Theory says there may be disk of dark matter at center of galaxy

Jun 16, 2014 by Peter Reuell
“We have some genuinely new ideas,” said Lisa Randall, the Frank B. Baird Jr. Professor of Science. “I’ll say from the start that we don’t know if they’re going to turn out to be right, but what’s interesting is that this opens the door to a whole class of ideas that haven’t been tested before, and potentially have a great deal of interesting impacts.” Credit: Rose Lincoln/Harvard Staff Photographer

Scientists widely accept that the extinction of the dinosaurs was triggered when a massive object smashed into Earth and touched off a global ice age that wiped out as many as three-quarters of all species. The question, however, is where that object originated.

Harvard physicists believe they may have the answer, and their theory may prompt scientists to re-evaluate the decades-old conventional wisdom about one of the most mysterious substances in the universe: dark matter.

Though the exact nature of dark matter remains unknown, physicists have been able to infer its existence based on the gravitational effect it exerts on ordinary matter. Though dark matter is otherwise believed to be non-interacting, theoretical physicists Lisa Randall, the Frank B. Baird Jr. Professor of Science, and Matthew Reece, assistant professor of physics, earlier this year suggested that a hypothetical type of dark matter could form a disk of material that runs through the center of the galaxy.

If the , as it orbited the center of the galaxy, were to move through that disk, they theorized that the gravitational effects from the dark matter might be enough to dislodge comets and other objects from what's known as the Oort Cloud and send them hurtling toward Earth.

"Those objects are only weakly gravitationally bound," Randall said. "With enough of a trigger, it's possible to dislodge objects from their current orbit. While some will go out of the solar system, others may come into the inner solar system, which increases the likelihood that they may hit the Earth."

The model described by Randall and Reece suggests that those oscillations occur approximately every 35 million years, a figure that is on par with evidence collected from impact craters suggesting that increases in meteor strikes occur over similar periods.

The extinction of the dinosaurs, however, is just one theory that will have to be re-examined if Randall and Reece's theory proves true.

"We have some genuinely new ideas," Randall said. "I'll say from the start that we don't know if they're going to turn out to be right, but what's interesting is that this opens the door to a whole class of ideas that haven't been tested before, and potentially have a great deal of interesting impacts."

Working with postdoctoral fellow Jakub Sholtz, Randall and Reece are also investigating whether the newly proposed form of dark matter may play a role in one of the largest mysteries in astrophysics: how the massive black holes at the centers of galaxies form.

"One possibility is that it may 'seed' black holes at the center of galaxies," she said. "This is a work in progress. It's an entirely new scenario we're working out, so I don't want to overstate anything, but it's a very interesting possibility."

Though the hypothesis adds additional complexity to a number of already-thorny questions about the nature of the universe, Randall believes it will be important to understand if a portion—even a relatively small portion—of dark matter behaves in unexpected ways.

Over the next several years, Randall said, the Gaia satellite, which was launched earlier this year by the European Space Agency, will perform a precise survey of the position and velocity of as many as a billion stars, giving scientists far greater insights into the shape of the galaxy and into the potential presence of a disk of dark matter.

"If you were to look at our world and assume there was only one type of particle, you'd be pretty wrong," Randall said. "I think it's definitely a worthwhile theory to explore, because even if this is only a small fraction of dark matter, there is six times more dark matter in the universe than ordinary matter. We care a lot about , and that's precisely because it has interactions. So if there is a small portion of dark matter that has those interactions, that may be what we should pay attention to, perhaps even more so than other ."

Explore further: Researchers suggest dark matter disk in Milky Way plane could signal rash of comet strikes on Earth

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arom
1 / 5 (5) Jun 16, 2014
Scientists widely accept that the extinction of the dinosaurs was triggered when a massive object smashed into Earth and touched off a global ice age that wiped out as many as three-quarters of all species. The question, however, is where that object originated.
Harvard physicists believe they may have the answer, and their theory may prompt scientists to re-evaluate the decades-old conventional wisdom about one of the most mysterious substances in the universe: dark matter…
"Those objects are only weakly gravitationally bound," Randall said. "With enough of a trigger, it's possible to dislodge objects from their current orbit. While some will go out of the solar system, others may come into the inner solar system, which increases the likelihood that they may hit the Earth."

