New Laser Vision Helps Telescope Probe Distant Star Cluster

[Judi Lynn]

New Laser Vision Helps Telescope Probe Distant Star Cluster
by Katia Moskvitch
Date: 14 May 2013 Time: 05:40 PM ET


A powerful new ultraviolet laser that fires into the night sky is helping scientists take their most detailed look yet at a distant star cluster.

A team of astronomers at the Southern Observatory for Astrophysical Research (SOAR) and the Cerro Tololo Inter-American Observatory (CTIO) in Cerro Pachon in Chile used an instrument called SOAR Adaptive Module, or simply SAM, to peer deep inside the crowded NGC 6496 cluster to understand how its stars evolved.

The researchers measured the color and brightness of over 7,000 stars in NGC 6496, and determined that the star cluster is 10.5 billion years old and 32,600 light years away from Earth — the most exact measurement yet of the star cluster's key parameters. [Starry Night: Take Our Star Quiz]

The study also suggests that NGC 6496’s stars have a much higher proportion of elements heavier than hydrogen and helium than most clusters of its kind. The research will be detailed in an upcoming edition of the Astronomical Journal.

Star clusters across the universe come in two types: globular clusters, which are home to hundreds of thousands of gravitationally bound and very ancient stars, many of them nearly 10 billion years old; and open star clusters, which are normally very young and contain only a few hundred stars.

More:
http://www.space.com/21148-laser-telescope-tech-star-cluster.html

[longship]

1. Here's NGC 6496.

It has been classified as a globular cluster, but it doesn't look very much like one to me. However, its other characteristics are similar to globulars. It's old. It is part of our local galaxy, but outside of the spiral disk.

For comparison, this is Messier 13, often called the Hercules Cluster, the largest globular cluster in the northern skies.

I've seen this through my telescopes many times. It is truly beautiful. Lots of sparkly points of light, like a plate of diamonds.

[Judi Lynn]

2. Messier 13 is unbelievable! Thanks for the image. n/t

[eppur_se_muova]

3. Creates an "artificial star", used for measuring, then compensating for, atmospheric turbulence.

The article is a little short on details, but apparently UV wavelengths provide more info about the atmosphere.

[Canuckistanian]

4. Ah, thanks

I didn't understand where the laser came in from the OP.

[Judi Lynn]

5. Thank you. n/t

[Ptah]

6. The laser is used as a reference to change the shape of the telescope primary mirror.

SAM is a type of a Laser Guide Star (LSG) – a powerful laser that creates an artificial
star in the night sky. It is used as a reference star to help astronomers get a better
image of the celestial object they wish to observe.

Most skywatchers are likely used to seeing stars twinkle. That twinkling appears because
of the turbulence of the Earth's atmosphere. The atmospheric interference can make the
image of a distant celestial object eyed with a ground-based telescope blurry. This fuzziness
is especially unwelcome when looking at star clusters, where stars are close together and
several stars may appear as one big one.

To sharpen the images, astronomers have to correct for atmospheric turbulence. To do so,
they need to measure the blurring of a bright reference star in the vicinity of the object
being observed. Telescopes with a so-called deformable mirror are then adjusted to cancel
out the atmospheric distortion. This is called "adaptive optics," and makes it possible to
achieve an image quality that is similar to that of telescopes in space.

But natural stars are not always available to act as a reference. According to astronomers
only about 1 percent of stars are bright enough to be used for adaptive optics.
So in the vast majority of cases, they need to create a star from scratch — by using lasers.

However, the wavelength of the laser has to be close to the wavelength observed by
the telescope. On some major telescopes, such as the Very Large Telescope (VLT) at
Paranal Observatory in Chile, astronomers use a powerful near-infrared laser to create
guide stars at an altitude of about 90km, which allows them to make observations
in the infrared range.