Encuentran los trozos del 2008 TC3

[gustavo muler]

les pongo aqui enlaces de la noticia...

http://www.astronomy.com/asy/default.aspx?c=a&id=8061

http://www.nytimes.com/2009/03/26/scien ... id.html?em

http://www.livescience.com/space/090325 ... rites.html

http://www.nasa.gov/topics/earth/tc3

:onfire:

http://www.elperiodico.com/default.asp?idpublicacio_PK=46&idioma=CAS&idnoticia_PK=598509&idseccio_PK=1021&h

[Alejandro]

que buena noticia, ademas los felicito (especialmente a vos) ya que tienen un reconocimiento por el seguimiento del objeto en cuestion en el articulo de elperiodico.com

esta mas que demostrado el aporte que uno puede hacer como aficionado.

un merito al empeño que le ponen dia a dia.

suerte

[Baxter]

felicidades Ramon y Gustavo!

[gustavo muler]

te pongo aquí la copia del cálculo del período de rotación, hecho por un astrofísico brasileño.

bueno, está en inglés, espero sirva para algo.

es el minor planet center bulletin 36

PHOTOMETRIC OBSERVATIONS OF EARTHIMPACTING

2008 TC3

Alberto Silva Betzler, Alberto Brum Novaes

Projeto “Descobrindo o Céu”

Departamento de Física da Terra e do Meio Ambiente

Instituto de Física, Universidade Federal da Bahia (IF-UFBA)

Salvador, Estado da Bahia, BRASIL

Paolo Beltrame

Circolo AStrofili Talmassons (C.AS.T) Observatory, Talmassons,

Udine, ITALY

Ramon Naves

Montse Campàs, Montcabrer – Cabrils Obervatory

Barcelona, SPAIN

Gustavo Muler

Nazaret Observatory

Nazaret, Canary Islands, SPAIN

(Received: 2008 Nov 30 Revised: 2008 Dec 23)

Apollo NEA 2008 TC3 collided with Earth in a deserted

region of Sudan on 2008 Oct. 7 UT. Based on our

observations and assuming G = 0.2, we found an

absolute magnitude H = 30.79 ± 0.08. With our H value

and pV = 0.09, we estimate the diameter of 2008 TC3 to

be D = 3 ± 1 m. Our period analysis of the lightcurve,

which assumed a single period, found periods 97.05 s or

194.34 s. These do not account for the tumbling nature

confirmed by Pravec and Harris using other data and so

probably do not indicate the true rotation characteristics

of the object.

The Apollo near-Earth asteroid (NEA), 2008 TC3 was discovered

by the Catalina Sky Survey on 2008 October 6 at 6:39 UT. The Jet

Propulsion Laboratory (JPL, USA) predicted that 2008 TC3 would

enter the Earth's atmosphere over northern Sudan on 2008 October

7 at 02:46 UT. During its entry in the Earth’s atmosphere, a

fireball was detected by United States Government satellites

sensors and infrasonic emissions by a station in Kenya. 2008 TC3

was the first Earth-colliding object detected before hitting Earth,

which made it a target of high interest. Photometric observations

prior to impact were carried out by M. Kozubal and R. Dantowitz

from Clay Center Observatory (USA). Analysis by A. Harris and

P. Pravec of the Clay Center data revealed that the object was a

“tumbler”, i.e., it was in non-principal axis rotation (NPAR), and

showed two periods being P1= 49 and P2= 97 seconds. (Chesley et

al., 2008).

Unfortunately, the “Descobrindo o Céu” group was unsuccessful

in its attempt to observe this object because of unfavourable

weather conditions. Our analysis is based on CCD images that

were kindly made available by Europeans amateur astronomers

(see Table 1). Unfiltered observations were made nearly

simultaneously by the three groups on 2008 October 6-7 from

21:40 to 00:40 UT. Images were made with exposure times of 2 to

10 seconds and were obtained with a maximum interval of 10

seconds. Bias, dark and flat-field images were applied to calibrate

all the images. A total of 617 images were measured in MPO

Canopus v9.3.1.0 as was the period search using Fourier analysis.

It should be pointed out, that the Fourier analysis algorithm in

Canopus is not designed for tumbling asteroids, which do not have

simple additive periods. Pravec’s analysis used his software that is

capable of working with non-additive periods (see Pravec et al.,

2005).

