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.

Perseid Meteor Shower May Show an Outburst

This Thursday and Friday, there will be one of the best annual meteor showers you and your family can watch -– the Perseids.    And some experts are even predicting that there might be a meteor “outburst” this year –- where the number of shooting stars increases beyond the usual rates.

This is a complicated year for watching the Perseid meteor shower, because the evening sky has a roughly half-lit-up moon in it, making it more difficult to catch the faint “shooting stars.”  So if you can wait until the Moon sets (between midnight and 1 am), you should have better viewing in the pre-dawn darkness.   (That’s great advice for people on camping trip and insomniacs, but probably not useful for those who have to get up for work.)

The best night is the evening of Thursday, Aug. 11 and morning of Friday, Aug. 12^th, although there could be significantly more meteors in the sky on the night before and the night after too.  Meteors or “shooting stars” (which have nothing to do with stars) are pieces of cosmic dust and dirt hitting the Earth’s atmosphere at high speed and making a flash of light.  These flashes could happen anywhere in the sky, so it’s best to view the shower from a wide-open place.  See the list at the end for viewing suggestions.

The Perseid meteors are cosmic “garbage” left over from a regularly returning comet, called Swift-Tuttle (after the two astronomers who first discovered it).  The comet itself returns to the inner solar system every 130 years or so; it was last here in 1992.  During each pass, it leaves dirt and dust behind and it is this series of long dirt and dust streams that we encounter every August.  Some scientists who study comets and meteors are predicting that we might briefly encounter an especially crowded part of the debris stream this time.

Each flash you see is a bit of material from the comet hitting the Earth’s atmosphere and getting heated up (and heating up the air around it) as it speeds through our thick atmosphere.  Both the super-heated dust and dirt and the heated air contribute to the visible light we observe.  Since comets are left-overs from the early days of our solar system, you can tell yourself (or your kids) that each flash of light is the “last gasp” of a bit of cosmic material that formed some 5 billion years ago.

EIGHT HINTS FOR “TAKING A METEOR SHOWER”

1. Get away from city lights and find a location that’s relatively dark

2. If it’s significantly foggy or cloudy, you’re out of luck

3. Your location should allow you to see as much of the dome of the sky as possible

4. Allow time for your eyes to get adapted to the dark (at least 10 -15 minutes)

5. Don’t use a telescope or binoculars – they restrict your view (so you don’t have to be part of the 1% with fancy equipment to see the shower; this is a show for the 99%!)

6. Dress warm – it can get cooler at night even in August (and don’t forget the insect repellent while you are outside)

7. Be patient (it’s not fireworks): keep looking up & around & you’ll see flashes of light

8. Take someone with you with whom you like to spend time in the dark!

Good Meteor Shower This Wednesday Night

This Wednesday evening and Thursday morning there will be one of the best meteor showers you and your family can see.

This is a great year for the Perseid meteor shower, because it is happening during the phase of the Moon called New Moon (which is when the moon is absent from the sky).  So there will be no moonlight to interfere with seeing the faint “shooting stars” of the meteor shower.

The best night is the evening of Wed, Aug. 12 and morning of Thur., Aug. 13, although there could be significantly more meteors on the night before and the night after too.  Meteors (which have nothing to do with stars) are pieces of cosmic dust and dirt hitting the Earth’s atmosphere at high speed and making a flash of light.

The peak of the shower is predicted to happen around 1 am PDT Aug. 13th, which means that after it gets dark on Aug. 12th, there should already a good number of meteors to watch for.

Here are a few tips for best viewing:

8 HINTS FOR TAKING A METEOR SHOWER

1. Get away from city lights and find a location that’s relatively dark

2. If it’s significantly foggy or cloudy, you’re out of luck

3. Your location should allow you to see as much of the dome of the sky as possible

4. Allow time for your eyes to get adapted to the dark (at least 10 -15 minutes)

5. Don’t use a telescope or binoculars – they restrict your view (so you don’t have to be part of the 1% with fancy equipment to see it; this is a show for the 99%!)

6. Dress warm – it can get cooler at night even in August

7. Be patient (it’s not fireworks): keep looking up & around & you’ll see flashes of light

8. Take someone with you with whom you like to spend time in the dark!

The Perseid meteors are cosmic “garbage” (dust and dirt clumps) left over from a regularly returning comet, called Swift-Tuttle (after the two astronomers who first discovered it).  The comet itself returns to the inner solar system every 130 years; it was last here in 1992.  During each pass it leaves dirt and dust behind and it is this long dirt and dust stream that we encounter every August.  Some experts are predicting we might briefly encounter an especially crowded part of the debris stream this time.

