Archive for October, 2010

The search for binary asteroids in the population of NEAs

Since the beginning of the work at our observatory, one of our basic tasks has been the job of photometric studies of near Earth asteroids (NEAs). At the end of October observations were made of several bright asteroids, including asteroid 3122 Florence which our team has been observing since Summer at several observatories. The asteroid belongs to the Amor group like the first NEA we discovered, 2010 RN80, and is potentially hazardous to our planet (Potentially Hazardous Asteroid, PHA). The period of the asteroid is already precisely known; it is 2.3581 hours. In the graph at left you can see its phase curve from observations obtained October 28-29 at our observatory.

Our main task is the determination of the angle of its rotation axis and, of course, searching for possible satellites. For that it is necessary to determine a second or even third period within the basic one, all tied to the rotation of the main body. For this painstaking work, high precision photometric observations are needed at various phase angles at several oppositions. This is not a task for one year.

Photometry of asteroids is more complex than observing variable stars, as the asteroids move quickly in space, especially near Earth asteroids. Because of that, from night to night, observations are made using different comparison stars, which complicates the task. It is also necessary to calculate the phase angle. Brightness curves obtained on different nights will slightly differ one from another, and to determine a phase curve, it is necessary to take out the brightness differences associated with the spatial effect (distance from the observer, phase angle), but not the rotation of the asteroid on its axis, as well as the possible orbital motion of a satellite.

Here you can become acquainted with the paper about the discovery of the satellite of asteroid 8373 Stephengould.

More detail information about our photometry program you can find on this page.

Impact of large asteroid may cause disruption of Earth ozonosphere

Recently scientists all over the world have presented many models describing a collision of the Earth with an asteroid or a comet. All of us can imagine the consequences of such a collision. That is a powerful impact wave, a huge tsunami from the body falling into the ocean and the so-called “impact” winter and “firey” rain consisting of material from the Earth’s crust blasted to the edge of the atmosphere with a subsequent rain of meteors back to the Earth. All these scenarios are possible with the falling of a large body similar to that which possibly killed off the dinosaurs at the Cretaceous-Tertiary boundary (the so-called K-T Event).

Is this all we can expect from such a catastrophic scenario? Or do we need to prepare for something more? As studies by the American scientists of the Planetary Science Institute (PSI) have shown, one more biosphere-destroying event will be the destruction of the planet’s ozone layer. The group, under the direction of Elizabeth Pierazzo, generated two models describing the fall of asteroids 500 and 1000 meters in diameter into the ocean (depth of 4000 meters). From their analysis of the data the scientists came to some conclusions about the catastrophic consequences of the ejection of huge quantities of hot water vapor into the atmosphere. After the water vapor, the liberation of huge volumes of chlorides and bromides will continue the process of destroying the ozone layer. As a result of these events, there will be a global exhaustion of the ozone layer, and Earth life will be defenseless for years.

The UVI (ultraviolet index) may be over 20 for several months after Earth is hit by a 500 meter asteroid. A reading of 10 is dangerous to humans, and 20 is the maximum value ever recorded on Earth. Under such radiation, a person can get burned even after only five minutes in the sun. Even more serious are the facts associated with the impact of a kilometer-sized asteroid. The brightness of the ultraviolet radiation will reach a huge value – 56! A person without protection in the open sunlight would literally burn up. The ultraviolet intensity would gradually decrease, but over the course of two years its level would remain over 20.

During this time most of the plant and animal life on Earth would perish; in countries where there are not huge reserves of foodstuffs, hunger would become a problem. All this is without calculating in the catastrophe which a huge tsunami would cause.

All these data are not to scare the people of the Earth, but, instead, they have the purpose of bringing understanding of what we must be prepared for, if we want to preserve our civilization at our modern level of development, and not plunge it into chaos because we couldn’t take a hit from space.

MPC statistic for October 2010

The monthly MPC circular is not released in October.

