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Could We Send a Probe to C/2019 Q4 (Borisov)?

The arrival of an apparent interstellar visitor, the comet now designated C/2019 Q4 (Borisov), invariably calls to mind the all too swift passage of ‘Oumuamua through our skies in 2017. Detected 40 days after perihelion, the object was headed out of the Solar system when discovered, making observation time limited and the prospects of visiting it with a probe problematic. Nonetheless, Andreas Hein and colleagues at the Initiative for Interstellar Studies put out a mission concept we reviewed in these pages. To refresh your memory, see Project Lyra: Sending a Spacecraft to 1I/’Oumuamua (formerly A/2017 U1), the Interstellar Asteroid).

Image: C/2019 Q4 (Borisov), in the center of the image. Note what appears to be a short tail extending from the coma. Credit: Gennady Borisov.

The mission the authors described stretched the boundaries of the technologically possible, not to mention the resources that would be available for such an attempt. But now we have a second interstellar wanderer, one detected well before perihelion. In a new paper assembled in what must be record time, Hein and two i4IS colleagues, Adam Hibberd and Nikolaos Perakis tackle the challenge of reaching the comet, noting several options with varying launch dates.

This is interesting stuff, because as the paper notes, the fact that we have found both ‘Oumuamua and C/2019 Q4 (Borisov) so close together, plus the fact that better observing technologies are coming online to find such objects, indicates that the population of interstellar materials coming into the Solar system is high enough to generate new discoveries, and in the not so distant future at that. If any kind of mission concept can be developed that is remotely feasible for both interstellar visitors, we should soon find more we can reach with a probe.

Adam Hibberd’s role in the new paper was to develop the needed algorithms for calculating the trajectories involved. Called Optimum Interplanetary Trajectory Software (OITS), the software is used to calculate a direct transfer from Earth to C/2019 Q4 (Borisov) with flight durations of up to 10,000 days, with the necessary Delta-V (change in velocity) coming out below 100 kilometers per second, but still too high to obtain with existing chemical propulsion.

The software shows that a mission with feasible Delta-V and direct transfer from Earth would have had to have been launched in July of 2018, using a Falcon Heavy launch vehicle, with arrival at the object in October of 2019. We’re reminded again of the benefit of early detection of objects like these, capabilities that new facilities like the Large Synoptic Survey Telescope (LSST) should be able to deliver in just a few short years.

We learn, however, that other strategies can be deployed beyond chemical propulsion, and here we’re into various kinds of gravitational assists coupled with propulsive maneuvers. Key to the concept is the so-called Oberth maneuver, in which a spacecraft going deep into the gravitational well of a large object like the Sun accelerates at the point when it has reached maximum speed. Firing the engine when orbital velocity is highest gives the mission maximum kick and relies upon creating the highest thrust possible in the shortest period of time.

From the paper, describing the Oberth maneuver in the context of this mission:

For later launch dates, the DeltaV increases to levels where no existing chemical propulsion system would be able to deliver the required DeltaV. One possibility to still reach an interstellar object is to use an Oberth maneuver. For an Oberth maneuver, the spacecraft is injected into a trajectory with a [perihelion] close to the Sun, where the spacecraft applies a boost. The closer the boost is applied to the Sun, the larger the gain in DeltaV. Additional flyby maneuvers are used to bring the spacecraft on the initial heliocentric trajectory.

The authors envision using the Oberth maneuver at the Sun in combination with a Jupiter flyby, thus leveraging the deepest gravitational wells available to us in the Solar System. The proposed trajectory is shown in the figure below, drawn from the paper. Notice that the Jupiter flyby is here used to decelerate the spacecraft toward the Sun. The Oberth maneuver at the Sun then flings the spacecraft outbound for its encounter with C/2019 Q4 (Borisov).

