Image: Comet Hartley 2
Rolando Ligustri / CAST-Italia
It is only in the last few days that Comet Hartley 2 has become bright enough to be spotted with binoculars or the naked eye.
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updated 10/19/2010 4:40:11 PM ET 2010-10-19T20:40:11

A fairly bright comet makes its closest approach to Earth on Wednesday, though it may be difficult to spot without clear conditions well away from city lights.

For a few nights at midweek, Comet 103P/Hartley 2 will be perfectly placed in the northeastern sky, in bright circle of stars that form the constellation Capella.

This sky map shows where to look to spot the comet, weather and lighting conditions permitting. Binoculars or a small telescope are advised to obtain the best viewing conditions.

Rare comet encounter
Bright comets are rare, perhaps one every three to five years. It's impossible to tell far in advance how bright a comet may be.

Comet Hartley 2 was discovered by Australian astronomer Malcolm Hartley 24 years ago. It's only in the last few days that it has become bright enough to be spotted with binoculars or the naked eye.

This Comet Hartley 2 skywatching guide describes how to see the celestial event.

It is best viewed with 10x50 to 20x80 binoculars from a dark sky location. If using a telescope, choose the lowest magnification possible.

Like the famous Halley's Comet, Comet Hartley 2 is a periodic comet that follows a years-long loop around the sun. It takes 6.46 years to complete one circuit, compared with Halley's 75.3 years.

Comet's close approach
Unlike some comets, Hartley 2 never crosses Earth's orbit, so it is high in the night sky when it makes its closest approach. It will be closest to the Earth on Oct. 20 at 3 p.m. ET (1900 GMT), and closest to the sun on Oct. 28.

At its closest, Comet Hartley 2 will be only 0.12 astronomical units (11 million miles) from the Earth.

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Because we are seeing this comet pretty much "head on" with the sun behind us, it has little or no detectable tail. It appears as a large diffuse glow in the sky. [New Photos of Comet Hartley 2]

On Nov. 4, this comet will have a visitor from Earth, when the probe Deep Impact does a flyby. It will pass only 435 miles from Comet Hartley 2.

This article was provided to Space.com by Starry Night Education, the leader in space science curriculum solutions.

© 2013 Space.com. All rights reserved. More from Space.com.

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Photos: Month in space: September 2010

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  1. Martian sea of sand

    Near Mars' north pole, the landscape is dominated by sand dunes forming a massive erg, or sand sea, much like parts of the Sahara Desert on Earth. In parts of the erg, sand is abundant and covers the entire surface. Here, near the edge, sand is in shorter supply and the dunes are separated by areas of lighter-toned soil. This color-coded image from NASA's Mars Reconnaissance Orbiter was captured in July and published on Sept. 1. (NASA /JPL/ University of Arizona) Back to slideshow navigation
  2. Dance of the galaxies

    NGC 5426 and NGC 5427 are two spiral galaxies of similar sizes engaged in a dramatic dance. It is not certain that this interaction will end in a collision and ultimately a merging of the two galaxies, although the galaxies have already been affected. Together known as Arp 271, this dance will last for tens of millions of years. This image, released Aug. 30, was taken with the EFOSC instrument attached to the New Technology Telescope at the European Southern Observatory's La Silla facility in Chile. (ESO) Back to slideshow navigation
  3. Crazy cones on Mars

    These Martian volcanic cones are similar in size and shape to cones found in Iceland, where hot lava has run over wet ground. The heat from the lava boils the water, which bursts through the lava flow. These steam-driven exploding bubbles of lava throw chunks of molten and solid lava into the air. A long series of such explosions is needed to build up one of the large cones. This image, released Sept. 1, was taken by a high-resolution camera on NASA's Mars Reconnaissance Orbiter. (NASA via AP) Back to slideshow navigation
  4. Creating Curiosity

    Engineers work on the Curiosity rover at NASA's Jet Propulsion Laboratory in Pasadena, Calif., on Sept. 16. Curiosity, also known as the Mars Science Laboratory, is due to be launched to the Red Planet from Cape Canaveral Air Force Station in Florida in late 2011. (Jae C. Hong / AP) Back to slideshow navigation
  5. Igor the Terrible

    A photo taken from the International Space Station on Sept. 15 shows Hurricane Igor whirling through the Atlantic Ocean hundreds of miles below. In the foreground you can see a Russian spacecraft docked to the space station. (NASA via AFP - Getty Images) Back to slideshow navigation
  6. Dodging a bullet

    An extreme ultraviolet image from NASA's Solar Dynamics Observatory shows an exceptionally heavy plasma eruption on the surface of the sun on Sept. 8. Not to worry, though: The resulting blast of electrically charged particles missed Earth. (NASA/SDA via EPA) Back to slideshow navigation
  7. Bull's-eye on the moon

    A color-coded topographic map based on data from NASA's Lunar Reconnaissance Orbiter shows the 580-mile-wide Mare Orientale, the largest young impact basin on the moon. This basin formed when a projectile hit the moon about 3.8 billion years ago and penetrated deeply into the lunar crust, ejecting huge amounts of material. The image was released Sept. 16 to coincide with the publication of scientific papers about LRO's mission. (NASA / Goddard / MIT / Brown) Back to slideshow navigation
  8. Two flashes from Jupiter

