Two Successive Lunar Impact Flashes: First lunar impact detection from Turkey

Abstract

A number of attempts have been done to detect of lunar impact flash observations by various researchers in last 20 years. One of the systematically research of lunar impact flash observations has been done at İSTEK Belde Observatory since 2017. We report the very first results of two first lunar impact flashes detected from Turkey.

Introduction

Interplanetary space is full of meteoroids, cometary fragments and debris. Occasionaly these objects impact to the surface of the Moon at high velocities. During these events the kinetic energy of the impactor is converted to thermal energy and give out an optical signature detectable with small instruments. Impact flashes are rapid events that in most cases escape attantion due to low amount of signal. Monitoring the night side of the Moon increases capturing an impact flash due to higher contrast. For this reason impact observations are carried out between 5-10 and 20-25 ages of the Moon. Impact events are beneficial providing information on impact energy, impactor mass,  impactor source, temperature of the event [1,2,3,4,5,6]. We present the first report of two impact flashes on December 12, 2017 from Turkey.

Observation and method

ISTEK Belde Observatory (IBO) is located on the Asian shore of the historic Bosphorus waterway at 41^o 01' 48'' N latitude and 29^o 02' 32'' E longitude at an altitude of 150m. The observatory houses a Meade LX600 16'' Schmidt-Cassegrain f/8 telescope as the primary instrument. By using f3.3 focal reducer and Celestron Skyris 274M (1600×1200 px) monochrome camera, the telescope provides 24x30 arcminute field of view. The camera is operated at 15 fps. The time signal is acquired by network synchronisation. On 2017 December 12th a number of consecutive 10 minute observations each providing 9000 frames were inspected by LunarScan [7] and ZEPAZO software. Two impacts were detected and the signal is converted into visual magnitudes using MaximDL aperture photometry routine. For magnitude calculation three reference stars HD111662, HD111663 and HD111692 with known V magnitudes are used. These stars were within 1/4° from the impact sites and they were imaged in close succession with same air mass and exposure time. The impact flashes are detected at 82^o.8 E, 8^o.3 N (Flash 1) and 33^o.7E , 16^o.3N (Flash 2) selenographic coordinates. The photometric data are provided in Table 1 and location of flashes on the Moon are shown in Figure 1.

 

Figure1: Flash 1- 82^o.8 E, 8^o.3 N and  Flash 2 - 33^o.7E , 16^o.3N Selenographic coordinates.

 

Table 1: Information of lunar impact flashes.

	Flash 1	Flash 2
Time	04:19:30.866	04:20:04.400
Duration	0.533(s)	0.466(s)
Peak Magnitude	7.98	7.48
Radiated Energy (J)	1,96x106(J)	2.33x106(J)

 

Analysis and results

Magnitudes of the flashes are calculated using Pogson formula m_f =m_s+2,5log(f_s/f_f), where m_f, m_s are the magnitudes of the flash and the reference star respectively, f_s and f_f are the observed fluxes of the flash and the reference star. The peak magnitudes of the flashes are 7.98 and 7.48 for Flash 1 and Flash 2, respectively. The radiated power P, in watts m^-2, of an impact flash can be calculated using P=κ x 10^-M/2.5Δλ , where κ is the flux density in W m^-2 µm^-1for a magnitude 0 source (κ=3,75x10^-8) [8], M is the aparent magnitude of the flash and Δλ is filter passband (Δλ=500nm), in µm. The observed energy E_d is calculated by integrating power equation with respect to time. The radiated energy which emitted as light on the lunar surface E_r, can be estimate by means of the relation  E_r=E_dπƒR² where R is the Earth-Moon distance (R=386605km), in m, when the flash occurs, f is a factor discribes the anisotropy degree of the light emission process (f=2 for the lunar surface and f=4 for the high altitude on the lunar soil)[9].  We conclude the observed events released energy  1,96x10⁶ J and 2.33x10⁶ J for Flash 1 and Flash2 respectively. These flashes are the first of their kind observed from Turkey; these event provided valuable insight on performance of the observatory instruments and reduction software. 

References

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