Image: This is Figure 3 from the paper. The green line is the trajectory from the Earth to Jupiter, with the deceleration at Jupiter and subsequent trajectory toward the Sun shown as a blue line. The solid red line is the trajectory following the Oberth maneuver at perihelion. Credit: Hibberd, Perakis & Hein.

As to the mission components, the authors’ calculations show that C/2019 Q4 (Borisov) could be reached in 2045 following a launch in 2030, using the Space Launch System, the requisite heat-shield (this draws on existing work with the Parker Solar Probe), and solid-fuel propulsion engines. The payload is envisioned as a CubeSat-class spacecraft with a mass of 3 kg.

Thus we have the outline of a way of reaching our second interstellar object. It’s helpful to know how this could be done no matter how it stretches our current methods because if we do find many more such objects, some are bound to present fewer challenges than the first two, with mission concepts that may prove less demanding. It pays us to be thinking now about early detection and fast implementation of such designs as we add these interesting objects into our list of high-priority destinations. After Ultima Thule, perhaps a comet from another star?

The paper is Hibberd, Perakis & Hein, “Sending a Spacecraft to Interstellar Comet C/2019 Q4 (Borisov),” available now as a preprint.

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{ 44 comments… add one }
  • Daniel September 16, 2019, 13:24

    I’d be more curious how the future Comet Interceptor(s) that the ESA plans to deploy would do. This is exactly the kind of object that I assume they would want to target!

    A more realistic mission in the near-term might be a sample return that goes through the plume of the comet after it passes.

  • Tiens van Greuning September 16, 2019, 13:50

    What occurs to me, is that the earlier we launch a mission to one of these visitors, the less DeltaV is needed, and also that most of the mass that needs to be sent to Jupiter is the solid-fuel boosters.

    The third thought occuring to me is that sending a probe to comet Borisov seems to be a tad optimistic with current techonology and political willpower.

    But we do have the LSST coming online in a few years, and possibly we will start seeing more of these interstellar visitors earlier in their trajectory past the Sun.

    So if we are really serious about sending a proper probe (maybe something a bit larger than 3kg) to one of these objects, we should start off by doing the following:

    Firstly, book a Falcon Heavy launch for as big a commercially available solid-fuel booster as it can deliver to Jupiter orbit right away.

    Secondly, start developing a probe with a Parker-type heat shield right away.

    Thirdly, launch another identical SF booster to LEO, and find a way to dock your to-be-developed probe to this booster, and train how to do it so that your actual mission can do this without a hitch.

    Then, launch your probe to Jupiter orbit and let it do some science and flyby’s of the moons while it is there.

    And finally, when a suitable target is detected, dock your probe to the booster that should have arrived there years ago, and light her up using Jupiter to slingshot it inward to the Sun and an Oberth Maneuver to take it to your destination with hopefully a lot less energy expenditure and cost than trying to catch comet Borisov would require.

    While you’re at it, send another few SF boosters to Jupiter orbit and manufacture a few of your probes, because I suspect there will be targets aplenty to choose from as our detection abilities continue to improve.

  • Charley September 16, 2019, 16:04

    “Then, launch your probe to Jupiter orbit and let it do some science and flyby’s of the moons while it is there.

    And finally, when a suitable target is detected, dock your probe to the booster that should have arrived there years ago, and light her up using Jupiter to slingshot it inward to the Sun … ”

    Think there may be a little bit of an problem with your idea of linking up with a booster in Jupiter’s orbit to make advantage of a gravity assist. My understanding, if it is correct, is that the incoming probe from earth must be in continuous motion with respect to Jupiter to achieve the assist. Docking with a already orbiting SF in Jupiter would by virtue of it being motionless (relative to Jupiter’s orbital motion) result in the incoming booster being unnecessarily de accelerated, thus defeating the gravity assist.

    However, having a system available in advance with regards to the NEXT probe that may come in at any time would be a virtue, since there may be always be a errant interstellar interloper, which could be on a collision course with Earth. We don’t know the frequency of these objects, but we should be knowledgeable and a bit prepared in the event that they impact us. Better to be a bit safe than sorry.

