APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

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APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by APOD Robot » Mon Jun 06, 2016 4:13 am

Image The Supernova and Cepheids of Spiral Galaxy UGC 9391

Explanation: What can this galaxy tell us about the expansion rate of the universe? Perhaps a lot because UGC 9391, featured, not only contains Cepheid variable stars (red circles) but also a recent Type Ia supernova (blue X). Both types of objects have standard brightnesses, with Cepheids typically being seen relatively nearby, while supernovas are seen much further away. Therefore, this spiral is important because it allows a calibration between the near and distant parts of our universe. Unexpectedly, a recent analysis of new Hubble data from UGC 9391 and several similar galaxies has bolstered previous indications that Cepheids and supernovas are expanding with the universe slightly faster than expected from expansion measurements of the early universe. Given the multiple successes of early universe concordance cosmology, astrophysicists are now vigorously speculating about possible reasons for this discrepancy. Candidate explanations range from the sensational, such as the inclusion of unusual cosmological components types such as phantom energy and dark radiation, to the mundane, including statistical flukes and underestimated sources of systematic errors. Numerous future observations are being planned to help resolve the conundrum.

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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by Ann » Mon Jun 06, 2016 5:01 am

I'm very glad that this spiral galaxy and the important research that has been done on two of its constituent kinds of stars is honored with an APOD.

The colors are very well-balanced. The Cepheids are not encircled in the large version of the picture, but I could memorize the star patterns where some of them are located, and then I could easily recognize them by their color and brightness in the large picture. Cepheids are fainter than the brightest blue and red stars in a starforming galaxy, and they are neutral or pale yellow in color, whereas other bright stars in their vicinity are usually either bluish or golden orange.

To my utterly amateur mind, it seems as if there is something systematic about the way the value of the Hubble constant and the rate of the acceleration of the universe has been revised up and down. The first discovery of the acceleration of the universe was made when two teams studied supernovas Type Ia in galaxies that are much too far away for any of their non-supernova constituent stars to be studied. Let's say this study was centered on the "teenage" era of the universe. The way I remember it, the two teams concluded that the universe was made up of 73% of 74% dark energy, plus dark matter and baryonic matter.

The next great studies of dark energy and the rate of the universe was carried out first by the WMAP spacecraft, which studied the cosmic microwave background, the baby era of the universe, and concluded that the universe is made up of 72.8% dark energy, plus dark matter and baryonic matter. After WMAP came Planck, whose study of the cosmic microwave background revised the strength of dark energy down to 68.3% of the universe.

But the new study is based of galaxies in a much later era of the universe, where the galaxies are close enough to have their Cepheid stars studied. The strength of dark energy and the rate of the acceleration of the universe is again revised upwards.

Could it be that dark energy is slowly, slowly gaining strength as the universe evolves? Alternatively, could it be that supernova studies, for whatever reason, gives a higher value for dark energy than studies of the cosmic microwave background? Or is the new study just more precise than previous ones, so that it arrives at a more correct value?

Questions, questions. And no answers. Well, I find this very interesting, at least!

Ann
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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by Boomer12k » Mon Jun 06, 2016 6:13 am

Ann wrote:I'm very glad that this spiral galaxy and the important research that has been done on two of its constituent kinds of stars is honored with an APOD.

The colors are very well-balanced. The Cepheids are not encircled in the large version of the picture, but I could memorize the star patterns where some of them are located, and then I could easily recognize them by their color and brightness in the large picture. Cepheids are fainter than the brightest blue and red stars in a starforming galaxy, and they are neutral or pale yellow in color, whereas other bright stars in their vicinity are usually either bluish or golden orange.

To my utterly amateur mind, it seems as if there is something systematic about the way the value of the Hubble constant and the rate of the acceleration of the universe has been revised up and down. The first discovery of the acceleration of the universe was made when two teams studied supernovas Type Ia in galaxies that are much too far away for any of their non-supernova constituent stars to be studied. Let's say this study was centered on the "teenage" era of the universe. The way I remember it, the two teams concluded that the universe was made up of 73% of 74% dark energy, plus dark matter and baryonic matter.

