C / 2007 W1 (Boattini)

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C / 2007 W1 (Boattini) [i]
Properties of the orbit ( animation )
Epoch:  May 26th, 2008 ( JD 2,454,612.5)
Orbit type hyperbolic
s. Cape. Orbit
Numerical eccentricity 1,00019
Perihelion 0.850 AU
Inclination of the orbit plane 9.9 °
Perihelion June 24, 2008
Orbital velocity in the perihelion 45.7 km / s
history
Explorer Andrea Boattini
Date of discovery November 20, 2007
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 2007 W1 (Boattini) is a comet that could be seen with the naked eye in 2008 . He is considered to be a serious candidate for an interstellar comet whose origin is not in our solar system .

Discovery and observation

The comet was discovered by A. Boattini at the Mount Lemmon Observatory in Arizona as part of the Mount Lemmon Survey , when he was actually looking for near-Earth asteroids . It was his first comet discovery.

When it was discovered in the border area of ​​the constellations Virgo and Leo , the comet had a brightness of 18 mag and was still about 3.3  AU away from the sun . It was first seen in the night sky, later at dusk , by early February 2008 it had reached a brightness of 14 mag and by early March 13 mag. At the beginning of May no tail had formed, the brightness was 7 mag. The comet moved further into the southern sky and could only be observed from the southern hemisphere at the time it approached the sun in late May and when it flew past it in June . At that time it reached a brightness of 4.5-5 mag and could barely be seen with the naked eye.

From the beginning of July it could be found again at dawn in the northern hemisphere , it had a tail several degrees long, but its brightness was only 5-6 mag and dropped to 10 mag by the beginning of September. He could be observed at least until mid-December.

Scientific evaluation

The chemical composition of the comet was examined in July 2008 with the Near Infra-Red Spectrograph (NIRSPEC) at the Keck Observatory on Mauna Kea . 11 volatile substances ( H 2 O , OH * , C 2 H 6 , CH 3 OH , H 2 CO , CH 4 , HCN , C 2 H 2 , NH 3 , NH 2 , CO ) were found. The abundances of almost all of these substances relative to water showed the highest values ​​ever recorded in a comet. The comet also exhibited complex outgassing behavior. Similar investigations were also carried out with the CRyogenic InfraRed Echelle Spectrograph (CRIRES) on ESO's Very Large Telescope (VLT) in Chile . In a further investigation with the CRIRES at the VLT, the gas production rate of HCN was examined.

In 2003 and 2008, the Canadian Meteor Orbit Radar (CMOR) in Ontario observed two strong daily meteor streams around August 31st, whose orbital elements (except for the eccentricity ) are very similar to those of comet C / 2007 W1 (Boattini ) showed. In both cases, the researchers saw a possible origin of the meteors in Comet Boattini, since its definitely hyperbolic orbital characteristics were not known with sufficient certainty at the time of their investigation. According to later investigations by Królikowska and Dybczyński (see Chapter Orbit), the comet can only be responsible for the meteor shower of 2008.

Orbit

For the comet, a hyperbolic orbit could be determined from 699 observation data over a period of about three quarters of a year , which is inclined by about 10 ° to the ecliptic . The comet's orbit is thus only slightly inclined against the planets of the planets . At the point closest to the Sun ( perihelion ), which the comet passed on June 24, 2008, it was about 127.1 million km from the Sun and was thus in the area between the orbits of Venus and the Earth . Already on June 12th, the closest approach to Earth down to about 0.21 AU / 31.4 million km had taken place and on the following day it passed Mercury at a distance of about 65.3 million km . There were no noteworthy approaches to Venus and Mars .

The comet approached the earth's orbit near the ascending node of its orbit around July 29, 2008 even to a very small distance of about 2.7 million km, which corresponds to almost 7 times the mean distance between earth and moon . The earth did not reach this point of its orbit until almost a month later around August 26th.

According to the orbital elements afflicted with a certain degree of uncertainty, as stated in the JPL Small-Body Database and which do not take into account non-gravitational forces on the comet, its orbit would still have an eccentricity of about 1.000047 before it approached the inner solar system had. Due to the gravitational pull of the planets, in particular through several relatively close passes to the large planet Jupiter on August 30, 2004 at a distance of about 10 AU, Saturn on April 26, 2006 at a distance of about 1.2 AU, and two more times at Jupiter, namely on July 1, 2008 in about 4.3 AU and on July 8, 2011 in about 8.3 AU, its future orbit would be one with elliptical characteristics. This would have an eccentricity of about 0.99951 and a semi-major axis of about 1730 AU, so that the period of rotation would be about 72,000 years.

