Archive for the ‘Supernovae’ Category

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Two binocular comets and a small-scope supernova

March 31, 2017

Comet 41P brightens – photo by Hisayoshi Kato, from Sky & Tel’s 41P news page.

This is a shorty, just posting links to some current events for easy reference:

  • Comet 41P is bright and easily visible in binoculars from dark skies for most of the night from mid-northern latitudes (link).
  • Comet C/2017 E4 Lovejoy – the sixth comet discovered by Australian amateur Terry Lovejoy – is up just before dawn, near the ‘nose’ of Pegasus (link).
  • Supernova 2017cbv in the spiral galaxy NGC 5643 is visible in Lupus in the middle of the night – it’s a few degrees north and about an hour east of Omega Centauri, so it transits the meridian around 3 AM right now (link).

Go see some fun stuff.

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A hydrogen bomb detonated against your eyeball

November 28, 2013

…would deliver less energy to your retina than a supernova observed from a distance of one astronomical unit (AU; the distance from the Earth to the sun). How much less? From this XKCD What If:

Which of the following would be brighter, in terms of the amount of energy delivered to your retina:

A supernova, seen from as far away as the Sun is from the Earth, or

The detonation of a hydrogen bomb pressed against your eyeball?

Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is … by nine orders of magnitude.

That rocked me back on my heels. And it got me thinking: how far away would one have to be for a supernova to be only as bright as an h-bomb pressed against one’s eyeball?

H-Bomb

Radiated energy is subject to the inverse-square law, by which intensity of radiation is inversely proportional to the square of the distance. So the answer  to my question is the square root of billion in AU, which is 31,623 AU, which is almost precisely half a light year. (BTW, Google will translate AU to light years for you!)

So if you’re close enough to a supernova that the light takes six months to reach you, it will still be like being nuked at point-blank range.

How far away from a supernova do you need to be to be safe? According to this article, even at a distance of 3000 light years, a supernova could still wreck the ozone layer of an Earth-like world.

Even more suprisingly (to me, anyway), the 1006 and 1054 supernovae apparently left detectable chemical traces on Earth, despite being 7200 and 6500 light years away, respectively. From farther down in the same article:

Gamma rays from a supernova would induce a chemical reaction in the upper atmosphere converting molecular nitrogen into nitrogen oxides…. In 2009, elevated levels of nitrate ions were found in Antarctic ice, which coincided with the 1006 and 1054 supernovae.

Amazing. The 1054 supernova is near and dear to my heart. Its visible remnant, the Crab Nebula, is also catalogued as Messier 1. I have observed it dozens of times, most notably during my nearly-annual Messier Marathons. I had no idea that it had literally left its mark on Earth.

So, here’s something to be thankful for this Thanksgiving: there are no particularly good supernova candidates close enough to Earth to pose a serious threat. All of the contenders are not massive enough yet (if they’re white dwarfs) or too far away, or won’t blow for millennia, or some combination of the above. So you can tuck in with abandon. We could still be annihilated at any moment by death from space–just ask the folks in Chelyabinsk–but it probably won’t come in form of a supernova.

Hat tip to Mike.

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W00t!, W00t!, and Gaaaah!

May 15, 2011

No time for a real post, so here are a few things of note. Two good, one bad, as the title says.

W00t! #1: Want to have your mind blown? Check out this photographic sky survey “meant to reveal the entire night sky as if it rivaled the brightness of day.” Link.

W00t! #2: Want to see a star blow up? No a simulation, but a real-life supernova? You have two choices: be very patient, or use a telescope. The last 5 naked-eye supernovae in our galaxy were observed in the years 1006, 1054, 1181, 1572, and 1604, although supernova 1987a in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, was also naked-eye visible. Anyway, the point is that if you want to see the light of an exploding star with your own eyes, the best place to observe from is the eyepiece of a telescope. It’s not uncommon for a supernova to briefly outshine its host galaxy–that fact is worth pondering for a moment–and there are literally thousands of galaxies within reach of amateur telescopes, so even a modest telescope will show you supernovae in other galaxies on a semi-regular basis. A good site for keeping track of potentially observable supernovae is this one, which lists them by their visual magnitude (you may also find this limiting magnitude chart and this calculator useful to determine which supernovae are within reach of your instrument).

I bring this up because right now supernova 2011by is at magnitude 12.5 and may get brighter still. It has already been sighted in a 6in telescope (according to a post on Cloudy Nights) and is theoretically observable with even a 3- or 4-inch instrument under very good skies. It’s in the galaxy NGC 3972, which you can find using Stellarium, Cartes du Ciel, or any of a number of other free programs. Right now isn’t the best time to see it, thanks to the nearly-full moon, but hopefully it will still be reasonably bright at new-moon time near the end of the month.

Gaaaah!: Sorry to end on a bummer. The state of California is planning to close 70 state parks for budgetary reasons, and the Salton Sea State Recreation Area is one of those on the chopping block (story here). The Salton Sea is one of my favorite spots for camping and stargazing, and I’m seriously bummed that they’re going to shut down the park. I don’t know who to write to in order to fight this, and even if I did, I doubt if enough people would write to make a difference. One reason I go to the Salton Sea is that it’s a really nice campground that is never empty but never overflowing, either. So it’s a bit of a catch-22: the low traffic that draws me there in the first place pretty well ensures that the park will have few advocates. And I’m not even sure if fighting this would be a good thing. I know that the state can’t afford to keep all of the parks open, and maybe it’s better to shut down a low-traffic place like the Salton Sea park and let the property rest undisturbed*, than to shut down a high-traffic place and drive those folks to the Salton Sea and thereby increase the human footprint. I’ll think about it some more, and look around and see if there is anything to be done. In the meantime, I’m just sad.

*Normally, I’d worry that this was Step 1 in some nefarious plan to sell the land for commercial development, but the Salton Sea is such a commercial black hole that I doubt if such a plan could be put into place even if someone strongly desired it, and there’s no evidence that anyone does. It’s a lonely spot, and that’s the point–I like to get out and enjoy the emptiness.

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Astronomy Quote #1

October 28, 2009
crab nebula

M1, the Crab Nebula, the remnant of a star that exploded almost 1000 years ago. The heavy elements in the universe--including the ones in our bodies--were created and dispersed by exploding stars.

I know that the molecules in my body are traceable to phenomena in the cosmos. That makes me want to grab people in the street and say, “Have you heard this!?”
– Neil DeGrasse Tyson

 

Photo from APOD.