Comet Elenin poses no threat to Earth

Often, comets are portrayed as harbingers of gloom and doom in movies and on television, but most pose no threat to Earth. Comet Elenin, the latest comet to visit our inner solar system, is no exception. Elenin will pass about 22 million miles (35 million kilometers) from Earth during its closest approach on Oct. 16, 2011.

Also known by its astronomical name C/2010 X1, the comet was first detected on Dec. 10, 2010 by Leonid Elenin, an observer in Lyubertsy, Russia, who made the discovery “remotely” using an observatory in New Mexico. At that time, Elenin was about 401 million miles (647 million kilometers) from Earth. Since its discovery, Comet Elenin has – as all comets do – closed the distance to Earth’s vicinity as it makes its way closer to perihelion, its closest point to the sun.

Image: Diagram of the projected course of Comet Elenin
The projected path of Comet Elenin. Trajectory of comet Elenin. Image credit: NASA/JPL-Caltech

NASA scientists have taken time over the last several months to answer your questions. Compiled below are the some of the most popular questions, with answers from Don Yeomans of NASA’s Near-Earth Object Program Office at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and David Morrison of the NASA Astrobiology Institute at the NASA Ames Research Center in Moffett Field, Calif.

Most Popular Questions About Comet Elenin

Q: When will Comet Elenin come closest to the Earth and appear the brightest?

A: Comet Elenin should be at its brightest shortly before the time of its closest approach to Earth on Oct. 16, 2011. At its closest point, it will be 22 million miles (35 million kilometers) from us.

Q: Will Comet Elenin come close to the Earth or between the Earth and the moon?

A: Comet Elenin will not come closer to Earth than 22 million miles (35 million kilometers). That’s more than 90 times the distance to the moon.

Q: Can this comet influence us from where it is, or where it will be in the future? Can this celestial object cause shifting of the tides or even tectonic plates here on Earth?

A: There have been incorrect speculations on the Internet that alignments of comet Elenin with other celestial bodies could cause consequences for Earth and external forces could cause comet Elenin to come closer. “Any approximate alignments of comet Elenin with other celestial bodies are meaningless, and the comet will not encounter any dark bodies that could perturb its orbit, nor will it influence us in any way here on Earth,” said Don Yeomans, a scientist at NASA JPL.

“Comet Elenin will not only be far away, it is also on the small side for comets,” said Yeomans. “And comets are not the most densely-packed objects out there. They usually have the density of something akin to loosely packed icy dirt.

“So you’ve got a modest-sized icy dirtball that is getting no closer than 35 million kilometers (about 22 million miles),” said Yeomans. “It will have an immeasurably miniscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”

Q: I’ve heard about three days of darkness because of Comet Elenin. Will Elenin block out the sun for three days?

A: “As seen from the Earth, comet Elenin will not cross the sun’s face,” says Yeomans.

But even if it could cross the sun, which it can’t, astrobiologist David Morrison notes that comet Elenin is about 2-3 miles (3-5 kilometers) wide, while the sun is roughly 865,000 miles (1,392,082 kilometers) across. How could such a small object block the sun, which is such a large object?

Let’s think about an eclipse of the sun, which happens when the moon appears between the Earth and the sun. The moon is about 2,500 miles (4,000 kilometers) in diameter, and has the same apparent size as the sun when it is about 250,000 miles (400,000 kilometers) away — roughly 100 times its own diameter. For a comet with a diameter of about 2-3 miles (3-5 kilometers) to cover the sun it would have to be within 250 miles (400 kilometers), roughly the orbital altitude of the International Space Station. However, as stated above, this comet will come no closer to Earth than 22 million miles.

Q: I’ve heard there is a “brown dwarf” theory about Comet Elenin. Would its mass be enough to pull Comet Honda’s trajectory a significant amount? Could this be used to determine the mass of Elenin?

