Astronomy

Rethinking the origin of cosmic rays

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The PAMELA instrument. Credit: Piergiorgio Picozza

New results from an Italian space-based experiment have astronomers puzzled about the origins of cosmic rays. Cosmic rays are charged particles — protons and other atomic nuclei — that are accelerated to near-light speeds and continue on through the universe. The Earth is awash in them, with dozens of cosmic rays passing through your body every second of every day. Until now, the prevailing explanation for their origin was that they are accelerated by the remnants of supernovae, the spectacular final moments of dying high-mass stars. However, evidence gathered by the exquisitely sensitive Italian space-based instrument, called PAMELA, suggests this is not the case. It seems that different types of particles are accelerated in different ways, contrary to what is expected if they are accelerated by the same source.

It’s another entry in the “We didn’t expect that” file, which is part of what science is all about. And theorists always like the extra business.

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Buckyballs in space

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Sounds like the title of a cheesy sci-fi movie, doesn’t it? Buckyballs (short for “buckminsterfullerenes”) are the largest molecules that we know of, and just last year they were discovered for the first time in space. Based on their properties, astronomers predicted that buckyballs would exist in certain environments in space and not in others. However, a group using the Spitzer Space Telescope has found precisely the opposite. This is why observation and experiment are so important in science.

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Never tell me the odds!

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The Pan-STARRS telescope in Hawaii discovered a record-breaking 19 asteroids in one night last January, two of which are projected to come close to the Earth at some point.

Even with all of these discoveries, it’s estimated we’re tracking only about 1% of the total number of Near Earth Objects (NEOs) in the solar system. To get an idea of the distribution of all the stuff zipping around out there, check this out (seriously).

A little scary perhaps, but at least it’s not this bad:

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Some galaxies grow like snowflakes

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Massive elliptical galaxy M87

Astronomers have found further evidence that some galaxies grow in a way similar to snowflakes. A snowflake grows by building up ice crystals around a tiny grain of dust in the atmosphere. Likewise, some galaxies start off as modest “seed” galaxies within a cluster and then build up by acquiring stars from other galaxies in the cluster. This brief computer simulation shows the process (the bright dots in the simulation are the luminous cores of galaxies; notice how the one in the center grows to enormous proportions by grabbing stars from the other galaxies).

The authors of the new study observed the massive elliptical galaxy, NGC 1407, also commonly known as M87. Their case relies on measurements of the proportion of heavy elements in M87’s stars as a function of where they are located in the galaxy. The stars in the outer part of the galaxy have a different chemical composition than stars near the core, so it’s likely the galaxy wasn’t built all at once, but from the inside out like a snowflake. Not a gentle, delicate snowflake mind you: M87 is the most massive galaxy in the local universe, with a powerful black hole-driven jet of particles shooting out of its core at near-light-speed.

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Possible baby planet discovered

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Astronomers may have spotted a baby planet around a star called T Cha, which is estimated to be 7 million years old — still in its diapers, compared to the 4.5-billion-year-old Sun. What makes this an unusual discovery is that it may be the first time astronomers have witnessed an individual planet in the process of forming. The evidence hinges on a suspicious gap in the dusty disk surrounding the newborn star, suggesting that some kind of object has formed and swept out the material in its orbit.

Astronomers have dubbed dusty planet-forming disks “proplyds,” short for “proto-planetary disks.” The Hubblecast video below shows astonishing images of several proplyds observed in the Orion Nebula.

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