Sunday, October 15, 2017

A Ring Around the Dwarf Planet Haumea

European astronomers have announced the first discovery of a ring around a dwarf planet. Dwarf planets are similar to Pluto, in that they are small and hang out in a zone with others of their kind. This one, Haumea, is beyond Neptune, taking 284 Earth years to go around the Sun.
The ring is very faint, but astronomers at the Institute of Astrophysics of Andalusia were able to find it when they saw Haumea cross in front of a star. The star’s light went out not only when Haumea crossed in front of it, but briefly before and after, indicating a ring was present.
All four of the giant planets in our solar system have rings, but this is the first found around a smaller planet. Its cousin Pluto definitely doesn’t have one, because we looked when the New Horizons probe went by it.
Haumea is named after the Hawaiian goddess of childbirth and has another oddity. It spins so rapidly – taking less than 4 hours for one spin -- that it doesn’t look exactly round, but more oval shaped. It’s the least round of any world we know bigger than about 60 miles across. It has two known moons, and now a ring too. The zone past Neptune, called the Kuiper Belt, is just getting more and more interesting.
(Our illustration is NOT a photo, just an artist's impression, based on what we have observed so far.)

Wednesday, September 13, 2017

Cassini Space Probe To Fall Into Saturn Friday Morning

Friday morning, around 5 am Pacific time, NASA will send the Cassini space probe falling into the planet Saturn -- until it is crushed by the pressure in the ringed planet's atmosphere. NASA is commanding Cassini to "commit suicide" before its propellant runs out and it can't be steered any more. Since Saturn has two moons which might harbor some sort of primitive life, we wanted to make sure we did not contaminate those worlds.

The planet Saturn is made mostly of gas and liquid (and its make-up is dominated by the two lightest elements in the universe, hydrogen and helium.) So you can't land ON Saturn, you can only fall INTO Saturn (like a giant ocean world.)
Cassini has been orbiting Saturn for 13 years, sending back amazing pictures and information on the planet, its complicated rings, and its 62 moons. It's made a slew of remarkable discoveries, including the presence of warm salt-water geysers on the relatively small moon called Enceladus, and lakes and rivers of liquid fuel oil on the giant moon Titan. It was launched 20 years ago (so it's had a long and fulfilling life for a spacecraft.)
Since April, it has been swooping in and out of the space between Saturn's cloudtops and its inner rings, an area we had never had the nerve to explore before. NASA estimates the spacecraft has traveled almost 5 billion miles in total and has sent back more than 450,000 picture (that's a Flickr file not even your most picture-taking relatives can compete with!)
In our image, you can see Saturn and its complex ring system, with a painting of the spacecraft above the planet's north pole, ready to make a dive.
Some of my favorite pictures in the introductory astronomy textbook I am the lead author on come from Cassini (which was the most complicated planetary explorer ever built.) On Friday morning, let's give it a thought as we wake up -- we'll miss you, Cassini!
You can see live coverage of the last days of the mission on NASA TV at:
You can access the image galleries and latest videos from the mission from this page (designed for the media, but which anyone can use):
By the way, you can access my free textbook at : 

Monday, September 4, 2017

Double Eclipse of the Sun; Eclipse Statistics

My favorite picture so far of the recent eclipse of the Sun is the one you see with this post. Photographer Simon Tang (who gave me permission to reproduce it here) took a sequence of photos from Huron, California, recording the International Space Station crossing the face of the Sun just as the Moon was eclipsing it.
Each of the images of the Space Station is less than 1/1000th of a second long, since the Station moved across the Sun in less than a second. The image is taken in H-alpha, a specific color of light emitted by hot hydrogen atoms in the Sun's lower atmosphere. You can see the Station close up in our second image.

NASA reports impressive statistics for the Aug. 21 eclipse: 90 million page views on NASA's two websites, 40 million views of the live broadcast, 3.6 billion users on social media, and the most popular Instagram image ever -- all of a celestial event with no politics, no national or religious affiliation. It was just nature, doing its thing, predictably, reliably, spectacularly.
In our own project, 2.1 million eclipse glasses were distributed to 7,100 libraries -- all to be given away free to the public. I was one of the astronomers leading the effort, and want to thank the Moore Foundation, Google, and NASA, for supporting the program to allow public libraries to help their patrons observe the eclipse safely. If only we could come together this well about other things!

Click on the images to see them bigger.

Wednesday, August 23, 2017

A Short Eclipse Mega-movie Already Available

A first 2.5-minute version of the Google Eclipse Megamovie is now out and can be viewed at:
This is actually version 2, which shows a map at the bottom right indicating where along the path of the total eclipse in the U.S. each image comes from. The team soon expects to have a much longer version with many more pictures taken during the 1 hour 37 minutes that the eclipse was over the continental U.S. stitched together.
So far over 6,000 images from the serious photographer volunteers, over 11,000 images via the online image upload from the public, and over 45,000 images via the App the team developed have been received, according to a message I got minutes ago from project leader Laura Peticolas of the University of California, Berkeley's Space Sciences Lab. What a nice example of citizen science!
I hope you all had good eclipse viewing Monday. I was in central Oregon with family and friends, and got a spectacular view of the total eclipse, with beautiful red prominences (great fountains of hot material being driven outwards from the surface of the Sun) visible through binoculars. The attached image above, from one member of our group, Dr. Cary Sneider, gives you a little taste of what we saw.
The other attached image, below, by Anna Rich, shows a car on the highway, on its way home from Oregon, expressing a sentiment many felt.
For anyone who missed the lead-up to the eclipse, a fun way to get caught up might be my conversation with veteran newscaster Gil Gross, at:
This eclipse special might be the first of a series of podcasts we will do on astronomical news and ideas, starting later in the fall. Stay tuned for more on what the producer's are calling "Fraknoi's Universe."

