Starship Asterisk*

neufer wrote:

Nitpicker wrote:
Imagine the event of a photon radiated from a star 10 light years away, 10 years ago. From our perspective, the photon arrives now with information of the event from 10 years ago. From the perspective of the photon, it is the event, moving through spacetime.

If an electron & positron collide to produce two quantum entangled photons
moving in opposite directions do they share the same perspective

Nitpicker wrote:
Imagine the event of a photon radiated from a star 10 light years away, 10 years ago. From our perspective, the photon arrives now with information of the event from 10 years ago. From the perspective of the photon, it is the event, moving through spacetime.

geckzilla wrote:

Chris Peterson wrote:

geckzilla wrote:Time dilation. How does it even work?

I recommend one of two approaches. Either don't think about it at all, or think about it quite hard. It's casual thinking about things like that which will mess you up.

Unfortunately I've taken the unrecommended approach and have a question that I don't suppose can be answered simply, but does time dilation affect light itself? For a particle of light, would no time seem to pass between the time it left one position and arrived at another?

Chris Peterson wrote:

geckzilla wrote:Time dilation. How does it even work?

I recommend one of two approaches. Either don't think about it at all, or think about it quite hard. It's casual thinking about things like that which will mess you up.

http://www.skyandtelescope.com/observing/highlights/Bright-Supernova-in-M82-241477661.html wrote:
Sky & Telescope: Supernova in M82 At Its Peak

<<Supernova 2014J in M82 has stopped brightening at about magnitude 10.5. The galaxy and supernova are visible in amateur telescopes in the northeast during evening, and higher late at night after the Moon sets.>>

BillBixby wrote:

Nitpicker wrote:

BillBixby wrote:
M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅,MMXIV

A worthy effort. Personally, I'd cheat be creative and "double-bar a 24", viz:

Code: Select all

====
XXIVMMXIV

I like it, very much. Is it acknowledged usage or inspired?

Nitpicker wrote:

BillBixby wrote:
M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅,MMXIV

A worthy effort. Personally, I'd cheat be creative and "double-bar a 24", viz:

Code: Select all

====
XXIVMMXIV

Nitpicker wrote:A worthy effort. Personally, I'd cheat be creative and "double-bar a 24", viz:

Code: Select all

====
XXIVMMXIV

BillBixby wrote:
M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅, M̅ M̅ M̅,M̅ M̅ M̅,MMXIV

====
XXIVMMXIV

rstevenson wrote:

geckzilla wrote:Wait, Rob. Where are you trying to go in 20 years at .999999999999 c?

Remember, I'd get to M82 in 20 of my years in the ship, but back here on Earth, you stick-in-the-muds will experience about 12 million years. If M82 turns out to be boring, I'll come back in another 20 years (ignoring the humungous accelerations and decelerations involved, just to keep things simple) and we can all catch up on who won all the Super Bowls I missed. Then I'll sit down to watch Super Bowl 24002014. (I leave as a challenge for the reader converting that to Roman Numerals.)

Rob

BDanielMayfield wrote:Thank you Ann and Nitpicker for those very helpful posts.

Ann, that article about the maximum magnitudes that type Ia Supernova can display was interesting. So these “standard candles” have some variability, but it’s reassuring that the variability wasn’t too large. The main conclusion of that paper was that, depending on the White Dwarf progenitor’s metallicity, a Ia SN can vary by 0.2 or at most 0.3 magnitudes.

Nitpicker, armed with your info that a mag. 10 object might just possibly be seen in my binos I think I’m going to alter my strategy for seeing this SN. I need to “phone a friend” who has a small telescope. Tonight I have a rare good weather window and if we can find SN 2014J in a telescope first finding it in binoculars should then be a little easier.

Bruce

BDanielMayfield wrote:

Nitpicker wrote:

BDanielMayfield wrote:Since it is expected to brighten for another two weeks, and since a supernova can breifly out-shine an entire galaxy, how bright can we expect this to become? Will this become a naked eye object?

According to what I have just read about Normal Type Ia supernovae, they all have an absolute magnitude of around -19.3, meaning that this one will have an apparent magnitude of about +8.5. So, visible in binoculars, but not to the unaided eye.

8.5 = -19.3 - 5 (1- log10[3,700,000pc])

Edit: this formula is not particularly accurate for objects beyond the Milky Way.

Nitpicker, thank you for that answer, which appeals to my mathematical side. So then the formula for apparent magnitude, given distance and absolute magnitude, would be:

M(app) = M(abs)-5*(1 – log10[D]), with distance in parsecs, and not taking any reddening factors into account.

Reddening must be quite strong in the exploding cigar though as shown by the infrared image Ann posted. One estimate I read mentioned 10.1 as a predicted maximum for SN 2014J.

Please excuse my ignorance of something that I ought to know, but at a fairly dark site what might the limits of a pair of 10x50 binoculars be?

geckzilla wrote:There's dust in M82, sure, but all this talk about it being super reddened seems unfounded. It's possible that it's at the periphery of the galaxy with a minimal amount of dust surrounding it. Until some measurements and analysis from someone experienced with such things are done it doesn't make sense to continue with this assumption.

geckzilla wrote:
<<There's dust in M82, sure, but all this talk about it being super reddened seems unfounded. It's possible that it's at the periphery of the galaxy with a minimal amount of dust surrounding it. Until some measurements and analysis from someone experienced with such things are done it doesn't make sense to continue with this assumption.>>

http://astrobob.areavoices.com/2014/01/25/m82-supernova-2014j-update-see-it-live-this-afternoon/ wrote:
M82 supernova 2014J update
Astrobob, January 25, 2014

<<The recent bright supernova SN 2014J discovered in the M82, the Cigar Galaxy, earlier this week has brightened up to magnitude 10.5 by some estimates. While I saw it last night at 11.5, I’m not complaining. Beginning and amateur astronomers the world over have been out braving the cold to get a look at this stellar beacon.

