Tag: comets

Comet NEOWISE (C/2020 F3)

Finally, a bright comet! Comet C/2020 F3 NEOWISE was discovered on March 27, 2020 by the NEOWISE space telescope. NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer) is the current extended “warm” mission of WISE after its hydrogen coolant became depleted.

Currently visible in the morning twilight sky, Comet NEOWISE is already a naked-eye object and is spectacular in binoculars, low in the NE, below and a little to the left of the bright star Capella. Soon it will be moving into the evening sky, though it is expected to diminish in brightness somewhat as it gets further from the Sun. Here’s an ephemeris for Comet NEOWISE for July and August showing when it will be at least 10˚ above the horizon in a sky that is not brightened by either twilight or moonlight. Avoiding light pollution, however, is up to you. Enjoy!

Comet naming these days is a mess! For one, some of the acronyms used for the automated surveys that discover them are unattractive. Thank heavens neither of the two comets named ASASSN (C/2017 O1 and C/2018 N2) ever became as bright as our current comet!

There were three comets NEOWISE in 2014, three in 2015, three in 2016, one in 2017, two in 2018, two in 2019, and one (so far) in 2020.

Comet NEOWISE

C/2014 C3
P/2014 L2
C/2014 N3
P/2015 J3
C/2015 X8
C/2015 YG1
C/2016 B1
C/2016 C2
C/2016 U1
C/2017 C1
C/2018 EN4
C/2018 N1
C/2019 H1
C/2019 L2
C/2020 F3

Might I suggest that we give this year’s first NEOWISE comet the following name?

Comet NEOWISE 15 (C/2020 F3)

Comet-NEOWISE-2020-F3-202007Download
Comet NEOWISE (C/2020 F3) 19 July 2020 3:21:59 UT 30s 55 mm f/4 ISO 1600 Canon EOS 100D
Photo by David Oesper
Comet NEOWISE (C/2020 F3) 20 July 2020 3:38:57 UT 3m 55 mm f/4.5 ISO 1600 Canon EOS 100D
Photo by David Oesper
Comet NEOWISE (C/2020 F3) 23 July 2020 3:22:17 UT 2m 55 mm f/4 ISO 1600 Canon EOS 100D
Photo by David Oesper

Comet ATLAS (C/2019 Y4)

Comet C/2019 Y4 ATLAS was discovered on December 28, 2019 and is named after the observational program that discovered it: Asteroid Terrestrial-impact Last Alert System (ATLAS). It could become a naked-eye comet—if it doesn’t disintegrate as it gets closer to the Sun. Here’s an ephemeris for the remainder of April and May.

Comet-ATLAS-2019-Y4-202004Download
Comet ATLAS (C/2019 Y4) 10 Apr 2020 0224 UT 4 minute exposure 300mm f/5.6 Dodgeville WI

Cometary Tails

A comet’s ion/plasma/gas tail points directly away from the Sun. A comet’s dust tail deviates somewhat (and sometimes a lot) from this, falling behind the comet along its orbital path around the Sun.

For the best view of either tail, our line of sight should be perpendicular to the length of the tail. However, that seldom happens, and we are viewing the tails with some degree of foreshortening. The orientation of the gas tail is called the phase angle, and it is the Sun – comet – observer angle.

A phase angle of 0° indicates we are looking straight down the tail of the comet (maximum foreshortening) with the head being oriented closest to the observer.

A phase angle of 90° indicates that our line-of-sight to the comet is perpendicular to the Sun-comet line, so we are viewing the comet’s gas tail with no foreshortening.

A phase angle of 180° indicates that we are again looking straight down the gas tail of the comet (again, maximum foreshortening) only this time the tail is closer to the observer and the head further away. Of course, the only time this orientation could happen is when the comet is transiting the Sun, thus rendering it essentially unobservable.

Phase angles of 0 to 90° mean that the comet head is closer to the observer than the tail; angles of 90 – 180° mean that the comet’s tail is closer to the observer than the head.

Here’s a table showing the phase angle, and some other information, for currently-observable comets brighter than 15th magnitude as seen from Earth. The column labeled Elongation indicates the Sun – observer – comet angle. In other words, the angular separation between the Sun and the comet.

A comet that is farther from the Sun than the observer can never have a phase angle as great as 90°, but a comet that is closer to the Sun than the observer can. Looking at the diagram above and considering a comet in a circular orbit around the Sun (highly unlikely, I know, but bear with me) and closer to the Sun than the observer, the phase angle would be 90° when the comet is at greatest elongation.

