And new: An experimental German companion to the CM.
Update # 148 of September 27th, 1999, at 19:00 UTC
Contact lost to Mars Climate Orbiter, probably destroyed!Mission declared a loss / Spacecraft came too close to Mars / Probably burned up in the atmosphere / Navigation error already on Sept.15?The Mars Climate Orbiter has probably been destroyed as it approached Mars early on September 23rd (UTC): Only after it disappeared (as planned) behind Mars it was noticed that its trajectory had taken the spacecraft much closer to the Martian surface than planned - it may have come as close as 57 km. That means that the MCO was probably destroyed by friction in the atmosphere as the minimum allowed flyby distance before orbit insertion would have been 85-100 km, and the expected height was 140 km. On Sept. 24 the mission was declared a loss.Flight controllers had expected to regain contact with the MCO - that had started to fire its braking engine - 20 minutes after its disappearance behind the red planet but never heard from it again. An investigation has been launched into the apparent drastic navigation error that doomed the mission. "Yesterday, MCO was approaching the planet to pass within 140km of the surface and all seemed okay," says one of the project's managers, Richard Cook (well known from the Mars Pathfinder success): "However, in the last six to eight hours before the approach we saw a 100 km drop and we don't understand why." It is well possible that the error had happened at the final trajectory correction back on Sept. 15 and gone unnoticed.
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JPL Press Release of Sept. 23rd and Status Report of Sept. 24th. Early reports about the loss of contact: Fla. Today Journal, CNN, BBC (plus an "obituary"), ABC, Space.com, again Space.com, Astronomy Now and SpaceViews. Later coverage and speculation about the cause of the navigation error: Fla. Today, CNN, BBC, Fla. Today again. Mission declared a loss, consequences pondered: Fla. Today, MSNBC, Astronomy Now, Space.com, SpaceViews, Fla. Today again. A PMIRR scientist speaks out: BBC. What could have been: JPL Universe, NASA Science News and an MPG Press Release on MCO's mission. Homepage of the MCO. In other Mars news: The MGS has imaged the Mounts of Mitchel, a patch of frost near Mars south polar cap discovered 150 years ago: MSSS Picture Release, CNN story. |
Breakthrough in exoplanetology!For the first time it has been possible to detect a planet of another star not only by the radial velocity it forces onto its host along the line of sight (and rather easily detected by precision spectroscopy) but also by the slight wobble in the plane of the sky it induces. Normally the radial velocity method, which has led to the discovery of almost 20 exoplanets by now, can only yield a lower limit for the planet's mass because the inclination of its orbits to the line of sight is not known. But with both the radial and plane-of-sky measurements the actual mass can be pinned down.The planet is the outermost one of the three of Upsilon Andromedae (see Update # 126) for which only a lower mass limit of 4 Jupiter masses was known. But the planet also makes the star move a bit in the sky, just barely enough to be detectable by the Hipparcos astrometry satellite. Now the complicated statistical analysis has been published: The mass of Ups And d is 10 +/-5 Jupiter masses! This makes it a definitive planet as the lowest possible mass for any nuclear burning is about 13 Jupiter masses. (The error bars quoted, though, are one sigma; at the 2 sigma level the planet's mass can be anywhere between 4 and 20 Jupiters still. ) The masses of the other two planets should be about 5 and 2 Jupiter masses if it is assumed that all have the same orbital plane. (Mazeh & al., Astrophys. J. 522 [Sept. 10, 1999] L149-151) |
The paper as a preprint. Exoplanet Encyclopedia entry. Discovery report of the 3 planets. Related news: Planet of CM Dra believable? It was detected as a dimming of the star when it moved in front of it, but many doubts remained: the Encyclopedia entry and a new New Scientist article. 'Earths' of other suns could be imaged by bold telescopes proposed by interferometry pioneer A. Labeyrie: his homepage, the EEI vision and a review. See also his article in Science 285 [Sept. 17, 1999] 1864-5! |
Superflares on ordinary Sun-like starshave been observed a few times over the past century: sudden and dramatic brightenings by many factors of ten that would severely influence the environment of Earth if they could happen to our Sun as well. Fortunately they don't (at least there was no superflare in the last few millennia) and perhaps can't at all: One model for the explanation of these giant energy releases proposes that a Jupiter-like planet with a close orbit (several cases of such 'hot Jupiters' have been discovered) and a strong magnetic field has to interact with the star's field to make it snap. The role of superflares for exobiology needs to be investigated: They could extinguish life on a planet's surface but on the other hand deliver the energy to make prebiotic molecules. (Schaefer & al. and Rubenstein & Schaefer, Preprints) |
Paper by Schaefer & al., Paper by Rubenstein & Schaefer. A New Scientist article ( alternate version). BBC coverage. |