In a study from 2013, Królikowska and Dybczyński were able to show, using a total of 1703 observations of the comet over a period of 13 months, that the comet's orbit can be described much better if apart from the gravitational influences of all planets and the relativistic effects When the comet passes close by the sun, non-gravitational forces on the comet due to outgassing effects are also taken into account. They obtained the best agreement with the observed positions of the comet by separately considering the observation results before and after the perihelion passage. They used 926 observations to determine a set of orbit elements to describe the comet's orbit up to perihelion, and 777 observations to determine a set of orbit elements to describe the comet's orbit after perihelion. They also determined values ​​for the original and future shape of the orbit long before and after the passage through the inner solar system. As a result, they obtained that the comet was moving on a definitely hyperbolic orbit with an eccentricity of about 1.000037 before it approached the Sun. For the future orbit, they determined an elliptical characteristic with an eccentricity of around 0.99953, a semi-major axis of around 1800 AU and an orbital period of around 77,000 years (uncertainty ± 6%).

In a further study from 2015, they were able to optimize the data somewhat by simulating the cometary dynamics with statistical methods while also taking into account the forces of attraction of the galactic disc and the galactic center, as well as gravitationally disruptive stars in the solar environment, but these additional effects only had one very little influence, so that the aforementioned numerical values ​​could also be approximately confirmed here. They also classified the comet as "dynamic new," meaning that it was the first time it came close to the sun.

In the first study, Królikowska and Dybczyński had already pointed out that this is the only comet among 108 comets they studied up to 2010 with parabolic orbits that originally had a definitely hyperbolic orbit even after eliminating all interfering influences. Also in connection with the study of the unusual chemical composition by Villanueva et al. and the investigation of the daily meteor shower from 2008 by Wiegert et al. (see chapter Scientific evaluation) they saw this as a strong indication that this comet could have an interstellar origin. This was then confirmed again by the second investigation, so that, with today's knowledge, it can be assumed that C / 2007 W1 (Boattini) is a serious candidate for an interstellar comet that came about 2 million years ago at a distance of 120,000 AE has entered the Oort cloud from outside .

See also

Web links

Commons : C / 2007 W1 (Boattini)  - collection of images, videos and audio files

Individual evidence

  1. ^ A. Hale: 427. COMET BOATTINI C / 2007 W1. In: Countdown to 500 Comets. Earthrise Institute, January 28, 2012, accessed July 19, 2020 .
  2. ^ Ch. Rollwagen: Boattini (2008). In: Astro Corner. Retrieved July 19, 2020 .
  3. ^ GL Villanueva, MJ Mumma, MA DiSanti, BP Bonev, EL Gibb, K. Magee-Sauer, GA Blake, C. Salyk: The molecular composition of Comet C / 2007 W1 (Boattini): Evidence of a peculiar outgassing and a rich chemistry. In: Icarus. Volume 216, No. 1, 2011, pp. 227-240 doi: 10.1016 / j.icarus.2011.08.024 .
  4. ↑ M. Lippi: The composition of cometary ices as inferred from measured production rates of volatiles. Dissertation, Braunschweig 2010, ISBN 978-3-942171-37-3 .
  5. ↑ M. Lippi, GL Villanueva, MA DiSanti, H. Böhnhardt, MJ Mumma, BP Bonev, D. Prialnik: A new model for the ν 1 vibrational band of HCN in cometary comae, with application to three comets. In: Astronomy & Astrophysics. Volume 551, A51, 2013, pp. 1-9 doi: 10.1051 / 0004-6361 / 201219903 . ( PDF; 1.00 MB )
  6. ^ PA Wiegert, PG Brown, RJ Weryk, DK Wong: The Daytime Craterids, a radar-detected meteor shower outburst from hyperbolic comet C / 2007 W1 (Boattini). In: Monthly Notices of the Royal Astronomical Society. Volume 414, No. 1, 2011, pp. 668-676 doi: 10.1111 / j.1365-2966.2011.18432.x . ( PDF; 6.54 MB )
  7. ↑ C / 2007 W1 (Boattini) in the Small-Body Database of the Jet Propulsion Laboratory (English).Template: JPL Small-Body Database Browser / Maintenance / Alt
  8. ↑ A. Vitagliano: SOLEX 12.1. Retrieved July 9, 2020 .
  9. ^ C / 2007 W1 Boattini. Solar System Dynamics & Planetology Group, 2013, accessed July 24, 2020 .
  10. ↑ M. Królikowska, PA Dybczyński: Near-parabolic comets observed in 2006–2010. The individualized approach to 1 / a-determination and the new distribution of original and future orbits. In: Monthly Notices of the Royal Astronomical Society. Volume 435, No. 1, 2013, pp. 440–459 doi: 10.1093 / mnras / stt1313 . ( PDF; 1.77 MB )
  11. ↑ PA Dybczyński, M. Królikowska: Near-parabolic comets observed in 2006–2010 - II. Their past and future motion under the influence of the Galaxy field and known nearby stars. In: Monthly Notices of the Royal Astronomical Society. Volume 448, No. 1, 2015, pp. 588-600 doi: 10.1093 / mnras / stv013 . ( PDF; 967 kB )