Video Courtesy of NASA.
Showing posts with label minor planet. Show all posts
Showing posts with label minor planet. Show all posts
Friday, December 9, 2011
Thursday, October 27, 2011
Occultation of Minor Planet 136199 Eris Gives Significant Data
Last November 6, 2010, minor planet 136199 Eris occulted the star USNOA2 0825-00375767 in the constellation Cetus. What significance does this relate to? Before this occultation, trans-Neptunian object Eris was assumed to be smaller than Pluto, its presumably larger contemporary. But now, Eris' diameter has been measured and not guesstimated, but rather an exact measurement. The video below shows the occultation, as astronomers would have seen it on that November day.
Previously estimated was the diameter of Eris at around 3000 km (or 25% larger than Pluto), but now, the research has proved that both minor planets are essentially the same size, as Eris' predicted diameter was 2326 km. (Pluto's diameter is approximately 2300 or 2400 km, as New Horizons will find out in 2016. Pluto's obstructive atmosphere makes occultation predictions hard to accurately define).
The below picture shows trajectories of the occultation, "the three oblique solid lines show the star trajectories relative to Eris, as seen from San Pedro, La Silla and CASLEO, with the arrow pointing towards the direction of motion," as multiple authors of A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation, a paper presenting their discoveries, write. The names below are observatories in Chile where this occultation was viewed.
“This density means that Eris is probably a large rocky body covered in a relatively thin mantle of ice,” comments Emmanuel Jehin, who contributed to the study. “It is extraordinary how much we can find out about a small and distant object such as Eris by watching it pass in front of a faint star, using relatively small telescopes. Five years after the creation of the new class of dwarf planets, we are finally really getting to know one of its founding members,” concludes Bruno Sicardy.
USNOA2 0825-00375767, with a magnitude of 17.25 is a very faint star, but nothing is too dim for the Belgian TRAPPIST telescope at ESO’s La Silla Observatory to see. This event has been described by ESO as a "very rare and difficult to observe" event becasue minor planets are very small - and an occultation is even rarer. But these things do occur, for Eris will occult again in 2013, ESO reports. Astronomers first observed the star using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory, and a another team carefully predicted the time and what would occur during the occultation. "Observing occultations by the tiny bodies beyond Neptune in the Solar System requires great precision and very careful planning. This is the best way to measure Eris’s size, short of actually going there," explains Bruno Sicardy, the lead author.
Twenty-six places global observed the occultation and were henceforth able to determine the diameter of Eris, which had not yet been accurately determined. Eris is a dwarft planet, today known to be the most massive, of the Kuiper Belt - the region of the solar system which contains the "remains," as astronomers call it. Eris is a dwarf planet, as well as other well-known objects such as Pluto, Sedna, and Makemake. The planet itself is magnitude 18.7 and it orbits 97.56 AU, or 9,068,768,557.0108 miles from earth. It has one moon, Dysnomia, as shown in the picture below. This moon was used to help determine the mass of Eris - which is 27% heavier than Pluto, astronomers found.
 |
| Artist's conception of Eris (with Dysnomia above) |
Previously estimated was the diameter of Eris at around 3000 km (or 25% larger than Pluto), but now, the research has proved that both minor planets are essentially the same size, as Eris' predicted diameter was 2326 km. (Pluto's diameter is approximately 2300 or 2400 km, as New Horizons will find out in 2016. Pluto's obstructive atmosphere makes occultation predictions hard to accurately define).
The below picture shows trajectories of the occultation, "the three oblique solid lines show the star trajectories relative to Eris, as seen from San Pedro, La Silla and CASLEO, with the arrow pointing towards the direction of motion," as multiple authors of A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation, a paper presenting their discoveries, write. The names below are observatories in Chile where this occultation was viewed.
“This density means that Eris is probably a large rocky body covered in a relatively thin mantle of ice,” comments Emmanuel Jehin, who contributed to the study. “It is extraordinary how much we can find out about a small and distant object such as Eris by watching it pass in front of a faint star, using relatively small telescopes. Five years after the creation of the new class of dwarf planets, we are finally really getting to know one of its founding members,” concludes Bruno Sicardy.
Saturday, August 20, 2011
Events for the Week 08/20 through 08/27
From our past weeks of same-old events, we have now decided to do events differently...from weekly viewings, to a Solar-System events Calendar, and from a planet observation line, to a section. Be amazed and observe!
SOLAR-SYSTEM EVENTS FOR THE WEEK OF 08/20 THROUGH 08/27, 2011.
(All times and dates are UT (Universal Time). *This is a major event. ^There will be a post published approx. 1-2 days event occurs.)
SPECIAL VIEWINGS FOR THE WEEK OF 08/20 THROUGH 08/27, 2011.
MOON & PLEIADES CONJUNCTION - Just after the moon is at last quarter, shortly before midnight, the moon will just be about four degrees away from the Pleiades, and will be a remarkable sight: a half lit moon with a cluster not very far away. Jupiter will also conjunct tonight, giving us something like this:
NEPTUNE OPPOSITION - On the night that Neptune is at opposition, astronomers and many other observers will be viewing this distant world at its brightest. At magnitude 7.8 (technically 7.78), Neptune is brighter than its darkest mag 8.02. It will be in the sky the highest at 1 am, but you'll be able to see it around 10 pm. To help locate Neptune, try looking for Iota Aquarii, just 1.6 degrees due south. Remember Neptune's birthday?...