    • EricSECT September 17, 2019, 5:11

      A Jupiter grazing vehicle steals a tiny bit of energy from that planet’s orbital motion around Sol. Makes Jupiter spiral in closer to the Sun an infinitesimal amount.

      And for those interested (I had to look it up): The physics behind the Oberth Maneuver is simply due to the fact that there is more kinetic energy in the fuel if the rocket is moving fast, vice moving slow ….so the rocket motor ends up being slightly more efficient (https://en.wikipedia.org/wiki/Orbital_maneuver).

    • Tiens van Greuning September 17, 2019, 7:36

      Hi Charley
      Please correct me if I’m wrong, but wouldn’t the effect of the gravity assist greater the slower your craft passes through perijove?

      As I understand it, you would, from Jupiter orbit, light up your engine once to drop into Jupiter’s gravity well, then a second time right after passing through perijove, to decelerate your craft relative to the Sun so that you can drop into the Sun’s gravity well, and then your third and largest burn right after passing through perihelium to achieve the necessary acceleration to head out toward your interstellar object.

      My suggestion was merely to get the largest part of the mass, which would be your SF booster, to Jupiter on earlier on a slower, more energy efficient trajectory, and then send the less massive probe later on to pair up with the booster.

      • Charley September 17, 2019, 10:23

        Hello, believe it or not I was thinking through your question last night and while it has some great merits, my rethinking of the thing suggest that your use of the booster in orbit about Jupiter as an agent of deceleration would result in a slower approach to the sun.

        The purpose of the Jovian gravity assist is to cancel the earth’s orbital momentum such as to allow the probe to fall into the sun. Your mated booster could possibly be allowed to fire after closest approach to Jupiter to allow you to accelerate the fall to the sun and get it there sooner which might give you some velocity increase, but the real problem comes about when you try to match the velocity of the probe coming into Jupiter to meet with the solid fuel booster already in orbit about Jupiter. I fear that the process of connecting the two crafts would result in a highly destructive velocity difference upon mating the two bodies together on the fly. That’s why I wonder if it would be ultimately to the disadvantage to follow this procedure.

        • Tiens van Greuning September 17, 2019, 13:48

          Hi Charley
          I was thinking, since you would not have a target yet when the probe got to Jupiter, (again, the earlier in the interstellar object’s approach to the Sun you launch your probe, the lower the DeltaV required to get to it, so park the probe there and wait for the next target to be detected) to put it in orbit around Jupiter and fly by some moons and do some science while it was waiting for the next interstellar object to be detected, and only then to mate it to the booster and send it on its way.

          • Charley September 17, 2019, 16:03

            Hello again, if I understand you correctly, that would be a nice option, however, sitting in orbit around Jupiter just waiting for an opportunity will not permit you to do a gravity assist. Gravity assists work only when you have a probe that is incoming into Jupiter’s gravity well. What you would end up doing is mating the booster in using it to push you out of Jupiter’s orbit, the us you wouldn’t get the required Delta V that you were seeking to get yourself to the sun.

  • Jens September 16, 2019, 17:07

    Here is a link to the ESA mission. http://www.cometinterceptor.space/ It does not state whether it will use an Oberth manouver or not, but why else would they want to place it at L2?

  • Neil Stahl September 16, 2019, 17:59

    Can anyone explain to me in clear and simple terms why there’s an advantage to flying out to Jupiter and back rather than applying all that Δv in flying toward the sun and saving months if not years in getting into pursuit.

    Thanks.

