Category: Comets

I wanted to see it myself before I said anything – but now it’s confirmed. Comet W1 Boattini is now visible in the northern hemisphere! So what if you have to get up before dawn? While its overall brightness is good enough to be seen with the unaided eye, I needed a lot of help, and maybe you’d like some, too?

Make no mistake. Fresh from its trip around the Sun and still holding a respectable 5.5 magnitude puts Comet W1 Boattini right in the ballpark of being visible without optical aid, but its size makes it invisible against dawn’s glow. But don’t be discouraged. If you have a decent southeastern skyline, you can catch Boattini with even small binoculars!

Let the one thing you can’t miss in the sky by your guide – the Pleiades. The view you see here is roughly what your horizon will look like before dawn. Although your own local time will vary a bit, that’s about 4:30 – 5:00 a.m. here. Take your binoculars out with you and begin scanning along the horizon for the Pleiades. Once you find them, locate Alpha Ceti. How can you be sure? It’s easy. Menkar is an optical double. Now begin looking with Menkar to the right of your field of view and scan slowly towards the Pleiades. Comet W1 Boattini will pop out and look like a small, unresolved globular cluster! It’s not big, and it doesn’t have a tail – but it sure is sweet.

If you’re good with sky charts, use this to help aid you. This is the rough track that Boattini will be following for the next few weeks – but don’t wait around to find it. In just a few days the Moon will also begin to interfere with the morning darkness and your chances of easily spotting the comet are going to become less. Once you locate it in binoculars, it’s easy to pick it up again in an optical finder on a telescope and take a closer look.

Good luck!

Many thanks to Joe Brimacombe and Guilherme Venere for the W1 Boattini images!

On June 25th, the ESA/NASA SOHO spacecraft discovered its 1,500th comet, making it more successful than all other comet discoverers throughout history, combined. But wait a minute, SOHO is the Solar and Heliospheric Observatory, designed to study solar physics. What’s it doing looking for comets? SOHO just happens to have a great vantage point to see comets as they approach the sun. Since its orbit is situated between the Sun and Earth, it has a unique view of the regions close to the sun that we can rarely see from Earth. But SOHO’s comet-finding success is just an added benefit to the extraordinary revelations this spacecraft has provided in its 13 years in space, observing the Sun and the near-Sun environment. “Catching the enormous total of comets has been an unplanned bonus,” said Bernhard Fleck, ESA SOHO Project Scientist.

About 85% of SOHO’s comet discoveries are fragments from a once-great comet that split apart in a death plunge around the Sun, probably many centuries ago. The fragments are known as the Kreutz group, which now pass within 1.5 million km of the Sun’s surface when they return from deep space.

That’s pretty close in celestial terms, and from Earth, we can only see those regions close to the Sun during an eclipse.

But that also puts them within sight of SOHO’s electronic eyes. Images of the comets are captured by the Large Angle and Spectrometric Coronograph (LASCO), one of 12 instruments on board.

Of course, LASCO itself does not make the detections; that task falls to an open group of highly-skilled volunteers who scan the data as soon as it is downloaded to Earth. Once SOHO transmits to Earth, the data can be on the Internet and ready for analysis within 15 minutes.

Enthusiasts from all over the world look at each individual image for a tiny moving speck that could be a comet. When someone believes they have found one, they submit their results to Karl Battams at the Naval Research Laboratory, Washington DC, who checks all of SOHO’s findings before submitting them to the Minor Planet Center, where the comet is cataloged and its orbit calculated.

From this mission, and with the public’s help, scientists have learned a great deal about comets.

“This is allowing us to see how comets die,” says Battams. When a comet constantly circles the Sun, it loses a little more ice each time, until it eventually falls to pieces, leaving a long trail of fragments. Thanks to SOHO, astronomers now have a plethora of images showing this process. “It’s a unique data set and could not have been achieved in any other way,” says Battams.

Most of the comet fragments are eventually destroyed when they get close enough to the Sun, evaporated by the Sun’s radiation.

Interested in helping search for SOHO’s comets? Visit the Sungrazing comets page.

Original News Source: ESA

Astoundingly, about 40,000 tons of dust particles fall to Earth each year which originates from space “leftovers,” mostly from disintegrating comets and asteroid collisions. Scientists are very interested in this dust because of its pristine nature –it is made of the original building blocks of the solar system. Some of that dust also resides in Earth’s atmosphere, and for years, NASA has routinely collected cosmic and interplanetary dust from Earth’s stratosphere with high-altitude research aircraft. NASA announced today that a new mineral has been found from this atmospheric research, in material that likely came from a comet.

Usually, any unique dust particles found in the atmosphere are difficult to trace as far as their origin, and whether it came from a comet or other space debris. But this new mineral, a manganese silicide which has been named “Brownleeite,” was discovered within an interplanetary dust particle, or IDP, that appears to have originated from comet 26P/Grigg-Skjellerup. The comet was discovered in 1902 and reappears every 5 years. A new method of collecting IDPs was suggested by space scientist Scott Messenger, from Johnson Space Center. He predicted comet 26P/Grigg-Skjellerup was a source of dust grains that could be captured in Earth’s stratosphere at a specific time of the year.