ISON-NM internal statistic for the previous month (September 17 – October 23):

Number of measurements: 13437

Measured objects: n/a

Discovered objects: 31 (2010 RA180; 2010 TU18; 2010 TY18; 2010 TZ18; 2010 TB47; 2010 TC48; 2010 TO51; 2010 TB58; 2010 TB82; 2010 TU86; 2010 TO104; 2010 TW113; 2010 TW114; 2010 TA121; 2010 TN128; 2010 TT139; 2010 TD142; 2010 TE142; 2010 TU152; 2010 TV161; 2010 TU161; 2010 TL168; 2010 TJ173; 2010 TH173; 2010 TK173; 2010 TY173; 2010 TS174; 2010 UZ5; 2010 UL6; 2010 UT6; 2010 UU6)

Sky coverage: 700 sq. degrees

Observing nights*: 25

* – include partial nights

Further study of P/2010 A2

On October 14 in the journal Nature, there was a scientific paper published on new studies about the nature of comet P/2010 A2 (LINEAR). What exactly is it – a unique main-belt comet, or the result of the first documented collision of two small asteroids?

A little history: the comet was discovered January 6, 2010 by the LINEAR automatic sky survey. After being placed on the confirmation page, it became clear that this was no ordinary object. It was not star-like. Furthermore, it did not have any apparent condensation resembling a cometary nucleus. In images, only a tail was visible, without the comet itself. This made astrometric measurement difficult. Immediately after its discovery, the discussion of the nature of the new comet began. They continue to this day, although everyone is beginning to lean toward the version of a collision of two asteroids, where the tail becomes nothing but a dust tail thrown off as a consequence of the collision.

The collisional nature of the formation of the “comet’s” tail was a result of follow-up studies. The time interval for the collision was determined – January to August of 2009. Additionally, the presence of large particles (diameter greater than 1 mm) was noted in the dust tail. That is rather large for ordinary comet dust tails.

New studies were based on the analysis of new images obtained with the help of the Rosetta spacecraft’s OSIRIS camera. Ground-based observational support was carried out at the 3.6-m NTT telescope (New Technology Telescope) at the ESO La Silla Observatory, and also at the 5-m Hale telescope at Mt. Palomar Observatory.

On the basis of numerical modeling of the ejection of dust particles, with consideration of numerous parameters and comparison of the results with the images, the scientists came to the conclusion that the tail formation happened before August of 2009. The greatest agreement between the calculated data and the images was achieved for a collision date of February 10, 2009 (+/- 5 days). From this model the particle sizes were also refined. The result supported the previous conclusion – the dust tail particles have a large size – from millimeters to centimeters and even larger. On the basis of these data the mass of the ejected material was also calculated – 3.7 x 108 kg, which comprises about 16% of the mass of the 120-m asteroid discovered earlier in the images taken with large telescopes. It is thought that this is one of the colliding asteroids. Most likely, the second, smaller object (probable diameter 6-9 meters), was completely destroyed as a result of the collision.

Based on data about the populations of main-belt asteroids, as well as the sizes of the colliding bodies, some conclusions were drawn about the frequency of collisions for a 120-meter sized asteroid – 1.2 billion years; that is, about one collision in 12 years. Since this collision is the first one documented and studied, with the coming on line of new generation surveys this figure will steadily grow.

Pan-STARRS – the first comet of new generation sky survey

The promising all-sky survey PanSTARRS (Panoramic Survey Telescope & Rapid Response System), having finally started regular observations, discovered its first comet October 6th! The short-period comet of the Jovian family received the designation P/2010 T2 (PANSTARRS) and, in principle, nothing special stands out about this comet. The comet’s period is approximately 13.2 years; its orbital inclination is small, on the order of 8 degrees. The comet will reach perihelion at the end of July 2011, and the new comet’s minimum distance from Earth will be October 14th (4.5132 a.u.). The comet’s brightness will not exceed 20th magnitude.

After the future comet was placed on the MPC Confirmation page, observations of the new object were carried out by two large telescopes – the Kitt Peak 2.3 meter reflector, and the one-meter telescope of the Japanese observatory Bisei Spaceguard Center.

October 2010
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