    • Ron S. September 16, 2019, 20:31

      Flying toward the sun isn’t easy because you must shed 30 km/s of orbital velocity which is orthogonal to the sun’s direction. Witness the multiple gravitational assists used to place spacecraft destined for Mercury and close solar encounters. It requires less energy to use Earth’s orbital velocity to chase down Jupiter and use it to change direction sunward. Further, you need a massive planet to achieve that tight maneuver. You could use Venus instead of Jupiter by shedding some of our orbital velocity but I’ll have to leave this to someone with greater knowledge to discuss the relative merits of the two (and other) methods.

    • Robin Datta September 16, 2019, 22:17

      I imagine it would be to get the boost of two sequential Oberth manoeuvres by the biggest masses in the vicinity: the time spent travelling to and from Jupiter would be more than compensated by the additional velocity.

    • Charley September 16, 2019, 22:22

      In the very most simplest terms possible, no booster currently in existence can provide all that Δv necessary to slow down and plummet into close to the sun. It’s necessary to go to Jupiter to lose all the extra Δv necessary to do that.

    • Antonio September 17, 2019, 2:08

      Because the Δv to fly toward the Sun is huge and to fly to Jupiter is way smaller.

      • Charley September 17, 2019, 10:25

        Yes, no chemical booster can remove the earth’s orbital momentum ( the Δv were talking about) only Jupiter can achieve that, and the Δv is less to fly to Jupiter.

  • James M Essig September 16, 2019, 18:30

    Here are some values of perhaps doable solar O’berth Maneuvers. I have lots of O’berth maneuver tables in my various published books.

    Now, the non-relativistic rocket equation is:

    Delta V = (Vexhaust)[ln (M0/M1)] where M0/M1 is the mass ratio of the rocket.

    So, let us assume a large mass ratio such as a value of 100. This value may be attainable with the large light-weight tanks being developed by NASA.

    So, assuming a start from a stationary state, the terminal velocity of the rocket would be 24.5 km/sec.

    For a mass ratio of 1,000, the result is 36.75 km/sec.

    Δv km/s: {1 + [(2Vesc)/(Δv)]} EXP (1/2): Exiting Velocity km/s
    20 : 5.567764363 : 111.3552873
    25 : 5 : 125
    30 : 4.582575695 : 137.4772708
    35 : 4.25944329 : 149.0805152
    40 : 4 : 160
    45 : 3.785938897 : 170.3672504
    TABLE 117.

    Now, if we were willing to attempt to graze the Sun, at a radial coordinate of closest approach corresponding to an escape velocity of 600 km/sec, we obtain the following performance data.

    Δv km/s: {1 + [(2Vesc)/(Δv)]} EXP (1/2): Exiting Velocity km/s
    20 : 7.810249676 : 156.2049935
    25 : 7 : 175
    30 : 6.403124237 : 192.0937271
    35 : 5.940177968 : 207.9062289
    40 : 5.567764363 : 222.7105745
    45 : 5.259911279 : 236.6960076
    TABLE 118.

  • Robin Datta September 16, 2019, 19:01

    Gravity assist ain’t gonna work if the trajectory ain’t parabolic and persistent orbits ain’t parabolic.

    Placement/positioning the hardware for “one size fits all/most” should take into consideration that one size optimally fits almost none; less advanced positioning sacrifices time for flexibility.

    Nevertheless, the prospect of broadening our knowledge beyond our backyard should give the study of these interstellar objects (and potential impactors!) a high priority.

    • James Essig September 17, 2019, 18:51

      A lot of things need to be considered before ruling out the use of Solar O’berth maneuvers for enabling fast Keplerian velocity probes that could catch up to interstellar objects.

      For one, solar sailing and tacking may set a probe on a more or less parabolic path of in-fall toward the Sun. Magnetic sails and magnetic plasma bottle sail procedures might also work.

      Another option is to simply use a huge rocket to set the probe on parabolic trajectory toward the Sun.

      Regardless, some NASA researchers seem to agree as can be seen from the paper at the following link for a two-burn maneuver.

      https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100033146.pdf

      Other forms of O’berth like maneuvers may also be possible and I have an open mind that additional maneuvers based on infalling and crazing approach to the Sun can work with ordinary mainstream chemical rocket fuels.

