images obtained with the Mt. Lemmon Survey's 1.5-m reflector on 2020 Mar. 22 and designated A/2020 F7 (cf. MPEC 2020-G78) has been found to show cometary appearance by numerous other CCD observers over the past half year. The new comet has been designated C/2020 F7 (Lemmon).

Stacking of 19 unfiltered exposures, 120 seconds each, obtained remotely on 2021, March 23.9 from Z08 (Telescope Live, Oria) through a 0.7 m f/8 Ritchey Chretien + CCD, shows that this object is a comet with a compact coma about 15" in diameter elongated toward PA 50. (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott)




MPEC 2021-F110, assigns the following preliminary orbital elements to comet  C/2020 F7 (Lemmon): T 2021 Nov. 14.1; e= 0.99; Peri. =  227.97; q = 5.33 ;  Incl.= 93.95


Credit: MPC


by Ernesto Guido 

Tuesday, March 23, 2021

New Comet C/2021 D2 (ZTF)

CBET 4948 & MPEC 2021-F67, issued on 2021, March 22, announce the discovery of an apparently asteroidal object (magnitude ~19.5) on CCD images taken on Feb. 19.5 UT & Mar. 09-5 with the 1.2-m Schmidt telescope at Palomar in the course of the "Zwicky Transient Facility" (ZTF) search program  (the object was reported twice by the ZTF survey team as two different objects) . This object has been found to show cometary appearance by CCD astrometrists elsewhere. The new comet has been designated C/2021 D2 (ZTF).

Stacking of 20 unfiltered exposures, 60 seconds each, obtained remotely on 2021, March 15.2 from I89 (iTelescope, Nerpio, Spain) through a 0.32-m f/8.0 reflector + CCD, shows that this object is a comet with a diffuse coma about 8" arcsec in diameter (Observers A. Valvasori, E. Guido).

Stacking of 12 unfiltered exposures, 90 seconds each, obtained remotely on 2021, March 18.2 from Z08 (Telescope Live, Oria) through a 0.7 m f/8 Ritchey Chretien + CCD, shows that this object is a comet with a diffuse coma about 10" in diameter (possibly elongated toward PA 140). (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).

 

Credit: MPC

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott)



MPEC 2021-F67, assigns the following preliminary orbital elements to comet  C/2021 D2 (ZTF): T 2022 Feb. 4.17; e= 0.99; Peri. =  125.07; q = 2.94 ;  Incl.= 83.84

 

by Ernesto Guido

Saturday, March 20, 2021

Apollo Asteroid 2020 UQ6: A Super Fast Rotator

In the latest issue of Minor Planet Bulletin (VOLUME 48, NUMBER 2, A.D. 2021 APRIL-JUNE), our work on determining the rotation period of asteroid 2020 UQ6 was published. This  asteroid  is  a  Near-Earth  object belonging  to  the  Apollo  group  discovered  at  Tokyo-Kiso Observatory (MPC code 381) on 2020 October 27.

You can read here our paper titled "ROTATIONAL PERIOD AND LIGHTCURVE DETERMINATION OF  2020 UQ6: A SUPER FAST ROTATOR"

CCD photometric observation of 2020 UQ6 were carried  out  in 2×2 binned format during the night between 2020 October 28 and 29 by using the main telescope of the Osservatorio Salvatore di Giacomo,  Agerola  (MPC  code  L07).  It  is  a  0.50-m  Ritchey-Chretien operating at f/8 equipped with an unfiltered FLI-PL4240 CCD camera (2048×2048array of 13.5-micron pixels). 

The software Tycho by D. Parrott, that now offers the ability to construct lightcurves and determine rotation periods, was used during the observing session to extract the light curve of this interesting asteroid almost in real time.

In order to take in account both the high speed of the object (ranging from 21.48  arcec/min  to  17.46  arcsec/min  during  the  measurements) exposure times were kept to 4 s for all sessions. Eight  observation  sessions  collected  1373  data  points  for lightcurve analysis. This led to a bimodal lightcurve with a period of 0.04521 h (162.76 s), or a frequency of 530.84 rev/d, and an amplitude of 0.57 magnitudes. This finding identifies this object as a super-fast rotator asteroid (P << 2 h).

