PROJECT: The comet C/2003 K4 (LINEAR)

Hristo Stoev Stoev and Nadezhda Lyubomirova Radeva

Fig.2.Leader: Veselka Siderova Radeva,
Astronomical Observatory, Varna, Bulgaria

In this project we have shown the most important and most interesting information about the discovery and movement of a comet that was very bright in 2004 – the comet K4 LINEAR. We have been very interested in comet observations for several years. That is why we are presenting our observations of the comet, that we made during the Astronomical Summer School in August 2004. The most intriguing and enjoyable part of our project is the exercise “Make a comet and eat it”. This amusing exercise about the nature and the movement of the comet was performed with 12 year old students. The main character of the exercise was our comet and we used information that we have gathered for the project in order to show what comets are and how they move in an interesting and unforgettable way. Using the two comet models – a comet from ice cream and a comet from paper we demonstrated to the young students the truth in the old proverb “I heard but forgot, I saw and memorized, I made and that is when I understood”.

3. Historical Highlights
4. Orbital elements
5. We observe the comet
6. Comparison
7. Exercise: “Make a comet, eat it and think”
8. Conclusion
9. Bibliography

Fig.3 Comet C/2003 K4
08/08/2004 20:34:52 exp.120sec Filter: R
Image made by Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

1. Introduction

Comets are the most impressive objects in the Solar system. They, together with asteroids and meteors, belong to the group of small bodies in the Solar system. Bright comets on the night sky are among the most beautiful and breath-taking sights observed in nature! In this project we present to you the bright comet K4 LINEAR that we observed during the International Astronomical Summer School in the National Astronomical Observatory in Rozhen in August 2004.

2. Discovery
The character of our comet story is a comet that was found during the programme LINEAR. The Lincoln Near Earth Asteroid Research (LINEAR) project is an MIT Lincoln Laboratory program funded by the United States Air Force and NASA. The goal of the LINEAR program is to demonstrate the application of technology originally developed for the surveillance of earth orbiting satellites, to the problem of detecting and cataloguing Near Earth Asteroids (also referred to as Near Earth Objects, or NEOs) that threaten the Earth.[1]
The LINEAR program uses a pair of GEODSS telescopes at Lincoln Laboratory's Experimental Test Site (ETS) on the White Sands Missile Range in Socorro, NM. The telescopes are equipped with Lincoln Laboratory developed CCD electro-optical detectors and collected data is processed on site to generate observations. Observations of the comet K4 LINEAR are then sent to the main Lincoln Laboratory site on Hanscom, AFB in Lexington, MA where they are linked from night to night, checked, and sent to the Minor Planet Center (MPC).
Our comet story began in this way:

The LINEAR project announced the discovery of an asteroidal object on images obtained on 2003 May 28.38. The magnitude was given as 17.6. Follow-up observations were obtained by J. McGaha (Tucson, Arizona, USA) and J. Young (Table Mountain Observatory, California, USA). McGaha obtained CCD images on May 29.4 which revealed a nuclear condensation 3 arc seconds across and a coma 6 arc seconds across. He noted that the coma was offset toward the northeast. Young imaged the comet on May 29.5 and May 30.4, and noted a round coma 5-7 arc seconds across, with a total magnitude of 17.5
The comet has been discovered with The GTS-2 Telescope. The GTS-2 telescope is a 1 meter folded prime focus Cassegrain design identical to that of the Ground-based Electro-Optical Deep Space Surveillance (GEODSS) telescope used by the Air Force for space surveillance. It is located at the Experimental Test Site (ETS).[2]

Fig.4 GTS-2 Telescope
credit by:

3. Historical Highlights - history and types of observations

Fig.5 Comet C/2003 K4
08/08/2004 Exp.120sec Filter: B
Image made by Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

• The first orbit was published in IAU Circular 8139 (2003 May 30), which also contained the initial announcement of the comet. It was a parabolic orbit based on 62 positions obtained during the period spanning May 28-30 that gave the perihelion date as 2003 September 11.935 and the perihelion distance as 8.5 AU. The orbit was considered "very preliminary". An improved orbit was published in MPEC 2003-L29 (2003 June 7). Based on 146 positions spanning the period of May 28 to June 6, it gave the perihelion date as 2004 October 13.50 and the perihelion distance as 1.02 AU.

• Following the discovery, the comet was well followed during the remainder of 2003. D. Tirelli (Sossano, Italy) obtained an excellent series of observations using a 25-cm reflector and a CCD camera from July through October, which revealed a brightening from magnitude 17.0 on July 3 to 15.0 on September 16. He reported slightly fainter magnitudes of 15.7 to 15.8 during the latter half of October. Before the end of 2003, R. Ligustri (Talmassons, Italy) observed with a 35-cm reflector and a CCD camera and gave the magnitude as 14.8 on December 12.