Incidentally, comet designations that have a number followed by the letter “P” (such as 29P, 68P, and 260P) are periodic comets (more precisely described as short-period comets), defined to be comets with orbital periods of less than 200 years or that have been observed at more than one perihelion passage.

Comet Orbital Elements

The orbit of a comet can be defined with six numbers, called the orbital elements, and by entering these numbers into your favorite planetarium software, you can view the location of the comet at any given time reasonably near the epoch date. The epoch date is a particular date for which the orbital elements are calculated and therefore the most accurate around that time.

Different sets of six parameters can be used, but the most common are shown below. Example values are given for Comet Holmes (17P), which exhibited a remarkable outburst in October 2007, now almost 12 years ago.

Perihelion distance, q

This is the center-to-center distance from the comet to the Sun when the comet is at perihelion, its closest point to the Sun. For Comet Holmes, this is 2.05338 AU, well beyond the orbits of both the Earth and Mars.

Orbital eccentricity, e

This is a unitless number that is the measure of the amount of ellipticity an orbit has. For a circular orbit, e = 0. A parabolic orbit, e = 1. A hyperbolic orbit, e > 1. Many comets have highly elliptical orbits, often with e > 0.9. Short-period comets, such as Comet Holmes (17P), have more modest eccentricities. Comet Holmes has an orbital eccentricity of 0.432876. This means that at perihelion, Comet Holmes is 43.3% closer to the Sun than its midpoint distance, and at aphelion Comet Holmes is 43.3% further away from the Sun than its midpoint distance.

Date of perihelion, T

This is a date (converted to decimal Julian date) that the comet reached perihelion, or will next reach perihelion. For example, Comet Holmes reached perihelion on 2007 May 5.0284.

Inclination to the Ecliptic Plane, i

This is the angle made by the intersection of the plane of the comet’s orbit with the ecliptic, the plane of the Earth’s orbit. Comet Holmes has an inclination angle of 19.1143°.

Longitude of the ascending node, Ω

The intersection between the comet’s orbital plane and the Earth’s orbital plane forms a line, called the line of nodes. The places where this line intersects the comet’s orbit forms two points. One point defines the location where the comet crosses the ecliptic plane heading from south to north. This is called the ascending node. The other point defines the location where the comet crosses the ecliptic plane heading from north to south. This is called the descending node. 0° longitude is arbitrarily defined to be the direction of the vernal equinox, the point in the sky where the Sun in its apparent path relative to the background stars crosses the celestial equator heading north. The longitude of the ascending node (capital Omega, Ω) is the angle, measured eastward (in the direction of the Earth’s orbital motion) from the vernal equinox to the ascending node of the comet’s orbit. For Comet Holmes, that angle is 326.8532°.

Argument of perihelion, ω

The angle along the comet’s orbit in the direction of the comet’s motion between its perihelion point and its ascending node (relative to the ecliptic plane) is called the argument of perihelion (small omega, ω). For Comet Holmes, this angle is 24.352°.

If all the mass of the Sun and the comet were concentrated at a geometric point, and if they were the only two objects in the universe, these six orbital elements would be fixed for all time. But these two objects have physical size, and are affected by the gravitational pull of other objects in our solar system and beyond. Moreover, nongravitational forces can act on the comet’s nucleus, such as jets of material spewing out into space, exerting a tiny but non-negligible thrust on the comet, thus altering its orbit. Because of these effects, in practice it is a good idea to define a set of osculating orbital elements which will give the best positions for the comet around a particular date. These osculating orbital elements change gradually with time (due to gravitational perturbations and non-gravitational forces acting on the comet) and give the best approximation to the orbit at a given point in time. The further one strays from the epoch date for the osculating elements, the less accurate the predicted position of the comet will be.

For example, the IAU Minor Planet Center gives a set of orbital elements for Comet Holmes that has a more recent epoch date than the one given by the JPL Small-Body Database Browser. The MPC gives an epoch date of 2015 Jun 27.0, reasonably near the date of the most recent perihelion passage of this P = 6.89y comet (2014 Mar 27.5736). JPL, on the other hand, provides a default epoch date of 2010 Jan 17.0, nearer the date of the 2007 May 5.0284 perihelion and the spectacular October 2007 apparition. For the most accurate current position of Comet Holmes in your planetarium software, you’ll probably want to use the MPC orbital elements, since they are for an epoch nearest to the date when you’ll be making your observations.

