Featured Research

from universities, journals, and other organizations

Stars Can Be Strange: Physicists Explore Strange Matter Hypothesis

Date:
December 21, 2006
Source:
Washington University in St. Louis
Summary:
According to the "Strange Matter Hypothesis," which gained popularity in the paranormal 1980's, nuclear matter, too, can be strange. The hypothesis suggests that small conglomerations of quarks, the infinitesimally tiny particles that attract by a strong nuclear force to form neutrons and protons in atoms, are the true ground state of matter. The theory has captivated particle physicists worldwide, including one of Washington University's own.

Strange Brew: Astronomers are debating whether the matter in these stars is composed of free quarks or crystals of sub-nuclear particles, rather than neutrons. If so, the stars would be strange quark stars, strange indeed.
Credit: Photo courtesy of NASA

According to the "Strange Matter Hypothesis," which gained popularity in the paranormal 1980's, nuclear matter, too, can be strange. The hypothesis suggests that small conglomerations of quarks, the infinitesimally tiny particles that attract by a strong nuclear force to form neutrons and protons in atoms, are the true ground state of matter. The theory has captivated particle physicists worldwide, including one of Washington University's own.

Mark Alford, Ph.D., Washington University in St. Louis assistant professor of physics in Arts & Sciences, and collaborators from MIT and the Lawrence Berkeley National Laboratory and Los Alamos National Laboratory, have used mathematical modeling to discover some properties of theoretical "strange stars," composed entirely of quark matter. Alford and his colleagues have found that under the right conditions the surface of a strange star could fragment into blobs of quark material called "strangelets," forming a rigid halo that contradicts traditional strange star models. This means that collapsed stars' nuclear leftovers, like the famously resplendent Crab Nebula, could be stranger than physicists think.

Alford and his colleagues recently published their findings in Physical Review D 73, 114016 (2006). The standard account of the dramatic death of a heavy star is that, after exploding in a supernova that rivals a whole galaxy in brightness, what is left is a "neutron star," a profoundly dense remnant, made mostly of neutrons, with a mass one and a half times that of our sun, crammed into an area with the radius of Saint Louis.

A strange star is an alternate ending of this story. If the Strange Matter Hypothesis is correct, then what is left behind is not a neutron star but an even denser strange star, made of quark matter rather than neutrons. And until recently, physicists thought that the two presented very different faces to the world.

A neutron star has a complicated multilayered surface. According to a description by M. Coleman Miller, Ph.D., of the University of Maryland, the deeper portions of the crust have voids that can be likened to Swiss cheese, overlaid by regions with sheets like lasagna, rods like spaghetti, and finally blobs like sprinklings of meatballs on the outside.

A strange star, on the other hand, was generally assumed to have a much simpler surface, consisting of a sharp interface between strange matter and the vacuum of surrounding space.

"A sharp interface between quark matter and the vacuum would have very different properties from the surface of a neutron star," noted Alford. But couldn't strange stars also have complicated surfaces? And if they did, could we even tell neutron stars and strange stars apart?

Kaleidoscopic aura of matter

Earlier this year, Alford's colleagues concocted a radical proposal. If blobs of quark matter (strangelets) have the right properties, maybe the strange star crust is something more like a kaleidoscopic aura of matter than a melon rind. "The idea was that the surface of a quark star might be as complicated as that of a neutron star, with a sort of crystalline halo or crust of strangelets," Alford explained. "If strangelets exist in reality, they will have a preferred size. If small strangelets are preferable, then big ones will split up into smaller ones. Conversely, if big strangelets are more stable, then small ones could fuse with other small ones--if they happened to bump in to each other--to make big ones."

If strangelets prefer to be big, then the strange star's surface will be the conventional simple sharp interface, with particles fused into the main body of the star. But if strangelets prefer to be small, then the surface will evaporate small strangelets to form a crystalline aura of strangelets floating in a sea of electrons.

His colleagues found that if surface tension along the interface and electrical forces within the charge distribution were neglected, then strangelets prefer to be small, and the strange star's surface indeed fragments into strangelets.

To follow, Alford joined the researchers in a more definitive investigation, addressing key parameters like surface tension and electrical forces that were neglected in the original study. Their results show that as long as the surface tension is below a low critical value, the large strangelets are indeed unstable to fragmentation and strange stars naturally come with complex strangelet crusts, analogous to those of neutron stars.

Their results will fuel the ongoing debate among astrophysicists about the nature and existence of strange stars. "A strange star believer would say: See, they showed that if the quark matter surface tension was low, then a strange star would have this strangelet crust, so perhaps some of the objects we think are neutron stars could actually be strange stars," Alford explained. "A strange star skeptic would say: Oh well, but the surface tension would have to be absurdly low for that to happen. These results basically show that for any reasonable value of the surface tension there is no crust, and strange stars are completely different."

Both conclusions are valid.

The strange star theory has its staunch defenders, but most physicists think it's merely an interesting, though improbable idea. But Alford and his colleagues are keeping its possibility afloat.

"There is still enough doubt about our understanding of these things," he said, "to leave room for speculation that there may be strange stars out there."


Story Source:

The above story is based on materials provided by Washington University in St. Louis. Note: Materials may be edited for content and length.


Cite This Page:

Washington University in St. Louis. "Stars Can Be Strange: Physicists Explore Strange Matter Hypothesis." ScienceDaily. ScienceDaily, 21 December 2006. <www.sciencedaily.com/releases/2006/12/061219095358.htm>.
Washington University in St. Louis. (2006, December 21). Stars Can Be Strange: Physicists Explore Strange Matter Hypothesis. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2006/12/061219095358.htm
Washington University in St. Louis. "Stars Can Be Strange: Physicists Explore Strange Matter Hypothesis." ScienceDaily. www.sciencedaily.com/releases/2006/12/061219095358.htm (accessed April 23, 2014).

Share This



More Space & Time News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA Chief Outlines Plan for Human Mission to Mars

NASA Chief Outlines Plan for Human Mission to Mars

AFP (Apr. 22, 2014) NASA administrator Charles Bolden, speaking at the 'Human to Mars Summit' in Washington, says that learning more about the Red Planet can help answer the 'fundamental question' of 'life beyond Earth'. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Nasa Gives You An Excuse to Post a Selfie on Earth Day

Nasa Gives You An Excuse to Post a Selfie on Earth Day

TheStreet (Apr. 22, 2014) NASA is inviting all social media users to take a selfie of themselves alongside nature and to post it to Twitter, Facebook, Flickr, Instagram, or Google Plus with the hashtag #globalselfie. NASA's goal is to crowd-source a collection of snapshots of the earth, ground-up, that will be used to create one "unique mosaic of the Blue Marble." This image will be available to all in May. Since this is probably one of the few times posting a selfie to Twitter won't be embarrassing, we suggest you give it a go for a good cause. Video provided by TheStreet
Powered by NewsLook.com
SpaceX's Dragon Spacecraft Captured by International Space Station

SpaceX's Dragon Spacecraft Captured by International Space Station

Reuters - US Online Video (Apr. 20, 2014) SpaceX's unmanned Dragon spacecraft makes a scheduled Easter Sunday rendezvous with the International Space Station. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Raw: Easter Morning Delivery for Space Station

Raw: Easter Morning Delivery for Space Station

AP (Apr. 20, 2014) Space station astronauts got a special Easter treat: a cargo ship full of supplies. The SpaceX company's cargo ship, Dragon, spent two days chasing the International Space Station following its launch from Cape Canaveral. (April 20) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins