Rings are a tough phenomenon to spot. As late as 1977, astronomers thought that the only thing in the solar system with rings was the planet Saturn. Now, we can add the first asteroid to the list of ringed bodies nearby us. The asteroid 10199 Chariklo hosts two rings, perhaps due to a collision that caused a chain of debris circling its tiny surface.
Besides the 250-kilometer (155-mile) Chariklo, the only other ringed bodies known to us so far are (in order of discovery) Saturn, Uranus, Jupiter and Neptune.
“We weren’t looking for a ring and didn’t think small bodies like Chariklo had them at all, so the discovery — and the amazing amount of detail we saw in the system — came as a complete surprise,” stated Felipe Braga-Ribas of the National Observatory (Observatório Nacional) in Brazil, who led the paper about the discovery.
The rings came to light, so to speak, when astronomers watched Chariklo passing in front of the star UCAC4 248-108672 on June 3, 2013 from seven locations in South America. While watching, they saw two dips in the star’s apparent brightness just before and after the occultation. Better yet, with seven sites watching, researchers could compare the timing to figure out more about the orientation, shape, width and more about the rings.
The observations revealed what is likely a 12.4-mile (20-kilometer)-wide ring system that is about 1,000 times closer to the asteroid than Earth is to the moon. What’s more, astronomers suspect there could be a moon lying amidst the asteroid’s ring debris.
If these rings are the leftovers of a collision as astronomers suspect, this would give fodder to the idea that moons (such as our own moon) come to be from collisions of smaller bits of material. This is also a theory for how planets came to be around stars.
The rings haven’t been named officially yet, but the astronomers are nicknaming them Oiapoque and Chuí after two rivers near the northern and southern ends of Brazil.
Because these occultation events are so rare and can show us more about asteroids, astronomers pay attention when they occur. Part of the Eastern Seabord enjoyed a more recent asteroid-star occultation on March 20.
The original paper, “A ring system detected around the Centaur (10199) Chariklo”, will soon be available on the Nature website.
North America’s brightest predicted asteroid occultation may be one-upped by a much bigger occultation – a solid blanket of clouds. Asteroid 163 Erigone will cover or occult the bright star Regulus shortly after 2 a.m. Eastern Daylight Time tomorrow morning March 20. Observers along a 45-mile-wide (73-km) belt stretching from the wilderness of Nunavut to the salty seas of Bermuda could see the star vanish for up to 14 seconds. Provided they can find a hole in the clouds.
Overcast skies with a mix of rain or snow are predicted along virtually the entire track from the tiny berg of Cochrane in northern Ontario south through New York City, Connecticut and New Jersey. A sluggish cold front isn’t expected to clear skies until … no surprise here … after the event is over.
But there is one place where maybe, just maybe, the clouds may part to let Erigone do its job. Bermuda. The Bermuda Weather Service forecast calls for highs in the low 70s mid-week, but that balmy air may come packaged with a partly to mostly cloudy sky at the time of the occultation. A few determined observers are on their way there right now, hoping for better weather. In case the islands are socked in, some plan to rent planes to rise above the low-lying clouds typical this time of year and revel in the shadow of an asteroid. Even if clear, Bermuda lies near the eastern edge of the path. Any occultation there will be brief.
Yes, there will be more occultations, but bright ones that the public can enjoy with the naked eye are rare.
Skywatchers are nothing if not hopeful. We believe in the sucker hole, the name given to rogue clearings in an otherwise overcast sky. We are patient and steadfast when it comes to glimpsing the rarest of the rare. I know this because my friends and I have stood outside on winter mornings staring at the western sky, waiting for clouds to peel back that we might glimpse a Martian dust storm or new comet.
If there’s an astronomer’s credo, it’s this: “The sky might clear yet!” The latest weather word (9 a.m. March 19) for U.S. and Canadian observers indicates thinner clouds along the southern end of the track in New Jersey. Many of us considered driving to the event but changed our minds because of work, worries about weather and other commitments. Assuming the credo holds true, you’ll be able to watch Regulus disappear live from the comfort of your home thanks to the efforts of several observers planning to stream the event on the Web.
Here’s a list of streamers so far:
* Brad Timerson plans to go live with audio at 2 a.m. at a rest area along I-90 just west of Syracuse, NY.
Or, more accurately, watch the Moon pass in front of Saturn. Either way you get the same result: a beautiful video of planetary motion in action!
On the morning of Saturday, Feb. 22, the Moon drifted in front of the planet Saturn from the point of view of certain locations on Earth. Luckily one of those locations was Perth, Australia, where astrophotographer Colin Legg happens to be, and thus we all get to enjoy the fantastic results of his photographic and astronomical acumen.