A: Morrison says that there is no ‘brown dwarf theory’ of this comet. “A comet is nothing like a brown dwarf. You are correct that the way astronomers measure the mass of one object is by its gravitational effect on another, but comets are far too small to have a measureable influence on anything.”

Q: If we had a black or brown dwarf in our outer solar system, I guess no one could see it, right?

A: “No, that’s not correct,” says Morrison. “If we had a brown dwarf star in the outer solar system, we could see it, detect its infrared energy and measure its perturbing effect on other objects. There is no brown dwarf in the solar system, otherwise we would have detected it. And there is no such thing as a black dwarf.”

Q: Will Comet Elenin be visible to the naked eye when it’s closer to us? I missed Hale-Bopp’s passing, so I want to know if we’ll actually be able to see something in the sky when Elenin passes.

A: We don’t know yet if Comet Elenin will be visible to the naked eye. Morrison says, “At the rate it is going, seeing the comet at its best in early October will require binoculars and a very dark sky. Unfortunately, Elenin is no substitute for seeing comet Hale-Bopp, which was the brightest comet of the past several decades.”

“This comet may not put on a great show. Just as certainly, it will not cause any disruptions here on Earth. But, there is a cause to marvel,” said Yeomans. “This intrepid little traveler will offer astronomers a chance to study a relatively young comet that came here from well beyond our solar system’s planetary region. After a short while, it will be headed back out again, and we will not see or hear from Elenin for thousands of years. That’s pretty cool.”

Q: This comet has been called ‘wimpy’ by NASA scientists. Why?

A: “We’re talking about how a comet looks as it safely flies past us,” said Yeomans of NASA’s Near-Earth Object Program Office. “Some cometary visitors arriving from beyond the planetary region – like Hale-Bopp in 1997 — have really lit up the night sky where you can see them easily with the naked eye as they safely transit the inner-solar system. But Elenin is trending toward the other end of the spectrum. You’ll probably need a good pair of binoculars, clear skies and a dark, secluded location to see it even on its brightest night.”

Q: Why aren’t you talking more about Comet Elenin? If these things are small and nothing to worry about, why has there been no public info on Comet Elenin?

A: Comet Elenin hasn’t received much press precisely because it is small and faint. Several new comets are discovered each year, and you don’t normally hear about them either. The truth is that Elenin has received much more attention than it deserves due to a variety of Internet postings that are untrue. The information NASA has on Elenin is readily available on the Internet. (See http://www.jpl.nasa.gov/news/news.cfm?release=2011-135) If this comet were any danger to anyone, you would certainly know about it. For more information, visit NASA’s AsteroidWatch site at http://www.jpl.nasa.gov/asteroidwatch/.

Q: I’ve heard NASA has observed Elenin many times more than other comets. Is this true, and is NASA playing this comet down?

A: NASA regularly detects, tracks and characterizes asteroids and comets passing relatively close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them and predicts their paths to determine if any could be potentially hazardous to our planet. For more information, visit the NASA-JPL Near Earth objects site at http://neo.jpl.nasa.gov/ .

However, neither NASA nor JPL is in the business of actively observing Elenin or any other comet. Most of the posted observations are made by amateur astronomers around the world. Since Elenin has had so much publicity, it naturally has attracted more observers.

Q: I was looking at the orbital diagram of Comet Elenin on the JPL website, and I was wondering why the orbit shows some angles when zooming? If you pick any other comet, you can see that there are no angles or bends.

A: Many people are trying to plot the orbit of the comet with the routine on the JPL website, without realizing that this is just a simple visualization tool. While the tool has been recently improved to show smoother trajectories near the sun, it is not a scientific program to generate an accurate orbit. Yeomans explains that the orbit plotter on the Near-Earth Object website is not meant to accurately depict the true motion of objects over long time intervals, nor is it accurate during close planetary encounters. For more accurate long-term plotting, Yeomans suggests using the JPL Horizons system.

From a NASA Jet Propulsion Laboratory news release.

