Friday, July 21, 2017

The #mu69occ campaign: Occam's razor wins again ...

On July 17 the third and final attempt to observe a stellar occultation by the next target of the New Horizons mission in the Kuiper Belt, 2014 MU69, succeeded with several telescopes seeing the star blink out briefly - in contrast to a similarly effortful attempt on June 3. In spite of placing two 'fences' of portable telescopes perpendicular to the expected shadow track, none of them saw anything. When this was finally acknowledged over a month later, the respective press release from NASA and the JHU APL was full of wild speculations about how MU69's shadow could have slipped somehow through the telescope fences and tried to spin the campaign's negative outcome as a success. Of course it wasn't: you can only claim success when at least one telescope has seen the target star blink out.

Furthermore occulation observers know from decades of experience - especially from the past century - that by far the most likely explanation for a total failure is that the shadow track had not been where it had been calculated: this could be due to either bad astrometry of the star or a bad orbit of the occulter. This, however, wasn't even mentioned as a possibility in the official word - and when I asked scientists involved in the campaign about it, I got either no answer at all or a snarky one at best. Apparently the use of unpublished Gaia astrometry of the star and HST astrometry of MU69 to determine its orbit had made it all but impossible in their minds that the June 3 shadow track could have shifted beyond all telescope fences.

Alas, this is exactly what had happened, New Horizons' Alan Stern has acknowledged now: "we [...] didn't put telescopes in the right place because back then we didn't have the MU69 orbit prediction well enough in hand. Subsequent HST June-July data helped with that." So there, the - by far - most likely explanation for the June 3 failure was the right one indeed and all the speculations were wrong! Fortunately the negative observations from back then (and whatever SOFIA saw or didn't on July 10; that's still kept secret) can now be put in context as the offset of the telescopes from the true shadow track can now be calculated and secondary bodies or debris or even a ring can be excluded at that relative location from 2014 MU69. A happy ending for the campaign and for New Horizons - and a lesson for press release writers trying to make a failed observation look good ...

Sunday, June 11, 2017

German artist triggers solar eclipse detective work

A brief article on an art exhibition in Zurich (a press release here and here) has just sent me on an unusual eclipse chase. The photo artist Thomas Ruff has a weakness for space topics, and one of the objects now depicts a total solar eclipse! Ruff's modus operandi here is to take old press photos and copy the caption from the back side onto the front side as well - which so happens to be readable only in fragments on the image of a solar corona shown in the article (which often hides behind a paywall anyway), though.

In particular the year of the eclipse is not evident - but one can read that the image was taken from a KC-135 airplane over the Atlantic near South America. According to this article (page 5) and this one (page 6) the KC-135 astronomy program covered 6 eclipses from 1965 to 1980 - and the only eclipse fitting geographically [ADDENDUM: no; see below] would be the one in 1973. Which, of course, is the same that was also observed from a Concorde by other astronomers: the KC-135 observers actually watched the latter pass way above them at an amazing speed.

I may add that I actually once met Ruff in a professional context ... in 1991 at the Kunstverein in Bonn, Germany, where he had an exhibition before becoming a celebrity showing the "Sterne" series. Together with a friend we created an astronomy-didactical show in which we tried to convey the depth in these huge prints of ESO sky images that contained stars, galaxies but also occasional satellite tracks. I don't recall much but one detail: I had prepared a square meter of paper with a square millimeter marked on it to demonstrate what a million - being the difference in area - meant. We couldn't come up with a means to demonstrate a billion, though ...

ADDENDUM: Airborne eclipse expert Glenn Schneider has pointed out in personal messages that the 1966 TSE is a much better fit when a KC-135 also observed - several text fragments that can be deciphered match actual information on that flight. "The name of the place is not very legible," says Schneider, but it sure looks like Rio Grande which "is on the coast (not too far away) and is very close to 240 miles from greatest eclipse" - where you logically would fly with a research aircraft. And from what one can read the plane was "240 miles southeast of" said town.

