Prepare to be awestruck as the celestial wanderer, Comet Hartley, returns to its home amidst the stars.

Discovered by Malcolm Hartley in 1986, this captivating Jupiter-family comet has graced our skies with its luminous green glow and enchanting tail.

With a composition mirroring Earth’s water, this 1.6-kilometer giant showcases a symphony of diatomic carbon emissions.

Join us as we embark on a journey to explore the remarkable features and viewing opportunities presented by Comet Hartley’s extraordinary homecoming.

Discovery and Characteristics

Comet Hartley was discovered by Malcolm Hartley in 1986, marking the beginning of its remarkable journey through the solar system. This Jupiter-family comet has an average distance from the Sun of 3.5 astronomical units and last reached perihelion in April 2017.

Its nucleus has a diameter of about 1.6 kilometers (1 mile) and is composed of various volatile compounds. The composition analysis of the comet has revealed the presence of water ice, methanol, carbon dioxide, and possibly methane. Interestingly, the ratio of deuterium to hydrogen in the water from Comet Hartley is similar to that found on Earth.

Further studies of the comet’s nucleus and composition are crucial in understanding the formation and evolution of comets and the solar system as a whole.

Observing Comet Hartley

During the remarkable journey of Comet Hartley through the solar system, it presents a unique opportunity for observers to witness its celestial spectacle.

The apparent brightness of the comet depends on the instrument used for observation. Recent magnitude estimates show it around magnitude 8–8.5 for observers using large binoculars.

The coma, or the fuzzy cloud surrounding the nucleus, balloons to 10′ to 12′ across, providing an expansive field of view under dark skies. However, with larger instruments and more restricted fields of view, the coma may appear smaller and fainter.

Faint-looking comets with large comas can appear dim due to light fanning over a large area. Observers with larger instruments estimate the comet’s visual magnitude to be closer to 9.5–10.

Therefore, a 6-inch or larger telescope (or large binoculars) is recommended for viewing Comet Hartley under a dark sky without strong moonlight.

Special Features and Viewing Opportunities

For observers interested in experiencing a unique celestial event, there are special features and viewing opportunities associated with Comet Hartley’s homecoming.

One notable feature is its close pairing with NGC 2392, also known as the Clown Face Nebula, on October 12th. This close alignment provides a captivating visual spectacle in the night sky.

Additionally, Comet Hartley presents an excellent imaging opportunity for astrophotographers. Its bright green glow from diatomic carbon emission and distinctive short tail make it a compelling subject for capturing stunning images.

Furthermore, October is a favorable time to observe the gegenschein, or counterglow, a phenomenon caused by interplanetary dust. This faint, diffuse patch of light centered on the ecliptic in Pisces below the Great Square of Pegasus adds to the celestial wonders on display during Comet Hartley’s homecoming.

Zodiacal Light and Gegenschein

The phenomenon of the zodiacal light and gegenschein is closely related to the presence of interplanetary dust, adding to the celestial wonders observed during Comet Hartley’s homecoming.

The zodiacal light, which appears as a giant cone of softly glowing light, is caused by interplanetary dust that scatters sunlight along the plane of the solar system. On the other hand, the gegenschein is a brighter splotch of hazy light directly opposite the Sun within the zodiacal band.

To further explore this topic, consider the following points:

  • Zodiacal light visibility:
  • Best observed in the morning sky during October and early November.
  • Broader at its base and tapers with increasing altitude.
  • Continues along the zodiac as the much fainter zodiacal band.
  • Gegenschein photography:
  • Located within the zodiacal band, directly opposite the Sun.
  • Appears as a brighter region of enhanced brightness within the zodiacal band.
  • Best viewed under dark, moonless skies in the southern direction.

Relationship With Comets and Asteroids

Interplanetary dust, originating from comets, asteroids, and Mars, plays a crucial role in the formation of the zodiacal light and gegenschein, further emphasizing the connection between these celestial phenomena and Comet Hartley’s homecoming.

The origin of interplanetary dust can be traced back to comets and asteroids, which release particles as they move through space. These particles become part of the zodiacal cloud, a disc of dust that surrounds the Sun and extends out to the orbit of Mars.

As the Sun’s light reflects off these tiny particles, it creates the zodiacal light, a cone-shaped glow that can be seen in the morning sky. Additionally, gravitational influences from massive bodies, such as Jupiter, can alter the orbits of comets like Hartley, keeping them relatively close to these influential planets.

Understanding the relationship between interplanetary dust, comets, and asteroids allows us to appreciate the interconnectedness of these celestial objects.

Frequently Asked Questions

How Was Comet Hartley Named?

Comet Hartley was named after its discoverer, Malcolm Hartley. The naming process for comets typically involves the discoverer or discoverers submitting a proposal to the International Astronomical Union (IAU) for approval.

What Is the Composition of the Diatomic Carbon (C) Emission That Makes Comet Hartley Glow Bright Green?

Comet Hartley’s green glow is caused by diatomic carbon (C) emission. Spectral analysis reveals the composition of this emission, providing insights into the celestial phenomena. Its bright green color adds to the captivating allure of this celestial spectacle.

What Is the Significance of the Ratio of Deuterium (D) to Hydrogen (H) in Comet Hartley’s Water Compared to Earth’s Water?

The significance of the ratio of deuterium (D) to hydrogen (H) in Comet Hartley’s water, compared to Earth’s water, provides insights into the origin and evolution of water in the solar system. Additionally, the relationship between Jupiter and the orbit of Comet 103P/Hartley keeps the comet relatively close to Jupiter.

How Does the Apparent Brightness of Comet Hartley Vary Depending on the Instrument Used for Observation?

The apparent brightness of Comet Hartley varies depending on the observation instrument used. Magnitude estimates range from 8-8.5 for observers with large binoculars, while those with larger instruments estimate closer to magnitude 9.5-10.

What Is the Relationship Between Jupiter and the Orbit of Comet 103p/Hartley?

Jupiter’s influence on the orbit of comet 103P/Hartley plays a significant role in its orbital dynamics. The gravitational pull from Jupiter keeps the comet relatively close to the planet, affecting its trajectory and ensuring its continued proximity.


In conclusion, Comet Hartley’s homecoming has been a celestial spectacle that has captivated astronomers and stargazers alike. With its glowing green diatomic carbon emission and short tail, this comet has displayed its unique characteristics as it passed closest to Earth.

Observing Comet Hartley has provided an exciting endeavor, offering viewing opportunities such as its close pairing with NGC 2392 and the chance to observe the faint patch of light known as gegenschein.

As we delve into the celestial wonder of Comet Hartley’s homecoming, prepare to be amazed by the beauty of our vast solar system.