Lots more data on the supernova has been pouring in. Here’s what we know so far:

* SN 2014J is a Type Ia-HV supernova. HV stands for high-velocity and indicates that explosive gases have been rushing outward from the obliterated star at exceptional speeds. Early measurements on Jan. 22 clocked clouds of gas at over 20,000 km/sec.

* Astronomers estimate it was discovered about a week before maximum brightness. That would indicate a peak on or around Jan. 29.

* SN 2014J is “highly reddened”, meaning that there is a great deal of dust in the host galaxy it has to shine through for its light to reach us. Without reddening, the explosion would be even brighter.

* White dwarf stars – one of which was the progenitor of this M82 supernova – are typically made of carbon and oxygen, the waste products left by the fusion of hydrogen and helium during the star’s lifetime. Once a star becomes a white dwarf it’s done fusing elements, so it twiddles its thumbs cooling off over the next trillion years.

BUT … when it explodes as a supernova, waste carbon and oxygen fuse in the fury of heat and pressure to create a new element, silicon. That’s exactly what astronomers are seeing now in SN 2014J’s spectrum, a map of the star’s light made with a spectrograph. Spectrographs spread out a star’s light to “fingerprint” the elements of which it’s composed. Silicon is also produced “naturally” by fusion in the cores of supergiant stars, some of which can explode as Type II supernovae.

Silicon combined with oxygen is the most common compound in Earth’s crust. Next time you admire an agate or feel the sand between your toes, look up and thank a supernova.>>

BDanielMayfield wrote:
Personally, being flippant, I don’t give a flying flip about the “big rip”.

Nitpicker wrote:

BDanielMayfield wrote:Since it is expected to brighten for another two weeks, and since a supernova can breifly out-shine an entire galaxy, how bright can we expect this to become? Will this become a naked eye object?

According to what I have just read about Normal Type Ia supernovae, they all have an absolute magnitude of around -19.3, meaning that this one will have an apparent magnitude of about +8.5. So, visible in binoculars, but not to the unaided eye.

8.5 = -19.3 - 5 (1- log10[3,700,000pc])

Edit: this formula is not particularly accurate for objects beyond the Milky Way.

Dirty Harry: "A man’s got to know his limitations.”

Chris Peterson wrote:

Anthony Barreiro wrote:
Given that the universe is currently understood to be less than 14 billion years old, and we don't have a clue what 69.3% of the stuff in the universe ("dark energy") is, I don't see how one could be at all confident predicting what's going to happen when the universe is millions of times older.

We're pretty sure now that the universe will keep expanding
but we don't know if the "Big Rip" will occur:

http://en.wikipedia.org/wiki/Big_Rip wrote:

[img3="The Phantom is the 21st in a line of crimefighters that originated in 1536,
when the father of British sailor Christopher Walker was killed during a
pirate attack. Swearing an oath on the skull of his father's murderer to
fight evil, Christopher started the legacy of the Phantom that would be
passed from father to son, leaving people to give the mysterious figure
nicknames such as "The Ghost Who Walks", "The Man Who Cannot Die"
and "Guardian of the Eastern Dark", believing him to be immortal."]http://upload.wikimedia.org/wikipedia/e ... omics2.jpg[/img3]

<<The Big Rip is a cosmological hypothesis first published in 2003, about the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, is progressively torn apart by the expansion of the universe at a certain time in the future. According to the hypothesis, the scale factor of the universe and with it all distances in the universe will become infinite at a finite time in the future.

The hypothesis relies crucially on the type of dark energy in the universe. The key value is the equation of state parameter w, the ratio between the dark energy pressure and its energy density. At w < −1, the universe will eventually be pulled apart. Such energy is called phantom energy, an extreme form of quintessence. A universe dominated by phantom energy expands at an ever increasing rate. However, this implies that the size of the observable universe is continually shrinking; the distance to the edge of the observable universe which is moving away at the speed of light from any point moves ever closer. When the size of the observable universe becomes smaller than any particular structure, no interaction by any of the fundamental forces (gravitational, electromagnetic, weak, or strong) can occur between the most remote parts of the structure. When these interactions become impossible, the structure is "ripped apart". The model implies that after a finite time there will be a final singularity, called the "Big Rip", in which all distances diverge to infinite values.

According to the latest cosmological data available, the uncertainties are still too large to discriminate among the three cases w < −1, w = −1, and w > −1.>>

Anthony Barreiro wrote:Given that the universe is currently understood to be less than 14 billion years old, and we don't have a clue what 69.3% of the stuff in the universe ("dark energy") is, I don't see how one could be at all confident predicting what's going to happen when the universe is millions of times older.

If there were cosmologists somewhere in the universe more than five billion years ago, when the universe was smaller and denser and the expansion of the universe is believed to have been decelerating, they would have been entirely correct to extrapolate to exactly the sort of big crunch that gives Ann the heebie-jeebies.

Who knows what our inconceivably remote future may hold?

Chris Peterson wrote: The evidence for continued expansion is very strong. However, we should know by simple direct observation within a few quadrillion years, so lets keep this thread open.