Oppy reaches Endeavour Crater

Photo: Edge of Endeavour Crater on planet Mars.
NASA's Mars Exploration Rover Opportunity arrived at the rim of Endeavour crater on Aug. 9, 2011, after a trek of more than 13 miles (21 kilometers) lasting nearly three years. Image Credit: NASA/JPL-Caltech/Cornell/ASU. (Click on image to see full-size.)

PASADENA, Calif. – After a journey of almost three years, NASA’s Mars Exploration Rover Opportunity has reached the Red Planet’s Endeavour Crater to study rocks never seen before.

On Aug. 9, the golf cart-sized rover relayed its arrival at a location named Spirit Point on the crater’s rim. Opportunity drove approximately 13 miles (21 kilometers) since climbing out of the Victoria Crater.

“NASA is continuing to write remarkable chapters in our nation’s story of exploration with discoveries on Mars and trips to an array of challenging new destinations,” NASA Administrator Charles Bolden said. “Opportunity’s findings and data from the upcoming Mars Science Laboratory will play a key role in making possible future human missions to Mars and other places where humans have not yet been.”

Endeavour Crater, which is more than 25 times wider than Victoria Crater, is 14 miles (22 kilometers) in diameter. At Endeavour, scientists expect to see much older rocks and terrains than those examined by Opportunity during its first seven years on Mars. Endeavour became a tantalizing destination after NASA’s Mars Reconnaissance Orbiter detected clay minerals that may have formed in an early warmer and wetter period.

“We’re soon going to get the opportunity to sample a rock type the rovers haven’t seen yet,” said Matthew Golombek, Mars Exploration Rover science team member, at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “Clay minerals form in wet conditions so we may learn about a potentially habitable environment that appears to have been very different from those responsible for the rocks comprising the plains.”

The name Spirit Point informally commemorates Opportunity’s twin rover, which stopped communicating in March 2010. Spirit’s mission officially concluded in May.

Geauga’s Observatory Park grand opening August 20

Photo: Oberle Observatory in Geauga Park District's Observatory Park. Photo by James Guilford.
Oberle Observatory in Geauga Park District's Observatory Park. Photo by James Guilford.

A special evening of activities is planned marking the 50th anniversary of the Geauga Park District. The event also serves as the public’s first viewing of its newest park, Observatory Park. Plans call for everything to get underway at 4:00 PM with a park dedication and ribbon-cutting ceremony. Tours, entertainment, a hot dog dinner, and evening concert are planned. The evening culminates in a first-light ceremony at the new Oberle Observatory itself. Click here for the full schedule of events.

9:15 PM: “First Light Ceremony” Dedication and Ribbon-Cutting of the Oberle Observatory and Telescope. The Newtonian reflector boasts a universe-grabbing 25.5-inch mirror created by legendary local astronomer Norman Oberle. Sandy Oberle donated her late husband’s telescope to the Geauga Park District to continue his legacy by opening the heavens to the public. The ceremony will feature the Chagrin Valley Astronomical Society’s Ian Cooper and Sandy Oberle.

9:15 PM – Midnight: Stargazing hosted by the Chagrin Valley Astronomical Society.

Observatory Park, 10610 Clay Street, Montville Township
Event Open to the Public • Free Entertainment and Education for All Ages • Registration is not required. Call: (440) 286-9516 with questions.

Geomagnetic storm expected

NOAA Space Weather Bulletin August 4, 2011
NOAA Region 1261, very active over the past few days, produced the third of a sequence of Coronal Mass Ejections (CMEs) and Solar Radio Blackout Events early today. The net effect of that activity is convergent CMEs expected to disturb the geomagnetic field in the early hours, Universal Time (UTC) of August 5. G3 (Strong) Geomagnetic Storm conditions are likely as well as a distinct chance of S2 (Moderate) Solar Radiation Storm levels being surpassed.