Name That Comet

As of this writing, there are 3,635 comets named SOHO, over 300 comets named LINEAR, some 179 comets named PANSTARRS, 82 comets named McNaught, 62 comets named NEAT, and so on.

Except for the comets discovered by Scottish-Australian astronomer Robert H. McNaught (1956-), all of the above comets were named after various semi-automated surveys.

SOHO = Solar and Heliospheric Observatory (spacecraft)

LINEAR = Lincoln Near-Earth Asteroid Research

Pan-STARRS = Panoramic Survey Telescope and Rapid Response System

NEAT = Near-Earth Asteroid Tracking

How do we distinguish between comets having the same name?  Each has a separate comet designation.  The first Comet LINEAR has a designation of P/1997 A2, and the most recent Comet LINEAR has a designation of C/2017 B3.

A comet designation starts with one of the following prefixes:

P/ – a periodic comet (orbital period < 200 years or confirmed observations at more than one perihelion passage)

C/ – non-periodic comet (orbital period ≥ 200 years and confirmed observations at only one perihelion passage)

X/ – comet for which no reliable orbit could be calculated (generally, historical comets)

D/ – a periodic comet that has disappeared, broken up, or been lost

A/ – an object that was mistakenly identified as a comet, but is actually a minor planet (asteroid, trans-Neptunian object, etc.)

I/ – an interstellar object that did not originate in our solar system

This is then followed by the year of discovery, a letter indicating the half-month of discovery, followed by the numeric order of discovery during the half-month.

So, we can see that the first Comet LINEAR, P/1997 A2, is a periodic comet discovered in 1997, between January 1 and January 15 of that year, and it was the second comet to be discovered during that period of time.  After the second perihelion passage, P/1997 A2 (LINEAR) was subsequently given the periodic comet number prefix of 230, so the full designation for this comet is now 230P/1997 A2 (LINEAR).

Likewise, the most recent Comet LINEAR (at the time of this writing), C/2017 B3, is a non-periodic comet discovered in 2017 between January 16 and January 31, the third comet discovered during that period of time.

Interestingly, if different periodic comets have the same name, they are sequentially numbered.  Perhaps the most famous example is Comet Shoemaker-Levy 9 that broke up and crashed into Jupiter during July 1994.  There are a total of nine periodic comets named Shoemaker-Levy.  They are:

192P/1990 V1   Shoemaker-Levy 1
137P/1990 UL3  Shoemaker-Levy 2
129P/1991 C1   Shoemaker-Levy 3
118P/1991 C2   Shoemaker-Levy 4
145P/1991 T1   Shoemaker-Levy 5
181P/1991 V1   Shoemaker-Levy 6
138P/1991 V2   Shoemaker-Levy 7
135P/1992 G2   Shoemaker-Levy 8
D/1993 F2      Shoemaker-Levy 9

However, four additional non-periodic comets were discovered by the Carolyn & Gene Shoemaker and David Levy team.  They have not received a numeric suffix and are all called “Comet Shoemaker-Levy”:

C/1991 B1      Shoemaker-Levy
C/1991 T2      Shoemaker-Levy
C/1993 K1      Shoemaker-Levy
C/1994 E2      Shoemaker-Levy

This strikes me as a bit strange.  Why afford a numeric suffix to a comet name only when it is a periodic comet?  Why not give all comets named “Shoemaker-Levy” a numeric suffix.  Normally, we would number them all in order of discovery, but since the nine periodic comets have already received a number, we would have to number the four non-periodic comets as C/1991 B1 (Shoemaker-Levy 10), C/1991 T2 (Shoemaker-Levy 11), C/1993 K1 (Shoemaker-Levy 12), and C/1994 E2 (Shoemaker-Levy 13).

I would like to see all comets, both periodic and non-periodic, receive a numeric suffix to their names whenever there is more than one.  So, instead of Comet LINEAR we would have Comet LINEAR 1, Comet LINEAR 2, Comet LINEAR 3, and so on.

By the way, the days of amateur astronomers discovering a new comet will probably soon come to a close.  Though this is a little sad, it does tell us that the entire sky is being monitored much more closely than in the past, by a number of automated surveys.  And that is a good thing, because we will be much less likely to miss anything “new” in the sky.

