Comet C/2019 Q4 (Borisov) is a (very likely) interstellar object passing through the Solar System. Based on its high velocity and trajectory, there is very high confidence that it is a visitor from outside the Solar system. The object was discovered on Aug. 30, 2019, by amateur astronomer Gennady Borisov in Nauchnij, Crimea using a telescope he built himself. It will be the second such object detected by humankind. The first one was the cigar-shaped interstellar object 'Oumuamua that swung by in October 2017.
skralyx yesterday published a diary on the subject with an excellent summary and some lively discussion; in this diary, we provide some technical details about C/2019 Q4 and some additional background information, including comparisons with ‘Oumuamua.
C/2019 Q4 (Borisov)
After the initial detection of the comet, NASA JPL, the Minor Planet Center and the European Space Agency made additional observations and indicated that there is high confidence that C/2019 Q4 is of interstellar origin. Astronomers in Poland and the Netherlands have come to similar conclusions.
There is still no “official” designation of C/2019 Q4 as an interstellar object; agencies are waiting for some more observations and data to rule out the faint possibility of a Solar System origin. The comet's estimated velocity of 150,000 km/h, which is well above the typical velocities of objects orbiting the Sun at that distance, strongly indicates that C/2019 Q4 is of interstellar origin. Its approach angle is almost perpendicular to the ecliptic plane, hence there is no chance that it has encountered and has been affected by any Solar System planet on its journey.
The Minor Planet Center has issued its Electronic Circular (MPEC) for C/2019 Q4. It has not been given interstellar status yet.
A new MPEC was issued Friday morning — still no interstellar designation.
Here is an image of the comet taken using the 8.2 m Gemini North telescope at Maunakea on Sep 10 by astronomers in Poland and the Netherlands. The coma and tail are clearly visible in this image. The findings of this observation are summarized in a paper, in which the authors state that “Residual analysis together with the large hyperbolic excess velocity assure that 2I/Borisov is of extrasolar origin.”
Discovery Info.
|
C/2019 Q4 Borisov |
‘Oumuamua |
Discoverer |
Gennady Borisov |
Robert Weryk |
Discovery Telescope |
Custom-built 0.65-meter telescope |
Pan-STARRS |
Discovery location |
Mobil Astronomical Robotics Genon Observatory (MARGO), Nauchnij, Crimea |
Haleakala Observatory, Hawaii |
Discovery date |
30 August 2019, more than 3 months before perihelion |
19 October 2017, 40 days after perihelion |
Trajectory
|
C/2019 Q4 Borisov |
‘Oumuamua |
Origin direction |
Constellation Cassiopeia |
Constellation Lira |
Destination direction |
Constellation Telescopium |
Constellation Pegasus |
Heliocentric orbital eccentricity |
3.2
(> 1 implies interstellar)
|
1.2 |
Speed during approach |
41 km/s (147,000 km/h) |
26.33 km/s (94,788 km/h)
|
Closest approach to the Sun (perihelion) |
2.0 AU
Outside Mars’ orbit
|
0.255 AU
Inside Mercury’s orbit
|
Date of closest approach to the Sun |
Dec 7-8, 2019 |
Sep 9, 2017 |
Closest approach to Earth |
~2 AU (quite far away) |
0.1616 AU |
Date of closest approach to Earth |
Dec 29, 2019 |
Oct 14, 2017 |
Current distance |
2.76 AU from Sun; 3.42 AU from Earth |
|
Note that many of the parameter values for C/2019 Q4 Borisov will get revised in the coming weeks.
1 AU = 150 million km = mean Earth-Sun distance
Physical Parameters
|
C/2019 Q4 Borisov |
‘Oumuamua |
Official Name |
C/2019 Q4 Borisov
Will change to 2I/Borisov
|
1I/2017 U1
The I stands for Interstellar
|
Size |
2-16 km across |
Length — between 100 and 1,000 m
Width and thickness — between 35 and 167 m
|
Rotation Period |
? |
7 — 8 hours |
Cometary outgassing |
Very prominent |
Not perceptible |
Oddities |
We will find out! |
Accelerated a bit on departure
Attributed to minor outgassing
|
Trajectory Description
C/2019 Q4 is approaching the Solar System ecliptic plane from the north, at about a 40 degree angle, will cross the ecliptic outside the orbit of Mars around and exit south of the ecliptic, putting on a show around Christmas time. It appears that the trajectory will bend a bit because of the Sun’s gravity.
Currently, C/2019 Q4 is located on the other side of the Sun relative to Earth, observations are done during dawn/dusk hours at low elevation angles, but observation conditions will improve in the next few months. Due to its high distance from earth, it will not be visible to the naked eye.
‘Oumuamua also approached from the North but came much closer to the Sun, inside the orbit of Mercury, looped around the Sun and exited back out the north side.
More Observations and Analysis
Observations made at the Gran Telescopio Canarias (GTC) located on the island of La Palma, in the Canaries, Spain, using its 10.4 m telescope, reveal that C/2019 Q4 has a surface composition not unlike that found in Solar System comets. Astronomers point out that the results of the research "clearly show that comets in other planetary systems can be similar to those of the Solar System and they may have formed by processes similar to those which led to the formation of the Oort Cloud comets in the Solar System."
The surface composition of ‘Oumuamua was also determined to be similar to D-type comets and asteroids (organic-rich, red surface color, found in the Solar System).
Detection of C/2019 Q4 Borisov
Why did it take an amateur astronomer to discover this comet? Why not the various large observatories that look for asteroids and comets?
