C/2017 O1 (ASASSN) is a comet discovered by the

All Sky Automated Survey for SuperNovae The All Sky Automated Survey for SuperNovae (ASAS-SN) is an automated program to search for new supernovae and other astronomical transients, headed by astronomers from the Ohio State University, including Christopher Kochanek and Krzysztof Stan ...

(ASAS-SN). It was first detected on July 19, 2017, located in the southern constellation

Cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the sky that contains other water-related conste ...

Discovery

During the ongoing ASAS-SN survey, using data from the quadruple 14-cm "Cassius" telescope on

Cerro Tololo The Cerro Tololo Inter-American Observatory (CTIO) is an astronomical observatory located on Cerro Tololo in the Coquimbo Region of northern Chile, with additional facilities located on Cerro Pachón about to the southeast. It is approximately ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

, a possible new moving transient source was detected on July 19, 2017; the team gave it the temporary designation ASASSN1. In the discovery images, C/2017 O1 had a

V band The V band ("vee-band") is a standard designation by the Institute of Electrical and Electronics Engineers (IEEE) for a band of frequencies in the microwave portion of the electromagnetic spectrum ranging from 40 to 75 gigahertz (GHz). T ...

magnitude of 15.3. The centroid was moving between the ASAS-SN three 90 second, dithered discovery images with no counterpart in the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...

database. Follow-up images from the Savannah Skies Observatory recovered C/2017 O1 9.7 hours later 0.21 degrees away. These observations revealed C/2017 O1 had a halo at least 25 arcsec in radius, a compact core, and no clear tail. Further observations were made using the

Las Cumbres Observatory Las Cumbres Observatory (LCO) is a network of astronomical observatories run by a non-profit private operating foundation directed by the technologist Wayne Rosing. Its offices are in Goleta, California. The telescopes are located at both northe ...

1m at CTIO 24.7 hours after discovery which recovered C/2017 O1 at a g-band magnitude of 15.2. C/2017 O1 was then found 0.77 degrees away from C/2017 O1's original location 35.7 hours after discovery. ASAS-SN's Cassius unit re-observed this field 3 days after discovery and found that C/2017 O1 significantly brightened to

11.9 magnitude. In addition to brightening, the coma around C/2017 O1 also increased significantly to 2.5

arcmin A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The nau ...

. Finally, the northern ASAS-SN unit, a quadruple 14-cm "Brutus" telescope on Haleakala Hawaii, observed C/2017 O1 6 days after discovery and found that C/2017 O1 appears to have faded to V~12.2.

Trajectory in sky

The comet was discovered in

in July, moving into

Taurus Taurus is Latin for 'bull' and may refer to: * Taurus (astrology), the astrological sign * Taurus (constellation), one of the constellations of the zodiac * Taurus (mythology), one of two Greek mythological characters named Taurus * '' Bos taur ...

in September, and

Perseus In Greek mythology, Perseus (Help:IPA/English, /ˈpɜːrsiəs, -sjuːs/; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of Mycenae and of the Perseid dynasty. He was, alongside Cadmus ...

and

Camelopardalis Camelopardalis is a large but faint constellation of the northern sky representing a giraffe. The constellation was introduced in 1612 or 1613 by Petrus Plancius. Some older astronomy books give Camelopardalus or Camelopardus as alternative fo ...

in later September and early October. Its perihelion is on October 14, and closest to the earth on October 18. It moves towards the north pole and northern Cepheus into December.

References

MPEC 2017-O45 : COMET C/2017 O1

External links

New Comet: C/2017 O1 ASAS-SN Takes Earth by Surprise
27 Jul, 2017
Sky Surprises: New Comet ASASSN1, Nova in Scutum, and Supernova in Pisces!
July 26, 2017
How to see binocular comet C/2017 O1
September 18, 2017 {{Comets Non-periodic comets Comets in 2017 20170719 Cetus (constellation)