#type ia supernova

[startswithabang]

Ask Ethan: What Could Solve The Cosmic Controversy Over The Expanding Universe?

“As you pointed out in several of your columns, the cosmic [distance] ladder and the study of CMBR gives incompatible values for the Hubble constant. What are the best explanations cosmologists have come with to reconcile them?”

If you had two independent ways to measure a property of the Universe, you’d really hope they agreed with one another. Well, the situation we have with the expanding Universe is extremely puzzling: we have about 10 ways to do it, and the answers all fall into two independent and mutually incompatible categories. Either you make the measurement of an early, relic signal that’s observable today, and you get a value of 67 km/s/Mpc, with an uncertainty of about 1%, or you measure a distant object whose emitted light comes directly to our eyes through the expanding Universe, and you get a value of 73 km/s/Mpc, with an uncertainty of about 2%. It’s looking increasingly unlikely that any one group is wrong, in which case, we absolutely require some new, exotic physics to explain it.

While many ideas abound, there are five of them that are eminently testable in the next decade or so. Here’s how we could solve the expanding Universe controversy in the best way possible: with more and better science!

[startswithabang]

These Are The 6 Different Ways To Make A Supernova

“Yet, if you cross a certain mass threshold, you overcome that quantum barrier, and that triggers a runaway fusion reaction, destroying the white dwarfs and leading to a different class of supernova: a thermal runaway supernova.

So, we've got core collapse supernovae and thermal runaway supernovae. Does that mean that there are only two classes?

Hardly. There's more than one way to make both a thermal runaway and a core collapse supernova, and each mechanism or method has properties that are wholly unique to it. Here are the six ways to make a supernova, starting with the least-massive trigger and going up from there.”

So, you’ve got a star, and you want to trigger a supernova with it? Great! Every star that ever gets made in the Universe has the possibility of going supernova. If your star is born with more than about 8 solar masses, it’s practically an inevitability that a supernova will ensue, and that it will be a core-collapse supernova at that. But there are four independent ways to make that happen, and only one of them is the conventional way you probably think about it. If your star has less than 8 solar masses, though, it ends its life in a white dwarf, but that’s not necessarily the end. White dwarfs can gain enough mass, through two different known mechanisms, to someday go supernova as well.

There are six different ways to make a supernova, and each one is spectacular. Which one is your favorite?

[startswithabang]

Why Cosmology's Expanding Universe Controversy Is An Even Bigger Problem Than You Realize

“The question of how quickly the Universe is expanding is one that has troubled astronomers and astrophysicists since we first realized that cosmic expansion was a necessity. While it's incredibly impressive that two completely independent methods yield answers that are close to within less than 10%, the fact that they don't agree with each other is troubling.

If the distance ladder group is in error, and the expansion rate is truly on the low end and near 67 km/s/Mpc, the Universe could fall into line. But if the cosmic microwave background group is mistaken, and the expansion rate is closer to 73 km/s/Mpc, we just may have a crisis in modern cosmology.

The Universe cannot have the dark matter density and initial fluctuations that such a value would imply. Until this puzzle is resolved, we must be open to the possibility that a cosmic revolution may be on the horizon.”

Ever since we first learned that the Universe was expanding, scientists have worked hard to measure just how fast that expansion rate is. From that, combined with what makes up the Universe, we can learn how old the Universe is and what it was like in the past, as well as what it’s fate will be in the future. Yet the two groups that make independent measurements of that rate, from the cosmic microwave background and the cosmic distance ladder, have gotten inconsistent results. If the distance ladder team has made a mistake, everything will be fine with cosmology. But if that team is right and the microwave background team is wrong, there should be a crisis coming.

Why is that? Come find out why the biggest controversy in modern cosmology might be an even bigger problem than almost everyone realizes!

[space--bot]

The Supernova and Cepheids of Spiral Galaxy UGC 9391

Image Credit: NASA, ESA, and A. Riess (STScI/JHU) et al.

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 farther 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.

Taken from NASA's Astronomy Picture of the Day Space--Bot is a computer program that searches for space images.

[customstoday]

Star racing out of Milky Way at blistering 2.6 million miles an hour

Star racing out of Milky Way at blistering 2.6 million miles an hour

FRANCE: A star is racing out of the Milky Way at a blistering 2.6 million miles an hour (4.2 million kilometers an hour), astronomers report Thursday in Science, making it the fastest moving star ever found. Most other hypervelocity stars, as these speedsters are known, have been flung outward by the enormous gravity of the Milky Way’s central black hole. This one, by contrast, was probably…

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[christinetheastrophysicist]

Gaia's First Supernova

Launched less than a year ago, the Gaia spacecraft has discovered its first supernova. At about 500 million lightyears away, Gaia14aaa resides in the galaxy SDSS J132102.26+453223.8. By repeatedly scanning the sky, Gaia was able to detect a difference in the galaxy's brightness over the course of one month. The Gaia team was able to identify Gaia14aaa as a Type Ia supernova by studying its spectrum.

Read more about the discovery and Gaia.

Image: Supernova Gaia14aaa and its host galaxy (Credit: M. Fraser/S. Hodgkin/L. Wyrzykowski/H. Campbell/N. Blagorodnova/Z. Kostrzewa-Rutkowska/Liverpool Telescope/SDSS)

[christinetheastrophysicist]

Unusual Supernova is Doubly Unusual for Being Perfectly Normal

August, 2011, saw the dazzling appearance of the closest and brightest Type Ia supernova since Type Ia’s were established as “standard candles” for measuring the expansion of the universe. The brilliant visitor, labeled SN 2011fe, was caught by the Palomar Transient Factory less than 12 hours after it exploded in the Pinwheel Galaxy in the Big Dipper.

Easy to see through binoculars, 2011fe was soon dubbed the Backyard Supernova. Major astronomical studies from the ground and from space followed close on its heels, recording its luminosity and colors as it rapidly brightened and then slowly faded away.

Read More.

[dendroica]

Kepler Supernova Remnant: Infrared and Iron (NASA, Chandra, 03/20/13) by NASA's Marshall Space Flight Center on Flickr.

This composite image shows Spitzer infrared emission in pink and Chandra X-ray emission from iron in blue. The infrared emission is very similar in shape and location to X-ray emission (not shown here) from material that was expelled by the giant star companion to the white dwarf before the latter exploded. This material forms a disk around the center of the explosion as shown in the labeled version. This composite figure also shows a remarkably large and puzzling concentration of iron on the left side of the center of the remnant but not the right. The authors speculate that the cause of this asymmetry might be the "shadow" in iron that was cast by the companion star, which blocked the ejection of material. Previously, theoretical work has suggested this shadowing is possible for Type Ia supernova remnants. Read entire caption/view more images: X-ray: NASA/CXC/NCSU/M.Burkey et al; Infrared: NASA/JPL-Caltech. Image credit: X-ray: NASA/CXC/NCSU/M.Burkey et al; Infrared: NASA/JPL-Caltech Caption credit: Harvard-Smithsonian Center for Astrophysics