In response to his prediction, NASA performed stratospheric dust collections, using an ER-2 high-altitude aircraft flown from NASA’s Dryden Flight Research Center at Edwards Air Force Base, Calif. The aircraft collected IDPs from this particular comet stream in April 2003. The new mineral was found in one of the particles. To determine the mineral’s origin and examine other dust materials, a powerful new transmission electron microscope was installed in 2005 at Johnson.

“When I saw this mineral for the first time, I immediately knew this was something no one had seen before,” said Keiko Nakamura-Messenger, also from Johnson Space Center. “But it took several more months to obtain conclusive data because these mineral grains were only 1/10,000 of an inch in size.”

“Because of their exceedingly tiny size, we had to use state-of-the-art nano-analysis techniques in the microscope to measure the chemical composition and crystal structure of Keiko’s new mineral,” said Lindsay Keller, Johnson space scientist and a co-discoverer of the new mineral. “This is a highly unusual material that has not been predicted either to be a cometary component or to have formed by condensation in the solar nebula.”

The mineral was surrounded by multiple layers of other minerals that also have been reported only in extraterrestrial rocks. There have been 4,324 minerals identified by the International Mineralogical Association, or IMA. This find adds one more mineral to that list.

Brownleeite, is named after Donald E. Brownlee, professor of astronomy at the University of Washington, Seattle. Brownlee founded the field of IDP research. The understanding of the early solar system established from IDP studies would not exist without his efforts. Brownlee also is the principal investigator of NASA’s Stardust mission.

Brownlee says he’s always been intrigued by minerals and now “it’s great to be one.”

Original News Source: PhysOrg, AP

Who can forget last October, when astronomers all over the world were astounded by the huge outburst of Comet Holmes? The eruption was the largest for more than a century. (Click on image to animate.) Fortunately for the world, a UK telescope was in the right place and the right time to capture the first images of this once-in-a-lifetime event.

The SuperWASP-North facility on the island of La Palma was built by UK scientists to discover planets around other stars. The 8 cameras that make up the system operate robotically, automatically scanning large areas of the sky each night. By coincidence, at 2339 GMT on the evening of 24 October 2007, it was pointing towards Comet 17P Holmes.

“By the time SuperWASP spotted the comet, it had already brightened by a factor of 1000” explains Dr. Henry Hsieh. “But this was still almost 3 hours before anyone else noticed it.” (The lucky astronomer and the honor belongs to amateur astronomer Juan Antonio Henriquez Santana who saw the eruption from Tenerife. Score a point for those of us who scan the skies!). Over the next 2 hours the comet continued brightening, until SuperWASP could no longer accurately measure it – it was too bright for the cameras.

Orbiting the Sun, comets are mainly composed of frozen gases and microscopic solid particles in a small solid nucleus. As they pass by our solar system’s nearest star, they heat up, releasing gas pockets and other frozen materials. Most of us understand outgassing and the properties of cometary tails, but during this outburst, Comet Holmes released a large amount of its material all at once.

Two days after the eruption began, sunlight reflecting from the ejected material had made the comet one million times brighter than it was originally making it easily visible to observers across the northern hemisphere. Dr. Hsieh comments:

“Over the next few weeks, SuperWASP continued to observe Comet Holmes as the cloud of dust and gas surrounding the 3-km diameter nucleus of the comet steadily expanded. By 31st October, the cloud was already 900,000 km across or more than twice the distance from the Earth to the Moon. Using our SuperWASP observations, we measured the speed of expansion of the outer edge of this cloud to be over 1500 km per hour and by 17 November measured the size of the cloud to be more than 2 million km across – much larger than the Sun.”

Two weeks after the outburst, SuperWASP scored again – the faint and delicate tail of Comet Holmes composed of the gas released from the nucleus. As astronomers watched over the next few weeks, this tail gradually faded and moved away from the comet. Although many images were gathered by astronomers around the world, the precise cause of the outburst is still a mystery. All they know right now is that it happened once before – in 1892 – and may well happen again. Keep watching!

For a little while there, Comet 17P/Holmes was the largest object in the Solar System, flaring up by a factor of over a million. Its cloud of gas and dust expanded outward to cover a diameter of 1.4 million km (870,000 miles) – bigger than the Sun. Well, the party’s over. Comet Holmes is fading away again. But will it follow history and flare up again?

This image of Comet Holmes was captured by the MMT observatory on November 4th, 2007 using an instrument called “Megacam”. This is one of the largest CCD cameras on Earth, putting 36 9-megapixel CCD chips together to form a single array with 300 megapixels.

The camera captured images of the comet with three separate exposures in three colours to produce this full colour image.

If you want to see Holmes before it fades into obscurity again, you’re going to need binoculars. Although it’s still a 3rd magnitude object, and should be visible with the unaided eye, it’s so large in the sky that it’s actually quite faint now.

Astronomers are hoping that it’ll repeat history. During its last outburst back in 1892, the comet underwent a second bright flareup five months after the first one. So, if history is any judge, we might just see the comet brighten again, and we’ll all get another chance to see it before it’s gone for good.

Original Source: CfA News Release