Comet Hyakutake (1996 B2)
At long last we again have a comet to be excited about:
Hyakutake (1996 B2).
(And possibly Hale-Bopp,
and another Hale-Bopp site, within a year!)
One fact that makes Hyakutake so exciting is that it will pass within ten
million miles of the Earth! On the day of closest approach, March 25, it
will move across 17 degrees of sky. Hyakutake is an infrequent visitor with
an orbital period currently estimated at 16,400 years.
- The next couple of weeks should give us a great show, the skies willing.
With the aid of
The Starry Night I have tried to produce some graphics of interest and usefulness
for observing and understanding Hyakutake.
- One big trick to observing possibly faint objects, such as Hyakutake's
talk, is to use "averted vision": not looking directly at something,
but rather slightly to the side (or above/below) of it.
"There are two kinds of light sensitive cells in the retina, rods
and cones. The cones give us the highest definition and also provide
color vision while the rods are very much more light sensitive.
Most of the retina has a mixture of the two types of cells but in the
center are only cones. We naturally use this high definition region
for reading and other detailed work. Averted vision causes the image
(in this case, of the comet) to fall on the more sensitive rods."
(Thanks to Kevin Patfield for the writeup.)
- For organized Chicago area viewing, there are events:
- near Palatine and
at Adler Planetarium
Also, Adler Planetarium has a
new sky show:
Comets are Coming
- If you can, I really urge you to get out to a "dark sky" site (away from
our light-polluted cities) and get a true look at this comet. (No, I have not
had the pleasure yet. Sigh.) While you are there, take a moment to look
around the rest of the sky. You will be surprised at what we lose thanks
to our wasteful ways:
- Friday March 15th:
- I was finally able to observe the comet from Chicago skies
(limiting magnitude about 4 that night). If you knew right where to
look, you could tell that something was there. The comet was trivial
to observe in low-power binoculars, with a slight hint of a tail.
- Thursday March 21st:
- The afternoon sky was wonderfully clear, but unfortunately some
scattered clouds and haze moved in for the evening. Even so, the
comet was a very obvious object in the eastern sky while standing
in a parking lot. Relocation to a slightly better site (but still
Chicago skies) showed a one-degree wide coma (comet nucleus plus
gas shell) quite well with elongation (hint of a tail) towards
For those who would like a realistic idea of what to expect, I have
attempted to sketch what the naked-eye comet
looked like tonight. The comet is the oblong blob towards the bottom of the
graphic. Arcturus is the bright star towards the top. (Arcturus' size
is exaggerated for viewing purposes. The comet is ten degrees below
Arcturus, and I sized the comet's appearance to match that scale.)
- Friday March 22nd:
- I made it to an almost dark sky site (limiting magnitude 5.5 straight
up, 4 closer to the horizon) a few miles south of Joliet. Tonight,
the comet would be near Izar, with any tail pointing back towards
Arcturus. The comet really had moved in the sky since the previous
night. In fact, the comet's motion over the course of a couple hours
was easily noticable.
While the comet was visible to the naked eye in Evanston, no tail
was visible (even with binoculars), just a slight elongation. At the
darker site, the comet was easily visible to the naked eye. In
addition, a five degree tail was initially visible with averted
vision. After dark adaptation, a fuller tail was visible, extending
about fourteen degrees(!), passing just above Arcturus, ending near
Again, I have made an
image of my observations. The top frame shows what the view was like from
Evanston, the bottom frame is the view that the semi-dark sky site
- Monday March 25th:
- By the time I was ready to go to bed the skies had finally cleared.
Grabbing my binocs, I went downstairs. From the front of the apartment
building the comet was quite visible. A tail of at least seven degrees
was visible in my binoculars.
- Tuesday March 26th:
- Hyakutake was near Polaris (the North Star) tonight (about 3.5
degrees away). The nucleus is not as distinctly visible as it was
previously (more active closer to the Sun? longer line of sight
through the coma now?). With averted naked-eye vision, a tail of
about 7-8 degrees is now available even with the city sky.
(Due to differences in monitors, comet images will be slightly brighter or darker
on your monitor than what I intended, though the general idea will
still be communicated.)
(The general location in the sky should be valid for any site.)
- I have put together an animation of Hyakutake's path through the Chicago
night sky from Marth 15th through April 15th. The green line is the comet's
path on the sky since March 15th. The yellow, connect-the-dots lines are
Hyakutake on the sky: AVI (695kb)
Hyakutake on the sky: QuickTime (750kb)
You can also view individual frames for specific dates.
(Need QuickTime? Check out Cross-platform QuickTime.)
The label in the upper left gives the local (Chicago) time and
location in the sky, for that
The Comet Hyakutake Diary from Abrams Planetarium provides excellent written descriptions
on finding the comet.
The comet and stars will move together across the sky during the night as
the Earth rotates. Additionally, around the time of closest approach
(March 25th), the comet will show motion against the background stars over
the course of just a single night. Because of this motion you should
just utilize the images here as a guide for where in the sky to start
looking, with the emphasis on the constellation background. Finding
the comet from March 20th-28th should not be difficult due to its brightness.
The orbits of the planets about the Sun all lie in roughly the same plane;
the plane of the Earth's orbit has a special designation: the Ecliptic.
The orbit of Hyakutake (purple) lies in a plane nearly perpendicular to the
Ecliptic (green). (The bright star is the Sun.)
A picture of the comet's path (purple) through the inner solar system shows
that it came up through the ecliptic between the orbits of Mars (red) and
(The comet's path will of course be a smooth parabola, rather than a
sequence of straight lines.)
After passing near Earth on March 25th, the comet will then pass by the Sun
on May 1 and swing back down through the Ecliptic, after which it will no
longer be viewable from the Northern Hemisphere.
I have prepared two animations of Hyakutake's voyage through the inner solar
system from the comet's viewpoint.
- In the first animation we ride the comet from March 18th through May 13th
while watching the Earth.
- Hyakutake in the inner solar system: AVI (525kb)
Hyakutake in the inner solar system: QuickTime (670kb)
- The second animation shows the comet's voyage starting from October 21,
1995 through early summer 1996 with the focus on the Sun.
- Hyakutake through the solar system: AVI (4Mb)
Hyakutake through the solar system: QuickTime (3.4Mb)
(Need QuickTime? Check out Cross-platform QuickTime.)
- For further exploration, you can visit one of many Comet Hyakutake
(1996 B2) web pages:
- A quite good article from the Chicago Tribune.
Hyakutake at JPL.
Night of the Comet!
Comet Photography for Everyone
Hyakutake from University of Washington
The March, 1996 Appearance of Comet Hyakutake
What is a Comet? and
The Motion of Comets from the
Comet Shoemaker-Levy 9 Educator's Guide
from Views of the Solar System
- You may also want to explore the virtual night sky yourself:
- The Starry Night (Macintosh) (Check out the balloon help!)
(Orbital elements for comets.)
(For Northwestern University users I have provided a
local mirror of the installation files.)
March 26, 1996 - Robert Lentz