Will Earth Perish by Fire, Ice or Black Hole?

On last night’s news, veteran PBS news anchor Gwen Ifill interviewed a prominent astronomer to solicit comment on the recent discovery of two enormous black holes hiding in the bright central bulges of the giant elliptical galaxies NGC 3842 and NGC 4889.

The scientific news itself went “viral,” being picked up on BBC, The New York Times, Huffington and elsewhere that I can recall, as well as in the scientific journals. The Sky & Telescope article is much more oriented toward readers who are already familiar with cosmological objects and distances. It can be picked up at this link.

You can also read the PBS transcript of Ifill’s interview with Chung-Pei Ma. Ma is professor of astronomy at the University of California, Berkeley. She appeared visibly constrained by the problem of how to explain these concepts to a general viewing television audience.

But the item here concerns Gwen’s question to Chung-Pei Ma. Presumably Gwen had done her homework and knew the answer, but most viewers might not:

GWEN IFILL: Nearby, but not a threat? I mean, we’re not — you’re talking about black holes that suck in light and gases and everything in its path, but we’re not in its path?”

Ma tried to explain, in lay terms, why not. Breaking this question apart, the salient components of a better answer would be:

  • how far out do the effects of these monster black holes reach?
  • how far away are we now?
  • how long in years could an approach to within their spheres of gravitational influence take?

Facts:

  • Both galaxies in question are about 300 million light years away.
  • “For NGC 3842’s central monster, the team found a mass between 7 and 13 billion Suns; for NGC 4889 the range is much bigger: 6 to 37 billion solar masses” [Sky & Telescope].
  •  In other words, each black hole’s estimated bulk suggested it had already swallowed the mass equivalent of an entire “ordinary” galaxy.
  • The “event horizon” of each black hole – the boundary inside of which even light cannot escape the black hole’s unimaginable gravitational field – is estimated at around 3 to 5 solar system diameters.
  • Our Solar System has a diameter of about 0.001 light year. To put this into some kind of perspective, our Milky Way galaxy has a diameter of about 100,000 light years.

Discussion:

  • So, our Milky Way (which has a large black hole of its own) is about 3,000 Milky Way diameters away from NGC 3842 and NGC 4889.
  • Looking at the second illustration in the Sky & Telescope article, and the companion text, it appears that only the the motion of stars within 1,000 light years of their black holes NGC 3842 and NGC 4889 are affected by the nearby dark monsters.
  • We are 300,000 times further way than that.

Devil’s Advocate:

But … but … supposing some cataclysmic upheaval were to propel our solar system, or our planet, toward those monster black holes? How long might it take for them to tear us apart? How fast could an “object” like us move in that direction?

Obviously, we’d have to move really fast.

  • Let’s disregard the fact that any catastrophic event powerful enough to do that would also undoubtedly shred Earth to dust, if not elemental gases.
  • A supernova explosion of our Sun might propel an expanding sphere of gases and dust outward at 11 million miles an hour, though it’s a fact our Sun is way too small to go supernova.
  • According to a Stanford article  “THE MYSTERY OF THE FASTEST MOVING STAR STILL PUZZLING,” they mention a candidate speed in this question: “How do you accelerate 2.7 octillion tons (27 followed by 26 zeros) from a standstill to over 1,800 kilometers per second, about one- half of one percent of the speed of light? That could be as fast as 4 million miles per hour.”

So, even at the catastrophic speed of one percent of the speed of light (give or take), hurtling straight toward either of those two monster black holes, it would take us something like 30,000 million years to reach a destination 300 million light years distant. The universe is currently 13.7 billion years old. Cosmologists think it might be good for another 10 or 20 billion years or so before perishing in fire, or ice, or whatever.

In short: since 30,000 million years is 30 billion years, the universe may not even exist by the time a battered Earth arrives at NGC 3842 and NGC 4889 at the improbably high speed of only one percent of the speed of light. Any slower than that, we’d never arrive, nor would there be any destination to arrive to. I don’t think we have to worry about it too much.

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Hubble Directly Images Black Hole Accretion Disk

For the full story see the NASA Hubble site: NASA/ESA managed to combine the powerful Hubble Space Telescope with the incredible sling-shot magnification of gravitational lensing to produce what appears to be mankind’s first visible-light image of an accretion disk. .

 

An international team of astronomers has used a new technique to study the bright disc of matter surrounding a faraway black hole. Using the NASA/ESA Hubble Space Telescope, combined with the gravitational lensing effect of stars in a distant galaxy [1], the team measured the disc’s size and studied the colours (and hence the temperatures) of different parts of the disc. These observations show a level of precision equivalent to spotting individual grains of sand on the surface of the Moon.