From SpaceWeather.com….
Moving at an estimated speed of 1950 km/s, this CME is expected to sweep up two earlier CMEs already en route. Analysts at the GSFC Space Weather Lab say the combined cloud should reach Earth on August 5th at 13:55 UT (9:55 AM EDT) plus or minus 7 hours: “The impact on Earth is likely to be major. The estimated maximum geomagnetic activity index level Kp is 7 (Kp ranges from 0 – 9). The flanks of the CME may also impact STEREO A, Mars and Mercury/MESSENGER.” High-latitude sky watchers should be alert for auroras. Please visit SpaceWeather.com for full details and latest news!

If we happen to have clear(ish) skies Friday night, Aug. 5, it might be worth stepping outside well after twilight and taking a look. You never know, we might get auroras!

2011 Convention a great night

Photo: Sunset over the still lake at park. Photo by James Guilford.
The sun sets on a beautiful day, ushering in a clear night sky full of stars. Photo by James Guilford.

It was a great night at Letha House Park! CAA members and invited astronomy club members from the area gathered under gloriously clear skies for an evening of socializing and a night of excellent observing.

Many thanks to all those who attended this annual event, and to those who brought the good food for the pot luck and helped with its preparation!  Special thanks in this regard to Marianne Wadsworth, who helped VP Mike Williams with her grilling skills.

Board member Tim Campbell brought in all the great-tasting wieners, brats, and sausages for the event at an excellent price.  Our thanks to Bob Guttwein, president of Five Star Brand Meats in Cleveland, who offered the high-quality meat at a steep discount through Tim.

Photo: Lecturer with projected image of Saturn's moon Titan. Photo by James Guilford.
Featured speaker Jay Reynolds talks about the NASA Cassini mission, shown here with a projected image of Saturn's moon Titan. The new facilities at Letha House Park were much appreciated.Photo by James Guilford.

We had visitors from the Black River, Chagrin Valley, and Mahoning Valley clubs.  It was nice to host them!

Many thanks to our secretary, Steve Spears, who got a good supply of door prizes in spite of tight economic conditions. Caffeine kudos to Ray and Lynn Paul, who brought a large coffee pot and fixings for coffee lovers.

Special thanks to Gail Korylak, who helped with the clean-up.  Gail cleaned all the tables, moved all the tables and chairs, and then vacuumed the floor.  Earlier during the dinner, she also set up and arranged the food table.  She did a great job.

Our thanks also, of course, to Jay Reynolds, who gave an interesting talk about Saturn and the Cassini Mission.

Photo: Astronomers setting up telescopes in early twilight. Photo by James Guilford
2011 Convention attendees set up their telescopes under the clear skies of early twilight. Photo by James Guilford.

The recent improvements to the park gave telescope owners the opportunity to park on solid pavement and set up their instruments on earth. Adding to the pleasure was the fact that skies over the park were the best they have been in many a year for the CAA’s event. It was a great night, indeed!

Target Mars: Gale Crater selected for Mars Science Laboratory

Gale crater is 96 miles (154 kilometers) in diameter and holds a layered mountain rising about 3 miles (5 kilometers) above the crater floor. Image Credit: NASA/JPL-Caltech/ASU/UA

PASADENA, Calif. — NASA’s next Mars rover will land at the foot of a layered mountain inside the planet’s Gale Crater. The US space agency made the announcement Friday, July 22.

The car-sized MSL (Mars Science Laboratory), or “Curiosity,” is scheduled to launch late this year and land in August 2012. The target crater spans 96 miles (154 kilometers) in diameter and holds a mountain rising higher from the crater floor than Mount Rainier rises above Seattle. Gale is about the combined area of Connecticut and Rhode Island. Layering in the mound suggests it is the surviving remnant of an extensive sequence of deposits. The crater is named for Australian astronomer Walter F. Gale.

“Mars is firmly in our sights,” said NASA Administrator Charles Bolden. “Curiosity not only will return a wealth of important science data, but it will serve as a precursor mission for human exploration to the Red Planet.”