  • Andrew Palfreyman September 16, 2019, 19:38

    Paul, that’s definitely the right specific question to ask in regards to these objects – of which we can expect a steady supply as our detection sensitivities improve.

    Cubesats are not particularly expensive, and neither is a flock of them. Might I therefore propose launching a standby fleet, poised ready to undertake early intercept missions? The trick is the optimal covering of the state space of likely arrival trajectories by judicious placement of the probes.

  • Alexa Kindler September 16, 2019, 22:44

    Maybe we should already have a spaceship in a suitable orbit around the Sun so, when one of these interstellar visitors show up, maneuvers may already commence in space, instead of waiting to see one to then start a veritable space race from behind, from the Earth.

    • Malcolm Davis September 17, 2019, 18:51

      Yes – agree. To me, a lot of the analysis above – about detecting a comet, then building the spacecraft and then launching it on complex and time-consuming gravity assist trajectories misses the point. If we had a dedicated comet interceptor in space, perhaps propelled by something other than traditional chemical rockets, we’d have a better chance to getting a sophisticated probe (not a cubesat) to an object quicker. It seems logical to me.

  • Alex Tolley September 17, 2019, 0:01

    While not doable anytime soon, these sort of missions are crying out for “high acceleration”, high-velocity craft. Beamed [sail] propulsion would fit the bill, allowing a craft to be aimed in the right direction and accelerated to the needed velocity for an intercept. If the object is detected well before perihelion, it may even be possible to stage a rendezvous.

  • Michael Fidler September 17, 2019, 3:06

    What we may find is that the majority of these objects do not come from other solar systems but instead form in the dense clouds in the spiral arms of our galaxy.
    The plane of the solar system as it travels thru space around the galaxy is at an angle of some 63 degrees to the plane of our galaxy. Orientation of the Earth, Sun and Solar System in the Milky Way looks like this:
    https://live.staticflickr.com/65535/48747477891_b5d0076a42_b.jpg

    This is the reason we see the milky way at such a large angle in the night sky:
    https://live.staticflickr.com/65535/48747146128_31dc76b034_b.jpg

    Here is an image of ‘Oumuamua and C/2019 Q4 (Borisov) passing thru our solar system:
    https://live.staticflickr.com/65535/48747146088_fcb6bca800_b.jpg

    This is the same image rotated by 63 degrees:
    https://live.staticflickr.com/65535/48747850362_b962cfb003_b.jpg

    So it looks to me that this is not a comet that was flung violently out of a
    alien solar system but a comet that formed in space by itself and we ran into it.

    The solar system also wobbles up and down around the mid-plane of the milky way galaxy and passes thru the mid-plane about every 35 to 30 million years:
    https://live.staticflickr.com/65535/48747293548_ee2eb0b5fa_b.jpg

    The result of this is that a higher number of interstellar comets and asteroids will be encountered. Every 60 to to 70 million years the solar system will pass near or thru one of the four spiral arms of our galaxy for as long as 10 million years:
    https://live.staticflickr.com/65535/48747626606_122c9db387_b.jpg

    These areas are rich in nebula’s and star forming regions that produce a huge number of comets and asteroids, this could create huge showers of such objects as the solar system and earth passes thru them:
    https://live.staticflickr.com/65535/48747732331_cd5f1efff7_b.jpg

    The earth’s Axial precession is over 26,000 and in 13,000 years be pointing at Vega instead of Polaris. This will cause the earth’s north pole to be facing closer to the milky way and the oncoming objects directly:
    https://live.staticflickr.com/65535/48747145973_494190e886_b.jpg

    https://upload.wikimedia.org/wikipedia/commons/5/58/A_comparison_of_two_interstellar_objects_passing_through_our_solar_system.gif

    http://i.imgur.com/E9Uoc0H.gifv

    https://socialunderground.com/wp-content/uploads/2018/01/tenor.gif

    https://fsmedia.imgix.net/19/94/66/ef/b162/4ff6/a79a/3307c8a515df/dinosaur-asteroid-impact.gif

    Look north of the Sun to catch a planet killer!

