Starship Asterisk*

[img3="Credit: ESO/Babak Tafreshi (TWAN)"]https://cdn.eso.org/images/screen/potw1623a.jpg[/img3][hr][/hr]

In this picture, the enclosure for ESO’s New Technology Telescope (NTT) has opened its angled doors to reveal a long slice of the southern sky. The sky is freckled by stars, while the moon lights up the inner walls of the NTT dome, casting a shadow over the 3.6-metre telescope. At the top of the telescope we can make out the secondary mirror cell of the telescope, held in a ring structure and supported on struts above the primary mirror.

One of the NTT’s remarkable aspects is that it employs active optics, in which the primary mirror is flexible and its shape is actively adjusted during observations by actuators to preserve the optimal image quality. The position of the secondary mirror is also actively controlled in three directions. This technology, developed by ESO, is nowadays applied to all major modern telescopes, such as the Very Large Telescope at Cerro Paranal and the future European Extremely Large Telescope.

The design of the octagonal enclosure housing the NTT is another technological breakthrough. The telescope dome is relatively small, and is ventilated by a system of flaps that makes air flow smoothly across the mirror, reducing turbulence and leading to sharper images. When the dome is opened, the telescope comes to life and moves across the sky to track astronomical objects.

[img3="Credit: NASA/ESA/Hubble"]http://cdn.spacetelescope.org/archives/ ... w1623a.jpg[/img3][hr][/hr]

The drizzle of stars scattered across this image forms a galaxy known as UGC 4879. UGC 4879 is an irregular dwarf galaxy — as the name suggests, galaxies of this type are a little smaller and messier than their cosmic cousins, lacking the majestic swirl of a spiral or the coherence of an elliptical.

This galaxy is also very isolated. There are about 2.3 million light years between UGC 4879 and its closest neighbour, Leo A, which is about the same distance as that between the Andromeda Galaxy and the Milky Way.

This galaxy’s isolation means that it has not interacted with any surrounding galaxies, making it an ideal laboratory for studying star formation uncomplicated by interactions with other galaxies. Studies of UGC 4879 have revealed a significant amount of star formation in the first 4-billion-years after the Big Bang, followed by a strange nine-billion-year lull in star formation, ended 1-billion-years ago by a more recent reignition. The reason for this behaviour, however, remains mysterious, and the solitary galaxy continues to provide ample study material for astronomers looking to understand the complex mysteries of starbirth throughout the Universe.

[img3="Credit: NASA/ESA/Hubble"]https://www.spacetelescope.org/static/a ... w1624a.jpg[/img3][hr][/hr]

This colourful and star-studded view of the Milky Way galaxy was captured when the NASA/ESA Hubble Space Telescope pointed its cameras towards the constellation of Sagittarius (The Archer). Blue stars can be seen scattered across the frame, set against a distant backdrop of red-hued cosmic companions. This blue litter most likely formed at the same time from the same collapsing molecular cloud.

The colour of a star can reveal many of its secrets. Shades of red indicate a star much cooler than the Sun, so either at the end of its life, or much less massive. These lower-mass stars are called red dwarfs and are thought to be the most common type of star within the Milky Way. Similarly, brilliant blue hues indicate hot, young, or massive stars, many times the mass of the Sun.

A star’s mass decides its fate; more massive stars burn brightly over a short lifespan, and die young after only tens of millions of years. Stars like the Sun typically have more sedentary lifestyles and live longer, burning for approximately ten billion years. Smaller stars, on the other hand, live life in the slow lane and are predicted to exist for trillions of years, well beyond the current age of the Universe.

[img3="Credit: ESO/Schmidt et al."]https://cdn.eso.org/images/screen/potw1624a.jpg[/img3][hr][/hr]

Astronomers hunt for planets orbiting other stars (exoplanets) using a variety of methods. One successful method is direct imaging; this is particularly effective for planets on wide orbits around young stars, because the light from the planet is not overwhelmed by light from the host star and is thus easier to spot.

This image demonstrates this technique. It shows a T-Tauri star named CVSO 30, located approximately 1200 light-years away from Earth in the 25 Orionis group (slightly northwest of Orion’s famous Belt). In 2012, astronomers found that CVSO 30 hosted one exoplanet (CVSO 30b) using a detection method known as transit photometry, where the light from a star observably dips as a planet travels in front of it. Now, astronomers have gone back to look at the system using a number of telescopes. The study combines observations obtained with the ESO’s Very Large Telescope (VLT) in Chile, the W. M. Keck Observatory in Hawaii, and the Calar Alto Observatory facilities in Spain.