Each flash you see is a bit of material from the comet hitting the Earth’s atmosphere and getting heated up (and heating up the air around it) as it speeds through our thick atmosphere.  Both the superheated dust and dirt and the heated air contribute to the visible light we observe.  Since comets are left-overs from the early days of our solar system, you can tell yourself (or your kids) that each flash of light is the “last gasp” of cosmic material that formed some 5 billion years ago.

[Note: image from Mike Hanley, American Meteor Society]

Wonderful New Image of Comet We Are Flying Along With

The Rosetta spacecraft is continuing to circle Comet 67P (also known as Comet C-G) and send back amazing images. The picture accompanying this post was taken on Feb. 6 at a distance of 75 miles from the comet.

Rosetta, a mission by the European Space Agency, is flying along the icy chunk that is the comet, accompanying it on its long voyage to whip around the Sun. As we get closer, the ice of the comet will evaporate more and more, and great jets of gas will be seen coming from the comet. (Ice turns directly into gas in the vacuum of space.) You can see the beginning of this activity on our photo.

For the sake of honesty, we should mention that this 6-second image was processed to make the faint jets appear brighter and more easily visible.

We now know that the comet consists of two sections (called lobes, likes the two parts of your brain) connected by a slender neck. The bigger lobe is about 2.5 miles across, while the smaller one is about 1.5 miles wide. The jets seem to be coming from the neck region, which has been named Hapi, after the god in Egyptian mythology who makes the Nile River flood every year.

As the comet continues toward the Sun for its August closest approach, we expect many more spectacular jets to erupt on its surface. Stay tuned for wonderful images!

To see a first map of the regions on Comet 67P and what Egyptian gods the ESA scientists have named them after, see: http://sci.esa.int/rosetta/55297-comet-regional-maps/

A Beautiful Comet Passes By

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:
http://www.skyandtelescope.com/astronomy-news/observing-news/spot-comet-lovejoy-tonight-122920141/ 
or
http://www.universetoday.com/118031/if-you-can-find-orion-you-can-find-comet-lovejoy/ 

Landing on a Comet: High Adventure in Space

This Wednesday, a European landing craft called "Philae" will attempt humanity's first landing on a fast-moving comet (a complex chunk of ice approaching from the depths of space.)

After a 10-year, 4-billion mile journey to Comet Churyumov-Gerasimenko (C-G for short), the Rosetta spacecraft (which is now orbiting the comet) will drop a probe about the size of a kitchen range from a height of 13 miles.  Taking some 7 hours to slowly land on its icy target, Philae will be moving at only 2 miles per hour at the end.  Still, the gravity of the two-mile wide comet is so low, it could bounce off and move away or simply fall over and roll.   To prevent this, the designers have equipped Philae with harpoons to grab the comet and with legs that have rotating screws in them to hold on to the ice for dear life.

Our robot representatives have only landed on six worlds so far: the Moon, Mars, Venus, Saturn's moon Titan, and two asteroids.  None of those landings were quite as difficult and strange as this one.  It takes radio signals from Rosetta about half an hour to get back to Earth even at the speed of light.  Thus the European Space Agency controllers can't help Philae if it gets into trouble.  Its own computer software will have to make the decisions that will lead to its survival or loss. 

For a complete picture of Comet C-G, see my August 6 post.  The photo accompanying today's post is a fantasy montage, showing the Philae lander safely on the comet's icy, boulder-strewn surface.  The full comet has a weird L-shaped structure, as if two oval comets had somehow stuck together at a weird angle. Because its shape is so complex, its gravity is not simple either, making landing even more challenging. But if Philae lands, its 10 instruments will give us our first-ever up-close look at one of the chunks of ancient ice that are building blocks left over from the early days of our solar system. 

Keep your fingers and toes crossed that the landing succeeds.  For a basic animation of what the spacecraft will do and what instruments it carries, please see: http://www.youtube.com/watch?v=szKZ77MbF9Q  

A fuller documentary about the Rosetta mission, see: http://www.youtube.com/watch?v=cArihDTnOZg 

A Comet Passes by Mars; An Eclipse of the Sun

 

On Thursday afternoon, Oct. 23, there will be a partial eclipse of the Sun, visible from the U.S. Different amounts of the Sun's area will be covered by the Sun. (For example, 40% of the Sun will be covered from the San Francisco region.) I have put question-and-answer introductions to the eclipse at: http://www.astrosociety.org/society-news/2014-eclipse-fact-sheets/

You can consult the national sheet for the degree the Sun will be eclipsed in your area. Here's wishing everyone clear skies. And please remember, do NOT look at the Sun without proper protection. Follow the instructions on the sheets or go to an astronomy place (observatory, college, planetarium) near you to join an eclipse viewing session.