During a prime mission lasting one Martian year — nearly two Earth years — researchers will use the rover’s tools to study whether the landing region had favorable environmental conditions for supporting microbial life and for preserving clues about whether life ever existed.

“Scientists identified Gale as their top choice to pursue the ambitious goals of this new rover mission,” said Jim Green, director for the Planetary Science Division at NASA Headquarters in Washington. “The site offers a visually dramatic landscape and also great potential for significant science findings.”

In 2006, more than 100 scientists began to consider about 30 potential landing sites during worldwide workshops. Four candidates were selected in 2008. An abundance of targeted images enabled thorough analysis of the safety concerns and scientific attractions of each site. A team of senior NASA science officials then conducted a detailed review and unanimously agreed to move forward with the MSL Science Team’s recommendation. The team is comprised of a host of principal and co-investigators on the project.

Curiosity is about twice as long and more than five times as heavy as any previous Mars rover. Its 10 science instruments include two for ingesting and analyzing samples of powdered rock that the rover’s robotic arm collects. A radioisotope power source will provide heat and electric power to the rover. A rocket-powered sky crane suspending Curiosity on tethers will lower the rover directly to the Martian surface.

The portion of the crater where Curiosity will land has an alluvial fan likely formed by water-carried sediments. The layers at the base of the mountain contain clays and sulfates, both known to form in water.

Dawn: First close-up image of asteroid Vesta

Photo: Image of asteroid Vesta as recorded by the DAWN spacecraft. Credit: NASA
Asteroid Vesta as imaged by the Dawn spacecraft. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

PASADENA, Calif. — NASA’s Dawn spacecraft has returned the first close-up image after beginning its orbit around the giant asteroid Vesta. On Friday, July 15, Dawn became the first probe to enter orbit around an object in the main asteroid belt between Mars and Jupiter.

The image taken for navigation purposes shows Vesta in greater detail than ever before. When Vesta captured Dawn into its orbit, there were approximately 9,900 miles (16,000 kilometers) between the spacecraft and asteroid. Engineers estimate the orbit capture took place at 10 p.m. PDT Friday, July 15 (1 a.m. EDT Saturday, July 16).

Vesta is 330 miles (530 kilometers) in diameter and the second most massive object in the asteroid belt. Ground- and space-based telescopes have obtained images of Vesta for about two centuries, but they have not been able to see much detail on its surface. “We are beginning the study of arguably the oldest extant primordial surface in the solar system,” said Dawn principal investigator Christopher Russell from the University of California, Los Angeles. “This region of space has been ignored for far too long. So far, the images received to date reveal a complex surface that seems to have preserved some of the earliest events in Vesta’s history, as well as logging the onslaught that Vesta has suffered in the intervening eons.”

Vesta is thought to be the source of a large number of meteorites that fall to Earth. Vesta and its new NASA neighbor, Dawn, are currently approximately 117 million miles (188 million kilometers) away from Earth. The Dawn team will begin gathering science data in August. Observations will provide unprecedented data to help scientists understand the earliest chapter of our solar system. The data also will help pave the way for future human space missions.

After traveling nearly four years and 1.7 billion miles (2.8 billion kilometers), Dawn also accomplished the largest propulsive acceleration of any spacecraft, with a change in velocity of more than 4.2 miles per second (6.7 kilometers per second), due to its ion engines. The engines expel ions to create thrust and provide higher spacecraft speeds than any other technology currently available. “Dawn slipped gently into orbit with the same grace it has displayed during its years of ion thrusting through interplanetary space,” said Marc Rayman, Dawn chief engineer and mission manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It is fantastically exciting that we will begin providing humankind its first detailed views of one of the last unexplored worlds in the inner solar system.”

Although orbit capture is complete, the approach phase will continue for about three weeks. During approach, the Dawn team will continue a search for possible moons around the asteroid; obtain more images for navigation; observe Vesta’s physical properties; and obtain calibration data.