Category Archives: Astronomy

The latest ESO (European Southern Observatory) report:

The small smattering of bright blue stars in the upper left of this vast new 615 megapixel ESO image is the perfect cosmic laboratory in which to study the life and death of stars. Known as Messier 18 this star cluster contains stars that formed together from the same massive cloud of gas and dust. This image, which also features red clouds of glowing hydrogen and dark filaments of dust, was captured by the VLT Survey Telescope (VST) located at ESO’s Paranal Observatory in Chile.

This sequence takes the viewer from a wide view of the Milky Way deep into the central regions, where many bright star forming regions and star clusters can be seen. The final view is a close-up of the sky around the bright star cluster Messier 18 taken with the VLT Survey Telescope at ESO’s Paranal Observatory. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org). Music: Johan B. Monell (www.johanmonell.com)

Messier 18 was discovered and catalogued in 1764 by Charles Messier — for whom the Messier Objects are named — during his search for comet-like objects [1]. It lies within the Milky Way, approximately 4600 light-years away in the constellation of Sagittarius, and consists of many sibling stars loosely bound together in what is known as an open cluster.

There are over 1000 known open star clusters within the Milky Way, with a wide range of properties, such as size and age, that provide astronomers with clues to how stars form, evolve and die. The main appeal of these clusters is that all of their stars are born together out of the same material.

eso1628c[1] — The small smattering of bright stars at the centre of this wide-field view is Messier 18, an open star cluster containing stars that formed together from the same massive cloud of gas and dust. This picture, which also shows part of the bright Omega Nebula (Messier 17) at the top, was created from images forming part of the Digitized Sky Survey 2. Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

In Messier 18 the blue and white colours of the stellar population indicate that the cluster’s stars are very young, probably only around 30 million years old. Being siblings means that any differences between the stars will only be due to their masses, and not their distance from Earth or the composition of the material they formed from. This makes clusters very useful in refining theories of star formation and evolution.

Astronomers now know that most stars do form in groups, forged from the same cloud of gas that collapsed in on itself due to the attractive force of gravity. The cloud of leftover gas and dust — or molecular cloud — that envelops the new stars is often blown away by their strong stellar winds, weakening the gravitational shackles that bind them. Over time, loosely bound stellar siblings like those pictured here will often go their separate ways as interactions with other neighbouring stars or massive gas clouds nudge, or pull, the stars apart. Our own star, the Sun, was most likely once part of a cluster very much like Messier 18 until its companions were gradually distributed across the Milky Way.

This video sequence takes a close look at a huge 615 megapixel image captured by the OmegaCAM camera attached to the VLT Survey Telescope (VST) located at ESO’s Paranal Observatory in Chile. It shows the sky around the star cluster Messier 18. This small smattering of bright blue stars is the perfect cosmic laboratory in which to study the life and death of stars that formed together from the same massive cloud of gas and dust. Credit: ESO. Music: Johan B. Monell (www.johanmonell.com)

The dark lanes that snake through this image are murky filaments of cosmic dust, blocking out the light from distant stars. The contrasting faint reddish clouds that seem to weave between the stars are composed of ionised hydrogen gas. The gas glows because young, extremely hot stars like these are emitting intense ultraviolet light which strips the surrounding gas of its electrons and causes it to emit the faint glow seen in this image. Given the right conditions, this material could one day collapse in on itself and provide the Milky Way with yet another brood of stars — a star formation process that may continue indefinitely (eso1535).

This mammoth 30 577 x 20 108 pixel image was captured using the OmegaCAM camera, which is attached to the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile.

Notes

[1] Messier 18 is also listed in the New General Catalogue as NGC 6613

This chart shows the rich constellation of Sagittarius. Among the many star clusters in this part of the Milky Way lies Messier 18, a bright grouping of stars not far from the Omega Nebula (Messier 17). This picture plots most of the the stars visible on a dark clear night with the naked eye.

Astronomy, Meteors

More on the Perseids

August 6, 2016 TopSpacer

I mentioned the Perseid meteor showers in a recent posting. Here is an infographic from Universe2go about the upcoming peak shower period over August 11th and 12th:

Astronomy, Exoplanets

Update on Tabby’s Star, i.e. the “Alien Megastructure Star”

August 4, 2016 TopSpacer 1 Comment

A star displaying peculiar light patterns was first noticed in Kepler space telescope data by a group of citizen scientists working in the Planet Hunters program. Their work convinced astronomer Tabetha Boyajian to investigate star KIC 8462852, which is also known as Tabby’s Star or the WTF star (‘Where’s the Flux?’), in more detail. The investigation by her group found the star to be quite an oddity. Boyajian is interviewed about it in this article: How Astronomers Plan to Solve the Mystery of the “Alien Megastructure Star” – Out There/Discover Magazine

Tabby’s Star is so unusual that a few scientists, including Boyajian’s colleague Jason Wright, raised the possibility that its flickering is not natural but is due to the presence of an enormous artificial construct. That speculation quickly lent KIC 8462852 another nickname, the “alien megastructure star,” and prompted a flood of breathless news stories; it even got a shout out on Saturday Night Live. Boyajian’s subsequent TED lecture drew even more attention to her star.

To obtain telescope time to study the star continuously for at least a year, a successful Kickstarter campaign raised $107,421: The most mysterious star in the Galaxy by Tabetha Boyajian — Kickstarter.

From the interview:

The plan is to observe the star through a full calendar year at the [private] Las Cumbres Observatory Global Telescope Network (LCOGT). We have the funds to cover that, and a little bit more. We’re observing now, running off time LCOGT has gifted us, 200 hours there. At the end of the summer, when the Kickstarter funds get transferred, we’ll be able to set up the process through August and probably through December of 2017.

We want to see the star’s brightness dip again—it’s as simple as that. When it dips, how long the dips are, if there are many dips, all of the stuff relevant to any theory that’s on the table. Also, we’ll be able to get more detailed observations of whatever stuff is passing in front of the star, because we have a system to notify us when it’s not at its normal brightness. LCOGT is set up so we can get a spectrum as soon as that trigger happens, and also more intense observations.

These two videos from the Kickstarter campaign describe the star and their research plan:

Asteroids & Comets, Astronomy, Meteors

Perseid meteor shower peak approaching

August 2, 2016 TopSpacer

The annual Perseid meteor showers are underway. Here is a guide for observing the shooting stars: Viewing the 2016 Perseids – American Meteor Society

The Perseids are active from July 13th through August 26th. Maximum activity is predicted to occur on the morning of August 12th, when rates in excess of 1 per minute may be seen from dark sky sites. On the morning of maximum the waxing gibbous moon will set between midnight and 0100 local daylight time as seen from mid-northern latitudes. This will free up the prime observing hours from interfering moonlight.

A meteor shower happens when the Earth’s orbit crosses the trail of dust particles left by a comet. The Perseids are produced by the trail of Comet Swift-Tuttle as seen in this image:

Although the dust particles are tiny, they are going so fast relative to the earth they can still produce a bright meteor when crashing through the atoms in the upper atmosphere.

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