• Because of the comet's faintness, it was lost in the sun's glare for a short time and passed 36° from the sun on 2004 January 22. One of the earliest observations in came from J. J. Gonzalez (Leon, Spain) who gave the visual magnitude as 12.7 on February 17.24, while observing with his 20-cm reflector. P. Guzik (Krosno, Poland) saw the comet with his 20-cm reflector on February 21 and gave the visual magnitude as about 12.5. The coma diameter was given as 0.5 arc minute by Gonzalez and 0.6 arc minute by Guzik. Following a period of moonlight, additional observations during the second half of March revealed a magnitude between 12 and 12.5, while the coma diameter was between 0.5 and 1.5 arc minutes.

Fig.6 Comet C/2003 K4
07/08/2004 01:28:58, exp.120s, Filter: I
Image made by:
Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

• The comet continued to slowly brighten during April and May. Observers generally reported a magnitude around 11.5 in the beginning of April, while it had increased to about 11 as the month ended. The coma diameter was generally around 1 arc minute during the first half of April, and was around 1.2 arc minutes as the month came to a close. M. Lehky (Hradec Kralove, Czech Republic) reporting the first observations using binoculars, which had a size of 25x100. In addition, on April 27, Walter Kutschera (Germany) reported a tail about 1 arc minute long. On May 1, observers generally estimated the magnitude as 11, while the coma was perhaps 1.2 arc minutes across. During the last days of May most observers estimated the magnitude as between 9.7 and 10.0, while the coma diameter was around 2.5 arc minutes.

• Up to this point in the comet's brightness evolution, the visual observations could be represented by a fairly uneventful curve that indicated a potential maximum brightness of 7 during October of 2004, but this all changed a few days into June. By June 4, the comet had brightened to a magnitude of approximately 9.5 andwas displaying a coma about

3.5 arc minutes across. For the most part these figures seem to have been carried over into the early hours of June 5. Late on June 5, several observers were indicating a magnitude of 8.5 or brighter, while the coma was at least 4 arc minutes across. The comet seemed to have changed only slightly in brightness by the 6th, while some observers were reporting a coma 8 arc minutes across. Many observers were now watching the comet with 7x50 binoculars and saw the comet attain a magnitude of 8 by mid-June and around 7.3-7.5 by the end of the month. Also, by the end of June, most observers were reporting a coma at least 10 arc minutes across, while the tail extended about 12 arc minutes toward PA 140°.

Fig7. Comet C/2003 K4
08/12/2004 exp.120s Filter: V
Image made by: Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

• The comet continued to steadily brighten as July began. Starting out at magnitude 7.3-7.5, it was actually seen with the naked eye by Piotr Guzik (Krosno, Poland) on July 12 at magnitude 6.8. Guzik had also provided a fine series of observations made with his 10x50 binoculars since July began, which consistently revealed a coma diameter of 15 arc minutes and a tail of about 0.5°. On July 4, J. Bortle (New York) also noted a very faint outer coma 15 arc minutes across and a bright, well condensed inner coma about 8 arc minutes across. The comet seemed to have displayed a very slow brightening as July progressed and, by the end of the month, it seemed to have finally reached magnitude 6.5. The coma was then generally estimated as 5 arc minutes across by observers using telescopes and 15 arc minutes across by observers using binoculars. These numbers changed little through mid August.

• A newcomer to the Solar system, C/2003 K4 LINEAR reaches perihelion on October 14th 2004. This occurs on the opposite side of the Sun and thus will not become a bright object from Earth's point of view. On June 1st 2004, the comet was situated in Lyra and shone at about 10th magnitude. It gradually brightened as it traversed the constellation of Hercules. By July 5th, the comet could be observed in Bootes and it was visible in the northern evening sky at about 8th magnitude. It crossed into Coma Berenices on Aug 11th, about 5 degrees east of the globular cluster pair M53 and NGC 5053. On August 20th, the comet was situated in Virgo and shone at magnitude 6.5. The comet was lost in the evening twilight by the middle of September.
Between September 28th and October 10th, the comet was visible in the SOHO LASCO C3 Coronagraph. You can see real-time movies from this period at:
At the end of October 2004, LINEAR was picked up in the constellation of Corvus in the morning sky and at peak brightness of about magnitude 5.5.
Nov to mid Dec 2004
Comet 2003 K4 LINEAR should maintain a constant brightness of approximately magnitude 5.5-6.0 and be a nice binocular-telescopic sight in the morning sky. Naked eye observations may be possible at this time. By early December, Comet 2003 K4 becomes visible low in the south-eastern late evening sky, trekking through the rich milky way regions of Vela, but still better viewed before dawn. This was the opportunity to observe both 2003 K4 and 2004 Q2 with the naked eye simultaneously although this was quite an observing challenge.
Mid to Late December 2004
Preferably observed before dawn as moonlight interferes during evening hours.The comet is in Carina and it shines at approximately magnitude 6.0-6.5.
Note close approach to open star cluster NGC 2516 on Christmas night.
Jan 2005
The comet shines around magnitude 6.5-7.0 by the start of January and it is in the southern evening sky. It rapidly fades as it recedes from both Sun and Earth.

4. Main characteristics - Orbital Elements of C/2003 K4

The orbital elements are taken from MPC 52 315. From 2244 observations 2003 May 28-2004 July 9 the following orbital parameters have been calculated. We will show some of them that will give us a notion of the comet's orbit.[3]

C/2003 K4 (LINEAR)
Epoch 2005 Jan. 30.0 TT = JDT 2453400.5
T 2004 Oct. 13.7148 TT
q 1.023637
e 1.000324
Node 18.6754
Incl. 134.2527

Fig.8 Comet C/2003 K4
08/11/2004 Exp.120 sec Filter R
Image made by Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

From these orbital elements we can understand that the comet was closest to the Sun at a distance of 1.0236 AU and this means that it was in the Earth's orbit. From the eccentricity we can understand that the comet had a parabola that was near to a hyperbola. The inclination of the comet's orbit to the elliptical plane is 134.2528 degrees. The comet passes closest to Earth on 2004 December 23 (1.15 AU).

5. We observe the comet:
We: Nadezhda, Hristo and Mrs Radeva, are members of the Bulgarian group of comet observers. We make visual, photographic and CCD observations of bright comets. We observed the comet K4 LINEAR with the Schmidt telescope whose mirror’s diameter is 50 cm and the focal length is 172 cm. We made several observations in different filters and with different exposures. We have been interested in astronomical observations for 4 years and have observed numerous comets. That is why we found this comet very interesting and beautiful. The comet images are presented in our small comet gallery.

Fig.9. Comet C/2003 K4
07/08/2004 23:45:01 Exp.120s Filter: R
Image made by Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

Fig.10 Comet C/2003 K4
08/11/2004 19:34:54 exp. 120 Filter: R
Image made by Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

Fig.11 Comet C/2003 K4
08/12/2004 20:17:05 exp. 120s Filter: V
Image made by Veselka Radeva,
Nadezhda Radeva and Hristo Stoev

Fig.12 Comet C/2003 K4
08/12/2004 20:06:58 Exp.180s Filter: V
Image made by Veselka Radeva,
Nadezhda Radeva and Hristo Stoev
6. Comparison:
We decided to compare our comet with other comets. We chose famous comets that we have observed visually and/or with a telescope.
For us it was very interesting to find information that describes the following comets: Hale-Bopp, Ikeya-Zhank and Machholz, and to compare them with the comet K4 LINEAR.[4];[5];[6];[7]
Type of orbit
Types of tails
Closest passage to the Sun
Ion and dust
2004 Oct 14th
Comet Hale-Bopp
4 200 years
Elliptic, close to parabola
e = 0.995068
Ion and dust
137121300 km – 01.04.2001
367.17 years
Elliptic, close to parabola
e= 0.990062
Ion and dust
76 million kilometers-18.03.2002
C/2004 Q2 (Machholz)
No data found
Elliptic, close to
e= parabola 0.999473
Ion and dust
2005 Jan. 24

Fig.13 Part of the class
photo:Nadezhda Radeva
7. Exercise: “Make a comet, eat it and think”
The exercise aims at developing new skills in students, which can happen through using multimedia (computers and Internet) with practical tasks for creating a model of comets. The exercise was prepared by the authors of this project and has been conducted at school with 12 year old students who study astronomy. The exercise provoked great interest and the students made models of comets and participated in the discussion of the problems with pleasure.
Overview: Using ice cream students explore the anatomy of a comet. Students will learn the basic components of a comet. They will demonstrate how the comet’s head and tail from by building two comet models. Students will learn how the comet turns around the Sun.
Objective: To construct an edible model of a comet; to determine the anatomy of a comet; to discuss the comet orbit

Fig.14 The comet's nucleus
photo:Nadezhda Radeva
1. Collect the necessary ingredients as described in the materials list
2. Prepare the materials necessary for the creation of the comet from either ice cream, biscuits, walnuts and sugar, or from paper, tape and thin bands.
3. Take a sheet of cardboard and make the orbit of the comet K4 LINEAR, make small comets and put them on different places on the comet orbit. Thus you can show the development of the comet head and the comet tail.
4. Process the comet images, for example we processed the images received with 50/70 cm Schmidt telescope, so that you can understand the nature of the comet and the changes that happen with comet on its way toward the Sun.
5. Prepare the Comet Fact sheets
2 kg chocolate ice cream -
2 packets of biscuits – the biscuits should be in small pieces
0.5 kg nuts – the walnuts should be ground
12 plastic cups
24 plastic spoons
2 sheets of paper
Yellow and blue bands
Cloth or paper towels
Images of the comets

Fig.15 The necessary materials
photo:Nadezhda Radeva

1. Put a spoon of chopped biscuits and walnuts in a plastic cup. Put 2 spoons of ice cream. Using the ice cream form the inner part of the comet nucleus.
2. Put more chocolate ice cream in the cup. With the help of two spoons form the comet nucleus
3. Observe the various forms of comet nuclei made by different students
4. Discuss what the nuclei of real comets are made from. Show an image of Halley comet’s nucleus on the computer. The ingredients used to build a comet represent our current understanding of the components found in actual comets: frozen water, frozen carbon dioxide and other frozen gases, dust and rock, and organic (carbon-based) substances.
5. Discuss and compare the density and the size of comet nuclei and the comet nuclei made with ice cream.
6. The ice cream model of a comet’s nucleus is very delicious!


Fig.16 - Creation of the nucleus - Step1

Fig. 17- Creation of the Comet - Step 2

Fig.18 - Comet from ice cream - Step 3

Fig.19 Demonstration of a comet's tail-Step 8
photo:Nadezhda Radeva
7. Make a model of a comet using a sheet of paper and put a long yellow band (the comet tail)
8. Turn on the hairdryer in front of the comet so that the jet of air raises the bands. Explain that the jet of air is like the solar wind that leaves the Sun and fills out the interplanetary space. This explains why comet tails are always in a direction opposite the Sun.
9. Discuss the orbit of K4 LINEAR – it is always a parabola. Examine the position of each comet made with paper and discuss the fact that the size of the coma and the length of the tail increase and the fact that the direction of the tail is always opposite the Sun, Discuss the different speed of the comet on its orbit and pat attention on the fact that when the comet is in perihelion (the point on the comet’s orbit that is closest to the Sun) it travels fastest (second law of Coupler). Using the orbit elements calculate the distance between the comet and the Sun when the comet is in perihelion.
10. Examine and compare the received images of the comet K4LINEAR and images of other comets with large bright comet tails. Discuss the similarities and the differences in the comets’ orbital parameters and the changes in the comet tails. Use the table in the project for the comet K4LINEAR and other famous comets.
11. Ask the Reflection Questions to reinforce the parts of a comet.

Fig.20.Discuss the orbit of a comet-Step 9
photo:Nadezhda Radeva

... ...
Fig. 21. Dessi's comet, Fig.22. Ivan's and Emilian's comet Fig.23 This delicious comet…
photos:Nadezhda Radeva

Reflection Questions
1. What does the ice cream represent? The chopped biscuits? The ground nuts?
2. Was there a dust tail in this comet? Why not? Did you observe a gas tail or coma?
3. How was the comet model like a real comet? How was it different?
4. How would this comet nucleus change as it enters the inner Solar System?
5. How do the brightness of the comet and the size of the tail change on the comet’s way on its orbit?
6. What types of tails exist?
7. What types of comet orbits exist?
8. What do comets have in common? How are comets different?
9. Do you think that a comet may impact a planet sometime in the future? Why or why not?
10. Does a comet’s tail ever point towards the Sun? Why not?

8. Conclusion:
The work on the project 'Comet K4LINEAR was very interesting and exciting. We found many books, in which we read a lot about comets; we saw many web-pages for this comet.
For us it was very interesting to learn how the comet moves and what the nature of the comet is. It was pleasure to make the interesting and funny exercise about comets with younger students. In this exercise the main character was our comet and we used information that we found for this project and showed photos that we have made. The most interesting part on this project was when we were both astronomers and assistants of our astronomy teacher during the educational process of the younger students.
We think that the work on this project gave us new knowledge and skills that will help us in our realization as astronomers.

9. Bibliography:

For contacts:
Nadezhda Lyubomirova Radeva, e-mail:,
Hristo Stoev Stoev, e-mail:
The students are from the Astronomical courses made by the Astronomical Observatory and Planetarium "N.Copernicus"-Varna

Leader: Veselka Siderova Radeva, e-mail:
Astronomical observatory,Varna, Bulgaria