Universe Today

Image credit: PPARC

A team of UK astronomers have discovered a new class of cannibalistic stars that may explain one of the mysteries surrounding the Big Bang. These stars formed shortly after the Big Bang but don’t contain any lithium -which astronomers predicted should be there. Astronomers believed that they must have misunderstood some essential aspect about the early universe, but this new research helps explain what happened to the lithium; it was destroyed by the star’s interaction with a partner star.

A team of UK astronomers announced this month the discovery of cannibalistic stars that explain one of the mysteries surrounding the Big Bang. The stars are almost as old as the Universe and they reveal what space was like in the very beginning.

The team from the Open University found that a group of 14-billion-year-old stars were all in a spin (literally) because of a nasty phase earlier in their lives. They were, in short, cannibalistic stars. The scientists’ discovery not only explains the origin of these mysterious stars, but also strengthens the Big Bang theory. The Big Bang is the name given to the rapid expansion of the Universe that marked the beginning of space and time; it explains the origin of the matter in the universe – including the matter which people are made of.

The stars under investigation are some of the oldest in the Universe. They formed out of gas clouds not long after the Big Bang. The OU team, led by Dr Sean Ryan, found that some of the stars that formed early in the life of the Universe were very unusual. They contained none of the metal lithium which astronomers believe is produced in the Big Bang.

Dr Ryan said:

“Observations showed that about 1 star in 20 contained no lithium, and some astronomers were concerned that this might mean we had misunderstood something important about the Big Bang and the origin of the Universe.”

New and more detailed observations of the peculiar stars were made with the 4.2-metre-diameter William Herschel Telescope. Using high precision equipment, the team found that most of the stars without lithium were spinning very fast. “Measuring the spin speed of stars is very difficult,” said Dr Ryan, “this is why no-one had seen this before. Most 14-billion-year-old stars do not spin very fast at all but these ones had up to 16 times as much spin energy as the Sun, our nearest star. We knew that the extra energy could come from only one source; another star.”

Dr Ulrich Kolb, an OU astronomer who specialises in interacting stars, explained what happened. “When these stars formed out of the gas clouds, not just one but two stars formed very near one another. Fatally, they were too close together for their own good. As they grew older, the smaller one captured the outer layers of the larger one. Very little now remains of what was the larger star; it has been cannibalised by its companion.”

The material captured by the companion carried orbital energy that was converted into spin energy. It was the discovery of the excessive spin energy that revealed the history of the objects.

The scientists believe that the lithium was destroyed in nuclear reactions shortly before the star-eating episode occurred.

Dr Ryan said:

“It’s rather a relief that we have discovered why the lithium-depleted stars are so different to most others. Knowing that the Big Bang theory tells us correctly how much lithium was produced gives us confidence that we really do understand much about the origin of the entire universe. Hydrogen that was formed in the Big Bang powers the Sun, which in turn provides energy to the Earth. It is also a vital component of pure water, which is so essential to life. Also we now know more about what happens when stars feed on one another.”

Using a technique called Doppler spectroscopy, the observations were made by measuring the speeds at which the stars are moving. This is similar to the way traffic speeds are measured on roads, but with stars clocking up many kilometres per second, not just a few kilometres per hour. The William Herschel Telescope on which the observations were made is one of the UK’s major telescopes. It is co-funded and operated by the Particle Physics and Astronomy Council (PPARC). It is located under the clear skies of the Canary Islands, where observing conditions are much better than in Great Britain. The telescope is shared with Dutch and Spanish astronomers. Dr Sean Ryan will be observing from the Canary Islands on 22-24 May.

Original Source: PPARC News Release

Image credit: NASA

The moon and five planets will appear close together in the night sky on Monday evening forming a rarely seen planetary conjunction. Look to the West, just after sunset. The planet Venus will be the brightest object in the sky, with Mars and Saturn below, and Jupiter above – Mercury will be visible just above the horizon, much dimmer than the rest. This will be the tightest conjunction of the planets in 40 years.

The Moon will join five visible planets to perform a seldom-seen celestial show on the evening of May 13.

To see the conjunction of the planets and moon, look in the western sky above the horizon just after sunset. Look for Venus, the brightest star in the group. Red Mars will be right below, and Jupiter, which appears white, will be topmost. Mercury is closest to the horizon, and Saturn is just below Mars.

“You’ll see just a sliver of the Moon, because it will be one day past new,” said Dr. E.M. Standish, an astronomer, also of JPL. “This will be the tightest conjunction for almost 40 years.”

A five-planet conjunction isn’t new; astronomers have been recording the phenomenon for over 3,500 years. Dr. Kevin Yau, an astronomer at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., has studied ancient Chinese astronomy texts to find out more about the conjunction.