Even the poor dinosaurs did not understand what going on; they might feel the mysterious dark matter which killed them all …
http://www.vacuum...14〈=en
Jantoo
1 / 5 (5) Jun 16, 2014
These ideas aren't that new, they're based on rather old observations (Johnson, Harnden 1997) and the positron signal was attributed to binary stars later. The ideas, that the Solar system is passing through dark matter clouds and IMO it just recently happened, as we are experiencing global warming period by now, followed with another typical phenomena.
Jantoo
1 / 5 (4) Jun 16, 2014
For example, whenever you appear inside of more dense vacuum, thickened with dark matter which pervades the space between particles, the massive bodies will become lighter and expanded - they will swell like the raising in the sugar solution. The Moon orbital path will gain the eccentricity and radius and the Earth will gain the rotational speed for to preserve momentum during it.
Mr Som-o
not rated yet Jun 17, 2014
"If the solar system, as it orbited the center of the galaxy, were to move through that disk, ..."

If this, if that, then maybe this or maybe that... sounds like a stretch to me, but, hey!, they got their funding.
George_Rajna
1 / 5 (2) Jun 17, 2014
Sterile Neutrino and Dark Matter: https://www.acade...k_Matter
antialias_physorg
not rated yet Jun 17, 2014
Now THAT is a researcher's desk in the image. Take note all you would-be scienmtists. (And those are only the papers worth keeping around for quick reference)
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
antialias_physorg
5 / 5 (2) Jun 17, 2014
The mainstream physics is not so bad business, if you know, how to do it.

You know what the chances are of winning such a prize as a scientist? You're better off buying lottery tickets.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
rockwolf1000
5 / 5 (2) Jun 17, 2014
I'm not sure about this theory but what I do know is Lisa Randall is a fox.

Intelligent and gorgeous. They should clone her.
Sikla
Jun 18, 2014
This comment has been removed by a moderator.
Benni
1 / 5 (1) Jun 22, 2014
Quoting the article:

"If the solar system, as it orbited the center of the galaxy, were to move through that disk"

A good explanation for why "dark matter" has never been discovered inside our solar system.

When the total force(s) of gravity inherent within the solar system are exactly proportionate to the total mass then there must be no "dark matter" present within our system. But if DM exists in isolated areas of the galaxy & for some reason does not mix with baryonic matter because it is matter not composed of an atomic shell structure, then the "disc" concept makes sense.
Torbjorn_Larsson_OM
5 / 5 (2) Jun 22, 2014
Speaking of over-stating, I'm disappointed with the otherwise excellent Randall here. Modern statistics (more fossils and use of autocorrelation) shows no periodicity, e.g no correlation with orbital galactic disk passages as with the impact record. So that is not "one theory that will have to be re-examined" because of this. [ http://www.pnas.o...full.pdf ]

The Chixculub impact was only an extinction trigger because a) it unluckily hit modern calciferous and sulfurous sediments and possibly because b) it was one among several environmental strains at the time. (E.g. followed closely the Deccan plateaus's volcanism.)
Torbjorn_Larsson_OM
5 / 5 (2) Jun 22, 2014
@Jantoo: Wrong! Wrong! Wrong! What are you, a Dunning-Kruger case?

- AGW is _Anthropic_ GW, the now well tested climate science main theory. Besides that, DM acts mostly gravitationally which is why even WIMPs hitting nuclei contribute little heat, so little that direct detection is difficult.

- Your claims of 'swelling' has no support from the references. E.g. the kilogram prototype's variation is believed to be due to cleaing difficulties.

- "Moon": They explicitly claimed that only Oort objects could be influenced, if that.

@Mr Som-o: Those were simple predictions. (Too simple, since they got one wrong, see my previous comment. Yes, such may be used to expand on potential importance. But it isn't explicitly wrong, and the funding agencies know the game.
MrPressure
Jun 29, 2014
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MrPressure
Jun 29, 2014
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