Monday, August 1, 2011

Supernovae Updates (from Page)

_This used to be a page, but now has moved into this post_


Supernovae Updates

Welcome to the Supernovae Page at Astronomical Events! Here, I keep track of two supernovae, T Pyxidis which has faded some, and SN 2011dh in the Whirlpool Galaxy. That's faded too. 
 Most current picture (Lynn Hilborn)

There lays Messier 15 and its companion NGC 5194 (irregular galaxy on top), both probably the most well known galaxy in the night sky, aside from the Milky Way and Andromeda Galaxy. Yet, something peculiar occurred over the past few days May 31, 2011 to be exact.


“For the second time in six years, a star has exploded in the iconic Whirlpool Galaxy (Messier 51)” wrote Kelly Beatty from SkyandTelescope. If you look at the picture on the right, you'll notice a prominent red star in the lower-left of the picture in one of the beautifully adorned arms. This is about where this explosion is; and we have great news! This supernova will be in view for backyard observers everywhere, everyone with some type of telescope that is.

May 31, 2011 gave the first hint of some explosion in the lower-left of Messier 51, by French amateur astronomer Amédée Riou noticed an absent magnitude fourteen star in CCD images of the galaxy. It had been previously there, but then it had 'vanished.' Riou recorded this event the following evening and the result was the same. It was identified and the word was sent out to several astronomers June 1 for further research and explanation. French observer Stéphane Lamotte Bailey, noticed it the night after on digital images taken through his 8-inch telescope, images of Messier 51, that is. 

The supernova is clearly not at magnitude 19.5 anymore, despite the fact that it’s still too early to tell whether the supernova will brighten or fade. But, based on further research and investigation, astronomers are confident that this supernova is a type II supernova: the explosion of a single massive star whose core has abruptly collapsed. The Keck I telescope tells us that this explosion is racing earthward as Bradley Cenko from the University of California, Berkeley, says: “The shock wave has material moving at a variety of different speeds (typically faster farther out). The hydrogen that we see moving toward us at 17,600 km per second is probably a pretty good proxy for the fastest material in the outflow.”

So, SN 2011dh, the designated supernova’s official title, was a likely supergiant at magnitude 21.8 (extremely faint; the human eye can perceive to magnitude 6 and even that’s faint!), and had the mass of approximately 18-24 Suns as formulized by UC Berekely’s Weidong Li and Alex Filippenko. Actually, this is the third supernova to occur in the same arm of Messier 51 in seventeen years; six years ago, in 2005, another Type II event occurred, along with, in 1994, a somewhat brighter event.
“Supernova 2005cs was discovered on June 28th by amateur supernova hunter Wolfgang Kloehr of Schweinfurt, Germany, in a CCD image that he took with an 8-inch reflector.” ~SkyandTelescope
For those of who would like to observe this supernova in action, to locate the Messier 15: Messier 15 is approximately 31 million light-years away in the constellation Canes Venatici, high in the evening sky. SN 2011dh's J2000 coordinates (in Canes Venatici) are right ascension 13h 30m 5.1s, declination +47° 10′ 11″. It is positioned 2.3 arcminutes to the east and 1.5 arcminutes to the south of the Messier 15’s center, halfway between two bright star fields. The supernova should remain visible for a few weeks. 
“The supernova will be quite tricky to spot visually and you may need a good sized...telescope to spot it, but it will be a easy target for those interested in astro imaging.” ~UniverseToday

TOP: Before the explosion, BOTTOM: after the explosion. Credit: Stéphane Lamotte Bailey
Other photos from our gallery:

Jerry Lodriguss

More images are ascessible here, at these following links.

