Sunday, January 11, 2015
A faint but beautiful comet passed by the Earth recently, and the accompanying picture shows you why so many of us love observing these icy visitors from deep space.
Called Comet Lovejoy (after its discoverer, Australian astronomy hobbyist, Terry Lovejoy), the comet passed closest to Earth on Jan. 7th. It wasn't that close -- 44 million miles away. That's why you really need a telescope to see the comet well.
But in a telescope, as you can see in our image, made by Austrian astro-photographer Gerald Rhemann, a beautiful coma and tail have already formed. (As always, click on the picture to see a bigger version.)
Comets are chunks of ice (with dust frozen within them) left over from the formation of our solar system. Comet Lovejoy is estimated to be about 2 to 3 miles in diameter. But when the ice comes nearer to the Sun, as Comet Lovejoy is doing until it rounds the Sun January 30th, the Sun's heat and wind evaporates the comet's ice and releases the dust that has been locked up inside it for billions of years.
As a result, a cloud of evaporated material form around the comet. Called a "coma," the cloud around Lovejoy is already about 400,000 miles in diameter!
The Sun's energy and particles push material away from the coma, producing the long and twisting tail we see, stretching for millions of miles, always pointing opposite the Sun. The tail of the comet is very tenuous -- astronomers like to say that a "comet's tail is the closest thing to nothing that something can be and still be something."
After Comet Lovejoy leaves our neighborhood, we estimate it won't return to the inner solar system for more than 8,000 years. So enjoy it now. You can do a Google image search and see pictures from many other astronomical photographers around the globe. (Just to avoid confusion, we should mention that this is the fifth comet Mr. Lovejoy has discovered, and so there were other Comet Lovejoy's in the past. The official nerdy name for this comet is C/2014 Q2.)
If you have good binoculars or a telescope, observing instructions can be found at:
Thursday, January 1, 2015
Happy 2015, which is likely to be remembered in astronomy circles as the year we finally get close-up and personal with Pluto.
Nine years after its launch, the New Horizons spacecraft is "waking up" and getting ready for its encounter with distant Pluto this coming July. The intrepid little spacecraft has traveled almost 3 thousand million miles since its 2006 launch. It is so far away that its radio signals, moving at the speed of light, take 4 and a half hours to get to Earth.
(This dramatic time delay will help you understand why Pluto is hard to see, even through the Hubble Space Telescope, and why astronomers are very excited that we will at last have a probe that can take detailed pictures as it flies by Pluto.)
If you are still confused about Pluto's status (why it got kicked out of the club of regular planets), you can read the background story I wrote at this PBS website:
The only thing that has changed since I wrote that piece is that we now know that the dwarf planet called Eris is not bigger than Pluto, but the same size.
Another member of our solar system that got reclassified as a dwarf planet is the largest object in the asteroid belt, Ceres. To make 2015 more fun, the Dawn spacecraft will have a close encounter with Ceres in March and go into orbit around it, also giving us close-up images for the first time.
I am about to start teaching Astronomy 10A, my "Planets for Tourists" class at Foothill College and we will be paying special attention to Pluto and Ceres as their visitors approach them throughout the spring. I'll have more information on this blog too, as we learn more.
And for those of you who are near the San Francisco Bay Area, you are invited to a free lecture by Dr. Mark Showalter (who discovered two of the five moons of Pluto) at Foothill College Wed., Jan. 28, 2015, at 7 pm in our Smithwick Theater. If you live somewhere else, we will have the lecture up on YouTube on the Silicon Valley Astronomy Lectures channel after a few weeks:
2015 is also the International Year of Light and the 100th anniversary of the completion of Einstein's General Theory of Relativity. Both of these -- light and relativity -- are important to our understanding of the universe, so we astronomers will be happily joining in both celebrations. Perhaps you will too, as events are announced.
Here's wishing you a good new year from the old Astronomy Professor who keeps this blog.