The next great studies of dark energy and the rate of the universe was carried out first by the WMAP spacecraft, which studied the cosmic microwave background, the baby era of the universe, and concluded that the universe is made up of 72.8% dark energy, plus dark matter and baryonic matter. After WMAP came Planck, whose study of the cosmic microwave background revised the strength of dark energy down to 68.3% of the universe.

But the new study is based of galaxies in a much later era of the universe, where the galaxies are close enough to have their Cepheid stars studied. The strength of dark energy and the rate of the acceleration of the universe is again revised upwards.

Could it be that dark energy is slowly, slowly gaining strength as the universe evolves? Alternatively, could it be that supernova studies, for whatever reason, gives a higher value for dark energy than studies of the cosmic microwave background? Or is the new study just more precise than previous ones, so that it arrives at a more correct value?

Questions, questions. And no answers. Well, I find this very interesting, at least!

Ann
Ann, nice observations... there MAY also be that the "standard candle" of Type 1a Supernova... are now considered....not so standard as thought... PLUS... new techniques, more sensitive equipment, like the new Interferometer... get new readings, thus, new data, totals, figures, and so, things appear to change. Science marches on...
I am sure the new space telescope will give us even some different data than Hubble. We will see more, learn more....
Also, maybe being closer, the Resolution is closer, and the situation clearer...

Nice night tonight, but I am too bushed, and it was a bit windy.
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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by neufer » Mon Jun 06, 2016 12:36 pm

http://arxiv.org/abs/1606.00634 wrote:
Reconciling Planck with the local value of H0 in extended parameter space
Eleonora Di Valentino, Alessandro Melchiorri, Joseph Silk (2 Jun 2016)

<<The recent determination of the local value of the Hubble constant by Riess et al, 2016 (hereafter R16) is now 3.3 sigma higher than the value derived from the most recent CMB anisotropy data provided by the Planck satellite in a LCDM model. Here we perform a combined analysis of the Planck and R16 results in an extended parameter space, varying simultaneously 12 cosmological parameters instead of the usual 6. We find that a phantom-like dark energy component, with effective equation of state w=−1.29 at 68 % c.l. can solve the current tension between the Planck dataset and the R16 prior in an extended ΛCDM scenario.>>
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PHANTOM:

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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by Zuben L. Genubi » Mon Jun 06, 2016 12:46 pm

What I would like to know is, if this data holds true, are there implications for the calculated age of the Universe? Wouldn't this suggest that the Universe is somewhat younger than currently believed?

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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by neufer » Mon Jun 06, 2016 1:35 pm

Zuben L. Genubi wrote:
What I would like to know is, if this data holds true, are there implications for the calculated age of the Universe? Wouldn't this suggest that the Universe is somewhat younger than currently believed?
About a billion years younger: http://asterisk.apod.com/viewtopic.php? ... 94#p258219
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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by Voltaire » Mon Jun 06, 2016 2:25 pm

I'm a complete astronomy novice, mainly here visiting the "pretty pictures," but when I noticed the circles and read the summary, I was suddenly grateful that machines help us look deep into the sky-- mainly because when I look where the circles are, or the blue crosshairs, my eye was not drawn to any of it by instinct-- only by the beauty of the brighter parts. Viva our machine overlords!

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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by geckzilla » Mon Jun 06, 2016 2:37 pm

Voltaire wrote:I'm a complete astronomy novice, mainly here visiting the "pretty pictures," but when I noticed the circles and read the summary, I was suddenly grateful that machines help us look deep into the sky-- mainly because when I look where the circles are, or the blue crosshairs, my eye was not drawn to any of it by instinct-- only by the beauty of the brighter parts. Viva our machine overlords!
They were likely picked out by human eyes looking at a series of frames. Cepheids stick out a bit better when they're flickering on and off. If you were able to see it zoomed up and as an animation, maybe you'd see them! I could be wrong, though. My searches for Cepheids in Hubble imagery have turned up empty for the most part.
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Re: APOD: The Supernova and Cepheids of Spiral... (2016 Jun 06)