Credit: Guido et al.; MPB

From the absolute magnitude value  of H  =  22.6  and  assuming  the  asteroid  to  be  a  spherical object with a uniform surface and albedo ranging from 0.05 and 0.30, one can gets an estimated diameter ranging from 80 and 180 m.  From  this,  it  is  possible  to  add  the  average  value  of  the estimated diameter, D = 130 m, to the frequency vs diameter plot from  LCDB. As it can be observed, 2020 UQ6 is located in an uncrowded  region  of  the  graph  (identified  by  a  yellow  point), making this object particularly noteworthy. (click on the image below for a bigger version)

Credit: Guido et al.; MPB


by Ernesto Guido, Antonio Catapano, Alfonso Noschese, Antonio Vecchione

Monday, March 1, 2021

New Comet C/2021 C4 (ATLAS)

CBET 4937 & MPEC 2021-D113, issued on 2021, February 26, announce the discovery of an apparently asteroidal object (magnitude ~19) on CCD images taken on Feb. 12.6 UT with a 0.5-m f/2 Schmidt reflector at Haleakala, Hawaii, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program. This object has been found to show cometary appearance by CCD astrometrists elsewhere after the object was posted on the Minor Planet Center's PCCP webpage due to its orbit. The new comet has been designated C/2021 C4 (ATLAS).

We performed follow-up measurements of this object while it was still on the PCCP webpage.

Stacking of 5 unfiltered exposures, 90 seconds each, obtained remotely on 2021, February 22.2 from X02 (Telescope Live, Chile) through a 0.6-m f/6.5 astrograph + CCD, shows that this object is a comet with a compact coma about 8" arcsecond in diameter. (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).

Our confirmation image (click on it for a bigger version; made with TYCHO software by D. Parrott):


Credit: Minor Planet Center
 

M.P.E.C. 2021-D113, assigns the following preliminary parabolic orbital elements to comet C/2021 C4 (ATLAS): T 2021 Jan. 21.04; e= 1.00; Peri. =  320.80; q = 4.50;  Incl.= 132.85


by Ernesto Guido

Tuesday, February 9, 2021

The Dig & Basil Brown's book on Star Charts

A recently (January 29, 2021) released film on the Netflix streaming platform, The Dig, tells the story of the 1939 excavation of Sutton Hoo, the exacavation of the great 7th-century Anglo-Saxon royal ship burial, considered one of the greatest archaeological discoveries in British history. It is a very interesting scientific and human story that will not fail to interest and attract many viewers. On the internet you can find accurate accounts of the events that occurred in Sutton Hoo and that saw as main protagonists local self-taught archaeologist-excavator Basil Brown and landowner Edith Pretty who hired him to tackle the large burial mounds at her rural estate in Sutton Hoo near Woodbridge. 

Credit: B. Brown

For astronomy enthusiasts like the readers of this blog, one of the most interesting facts is certainly that the protagonist of this story, Basil Brown, was not only an archaeologist but also an amateur astronomer. Brown (22 January 1888 - 12 March 1977) joined the British Astronomical Association on 27 November 1918. Through NASA ADS it is possible to find and read some of his astronomical notes and reports published on the BAA Journal (JBAA). 

For example he observed the transit of Mercury across the Sun on 7th May 1924 at Diss, Norfolk, with his only instrument a 2-inch (50mm) refractor (in the film you'll see Ralph Fiennes as Basil Brown carrying around a small telescope). His report to BAA was illustrated with four sketches: "the foregoing is an interesting illustration of the capability of a small telescope in the hands of an enthusiastic amateur".

He also observed meteors, the aurora and the zodiacal light. Basil was also searching for comets as reported in a Notes section of November 1921 of JBAA: "COMET NOTES. -- I have been glad to hear from Mr. Basil Brown that he has spent a good many hours in sweeping for comets. This should be one of the main objects of the sectional workers, especially when no known comets are within reach".

One of the facts that the viewer learns about while watching the movie The Dig, is that Mr. Brown is the author of an astronomy book, specifically a book on Atlases and Celestial Maps. In fact, while Mr. Brown never published any of his archaeological work, "the good reception which greeted his various astrono-mical papers led him to  publish in 1932 the book "Astronomical Atlases, Maps and Charts" a work which the publishers then described as  'filling an inexplicable gap in the literature'".

As it happens, I own a copy of the first edition of the book published in 1932 by Search Publishing Company in London (a reprint was published in 1966). and I think it's interesting to share here some photos of this beautiful book. (click on each image for a bigger version)

Credit: E. Guido

 

This is a book that should not be missing from the shelf of any fan of the history of astronomy (unfortunately it is quite difficult to find) and in particular of that fascinating branch that is the mapping of celestial things. The book, which as the subtitle says is a historical and general guide, is full of references and anecdotes about atlases, star charts and their authors.  As Mr. Brown points out in his introduction (a part is reproduced in the images below): "History is as essential to science as roots to a tree. Modern Astronomy may be likened to a great city built on foundations dating back so far as to be almost as old as the human race". There are also in the book illustrations of the most famous atlases and maps of antiquity. Some chapters are devoted to the mapping of the Moon, the Planets and the Sun.

 

 

Credit: E. Guido

Credit: E. Guido


There are several pages devoted to maps containing information and locations of comets of antiquity. The author provides a whole series of book titles that will help the comet scholar.


By Ernesto Guido