Pinwheel Supernova, Comet Elenin Updates And The Holy GRAIL

Look how bright the supernova is! This photo was made with a 14-inch telescope on September 3. Credit: William Wiethoff

Lots of news in the world of astronomy this week. First, let’s do some updates. Supernova SN 2011fe  in the Pinwheel Galaxy (M101) appears to have peaked at magnitude 10.0 according to my own estimates over the past few nights using charts available from the American Association of Variable Star Observers. That makes it the 6th brightest supernova ever seen outside the Milky Way system.

We’re now headed for full moon, so the galaxy appears faint to invisible in most telescopes. Don’t let that stop you. SN 2011fe is so bright, you can star-hop to it without the need to even see the galaxy! Recent observations show that debris is expanding away from the supernova explosion at some 12,000 miles per second. I updated the finder chart for a third time to help get you there. Click HERE to see it and a telescopic map.

Mercury and Regulus will hang together in the east tomorrow morning about 45 minutes before sunrise. Mercury will be noticeably brighter than the star. Created with Stellarium

Tomorrow morning (Sept. 9) the bright planet Mercury is in conjunction with Regulus, Leo the Lion’s brightest star. If you’re up around 6 a.m. and have a great view to the east, try to spot the pair low in the sky far to the left of the stars Procyon and Sirius.  Mercury should be fairly easy to see with Regulus requiring a little more effort. Keep your binoculars handy.

Two views of Comet Elenin. At left photographed by Michael Mattiazzo of Australia through an 11-inch telescope on Sept. 6; at right by John Drummond of New Zealand with a 14-inch telescope on Sept. 3. The comet looks different in each picture because different instruments and exposures were used.

Some of you have e-mailed me asking what’s happening lately with Comet Elenin. It’s still rather faint — around 9th magnitude — and the comet’s coma continues to fade and spread out as the nucleus disintegrates. Well-known Japanese comet observer Seiichi Yoshida’s new light curve, which is a prediction of of the comet’s future brightness based on current and past behavior, shows Elenin only reaching 8th magnitude in October at brightest. That would make it faintly visible in binoculars under rural skies.

The comet reaches perihelion or closest distance to the sun this Saturday at 44.6 million miles or about half Earth’s average distance from the sun. Everyone eager to see Elenin when it pops into the morning sky next month hopes it survives the additional heating and more powerfully-felt solar  gravity at perihelion. If so, perhaps the comet will be bright enough to see in the Solar and Heliospheric Observatory’s C3 coronagraph a couple weeks before we see it in the dawn sky. Comet Elenin should be in the instrument’s field of view from September 24-28.

Orbiting in formation around the moon, the twin GRAIL spacecraft will map the moon's gravity field. Radio signals traveling between the two spacecraft provide scientists the exact measurements needed to create the most accurate gravity map of the moon ever made. Credit: NASA/JPL-Caltech

Weather forced NASA to scrub today’s launch of the Gravity Recovery and Interior Laboratory (GRAIL) mission to the moon and re-schedule it for early tomorrow morning. Two identical spacecraft will be sent to orbit in tandem around the moon for several months. Using a microwave signal, the distance between the two probes can be measured with great precision. By watching that distance expand and contract as the pair fly over the lunar surface, researchers will be able to map the moon’s underlying gravity field.

“These measurements will tell us a lot about the distribution of material inside the Moon, and give us pretty definitive information about the differences in the two sides of the Moon’s crust and mantle. If the density of crustal material on the lunar far side differs from that on the near side in a particular way, the finding will lend support to the ‘two moon’ theory,” according to David Smith, GRAIL’s deputy principal investigator at MIT.

Four snapshots from the computer simulation of a collision between the moon and a smaller companion moon show most of the companion moon is accreted as a pancake-shaped layer, forming a mountainous region on one side of the moon. Credit: M. Jutzi and E. Asphaug, Nature.

The two-moon theory is a recent attempt to explain why the farside of the moon is so different from the nearside. The farside is covered in mountainous highlands and saturated with craters, while the nearside is dominated by vast, lava-filled impact basins or ‘seas’. The seas are the dark blotches that comprise the face of the ‘man in the moon’ most noticeable around the time of full moon.

Martin Jutzi and Erik Asphaug of the University of California at Santa Cruz believe that two moons formed when Earth was struck by a Mars-sized asteroid early in its history. The resulting debris from the collision may have created a larger body that would ultimately become the moon and a smaller moon that later collided in a more gentle fashion with the larger body. Instead of gouging out a huge crater, it went splat on what’s now the lunar farside, coating it with a thick layer of debris. It’s an intriguing idea, and one scientists hope the GRAIL mission may provide more evidence for.  To read more on the topic, take a look at this NASA release.

16 Responses

  1. Iceberg

    i think the two moon theory is somewhat believable however its very curious that the sumerian myth of creation of the moon is somwhat similar except the earth (tiamat) was the big sphere and the moon we see today was the small sphere… the smooth nearside is the side that hit this planet where the Pacific ocean is today… the so called ring of fire is the impact crater and the mid atlantic ridge is the resulting bulging… throw in some plate tectonics and we might have a theorem. very interesting stuff this astronomy.