Check out the video below:
The occultation — as such events are called whenever one celestial object passes in front of, or “hides,” another (the root of the word means “to conceal”) — may make it look like a tiny Saturn is getting absorbed by a giant Moon. But (obviously) they are separated by a vast distance: at the time of the occultation, 9.658 AU, or about 1,444,816,000 kilometers (897.7 million miles).
These sort of events will become a bit more common as the Moon is “headed towards a ‘shallow’ year in 2015 relative to the ecliptic; it will then begin to slowly open back up and ride high around 2025,” according to a recent Universe Today article by David Dickinson.
For those of you interested, Colin lists his equipment as a Celestron C8, f/10, prime focus. His camera is a Canon 5D2, running Magic Lantern RAW video firmware in 3x crop mode @ 1880 x 1056 resolution. Footage was taken at 1/60 sec exposure, ISO 200, 10 fps.
Fluffy, with a core of density. That’s what the interior of the asteroid 87 Sylvia likely looks like, astronomers say. The neatest thing about that observation? It didn’t require a drill or even a spacecraft visit. That came from watching the orbits of the asteroid’s two moons, Romulus and Remus.
The discovery illustrates the power of amateur and professional astronomers working together, the team said. On Jan. 6, dozens of small telescopes across France, Greece and Italy were set up to watch a celestial show: watching Sylvia move in front of an eleventh-magnitude star. The professionals received assistance from European Asteroidal Occultations (EURASTER), a group of professional and amateur observers, for this event.
“Observers at different locations see different parts of the asteroid, or its moons, passing in front of the star,” the team stated in a press release. “Such occultations allow exquisitely precise measurements of the relative positions and sizes of the occulting objects.”
Of the 50 observers watching the show, twelve of them saw the occultation, which lasted anywhere from four to 10 seconds depending on where the observers were.
Subsequently, the professional astronomers determined how Sylvia is shaped by using that information and combining it with other data, such as recordings of the asteroid’s light variations that happened as it spun, and some direct images using adaptive optics. The team noted that Romulus and Remus don’t seem to change in their paths in space due to Sylvia’s non-circular shape, making them conclude that it has an interior of different materials.
All told, there were 66 adaptive optics observations of the asteroids using 8 to 10 meter telescopes at the W. M. Keck Observatory, the European Southern Observatory, and Gemini North. Calculations of the system came from the Institute of Celestial Mechanics and Ephemerides Calculations (IMCCE) of the Paris Observatory.
“Four observers detected a two-second eclipse of the star caused by Romulus, the outermost moon, at a relative position close to our prediction. This result confirmed the accuracy of our model and provided a rare opportunity to directly measure the size and shape of the moon,” stated Jérôme Berthier, an IMCCE astronomer.
“Combined observations from small and large telescopes provide a unique opportunity to understand the nature of this complex and enigmatic triple asteroid system,” added Francis Marchis, a senior research scientist at the Carl Sagan Center of the SETI Institute, who led the research. “Thanks to the presence of these moons, we can constrain the density and interior of an asteroid, without the need for a spacecraft’s visit. Knowledge of the internal structure of asteroids is key to understanding how the planets of our solar system formed.”
The results were presented yesterday (Oct. 7) at the American Astronomical Society’s division of planetary sciences meeting in Denver.
Sky watchers worldwide are in for a treat Sunday evening September 8, 2013 as the waxing crescent Moon passes near the dazzling planet Venus. And for a select few, the Moon will actually pass in front of Venus, in what is known as an occultation.
The action has already started this week, as the Moon reached New phase earlier today at 7:36 AM EDT/11:36 UT. The appearance of the slim crescent Moon nearest to the September equinox marks the start of the Jewish New Year with the celebration of Rosh Hashanah, which this year began as early as it possibly can at sundown on September 4th. As per tradition, Rosh Hashanah formally begins when the sky is dark enough for three stars to be seen. The convention established by Hillel II in 363 A.D. uses the mean motion of the Moon to fix the start dates of the Jewish luni-solar calendar, which means that occasionally Rosh Hashanah can start a day early. This also occurred in 2002.
The New Moon has also been historically an opportune time for nighttime military operations to commence —Desert Storm in 1991 and the raid against Bin Laden in 2011 were both conducted under the darkness afforded by the absence of moonlight around a New Moon. It’s yet to be seen if planners looking to conduct airstrikes on Syria are planning on taking advantage of the same conditions to begin operations soon.
