Comet Hartley 2

Hartley 2 on 30 December 1997
Hartley 2 on 30 December 1997
Image Credit: Tony Farnham / Lowell Observatory

Hartley 2 Rendezvous.

Comet 103P/Hartley 2 will be the next comet to visit the night skies of Earth. Following Comet McNaught, Hartley 2 makes its closest approach to Earth this coming 20 October 2010 and its closest approach to the Sun eight days later on 28 October. Our most recent updates are here, here and here.

Hartley 2 was discovered by Malcolm Hartley in 1986. With a period of about 6.5 years, it returned in 1997 (image at left) and 2004. Following 2010, its next perihelion is expected to be 20 April 2017.

A very nice interactive visualization of the encounter between Hartley 2 and the Earth can be found at the JPL / NASA NEO site.

The comet will pass through the constellation Cygnus, reaching an apparent magnitude of 5. Viewing from a dark location with binoculars should allow you to easily find the comet.

The latest information on the nucleus of Hartley 2 can be found in the 11 May 2010 publication of Astronomy & Astrophysics (manuscript no. 14790tex c). The abstract is at arxiv, and the article can be downloaded as a pdf.

Hartley 2 is the target of the Deep Impact spacecraft, which will make it closest approach (about 700 km) on 4 November 2010. At that point, Hartley 2 will be about 20 million km from Earth, and will be found between the stars Betelgeuse and Procyon.

Deep Impact is famous for its “fireworks” on 4 July 2005 Tempel 1 when it sent a probe smashing into the surface of the Tempel 1 comet, explosively dislodging cometary material for analysis (Image Credit: Credit: NASA/JPL-Caltech/UMD ). The two telescopes and the infrared spectrometer aboard Deep Impact made measurements of Tempel 1 before, during and after the collision.

The data on Tempel 1 was startlingly different from that obtained from comet missions like Deep Space 1 to comet Borrelly and Stardust, which retrieved material from Wild 2.

Deep Impact
The Deep Impact Space Craft
Image Credit: NASA / JPLCaltech

In December 2007, Deep Impact was re-purposed as EPOXI to take on two new tasks.

The first part took place during six months in early 2008. Named Extrasolar Planet Observations and Characterization (EPOCh), the mission used the larger of the two telescopes on the Deep Impact spacecraft to search for Earth-sized planets around five stars selected as likely candidates for such planets.

The second part is the mission to Hartley 2 itself. The Deep Impact Extended Investigation (DIXI) will observe the nucleus of comet Hartley 2, which belongs to a currently undefined class of comets. Interest is high as to whether features of Hartley 2 are similar to Tempel 1. When Deep Impact observed Tempel 1, it found that the comet had vents of water vapor all over its surface, but carbon dioxide vents were found only on one portion of the comet. This is very unusual. The chance to observe Hartley 2 (more active than Tempel 1) with the same instruments will help determine which cometary features represent primordial differences and which result from subsequent evolutionary processes.

On 27 June 2010 the Deep Impact spacecraft passed 18,890 miles above the South Atlantic with a relative speed of 12,750 mph. This was the last gravity assist for the spacecraft.

4 thoughts on “Comet Hartley 2

  1. Pingback: Comet Hartley 2 – Update « The National Space Society of Phoenix

  2. Pingback: Comet 103P/Hartley 2 – 30 Days from Closest Approach « The National Space Society of Phoenix

  3. Pingback: A Snowstorm in Space – Hartley 2 and EPOXI « The National Space Society of Phoenix

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