Schneider also points out that while the 1973 TSE was visible low from parts of South America, that's a long way "to where the Concord flew across Africa! You are right that in 1973 the guys in the KC-135 watched the Concorde streak by overhead at 55,000 ft - but they were over Africa, not South America or the nearby coastal waters. Finally I will add, the corona in that picture, though not a very good picture, just does not look like the 1973 corona. I did not see the 1966 eclipse as it pre-dated my eclipse chasing started in 1970, so I cannot comment on that directly. But I did see 1973, and that just doesn't look the same..."

Saturday, May 27, 2017

Another impact flash on Jupiter - and I helped confirm it!

This afternoon Marc Delcroix, Damian Peach and Ricardo Hueso Alonso spread the news that Sauveur Pedranghelu in Corsica had probably recorded another impact flash on Jupiter yesterday - but there was no confirmation from another site, essential to rule out some flash (e.g. from an artificial satellite) close to Earth. I distributed the news and call for observations in various other Facebook groups and also on the Facebook page of Abenteuer Astronomie, a German astronomy magazine I'm with.

Within hours in the comments to the latter posting I learned that Andre Fleckstein had indeed filmed the same flash! The time was 19:25:18 UTC on 26 May 2017, i.e. smack in the middle of the time interval given by Pedranghelu, and the duration was about one second. The quality of the video was described as poor, due to bad seeing, but one could see the flash well while it was running. Fleckstein also provided a quick screenshot, upside down w.r.t. Pedranghelu's image - and the flash is clearly there, as confirmed by Peach and Alonso. The Fleckstein video will now be processed further, and scientific analysis will follow.

ADDENDA: a stacked version of Fleckstein's data, now in the same orientation as Pedranghelu's image, and a further processed version together with an explanation - and yet another confirmation of the impact, as a video clip and also nicely stacked the same way as the other two videos! Also a first report on and some more analysis of this triple success - and a depiction as space art, by a well-known Jupiter observer. Meanwhile an image sequence starting minutes after the impact or this hi-res image a bit later aren't showing any traces, typical for such events.

Saturday, February 11, 2017

Stop. That. Hype.

And so it happened again: when last night's penumnbral lunar eclipse coincided with the perigee of a faint comet (i.e. two less-than-stellar events for the public at large) all hell broke loose in the "science" and general media around the globe. The claim went that three "dazzling" (for everything in astronomy "dazzles", right? Except black holes perhaps. Which suck) sky phenomena were visible at the same time: a "snow moon", a lunar eclipse and a "mysterious green" comet. Oh yeah?
  • That "snow moon" term which suddenly invaded even German 'news' stories is of dubious provenance and in any case related to U.S. East coast folklore at best. Adopting it blindly around the globe makes no sense culturally, let alone geographically (Africans and Australians might agree). And why on Earth does each and every Moon need some fancy nickname nowadays?

  • Talking about three sky events makes no sense either as the lunar eclipse is an effect of said full moon. And regarding its relevance confusion abounded: some mixed it up with total eclipses, others claimed nothing would be seen at all - while in fact from past experience one could predict a quite distinct darkening so close to the umbra. Which was the case indeed, obvious - though not dramatic - even under bad conditions.

  • The worst mistake, however, was throwing the poor comet 45P/HMP into the mix, which has faded (in absolute brightness) since perihelion and lost most of its tail by now. Close to Earth it grew into a fuzzy blob half a degree in diameter but only of 7th magnitude: completely drowned out by the bright sky the full or nearly full moon causes. To advertise it in connection with a a full moon / non-total lunar eclipse was sheer madness.
Now you might say, so what, any astronomy in the media is good astronomy - but that is dead wrong. As one can read today in social media in reports by amateur astronomers talking to lay people the disappointment runs deep: "the media" or worse "the astronomers" predicted something exciting, and it didn't occur. In these times of - deserved or undeserved - widespread growing distrust in journalism even such small sins should be avoided. So please think first before promising things the sky won't or can't deliver - it'll hurt us all in the end ...