ScienceDaily (Sep. 30, 2007) — It is nothing new for the ESA/NASA Solar and Heliospheric Observatory (SOHO) to discover another comet – it has already found more than 1350. But the latest is a bit different - SOHO had spotted it twice before. See Also:
Space & Time

• Asteroids, Comets and Meteors
  
• Astronomy
  
• Sun
  
• Solar Flare
  
• Space Missions
  
• NASA
  

Reference

• Comet Hale-Bopp
  
• Comet
  
• Near-Earth asteroid
  
• Near-Earth object
  

For the first time, SOHO’s Large Angle and Spectrometric Coronagraph Experiment (LASCO) has found a rare type of comet called a periodic comet (which flies by the Sun at regular intervals). While many SOHO comets are believed to be periodic, this is the first one that has been conclusively proven and officially declared as such. Astronomers have seen thousands of comets but classified only around 190 as periodic. Many more are proposed to be periodic, but they only gain this classification officially if they are seen to follow their orbits around the Sun more than twice, and have orbital periods of less than two hundred years. The most famous periodic comet is Halley’s comet, returning every 76 years, with its last close pass to the Sun taking place in 1986. SOHO’s new catch has a much smaller orbit, taking approximately four years to travel once around the Sun. It was first seen in September 1999, and then again in September 2003. In 2005, German PhD student Sebastian Hoenig realised that the two comets were so similar in orbit that they might actually be the same object. To test his theory, he calculated a combined orbit for the comet, and consequently predicted that it would return on 11 September 2007. Sebastian's prediction proved to be extremely accurate – the comet reappeared in SOHO's LASCO camera right on schedule, and has now been given the official designation of P/2007 R5 (SOHO). There is a puzzling aspect, however, as the comet does not look exactly like a comet. It has no visible tail or coma of dust and gas. Initially, some scientists wondered if it were actually an asteroid, a chunk of space-rock rather than a chunk of space-ice. However, P/2007 R5 (SOHO) did exhibit some cometary characteristics. As it passed to within 7.9 million kilometres of the Sun, around 5% of the distance from the Earth to the Sun, they observed it brighten by a factor of around a million. This is common behaviour for a comet.So P/2007 R5 (SOHO) seems to behave like a comet, even though it doesn’t really look like one. “It is quite possibly an extinct comet nucleus of some kind,” says Karl Battams, who runs SOHO's comet discovery programme. Extinct comets are those that have expelled most of their volatile ice and have little left to form a tail or coma. They are theorised to be common objects amongst the celestial bodies orbiting close to the Sun. The comet faded as quickly as it brightened, and soon became too faint for SOHO's instruments to see it. Estimates show that P/2007 R5 (SOHO) is probably only 100-200 metres in diameter. Given how small and faint this object is, and how close it still is to the Sun, it is an extremely difficult target for observers on Earth to pick out in the sky. Now we know for certain that P/2007 R5 (SOHO) is there, astronomers will be watching closely for it during its next return in September 2011. Hoenig’s work is detailed in ‘Identification of a new short-period comet near the Sun’ by S.F. Hoenig, published in Astronomy and Astrophysics in January 2006. The credit for discovery and recovery of the object goes to Terry Lovejoy (Australia, 1999), Kazimieras Cernis (Lithuania, 2003) and Bo Zhou (China, 2007). Email or share this story:
| More

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by European Space Agency.

Need to cite this story in your essay, paper, or report? Use one of the following formats: APA

MLA
European Space Agency (2007, September 30). SOHO's New Catch: Its First Officially Periodic Comet. ScienceDaily. Retrieved November 2, 2010, from http://www.sciencedaily.com­ /releases/2007/09/070929162108.htm

Note: If no author is given, the source is cited instead.


An artist's impression of SOHO. (Credit: Credits: SMM (IAC))

Ads by Google
Nano-coating for glass
permanent easy-to-clean coating
anti-lime, hygienic effect
www​.nano-care​.com
Uses of Solar Power
Discover our sun's power and how to
use its energy. Find out more now!
​Knowledge​.​Allianz​.com
Drug Delivery Solutions
40 years helping clients
find drug delivery solutions
www​.elandrugtechnologies​.com
Einstein Brn Mvt Theory
Generalized & Applied to
Interfacial Phenomena
www​.amazon​.com

Related Stories

1000th Sungrazing Comet Discovered By SOHO (Aug. 10, 2006) — Polish amateur comet hunter Arkadiusz Kubczak recently discovered his third comet in SOHO LASCO coronagraph images, but this one was special: the 1000th SOHO comet discovery in the Kreutz group of ... > read more
SOHO Prepares For Comet McNaught (Jan. 12, 2007) — Recently, sky watchers in the Northern Hemisphere have been enjoying the sight of Comet McNaught in the twilight sky. Now, solar physicists using the ESA-NASA SOHO spacecraft are getting ready for ... > read more
SOHO Discovers Its 1,500th Comet (July 1, 2008) — The ESA/NASA SOHO spacecraft has just discovered its 1,500th comet, making it more successful than all other comet discoverers throughout history put together. Not bad for a spacecraft that was ... > read more
SOHO Spacecraft Will Lead A Fleet Of Solar Observatories (May 31, 2006) — New funding, to extend the mission of the European Space Agency's venerable solar watchdog SOHO, will ensure it plays a leading part in the fleet of solar spacecraft scheduled to be launched over the ... > read more
Comet Dives Into Sun: STEREO, SOHO Spacecraft Catch Crash (May 25, 2010) — Solar physicists have used STEREO data to track the path of a sun-grazing comet and have caught it crashing through the corona and chromosophere to evaporate in the ... > read more

Ads by Google