Did SOHO’s Comet Survive? The Hunt Is On!

Newly-named Comet C/2015 D1 (SOHO) will share the sky with Venus and Mars at dusk. For the next few nights it will be quite low and nearly impossible to see. Its situation improves over time as the comet moves rapidly northward into Pegasus and Andromeda. Tick marks show the comet's position each evening. Stars are shown to magnitude +6.5. Created with Chris Marriott's SkyMap software
Newly-named Comet C/2015 D1 (SOHO) will share the sky with Venus and Mars at dusk. For the next few nights it will be quite low and nearly impossible to see. Its situation improves over time as the comet moves rapidly northward into Pegasus and Andromeda. Tick marks show the comet’s position each evening. Stars are shown to magnitude +6.5. Created with Chris Marriott’s SkyMap software

There’s no telling whether anyone will yet see the “phoenix comet” that survived a close encounter with the Sun last week and continued to keep it together until it exited the coronagraph on the orbiting Solar and Heliospheric Observatory (SOHO).

The last we heard, SOHO-2875, now formally named C/2015 D1 (SOHO), still glowed around magnitude +4 on Feb. 21.

Now the hunt is on to see if enough of the comet remains after its perilous journey to make an appearance in evening twilight. After many position measurements from photos taken by SOHO, an orbit has been calculated that was just published today. Using those numbers, I made a map showing the comet’s nightly progress as it travels up from the western horizon not far from Venus and Mars through the constellations Pisces and Andromeda over the next couple weeks.

Don’t expect to see it tonight. It’s likely no brighter than the naked eye limit (magnitude +6) and swamped in the glow of twilight very low in the western sky. Still, by good fortune, it just happens to hover very close to the star Gamma in Pisces about 5° above the horizon near the end of dusk.Those with crystal clear skies and an open view to the west should give it a try.

The situation soon improves as SOHO’s northward movement carries it higher into a darker sky. It’s uncertain if the comet is a tight, dense ball or a ballooning bag of dust. Until the first observations come in, we won’t know how the comet’s fairing. Also keep in mind that the orbit is preliminary, meaning C/2015 D1 may not exactly follow the path shown. Do sweeps around the positions, moving left and right and up and down from each nightly spot.

I’m as eager as you to see our new visitor.

10 Responses

  1. Chris

    Thanks a lot for your Information, dear Bob.

    Yes, let us see what will happen. Things are very exciting. Miracles are the most wunderful events in this Uni-verse! Let us hope and pray for the BEST. Justice, Truth, Peace, Love, Freedom for all the good, for all the just, all the foltered, all the killed, all the suppressed and persecuted by injustice, especially all nature, animals, plants, children, killed, destroyed by the demons of vanity and hate.

  2. Edward M. Boll

    With SOHO around 20? degrees from the Sun, I doubt that the magnitude could be brighter than 2. I hope that it is brighter than magnitude 9. If it is dimmer than that it will likely fade out very quickly.

  3. Ray

    Very interesting. I’ve been playing around with the MPC positions on an orbital determination program and I am getting a similar but slightly different orbit from the MPC: q=0.02925068, Peri.=236.40076, Node=40.97556, Incl.=106.22113, e=1.0055818, T=2015 Feb 19.740296. I checked both orbits on Stellarium and they follow extremely similar paths during the period of SOHO observation. However, the differing angular elements mean that on my orbit, the comet stays very close to the sun much longer than the MPC orbit (elongation 17 deg., mag. 13 on March 1 and elongation less than 30 degrees for the rest of March).

    But of course the observational arc is so short that an number of orbits could satisfy the positions… I’m hoping for the best, but it seems unlikely that I’ll be able to get any visual observations unless the comet fades slowly.

      1. Ray

        I calculated three similar orbits, one using pre-perihelion obs., one using post-perihelion obs., and one using all of the positions. The epoch of the one I mentioned above is at the last date of observation.

  4. Hi Bob.
    Is there any plans to observe D1 with other assets in space as in the STEREO’s and MESSENGER and the orbiting space-telescopes as it moves away from Sol?

  5. Edward M. Boll

    I calculate that Comet Howell rises about 2 hours before sunrise.That is not soon enough for a 10th or 11th magnitude comet to be visible. Missing out on that one, I was hoping that SOHO might act as a replacement comet for those of us in the north hemisphere. But if it is fainter than Howell, most of us will not see that one either.

  6. Bob

    Do you still believe comets are dirty snowballs just because NASA says so? Reality is that comets are asteroids with an opposite electrical charge relative to the sun. 3200 Phaethon is an excellent example. Have you ever considered independent thought as opposed to simply regurgitating everything NASA plants in your infinitely manipulable mind? You are the first one in line to strike the match when an independent thinker is burned at the stake for expressing an idea that does not conform to prevailing dogma.You do not think, therefore you subscribe to every scam. Truth is in the eye of the beholder. Unfortunately, you are incapable of believing your own lying eyes. Forgive my sarcasm, but many discoveries are vigorously resisted simply because they do not tow the commonly held line. Climb out of the box, my good man, and discover the liberation of independent thought.

    1. astrobob

      Bob,
      When the claim for asteroids having an opposite electrical charge to the Sun (whatever that means) is verified by evidence, I’d be happy to believe it. In the meantime it’s nothing but conjecture. If you’re referring to the solar wind, it’s been verified to be electrically neutral because it’s composed of an essentially equal number of positive and negative particles. As long as empirical evidence is brought to bear, I and many of the other readers of this blog are prepared to embrace a new concept. Thunderstorms giving rise to gamma rays is a case on point. Who would have thought this possible a couple decades ago? Now there’s hard data including photographs that show it to be true. I love new discoveries but have little patience for the pseudoscience and false information behind the “electric universe”.

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