An ancient comet that has been moving through the solar system since discovery last year reached perihelion Thursday and observers are speculating that the sun’s heat is breaking it up.
Comet ISON arrived at the point in its orbit closest to the sun at 18:25 UT Thursday (11:25 am MST).
At perihelion the comet is about 730,000 miles from our star. It has brightened considerably as it approached the sun, reaching a magnitude similar to the full moon.
Emily Lakdawalla and Bruce Betts of the Planetary Society are blogging about the event here.
You can see images obtained by NASA’s Solar Dynamics Observatory here.
Intrepid early risers have the chance for a spectacular sky reward this weekend: seeing comet ISON.
After a journey that has lasted at least one million years, Comet C-2012 S1 ISON will reach perihelion on Nov. 28. That means now is a good time to see the fireball.
Before dawn on Sunday, Nov. 25, the comet will be visible low on the southeastern horizon.
ISON originated in the Oort cloud, far beyond Neptune’s orbit.
If the comet survives its trip around the sun, Earth dwellers may be able to see it again in early December. But that is not certain, because ISON will be only about three-quarters of a million miles above the sun’s surface when it is as close to our star as it will get.
Comets are tiny, generally no more than about 10 kilometers across, and they are constructed mostly of ice and dust. That means the sun’s heat can easily destroy them.
ISON’s nucleus is only about 6.5 kilometers across. It has a tail that extends at least 90,000 kilometers behind it.
Observers first noticed comet ISON last November, when it was more than 500 million miles away from the sun. It has never before completed an orbit around the sun, which means that the comet contains material dating to the formation of the solar system.
NASA has put together a helpful timeline of ISON’s journey through the solar system. Check it out!
It’s always fun to look up at Earth’s closest neighbor and indulge some curiosity about the Moon, but tonight’s a special night to do it: it’s International Observe the Moon Night.
The celebration, sponsored by an array of scientific and educational organizations along with some dedicated Moon enthusiasts, has prompted a wide variety of events all over the world. You can find one near your home if you visit this webpage.
If you’re looking for your own activities, obviously a good place to start is by going outside and observing Luna. You don’t even need a telescope. If the night sky is clear, the naked eye will allow you a good view of lunar maria, or “seas,” and the Moon’s highlands.
If you use binoculars, attach them to a stand or tripod if you have one.
The Moon is at first quarter phase tonight, so it is not likely that an observer will be able to see the phenomenon known as Earthshine, in which the night side of the moon is visible when sunlight reflects off the surface of Earth. Earthshine is visible only when the Moon is at or near new moon phase.
After you’ve looked at the Moon, it might be fun to try your hand at this Mission Moon activity. Participants work in teams to figure out the best place on Luna for a base. The activity is suitable for kids from about third grade and up. You can also try the Moon Mappers activity.
Before going outside to have a look at our closest celestial neighbor, you might enjoy watching this NASA video about how the Moon formed and its history.
Note: This story also appears at Examiner.com.
Scientists have found, for the first time, evidence of water on a rocky celestial body outside of our solar system.
The study focused on dust and debris found orbiting a white dwarf star about 170 million light years away.
“This planetary graveyard swirling around the embers of its parent star is a rich source of information about its former life,” Boris Gaensicke, a professor of physics at the University of Warwick in the United Kingdom, said. “In these remnants lie chemical clues which point towards a previous existence as a water-rich terrestrial body.”
“Those two ingredients — a rocky surface and water — are key in the hunt for habitable planets outside our solar system so it’s very exciting to find them together for the first time outside our solar system.”
The debris probably came from a planet with a diameter of at least 90 kilometers. The planet may have been much bigger than that, but scientists are limited in their ability to estimate its size by the amount of debris that can now be detected.
Oxygen signatures in the debris indicates that the planet would have been, as a proportion of its mass, about 26 percent water.
Water accounts for about 0.023 percent of Earth’s mass.
Scientists had earlier found evidence of water outside our solar system in gas giants. This discovery is significant because it is the first indication that water may be found on rocky exoplanets.
A possible parallel in our solar system is the dwarf planet Ceres, which has ice buried under its crust.
The star around which the debris is accumulated, GD 61, once hosted a planetary system. It became a white dwarf about 200 million years ago.
The discovery of the GD 61 system planetary remnants is the twelfth known example of planetary fragments circling a white dwarf elsewhere in our galaxy.
Researchers used the Hubble Space Telescope and the large Keck Telescope in Hawaii to make the observations in the study.
The paper can be found here.
Artist’s conception (c) Mark A. Garlick, courtesy University of Warwick and University of Cambridge.
Note: A version of this story has also been published at Examiner.com.
The solar system’s seventh planet, Uranus, recently was at opposition from Earth and is currently visible with binoculars if you know where to look in the night sky.
You’ll want to look near the border of the constellations Pisces and Cetus. This Universe Today report should help.
The best time to observe is around midnight local time.
This image of Uranus was obtained by the Voyager 2 spacecraft in 1986. The blue-green color is the result of the presence of methane in the planet’s atmosphere. Courtesy Wikimedia.
The Nobel prize in physics has been awarded to the scientists who predicted the existence of the Higgs boson nearly 40 years ago.
Francois Englert and Peter Higgs were granted the coveted award this morning by the Royal Swedish Academy of Sciences.
They separately proposed, way back in 1964, that a particle we now know as the Higgs boson allows matter to acquire mass. The existence of that particle was confirmed in 2012 by scientists working at the CERN laboratory in Switzerland.
The Draconid meteor shower will again be visible tonight in the northern hemisphere.
The meteor shower occurs when dust from Comet Giacobini-Zinner enters Earth’s atmosphere and ionizes, creating a “shooting star” look.
The meteors appear to come out of the constellation Draco (the dragon) and the flurry of them will appear highest in the sky shortly after sunset. As night advances the spectacle drops below the horizon.
The Draconids can be unpredictable in their intensity. Astronomers have not predicted a noteworthy display from the Draconids this year, but in some years the number of meteors is impressive. In 2011 more than 600 per hour were visible.
The reason for 2011′s display was that Comet Giacobini-Zimmer was at the perihelion of its orbit around the sun.
Earth’s moon is not likely to be much of an impediment to viewing the meteors, as it is in waxing crescent phase now.
Observers will have the best opportunity to see meteors if they choose a viewing location far from city lights.
Graphic courtesy EarthSky.org.