None One of the comets this year (so far) have has been discovered by amateurs.

UPDATE – November 20, 2018: California amateur astronomer and prolific comet hunter Don Machholz, along with Japanese amateur astronomers Shigehisa Fujikawa and Masayuki Iwamoto, independently discovered a new comet on November 7.  The new long-period comet has been named C/2018 V1 (Machholz-Fujikawa-Iwamoto).  Remarkable!

Here is the current tally of comet discoveries (or recoveries) this year:

Pan-STARRS (Panoramic Survey Telescope and Rapid Response System)
C/2018 A1 (PANSTARRS)
364P/2018 A2 (PANSTARRS)
C/2018 A4 (PANSTARRS)
P/2018 A5 (PANSTARRS)
C/2018 F4 (PANSTARRS)
P/2018 H2 (PANSTARRS)
P/2018 L1 (PANSTARRS)
P/2018 L4 (PANSTARRS)
P/2018 P3 (PANSTARRS)
P/2018 P4 (PANSTARRS)
C/2018 P5 (PANSTARRS)
372P/2018 P6 (McNaught) [recovery of P/2008 O2]

ATLAS (Asteroid Terrestrial-impact Last Alert System)
C/2018 A3 (ATLAS)
C/2018 E1 (ATLAS)
C/2018 K1 (Weiland) [H. Weiland, ATLAS]
C/2018 L2 (ATLAS)
C/2018 O1 (ATLAS)

MLS (Mt. Lemmon Survey)
C/2018 A6 (Gibbs) [A.R. Gibbs, MLS]
C/2018 B1 (Lemmon)
P/2018 C1 (Lemmon-Read) [M.T. Read, Spacewatch, Kitt Peak]
C/2018 C2 (Lemmon)
C/2018 EF9 (Lemmon)  [originally classified as an asteroid]
C/2018 F1 (Grauer) [A.D. Grauer, MLS]
C/2018 F3 (Johnson) [J.A. Johnson, MLS]
C/2018 KJ3 (Lemmon) [originally classified as an asteroid]
P/2018 L5 (Leonard) [G. Leonard, MLS]
C/2018 R3 (Lemmon)
C/2018 R5 (Lemmon)

SONEAR (Southern Observatory for Near Earth Asteroid Research)
C/2018 E2 (Barros) [Joao Barros, SONEAR]

NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer)
C/2018 EN4 (NEOWISE)  [originally classified as a Centaur asteroid]
C/2018 N1 (NEOWISE)

Spacewatch
366P/2018 F2 (Spacewatch)

CSS (Catalina Sky Survey)
367P/2018 H1 (Catalina)
C/2018 M1 (Catalina)
C/2018 R4 (Fuls) [D.C. Fuls, CSS]

NEAT (Near-Earth Asteroid Tracking)
368P/2018 L3 (NEAT)
370P/2018 P2 (NEAT)

ASAS-SN (All Sky Automated Survey for SuperNovae)
C/2018 N2 (ASASSN)

OGS (ESA Optical Ground Station)
369P/2018 P1 (Hill) [recovery of P/2010 A1]
371P/2018 R1 (LINEAR-Skiff) [recovery of P/2001 R6]

373P/2018 R2 (Rinner)  [Jean-Francois Soulier, Maisoncelles, and Krisztian Sarneczky, University of Szeged, Piszkesteto Station (Konkoly), independently recovered P/2011 W2]

374P/2018 S1 (Larson) [Krisztian Sarneczky and Robert Szakats, University of Szeged, Piszkesteto Station (Konkoly), recovered P/2007 V1]

375P/2018 T1 (Hill) [Krisztian Sarneczky, University of Szeged, Piszkesteto Station (Konkoly), recovered P/2006 D1]

Eclipse Comets

A total solar eclipse, such as that which will be crossing America on 21 Aug 2017, would present a great opportunity to discover a bright comet near the Sun.  Has that ever happened?  The answer is yes.

A comet, perhaps magnitude -4 or brighter, was spotted about 1.4° SW of the Sun during the total solar eclipse of 1 Nov 1948.  The editors of Sky & Telescope write in the January 1949 issue, “British Astronomical Association Circular No. 303, dated November 10, 1948, under the title, ‘The Eclipse Comet, 1948 I,’ reads in part:

There can be little doubt that the bright comet now reported seen in the southern morning sky is identical with the one seen during the eclipse of November 1.  The Times of November 2 in the report of the eclipse from its correspondent at Nairobi stated that a bright comet, with a long tail, was seen both by the crew of an R.A.F. aircraft and by observers on the ground.  The head, it was stated by one amateur astronomer, was still visible a few seconds after the Sun began to emerge.