    A fleeting bright dot on each of these images of Jupiter marks a small comet or asteroid burning up in the atmosphere. The image on the left was taken on June 3 by Australian amateur astronomer Anthony Wesley, with a fireball appearing on the right side. The image on the right was taken by Japanese amateur astronomer Masayuki Tachikawa on Aug. 20, with a fireball appearing at upper right. In a report published Sept. 9, NASA said neither event left a lasting mark on the planet. (NASA via Reuters) Back to slideshow navigation
  9. Spiral in space

    A picture from the Hubble Space Telescope, published Sept. 7, shows an unusual spiral nebula around the star LL Pegasi, 3,000 light-years from Earth. Astronomers say the spiral shape was created by material swirling out from one of the stars in a binary-star system. (ESA / NASA) Back to slideshow navigation
  10. Bootprint on Mars?

    Orcus Patera is an enigmatic elliptical depression near Mars' equator, in the eastern hemisphere of the planet. Located between the volcanoes of Elysium Mons and Olympus Mons, its formation remains a mystery. The favored theory is that the feature was created when a comet or asteroid hit the Red Planet at a shallow angle. This picture of Orcus Patera, released Aug. 27, was taken by the European Space Agency's Mars Express orbiter. (ESA) Back to slideshow navigation
  11. NASA's six-legged robot

    The All-Terrain Hex-Limbed Extra-Terrestrial Explorer, or ATHLETE, is a prototype heavy-lift utility vehicle designed to support future human exploration of extraterrestrial surfaces. ATHLETE got a chance to flex its limbs on Sept. 15 in northern Arizona during NASA's Desert RATS field tests. (Robyn Beck / AFP - Getty Images) Back to slideshow navigation
  12. Practicing for Mars

    Geologists Jacob Bleacher and Jim Rice take a close look at a rock formation in northern Arizona before collecting samples on Sept. 5. The geologists took part in NASA's Desert RATS exercise, which is aimed at trying out the equipment and procedures that could come into play during a mission to Mars or other interplanetary destinations. The "RATS" in the name stands for "Research and Technology Studies." (NASA Desert RATS) Back to slideshow navigation
  13. Ice sculptures in space

    Clouds of gas and dust in the Carina Nebula are sculpted into bizarre shapes by stellar radiation, as seen in this image captured by the Hubble Space Telescope and unveiled on Sept. 16. The Hubble team compares the pillars to "cosmic ice sculptures." (NASA, ESA, and the Hubble Heritage Project) Back to slideshow navigation
  14. New York at night

    New York City is ablaze in an image sent by NASA astronaut Doug Wheelock from the International Space Station on Aug. 28. "The City That Never Sleeps," he wrote in a Twitter tweet. "New York, New York on a clear summer night." (Doug Wheelock / NASA via AP) Back to slideshow navigation
  15. Shooting a laser at the sky

    This image, released on Sept. 6, shows a laser beam shooting up from the European Southern Observatory’s Paranal Observatory in Chile. The laser beam is used as a guide for the observatory's adaptive-optics system, which compensates for unsteadiness in the atmosphere to produce sharper astronomical images. (Y. Beletsky / ESO) Back to slideshow navigation
  16. Thar she blows!

    A solid rocket motor that could be used on future NASA launch vehicles is tested Aug. 31 at ATK Aerospace Systems' test site in Promontory, Utah. The rocket motor burned for just over two minutes during the successful static test, producing about 3.6 million pounds of thrust. (ATK) Back to slideshow navigation
  17. The road ahead

    NASA's Opportunity rover looks across a series of sand ripples and bedrock outcrops toward the rim of Endeavour Crater on the horizon on Sept. 6. Opportunity has just crossed the halfway mark in its trip from Victoria Crater to Endeavour. The rover headed out from Victoria in September 2008. (NASA / JPL-Caltech) Back to slideshow navigation
  18. Saturn and its children

    Four of Saturn's moons join the planet for a well-balanced portrait, released by the Cassini orbiter's imaging team on Sept. 10. Saturn's largest moon, Titan, is at lower left. Tethys is at upper right. Two much smaller moons, Pandora and Epimetheus, are barely visible near the rings. (NASA/JPL/Space Science Institute) Back to slideshow navigation
  19. Moon and Earthglow

    A crescent moon is just about to set below Earth's glowing horizon in a picture taken Sept. 4 from the International Space Station. The glow is sunlight scattered by Earth's atmosphere. (NASA via Reuters) Back to slideshow navigation
  20. Twilight of the shuttle

    Photographers gather early on the morning of Sept. 21 to take pictures of the space shuttle Discovery, just after its arrival at the launch pad. Discovery is scheduled to embark on the shuttle fleet's penultimate mission on Nov. 1. The final shuttle flight, involving Endeavour, is set for launch in February - although there's a chance that one additional mission will be flown. (Scott Audette / Reuters) Back to slideshow navigation
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