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The Countdown, Episode 19 – Voyager Hokey Pokey, Mini-Supernovae, Mercury Meteorite?, Planck’s Map, Birth of Massive Stars

The views expressed are those of the author and are not necessarily those of Scientific American.


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5) Voyager Hokey Pokey

What is going on with Voyager 1? Two weeks ago, the American Geophysical Union, or AGU, announced the space probe had finally left our solar system, which is incredibly exciting. Except it’s not exactly true.

Voyager 1 and its twin Voyager 2 launched in 1977, checked out a couple planets, and then kept going. The spacecraft are currently on a mission to explore beyond the edges of the heliosphere, the magnetic bubble surrounding our solar system. As they travel, the probes are constantly bombarded by cosmic rays. And in August of last year, the intensity of the local cosmic rays hitting Voyager 1 dropped, replaced by interstellar ones.

The most recent paper suggests Voyager 1 has exited the heliosphere, inspiring the announcement about the probe’s escape from our solar system. But although the particle data may be suggestive, it’s not enough to prove Voyager 1 is gone. According to scientists involved with the mission, the probe has not registered the magnetic field changes they’d expect to see at the edge of our system. Voyager 1 hasn’t left quite yet—it’s just in a new region of the heliosphere.

4) Mini-Supernovae

Supernovae now come in a brand new category: Type Iax.

If the name didn’t give it away, a Type Iax supernovae is closely related to a Type Ia. Ia supernovae occur in binary systems where a white dwarf star orbits a companion star. The strong gravity of the dense white dwarf actually steals material away from its companion, until the dwarf gets too big and explodes. This distinctive explosion is about 5 billion times brighter than our sun. But astronomers have discovered 25 supernovae that are much dimmer than expected, with only a hundredth of a Type Ia’s brightness.

The newly named Type Iax supernovae probably occur when the companion star has already lost its outer layer of hydrogen, leaving only helium for the white dwarf to strip away. The different process leads to a different type of explosion, one the white dwarf might manage to survive.

There’s still a lot to learn about Type Iax supernovae, but they may be a third as common as Type Ia’s, so scientists have plenty of opportunities for further study. You can find out more in The Astrophysical Journal.

3) Mercury Meteorite

Did we find a piece of the planet Mercury buried in our own backyard? If so, it will be the first time on record.

University of Washington scientist Anthony Irving has been studying 35 green-colored meteorites (pdf) found in Morocco in 2012. The meteorites are 4.56 billion years old–older than the Earth itself.

And they’re low in iron, with the weakest magnetic intensity of any known rock. This seems to match up with what the Messenger spacecraft tells us about Mercury’s surface. Irving thinks the strange rocks were ejected from a hot, magma-covered body. But we won’t know for sure that body was Mercury, until we can bring back a sample from the tiny planet’s surface.

2) Planck’s Map

When telescopes peer into space, they’re not just looking across distances—they’re also looking back in time. And the Planck space telescope’s peek into the past has revealed our universe is older than we thought.

The Planck mission studies the Cosmic Microwave Background, or CMB, the radiation left over from the Big Bang. Temperature variations in the CMB can reveal important facts about our universe, such as when the Big Bang happened. And the Planck satellite is very sensitive to these variations—it can even detect changes of a millionth of a degree. Its measurements have created the most accurate map ever of the CMB.

The map contains so much information, cosmologists are still sorting through it. But it pretty much supports the current model of the universe, just with better data. For example, the map confirms the universe is lopsided. And suggests it’s 13.82 billion years old, 80 million years older than we thought. We also have more accurate numbers for how fast the universe is expanding, and for the ratio of matter to dark matter to dark energy.

1) Birth of Massive Stars

There are some incredibly massive stars out in the universe. The problem is, they shouldn’t exist.

In order to get larger, a star must pull in matter from its surroundings. But the bigger it gets, the more radiation it emits, pushing away the very material it needs to keep growing. This should make it impossible for any star to reach a status called high-mass, defined as eight times the mass of our own sun.

Yet these massive stars exist. To discover how they form, the Herschel Space Observatory focused on W3, a giant gas cloud 6200 light years away. W3 acts as a stellar nursery for both low- and high-mass stars. As the astronomers discovered, a community of older stars is key to the development of high-mass bodies. When young stars begin to grow within a cluster of older ones, the elders funnel material to the youngsters, allowing them to reach a more massive size. This type of environment, where young stars can continuously accumulate and confine new matter, is crucial to the growth process.

You can read more about the study in The Astrophysical Journal.

—Portions of the script above written by Sophie Bushwick & Eric R. Olson

[The text above is a modified transcript of the video.]

About the Author: Eric is multimedia journalist and producer who specializes in science and natural history. His work has appeared on the websites of Scientific American, Nature, Nature Medicine, Popular Science, Slate and The New York Times among many others. He is a former video producer & editor for Scientific American. Follow on Twitter @EricROlson.

The views expressed are those of the author and are not necessarily those of Scientific American.





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