This Sunday, Oct. 19th, a comet will pass closer to Mars, than any comet has passed to the Earth in recorded history. Comet Siding Spring (named after the observatory where it was discovered) will pass within only 87,000 miles of Mars. An armada of telescopes near Mars and Earth will try to get a good glimpse of it. From its orbit, this appears to be what you might call a "virgin" comet, making its first entry to the inner solar system. It is coming from the distant reservoir of ancient "icy chunks" that surround our solar system in a giant cloud.

A comet is just such an icy chunk that comes close enough to the Sun so that the Sun's energy and wind begin to evaporate the ice and loosen the dust frozen inside it for billions of years. These comets thus contain some of the original material from which our solar system was formed some 5 billion years ago. 

To learn more about NASA's plans for observing this Mars visitor, see: http://science.nasa.gov/science-news/science-at-nasa/2014/09oct_cometprep/

For a while, NASA scientists worried that dust from the comet may damage some of the spacecraft around Mars, but recent calculations are showing that the path the comet is taking means that its dust is not likely to pose a serious threat.  But we'll see Sunday.  Perhaps there will be faint "shooting stars" (dust burning up in the thin atmosphere) on Mars.

Happy Fall Equinox on Monday and Other Sky Events

Monday morning (Sept. 22) is the "autumnal" or fall equinox for those of us in the Northern Hemisphere. On that day, the length of the day and the night are roughly the same ("equinox" means equal night). We are moving from the summer, when the days were longer, toward the winter when our nights are longer -- and our parts of the planet have fewer hours to heat up from sunlight.

The equinox is sometimes called the official start of fall and throughout history there have been festivals and beginnings celebrated at the time. It so happens that Foothill College, where I teach, starts its fall quarter on the equinox this year, so I will be welcoming several hundred new students to my classes with a happy equinox greeting (and many who don't know the term will be looking at me as if I were a crazy person!)

The fall quarter will bring many interesting events to fans of astronomy. Tonight, Sunday, the MAVEN spacecraft will be inserted into orbit around Mars, so it can begin to study how little Mars, with its lower gravity, lost its atmosphere over the millennia, and how its remaining air layers interact with the radiation and wind from the Sun.

October 8th, we will have a total eclipse of the Moon (these are much more common than total eclipses of the Sun.) Alas, for those of us in North America, this will be a middle of the night eclipse! The full Moon will go dark as the Earth's shadow falls on it, but most of us will be in bed, deeply asleep, when it happens. For example, in San Francisco, the eclipse happens from about 2:30 am to 5:30 am, so only dedicated night owls will be watching it. (If you miss it, don't worry, there will be two lunar eclipses visible in 2015.)

On October 19th, a newly discovered comet will come closer to the planet Mars than any known comet has come to Earth, and so our robot "representatives" around Mars will be keeping their cameras out for that pass.

On October 23rd, in the afternoon, much of North America will witness a partial eclipse of the Sun in the afternoon. Many astronomy organizations will be planning eclipse parties, with safe viewing options. I will do a full post about the eclipse when we get closer to the time.

And, down on Earth, October 25th, the opening day of the 2014 Bay Area Science Festival, I will be giving a free public talk on Mt. Tamalpais about the "Top Tourist Sights of the Solar System: Where Bill Gates' Great-Granddaughter will go for Her Honeymoon." See: http://wonderfest.org/top-tourist-signs-of-the-solar-system/

Close-up View of a Comet

Today the Rosetta spacecraft closed in on Comet 67P (the P stands for periodic comet, meaning it comes around again and again every six and a half years. ) It's also known as Comet Churyumov–Gerasimenko (C-G). Look at the amazing image our cameras sent back, taken from a distance of only 177 miles.

The comet and the spacecraft are currently still about half way between the orbit of Jupiter and the orbit of Mars.  In this exciting rendezvous, Rosetta will match course with the icy comet and then stay with it as it gets closer and closer to the Sun and its ice begins to "sublimate" (turn from ice directly to a vapor in the vacuum of space.) 

We hope to stay with the comet for a year, as it goes inward and then swings back outward again, watching the Sun's light and heat playing with the comet all the while. In November, part of Rosetta will actually land on the icy surface of Comet 67P.

But for now, just enjoy the weird and wonderful image.   The comet's shape is definitely not symmetrical.  Is it two ice pieces that stuck together in an ancient collision?  Have past encounters with the Sun's heat resulted in this odd shape?

