Archive for Orbits

Four New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , on November 9, 2024 by telescoper

Once again it’s time for a quick update of activity at the Open Journal of Astrophysics. Since the last update a week ago we have published  four papers, which takes the count in Volume 7 (2024) up to 102 and the total published altogether by OJAp up to 217.   This means not only that we have reached a century for the year but also that so far in 2024 we have published more than double the number of papers that we published in all of 2023. I blogged about the significance of the figure 217 here.

In chronological order, the four papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.

First one up is “A generative model for Gaia astrometric orbit catalogs: selection functions for binary stars, giant planets, and compact object companions” by Kareem El-Badry (Caltech, USA), Casey Lam (Carnegie Observatories), Berry Holl & Jean-Louis Halbwachs (U. Geneva), Hans-Walter Rix (MPA Heidelberg, Germany), Tsevi Mazeh (Tel Aviv, Israel) and Sahar Shahaf (Weizmann Institute of Science, Israel). This one is in the folder Solar and Stellar Astrophysics. The paper presents a forward method for estimating the selection function (i.e. the probability of a system with a given set of parameters being included in a catalog). It was published on November 4th 2024.

Here is a screen grab of the overlay, which includes the abstract:

 

You can find the officially accepted version of the paper on the arXiv here.

The second paper to announce, published on 5th November 2024. is “Primordial magnetogenesis in a bouncing model with dark energy” by Marcus V. Bomfim (Rio de Janeiro, Brazil), Emmanuel Frion (Western U. Canada), Nelson Pinto-Neto (Espírito Santo, Brazil), and Sandro D. P. Vitenti (Paraná, Brazil). This paper, in the section on Cosmology and NonGalactic Astrophysics, presents a discussion of the possible generation of magnetic fields on cosmological scales by in a model involving a scalar field coupled to electromagnetism

You can see the overlay here:

 

 

 

The accepted version of this paper can be found on the arXiv here.

The third paper, published on 6th November 2024 in the folder marked Astrophysics of Galaxies, is called  “Evidence for large scale compressible turbulence in the ISM of CSWA13, a star-Forming Lensed Galaxy at z = 1.87 with outflowing wind” by Itzhak Goldman (Tel Aviv, Israel). It presents a statistical analysis of the spatial distribution and kinematics of nebular gas with discussion of the nature of the turbulence present.

Here is the overlay

 

 

The final version accepted on arXiv is here.

Last in this batch is “Star formation in the high-extinction Planck cold clump PGCC G120.69+2.66” by Anlaug Amanda Djupvik (Aarhus, Denmark), João L. Yun (Lisbon, Portugal), and Fernando Comerón (ESO, Garching, Germany). It was published on 7th November 2024 in the folder marked Astrophysics of Galaxies. The paper uses imaging and spectroscopy  information to identify sites of star formation in a molecular cloud. This is the overlay:

You can find the official accepted version on the arXiv here.

That’s all for now. I will post another update in a week.

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The Problem of the Disintegrating Asteroid

Posted in Cute Problems, The Universe and Stuff with tags , , on September 30, 2019 by telescoper

I thought you might enjoy this entry in the Cute Problems folder.

An asteroid is moving on a circular orbit around the Sun with an orbital radius of 3AU when it spontaneously splits into two fragments, which initially move apart along the direction of the original orbit. One fragment has a speed which is a fraction 0.65 of the original speed, the other has a speed of 1.35 times the original speed. The original orbit (solid line) is shown above, along with the two new orbits (dashed and dotted).

  1. Which orbit does the fast fragment follow, and which the slow fragment?
  2.  Calculate the original orbital speed in AU/year.
  3. Calculate the angular momentum per unit mass, h, of the original asteroid and of each of the two fragments in units of AU2 per year. [HINT: Show that in these units, for a general orbit of eccentricity e and semi-major axis a, h2=4π2 a (1-e2).]
  4.  Calculate the eccentricities of the orbits of the two fragments.
  5.  Calculate the orbital periods of the two fragments in years.

Answers please through the Comments box. First complete set of answers wins a trip to the Moon on gossamer wings.

 

 

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