Saturday, December 30, 2017

New Year's Day Will Have a Supermoon


By a cosmic coincidence, the first day of 2018 will have a nice full Moon in the evening. And the full Moon occurs just when the Moon is closest to the Earth in its monthly orbit, so it will look a little bigger to us in the sky.
Since 2011, the media have followed a suggestion by an astrologer (!) and started calling these slightly closer full Moons "Supermoons" -- a name more likely to make people notice. We astronomers tried to fight the term, but we're mostly giving up.

On January 1, the Moon will be closest (at perigee) at 2 pm, Pacific time: it will be 221,600 miles from us. (The average distance is about 239,000 miles.) The full Moon officially happens only 4 hours or so later, at around 6 pm Pacific time.
So when the full Moon rises, in the evening, as the Sun sets, it will looks somewhat bigger and brighter than usual. It's no big deal, except to reporters eager to fill news copy during the holidays when news is slow. Still, it's always nice to have an excuse to notice the full Moon and show it to kids in your family or neighborhood.
Remember, the Moon is the only world other than Earth on which humans (12 of them) have stood and explored. Even just with your naked eye (but better with a pair of binoculars), you can see some of the bigger round craters on the Moon, evidence of the ancient violence that was common in the early days of the solar system. More than four billion years ago, large chunks of rock and ice were still moving around the system, hitting the forming planets and moons.
January 2018 is a blue-moon month (meaning two full moons will happen in the same month) and the second full moon, on January 31, will be more impressive. It will include not only a Supermoon, but a total eclipse of the Moon!
That eclipse will be best on the West Coast, but it will happen early in the morning. So you'll have to get up at 5:30 or 6 am on a Wednesday morning to see the full Moon fully eclipsed. I will have a much more detailed preview of the eclipse in this column when it's a closer in time.
Our photo, by astro-photographer Rick Baldridge, shows a full Moon seen above the historic Lick Observatory near San Jose.  Click on it to see it bigger.
On a personal note, I have just launched my own astronomy website at http://www.fraknoi.com and invite you to check it out. It's still a work in progress.

Tuesday, November 28, 2017

First Visitor from the Realm of the Stars Ever Found Is Oddly Shaped


Astronomers around the world have been observing a small but fast object that gives every indication of coming from some other star system. It's the first such "interstellar" visitor we have ever observed. And it's characteristics are quite unexpected.
Most astronomers expected the first such deep-space visitor to be a comet -- a chunk of icy material (which our solar system has in great abundance outside the orbits of the main planets.) But all the characteristics of this visitor argue against that idea. It didn't evaporate and develop a "tail" as it came closer to the Sun than Mercury. Any comet would have done that.
And it seems to spin in less than 8 hours. Something made of snowballs or ice might fall apart from such a fast spin. So it appears that our visitor is made of rock -- more like an asteroid and not like a comet. And its color is dark and reddish, like some asteroids we have seen from our own system.
Furthermore, its shape -- which we can estimate from the way the sunlight reflected from it changes -- is also odd. It appears to be much longer than it is wide. Our best estimate is a cigar shape (see the attached painting from the European Southern Observatory), perhaps half a mile long and only 80 yards in diameter. But it could also be a flat cylinder -- which reminds some people of the shape of the main body of the Starship Enterprise.
(Just to be sure, astronomers at the SETI Institute used their antenna array in Northern California to check if the visitor was sending any radio messages. Nothing was found.)
First discovered by a team led by Karen Meech of the University of Hawaii using a Hawaiian telescope, the visitor has been given a Hawaiian name: Oumuamua, which means "scout or messenger, arriving first" -- not a bad fit. Its scientific designation is 1I2017U1. The 1I stands for first interstellar object ever discovered!
When we found it on Oct. 19th, it was coming in fast from the direction of the constellation of Lyra. It's now going out at a speed of 86,000 mph relative to the Sun. It already crossed the orbit of Mars and will reach the distance of Jupiter in May 2018. Having been whipped around by the Sun's gravity, it will go out in a new and random direction, back toward the realm of the stars.
We expect that such visitors should be passing through all the time, but we haven't discovered them until now. With new surveys of small, dim objects in the sky soon getting under way, we expect to find a lot more small pieces from our own neighborhood -- and beyond. Stay tuned.

Monday, November 6, 2017

A Beautiful Star Cluster for Dark Times


As many readers switch from Daylight Savings Time to find darker evenings awaiting them, here is a beautiful new image from the Hubble Space Telescope. We see a "globular cluster" with the catalog name M5 -- an ancient collection of stars, with about 100,000 of them visible on this remarkable photo.
The image combines views taken with visible light and infra-red cameras, and highlights some of the younger bluer stars sprinkled among the older yellower stars that make up the majority of the cluster. This grouping is about 25,000 light years away and was born 12-13 billion years ago.
It was about 100 years ago that Harlow Shapley, one of the greatest astronomers of the 20th century, used such bright globular clusters to map the extent and shape of our Milky Way Galaxy and to demonstrate conclusively that the Sun and the Earth were not in its center.
Such a beautiful picture can help remind us that there is a larger perspective out there, and help us put aside thoughts of the crazy things we seem to be doing to each other and to our fragile planet on almost a daily basis. Click on the pictures to see them bigger.  The diagram below shows how the globular clusters, distributed above and below the plane of our Galaxy, help outline its shape and extent.


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: http://nasa.gov/live
You can access the image galleries and latest videos from the mission from this page (designed for the media, but which anyone can use): https://saturn.jpl.nasa.gov/mission/grand-finale/for-media/
By the way, you can access my free textbook at : http://openstax.org/details/astronomy 

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: http://fraknoisuniverse.libsyn.com/website
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."