A cable received by Dr. R. d’E. Atkinson, leading the Royal Observatory expedition, reports photographic confirmation of it, saying it was 93′ from the centre of the Sun in position angle 226°, and was very bright, with a tail.

“Harvard Announcement Card 956, dated November 22nd, reads in part:

Dr. Leland E. Cunningham, Students’ Observatory, University of California, Berkeley, writes: ‘New elements have been determined for the bright comet . . . .  These place the comet in position angle 228° and 104′ distant from the sun at the time of the total solar eclipse on November 1, which are in moderate agreement with Atkinson’s observed values of 226° and 93′, respectively.’

“Thus, although Comet 1948 I was missed by northern observers before it passed perihelion late in October, when its tail must have extended into the evening sky after sunset, the total eclipse of the sun provided a favorable opportunity to observe the comet practically a week before southern observers viewed it in their morning sky.  It well can be called the ‘eclipse comet’ of 1948.”

The editors of Sky & Telescope write in the March 1949 issue, “From The Observatory of December, 1948, we quote part of the proceedings of the meeting of the Royal Astronomical Society held on November 12th, at which Dr. R. d.’E Atkinson told something of his recent eclipse expedition to East Africa, and the discovery of the comet during the eclipse.  Dr. Atkinson said:

I propose to speak mainly about the comet which was observed during the eclipse; as far as our own eclipse observations are concerned, I believe they were successful, but the films have not yet been developed.

The comet, though very bright, was not visible at Mombasa, where we were (98% totality), but several newspaper reports from further north referred to it; they did not sound very convincing.  A photograph was published, but as printed it did not actually show the comet; the accompanying description was also based on an error, as I later learnt.  On the journey to Nairobi, sixty hours after the eclipse, I spoke to an eyewitness, whose account disagreed with that in the paper.  It was not until I had seen the photographs taken by the R.A.F. at Nairobi, and had found that they agreed with eye-witness reports at both places, that I realised it must have been a comet; I then made a very rough measurement of its place on the R.A.F. film, and telegraphed Dr. Merton.  As a result of my interest in these photographs, which were taken at 13,000 feet just within and just outside the shadow, the Air Commodore very kindly let me bring the films home for thorough examination.  [On one picture] very much enlarged from a hand-camera snapshot also taken by a member of the crew . . . the tail is clearly visible; visual observers all agreed that it extended downwards until it reached either clouds or the horizon, and it must have been twenty degrees long at least.  The visible part of it does not point away from the Sun at all; any portion which does this must have been extremely foreshortened.  [On another picture] the scale is larger and the definition much better, but the tail is too much underexposed to show except with a magnifying glass.  Viewed in this way, and accepting the idea that the root of the tail will point away from the Sun, one can see enough indications of curvature to make it seem that it is convex to the west; I therefore concluded in my cable a guess that the motion would be westwards, and this has proved correct.  The comet must certainly have been very bright; these pictures were taken with an aperture of f/5.6 and an exposure of 1/300 second; moreover, the head was visible for some 5-10 seconds after the end of totality.  It must certainly have been brighter than Venus.  I have now measured up three separate negatives, and they agree closely in giving a distance from the centre of the Sun of 105.4 minutes, and a position angle of 230°; however, there is some possibility of systematic error, and I have written to the Air Commodore to ask for further details.  If systematic errors can be eliminated, the place should, I think, be useful for orbit determination; it is a week earlier than any other place.”

Thus writes British astronomer Robert d’Escourt Atkinson (1898-1982) about comet C/1948 V1, the “Eclipse Comet of 1948” seen at Nairobi and Mombasa, Kenya on 1 Nov 1948.  It was next observed in the morning sky on 8 Nov 1948, and continued to be followed until 3 Apr 1949.

According to Edward S. Holden (1846-1914), John Martin Schaeberle (1853-1924) discovered a comet-like object on photographic plates taken during the 16 Apr 1893 total solar eclipse, but it has since been determined (Cliver 1989) that this was a coronal mass ejection (CME).