DAWN & VESTA - as NASA probe Dawn is circling the planet, Vesta recently passed opposition and was a great target for many observers August 5. But, still it remains bright and you too can view the protoplanet if you have binoculars, telescope, etc. Come to our Minor Planets Viewing Page, and look under the header titled: "Viewing 1 Ceres and 4 Vesta through the rest of 2011. There is a nice dissertation on how to view them, thanks to Sky&Telescope.
Below is the sky for August 25-27.
PLANET VIEWINGS FOR THE WEEK OF 08/20 THROUGH 08/27, 2011.
Mercury - (NV)* Hidden in the Sun's glare
Venus - (NV) Hidden in the Sun's glare
Mars - (N) magnitude +1.4; constellation: Gemini; up around 2am EDT
Jupiter - (N & D) magnitude -2.6; constellation: south Aires; rises at 11pm, and sets as the Sun rises. Best to view around 1am.
Saturn - (E & N) magnitude +0.9; constellation: Virgo; sinking into the evening, earlier each night.
Uranus - (E & N) magnitude +5.8; constellation: in the Circlet of Pisces
Neptune - (E & N) magnitude +7.78 (opposition this week!); constellation: Aquarius. Both Uranus and Neptune are high before midnight.
Pluto - (N) magnitude +14.0 in Sagittarius.
Minor Planets - come to this page.
*(E) Evening, (N) Night, (D) Dawn, (NV) Not Visible.
Have a great viewing this week!!
SOLAR-SYSTEM EVENTS FOR THE WEEK OF 08/20 THROUGH 08/27, 2011.
19 Aug 2011 01:03:35 Aphelion of Asteroid 2 Pallas, 3.41195 AU from Sun
20 Aug 2011 09:51:38 Conjunction of Jupiter with the Moon, 4.6°
21 Aug 2011 05:45:32 (Quebec, Canada) Stellar Occultation of Delta Aries*^ 21 Aug 2011 21:54:29 Last Quarter
22 Aug 2011 04:00:00 Moon Conjunction with the Pleiades, 4°
22 Aug 2011 06:36:32 (Washington DC) Stellar Occultation 37 Taurus*^
22 Aug 2011 09:21:49 Closest Approach of Neptune, 28.99519 AU from Earth
22 Aug 2011 23:25:59 Opposition of Neptune, 7.8m*
23 Aug 2011 12:19:52 Max. South Declination of the Moon, 23.1°
23 Aug 2011 17:23:27 Descending Knot Passage of the Moon
25 Aug 2011 12:38:46 Conjunction of Mars with the Moon, 2.6°
26 Aug 2011 04:04:34 Mercury stationary: getting prograde
27 Aug 2011 04:15:07 Max. South Declination of Jupiter, 13.6°
27 Aug 2011 23:32:17 Conjunction of Mercury with the Moon, 2.4°
(All times and dates are UT (Universal Time). *This is a major event. ^There will be a post published approx. 1-2 days event occurs.)
SPECIAL VIEWINGS FOR THE WEEK OF 08/20 THROUGH 08/27, 2011.
MOON & PLEIADES CONJUNCTION - Just after the moon is at last quarter, shortly before midnight, the moon will just be about four degrees away from the Pleiades, and will be a remarkable sight: a half lit moon with a cluster not very far away. Jupiter will also conjunct tonight, giving us something like this:
OR
NEPTUNE OPPOSITION - On the night that Neptune is at opposition, astronomers and many other observers will be viewing this distant world at its brightest. At magnitude 7.8 (technically 7.78), Neptune is brighter than its darkest mag 8.02. It will be in the sky the highest at 1 am, but you'll be able to see it around 10 pm. To help locate Neptune, try looking for Iota Aquarii, just 1.6 degrees due south. Remember Neptune's birthday?...
DAWN & VESTA - as NASA probe Dawn is circling the planet, Vesta recently passed opposition and was a great target for many observers August 5. But, still it remains bright and you too can view the protoplanet if you have binoculars, telescope, etc. Come to our Minor Planets Viewing Page, and look under the header titled: "Viewing 1 Ceres and 4 Vesta through the rest of 2011. There is a nice dissertation on how to view them, thanks to Sky&Telescope.
Below is the sky for August 25-27.
PLANET VIEWINGS FOR THE WEEK OF 08/20 THROUGH 08/27, 2011.
Mercury - (NV)* Hidden in the Sun's glare
Venus - (NV) Hidden in the Sun's glare
Mars - (N) magnitude +1.4; constellation: Gemini; up around 2am EDT
Jupiter - (N & D) magnitude -2.6; constellation: south Aires; rises at 11pm, and sets as the Sun rises. Best to view around 1am.
Saturn - (E & N) magnitude +0.9; constellation: Virgo; sinking into the evening, earlier each night.
Uranus - (E & N) magnitude +5.8; constellation: in the Circlet of Pisces
Neptune - (E & N) magnitude +7.78 (opposition this week!); constellation: Aquarius. Both Uranus and Neptune are high before midnight.
Pluto - (N) magnitude +14.0 in Sagittarius.
Minor Planets - come to this page.
*(E) Evening, (N) Night, (D) Dawn, (NV) Not Visible.
Have a great viewing this week!!
Subscribe to:
Posts (Atom)