Mike Kretlow

Instituto De Astrofisica De Andalucia · Solar System

Within our program of physical characterization of trans-Neptunian objects and centaurs, we predicted a stellar occultation by the centaur (54598) Bienor to occur on January 11, 2019, with good observability potential. We obtained high accuracy astrometric data to refine the prediction, resulting in a shadow path favorable for the Iberian Peninsula...

Context. Outer main belt asteroid (223) Rosa is a possible flyby target of opportunity for the European Space Agency (ESA) JUpiter ICy moons Explorer (JUICE) mission when it passes the asteroid belt on the way to Jupiter. The very low albedo and the featureless red spectra indicate a P-type asteroid in the Tholen taxonomy, though the yet known bulk...

Outer main belt asteroid (223) Rosa is a possible flyby target of opportunity for ESA's (European Space Agency) JUpiter ICy moons Explorer (JUICE) mission when passing the asteroid belt on the way to Jupiter. The very low albedo and the featureless red spectra indicate a P-type asteroid in the Tholen taxonomy, though the yet known bulk density did...

Context. A stellar occultation by Neptune’s main satellite, Triton, was observed on 5 October 2017 from Europe, North Africa, and the USA. We derived 90 light curves from this event, 42 of which yielded a central flash detection. Aims. We aimed at constraining Triton’s atmospheric structure and the seasonal variations of its atmospheric pressure si...

A stellar occultation by Neptune's main satellite, Triton, was observed on 5 October 2017 from Europe, North Africa, and the USA. We derived 90 light curves from this event, 42 of which yielded a central flash detection. We aimed at constraining Triton's atmospheric structure and the seasonal variations of its atmospheric pressure since the Voyager...

Context. The Centaur (10199) Chariklo has the first ring system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow sizes and shapes to be determined with kilometre accuracy, and provide the characteristics of the occulting object and its vicinity. Aims. Using stellar occultations ob...

The Centaur (10199) Chariklo has the first rings system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow the determination of sizes and shapes with kilometre accuracy and obtain characteristics of the occulting object and its vicinity. Using stellar occultations observed between 2...

The stellar occultation method is a particularly powerful tool for probing the nature of distant solar system objects. Here we report a single observation of a close appulse of comet 29P/Schwassmann-Wachmann 1 to a 14 mag star that showed no significant deviation in the recorded light curve on a 2.25 s time resolution (corresponding to 27 km in pro...

Python is one of the most popular programming languages and is a great tool for scientific computing. Thus, it is well suited for almost any kind of astronomical applications. In the last few years many large packages for astronomical and astrophysical work have been developed or have matured, in many cases actively maintained by professional inst...

Size (volume), mass, density, and macro porosity are important physical properties for our understanding of the internal structure and morphology of asteroids. Up to now, no machine-readable, easy to use and open-access data collection was available. Purpose of SiMDA (Size, Mass and Density of Asteroids) is not only to serve as an up-to-date and co...

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto an...

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto an...

Context. Pluto's tenuous nitrogen (N2) atmosphere undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has been recently (July 2015) observed by the New Horizons spacecraft. Goals are (i) construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) constrain the structure of the...

We report here the observation of a stellar occultation by Kuiper Belt object (50000) Quaoar. We recorded a positive occultation of a 12.7 G-mag star designated as Gaia DR2 source ID 4145444851530756224 on 2018 September 2 at two stations; one fixed station in Namibia (ATOM, H.E.S.S. site), using a 0.75 m telescope and one mobile station placed abo...

Stellar occultations by comets are generally problematic. The coma is usually too tenuous to be detected by the attenuation effect on stars unless the comet is a very active one and the nucleus passes within a few hundred kilometers of the star as projected on the sky frame. Where an occultation by the solid body of the nucleus occurs, the shadow t...

On 2017 October 05 Triton, the largest satellite of Neptune, will occult a 12.7 V-mag star, visible from the US east coast, Northern Africa and Europe. This will be the first opportunity to monitor Triton's current atmospheric state and possible changes since the 1990s.

A successful occultation observation of a 14 Gmag star by the Centaur (10199) Chariklo on 2017 June 22 using the IOTA/ES 50-cm "M2" portable Alt-Az telescope in Namibia is reported.

A successful occultation observation of a 14 Gmag star by the Centaur (10199) Chariklo on 2017 Apr 09 using the IOTA/ES 50-cm "M2" portable Alt-Az telescope in Namibia is reported.

CCD photometric observations of the main-belt asteroid (222317) 2000 TE1 were made on 2014 December 23 and 25. From the lightcurve, we obtained a possible synodic period of 11.83 ± 0.04 h with an amplitude of 0.63 mag.

In the past years lightcurve observations were successfully combined with other data like occultation timings. This has added a new, important application to asteroidal occultation work.

CCD photometric observations of main-belt asteroid 30 Urania were made over six nights in 2012 January. The lightcurve shows a synodic period of 13.692 ± 0.001 h with an amplitude of 0.19 mag.