Tonight, you can see the +1st magnitude star Spica less than two degrees away from -4th magnitude Venus. This places Venus at 100 times brighter than Spica and visible before sunset if you know exactly where to look for it.
The brightest star in the constellation Virgo, Spica is 260 light years distant and on the short list of nearby stars that will eventually go supernova. Fortunately for us, Spica is well outside of the ~100 light year radius “kill zone”.
You might just be able to spy the Moon and the -1st magnitude planet Mercury low to the west at dusk for the first time for this lunation tonight or (more likely) Friday night. This is also a great time to check out LADEE’s future home as it departs for lunar orbit from Wallops Island in Virginia on Friday night.
Hey, LADEE sitting on the pad atop its Minotaur V rocket with the slim crescent Moon in the background at dusk Friday night would be a great money shot, I’m just sayin’…
This weekend will see the Moon increase in illumination and elevation above the western horizon each evening until Spica, Venus, and the waxing crescent Moon fit within a four degree circle on Sunday night. The Moon will be 12% illuminated, while Venus is currently at a gibbous phase and 72% lit.
This will also present a good chance to see Venus during the daytime, using the nearby crescent Moon as a guide. This is a fun thing to try, and no gear is required! Though Venus may seem tough to find against the bright daytime sky, appearances are deceptive. With an albedo of 67% versus the Moon’s average of 14% Venus is actually brighter than the Moon per square arc second of size!
The Moon will also occult Spica on the evening of September 8th for observers in the Middle East and Europe right around sunset. Spica is one of four bright stars that the Moon can occult in the current epoch, along with Antares, Aldebaran, and Regulus. This is also part of a series of fine occultations of Spica by the Moon ongoing from 2012 to 2014.
Sundown on September 8th offers a special treat, as the 3-day old Moon passes less than a degree from Venus worldwide. The pair will fit easily into the field of view of binoculars or a telescope at low power and present an outstanding photo op.
And for observers based in Argentina and Chile, the Moon will actually occult Venus. Occultations are grand events, a split-second astronomical event in a universe that seems to usually move at a glacial pace. This particular occultation occurs for South American observers just before & after sunset.
We witnessed and recorded a similar pairing of Venus and the daytime Moon from the shores of our camp on Saint Froid Lake in northern Maine back in 2007:
Also, keep an eye out for a ghostly phenomenon known as the ashen light on the dark limb of the Moon. Also known as Earthshine, what you’re seeing is the reflection of sunlight off of the Earth illuminating the (cue Pink Floyd) dark side of the Moon. When the Moon is a crescent as seen from the Earth, the Earth is at gibbous phase as seen from the nearside of the Moon. Remember, the lunar farside and darkside are two different things! Earthshine can vary in brightness, based on the amount of cloud and snow cover present or absent on the Earth’s moonward side. My Farmer’s Almanac-consulting grandpappy would call ashen light the “Old Moon in the New Moon’s arms,” and reckon rain was a comin’…
Be sure to check out these astronomical goings on this weekend, and send those pics in to Universe Today!
The planets are slowly returning into view this month, bashfully peeking out from behind the Sun in the dawn & dusk sky. This month offers a bonanza of photogenic conjunctions, involving the Moon, planets and bright stars.
The action begins tonight on July 8th, as the waxing crescent Moon joins the planet Venus in the dusk sky. The razor thin Moon will be a challenge on Monday night, as it just passed New on the morning of the 8th at 3:14AM EDT/7:14 Universal Time (UT). The record for spotting the thin crescent with the naked eye currently stands at 15 hours and 32 minutes, completed by Stephen O’Meara on May 1990. Binoculars help considerably in this endeavor. Wait until 15 minutes after local sunset, and then begin patiently sweeping the horizon.
Mr. Thierry Legault completed an ultimate photographic challenge earlier today, capturing the Moon at the precise moment of New phase!
This week marks the start of lunation 1120. The Moon will be much easier to nab for observers worldwide on Tuesday night, July 9th for observers worldwide. The sighting of the waxing crescent Moon will also mark the start of the Muslim month of Ramadan for 2013. Due to the angle of the ecliptic in July, many northern hemisphere observers may not spot the Moon until Wednesday night on July 10th, about 6.7 degrees south west of -4.0 magnitude Venus.
Did you know? There are Guidelines for the Performance of Islamic Rites for Muslims aboard the International Space Station. It’s interesting to note that the timing of the rituals follows the point from which the astronaut originally embarked from the Earth, which is exclusively the Baikonur Cosmodrome in Kazakhstan for the foreseeable future of manned spaceflight.