Sunday, August 6, 2017

Eclipse of the Sun Coming in 2 Weeks! And Another in 7 Years!

The path from top left to bottom right is the Aug. 21, 2017 eclipse
The path from bottom left to top right is the Apr. 8, 2014 eclipse

In just two weeks, on August 21, all of North America will experience an eclipse of the Sun. The eclipse will be total on a narrow path going across the U.S. from Oregon to South Carolina. The rest of the continents will see a partial eclipse, with a big bite taken out of the Sun by the disk of the Moon.
If you don't get to see this one, there will be another U.S. total eclipse in only seven years (on April 8, 2024.) If you missed out getting a hotel room or a campground in the zone of totality for August's eclipse, you have no excuse now for 2024! (See the attached map; click on it to see it bigger.)
I've had the opportunity to do quite a bit of media outreach for the eclipse; you can:
1. hear me as part of the eclipse special on the "Big Picture Science" radio show:…/eclipsing-all-other-shows
2. see me speaking on the eclipse at the SkeptiCAL convention sponsored by the Bay Area Skeptics:
3. read my comments as part of legendary science journalist David Perlman's last science article (David, who covered science news at the San Francisco Chronicle, is retiring at the age of 99! May we all have a career as long and respected as his.):…/Total-solar-eclipse-to-create-…
This week many media and people are waking up to the coming of the eclipse at last. Our free 8-page booklet all about it and how to view it safely can be downloaded from the page: Do read through it to get hints about how best to see and explain this rare sky phenomenon.
A free app, called TOTALITY, can be downloaded from both the Apple and Android app stores, and it will tell you exactly when and how the eclipse will be visible in your location.
If you haven't yet gotten safe eclipse-viewing glasses, your first stop should be your local public library. (Thanks to the Moore Foundation and Google, our project to distribute 2.1 million eclipse glasses has gotten glasses to almost 7,000 public libraries nationwide.)
If your library doesn't have any, here is a page to tell you all the reliable sources of eclipse glasses that are certified to meet the standards for protecting your eyes set by eye-doctors:
And for kids, please forgive me if I mention our children's book, "When the Sun Goes Dark," now in its fourth printing. Copies have temporarily run out in some places, but the publisher has it at:
Here is wishing you clear skies for August 21.

Eclipse stamp issued by the US Postal Service
changes the picture you see when you touch it

Tuesday, July 11, 2017

New Hubble Image of Jupiter's Red Spot

Astronomers are eagerly awaiting new information about the Great Red Spot, the largest and most colorful storm in the atmosphere of the giant planet Jupiter. The Juno spacecraft just flew as close as 5600 miles over the Red Spot, and the information is coming slowly back to Earth. This giant storm is currently about 10,000 miles wide -- larger than the entire planet Earth -- although it is smaller than when the Voyager spacecraft flew by in the 1970's. Why it has been shrinking and why it's color is so vivid are mysteries planetary scientists are trying to solve. 
In the meantime please enjoy the attached Hubble Space Telescope image of Jupiter, taken on April 3, when the Earth was closest to Jupiter in its yearly orbit. The Red Spot is vividly clear on this wonderfully detailed image, taken from just a few hundred miles above our planet's surface.  (Click on the image to see it bigger.)

Wednesday, June 21, 2017

Eclipse Talk on YouTube and New Kind of Eclipse Stamp

We are exactly two months away from the eclipse of the Sun that is coming to North America on August 21, 2017. I gave an illustrated, non-technical talk on the eclipse in the Silicon Valley Astronomy Lecture series, and it is now available on YouTube at: The talk has lots of information and visuals on where and how the eclipse will be visible, how to watch it safely, and how the U.S. is preparing for the huge crowds that are expected in the narrow zone where the eclipse will be total.
   Yesterday, the U.S. Postal Service issued its first ever "thermochromic" stamp in honor of the eclipse. That means when you touch the picture, it changes. Clearly this is a stamp every science will want to have. You can get them at your post office or by mail through:
   If you have not planned for the eclipse yet, now is the time to start thinking about where you will be on Monday, Aug. 21 and how you and your family or colleagues will observe the eclipse. In the video, I explain what is happening and give suggestions for safe viewing techniques. (Remember, any time any part of the Sun is showing, it's not safe to look at with just your eyes or sunglasses.)
   Thanks to grants from the Moore Foundation and Google, three astronomy colleagues and I were able to distribute 2 million safe eclipse-viewing glasses to public libraries nationwide. Check with your library to see if they are participating. The free booklet for libraries can be downloaded by anyone at: