Wednesday, July 30, 2014
I would like to invite all of you who live in or near the San Francisco area to a very special event this Sunday, at the Hyatt Regency Hotel near the San Francisco Airport, in the town of Burlingame. I will be moderating an afternoon discussion with three of my favorite astronomers (all excellent public speakers.)
Our topic will be "Beyond Earth: Planets, Life, and Intelligence in the Cosmos" and we will discuss the search for planets around other stars, for life on the worlds in our own solar system, and for intelligent life elsewhere in the universe. Geoff Marcy is considered the foremost planet hunter on our planet, having discovered more planets orbiting other stars than any other human being. Jill Tarter has headed the search for intelligent radio signals from ET for many years, and is the scientist whom Jody Foster was playing in the film "Contact." Chris McKay is one of the top Mars experts in the world and explores places on Earth that most resemble Mars.
The program is sponsored by the non-profit Astronomical Society of the Pacific, which is celebrating its 125th anniversary this year. The illustrated talks and panel will go from 1:30 to 5:30 pm at the Hyatt Hotel, 1333 Bayshore Highway, Burlingame, CA 94010. It's all free and open to the public, but the sponsors hope each attendee will make a donation of $10 to help pay for the expenses at the hotel. We expect big crowds, so come a little early to get a seat.
For more information and to RSVP, go tohttp://www.astrosociety.org/universe2014
With almost 2,000 planets now known to orbit other stars, and with many stars having more than one planet (just like our Sun does), this is the time that topics that seemed like science fiction only a few years ago are becoming an exciting part of science. Hear the latest from those at the forefront of this work.
If you know people living near San Francisco who might be interested, perhaps you can help me by sending this information on to them.
Sunday, July 20, 2014
On Wednesday, August 6, the European spacecraft Rosetta is going to have a close encounter of the best kind with a comet (a chunk of cosmic ice mixed with dirt.) It's called Comet 67P (the P stands for periodic comet, meaning it comes around again and again every six and a half years.) Its more informal name is Comet Churyumov–Gerasimenko, after the two astronomers who discovered it on a 1969 photograph.
In mid-July when our photo was taken, the spacecraft was still more than 7000 miles from the comet, but it was already becoming clearer in the camera. And, as you can see, 67P/C-G is weird looking. Instrument project manager project manager Carsten Güttler said,“The images faintly remind me of a rubber ducky with a body and a head."
What could cause the icy body of this comet, which is roughly two and a half miles across, to look like this. One possibility is that it is really two comets stuck together, something we have seen in other comets (such as 8P and 103P). Or maybe it was one comet that broke apart into pieces when it got too close to the gravity pull of a big planet like Jupiter, and this odd fragment is all that's left.
Another possibility is that early in its life the comet got hit by other chunks of cosmic ice or rock, carving out big pieces of it and leaving great rounded valleys behind.
We should learn more when we get closer to this ancient icy visitor, and especially when part of Rosetta attempts a landing. Stay tuned.
In the meantime, here is a great animation of the images from this past week, showing the comet spinning in the majestic darkness of
Sunday, July 13, 2014
An international team of astronomers recently reported a wonderfully strange discovery. They found the faint, cold "corpse" of a dead star, not by detecting any light from it, but through its gravity grip on another star corpse with which it shares a system. It's quite a story!
To follow it, we need to take a brief excursion into the gruesome deaths of stars. All stars collapse at the end of their lives, but stars with different amounts of mass (stuff) die differently. Less massive stars (like our Sun) eventually die by collapsing into a ball not much bigger than a planet -- such a white-hot but tiny corpse is called a "white dwarf." They start out as really hot, but cool off as they shine away their light and heat into the darkness of space.
More massive stars have a more complicated death in store for them. They die in a sudden event, where the core of the star collapses catastrophically, while the rest of the star blows up in a giant explosion called a "supernova." We have discussed such explosion in several posts.
What interests us today, however, is the tiny core of the star which is super-squozen (that's a technical term!) by the star's death. It's typically not much bigger than your average suburban town, and called a "neutron star" -- because in it all the atoms lose their identity and become neutrons.
