SEN: Twin Cepheids Found on the Far Side of the Galaxy

[bystander]

Pulsating stars found in hidden star cluster on far side of the Galaxy
Space Exploration Network | 2015 Jan 14

[i]False colour VVV image taken from the paper, showing the location of the two Cepheids highlighted by the white marks. The image scale given is 30 arcseconds, or 0.11 light years. [b]Image credit: I. Dékány et al. 2014[/b][/i]

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Astronomers from Chile and Canada have recently detected the first pair of a type of pulsating star called Cepheids to be found on the far side of the Milky Way.

It seems that they may be part of a young, open star cluster, making this a potential double-discovery win for the team as neither object has been discovered on the opposite side of the Galactic disc to the Earth before.

By using infrared data from a survey called the Vista Variables in the Via Láctea (VVV), using the VISTA telescope based at Paranal Observatory, Chile, the team created a new observing programme, called the VVV Galactic Cepheid Program (VGCP). Its aim was to discover and characterise distant Cepheids with the aim of mapping the spiral arm structure on the far side of the Milky Way’s disc, behind the central bulge.

As part of their first results from VGCP, the team were able to detect a close pair of classical Cepheids that are almost identical in their observed properties. These "Twin Cepheids" both have the same apparent brightness and colour (temperature), are located at the same distance away from the Sun, and are obscured by the same amount of dust from the central bulge.

From these similarities and subsequent models, it is believed that both stars are the same age at around 48 million years, have a separation of just over 3 light-years, and are located more than 37,000 light-years away. ...

Discovery of a Pair of Classical Cepheids in an Invisible Cluster Beyond the Galactic Bulge - I. Dékány et al

• Astrophysical Journal Letters 799(1) L11 (20 Jan 2015) DOI: 10.1088/2041-8205/799/1/L11
  arXiv.org > astro-ph > arXiv:1412.8658 > 30 Dec 2014

[bystander]

VISTA Stares Right Through the Milky Way
ESO Photo Release | VISTA | 2015 Feb 04

New infrared view of the Trifid Nebula reveals new variable stars far beyond

[imghover=http://www.eso.org/public/archives/imag ... o1504f.jpg]http://www.eso.org/public/archives/imag ... o1504g.jpg[/imghover]Credits: IR (ESO/VVV Consortium/D. Minniti); Visible (ESO/Gábor Tóth)[hr][/hr]

A new image taken with ESO’s VISTA survey telescope reveals the famous Trifid Nebula in a new and ghostly light. By observing in infrared light, astronomers can see right through the dust-filled central parts of the Milky Way and spot many previously hidden objects. In just this tiny part of one of the VISTA surveys, astronomers have discovered two unknown and very distant Cepheid variable stars that lie almost directly behind the Trifid. They are the first such stars found that lie in the central plane of the Milky Way beyond its central bulge.

As one of its major surveys of the southern sky, the VISTA telescope at ESO’s Paranal Observatory in Chile is mapping the central regions of the Milky Way in infrared light to search for new and hidden objects. This VVV survey (standing for VISTA Variables in the Via Lactea) is also returning to the same parts of the sky again and again to spot objects that vary in brightness as time passes.

A tiny fraction of this huge VVV dataset has been used to create this striking new picture of a famous object, the star formation region Messier 20, usually called the Trifid Nebula, because of the ghostly dark lanes that divide it into three parts when seen through a telescope.

The familiar pictures of the Trifid show it in visible light, where it glows brightly in both the pink emission from ionised hydrogen and the blue haze of scattered light from hot young stars. Huge clouds of light-absorbing dust are also prominent. But the view in the VISTA infrared picture is very different. The nebula is just a ghost of its usual visible-light self. The dust clouds are far less prominent and the bright glow from the hydrogen clouds is barely visible at all. The three-part structure is almost invisible. ...

[Ann]

I really like the infrared view of the Trifid, and I totally enjoyed the video that allowed me to compare the appearance of the Trifid in optical and infrared light.

Thanks, bystander!