    • Alex Tru. September 18, 2019, 3:38

      Your idea supposes that our Solar system is not bounded by gravity laws to our Galaxy but is free flying in the Universe…

      • Michael Fidler September 18, 2019, 8:09

        No, you missed the idea completely.

  • wdk September 17, 2019, 10:32

    It looks to me that the benefit of intercept with a spacecraft would be rendezvous.
    But if the idea is to get a closer look at the comet, then a great deal can be done with a large space telescope, assuming that the near approach and the Mars orbit perihelion does not pose viewing issues such as the sun in near the line of sight.

    The case of ‘Oumuamua is a precedent of a sort, but one of its features was that there was little time to observe it since it was near perihelion and it was most likely less luminous than this next object will be – maybe already is. But a lot of science could be done by existing space observatories – and even ground stations.

    Within the technical bounds and outside of crash programs, small satellites could be sent to the vicinity of its track – or later sent to sample its wake. But a problem which will remain is the large difference in velocity of a hyperbolic out of plane comet trail and a spacecraft in the ecliptic plane. Any contacted organic material would be atomized.

    So, beside pouring on more and more storable stages, there are still some other trades.

  • ljk September 17, 2019, 11:55

    https://arxiv.org/abs/1909.06387

    Hidden Planets: Implications from ‘Oumuamua and DSHARP

    Malena Rice, Gregory Laughlin

    (Submitted on 13 Sep 2019)

    The discovery of ‘Oumuamua (1I/2017 U1), the first interstellar interloper, suggests an abundance of free-floating small bodies whose ejection into galactic space cannot be explained by the current population of confirmed exoplanets.

    Shortly after ‘Oumuamua’s discovery, observational results from the DSHARP survey illustrated the near-ubiquity of ring/gap substructures within protoplanetary disks, strongly suggesting the existence of a vast population of as-yet undetected wide-separation planets that are capable of efficiently ejecting debris from their environments. These planets have a≳5 au and masses of order Neptune’s or larger, and they may accompany ∼ 50% of newly formed stars (Zhang et al. 2018).

    We combine the DSHARP results with statistical constraints from current time-domain surveys to quantify the population of detectable icy planetesimals ejected by disk-embedded giant planets through gravity assists. Assessment of the expected statistical distribution of interstellar objects is critical to accurately plan for and interpret future detections.

    We show that the number density of interstellar objects implied by ‘Oumuamua is consistent with ‘Oumuamua itself having originated as an icy planetesimal ejected from a DSHARP-type system via gravity assists, with the caveat that ‘Oumuamua’s lack of observed outgassing remains in strong tension with a cometary origin.

    Under this interpretation, ‘Oumuamua’s detection points towards a large number of long-period giant planets in extrasolar systems, supporting the hypothesis that the observed gaps in protoplanetary disks are carved by planets.

    In the case that ‘Oumuamua is an ejected cometary planetesimal, we conclude that LSST should detect up to a few interstellar objects per year of ‘Oumuamua’s size or larger and over 100 yr −1 for objects with r>1m .

    Comments: 8 pages, 5 figures, accepted to ApJL

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:1909.06387 [astro-ph.EP]
    (or arXiv:1909.06387v1 [astro-ph.EP] for this version)

    Submission history

    From: Malena Rice [view email]

    [v1] Fri, 13 Sep 2019 18:00:23 UTC (172 KB)

    https://arxiv.org/pdf/1909.06387.pdf

  • Mike Serfas September 17, 2019, 13:23

    If the ‘Breakthrough Starshot’ mission is truly more than just an excuse to develop large military lasers, then surely this comet and Oumuamua should be good practice for the system.