CCD photometric observations of Amor-type asteroid (361071) 2006 AO4 were made on 2013 September 23. From the lightcurve we obtained a synodic period of 4.09 ± 0.17 h with an amplitude of 0.13 mag.

By applying the astrometric mass determination technique, a value of M = 2.4 ± 0.4 × 10–12 solar masses has been obtained for the binary asteroid 121 Hermione from the motion of 278 Paulina and 5750 Kandatai.

By applying the astrometric mass determination technique, a value of M = (6.2 ± 2.7) 10^-13 solar masses has been obtained for asteroid 476 Hedwig.

Context. Pluto has five known satellites with diameters ranging from ~1200 km down to ~40 km, a possible outcome of a collisional origin. Smaller objects probably exist and may maintain tenuous rings, thus representing hazards during the New Horizons flyby of July 2015. Aims: The goal is to provide an upper limit for the numbers of unseen small bod...

Photometric observations of NEO (24445) 2000 PM8 were made over three nights in September 2013. A synodic period P = (6.81 ± 0.03) h was derived from these data.

On September 8, 2001 around 2 h UT, the largest uranian moon, Titania, occulted Hipparcos star 106829 (alias SAO 164538, a V=7.2, K0 III star). This was the first-ever observed occultation by this satellite, a rare event as Titania subtends only 0.11 arcsec on the sky. The star's unusual brightness allowed many observers, both amateurs or professio...

On September 8, 2001 around 2 h UT, the largest uranian moon, Titania, occulted Hipparcos star 106829 (alias SAO 164538, a V = 7.2, KO III star). This was the first-ever observed occultation by this satellite. a rare event as Titania subtends only 0.11 arcsec on the sky. The star's unusual brightness allowed many observers, both amateurs or profess...

1] We report the observation of two stellar occultations by Titan on 14 November 2003, using stations in the Indian Ocean, southern Africa, Spain, and northern and southern Americas. These occultations probed altitudes between $550 and 250 km ($1 to 250 mbar) in Titan's upper stratosphere. The light curves reveal a sharp inversion layer near 515 ±...

The mass of (29) Amphitrite, an S-class asteroid in the main belt, was determined from its gravitational perturbations on the motion of (987) Wallia and (6904) McGill. For the mass of (29) Amphitrite a value of (5.6 ± 1.1) × 10 −12 M was obtained from the analysed observations of (987) Wallia and (5.9 ± 0.6) × 10 −12 M from the observations of (690...

After the discovery and study of Pluto's tenuous atmosphere in 1985 and 1988 with stellar occultations 14 years were necessary before two other occultations by the planet could be observed on 20 July 2002 and 21 August 2002 from Northern Chile with a portable telescope and from CFHT in Hawaii respectively. These occultations reveal drastric changes...

Pluto’s tenuous nitrogen atmosphere was detected by stellar occultations in 1985 and 1988. This atmosphere is poorly known, however, due to the rarity of these events. We report here the first Pluto occultations observed since 1988, on 20 July and 21 August 2002. Our analysis reveals drastic changes undergone by the atmosphere since 1988, namely a...

On November 14, 2003, Titan occulted two bright Tycho stars (V= 8.4 and V= 10.3). The first event was observed in the Indian Ocean and southern Africa, while the second one was followed from western Europe, northern and central Americas. Data were gathered by both professional and amateur astronomers, using fixed and portable telescopes at waveleng...

Pluto's tenuous nitrogen atmosphere was first detected by the imprint left on the light curve of a star that was occulted by the planet in 1985 (ref. 1), and studied more extensively during a second occultation event in 1988 (refs 2-6). These events are, however, quite rare and Pluto's atmosphere remains poorly understood, as in particular the plan...

The star P126 was a candidate for occultation by Pluto on July 20, 2002, see the list of McDonald and Elliot, AJ 119:1999-2007, April 2000, and AJ 120:1599-1602, September 2000. Astrometric measurements from various sources, including Pic du Midi Observatory, predicted that the shadow path would sweep across the upper half of South America, with si...

Ergebnisse über nichtgravitative Kräfte bei Kometen

Contents: 1. Geschichte der Kometenforschung (H.-L. Neumann). 2. Kometenbeobachtung mit Amateurmitteln (A. Kammerer). 3. Die visuelle Kometenbeobachtung (S. Korth, O. Guthier). 4. Die wichtigsten Sternkataloge für Kometenbeobachter (A. Kammerer, M. Möller). 5. Die Auswertung visueller Kometenbeobachtungen (A. Kammerer). 6. Die photographische Komet...

An introduction is presented to observations of star occultations by minor planets and comets. Some basic observing techniques are described.

Astrometry updates of minor planets and target stars are necessary to compute last minute predictions of those events. A coordinated network of both amateur and professional observers could do this job.

The author gives an overview of the scientific value of astrometric observations of minor planets and comets by amateurs and shows some proposals. An introduction into basic photographic astrometry is also presented.

The author presents the history of the comet P/Swift-Tuttle.

The author presents an introduction into determing astrometric positions by using only two reference stars. The accuracy of this method reaches 2".