German-born British physicist Arthur Schuster (1851-1934) recorded a comet on photographic plates of the total solar eclipse of 17 May 1882 in Egypt.  The comet moved noticeably during the 1m50s of totality.  It is thought that this comet was a member of the Kreutz sungrazer group of comets.  It has received the designation of X/1882 K1.  The “X/” indicates that there were not enough observations of this comet to determine an orbit.  In fact, the only observations of this comet were during the total solar eclipse.  The comet is sometime called Comet Tewfik—named after the ruler of Egypt at that time in recognition of his hospitality towards the eclipse party.

A comet was discovered during the eclipse of 19 Jul 418 at Constantinople (Istanbul, Turkey) and was observed for four months afterwards.

Seneca the Younger (c. 4 BC – AD 65) writes in his Naturales quaestiones (Natural Questions):

Posidonius, in fact, tells us that during an eclipse of the Sun a comet once appeared which the sun’s proximity had hitherto concealed.

Did Posidonius (c. 135 BC – 51 BC) see this comet, or was he referring to an even earlier observation made by someone else?  With so much of the knowledge of the ancient world lost or destroyed by barbarians and zealots, we may never know.

References
Clarke, J. 1910, Physical science in the time of Nero; being a translation of    the Quaestiones naturales of Seneca
Cliver, E. W. 1989, Solar Physics, 122:2, 319-333
Federer, C. A. Jr., Sky & Telescope, January 1949, pp. 59-60
Federer, C. A. Jr., Sky & Telescope, March 1949, p. 110, 113
Hetherington, B. 1996, A Chronicle of Pre-Telescopic Astronomy
Kronk, G. W., Cometography, X/1882 K1 (Eclipse Comet or “Tewfik”)
Poitevin, P., Eclipse Comets
Seneca c. 65 AD, Naturales quaestiones, 7.20.4
Vaquero, J. M. 2014, Physics Today, 67:5, 9

Voyager 4.5 by Carina Software

My all-time favorite planetarium software program is Voyager 4.5 from Carina Software.  Hardly a day goes by when I am not using it, and my use of Voyager goes all the way back to 1993.  The current version for Mac OS X (and Windows) is 4.5.7.  Sadly, the last update was in 2010.  I wish there was something we could do to ensure that Voyager will be maintained and enhanced in the future.

Speaking of maintenance, in 2015 Voyager ceased being able to import comet and asteroid orbital elements through its automatic Updates process.  This happened because the URL changed for both.  Seems like a pretty easy fix to me.  If Carina won’t fix it, then maybe someone can edit the executable and change the two URLs?

Fortunately, you can still manually import these orbital elements by following these instructions.

Adding Comets
  1. Navigate your web browser to https://www.minorplanetcenter.net/iau/Ephemerides/Comets/Soft00Cmt.txt and save this page to a file, which will automatically be called Soft00cmt.txt.  You can save it anywhere, but I’d suggest you save it in the Import Files folder in the Voyager 4.5 main directory within your Applications folder.
  2. In Voyager, go to File : Import : Comet Orbit File…
  3. Navigate to Applications : Voyager 4.5 : Import Files : Soft00Cmt.txt and click Open.  You will get a message box asking “Before importing new data, do you want to delete all current asteroid/comet/satellite data?”  Click Yes.  Next you will see an Import results box showing you the number of comets added to Voyager’s database.  Click OK.
Adding Asteroids
  1. Navigate your web browser to https://www.minorplanetcenter.net/iau/MPCORB.html and under Available Files right click on MPCORB.DAT (uncompressed) and Save Link As… to your Voyager 4.5 Import Files folder.  Do not open this file in your web browser as it is over 147 Mb in size!  The file saved is called MPCORB.DAT.
  2. Navigate to Applications : Voyager 4.5 : Import Files : MPCORB.DAT and edit the MPCORB.DAT file with the editor of your choice.  Remove the header lines at the top of the file right down through the line of dashes, and save the file.
  3. In Voyager, go to File : Import : Asteroid Orbit File…
  4. Navigate to Applications : Voyager 4.5 : Import Files : MPCORB.DAT and click Open.  You will get a message box asking “Before importing new data, do you want to delete all current asteroid/comet/satellite data?”  Click Yes.  It will take a while to import all the asteroids, and then you will see an Import results box showing you the number of asteroids (and transNeptunian objects, by the way) added to Voyager’s database.  Click OK.