2024 May 2

M100: A Grand Design Spiral Galaxy
Image Credit & Copyright: Drew Evans

Majestic on a truly cosmic scale, M100 is appropriately known as a grand design spiral galaxy. The large galaxy of over 100 billion stars has well-defined spiral arms, similar to our own Milky Way. One of the brightest members of the Virgo Cluster of galaxies, M100, also known as NGC 4321 is 56 million light-years distant toward the well-groomed constellation Coma Berenices. In this telescopic image, the face-on grand design spiral shares a nearly 1 degree wide field-of-view with slightly less conspicuous edge-on spiral NGC 4312 (at upper right). The 21 hour long equivalent exposure from a dark sky site near Flagstaff, Arizona, planet Earth, reveals M100's bright blue star clusters and intricate winding dust lanes which are hallmarks of this class of galaxies. Measurements of variable stars in M100 have played an important role in determining the size and age of the Universe.

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2024 May 4

3 ATs
Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory, TWAN)

Despite their resemblance to R2D2, these three are not the droids you're looking for. Instead, the enclosures house 1.8 meter Auxiliary Telescopes (ATs) at Paranal Observatory in the Atacama Desert region of Chile. The ATs are designed to be used for interferometry, a technique for achieving extremely high resolution observations, in concert with the observatory's 8 meter Very Large Telescope units. A total of four ATs are operational, each fitted with a transporter that moves the telescope along a track allowing different arrays with the large unit telescopes. To work as an interferometer, the light from each telescope is brought to a common focal point by a system of mirrors in underground tunnels. Above these three ATs, the Large and Small Magellanic Clouds are the far, far away satellite galaxies of our own Milky Way. In the clear and otherwise dark southern skies, planet Earth's greenish atmospheric airglow stretches faintly along the horizon.

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The relative speed of rotation of the planets of the solar system around their axis.

A Mercurian day is equal to 58 Earth days, that is, 2/3 of a Mercurian year

Venus rotates in the direction opposite to the direction of rotation of most planets. One revolution around its axis in duration is equal to 243 Earth days.

Jupiter rotates around its axis faster than any other planet in the solar system - 9 h 55 min. Because of its rapid rotation, Jupiter's equatorial radius is 6.49% larger than its polar radius.

The duration of Saturn's revolution around its axis is 10 hours, 33 minutes. Saturn is the only planet that has an axial rotation rate at the equator greater than its orbital rotation rate (9.87 km/s and 9.69 km/s).

Because Neptune has no solid surface, its equatorial zone rotates with a period of approximately 18 hours, while its polar regions rotate in 12 hours. Of all the planets in the solar system, this type of rotation is most pronounced for Neptune. This results in a strong wind shift.

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