Malaysia’s first astronaut, Sheikh Muszaphar Shukor observed Ramadan aboard the International Space Station in 2007.
From there, the crescent Moon fattens, meeting up with Saturn and Spica on the evenings of July 15th and 16th. The Moon will actually occult (pass in front of) the bright star Spica on the evening of July 15/16th at ~3:33UT/11:33PM EDT (on the 15th) for observers in Central America and western South America. The rest of us will see a near miss worldwide.
This is the 13th in a cycle of 18 occultations of Spica by our Moon spanning 2012-2013. Spica is one of four stars brighter than magnitude +1.4 that lie close enough to the ecliptic to be occulted by our Moon, the others being Antares, Regulus and Aldebaran. Saturn will lie 3 degrees from the Moon on the evening of July 16th.
Can you nab Spica and Saturn near the Moon with binoculars in the daytime around the 15th? It can be done, using the afternoon daytime Moon as a guide. Crystal clear skies (a rarity in the northern hemisphere summertime, I know) and physically blocking the Sun behind a building or hill helps.
The waxing gibbous Moon will also occult +2.8 Alpha Librae for South Africa on July 17th around 17:09UT & +4.4th magnitude Xi Ophiuchi for much of North America on the night of July 19th-20th.
And speaking of Regulus, the brightest star in the constellation Leo lies only a little over a degree (two Full Moon diameters) from Venus only the evenings of July 21st & the 22nd. 77.5 light years distant, Regulus is currently over 100 times fainter at magnitude +1.4. Can you squeeze both into the field of view of your telescope at low power? Venus’s mythical ‘moon’ Neith lives!
Venus can even occult Regulus on rare occasions, as last occurred on July 7th, 1959 and will happen next on October 1st, 2044.
But there’s morning action afoot as well. The planets Mars and Jupiter have emerged from solar conjunction on April 18th and June 19th, 2013 respectively, and can now be seen low in the dawn skies about 30 minutes before sunrise.
Mars approaches Jupiter in the dawn until the pair is only 0.79 degrees (about 48 arc minutes) apart on Monday, July 22nd. Mars shines at magnitude +1.6 and shows a tiny 3.9” disk, while Jupiter displays a 32.5” disk shining at magnitude -1.9 on this date. Conjunction occurs at about 7:00 UT/3:00 AM EDT, after which the two will begin to race apart. Mercury is visible beginning its morning apparition over 5 degrees to the lower right of the pair (see above).
Jupiter will reach opposition and reenter the evening sky on January 5th, 2014, while Mars won’t do the same until April 8th of next year. Weird factoid alert: neither Jupiter or Mars reach opposition in 2013! What effect does this have on terrestrial affairs? Absolutely none, well unless you’re a planetary imager/observer…
Mars also reaches its most northern declination of 2013 of 24 degrees in the constellation Gemini on July 16th at 7:00 AM EDT/11:00 UT. Mars can wander as far as declination 27 degrees north, as last happened in 1993.
Finally, are you observing from southern Mexico this week and up for a true challenge? The asteroid 238 Hypatia occults a +7.4 magnitude star from 10:13-10:49 UT on July 10th in the constellation Pisces for up to 29 seconds. This event will be bright enough to watch with binoculars- check out our best prospects for asteroid occultations of stars in 2013 here and here.
Good luck, clear skies, and be sure to post those astro-pics in the Universe Today’s Flickr community!
Are you ready for a weekend observing treat? Then get out your binoculars, telescopes, or just your eyes as the Moon passes over a bright star. Who, what, when and where? Come on inside and find out…
On September 3, 2001 the dark limb of the Moon will encounter 2.3 magnitude Delta Scorpii. The event can be seen from the eastern and southern United States to northern Venezuela. But don’t be discouraged if you aren’t right in that “zone”. For observers from roughly New York City through central Texas to Baja California, you’ll have an event called a “graze” – where the star will appear to slide along the edge – or just be mighty close.
When do you need to observe? Thankfully the event takes place in the early evening, starting around 10:30 p.m. Eastern Daylight Savings time. But don’t wait until that moment to begin your observations! Get your equipment set up in advance and consult with this IOTA page for precise times and locations.
What do you need to observe an occultation? In this circumstance, the Moon isn’t quite half lit, so the glare won’t be so bad that you can’t observe with your eyes alone. However, a pair of binoculars or a small telescope will make the event far more interesting! For even more fun, take along an accurate watch and time it yourself. If you are in the occultation path, watch to see if Delta disappears and reappears behind a crater rim. Then watch as the whole scene shifts west and the star emerges again!