Day: March 10, 2021

Review By Jerry Hillburn

cepheids

In March of 2021 I reached out to the Cepheid Observatory team (V.K.Agnihotri, B. Kumar, S. Mahawar, K.Vora) requesting an imaging run on asteroid Apophis. I was impressed by their effort to obtain that data, which I will use in teaching a class on Asteroid studies.

The follow on lightcurve study they performed on the data is quite interesting and is indicative of the scientific rigor of their work

(see https://posts.3cepheids.co.in/wp/photometry/apophis-photometric-curve/).

Asteroid research is conducted by a small community of highly dedicated astronomers. I for one greatly appreciate the opportunity to work together with my fellow researchers on the other side of our pale blue dot. I am only just beginning my collaboration with this team of bright thinkers, and look forward to working with them in the future! Please accept my thanks for your assistance!

Jerry Hilburn (San Diego California, USA) – He is working at catfish Software Inc. and also an amateur astronomer. He is contributor in many papers on Astrometric and Photometric Measurements of double stars. For more visit: http://jdso.org/

Jerry Hilburn

Apophis Photometric Curve

cepheids1 Comment

Asteroid photometry is nothing but the study of fraction of solar radiation, which is reflected by the surface of small body. Here we examined the photometry of Apophis, a big/elongate metal rich asteroid passing by near to earth.

If we assume that asteroid Apophis is metal rich, it could reflect good part of solar radiation at V band as well as R Band. The tendency of photon reflection decrease from V (short wavelengths) to R (longer wavelengths) band. Here we took the assumption that sun is G2V type star, so most of photons are towards yellow + red end and hence small body is reflecting more photons at R band. These are just assumption to make task interesting. Anyway!

The second point is that if asteroid is perfect spherical body, spinning around random axis will reflect same flux towards telescope, but case will be different if small body have irregular structure. In this case the flux reflected will be proportional to the cosine of area seen by telescope and depend on angle between sun/asteroid/earth.

In our study, we dragged the R band flux w.r.t time. The FITS generated and examined using PriSMv10 batch photometry using UCAC4 catalog. The results are shown below.

Apophis Photometric Curve

We should not forget that Apophis photometric curve was measured w.r.t standard stars and as soon as sun and asteroid changes the position in sky, the incident solar flux does not remain constant. It can be seen that the magnitude at the end of observation goes too high.

Instrument:
Catalog: UCAC4
Bessell (B): +*.*, Bessell (V): +*.*
Bessell (R): +15.2, Bessell (I): +*.*
CCD: ATIK-383L+
FILTERS: R
TELESCOPE: C11, 1623.0mm
PRiSMv10, Astrometrica
Site:
ORIGIN: Cepheid Observatory, India, Vorion Scientific, India
SITELAT: +24:55:00:00
SITELONG:+75:33:58:99
Observers:
V.K.Agnihotri, B. Kumar, S. Mahawar, K.Vora
Remark:
Sky Clear.
End