C/2019 Q4 Borisov is 3.75 AU (562 million km) away and has an estimated size of 10 km across. That would be 0.000001 degrees wide as seen from Earth. Even the Pan-STARRS telescope with a relatively wide view of 3 degrees and a 1.4 billion pixel CCD (37,416 x 37,416) will not be able to resolve this comet; each pixel covers approx. 0.00008 degrees of the view. Also, Pan-STARRS takes a week to scan the whole sky, taking approximately 1 minute per image, during dark nights. One needs a telescope with a much smaller field of view, serendipitously aimed at just the right spot to catch a comet like this. Now that we know where it is, many professional and amateur telescopes will be focused on it for months to come.
The Gemini North telescope (which was used for the image shown earlier in this article) is used for imaging exoplanets thousands of light years away and is capable of capturing images with field widths as narrow as 0.0016 degrees.
’Oumuamua was not detected until 40 days after perihelion. We have a head start of this one (thanks Borisov) and months of observation ahead of an object much larger than ’Oumuamua although it will remain more distant from Earth than ’Oumuamua.
Gennadi Borisov
Gennady Borisov, is an amateur astronomer who works as an engineer at the Sternberg Astronomical Institute. He designs his own telescopes and has discovered seven comets and several NEOs (Near Earth Objects).
C/2019 Q4 (Borisov) was discovered using the Borisov-designed telescope shown below. Amazing work!
The Origin of C/2019 Q4
It’s quite likely that this object may have been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our Solar System. And it will probably never visit us again. It has been speculated that this object was created in the early stages of planet formation around another star. It is estimated that 99% of the material around the Sun when it formed got thrown out into interstellar space, and much of it is probably still roaming the galaxy. Astronomers are also quite certain that it came from our galaxy, not another galaxy.
The authors of the paper on ‘Oumuamua (A/2017 U1) stated that -
A/2017 U1 has likely orbited the galaxy multiple times and its system of origin could today be on the other side of the galaxy. This also suggests that the solar perihelion of A/2017 U1 was its first close encounter with a star and the first opportunity to warm any volatiles.
So what might C/2019 Q4 look like, if we could see it up close?
Here is a short film created using images from the Rosetta spacecraft's mission that shows the rugged beauty of the odd-shaped 4.3 x 4.1 km comet 67P/Churyumov-Gerasimenko.
So, how many such ISOs are out there?
Astronomers estimate that an interstellar object (ISO) similar to ‘Oumuamua and C/2019 Q4 passes through the inner Solar System (< 1 AU, AU = Earth-Sun distance) about once per year, but they are too faint to be easily detected. Comets with their long vapor tails are obviously much easier to spot. It is only recently that survey telescopes, such as Pan-STARRS, have become powerful enough to detect and study them.
Another independent paper, which uses data gathered using the NOT and WIYN Telescopes, estimates that, at any one time, there are ∼10,000 ‘Oumuamua-like objects closer to the Sun than Neptune (30 AU). Each takes ∼10 years to cross the planetary region before returning to interstellar space.
What if such an Object Collided with Earth?
The size and speed of C/2019 Q4 implies that a direct collision with Earth would be catastrophic, much more devastating than the (similar size) 10 km asteroid that hit Earth about 65 million years ago and wiped out the dinosaurs. That asteroid was traveling at about 71,424 km/h while C/2019 Q4 is traveling at more than twice that speed at 147,600 km/h.
There are plenty of of Solar System asteroids whose paths cross that of Earth. That is why NASA and other agencies around the world have been observing and cataloging asteroids for years now, using ground and space based telescopes and radar, and are experimenting with technologies to defend Earth against such an object should one happen to be on a direct collision course with Earth. Of course, interstellar asteroids are difficult to detect and catalog and we just have to keep our planetary fingers crossed.
Here is a clip from the 1998 film, which featured a failed attempt to deflect a comet headed for Earth -
Planetary Defense Against Asteroids
A variety of techniques have been proposed for dealing with marauding asteroids. A few experimental missions have been conducted and others are in the pipeline. See earlier diary Asteroids and Planetary Defense for more info on these missions.
Here are 2 recent examples-
Unfortunately, NASA’s budget is getting squeezed, while its projects grow in number and complexity. One of the asteroid defense projects — the Asteroid Redirect Mission (ARM) — was canceled in 2017. The mission included grabbing a boulder off the comet, using the gravity tractor technique to deflect the asteroid and transporting the boulder back to a lunar orbit. The House Appropriations Committee explained that decision by saying “The Committee believes that neither a robotic nor a crewed mission to an asteroid appreciably contribute to the overarching mission to Mars.”
Mars over civilization-destroying asteroids? Don’t look to republicans for logic, they just look for opportunities to line their pockets.
Remarks
It’s going to be a very interesting next few months, as researchers get an extended opportunity to study and analyze C/2019 Q4. It will certainly spike the imagination of the general public and questions will pop up — what is it really? Just a comet or something seen in science-fiction novels and movies? What is it’s purpose, if any? Are we alone?
It does remind us of the spacecraft in Rendezvous with Rama by Arthur C. Clarke -
… and the whale probe from the Star Trek IV film -
References
- Submitted paper — arxiv.org/…
- FAQ for gb00234 = C/2019 Q4 (Borisov) — projectpluto.com/…
- C/2019 Q4 (Borisov) wiki — en.wikipedia.org/…
- Astronomy Forum — astronomy.ru/…
- Minor Planet Electronic Circular (MPEC) for C/1029 Q4 (Borisov) - www.minorplanetcenter.net/…
- NASA announcement — www.nasa.gov/…
- ssd.jpl.nasa.gov/...
- ‘Oumuamua — en.wikipedia.org/…
- Solar System’s First Interstellar Visitor is Shaped like a Cigar! — www.dailykos.com/…
- Asteroids and Planetary Defense — www.dailykos.com/…