Post by neufer » Mon Jun 06, 2016 3:13 pm

geckzilla wrote:
Voltaire wrote:
when I noticed the circles and read the summary, I was suddenly grateful that machines help us look deep into the sky-- mainly because when I look where the circles are, or the blue crosshairs, my eye was not drawn to any of it by instinct-- only by the beauty of the brighter parts. Viva our machine overlords!
They were likely picked out by eyes looking at a series of frames. Cepheids stick out a bit better when they're flickering on and off. If you were able to see it zoomed up and as an animation, maybe you'd see them! I could be wrong, though. My searches for Cepheids in Hubble imagery have turned up empty for the most part.
They were likely picked out by "our machine overlord's eyes" looking at a series of frames about every 4 days.
http://www.nasa.gov/mission_pages/hubble/science/star-v1.html wrote: <<NASA's Hubble Space Telescope has been trained on a single variable star that in 1923 altered the course of modern astronomy. V1 is a special class of pulsating star called a Cepheid variable that can be used to make reliable measurements of large cosmic distances.

The star goes by the inauspicious name of Hubble variable number one, or V1, and resides in the outer regions of the neighboring Andromeda galaxy, or M31. The star helped Hubble show that Andromeda was beyond our galaxy and settled the debate over the status of the spiral nebulae. Nearly 90 years later, V1 is in the spotlight again. Astronomers pointed Edwin Hubble's namesake, NASA's Hubble Space Telescope, at the star once again, in a symbolic tribute to the legendary astronomer's milestone observation.

Astronomers with the Space Telescope Science Institute's Hubble Heritage Project partnered with the American Association of Variable Star Observers (AAVSO) to study the star. AAVSO observers followed V1 for six months, producing a plot, or light curve, of the rhythmic rise and fall of the star's light. Based on this light curve, the Hubble Heritage team scheduled telescope time to capture images of the star.

"V1 is the most important star in the history of cosmology," says astronomer Dave Soderblom of the Space Telescope Science Institute (STScI) in Baltimore, Md., who proposed the V1 observations. "It's a landmark discovery that proved the universe is bigger and chock full of galaxies. I thought it would be nice for the Hubble telescope to look at this special star discovered by Hubble, the man."

But Hubble Heritage team member Max Mutchler of the STScI says that this observation is more than just a ceremonial nod to a famous astronomer. "This observation is a reminder that Cepheids are still relevant today," he explains. "Astronomers are using them to measure distances to galaxies much farther away than Andromeda. They are the first rung on the cosmic distance ladder."

The observations were still tricky, though. "The star's brightness has a gradual decline followed by a sharp spike upward, so if you're off by a day or two, you could miss it," Mutchler explains. Using the Wide Field Camera 3, the team made four observations in December 2010 and January 2011. "The Hubble telescope sees many more and much fainter stars in the field than Edwin Hubble saw, and many of them are some type of variable star," Mutchler says. "Their blinking makes the galaxy seem alive. The stars look like grains of sand, and many of them have never been seen before."

On the night of Oct. 5, 1923, Hubble began an observing run that lasted until the early hours of Oct. 6. Under poor viewing conditions, the astronomer made a 45-minute exposure that yielded three suspected novae, a class of exploding star. He wrote the letter "N," for nova, next to each of the three objects. Later, however, Hubble made a startling discovery when he compared the Oct. 5-6 plate with previous exposures of the novae. One of the so-called novae dimmed and brightened over a much shorter time period than seen in a typical nova. Taking out his marking pen, Hubble crossed out the "N" next to the newfound Cepheid variable and wrote "VAR," for variable, followed by an exclamation point.

By the end of 1924 Hubble had found 36 variable stars in Andromeda, 12 of which were Cepheids. Could Hubble ever have imagined that nearly 100 years later, technological advances would allow amateur astronomers to perform similar observations of V1 with small telescopes in their backyards? Or, could Hubble ever have dreamed that a space-based telescope that bears his name would continue his quest to precisely measure the universe's expansion rate?>>
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