    • ljk September 19, 2019, 11:15

      However, if the military isn’t a big factor in the development of these powerful lasers (funding), I doubt they will happen any time soon. Just like how our Space Age would have come much later without the various militaries taking an interest in rockets. Sad but true.

  • ljk September 17, 2019, 14:17

    Here is another type of space sail vessel to ponder:

    http://www.projectrho.com/public_html/rocket/slowerlight.php#swimmer

    • Alex Tolley September 18, 2019, 13:03

      Interesting idea. It seems to be an electrical”pulse jet” using ions that are initially banked by deceleration, then accelerated behind the pusher plate. Whether practice meets theory is another matter. It does seem to require tuning the current energies and reversals to match the ambient ion conditions, but that would seem trivial. As with teh electric sail, it needs a power supply, which the authors suggest should be from a laser back at Sol.

  • Geoffrey Hillend September 17, 2019, 17:37

    Actually, flying to the Sun is easy since the spacecraft’s momentum is increased by the Sun’s gravity. Also it depends whether or not the spacecraft is launched with the orbital direction of the planet which adds to it’s speed or flies opposite or against it to decrease speed. https://en.wikipedia.org/wiki/Gravity_assist

    The Mariner 10 mission had to use a gravity assist in order to have more than one flyby because it did not have the fuel to slow down for orbital insertion of Mercury and NASA wanted to photograph as much as the surface as possible. The Messenger mission needed a gravity assist for orbital assertion since it takes too much fuel to do that.

  • ljk September 18, 2019, 9:14

    When one goes sailing, whether on the terrestrial seas or the seas of space, always bring your star charts…

    https://astroblogger.blogspot.com/2019/09/itelescope-alert-extrasolar-comet-c2019.html

  • ljk September 18, 2019, 9:19

    Early results hint newfound interstellar comet is ‘very red’

    Although it came from another star, astronomers say the latest interstellar interloper shares some striking similarities with comets from our own solar system.

    By Mara Johnson-Groh | Published: Monday, September 16, 2019

    http://astronomy.com/news/2019/09/early-results-hint-newfound-interstellar-comet-is-very-red

    To quote:

    In the meantime, astronomers are rushing to put together proposals to use major telescopes to observe the comet in greater detail in the weeks to come, hoping to measure things like its composition, size and rotation. From preliminary observations astronomers suspect the nucleus of the comet is somewhere between one mile to 16 kilometers in diameter, and it looks like other known comets.

    “From the very early results, it’s similar to comets in our solar system,” said Mike Kelley, astronomer at the University of Maryland who is already analyzing initial data. “It has a similar color, a very red color, which is already an interesting result.”

  • Michael C. Fidler September 18, 2019, 22:15

    Excellent article in Sky and Telescope with a color star chart of Comet Borisov position til January 9, 2020, if you tap on the chart a black and white Pdf file with a higher detail chart will be download. Looks like it will be only 15 magnitude when closest to Earth on December 28, 2019, unless there are some large outburst of Comet Borisov.

    Will Amateurs Be Able to See the New Interstellar Comet?

    We’re all crossing our fingers we’ll see the new comet in our telescopes. Here are some tips on making the best of this rare apparition.

    https://www.skyandtelescope.com/astronomy-news/will-amateurs-be-able-to-see-the-new-interstellar-comet/

  • wdk September 19, 2019, 12:06

    The good news is that current technology applied, we could get there. The bad news might be what can we do once we get there?

    Intercept missions such as the above, with a 13 year elapse between solar pass and
    reaching the objective, that indicates considerable distance from the sun at rendezvous,
    but what is it? I see times of flight in the report, but I don’t see how many AUs out
    the rendezvous occurs. If the outward rate is averaged to 15 km/sec for 13 years,
    that’s about 41 AUs out, about Plutonian distance above the ecliptic plane. If it’s
    double that, then operations start around 80 AUs out. Etc.

