Remembering Comet Shoemaker-Levy 9’s impact on Jupiter, 23 years ago this week

View of Jupiter from the Hubble Space Telescope after the impact of one of the largest fragments from Comet Shoemaker-Levy 9 in 1994. Photo Credit: NASA/STScI

Jupiter has been in the news a lot lately, with the Juno spacecraft continuing to send back stunning new images of the largest planet in the Solar System, including close-ups of the Great Red Spot. But something else happened at this time 23 years ago which captured astronomers’ and the public’s attention – a huge explosion in Jupiter’s atmosphere as a comet broke apart and the fragments collided with the planet, plummeting into the deep, thick atmosphere. The impacts and resulting “scars” were observed by telescopes around the world.

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Aliens or comets? Has the ‘Wow!’ signal mystery finally been solved?

Illustration showing the location of the “Wow!” signal in 1977, from the direction of a group of stars called Chi Sagittarii, and where the comets were located and monitored. Image Credit: The Center for Planetary Science

The search for evidence of extraterrestrial intelligence is one of the most exciting pursuits in astronomy today. Needless to say, there is a lot of controversy and debate surrounding the topic, partly due to an event which happened in 1977 – the famous “Wow!” signal. The brief but unusual radio transmission was detected only once, and the debate over its origin has continued to this day. Now, a group of astronomers are claiming to have finally solved the mystery. According to their new study just published, the signal came not from aliens, but comets.

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Mystery deepens: new study shows comets don’t explain odd dimming of Kepler’s ‘weird star’

The mystery surrounding KIC 8462852 may not involve comets after all, but it is still an enigma for astronomers. Image Credit: NASA/JPL-Caltech
The mystery surrounding KIC 8462852 may not involve comets after all, but it is still an enigma for astronomers. Image Credit: NASA/JPL-Caltech

As has been reported previously, there is something weird going on around a star which is a little over 1,400 light-years away. Astronomers are still baffled as to just what that is, and theories have ranged from a huge mass of comets to alien megastructures. Indeed, comets had become the leading explanation offered for the star’s odd behaviour, although that was really just the best of a bunch of ideas which all had flaws in them. Now, new research shows that the comet explanation is even less likely to be the answer, although the actual explanation is still as elusive as ever. Needless to say, this has resulted in a lot of discussion and debate in the past few months.

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2015 in review: a year of spectacular planetary missions and discoveries

High-resolution view of Pluto from New Horizons, showing rugged mountains and vast icy plains. Image Credit: NASA/JHUAPL/SwRI
High-resolution view of Pluto from New Horizons, showing rugged mountains and vast icy plains. Image Credit: NASA/JHUAPL/SwRI

To say that 2015 has been a great year for planetary exploration would be an understatement, with fantastic new discoveries from around the Solar System. From our first ever close-up look at Pluto and its moons, to more evidence for ancient lakes and rivers on Mars (and current briny streams) to weird bright spots and mountains on Ceres, to the continuing study of Saturn and its moons, notably Enceladus, to spectacular close-up views of a comet, it has indeed been quite a year.

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