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Interstellar Time & Distance

In this Sunday’s comic strip “Beetle Bailey”, the dumbest guy in Camp Swampy asks the smartest questions, and nobody knows the answers. Zero: “Boy! I’d like to visit one of those stars.” Sarge: “It would take you years to travel through space to get to one of them.” Exactly. But how long would that really take?

Beetle Bailey by Mort Walker
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Mars Hoax 2010

HOAX: Two moons 27th August 2010

The annual “Two Moons on Aug 27th” Mars e-mail is circulating again. Alas, the myth is another internet hoax, a best fit for the “liar liar pants on fire” category. Amateur astronomers already know this. This year, for the benefit of everybody else, we do our best to explain why.

A picture is worth a thousand words. See: http://www.astronomy.org.gg/hoax.htm

from astronomy.org.gg - click graphic for source article and image

The photo above is also true to my own experience, as I’ll narrate below.

Wikipedia on the “Mars Hoax” (emphasis mine):

Although nearly all of the claims made in the e-mail are true, the hoax stemmed from a misinterpretation of the third sentence of the second paragraph which states that “At a modest 75-power magnification Mars will look as large as the full moon to the naked eye”. The message was often quoted with a line break in the middle of this sentence, leading some readers to mistakenly believe that Mars would “look as large as a full moon to the naked eye” when, in reality, this only applies when a telescope with a 75-power magnification is used. This is the most likely source of misinterpretation.

We will never, EVER see a sight even remotely like the faked “two moons” e-mail image from Earth (or from anywhere else in the solar system). And 2010 is not even a particularly good year for telescopic viewing of Mars.

We already had Mars’ 2010 “closest approach” in January . Most non-astronomer citizens never would have noticed it. Phoenix and Bay area residents would probably be unable to see it with the naked eye unless it was an exceptionally clear night.

We actually have mathematical “closest approaches” every other year or so (Mars takes 687 Earth “days” to orbit the sun). Obviously, since both planets orbit the sun, there is always going to be some “closest” distance as the Earth swings round past Mars. That distance is not the same each year because the orbits if the two planets are not quite concentric, but elliptical — not quite perfect circles. Mars’ orbit is quite eccentric for a planet – about 9% longer on the long axis compared to the short dimension.

In 2003, we had the celebrated closest Mars approach “in 60,000 years”. Astronomers would have noticed Mars having an apparent diameter of almost twice its “farthest distance”. This difference doesn’t become readily apparent without a telescope of at least 6″ diameter.

The angular size of the Moon is about 1/2 degree (30 ARC MINUTES). By coincidence our Sun is of the same apparent diameter, which is why we can have perfect lunar eclipses. NASA confirms the angular size of Mars varies from a minimum of 3.4 ARC SECONDS to a maximum of 25.1 ARC SECONDS.

An arc second is 1/60 of an arc minute. Mars never stood a chance of looking close in size to the Moon!

From University of Wisconsin:

Even at its closest approaches Mars seldom appears larger than 26 arc seconds, or about 1/69 the apparent size of the moon.

Some sources compare this to the apparent size of a penny at 500 feet.

We all know from experience the Moon NEVER looks about the size of a penny at 500 feet. The Moon might look more like the size of a basketball at 100 feet. So how could Mars ever look like it was almost the same size? It can’t.

If that isn’t bad enough for backyard astronomers, more math (groan) conspires against us too. Remember that the area of a circle is proportional to the square of the radius. So, a planet of radius 1/2 will only display 1/4 the surface detail of a planet of radius 1, all other things being equal. A planet of radius 1/60 can, at best, display 1/3600 the surface detail of the larger one — not counting the distorting effects of the Earth’s atmosphere!

The 2003 Mars approach was a HUGE disappointment to Bob and me, and we (I) wasted a good deal of money trying to be ready to photograph this highly publicized event.

As actually viewed with the naked eye in 2003, it was hard to tell whether any kind of “disk” of Mars could be made out at all, or if Mars was just a really bright reddish point-source star like Aldebaran. With eye to our telescope eyepiece, we were barely able to see Mars’ polar icecap, but that was all. Bob and I tried to photograph Mars through the 8″ telescope with an expensive SLR camera body, without much success as we were inexperienced in photographing the night sky. Bob did the best job, holding up a “Brownie point and shoot” to the telescope eyepiece.

Our photo looked about like a penny at 500 feet. Copper-red, no surface detail visible at all. Unless you blow up the image (below), Mars looks like a little red dot in a huge black frame. This photo has been published here before. For a better color photo (looks like black-and-white), see also our Mars Elusive post (9-17-2003).

Mars 2003 - photo by Bob Sibley

The next “good” year for viewing Mars will be 2014, and it won’t get as good as 2003 again during our lifetimes.