We found periods of 0.026957 ± 0.000005 h or 97.05 ± 0.02 s and

0.053983 ± 0.000004 h or 194.34 ± 0.02 s (Figure 1). Similar

periods were obtained by M. Kidger using part of the sample

analyzed in this study (Kidger, 2008). The results suggest that the

longer period is simply twice that of the shorter and likely caused

by an ambiguity in the number of rotations over the time the data

were obtained. Our failure to find the true periods found by Pravec

show the importance of using the proper tools for complex

lightcurves. The amplitude of the curve using the shorter period is

0.30 ± 0.03 mag (Figure 2). However, this result should not be

taken at face value due to the dispersion in our data and because

we did not fully analyze the tumbling nature of the object and so

its effect on the lightcurve.

The unfiltered instrumental magnitudes, taken from the images by

P. Beltrame and R. Naves, were transformed to Johnson V

magnitudes using the methodology proposed by Henden (2000).

In this case, we assumed that 2008 TC3 has a B-V color index

equal to 0.80 ± 0.08. This value is based on mean of B-V colors

of a sample of 56 NEAs (Dandy et al. 2003). The B-V colour

index for each comparison star was calculated by applying the

conversion equations between 2MASS J-K colour and the

Johnson-Cousins system (Warner, 2007).

At 21:11 UT (average time), the apparent V magnitude was 16.01

± 0.09 and 14.39 ± 0.04 at 00:21 UT. The second magnitude

matches the one proposed in the ephemeredes from the Minor

Planet Center, with an error of 0.07%. The 16.01 V magnitude of

object at 21:11 UT implies an error of 1.7% when compared with

the MPC ephemeredes. This error difference may be a result of

SNR variation among the analyzed images. The magnitude

estimate at 00:21 UT was used to find the object’s absolute

magnitude (H). Using the H-G magnitude system (Bowell et al.,

1989), we found the reduced magnitude H(α) = 31.17 ± 0.04. We

assumed a mean phase slope parameter and albedo of G = 0.2 ±

0.2 and pV = 0.09 ± 0.07 for low albedo Tholen classes from

Harris (1989). For phase angle α = 12.50, this implies H = 30.79 ±

0.08. This value is consistent with the JPL Small-Body Database

Browser of H = 30.7 ± 0.4. Assuming a spherical shape and using

the expression proposed by Bowell et al. (1989), we estimate D =

3 ± 1 m. This diameter is in the interval between 10-4 m and 10 m

that distinguishes dust and asteroids from meteoroids as defined

by Beech and Steel (1995), and so imply in the reclassification of

2008 TC3 as a meteoroid.

Acknowledgments

A.S. Betzler and A.B. Novaes thanks to the Vitae Foundation,

MCT (Ministry of Science and Technology) and the Institute of

Physics of UFBA (IF-UFBA) for supporting the “Discovering the

Sky” Project. We are also grateful to B. D Warner and two

anonymous reviewers for the detailed revision and many

suggestions, which much improved this work.

Observer Site Telescope Inst.

P. Beltrame C.AS.T

0.35m f/5

Newt.

ST-10XME

R. Naves,

M. Campàs

Montcabrer–

Cabrils

0.3m f/5.5

SCT

ST-8XME +

AO8

G. Muler Nazaret

0.3m f/5.6

SCT

ST-8XME +

AO7

Table 1. Contributing observers.

por cierto, muchas gracias.

para algo tiene que servir tantas noches sin dormir...

[cometas]

Fue una noche realmente emocionante.

[Solrac]

Impresionante!

Si fue muy emocionante para los que nos tuvimos que limitar a seguir los acontecimientos de esa noche por internet, me imagino lo que habrá sido para los que pudieron registrarlo.

Saludos!

[jahensan]

Una noche única, claro que si:

A mi se me nubló pero pude tomar esta foto:

,

Ahora resulta increible ver los pedazos de ese puntito blanco...

Saludos

[gustavo muler]

ahora que lo miro desde esta perspectiva...

pues si, la primera vez que le tiro a algo y lo veo bien de dia, el primer objeto tangible que pasó por la ccd.

si, un lujazo.

saludos, !!!!!!!!!

esta noche, estuvimos en contacto los tres por telefono viendo un poco como iba progresando el evento.

que bueno que haya terminado así.

saludos, gustavo !