Using the data astronomers have imaged what is likely to be a second planet! To produce the image, astronomers exploited the astrometry provided by VLT’s NACO and SINFONI instruments.

This new exoplanet, named CVSO 30c, is the small dot to the upper left of the frame (the large blob is the star itself). While the previously-detected planet, CVSO 30b, orbits very close to the star, whirling around CVSO 30 in just under 11 hours at an orbital distance of 0.008 au, CVSO 30c orbits significantly further out, at a distance of 660 au, taking a staggering 27 000 years to complete a single orbit. (For reference, the planet Mercury orbits the Sun at an average distance of 0.39 au, while Neptune sits at just over 30 au.)

If it is confirmed that CVSO 30c orbits CVSO 30, this would be the first star system to host both a close-in exoplanet detected by the transit method and a far-out exoplanet detected by direct imaging. Astronomers are still exploring how such an exotic system came to form in such a short timeframe, as the star is only 2.5 million years old; it is possible that the two planets interacted at some point in the past, scattering off one another and settling in their current extreme orbits.

• arXiv.org > astro-ph > arXiv:1605.05091 > 17 May 2016

• arXiv.org > astro-ph > arXiv:1605.05315 > 17 May 2016

[img3="Credit: NASA/JPL-Caltech/Space Science Institute"]http://s3.amazonaws.com/ciclops_ir_2016 ... 0042_1.jpg[/img3][hr][/hr]

A bright disruption in Saturn's narrow F ring suggests it may have been disturbed recently. This feature was mostly likely not caused by Pandora (50 miles or 81 kilometers across) which lurks nearby, at lower right. More likely, it was created by the interaction of a small object embedded in the ring itself and material in the core of the ring. Scientists sometimes refer to these features as "jets."

Because these bodies are small and embedded in the F ring itself, they are difficult to spot at the resolution available to NASA's Cassini spacecraft. Instead, their handiwork reveals their presence, and scientists use the Cassini spacecraft to study these stealthy sculptors of the F ring.

This view looks toward the sunlit side of the rings from about 15 above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 8, 2016.

The view was acquired at a distance of approximately 1.4 million miles (2.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 105 degrees. Image scale is 8 miles (13 kilometers) per pixel.

See also: Sculptor and His Work

bystander wrote:The 2016 International Earth & Sky Photo Contest Winners
The World at Night | 2016 Jun 12


Against the Lights Category
[list]
1st: Northern Lights above Lofoten by Alex Conu
[img3=""]http://twanight.org/newTwan/news/6108-03L.jpg[/img3]
2nd: All that Glitters is not Gold by Carlo Zanandrea
[img3=""]http://twanight.org/newTwan/news/6108-05L.jpg[/img3]
3rd: Ancient Ground, Modern Sky by Amirreza Kamkar
[img3=""]http://twanight.org/newTwan/news/6108-07L.jpg[/img3]
Photo Composite: Milky Way Like a Dolphin by Alvin Wu
[img3=""]http://twanight.org/newTwan/news/6108-12L.jpg[/img3]
Photo Sequence: Mountain Liupan Startrails by Sun Guocai
[img3=""]http://twanight.org/newTwan/news/6108-10L.jpg[/img3]
Honorable Mention: [list]
Ocean in the Sky by Sergio Montufar
[img3=""]http://twanight.org/newTwan/news/6108-15.jpg[/img3]
The Forgotten Giant by Jean-Luc Dauvergne
[img3=""]http://twanight.org/newTwan/news/6108-16.jpg[/img3]
[/list][/list][/b]
Beauty of the Night Sky Category
[list]
1st: The Tail of Aurora by Stephanie Ye
[img3=""]http://twanight.org/newTwan/news/6108-04L.jpg[/img3]
2nd: The Photographer by Nicholas Roemmelt
[img3=""]http://twanight.org/newTwan/news/6108-06L.jpg[/img3]
3rd: Sacrament of Unification with Nature by Boris Dmitriev
[img3=""]http://twanight.org/newTwan/news/6108-08L.jpg[/img3]
Photo Composite: Viking Lights by Adam Woodworth
[img3=""]http://twanight.org/newTwan/news/6108-11L.jpg[/img3]
Photo Sequence: Total Solar Eclipse from Svalbard by Thanakrit Santikunaporn
[img3=""]http://twanight.org/newTwan/news/6108-09L.jpg[/img3]
Honorable Mention: [list]
Emerald Crown by Tommy Eliassen
[img3=""]http://twanight.org/newTwan/news/6108-13.jpg[/img3]
Baobab Night by Taha Ghouchkanlu
[img3=""]http://twanight.org/newTwan/news/6108-14.jpg[/img3]
[/list][/list][/b]