I got many comments on last week's Nibiru article from some very scared people. They needed a lot of reassuring that it was indeed a hoax and not real, and brought up many topics to discuss such as lens flares, hoaxes, double sun videos, rare sun mirages, and the status of the astronomical search for various versions of planet X. Why are astronomers so sure that Nibiru is nonsense?

Astronomers have discovered an adolescent protostar that is undergoing a rapid-fire succession of growth spurts. Evidence for this fitful youth is seen in a pair of intermittent jets streaming away from the star's poles.

Known as CARMA-7, the protostar is one of dozens of similar objects in the Serpens South star cluster, which is located approximately 1,400 light-years from Earth. This clutch of nascent stellar objects was first detected by and named for the Combined Array for Research in Millimeter-wave Astronomy (CARMA) telescope.

In the film version of "The Martian", the main character is trapped on the red planet and is forced to figure out how to grow food. He declares he is going to "science the s--t out of" the issue before instead engaging in regular old agriculture mixed with some engineering.

But science may soon help, researchers have discovered a gene that could open the door for space-based food production. Professor Peter Waterhouse, a plant geneticist at QUT, discovered the gene in the ancient Australian native tobacco plant Nicotiana benthamiana, known as Pitjuri to indigenous Aboriginals tribes, which has been used for decades as a model plant upon which to test viruses and vaccines.

Science fiction stories often suggest that ETs, and our future selves also, would be expansionist, colonizing the galaxy, taking over worlds, and so forth. It's natural enough, because we are expansionist ourselves. But it's actually quite easy to see that ETs simply can't have expanding populations, at least not for very long. Not if they are anything like us. 

It's a simple calculation which I covered before. If their doubling time is once a century, say (for  ease of calculation) - then in a thousand years, their population multiples by a little over a thousand (two to the power ten). So after two thousand years it has multiplied by a million, by a billion after three thousand years and so on.

Sorry, I accidentally made two copies of this article with different titles. And both have comments, so not sure what to do.

Unless you want to read the comments here, please visit the newer copy, Why ETs Won't Need to Colonize or Expand.

Jupiter's moon Europa is believed to possess a large salty ocean beneath its icy exterior, and that ocean, scientists say, has the potential to harbor life. Indeed, a mission recently suggested by NASA would visit the icy moon's surface to search for compounds that might be indicative of life. But where is the best place to look? New research by Caltech graduate student Patrick Fischer; Mike Brown, the Richard and Barbara Rosenberg Professor and Professor of Planetary Astronomy; and Kevin Hand, an astrobiologist and planetary scientist at JPL, suggests that it might be within the scarred, jumbled areas that make up Europa's so-called "chaos terrain."

Scientists have predicted a new phase of superionic ice, a special form of ice that could exist on Uranus and Neptune, thanks to a computer solution performed by a team of researchers at Princeton University. 

Durable crystals called zircons are used to date some of the earliest and most dramatic cataclysms of the solar system. One is the super-duty collision that ejected material from Earth to form the moon roughly 50 million years after Earth formed. Another is the late heavy bombardment, a wave of impacts that may have created hellish surface conditions on the young Earth, about 4 billion years ago.

Both events are accepted but unproven and the dates were estimated from zircons retrieved from the moon during NASA's Apollo voyages in the 1970s.

Can an astronaut throw a ball to the Earth? The answer is Yes, and No. Depends what you mean by hitting the Earth. First, if you throw a ball towards the Earth - yes it's traveling that way when you throw it. So, it is natural to think that no matter how slow it is, it would get there eventually. However, we aren't used to throwing things in orbit, and our intuitions can often lead us astray.

Within modern cosmology, the Big Bang marks the beginning of the universe and the creation of matter, space and time about 13.8 billion years ago. Since then, the visible structures of the cosmos have developed: billions of galaxies which bind gas, dust, stars and planets with gravity and host supermassive black holes in their centres. But how could these visible structures have formed from the universe's initial conditions?

To answer this question, theoretical astrophysicists carry out cosmological simulations. They transform their knowledge about the physical processes forming our universe into mathematical models and simulate the evolution of our universe on high-performance computers over billions of years.