    The point is that this object is not as big as Pluto, maybe the size of Ultima Thule.
    It’s not going to be a very bright object. And even navigation for proximitiy operations is going to be a problem. If this is a genuine rendezvous, it might be appropriate to
    carry a flashlight, maybe even radar. True, it’s likely to be the only object in the area to
    give a return. But I have to wonder what deep space tracking is like for missions over the Earth’s south pole.

    • Charley September 19, 2019, 15:01

      Good comment. Isn’t there a NASA space dish somewhere in the Australian outback? Also to, by the time he gets that far out, the trajectory may have curved enough that it’s visible above the Australian horizon; hard to know though.

    • ljk September 20, 2019, 10:24

      Even if all the probe had was a camera, that would still tell us a lot. But of course it will have a suite of instruments.

      New Horizons fed its results back to Earth over the span of one year. Slow but it worked.

      And we should REALLY consider sampling Comet Borisov’s tail particles. We have done this already with other comets.

      • wdk September 20, 2019, 20:16

        Charley, ljk,

        The tail of the comet is moving with some relative velocity to the comet. The actual
        velocity is going to depend on the ejection mechanics on the surface and interaction
        with solar photons and solar wind. But this comet is coming in at hyper velocity
        to the orbital plane. The Earth travels around at 30 km/sec. Were Earth on an
        escape trajectory it would be about 42.2 Mars would be about 24.3 and 34.4.

        Now if perihelion of the comet is at Mars orbit (?) at 1.52 AU and e=3, perihelion velocity I get is double Mars orbital velocity and out of plane ( near perpendicular).
        So, that looks to me like a train wreck at in intersection with 24.3 km/sec x sqrt (3) or 42.08 km/sec.

        Vinfinity has some bearing on the catch up ( say in 13 years).
        Using the same assumptions as above with e = 3 and perihelion at Mars orbit,
        that’s about 24.3 km/sec. Earlier I made a guess of 15 km/sec.

        This would place a rendezvous after 13 years at about 66 AU
        or about 1/4400 Earth illumination from the sun.

        But it’s probably worse than that, since I am judging the
        time of flight between solar maneuver and intercept.
        Solar maneuver was around 2032 and intercept was in 245.
        Rendezvous would be around 120 AUs, taking into account
        the additional headstart Borisov has.

  • DCM September 20, 2019, 14:46

    Getting a sample and bringing it back would be an excellent idea. Let’s not be disappointed though when it turns out to be just another rock.
    We should construct a battery of craft ready to intercept incoming interstellar objects.
    A noticeable number over a short time might prove to be from the same source — maybe an explosion or collision somewhere.

  • ljk September 24, 2019, 9:25

    I know there are plenty of astronomers and other professionals (and no doubt many in the masses) who are nothing short of relieved that Borisov is looking and acting just like a comet, unlike that annoying Oumuamua that had the nerve not to bend to preconceived human notions about interstellar object visiting our Sol system.

    However, if you wanted to send a probe into a star system inhabited by beings that are not only hostile but also on the verge of either galactic expansion or extinction, you might want to camouflage it as something their astronomers would not suspect, or want to admit to anyone else, especially their peers, even in 2019…

    https://www.ibtimes.com/new-interstellar-object-could-be-alien-probe-astronomer-reveals-2831122

    • Ron S. September 25, 2019, 13:54

      If it spouts a tail it’s a probe mimicking a comet to avoid undue attention. If it doesn’t spout a tail it isn’t a comet so it must be a probe. If its trajectory is hyperbolic it’s a probe. If its trajectory isn’t hyperbolic it’s a probe that slowed down for a better look at us. Thus demonstrating that those with strong beliefs are very good at rationalizing their beliefs. An “authority” expressing doubt or presenting contrary evidence only reinforces their beliefs. Ho hum.

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