    1. astrobob

      Hi Iceberg — Your Pacific Ocean idea reminds me of the old “fission theory” for the moon’s formation, when it was believed that the moon spun out from the Pacific Ocean due to a rapidly rotating Earth. This idea was popular in the early 20th century but later discredited for lack of evidence. When I was a kid, books showed this amazing illustration of the moon stretching away from the Earth. I loved it. As to the location of the impact between Earth and the Mars-sized asteroid/planet, no one knows. The Pacific Ocean is relatively young, having formed only some hundreds of millions of years ago. The moon in contrast formed about 4.5 billion years ago, so the two are not connected. Whatever may have been present for a landscape back then is long gone.

      The two-moon theory posits that the second, much smaller moon ended up for a time in one of the stable, Earth-moon Lagrangian points. From there it eventually migrated out and struck our current moon.

  2. mike

    About to buy my telescope. What books should I get?

    Also I think you mentioned a red-dot finder for the scope? Any other accessories a beginer should have?

  3. Larissa Hills


    1. astrobob

      Larissa — Nova still means “new star” in a figurative sense. Astronomers now know that a nova happens in a very close double star system where one star is similar to the sun and the other is a very tiny, fantastically dense star called a white dwarf. The dwarf pulls gas from its companion, which piles up on its surface until enough is there to ignite and burn. The burning lights up the star system and astronomers call it a ‘nova’. Not a new star, but rather an outburst of the star. Novae have multiple outbursts spaced years apart.

  4. stephanie

    hi bob quick question did elenin go through perihelion today or did it slow down? cause I read it slowed down till tomorrow or the 13th? is their any truth in this or no? thanks again I just dont know who else to ask!!!

    1. astrobob

      The comet is at perihelion today and then on the 13-14th passes through the plane of Earth’s orbit. It only begins to slow down after perihelion as all solar system objects do after their closest approach to the sun.

  5. stephanie

    Thanks Bob!!! did they ever confirm if it was breaking up or not? still just trying to keep up to date with out reading all the trash thats spread out on the web about it…. the only thing I read was American radio astronomers report that did not detect any water coming from any remains of comet Elenin… what does that mean? would you mind explaining please!?? I read that off Leonids facebook but I didnt understand! thanks

    1. astrobob

      Stephanie — Not positive what it means. I saw the post as well. Maybe Elenin’s a particularly dusty comet with less water than some others. More likely, a breakup of the comet would cause a rapid increase in the amount of water at first, which would then be followed by a quick decline as the fragments vaporized away. Since these were the first radio telescope observations, the peak of the breakup (which appeared to happen sometime in August) may have passed, leaving little water left to detect. Just my hunch.

  6. stephanie

    could that effect earth in anyway? or is this normal for some comets? and will it stay on the same path? and will it still be visable to see in Oct still?

    1. astrobob

      Could that effect earth in anyway?
      — No.
      Is this normal for some comets?
      — I don’t know how normal it is, but it has been observed before. Breakups in particular aren’t uncommon.
      Will it stay on the same path?
      — Yes
      Will it still be visable to see in Oct still?
      — Yes, but will likely be much fainter than early predictions.

  7. buffy

    Hi bob I have been hearing alot of things about comet elenin and blocking the sun my question is… Today it was closest to the sun right wouldnt it blocked out the sun today if it were that big? Sorry for such a dum question! But my daughter is 12 and read about it and I want to ease her mind from any fear she is having !!please explain that everything is going the way it should be and has been with hundreds of other comets please! Thank you

    1. astrobob

      Hi Buffy,
      Comet Elenin is much, much too small to block the sun. The actual solid object – the comet – is only a few miles across. Now imagine even trying to see something that size from a distance of 65 million miles (its distance from Earth today). It would smaller than the smallest pinpoint! Not only that, but from our perspective today, the comet is not lined up with the sun but off to the side. The closest the comet gets to the sun from our perspective is 2 degrees (four full moon diameters) north of it on Sept. 26.

      Comets do have large, rarefied atmospheres called comas. Elenin has a good-sized coma, but it contains so little material it’s nearly transparent to sunlight. Elenin’s coma is presently about 4.5 minutes of arc in diameter or 1/6 the size of the full moon. Even on September 26, the comet will be too far north of the sun for its small coma to even come close to an Earth-sun lineup. Again, even in an imaginary perfect lineup, we’d never notice a thing, because comas are so tenuous.

  8. Wes Jones

    Interesting topic here . . . in my searches I came across a very concise description of what’s happening with this comet : . The common notion that comets are loosely packed snowballs, etc. has been severely challenged by the results of recent NASA missions to comets Tempel 1 and Wild 2 which suggest that they are more like cousins to asteroids, with their main difference being their electrical charge state (this results in the coma and tail phenomnon when they enter the positively charged environment nearer the sun). I think you will find the perspective presented by the “Thunderbolts” team a little more satisfying and better aligned with observations than even NASA’s presentations. A full review of what a comet is can be found here : .

    Welcome to the latest in cosmology.

    1. astrobob

      Hi Wes,
      More like welcome to the latest hokum.
      Nothing personal but the “electric comet” idea is a fringe/junk science concept. There is no scientific evidence for it. All the stuff in the article sounds and feels good, but it’s completely concocted. The solar wind is electrically neutral and not positively charged. Comets are not negatively charged. We’ve sent spacecraft to them and no evidence for these charges have been found. Nor are there proven causal connections between CMEs and comets blowing up. The beat goes on 🙂
      Best wishes,

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