Astronomers searching for potentially destructive Earth-crossing asteroids have revised the scale they use to communicate the risk of impact to the public. The Torino scale, which still goes from 0 (no chance of impact) to 10 (collision is certain) has the same classifications, but it's been rewritten to give the public a better idea of the risks associated with different space rocks. Instead of "meriting concern", lower risk objects now "merit attention by astronomers", explaining that astronomers will be making further observations.

Most objects in the Solar System have been resurfaced by collisions with asteroids, smaller rocks and comets. But Sedna, on the other hand, has spent its lifetime in the remote reaches of the Solar System, and probably hasn't had many impacts at all. It's only been weathered by cosmic rays and solar ultraviolet radiation. Astronomers think that Sedna started out icy, like Pluto and Charon, but was then baked for millennia, until the ice was transformed into a complex hydrocarbon similar to asphalt.

Are you liking astronomy but feeling unsure about how to take that first step? Have a friend showing a spark of interest in stars and you want to get them a small present? Look no further than Robin Scagell's book, Stargazing with a Telescope. In a concise, well pictured presentation, he describes the myriad of optical aids that bring our night time visage much closer and provides ready tricks for sizing up the relative benefits. Reading this book makes that first step less likely to be a mis-step.

The Milky Way - like all spiral galaxies - swings gracefully around a central super-massive black hole (SMBH). Astronomers have known for some time that a "fairy ring" of youthful blue-hot stars dance within a few light-years of its event horizon, but such stars should be very old and display expansive low-temperature red giant envelopes. Could there be a "fountain of youth" in the center of the Milky Way Galaxy?

Today NASA has 55 active mission control teams monitoring ongoing spacecraft and station missions - 13 associated with missions extended beyond original planning. Soon there may be seven less. By October of this year, we could be turning a deaf ear to data collected by one of the most successful NASA programs of all times. For even as Voyager 1 and 2 are poised to enter the interstellar realm, budget-minders in our nation's capital may have already sealed the fate on a pair of craft that could provide important information about our solar system - and beyond - for the next 15 years.

It's back. Yes, the Moon will figure prominently in this week's night sky, but it will put on a grand show as we have several occultations and a grazing event in store. We'll have plenty of opportunities to view new lunar features and catch a "shooting star" as we enter a very unusual meteoroid stream. So grab your telescopes and binoculars, because...

Here's what's up!

Since the beginning of astronomical observation, science has been viewing light on a curve. In a galaxy filled with thousands of eclipsing binary stars, we've refined our skills by measuring the brightness or intensity of so-called variable star as a function of time. The result is known as a "light curve". Through this type of study, we've discovered size, distance and orbital speed of stellar bodies and refined our ability to detect planetary bodies orbiting distant suns. Here on Earth, most of the time it's impossible for us to resolve such small objects even with the most powerful of telescopes, because their size is less than one pixel in the detector. But new research should let us determine the shape of an object... like a ringed planet, or an orbiting alien space station.

Wolf Rayat stars are some of the most massive and dangerous stars in the Universe, living out the final days before they explode as supernovae. And astronomers have found two of them orbiting one another at distances varying as close as the Sun is to Mars and as far as the Sun to Neptune. One star is 20 times the mass of the Sun, and the other 50 times the mass of the Sun, and they only take 7.9 years to complete their orbital cycle.

On its recent Titan flyby, Cassini took a series of detailed images of the Eastern edge of the bright Xanadu region. Cassini had only viewed this region with its synthetic aperture radar on a previous flyby, so this was an opportunity to image the area in infrared. In the centre of the image is a bright "island" completely surrounded by a dark "sea" of material. There is also an 80 km-wide (50 mile) impact crater, which has also filled up with this dark material.

If you think current telescopes are powerful, just you wait. A new class of observatories are in the works that could sport mirrors as large as 100 metres (328 feet) across, and have 40 times the observing power of the Hubble Space Telescope. A new study developed by a commission of European astronomers proposes that instruments this large could be built for approximately 1 billion Euros and take 10-15 years to construct.

"Sakurai's Object" is a white dwarf star that surprised astronomers when if flared brightly in 1996. They originally thought it was a common nova explosion, but further observations have uncovered that the star has actually reignited its stellar furnace. Computer simulations predicted that it could be possible for leftover hydrogen to sink into the star and drive a new flash of hydrogen fusion. If the simulation is correct, the star will stay bright until around the year 2200.

A vast looping structure 20 light-years across has been discovered near the heart of the Milky Way. The loop was found near a star forming region of our galaxy in the X-ray spectrum using the European Space Agency's XMM-Newton space telescope. Very high energy particles, usually only seen coming from pulsars or supernovae remnants, are streaming out of the object, so it could be working as a kind of natural particle accelerator.

Astronomers have discovered more than 150 planets orbiting distant stars, but only indirectly. Now an international team of researchers think they might have the first direct photograph of a planet orbiting another star. The image is of GQ Lupi, a young star located 400-500 light-years away. A dimmer object, potentially a planet, is located to the right of the star separated by 100 astronomical units (2.5 times the distance of the Sun to Pluto). Unfortunately, the astronomers haven't been able to determine the mass of the object, so they can't rule out that it might be a brown dwarf.

Scientists from the European Space Agency have strongly recommended that that the next scientific mission to Mars should be a rover. The ESA's EXOMARS rover would have a similar design to NASA's Spirit and Opportunity, but it would have a suite of instruments designed to search for evidence of past or present life. The rover would arrive on Mars in 2013 to begin the search for life. The ESA is also planning a mission for 2016 that would return samples from the Martian surface to Earth.

Gamma ray busts are the most powerful known explosions in the Universe, so if one went off in our galactic back yard, it could be bad for life on Earth. Researchers working with NASA think that a massive extinction hundreds of millions of years ago could have been started by such an explosion. If a GRB went off only 6,000 light-years away, it would strip away much of the Earth's ozone layer, and expose all surface life to deadly levels of ultraviolet radiation from the Sun.