Cepheid distance scale: The shaking intensifies!It's definitely back to the drawing boards for those astrophysicists who have boldly claimed to know the distance scale of the Universe to within a few percent: The doubts about the calibration of the Cepheids that suddenly appeared at a conference 4 months ago (see Update # 133, 2nd story) have now made it into the printed, refereed literature. There's no denying now: A purely geometrical method yields a distance to the galaxy NGC 4258 of 7.2 +/- 0.5 Mpc - and the 'trusted' Cepheids (observed with the HST) deliver 8.1 +/- 0.4 Mpc!This difference of 1.3 sigma is a clear sign of problem: The absolute calibration of the Cepheids could be in error. It is based on the distance of the Large Magellanic Cloud, which has remained controversial despite all the progress by Hipparcos and such. If one adopts the geometrical distance to NGC 4258 and calibrates the Cepheids anew with that value, the Hubble constant would increase by 12 +/- 9 percent over the value of 71 km/s/Mpc - that the Ho Key Project had obtained in its final analysis - to 80 +/- 10 km/s/Mpc. And the LMC would come quite a bit 'closer' to us... (Herrnstein & al., Nature 400 [Aug. 5th, 1999] 539-41 + Maoz & al., Nature 401 [Sept. 23, 1999] 351-4) |
Herrnstein's paper as a preprint, an MPG Press Release (in German) after the paper was published and an earlier NRAO Press Release. Maoz' paper as a preprint and a NASA Science News story about it. ABC, MSNBC, Astron. Now and ABQ Journal stories. More cosmology in the news: MACHOs images by Hubble? Extremely faint blue spots in the Hubble Deep Fields, some of which seem to move ever so slightly, could be old White Dwarfs in the Milky Way's halo which could be a major constituent of the local Dark Matter: Preprint von Mendez & Minniti, Science of Sept. 10, 1999, 1653 + Science News of Sept. 18, 1999. |
Major parameters of the Universe get ever clearerCombining the famous supernova data (see Update # 115, main story - but don't forget the problems from Update # 139, 6th story) and measurements of the velocity field of galaxies in space suggests that Omega M is arounf 0.5 and Omega Lambda about 0.8: The two approaches are almost orthogonal to each other, intersecting at around these values. (Zehavi & Dekel, Nature 401 [Sept. 16, 1999] 252-4) That means that a) the Cosmological Constant is large and b) that the Universe is pretty flat. Combined analysis of the supernova data with 9 other methods yields values of Omega M = 0.3 and Omega Lambda = 0.7, a perfectly flat Universe. (Riess, ibid. 220-1) |
CMB experiments also show a flat Universe: The latest generation of ground-based cosmic microwave background detectors, esp. the MAT on Cerro Toco in Chile, is now seeing the critical fluctuation structure that says Omega M + Omega Lambda = 1. (Science of Sept. 17, 1999, 1831; MAT Homepage, another page and another one) |
What the new moons of Uranus meanThe recent discovery of 5 irregular moons of Uranus (i.e. moons with eccentric and/or inclined orbits) - see Updates # 61, 142 and 147 - means that the green planet is not unusal anymore: Until 1997 not one irregular moon was known here while Jupiter, Saturn and Neptune have at least one each. But now Uranus has not only joined the crowd: With 21 known moons in total it's now actually in lead. The other planets probably have more small moons as well, but they are very hard to detect near the bright bodies. (CfA Press Release of Sept. 20, 1999) |
Press Release. ABC, SpaceViews stories. |
Ikonos launched on time!An Athena 2 rocket has launched the second Ikonos hi-res Earth observing satellite (sometimes called a 'spysat for everyone'; resolution 1 meter) on time on September 24th: Homepage, Fla. Today coverage, Space.com, MSNBC, Space Daily, Astronomy Now, SpaceViews stories. What it all means: the NYT on the new "age of transparency".New Chandra images of SNRshave now been taken, showing previously unseen features in the wreckage of three exploded stars: MSFC Press Release, Chandra picture gallery, NASA Science News, BBC and CNN stories.XMM arrives in Kourou - the European X-ray satellite will be the next Ariane 5 payload in December: ESA XMM News. Big bucks at space auctionAmazing sums of money were paid at the Sept. 18 space memorabilia auction in NYC, e.g. $310,500 for a NASA tag coated with moon dust: Sales Results (requires reference to the catalog for the lot numbers - here is another version with short descriptions), Christies Press Release, CollectSpace, SpaceViews, Space.com stories.What does the success mean for collectors in the future, CollectSpace wonders. And the price for moondust could collapse if a private company succeeds in getting much more to Earth: Space Daily.
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New launch delays for the shuttlehave become necessary, mainly as a consequence of the ongoing wiring inspections: There won't be a mission before Nov. 19 the earliest, and priority is given to the HST visit, with the SRTM possible in December: KSC Status of Sept. 24, SpaceViews, Space.com stories.USA to pay penalties for shuttle delays - 3 million bucks for each launch: SpaceViews. The full cost of the delays isn't known yet: Fla. Today. The ISS may go to a private company: NASA is willing to turn over operation of the new international space station to private enterprise, perhaps within the next decade, space agency Administrator Dan Goldin has said - Fla. Today. Subaru telescope inauguratedOn that occasion (Sept. 17) a new set of pictures was published: Press Release. And the NYT on what Subaru means for Japan.GM Sgr in outburstA known variable star apparently is acting up, feeding materials to a massive, compact companion that shows its appreciation with a brilliant X-ray belch: NASA Science News, Space.com story.
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Compiled and written by Daniel Fischer
(send me a mail to dfischer@astro.uni-bonn.de!), Skyweek