Alex

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National Geo: Seeking new earths

rocket launch - from National Geographic

rocket launch - from National Geographic

There’s an article of interest in the December 2009 National Geographic, “Worlds Apart: Seeking new earths”. Written for National Geographic by stargazer Timothy Ferris, the article discusses, in lay editorial style, the mission of NASA spacecraft Kepler (the launch image on this page).

Also discussed with excellent graphics is a foldout showing new planets that have been found so far. The newsprint magazine also presents thumbnail concepts of current detection techniques, including subtle changes in parent star luminosity, and doppler wobble.

For those of us who don’t have access to the current old-fashioned subscription magazine (which I prefer), here are current links to the National Geo articles:

The chart covers the 373 found planets (as of when the issue went to press). I didn’t realize we had identified orbiting planets out to 10,000 light years distance. At least one “planet” is really a failed star (17 times Jupiter’s mass) – it should have gone thermonuclear.

Since Andromeda is our nearest neighboring galaxy, some 2.5 million light years distant, the article doesn’t report any discoveries there, and most likely none have been observed. For ET hunters it might be somewhat unsettling to realize that there is no way Earth could be seen from Andromeda with what we consider state of the art technology. Newly launched Kepler will peer out 15 times farther than current sightings, that is, 6,000 lights years distance, as opposed to the current 400.

In that case, where exactly are the host stars for our 373 observations to date? They seem to all be in own Orion Spur of the Milky Way’s  Sagittarius arm. Even Kepler is confining its search area to this spur.

For the seasoned amateur astronomer, there is perhaps not much content we haven’t read elsewhere, at some time or other,  in astronomy magazines and websites. But the National Geo presentation is well-organized, as generations have come to expect from that publication, and well worth our review.

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The Great 2012 Scare – Sky & Telescope

When we wrote our two October postings on the “2012″ doom-and-gloomers, we debunked the myth, as many others have done. We also referenced the Sky & Telescope magazine’s impressive articles stating that the world is not going to end in any of the ways the movie or the Nostradamus and Mayan Calendar fetishists are predicting, at least, certainly not as the result of any known astronomical phenomenon expected in that year or century.

And we noted with regret that the S&T magazine’s website was “under construction” and we could not provide the customary link to document our sources.

The S&T editors have rectified that with a new November 11 online article and a couple of PDF downloads, free reprints from their magazine articles. They say:

If your friends and family are worried about the impending disaster — supposedly based on an ancient Mayan prophecy — we have the stuff you need to tell them …

November 11, 2009 | The world won’t end on December 21, 2012, no matter what ancient Mayan prophecies might imply. Noted archaeoastronomer E. C. Krupp explains the cause of this mania in November’s Sky & Telescope. But this issue is no longer available on newsstands, so we’re making Krupp’s article available as a free download.

The link to the article is here: The Great 2012 Scare

You should be able to download the PDF’s for yourself. Should you find the link broken at some future point, just reply to this posting, let me know. I downloaded them for myself and any friends who might want them by e-mail (they’re in my ‘Articles’ folder, Alex). I’ll post the PDF’s myself.

Cheers!

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Debunking the “2012″ Myth

On November 13, Sony Pictures International is releasing a new doomsday movie, “2012“. It’s about yet another end-of-the-world, Chicken Little “prediction” of the ancient Mayan Calendar (which the Mayans were not actually predicting). The movie will no doubt scare a lot of superstitious or uninformed people, and may even (grin) scare off sales of the Sony Playstation:

from the Sony website

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Mystery Object Tears Star Apart?

Excerpted from the Sky&Telescope posting June 7, 2009, below.  We know that binary star groups sometimes consume one partner with cataclysmic results, so this article should be no surprise. Still, the idea of invisible black holes that can tear a star apart in 200 days is something that boggles the mind:

Update on Hubble Mystery Object

June 7, 2009
by Rachel Courtland, NewScientist.com

Remember the Hubble Mystery Object? In 2006 it steadily brightened, then steadily faded over the course of 200 days total, in a way that resembled no known type of variable object. Even its spectrum was inscrutable, leaving no sign of whether it was a flare on a very faint star in our own Milky Way or some enormous eruption billions of light-years distant.

What was it?
Now you don’t see it, now you do. Something truly in the middle of nowhere — apparently not even in a galaxy — brightened by at least 120 times during more than three months and then faded away.
K. Barbary and others

Now there’s a sign that it was the latter. And one new theory suggests that an odd, wandering, intergalactic black hole tore apart a star of unusual composition … Gaensicke and colleagues propose two scenarios that might explain the object. In one, a carbon-rich star swung too close to an intermediate-mass or heavyweight black hole, which pulled it apart. Some of the material made its way into the black hole, and some was blasted off in a flare that was seen from Earth as SCP 06F6.

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