Comet Hale-Bopp (C/1995 O1)

by T. Fujiwara

[JPEG Image]
Comet Hale-Bopp in the pre-dawn sky.
18 March, 1997, 13:55GMT, Fujicolor SuperG 800
30 secconds with 50mm F1.7 lens on a tripod.
Location: Kameoka, Kyoto Pref., Japan

Japanese version

Comet Hale-Bopp has come! This comet was discovered by amateur astronomers Alan Hale and Tom Bopp in July 1995. What was surprising is that the position at that time was so far from the sun: outside the orbit of Jupiter. The brightness was about a hundred times that of Comet Halley placed at the same distance. This means that the comet was intrinsically bright. That is why this comet was discovered in such an early stage.

The nature of a comet is a small icy object of typically 10km in diameter. For example, Comet Halley has a size of about 10km and the size of Comet Hyakutake is estimated to be only a few km. When a comet comes into the planetary system, the surface radiated by the sun's light begins to eject vapor of water and other gases to form a coma. If the surface turns active when the comet get close to the sun, the gas is brown by the solar wind to form a plasma tail, while the dust component in the ejecta is shifted away by the pressure of light and forms a broad dust tail.

Comet Hale-Bopp passes the closest point to the sun on April 1, 1997. The distance is 0.91 AU (Astronomical Unit = the mean radius of Earth's orbit), not small compared with that of Comet Hyakutake, 0.23 AU. Unfortunately, the timing is not good, so that the distance between Earth and the comet at the closest approach in late March is as large as 1.3 AU.

Nevertheless, Comet Hale-Bopp is expected to be a great comet because of its intrinsic brightness. Recent observation suggests that the total magnitude will come up to around 0 mag. This is almost the same as that of Comet Hyakutake in 1996. However, Comet Hale-Bopp will look much clearer because it is apparently compact, not so diffuse as Comet Hyakutake. Moreover, this brightness will remain for a long time (a month or more). Comet Hale-Bopp will be a really enjoyable comet for many people.

In March and April, the comet can be found easily with the naked eye. Since the altitude is not high, good condition such as few city lights and clear sky will be necessary. Using binoculars will help to see the whole comet in detail. If you would like to use a telescope to see a detailed structure of the head, a small magnification such as 20x or 30x would be recommended.

Finder Charts

[Small sample] Position in the pre-dawn sky for February - March (35°N) / B&W version

[Small sample] Position in the pre-dawn sky for February - March (45°N) / B&W version

[Small sample] Position in the evening sky for March - May (35°N) / B&W version

[Small sample] Position in the evening sky for March - May (45°N) / B&W version

[Small sample] Path in February / B&W version

[Small sample] Path in March / B&W version

[Small sample] Path in April / B&W version

[Small sample] Visibility chart (35°N)

[Small sample] Visibility chart (45°N)

[Small sample] Orbital Motion (GIF animaion)
* The orbital plane of the comet is almost perpendicular to that of Earth.

These charts were created with StellaNavigator (ASCII/AstroArts).

Every Month

The comet is in the pre-dawn sky and moves from East to ENE. The brightness will change from 2 mag to 1 mag. This is bright enough for the naked eye. If it is difficult to find the comet, trace bright stars such as Altair, Deneb, and Vega of the triangle. Moonlight will interfere from late February through the beginning of March (full moon is on February 22).

The comet is in the NE of the pre-dawn sky. After middle March, the comet can also be seen in the NW of the evening sky. It will get brighter until its best (0 mag?) in late March. Unfortunately, moonlight would interfere at that time (full moon is on March 24).

The comet is in the NW of the evening sky. It will still be bright (0 mag in early April and 1 mag in late April). Moonlight will interfere in late April (full moon is on April 24).

The comet can be seen in the WNW of the evening sky in early May. The altitude gets lower and lower, so that it cannot be seen after middle May from the northen hemisphere. The brightness will be 2 mag or so. The next return of this comet is in the 44th century!

Related Pages

* Comet Hale-Bopp Home Page
A great page by Ron Baalke, JPL, NASA.
* Comet Hale-Bopp
Comet's page by AstroArts, Japan.
* Recent News and Observations
Reports from around the world (JPL, NASA).
* Light Curve of C/1995 O1 (Hale-Bopp)
Prediction of the brightness (JPL, NASA).

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Last Updated: 1997/2/5
Takao Fujiwara, Kyoto City Univ. of Arts