The comet is 2.5 miles wide, and you can see details as small as 17 feet (5.3 meters) across on our picture.   Can you see the individual "boulders" or "ice rocks" sitting on the comet's surface?

If you'll pardon the expression, what a cool picture!

By the way, click on the photo to see it bigger and with more detail.

Strange Shape to a Comet We are About to Visit

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 
space: http://sci.esa.int/rosetta/54356-rotating-view-of-comet-67pc-g-on-14-july-2014/ 

Comet ISON Ready for its Thanksgiving Date with Destiny

When it was discovered in 2012 as a new comet coming from deep space, some observers predicted Comet ISON would become so bright in our skies it would be the "Comet of the Century." Wiser heads knew, as comet hunter David Levy likes to say, "Comets are like cats. They have tails and they do precisely what they want!"

For a while, the comet seemed disappointing. But this week, on its way in to a close encounter with the Sun, Comet ISON started putting on a somewhat better show (as you can see in the image, taken by the skillful UK astro-photographer Damian Peach.) The comet now has two nice tails, one made of dust, the other of gas, pointing in the direction away from the Sun.

The comet is currently visible in the pre-dawn sky, but only barely and only when it's really dark. It's better with binoculars or telescopes. The excitement, however, is just beginning. Comet ISON is what astronomers call a "sungrazer" -- a comet that comes indecently close to our Sun. It just so happens, the closest encounter -- only about 3/4 of a million miles from the Sun's surface -- will be on Thanksgiving Day 2013.

The solid "nucleus" of this comet -- a chunk of frozen ices and rock -- is now estimated to be somewhere between 1/4 and 3/4 of a mile across. The Sun's heat could vaporize much of its ice and rock and the Sun's gravity could tear it apart into smaller chunks. Past sungrazing comets have had one or both of these things happen. So it could emerge from its date with the Sun one smaller but strongly evaporating comet, or as several comets spread out over a wider area, or as nothing more than a subtle trail of gas and dust.

If Comet ISON survives Thanksgiving, it will swing away from the Sun and emerge into our dark skies going northward from the plane of our solar system. Should there be enough of it left to make a show, that show will be visible to us in December and January. Around January 8th, for example, it will be near the north star, remaining in our view all night long. (But by then it will likely be much fainter.)

As we say on the radio, "Stay Tuned!" I will give you more updates on this interesting new visitor to our cosmic neighborhood in future posts.

If your want bulletins on Comet ISON between my posts, or need more technical information, see the "Current Status" page at NASA’s Comet ISON Campaign: http://isoncampaign.org/Present and then look around on that site.

[If you search the web for Comet ISON information, beware of the nutty websites predicting a collision with Earth or some other reason for the end of the world. The closest the comet will get to Earth is about 40 million miles on Dec. 26th. That's far enough that we can all sleep soundly at night.]

Comet PanSTARRS: Beware of the Internet Hype, but Check out the Sight

This coming week is perhaps the best time to look for a new comet in our evening skies, as long as your expectations are not set too high by some of the media attention it has received.   The comet – a chunk of ice and dirt from the distant backwaters of the solar system – is falling around the Sun with closest approach to our star on Sunday, March 10^th.  

For the next week, it will be visible very low on the horizon if you look toward the west.  Tuesday and Wednesday it will be near the crescent Moon and may be easier to spot as a result.  But here are the problems beginners will need to keep in mind:

1. It’s so low in the sky you will need to look for it from a location where you have a clear view all the way down to the western horizon -- and no hills, buildings, or trees in the way.  Out by the ocean is really great.

2. Things on the western horizon are SETTING – going quickly below the edge of the sky.  That means there is a very short window to see the comet.  Try too early, and the sky is too bright with sunlight.  Try too late, and the comet is below the horizon.  About 30 - 45 minutes after sunset is what experts are recommending.

3. If there are clouds or fog in the western direction, or you’ve got bright street or car lights in your view, the comet may be too hard to see.  In March, weather is an issue in many locations.

4. And the comet is so far from Earth, it is not spectacularly bright. In general, binoculars may be needed to pick the head of the comet and the faint upward-pointing tail out of the glow of the sunset.

Get the latest observing information at: http://www.skyandtelescope.com/observing/highlights/Spot-Comet-PanSTARRS-in-Twilight-196688441.html

By the way, if you are wondering about the strange name for a comet, it’s taken from the automated survey telescope in Hawaii that discovered it in 2011: the Panoramic Survey Telescope and Rapid Response System.