[Edited 6/4] T Pyxidis is now starting to return to its original magnitude. At around magnitude 8.2, its starting to grow fainter, but keep on viewing until it goes back to mag 15!
[Edited 5/25] T Pyxidis is still shining strong! At an average magnitude of 7.3 over the past few days, its period of 'explosion' will end soon, so view it now!!
To view a current viewing update on T Pyxidis, Please visit Sky&Telescopes daily viewing page of T Pyxidis.  (Its close to the bottom of the page). For a more precise viewing and history, visit AAVSO's page. Although its hard to view in the northern hemisphere, southern observes will get a great shot!
Detected by American astronomer Michael Linnolt in Hawaii on April 14 (technically April 14.2931), binary star T Pyxidis finally exploded again. After out-bursting last in December of 1966, forty-five years ago; T Pyxidis was very overdue (on exploding) and reached magnitude 8.4 on April 14, 2011 although in 1996-7 it reached 6.5, much brighter than its present state. Τo view this event; look for T Pyxidis in the dim constellation Pyxis, "the Mariner's compass box," east of Puppis and Canis Major. (America rarely is able to view the constellation, but the Southern Hemisphere is able to). Thanks to AAVSO (the American Association of Variable Star Observation) we are given the exact declination: -32 22 47.4 degrees and currently lies high in the sky after dusk in the south-southwest sky. 

Images from ground telescopes and the Hubble Space telescope; you can view the white dwarf surrounded in matter accumulated by the Sun-like star.

However, T Pyxidis' history is very interesting; needless to say its future is as well. The first explosion was observed in 1890; it continued to explode [around] every twenty years: again in 1902, 1920, 1944, and 1966-7. You can now see this was an extremely overdue out-bursting, and no-one knows why it stopped its explosions for the pause of forty-five years: 1966-7 to 2011. T Pyxidis will remain about at magnitude seven or eight for about two months (as recorded before), so viewing until June will be at its best. 

T Pyxidis is located approximately 3300 light-years from earth in the constellation Pyxis, hence the name 'Pyxidis.' It is a binary star system, which is comprised of a prominent white-dwarf, and a lesser Sun-like star orbiting around each other. (Most of the stars in the universe are not single; our Sun is actually very special: it has no companion). The reason why T Pyxidis periodically explodes is simple: the white dwarf has a strong gravitational pull on the Sun-like star and pulls matter (specifically hydrogen-rich gases) from the other resulting in a periodic thermonuclear explosion. This thermonuclear explosion was the one observed these past (including 2011) six times. 

An article entitled T Pyxidis Soon To Be A Type Ia Supernova, published January 5, 2010, tells us: "An extremely important unanswered question about such close binary stars is whether the mass receiving white dwarf continually grows in mass despite the nova explosions or decreases in mass because the nova explosions eject more mass from the white dwarf than it accumulates from the Sun-like star." Regularly viewed, the system is about magnitude 15.5 (the naked, human eye can detect up to magnitude six), and hasn't gone any brighter since 1966-7, until 2011. Thoughts are, is that this star (or these stars) will explode on itself (only one star of the system will) in the next ten millenia or so, resulting in T Pyxidis becoming a Type Ia Supernova. 

This summons the issue of being a threat to earth. Type Ia supernovae are extremely dramatic: "If the mass of the white dwarf in such a binary star system increases with time, then it will eventually reach the so-called Chandrasekhar Limit and will undergo instantaneous gravitational collapse resulting in an unimaginably powerful thermonuclear detonation which completely destroys the white dwarf and leaves no stellar remnant such as a pulsar (i.e., spinning neutron star) or a black hole." Space Daily tells us. (If this occurs,) because about twenty billion, billion, billion megatons of TNT would be released, if it would ever become a Type Ia supernova, earth would sure feel an effect of its explosion. T Pyxidis is closer to earth than astronomers had reasoned; the gamma radiation formed by such an explosion would fry earth. Astronomers are also watching Eta Carinae (7500 light years from earth) also. It is too a remnant that could do the same as T Pyxidis. But, this event (with T Pyxidis) won't or couln't happen until ten million years into the future. Edward Sion, researcher at Villanova University, tells us that "While we can relax, that is very short on astronomical and geological timescales." (Note: it is short on evolutionary/'big-bang theory' timescales, NOT creationism timescales). 

So, if whether T Pyxidis decides to explode in on itself, we don't know. We have observed many other supernovae explosions, but are a safe distance from earth. T Pyxidis is a remarkable binary!

To view T Pyxidis' explosion April 15th, you can view a quick double-image on this page. (Note: T Pyxidis explodes in the center, not at the top.) Below; how a Type Ia supernova forms.

[~Matthew Winter~]

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