Such a neutron star, surrounded by an "atmosphere" of materials from the messy explosion of the rest of the star, can sometimes be detected by faint pulses of radio waves it gives off, and is then called a "pulsar." (A watch company "borrowed" that name, but we astronomers had it first.)
So now here's the discovery. Astronomers using radio telescopes first discovered a pulsar in the constellation Aquarius, indicating that a neutron star was revealing itself to us. But the pulsar showed signs of wobbling, as if something with strong gravity was orbiting around it and pulling on it. Careful measurements reveal that the orbiting object is a white dwarf, and it takes only two and a half days to revolve around the neutron star. (Remember that Earth takes 365 days to go around the Sun, so these two star corpses are in an intimately close dance.)
To their amazement, when other astronomers tried to find the light or heat of the white dwarf companion, they COULDN'T -- not even with the biggest telescopes. That white dwarf must be so old that it has cooled down below the level where we can find it (at its distance of about 900 light years.) This makes it the coldest, dimmest star corpse ever found. If you are into star corpses, and we astronomers really are -- this is a big deal. It's remarkable that with today's technology, we can know this white dwarf is there not by its light, not by its heat, but just by its pull on another dead star nearby.
Note: Our image is just a painting, not any kind of photograph. It shows the pulsar on the left (with two beams of radio waves coming from it) and the white dwarf on the right. Although we can see light coming from the white dwarf in the painting, in real life the star is so faint and far away, no light from it is detectable with today's instruments.
Friday, July 4, 2014
For those of you who don't get to see fireworks today (July 4), here is an image of cosmic fireworks for your enjoyment. The glowing ring on our picture (taken with the Hubble Space Telescope) shows material ejected long ago from a star whose total explosion we saw in 1987. Recently, earlier debris from the star has been hit by the fastest moving material from the star's final explosion. The shock of collision has set knots of thicker material in the ring to glow like a necklace of sparklers.
The dramatic explosion at the end of the life of a star is called a "supernova," and this particular supernova is located in one of our closest neighbor galaxies, the Large Magellanic Cloud, about 168,000 light years away. We wish it were closer, but a visible supernova is a rare event. This was actually the first supernova explosion we have been treated to since the invention of the telescope in 1609-1610. It's been given the extremely clever name Supernova 1987A (the first such explosion seen in 1987.)
The huge star whose explosion we saw in 1987 had been losing some of its mass in earlier periods of its life and was surrounded by a cloud of its own debris. Later a wind of hot particles had blown from the star as it went through a different stage of its development. That wind had made a cavity in the gas around the star.
Now the material from the star's actual explosion, which has been moving for 27 years at great speed, has reached the inner walls of this cavity and is colliding with thicker blobs of the older material. That's the glowing ring we see so clearly in the Hubble image.
If you want to see a time lapse movie made of Hubble images taken each year as the ring started lighting up, you can see it at:
Happy fireworks day!
Tuesday, July 1, 2014
Last night, thanks to the Wonderfest organization in San Francisco, I got a chance to see a science fiction film that was in theaters for so short a time that if you blinked, you probably missed it. It's called "Europa Report" and it is the story of a crewed expedition to Jupiter's intriguing moon Europa. This world, one of the four large moons of Jupiter discovered by Galileo, is an ice-covered ball that may well have a large liquid ocean under its surface.
You can see Europa's cracked surface on the picture I have posted above. (This is actually a montage of images from NASA's Galileo spacecraft, with additional image processing by Professor Ted Stryk to bring out more detail.) One possibility is that the dark cracks we see are places where material from deeper inside the Moon (perhaps even from the liquid ocean) is seeping up toward the surface.
In the movie (see the poster below), future astronauts (from a private space company) go to Europa to search for evidence of life. The complex story is told by interweaving the view from cameras in their suits and in their cabins, with footage they recorded for sending back to Earth and interviews with the mission controllers, who eventually lose contact with the ship. What the surviving astronauts eventually find is far more than the micro-organisms scientists currently hope might exist deep under the ice of Europa.
The film, by Ecuadorian director Sebastian Cordero, is now available on DVD and various internet film services. If you enjoy somewhat complicated but scientifically reasonable space stories, I commend it to your attention. If not, spend a little time Googling other images of Europa and check out one of the strangest worlds with which we have the pleasure of sharing the solar system.