“The Han Dynasty came to power in 605 BC,” Yau said. “One year later astronomers saw a five-planet conjunction gathered in the constellation Dongjing – what we would call Gemini.” This led to the ancient Chinese belief that the conjunction was an omen of change, but the alignment really has no effect on Earth or Earthlings.

Based upon good observing circumstances, 40 five-planet conjunction events may [vcm2]have been seen between the years 2000 BC and AD 2000. The next time these bodies will be grouped so closely together will be in September 2040.

“This alignment is a great opportunity to see the planets, since they are so easy to find in the sky,” he said.

As part of the imperial establishment in ancient China, an astronomical observatory was usually built inside the capital city of the time. Trained astronomers were appointed to keep a diligent watch of the sky day and night. The Chinese constellations have names that represent palaces and gardens, generals and ministers.

“Today, we are grateful that such detailed observational records were kept,” Yau said. “Our modern astronomical database goes back about five hundred years, which is relatively short in terms of astronomical timescales.” Astronomers often need to access data covering a longer time span in order to prove or disprove their theories such as the effect of the 11-year solar cycle on the Earth’s climate change, or predictions of when a comet will be visible from Earth.

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Original Source: NASA/JPL News Release

My wife and I went to see Spider-Man on Sunday, and so I thought I’d celebrate with a Hubble image of the Tarantula nebula (trust me, when you’ve got a six-month old, you celebrate the chance to see a movie).

To make this your computer screen’s background, click the image that matches your screen’s resolution, right-click “Set as Background”.

1024×768 (168K) – 800×600 (110K) – 640×480 (77K)

On a completely unrelated note, lots of you have a computer virus. I know this because I’m probably receiving hundreds of viruses a day from various readers. I can’t inform you individually because the virus disguises who actually sent it. Here’s a free virus scanner that I like.

Fraser Cain
Publisher, Universe Today

Image credit: NASA
NASA astronomers are studying a strange set of stars that spin much slower than expected. Normally, young stars spin quickly as its gravity pulls gas and dust into the centre, but a certain percentage of stars don’t – and astronomers don’t know why. There are several theories, but the most intriguing one is that planets have already formed around the star and are stealing momentum away from the parent star. NASA’s Origins mission, due for launch next year will help detect planet-forming disks around these young stars.

They don’t know why, but scientists say some adolescent stars rebel against the norm by spinning more slowly than their peers.

Normally, a young star gets smaller as its gravity pulls gas and dust in toward its center; the smaller the star gets, the faster it spins. But a scientist with NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and her colleagues have found that a significant percentage of adolescent stars do not spin faster as they shrink.

“A young, shrinking star should behave like a skater who pulls in her arms to make herself smaller and spin faster,” said Dr. Luisa Rebull, a staff scientist at JPL and the California Institute of Technology in Pasadena, which manages JPL for NASA. “We don’t know why some stars act differently, but we’d sure like to find out.”

Rebull offers four possible reasons for the odd behavior:

1 — It is simply a quirk of the process by which the stars formed.

2 — The stellar winds are carrying away the angular momentum, or spin. This is like a skater who extends her arms away from her body to slow down.

3 — The magnetic field generated by the young stars locks their rotation to the slower rotation rate of the dust and gas disks around them, disks that might eventually form planetary systems.

4 — The stars have already formed planets from their disks. In our solar system, the largest planet, Jupiter, has the most angular momentum, or spin. Maybe other planetary systems are operating the same way, with large planets “stealing the momentum” from the parent star.

The fourth possibility intrigues scientists with NASA’s Origins Program, which will hunt for Earthlike planets that might harbor life. If orbiting planets cause this odd stellar behavior, scientists might detect them by looking for this trait. Rebull is a scientist on a new Origins mission, the Space Infrared Telescope Facility. The mission will launch early next year on a mission which, as one of its many goals, will look for planet-forming disks around other stars. A subsequent Origins mission, the Space Interferometry Mission, will look for planets around young stars to investigate the planet hypothesis directly.

For this current research, Rebull and her team studied more than 9,000 stars in the Orion Nebula and the Christmas Tree Cluster, also known as NGC 2264. They observed about 500 stars with large spots. The spots are like Sunspots, but much bigger, covering a large portion of the star’s surface. As the stars rotate, the spots come into and out of view, causing tiny changes in the total light we see from the star. Some of these stars appear redder than expected. That might indicate they have dust disks around them, Rebull said, which could interact with the star to slow its rotation. This might support the third possible explanation.

The researchers used the .76-meter (30-inch) telescope at the McDonald Observatory in western Texas. They also incorporated data from the National Optical Astronomy Observatory, Tucson, Ariz. The research paper, which Rebull co-authored with Drs. Sidney Wolff and Steven Strom of the National Optical Astronomy Observatory, and Russell Makidon of the Space Telescope Science Institute, Baltimore, Md., will appear in the July 2002 issue of the Astronomical Journal.

Original Source: NASA/JPL News Release